Browse Topic: Continuously variable transmissions

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Minimum Weight Design of an Electronic Continuously Variable Transmission for Rotorcraft ApplicationsF-0081-2025-02905/20/2025
This paper, explores the design and sizing of a planetary gear-based electronic continuously variable transmission (ECVT) for implementation of a parallel gas-electric hybrid helicopter propulsion system. The ECVT consists of a differential planetary gear transmission (PGT) and an electric motor/generator (MG) unit. The ECVT enables power-flow between engine, motor and helicopter main rotor. The parallel arrangement enables the main rotor speed to varied continuously based on the MG speed while the engine speed can remain constant. The performance benefits enabled by the main rotor speed variation capability are offset by the added weight penalties introduced by the ECVT system. By considering factors such a as gear tooth bending and contact stress, bearing loads, required motor torque, planetary gear kinematics and pitch-line velocity constraints, this paper conducts a minimum mass design study for several PGT / ECVT arrangements. Here, three different single stage PGT/ECVT arrangements are compared along with an improved two stage ECVT. The three single stage ECVT configurations can be summarized as; I) Sun-Engine / Carrier-Motor / Ring-Out, II) Sun-Engine / Ring-Motor / Carrier-Out, and III) Carrier-Engine / Sun-Motor / Ring-Out. Of these three types, it was found that type III was significantly lighter in weight compared with types I and II since type III would have the highest relative motor speed. When sized for a 3000 Hp engine-side power input at 6000 rpm, the minimum mass design for type III was on the order of 100 lbs compared to 400 lbs and 700 lbs respectively for types I and II. Despite the seemingly obvious advantage of design type III, it's drawback is that it is effectively a speed increasing stage with respect to the engine. To address this, a two-stage ECVT with compound planetary arrangement of Type III and II was designed which achieved an overall minimum weight of 219 lbs at the 3000 Hp level while providing 1:0.351 gear reduction form engine to output. The analysis tools developed and sizing results flowing from this study will provide a baseline for evaluating performance benefits and weight penalties introduced by parallel hybrid drive-systems for rotorcraft applications.
DeSmidt, Hans, Ai, Zhisheng
Regression Test 08/22/24 - Tatsiana twrtwtwSAE-PP-094488/22/2024
QA Test
Mutagaana, Festo
Dynamics of a Variable Speed Hybrid-Electric Helicopter Propulsion SystemF-0080-2024-12525/7/2024
In this paper, a comprehensive dynamic simulation of a parallel hybrid gas-electric single main rotor helicopter involving a motor/generator (MG) pair and a differential planetary gear transmission (PGT) arrangement forming an electronic continuously variable transmission (E-CVT) was performed. This notional hybrid electric helicopter was sized based on a retrofit of a dual engine, 10000 lb, 2500 Hp class helicopter. The total weight added by the electric components was 182 lbs which increased the propulsion system weight from 1184 to 1366 lbs. The simulation results found that at 110 kts cruise, the hybrid electric system enabled a 27% reduction in main rotor rpm which resulted in an 18% reduction in the fuel burn rate. It is concluded that use of an E-CVT parallel hybrid propulsion system offers potential for increased flight range and reduced fuel consumption in medium to large-scale helicopter applications.
DeSmidt, Hans, Ai, Zhisheng
Coordination Control Strategy for Mode Switching of a Parallel Hybrid Electric System Based on Continuously Variable Transmission02-13-02-00108/11/2020
This study aims to solve the problem of impact in a parallel hybrid electric system based on the continuously variable transmission (CVT) during switching from pure electric mode to engine-driven, power-generating mode. Taking into account the torque response characteristics of the engine and motor and the dynamic characteristics of the wet clutch hydraulic control system, the mode switching process is divided into six stages, namely, pure electric mode, wet-clutch free travel, engine start-up, engine speed synchronization, clutch combination, and engine intervention drive. A coordination control strategy is developed based on the model predictive control algorithm to ensure smooth mode switching. The effectiveness of the control algorithm is verified using Matlab/Simulink and the AMESim co-simulation platform. Results show that with the mode switching coordination control strategy, the components of the system work harmoniously. The maximum impact is reduced by 52.0% at the speed synchronization stage and by 84.3% at the clutch coupling stage compared with the uncoordinated control situation.
Zeng, Xiaohua, Li, Xiaojian, Dong, Bingbing
Maximum Sound Level Potential for MotorcyclesJ47_202006 (Current)6/5/2020
This SAE Recommended Practice establishes the test procedure, environment, and instrumentation for determining the maximum sound level potential for motorcycles under wide open throttle acceleration and closed throttle deceleration.
Motorcycle Technical Steering Committee
Main Features of Forming the Transmission of an Active Multi-Link Road Train2020-01-04274/14/2020
The development of the economy and the associated growth in trade both within the country and international transport, the associated construction and development of transport routes using elements of intelligent transport systems constantly require increasing the efficiency of trunk transportation. In addition, the development of new economic regions with an undeveloped road network is impossible without high-capacity motor vehicles and cross-country ability. To achieve these goals, the creation of active road trains, including multi-link ones, based on non-traditional technical solutions, is required. The idea of using multi-link trains in the system of intercity and international transportation is not new. However, at the present stage of development of automotive technology requires rethinking and use of new achievements of science and technology. At present, the process of changing the design of land vehicles, qualitatively changing their structure and composition of the main power devices based on the integration of electronic, electrical, hydraulic, pneumatic and mechanical elements and significantly increasing the role of electronics and control systems, i.e. widespread introduction of mechatronic systems and modules in the design of a road train. The article describes some aspects of constructing the transmission of active road trains based on the mechatronic modular principle. Materials of the article are based on the results of theoretical and experimental studies conducted by the authors and with their participation. In this article, the term “mechatronics” is understood as a synthesis of electromechanics and microelectronics, combined by a common control and optimized according to system-wide criteria.
Belousov, Boris, Haritonchik, Sergey, Keller, Andrei, Bakhmutov, Sergey, Berdnikov, Alexey, Alyukov, Sergei, Alyukov, Alexander
Dynamics and Control of Gearshifts in Wet-Type Dual Clutch Transmission for BEVs2020-01-07674/14/2020
The dual clutch transmission is one of the possible choices for electric vehicle drivelines. The basic principle and control mode of shifting of wet dual clutch transmission are introduced, and the dynamic process of shifting of wet double clutch transmission is studied. Combined with the dynamic model of the wet clutch engagement process, the difference between the dynamic characteristics of the dual clutch transmission modeling using the Coulomb friction model and the dual-clutch transmission model using the average flow model and the micro-convex contact theory is analyzed. The shift control strategy of the dual clutch transmission proposes a correction method to improve the shifting smoothness. Studies have shown that the torque response of the wet clutch has significant hysteresis, and the improved control algorithm can significantly improve the shifting smoothness of the wet dual clutch transmission. Based on the dynamic model of the wet clutch, the torque interruption of the shift control strategy of the dual clutch transmission is studied, and the method of improving the shift smoothness by the correction of the shift control strategy is proposed.
Lou, Zhenxiong, Duan, Yupeng, Zhang, Yunqing
Two-Speed Transmission Gear Shift Process Analysis and Optimization Using Genetic Algorithm08-09-01-00011/16/2020
Electric Vehicle (EV) equipped with two-speed transmission has benefit in improving dynamic performance and saving battery consumption. However, during gear shift process, torque interruption and shift impact may lead to a bad shift quality. This work investigates gear shift process in an Automated Manual Transmission (AMT) configuration-based two-speed transmission. First of all, a typical gear shift process is analyzed. Parameters like motor speed, shift force, motor torque change rate, and speed difference between synchronizer and target engage gear are all included to find the relationships with shift duration. Then vehicle jerk is introduced as a criterion to evaluate shift impact. Besides, a comprehensive shift control strategy is developed. While keeping the output torque at wheels unchanged, the shift strategy also improved motor working efficiency after gear shift. Therefore, to determine an optimum shift strategy and achieve a balance among different parameters, Genetic Algorithm (GA) multi-objective optimization method is implemented. Through GA optimization, several solutions are presented and discussed. The final results can well satisfy the requirements of different objectives. This work provides a novel and efficient method for shift strategy development.
Cao, Zhan, Yang, Jiansen, Wang, Xinyu
Dynamic modeling and simulation of a powertrain system with a six-speed automatic transmission2019-36-01001/13/2020
The constant growth of the automotive market demands for comfort to the user and energy efficiency have caused the intensification of the industry researches and development of the automatic transmissions (AT). However, vehicles equipped with these gearboxes entails in higher fuel consumption levels than the one required by vehicles equipped with manual transmission. In the automotive industry due to the advantages offered using computer simulations, such as fast evaluation an optimization, many researchers are using virtual models for optimization of dynamic behavior of systems and fuel consumption. Aiming to study the dynamic behavior of an AT and the influence of its components on that behavior, this paper presents an AT dynamic model developed in MATLAB® / Simulink®. The AT model has three main subsystems: a torque converter model, which includes the dynamic of both the forward flow mode and the reverse flow mode; a Lepelletier gearbox model, composed by a set of three planetary gearsets in parallel, resulting in a six forward speeds gearbox; and a gear-shift schedule, which has the vehicle speed and accelerator pedal position as inputs of the model and the gear that should be selected in that condition as output of the model. The torque converter subsystem considers the transient and steady-state dynamic and their mainly operation dynamic characteristic: the conversion range, in which occurs a torque amplification and the stator is held; the coupling range, in which the stator freely rotates; and the transition periods from the forward to the reverse flow mode and vice-versa. The axial volume flow of the fluid, the speed and the torque of the three wheels (impeller, stator and turbine) were verified for the dynamic analysis of the system. In addition, the AT model was integrated into a MATLAB® / Simulink® vehicular dynamics and fuel consumption model in order to be analyzed under the ABNT 7024 standard speed profile.
de Araujo, Marcel T. da S., Falleiros, Murilo F., Gioria, Gustavo dos S.
Automatic Transmissions - Schematic DiagramsJ647_201911 (Current)11/19/2019
The following schematic diagrams reflect various methods of illustrating automotive transmission arrangements. These have been developed to facilitate a clear understanding of the functional interrelations of the gearing, clutches, hydrodynamic drive unit, and other transmission components. Two variations of transmission diagrams are used: in neutral (clutches not applied), and in gear. For illustrative purposes, some typical transmissions are shown.
Automatic Transmission and Transaxle Committee
Hybrid Transmission for Optimizing Input Machine Operation08-08-02-000811/14/2019
The hybrid transmission with a single energy source is presented in this article, which has the ability to, under certain constraints, transfer the energy from the input shaft with arbitrary variable speed onto the output shaft with the variable speed required for an output machine or propelling member operation - without a control system. The transmission is in a way similar to a power-split transmission for hybrid electric vehicles sans the battery and a power-split control logic. Development of a dedicated control system enables the optimal operation of the input machine. As an example, the transmission is designed for a passenger automobile. For the chosen automobile type, the power train is modeled in MATLAB/Simulink. In drive simulations during the single New European Driving Cycle (NEDC), the powertrain efficiency and fuel consumption are obtained and compared with two comparable vehicles: the conventional one and the advanced HEV. The competitiveness of the proposed transmission is proven.
Jelaska, Damir, Perkušić, Milan, Podrug, Srdjan, Tvrdić , Vjekoslav
WHAT WE'RE DRIVING19AUTP10_0710/1/2019
What first impresses about the GT is how easy it is to drive. Ingress is a little tricky over the wide sill, but once situated in the comfy driver's seat you use a strap to position the foot controls to your liking in a very cramped pedal box, and you have a few degrees of seatback angle to play with. The 3.5-L EcoBoost twin-turbo-charged V6 erupts to life from what feels like just behind your right earlobe, but settles quickly in a buzzing idle. Like many competition-focused machines, the V6 has a lightened-crank eagerness about it, but the “automatic” gearbox prevents any uneasiness about getting underway. Thanks to the rear-wheel-drive GT's low and centered mass, the engine can mutter away at low rpm while easily bringing the GT up to traffic speeds.
Innovative Dedicated Hybrid Transmission Concepts in the Next Generation of Hybrid Powertrains08-08-01-00059/20/2019
Due to the advantages of hybrid vehicles in comparison with pure electric vehicles, Hybrid Electric Vehicle (HEV)/Plug-in HEV (PHEV) no undoubtedly becomes the reasonable and practical solution in the development of vehicle electrification at the moment. Meanwhile, Dedicated Hybrid Transmission (DHT), as the especially designed hybrid transmission for HEV/PHEV, represents the development direction of hybrid vehicles. But in the market, the well-known DHT concepts are all protected by patents by large Original Equipment Manufacturers (OEMs). How to break the patents and more importantly develop the innovative DHT concepts in the next generation is of vital importance in the development of HEV/PHEV. In this article, firstly, the features and comparisons of different well-known DHT concepts are discussed and analyzed. The mechanical and electrical complexity are introduced to essentially analyze the advantage and disadvantage of different kinds of DHT concepts. Based on the analysis, the possibilities of different DHT concepts in the next generation are further analyzed and demonstrated. The innovative DHT are derived from the analysis. In comparison with DHT in the market, the innovative DHT concepts can on one hand break the DHT patents and, on the other hand, overcome the shortcomings of the present DHTs. Especially for the new possibilities of power-split DHT, the DHT concepts with the combined structure are newly introduced. With the combination of planetary gear set in Automatic Transmission (AT) and synchronizer/dog clutch in Dual Clutch Transmission (DCT), the advantages of both transmissions can be effectively integrated to realize the mode transition without power interrupt. In this way, the mechanical and electrical complexity of the concepts can reach an excellent balance. At last, the dynamics and economics of the new DHT concepts are further simulated and validated in the driving cycle. In conclusion, the new DHTs have many advantages both in structure and function compared with the DHTs in the market. It provides the new development direction of DHT in the next generation.
Chen, Haijun, Li, Lin, Lange, Andreas, Küçükay, Ferit
Ford amped for new phase of hybrid-electric offensive19AUTP06_126/1/2019
With the persistent auto-industry question of how soon battery electric vehicles will become mainstream options, Ford is preparing to widely deploy its fourth-generation hybrid-electric vehicle (HEV) technology that Dave Felipe, the VP of powertrain engineering, said will result in a fuel-efficient, performance-rich HEV variant for “all mainstream models” in North America. The company's wide-ranging plan to implement hybridization is a central aspect of its commitment to invest $11 billion in new electrification technology by 2022, said Felipe. He added that the new modular hybrid technology (MHT) system for its larger and heavier vehicles that often are used for towing makes Ford “the only OEM that's going to play in those places” with hybrid models-while market forces sort out how quickly electric vehicles are adopted for mass-market buyers.
Visnic, Bill
New design for 2020 Mitsubishi Outlander Sport as brand awaits alliance's new platforms, products19AUTP06_166/1/2019
The 2020 Mitsubishi Outlander Sport carries over with no mechanical changes compared to the 2019 model. But its new face-part of a front/rear styling redo plus new interior trims/tech for the 5-seat, 2-row SUV-signals a new start for the brand in the U.S. Having pared its product lineup to all-SUV plus the economy minded B-segment Mirage, the triple-diamond brand is saucing up its styling while it awaits a bevy of new platforms and products from its alliance with Nissan/Renault. Mitsubishi sold over 100,000 vehicles in the U.S. for the last two years running. Compared to the nearly 350,000 vehicles it sold in 2002 (or the 800K pickups Ford delivers in a year), this might not sound spectacular. But compared to the sub-54K year it had in 2009, the steady growth over the last 10 years (including a 14% jump last year in a flat-overall market) shows that life is returning to the brand.
Seredynski, Paul
Dynamic Interactions in an Electromechanical Main Gearbox of a High-Speed Coaxial Compound HelicopterF-0075-2019-146705/13/2019
To further increase the speed of conventional helicopters, several new concepts and technology demonstrators have been developed. This paper proposes an electromechanical main gearbox for a compound, coaxial helicopter. The speed and power variation of the main rotor between hover and high-speed cruise is realised by two brushless permanent magnet (BPM) machines and a differential planetary gear set that act as a continuously variable transmission (CVT). To assess such highly integrated hybrid applications, a novel analysis method is proposed that captures the influences of electrical motor and gear excitations in a full system approach. Alternative gear and motor designs are explored by completing speed sweeps through different operating conditions in the frequency domain. System responses are shown and indicate that motor and gear excitations can interact if their parameters are not selected carefully. This can lead to critical situations when hitting resonances and demonstrates the importance of considering electromechanical interactions from early design stages.
Park, Youn, Schlaich, Andreas
Modeling of the Automatic Power Distribution System among the Traction Motors of the Driving Wheels of a Multi-Axle Vehicle2019-01-09144/2/2019
Dynamics of acceleration, mobility, fuel efficiency of wheeled vehicles are largely determined by the drive circuit to the driving wheels and bridges, as well as devices used in drive link nodes to distribute power among the driving wheels. This is especially important for multi-axle wheeled vehicles. In this paper, the object of the study is a multiaxial wheeled vehicle with an electric transmission consisting of an internal combustion engine with a power of 720 kW, one common generator and twelve traction motors mounted directly on the driving wheels. In connection with the change in load on the driving wheels due to the variability of soil properties, driving conditions (acceleration, braking, uniform motion), terrain topography, it is necessary to provide external regulation of electric machines working in the transmission of the vehicle. The aims of the work are: 1) the study of currents and voltages in traction motors while changing the properties of the ground during the movement; 2) modeling of the automatic system providing full loading of the internal combustion engine and optimal distribution of power among the driving wheels with full fuel supply; 3) simulation of an automatic control system for traction motors, which provides the operation of the internal combustion engine with an economical characteristic for partial fuel supply and during acceleration. As a result of the study, the model of the automatic power distribution system among traction motors of the driving wheels of a multi-axle vehicle was developed, which made it possible to provide more efficient operation of the multi-axis vehicle.
Kondakov, Sergei, Pavlovskaya, Olga, Aliukov, Sergei, Smirnov, Vladimir
CVT, Promising Solutions for Electrification2019-01-03594/2/2019
A single speed transmission for electric vehicles (EV) puts specific requirements on the electric motor and battery to enable the full characteristics as offered by the internal combustion engine such as driving large distances at higher speed or towing a trailer. EV developers are facing several challenges in extending driving range, reducing recharge times and finding a performance and efficiency compromise between low and high-speed conditions. This study proposes a combination of a dedicated electric machine and a Continuously Variable Transmission (CVT) that offers a chance to overcome these challenges. The result is an efficient and cost effective solution where the surplus cost of the CVT is recovered within the powertrain by lowering cost of the electric components, cooling system and battery. A CVT reduces the maximum torque and speed requirement of the electric machine which enables a reduced size and cost of the active parts. The combination of a downsized electric machine and a pushbelt CVT can deliver the good performance that consumers expect from their EV. This paper combines the results of research into various topics to support these statements. A simulation based comparative study of various EV powertrain configurations shows that with respect to the single speed EV, efficiency benefits around 13% on WLTC are possible. A cost study based on the bill of materials furthermore concludes that a 6% cost benefit is achievable.
Van der Sluis, Francis, Romers, Luc, Van Spijk, Gert-Jan, Hupkes, Ingmar
Optimization of the Process of Acceleration of a Vehicle Taking into Account the Regimes of Operation of Its Engine2019-01-07764/2/2019
Currently, in order to effectively use the engine's energy resources and implement the required indicators of the traction, speed and fuel-economic properties of a vehicle, designers and manufacturers are trying to realize some certain properties to the transmission design that will ensure the most complete coordination of their joint work. However, even the optimal constructive solution cannot be universal, i.e. what is good for some operating conditions is not effective for other conditions. Therefore, today it is economically expedient to create vehicles intended for a certain, relatively narrow range of operating conditions. A wide range of modern continuously variable transmissions (CVT), as well as automatic control systems make it possible to radically change the approach to the design of vehicle transmissions. It remains only to determine the algorithms for changing the gear ratio of the CVT. The technique of a choice of optimum transfer numbers of CVT of a car in view of modes of movement and work of its engine is offered. The results of calculation of the traction-dynamic and fuel-economic parameters of a car with CVT, the gear ratios of which change during the movement in accordance with the proposed procedure, in comparison with the actual prototype, confirmed the accepted optimization hypothesis and gave all grounds for recommending the application of this technique to practice when choosing the gear ratios of continuously variable transmission, depending on the mode of movement of vehicle and regimes of operation of its engine.
Ulanov, Alexander, Aliukov, Sergei
Lexus soups-up seventh-generation ES sedan18AUTP11_1011/1/2018
Sedans and any configuration of a “car” might be a tough sell at the moment, but Toyota's Lexus division certainly wasn't going to let that stop it from launching a new, seventh generation of the ES midsize sedan, which by a large margin just happens to be the brand's best-selling car (51,398 last year in a shrinking U.S. market for sedan bodystyles). The ES typically accounts for nearly half of Lexus' total car sales. Considering that kind of sales critical mass, it's tough to say the ES has been injured by its reputation as being the softer “cruiser” of the Lexus car lineup, but the company seems to continually strive to inject more sporting character into the midsize sedan. Such is the case with the new 2019 ES-there are two variants, the ES350 with a 3.5-L V6 and the ES300h hybrid that went on sale in the U.S. in September-although refinement and isolation remain at the expected high levels.
Visnic, Bill
Dynamic Stability Analysis of High-Speed Traction Drive CVT for Aircraft Power Generation2018-01-193610/30/2018
The traction-drive integrated drive generator (T-IDG®) has been developed since 1999 to replace current hydrostatic transmission drive generators mounted on Japanese military aircraft. The T-IDG® consists of a generator and a half-toroidal traction-drive continuously variable transmission (CVT), which maintains a constant output speed of 24000 rpm, that is, a 400 Hz AC power supply. To cope with recent trends of more electric aircraft (MEA) and the need for weight reduction, a high-speed traction-drive CVT is advantageous over other transmissions. The torque on the half-toroidal variator is transmitted through multiple power rollers. The equal load sharing among power rollers is typically controlled by a mechanical hydraulic feedback system, whose stability is one of the main issues for the high-speed traction-drive CVT. Previous studies have shown that insufficient damping and stiffness of the mechanical hydraulic feedback system cause self-induced vibration. We found that the support stiffness of the variator also affects the stability of the feedback system when it is driven at a high speed. This paper describes the theoretical criteria to maintain the stability of the load-sharing system of the power rollers of the high-speed CVT. A test to validate the theory is also conducted with a prototype traction-drive CVT at speeds of up to 20000 rpm with a peripheral speed of the traction contact of 70 m/s. The test results show that the vibration is excited at high rotational speeds when the variator is supported with a low-stiffness bearing support. We conclude that a high-stiffness support is necessary to transmit the power stably with a high-speed traction-drive CVT.
Matsuda, Kippei, Goi, Tatsuhiko, Tanaka, Kenichiro, Imai, Hideyuki, Tanaka, Hirohisa, Sato, Yasukazu
Super Low Viscosity ATF; AW-22018-01-17569/10/2018
Reducing loss torque in automatic transmissions (ATs) is a key factor in improving fuel economy. A promising approach is to reduce the viscosity of the Automatic Transmission Fluid (ATF) so as to minimize churning loss. Aisin AW and JXTG Nippon Oil & Energy Corporation have developed a super low viscosity ATF, called “AW-2”, which has approximately 50% lower kinematic viscosity at 40 °C compared to the conventional ATF “AW-1”. It is generally understood that if the viscosity of an ATF is too low, it can have a negative impact on the fatigue life of components such as gears and bearings, and possibly lead to increased wear or seizure. AW-2 was designed to solve these problems via the application of two key technologies. The first is a high performance base oil with a low traction coefficient, which translates to low viscosity under high pressure conditions. This decreases the shear resistance between sliding surfaces under elastohydrodynamic lubrication (EHL) conditions, which contributes in improving the fatigue life of bearings and other components. The second is an ester type base oil with high polarity. It was found that the amount of ester base oil used has a major influence on fatigue life. The adsorption of esters onto metal surfaces is thought to improve lubricity in severe lubrication conditions. Durability tests were performed in a wide range of conditions, using gear and bearing components and actual transmission units, and it was confirmed that AW-2 outperforms AW-1, despite its super low viscosity. Furthermore, AW-2 reduced loss torque in the transmission by approximately 10% compared to AW-1.
Masuda, Kohei, Nakao, Hajime, Komatsubara, Hitoshi, Kurosawa, Osamu, Yamada, Katsuhito, Ishikawa, Kazunori, Mori, Atsushi
Mass and Kinematic Analysis of Compound Split with Simulation of the Shifting Process for Variable Rotor SpeedF-0074-2018-128545/14/2018
ABSTRACT The investigation presented in this paper is part of the project VARI-SPEED which aims to invent a speed variable drivetrain for different rotorcraft configurations. A kinematic and a mass analysis of compound split transmissions (CS) variations and a rotorcraft drivetrain simulation model to analyze the dynamic behavior during rotor speed change were performed. All solutions have the same power flow in the variator path but different fixed carrier transmission ratios of the planetary gears, which lead to a difference in mass. CS can be used as two speed transmissions and as continuous variable transmissions (CVT). As a two speed transmission less torque and friction energy is induced in the clutches than in a double clutch transmission, but CVT enable a smooth transition with no friction losses. CS offer the opportunity to vary rotor speed which decreases the overall power demand and lead to a more ecologically efficient rotorcraft aviation.
Amri, Hanns, Hartenthaler, Katharina, Weigand, Michael
Dynamic Lever: Key to Automotive Transmission and Drivetrain Dynamics2018-01-11654/3/2018
Lever analogy has been developed for more than 30 years. The powerful tool can greatly simplify transmission analysis and has been widely used for transmission powerflow analysis, selection, and control synthesis. In the past two decades, automatic transmissions have undergone a rapid growth with continual increase in the number of speeds and electrification. The increase in the system complexity has presented great challenges to system integrations. Many unpredicted issues have been NVH related and difficult to troubleshoot, partially due to the lack of proper modeling and analysis tool to capture the drivetrain dynamics including transmission components. Although the lever analogy has played important roles in the system design, the current form is not adequate and has never been used for dynamic analysis for the transmission and drivetrain system. In this article, we will introduce the dynamic lever model framework and analysis method to address the dynamic aspect of a transmission and drivetrain system. This analytical model framework allows one, for the first time, to systematically comprehend all possible dynamic structures within a drivetrain system. We will show that the dynamic lever framework can add the desired dynamic analysis capability to the existing lever analogy-based methods and will be a powerful tool proven to be effective in transmission analysis, control design, and troubleshooting.
Li, Dongxu
New 2.0L I4 Gasoline Direct Injection Engine with Toyota New Global Architecture Concept2018-01-03704/3/2018
Toyota Motor Corporation has developed a new 2.0L Inline 4- Cylinder (I4) Gasoline Direct Injection Engine, the second Naturally Aspirated (NA) engine of the Toyota New Global Architecture (TNGA) engine series, to meet our customers’ expectations for drivability, performance, and fuel economy. The high speed combustion technologies adopted previously in our 2.5 L NA conventional and Hybrid Vehicle (HV) engines for the 2018 Toyota Camry are necessary for high engine power and thermal efficiency. To adopt our high speed combustion technology on engines with different displacements, the turbulence intensity has been defined as the target index of combustion speed. The basic engine structure has been revised by using Computational Fluid Dynamics (CFD) analysis to achieve the combustion target. Additionally the Toyota dual injection system D-4S (Direct injection 4 stroke gasoline engine Superior version) has been improved by our new multi-hole injector design to reduce fuel wetting due to the smaller displacement. With these new technologies, and further optimization, the new 2.0L I4 gasoline direct injection engine achieved top level specific power and thermal efficiency in its class. As a result the new 2.0L Gasoline Direct Injection Engine, in combination with the newly developed Continuously Variable Transmission (CVT), allow our vehicles to achieve top acceleration, vehicle performance, and fuel economy.
Yamaji, Kazunori, Tomimatsu, Makoto, Takagi, Isao, Higuchi, Akihiko, Yoshida, Takashi, Murase, Eiji
Nonlinear Hybrid Optimization for the Powertrain of a Four-Wheel-Drive (4WD) Vehicle2018-01-12304/3/2018
Lightweight of the structure is known as an effective approach to improve fuel economy and handling of the automobile. Moreover, the optimization for the powertrain increases the acceleration performance and reduces the energy consumption of driven components. In this paper, a popular powertrain of a Four-Wheel-Drive (4WD) vehicle is considered as a research object. The nonlinear hybrid mathematical model of optimization is created. The target function, whose value varies with continuous and discrete variables, is the combined moment of inertia consisting of transmission and sub-actuator. The constraints include the gear surface fatigue, gear bending fatigue, the belt tensile failure and so on. The design variable involves the sizes of gears and sheaves, the gear thickness, the numbers of sheaves and so on. Finally, some results based on the nonlinear programming principles are derived, and relative conclusions are drawn.
Wu, Huyao
Inertial Continuously Variable Transmissions and Ways to Improve Their Performance2018-01-10594/3/2018
The inertial continuously variable transmissions are transmissions of mechanical type. They have a number of advantages in comparison with other types of transmissions. For example, they have a big value of the coefficient of efficiency, since the principle of their action does not imply the need to convert energy from one type to another one. These transmissions have a compact design, a wide range of torque transformation. They can operate in direct mode, smoothing the torsional vibrations in the system. At the moment when the output shaft is stopped, the input transmission shaft continues to rotate, that prevents the engine from overloading. There are other advantages. But despite these advantages, the inertial transmissions are not widely used in the automotive industry. The main reason for this is the inadequate durability of the freewheel mechanisms involved in the designs of the inertial transmissions. The paper considers some ways to improve the efficiency and durability of the inertial transmissions. Dynamics of the inertial transmissions is considered. For this purpose, physical and mathematical models of the inertial transmissions have been developed. The transmissions have a variable structure, nevertheless, new mathematical methods have been developed in the paper, which made it possible to describe the dynamics of the transmissions in the form of only one system of differential equations. On the basis of the developed mathematical model, periodic solutions of the system are constructed, and the external characteristic of the inertial transmissions is obtained. It is shown that the obtained external characteristic is close to ideal one. To increase the reliability and durability of the inertial transmissions, a new design of the overrunning clutches is proposed, which is distinguished by increased capacity of operating. The proposed design has a new principle of activity. It is shown that the load on the details of the developed overrunning clutches can be reduced in several times in comparison with the existing designs of overrunning clutches. A mathematical model of the proposed design of the overrunning clutches is investigated in this paper. Periodic solutions of the systems of differential equations that describe the dynamics of the overrunning clutches with the new principle of action are constructed. It is shown that the application of the proposed design allows increasing significantly the durability of the inertial transmissions. In this paper computer simulation was carried out, which confirmed the correctness of the results of the theoretical studies.
Aliukov, Sergei, Keller, Andrei, Alyukov, Alexander
Development of a Torque-Based Control Strategy for a Mode-Switching Hydraulic Hybrid Passenger Vehicle2018-01-10074/3/2018
An increase in the number of vehicles per capita coupled with stricter emission regulations have made the development of newer and better hybrid vehicle architectures indispensable. Although electric hybrids have more visibility and are now commercially available, hydraulic hybrids, with their higher power densities and cheaper components, have been rigorously explored as the alternative. Several architectures have been proposed and implemented for both on and off highway applications. The most commonly used architecture is the series hybrid, which requires an energy conversion from the primary source (engine) to the secondary domain. From he re, the power flows either into the secondary source (high-pressure accumulator) or to the wheels depending upon the state of charge of the accumulator. A mode-switching hydraulic hybrid, which is a combination of a hydrostatic transmission and a series hybrid, was recently developed in the author’s research group. This paper focuses on the development of a new controller for the mode-switching hydraulic hybrid prototype. A uniform torque-based control strategy is proposed, which, along-with a supervisory controller decides on the usage of the high-pressure accumulator, thereby switching the vehicle mode from hydrostatic to series hybrid, among others. The supervisory controller analyzes the driving scenario, the system states and the user power demand to select the optimum vehicle-driving mode. This improved control strategy allows the vehicle to operate in higher efficiencies and the uniform control type results in a better “driver-feel”. The development of the control strategies, their implementation on the prototype vehicle and the test results are discussed in this paper.
Banerjee, Pranay, Ivantysynova, Monika
Transmission-Mounted Power Control Unit Including 12-Volt DC-DC Converter for Two-Motor Hybrid System2018-01-04574/3/2018
This research proposes a third-generation power control unit (PCU) for a two-motor hybrid system. To make a more compact intelligent power unit (IPU) to be located under the second seat, a PCU with a 12-volt DC-DC converter (DCDC) that mounts directly on the transmission was developed, whereas the DCDC was previously mounted within the IPU. Since this has a considerable impact on the engine room layout, the technology described below was used to make the PCU even more compact than the second-generation unit. The power module, a key component of the PCU, now uses Ag nanoparticles sintering bonding rather than conventional solder bonding. This helps lower thermal resistance and enables smaller power semiconductors. The voltage control unit (VCU) has a new circuit that uses a multi-stage switching circuit and electric power transfer capacitor instead of the conventional chopper circuit. This makes it possible to shrink the reactor to less than 65% of its usual volume without raising the carrier frequency, and enables a layout that efficiently uses both sides of the water jacket (W/J), so that no specially designed W/J needs to be added just for the DCDC. As for the W/J seal, friction stir welding (FSW) to increase rigidity was used to reduce seal width and to make the W/J itself more compact. The use of these compactness technologies enabled the PCU to maintain all the efficiency of a second-generation PCU and made it possible to build the DCDC in the PCU with its volume less than a second-generation one. Development of this PCU makes the IPU much more compact and provides a similar amount of trunk space as in a gasoline-powered vehicle.
Ozuchi, Yasuhiro, Tomokage, Ryoji
Supervisory Model Predictive Control of a Powertrain with a Continuously Variable Transmission2018-01-08604/3/2018
This paper describes the design of a supervisory multivariable constrained Model Predictive Control (MPC) system for driver requested axle torque tracking with real-time fuel economy optimization that is scheduled for production by General Motors starting in 2018. The control system has been conceived and co-developed by General Motors and ODYS. The control approach consists of a set of linear MPC controllers scheduled in real-time based on powertrain operating conditions. For each MPC controller, a linear model is obtained by system identification with vehicle and dynamometer data. The supervisory MPC coordinates in real time desired Continuously Variable Transmission (CVT) ratio and desired engine torque to satisfy the system requirements, based on estimates of axle torque and engine fuel rate, by solving a constrained optimization problem at each sampling step. Each linear MPC controller is equipped with a Kalman filter to reconstruct the system state from available measurements. Compared to more classical controls, the presented MPC approach achieves better coordination of powertrain actuators to satisfy system requirements, while maintaining robustness with respect to measurement noise, ambient conditions, and part-to-part variations. Moreover, the systematic, model-based framework developed for production enables a potential adaptation of the design to different powertrain architectures.
Bemporad, Alberto, Bernardini, Daniele, Livshiz, Michael, Pattipati, Bharath
Drivecycle Benefits of Controlling Airflow with the SuperTurbo™2018-01-09704/3/2018
The SuperTurbo™ is a driven turbocharger that uses a high-speed traction drive combined with a CVT (Continuously Variable Transmission) or electric motor to provide additional power to or from the turbo shaft. The CVT can be shifted to a ratio that provides a turbo speed that generates a desired boost pressure and air flow rate to the engine. Unlike a conventional turbocharger, where the turbine and compressor powers must be balanced, the a driven turbocharger can provide additional power to the turbo shaft through supercharging when the turbine is not collecting sufficient power to drive the compressor to the desired boost pressure, and during other operating conditions can absorb excess turbine power through turbo-compounding to improve engine efficiency. This direct control of air flow to the engine enables greater flexibility in engine operation. The topics presented focus on heavy-duty diesel engines, but the concepts can be applied to all engine types. Transient response is improved, as well as fuel efficiency during transient operation of diesel engines, as excess fueling to provide exhaust energy to the turbine is avoided. Instead, additional airflow is provided to the engine through supercharging to increase combustion efficiency. This aids in engine downspeeding, as well as downsizing, to provide improved drivability of the vehicle. Simulations and engine testing show that efficient transients can provide a fuel savings of up to 6% over a transient drivecycle, and the ability to downspeed the engine can provide an additional 3% efficiency gain. Overall, the ability to directly control airflow to the engine provides flexibility for engine operation that is not possible with a conventional turbocharger.
Brown, Jared W., Waldron, Thomas
WHAT WE'RE DRIVING18AUTP02_152/1/2018
It isn't every carmaker that introduces its new model with a session on a tight and slippery test track. But when it's a 1955-kg (4090-lb) sedan with 450 kW (603 hp) and 850 N·m (627 lb·ft) available at the shove of a foot, it is a useful education. That's what Mercedes-Benz offers its U.K. buyers of the new Mercedes-AMG E 63 S 4Matic+.
DANA OPENS NEW CHAPTER ON CVTs18AUTP01_041/1/2018
A dedicated development center is hustling the unique VariGlide “spherical traction drive” toward 2020 production. Any emerging technology that warrants its own dedicated development center-40,000 ft2, staffed by 40 engineers and loaded with state-of-art design engineering, analysis, metallurgy, machining, prototyping and test cells with four dynamometers-must be considered a competitive threat. That's the buzz within the powertrain community about Dana's Cedar Park, TX, tech center, and the highly anticipated VariGlide continuously-variable planetary transmission under development there since 2014. VariGlide is slated to enter production at one or more light vehicle OEMs in 2020. Dana engineers claim it will offer up to 10% greater fuel efficiency than incumbent CVTs, with improved drivability and NVH characteristics. It is “highly scalable” according to company engineers and its compact design enables it to effectively slot into existing transmission housings without significant modification.
Brooke, Lindsay
Continuously Variable Transmission (CVT) Fuel Economy2017-01-235510/8/2017
Due to its simplicity and fuel economy benefit, continuously variable transmission (CVT) technology has gained a lot of attention in recent years. Market penetration of CVT technology is increasing rapidly compared to step-type automatic transmission technology. OEMs, Tier 1 suppliers, and lubricant suppliers are working to further improve the fuel economy benefit of CVTs. As a lubricant supplier, we want to understand the effects of fluid properties on CVT fuel economy (FE). We have formulated fluids that had KV100 ranges from 2-4 cSt to 7-9 cSt with various types and viscosities of base oils. Wide ranges of viscosity indexes, steel-on-steel friction, and other properties were tested. Full vehicle fuel economy tests were performed in a temperature controlled environment with a robotic driver. The test revealed that there was more than 3% overall FE variation compared to a reference fluid. Iron content analysis following each test confirmed there was no noticeable transmission wear, and average sump temperature increase was found to be more dependent on driving cycle rather than fluid.
Kwak, Yungwan, Cleveland, Christopher
A Comparative Study on Fuel Economy for CVT and 9-speed AT based Vehicles2017-01-243510/8/2017
It is well-known that, compared with automatic transmissions (ATs), continuously variable transmission (CVT) shows advantages in fuel saving due to its continuous shift manner, since this feature enables the engine to operate in the efficiency-optimized region. However, as the AT gear number increases and the ratio gap narrows, this advantage of CVT is challenged. In this paper, a comparative study on fuel economy for a CVT based vehicle and a 9-speed automatic transmission (AT) based vehicle is proposed. The features of CVT and AT are analyzed and ratio control strategies for both the CVT and 9-speed AT based vehicles are designed from the view point of vehicle fuel economy, respectively. For the 9-speed AT, an optimal gear shift map is constructed. With this gear shift map, the optimal gear is selected as vehicle velocity and driving condition vary. Vehicle simulators are developed using MATLAB/Simulink, including the core components such as engine, clutch, CVT, 9-speed AT and so on. The performances of both vehicles with different transmission types are analyzed using the developed vehicle simulator. The influences of different transmission types and ratio change manners on the operation efficiency of engine and vehicle fuel economy are investigated. It is found from the simulation results that, although CVT shows an advantage in improving the engine efficiency by 8.1% due to its continuous ratio change, 3.8% improvement of fuel economy is achieved by the 9-speed AT based vehicle for the whole driving cycle of FTP-72.
Ji, Jian, He, BoZhou, Yuan, Lei
Driveline Ratio Selection and Shift Map Optimization for Automatic Transmission Vehicle at Concept Phase through Simulations06-11-01-000510/8/2017
Traditionally driveline ratios are selected based on trial and error method of proto vehicle testing. This consumes lot of time and increases overall vehicle development effort. Over last few decades, simulation-based design approach has been extensively used to alleviate this problem. This paper describes torque converter and final drive ratio (FDR) selection at concept phase for new Automatic Transmission (AT) vehicle development. Most of the critical data required for simulating vehicle performance and fuel economy (FE) targets were not available (e.g. shift map, clutch slip map, pedal map, dynamic torque, coast down, etc.) at an initial stage of the project. Hence, the risk for assuming right inputs and properly selecting FDR/Torque converter was particularly high. Therefore, a validated AVL Cruise simulation model based on an existing AT vehicle was used as a base for new AT vehicle development to mitigate the risk due to non-availability of inputs. The simulation model shows 97% correlation with the test results by using base shift map. The shift map was further optimized by using Gear Shifting Program (GSP) and FE improved by ~ 1.5% over base shift map without deterioration in performance. Finally, Torque converter and FDR were selected based on Performance and FE trade-off through simulation. The new AT proto vehicle was built with suggested configuration and Jury feedback on drivability on proto vehicle was found to be excellent. The FDR and Torque converter were subsequently confirmed to supplier for mass production. Hence, the FDR and torque converter selected by simulation met the requirements of “First Time Right” Quality Crusade while conforming to strict project deadlines.
Paulraj, Srinivasan, Muthiah, Saravanan
Composition Platform for Conventional and Hybrid Powertrains2017-24-01729/4/2017
In view of the rapidly increasing complexity of conventional as well as hybrid powertrains, a systematic composition platform seeking for the global optimum powertrain is presented in this paper. The platform can be mainly divided into three parts: the synthesis of the transmission, the synthesis of the internal combustion engine (ICE) and the optimization and evaluation of the entire powertrain. In regard to the synthesis of transmission concepts, a systematical and computer-aided tool suitable both for conventional und hybrid transmissions is developed. With this tool, all the potential transmission concepts, which can realize the desired driving modes or ratios, can be synthesized based on the vehicle data and requirements. As a result of the transmission synthesis, the detailed information of each transmission concept, including the transmission structure, the shifting logic, the estimated efficiency in each gear, and the estimated space arrangement of the transmission can be given out. The synthesis of transmission concepts is complemented by a comprehensive tool able to synthesize internal combustion engines of gasoline and gasoline/Atkinson type. The ICE synthesis precalculates frictional and thermodynamic engine behavior and is validated by an ad hoc created database of 250 engines, which serves as a comparison. Design parameters are deducted from this database in order to minimize the number of input parameters for the ICE synthesis. The result of the ICE synthesis is a map of the specific fuel consumption or an effective efficiency map. The tool is implemented as a function to the overall powertrain synthesis and will be triggered by an optimizer during the future development progress. Successively, the two synthesizing tools are joined to compose complete powertrains. Each powertrain concept consists of design parameters and corresponding configurations of synthesized ICE and transmissions. By varying these parameters, the different powertrains are further optimized and evaluated in consideration of the system efficiency and vehicle dynamics within the driving cycle.
Chen, Haijun, Li, Lin, Schudeleit, Mark, Lange, Andreas, Küçükay, Ferit, Stamme, Christian, Eilts, Peter
Automotive Transmission TerminologyJ645_201708 (Historical)8/25/2017
The following listed definitions are intended to establish terminology and criteria for describing the various kinds of automotive transmissions. A specific arrangement may be described by a combination of several of these definitions.
Automatic Transmission and Transaxle Committee
Electric Baggage/Cargo TractorARP1804B (Current)6/9/2017
This SAE Aerospace Recommended Practice (ARP) outlines the design and performance requirements for a battery-powered electric tow tractor for the handling of baggage or cargo trailers in airline service. The use of “shall” in this document indicates a mandatory requirement. The use of “should” indicates a recommendation or that which is advised but not required.
AGE-3 Aircraft Ground Support Equipment Committee
Modeling of Dynamic Processes for Inertial Continuously Variable Transmissions2017-01-10603/28/2017
The inertial continuously variable transmissions are mechanical transmissions that are based on the principle of inertia. These transmissions have a lot of advantages. Usually, the design of the inertial continuously variable transmissions consists of inertia pulsed mechanism with unbalanced inertial elements and two overrunning clutches. Dynamics of the transmissions is described by systems of substantial nonlinear differential equations. In general, precise methods of solution for such equations do not exist. Therefore, in practice, approximate analytical and numerical methods must be employed. The main analytical methods employ successive approximation, a small parameter, or power series expansion. Each approach has its advantages and disadvantages. Therefore, we need to compare them in order to select the best method for dynamic study of such kind of transmissions. In this paper a comparative analysis of approximate methods of solving of differential equations for the inertial continuously variable transmissions is done. The object of the investigation is structural dynamics of the continuously variable automatic inertial mechanical transmissions. Approximate methods of solving the nonlinear differential equations of motion of inertial transmissions based on a pulsed mechanism are compared. These methods take account of the no uniform driveshaft rotation and the dynamic characteristics of the motor. Analysis of the solutions reveals the best method for dynamic study of the given transmissions. The comparative analysis showed that the best method of approximate solution is the method of a small parameter.
Aliukov, Sergei, Keller, Andrei, Alyukov, Alexander
Brake Clutch Assisted Mode Transition Control for Compound Power-Split Vehicle2017-01-11703/28/2017
Because a compound power-split transmission is directly connected to the engine, dramatic fluctuations in engine output torque result in strong jerks and torque losses when the hybrid vehicle is in mode transition from electric drive mode to hybrid drive mode. In order to enhance ride comfort and reduce the output torque gap during mode transition process, a brake clutch assisted coordinated control strategy was developed. Firstly, the dynamic plant model of the power-split vehicle including driveline model, engine ripple torque and brake clutch torque was deduced. Secondly, the brake clutch assisted mode transition process was analyzed, and the output torque capability was compared between cases of both brake clutch assisted and unassisted mode transition process. Thirdly, a coordinated control strategy was designed to determine the desired motor torque, brake clutch torque, engine torque, and the moment of fuel injection. Finally, the effectiveness of coordinated control strategy was verified by vehicle test. The experimental results indicate that the proposed strategy was effective to suppress driveline speed oscillations during engine cranking phase, and reduce the engine cranking time.
Zhang, Tong, Wang, Chen, Zhou, Wentai, Cheng, Huijun, Yu, Haisheng
Development of Multi Stage Hybrid Transmission2017-01-11563/28/2017
Toyota Motor Corporation developed the Multi Stage Hybrid System for the Lexus flagship LC500h coupe with the aim of achieving an excellent balance between fuel economy and acceleration performance. The Multi Stage Hybrid Transmission used in this new hybrid system includes a shift device located immediately after the power split device and motor. Compared with previous hybrid systems, acceleration performance is improved by increasing the driving force at low and medium vehicle speeds in lower gears, fuel economy and heat management performance are improved by reducing electrical loss by selecting the optimal gear depending on the driving state. The Multi Stage Hybrid Transmission uses a shift device with a wide gear ratio range to maximize both fuel economy and acceleration performance. The transmission was designed to achieve the appropriate size to be mounted in a new platform, as well as class-leading low noise levels for adoption in luxury vehicles. It also includes a quickly responsive and accurate hydraulic control system that achieves excellent shift performance. This paper describes the hardware of the Multi Stage Hybrid Transmission.
Okuda, Koichi, Yasuda, Yuji, Adachi, Masatoshi, Tabata, Atsushi, Suzuki, Haruhisa, Takagi, Kiyonori, Atarashi, Tomoo, Horie, Ryuta
Development of Multi Stage Hybrid System for New Lexus Coupe2017-01-11733/28/2017
Lexus launched the new hybrid luxury coupe LC500h in 2017 to help enhance its brand image and competitiveness for the new generation of Lexus. During the development of the LC500h, major improvements were made to the hybrid system by adopting the newly-developed Multi Stage Hybrid System, which combines a multi stage shift device with the transmission from the previous hybrid system to maximize the potential of the electrically-controlled continuously variable transmission. Optimum engine and electrical component specifications were designed for the new vehicle and transmission. As a result, the LC500h achieves a 0-to-60 mph acceleration time of 4.7 seconds, with a combined fuel economy of 30.0 mpg while satisfying SULEV emissions requirements. Two controls were constructed to help resolve the issues that arose due to adding the shift device. A model-based shift control that calculates the torque for the electrical components during shifts was established using an optimal control method. The power management control, which ensures the input and output power of the lithium-ion battery in the LC500h, was modified by applying compensators to reduce delays in detecting speeds of electrical components and providing torque request to the electrical components. Additionally, a control simulating a ten-speed transmission was established to enhance dynamic drivability in line with the intentions of the driver when accelerating, to eliminate the rubber band effect using the characteristics of the shift device.
Kato, Shunya, Ando, Ikuo, Ohshima, Koji, Matsubara, Tooru, Hiasa, Yasuhiro, Furuta, Hideki, Mori, Yuma
An Advanced Automatic Transmission with Interlocking Dog Clutches: High-Fidelity Modeling, Simulation and Validation2017-01-11413/28/2017
Fuel economy regulations have forced the automotive industry to implement transmissions with an increased number of gears and reduced parasitic losses. The objective of this research is to develop a high fidelity and a computationally efficient model of an automatic transmission, this model should be suitable for controller development purposes. The transmission under investigation features a combination of positive clutches (interlocking dog clutches) and conventional wet clutches. Simulation models for the torque converter, lock-up clutch, transmission gear train, interlocking dog clutches, wet clutches, hydraulic control valves and circuits were developed and integrated with a 1-D vehicle road load model. The integrated powertrain system model was calibrated using measurements from real-world driving conditions. Unknown model parameters, such as clutch pack clearances, compliances, hydraulic orifice diameters and clutch preloads were estimated and calibrated. Simulation results, such as vehicle acceleration, turbine speed, and output shaft speed, are reported and compared with the measured data to validate the transmission model. Subsequently, the transmission model was coupled with internal combustion engine and road load models. This arrangement permitted investigating the dog clutch engagement dynamics under transient conditions. The relative speed of the dog clutch halves was found to be highly sensitive to the transmission input torque, which indicates that a precise engine torque control schemes are necessary for successful engagement.
Alzuwayer, Bashar, Prucka, Robert, Haque, Imtiaz, Venhovens, Paul
Development of Shift Control System for Multi Stage Hybrid Transmission2017-01-11503/28/2017
Toyota Motor Corporation developed a new hybrid system, Multi Stage Hybrid System, for the Lexus flagship coupe LC500h with the aim of achieving an excellent balance between fuel economy and acceleration performance. The Multi Stage Hybrid Transmission used in this new hybrid system includes a shift device located immediately after the power split device and motor. Compared with previous hybrid systems, the new hybrid system improves fuel economy by reducing electrical loss in the optimal gears, which are selected depending on the driving state. The system also improves acceleration performance by increasing the driving force at low and medium vehicle speeds in lower gears. In addition, the range of the power split device that cooperates with the shift device was widened to enable both an electrically-controlled continuously variable transmission mode and a ten-speed transmission mode, which creates a direct shift feeling to improve driving pleasure. This system contains many independent variables given by the interactions of the engine, generator, motor, and shift device. Thus, conventional control methods were not appropriate for devising the shift control of the system. In addition, shift performance may also be affected by the particular constraints of a hybrid system, such as battery limitations. This paper describes the shift control system for the Multi Stage Hybrid Transmission that was developed to resolve these issues.
Kumazaki, Kenta, Matsubara, Tooru, Kobayashi, Nobufusa, Kato, Shunya, Shiiba, Kazuyuki, Ando, Ikuo, Kimura, Hiromichi, Endo, Hiroatsu
Concept and Approach of Multi Stage Hybrid Transmission2017-01-10983/28/2017
Lexus developed the Multi Stage Hybrid Transmission for the flagship Lexus LC500h coupe with the aim of achieving an excellent balance between fuel economy and acceleration performance. To gain these benefits, this transmission utilizes a multi-stage approach with the input split mode as an enabler for a concept of multiple high- efficiency points. In order to apply this approach to the transmission, a shift device was located immediately after a power split device. For functioning of the input split mode electrically-controlled continuously variable transmission, the power split device is connected with the motor, generator, and inverters. The optimal gear selection of the shift device to reduce the power loss in accordance with the driving state improves not only fuel economy but also heat management performance compared with the previous hybrid transmission. The Lower gears of the shift device that amplifies both the motor and the engine torque enhances acceleration performance compared with the previous hybrid transmission which amplifies only the motor torque. This paper describes the motivation for selecting the multi-stage approach with the input split mode from implementations of multiple high-efficiency points concept, and the potential of multi-stage approach with the input split mode compared to the previous hybrid transmission.
Imamura, Tatsuya, Tabata, Atsushi, Matsubara, Tooru, Iwase, Yuji, Kumazaki, Kenta, Imai, Keita
Analysis of Methods for Solution of Differential Equations of Motion of Inertial Continuously Variable Transmissions2017-01-11053/28/2017
The inertial continuously variable transmissions are mechanical transmissions that are based on the principle of inertia. These transmissions have a lot of advantages. Usually, the design of the inertial continuously variable transmissions consists of inertia pulsed mechanism with unbalanced inertial elements and two overrunning clutches. Dynamics of the transmissions is described by systems of substantial nonlinear differential equations. In general, precise methods of solution for such equations do not exist. Therefore, in practice, approximate analytical and numerical methods must be employed. The main analytical methods employ successive approximation, a small parameter, or power series expansion. Each approach has its advantages and disadvantages. Therefore, we need to compare them in order to select the best method for dynamic study of such kind of transmissions. In this paper a comparative analysis of approximate methods of solving of differential equations for the inertial continuously variable transmissions is done. The object of the investigation is structural dynamics of the continuously variable automatic inertial mechanical transmissions. Approximate methods of solving the nonlinear differential equations of motion of inertial transmissions based on a pulsed mechanism are compared. These methods take account of the no uniform driveshaft rotation and the dynamic characteristics of the motor. Analysis of the solutions reveals the best method for dynamic study of the given transmissions. The comparative analysis showed that the best method of approximate solution is the method of a small parameter.
Aliukov, Sergei, Alyukov, Alexander
Inertia Continuously Variable Transmissions and Investigation of their Dynamics2017-01-11033/28/2017
The inertial continuously variable transmission is a mechanical transmission which is based on the principle of inertia. This transmission has a lot of advantages, namely: compactness, minimum friction losses and high efficiency as a result of the relatively small number of rotating components, a wide range of transformation of the torque. It does not need any conventional friction clutches. This transmission protects the engine from overload when the output shaft is braked. This drive guarantees optimum conditions of work for the engine regardless of the changing of load, and smoothly changes output speed according to the load. Mostly, design of this transmission consists of a pulsed mechanism with unbalanced inertial units and two overrunning clutches. The objects of the investigation are structural dynamic analysis of the continuously variable transmission. The physical and mathematical models of this transmission are developed. For these models of the transmission the differential equations of structural dynamics in the form of second kind Lagrange's equations were developed. Dynamics of the transmissions is described by systems of substantial nonlinear differential equations. In general, precise methods of solution for such equations do not exist. Therefore, in practice, approximate analytical and numerical methods must be employed. Each approach has its advantages and disadvantages. Besides, the nonlinear differential equations were solved on the basis of Runge-Kutta numerical method. The described methods allow increasing the durability of the transmission and created transmission with higher level of reliability in comparison with existing designs of such a kind of transmissions. In this paper, a new design of the inertial transmission with only one overrunning clutch is suggested. This transmission provides a high level of the load ability. Besides, the periodic solutions of the equations were also received by means of the numerical methods. Optimal working modes of the transmission were found using these periodical solutions.
Aliukov, Sergei, Keller, Andrei, Alyukov, Alexander
Research on Optimal Gearshift Strategy for Stepped Automatic Transmission Based on Vehicle Power Demand2017-01-11083/28/2017
Selection of gearshift point plays an important role in the field of automatic transmission technology, which directly affects the vehicle dynamic and economic performance, etc. In order to designing optimal gearshift strategies for conventional passenger vehicles equipped with stepped automatic transmission, in this paper, the vehicle power demand was defined under different environment, different driving intention and different vehicle operating conditions. Dynamic programming (DP) method is used to solve the optimal static gearshift decision sequence based on the simplified model of powertrain system. The drivability is respected by imposing an inequality constraint on the power reserve limit and the fuel economy is the objective function. Considering the change of vehicle additional load and road slope, the gearshift strategy based on power reserve is proposed. NEDC, FTP75 and full throttle acceleration performance simulation were carried out respectively based on optimal dynamic shift schedule, optimal economic shift schedule and the proposed optimal gearshift strategy. And the gearshift strategy based on power reserve was subsequently implemented to the target vehicle and tested for dynamic and economic performance evaluation. The simulation and real vehicle results show that the proposed optimal gearshift strategy can achieve the optimal tradeoff between the fuel economy and the drivability, which is adaptive to the vehicle dynamic characteristics. Overall, the optimal shift schedule based on DP shows good fuel economy and the test drivers were quite satisfied with the timing of the shifts as well as the overall drivability the designed shift schedule based on DP provided. It is also observed that if applying the concept of vehicle power demand in the design of optimal gearshift strategy, the vehicle fuel economy can be improved without sacrificing the vehicle drivability.
Lei, Yulong, Fu, Yao, Liu, Ke, Xingzhong, Li, Liu, Zhenjie, Zhang, Yin, Fu, Xuanyi
New Hybrid Genetic Algorithm for Pitch Sequence Optimization of CVT Variator Chain2017-01-11203/28/2017
A CVT variator chain system is superior in transmission efficiency to a belt system because of its lower internal friction. However, a chain produces more noise than a belt due to the long pitch length of contact between the pulleys and rocker pins. This study focuses on optimization of the pitch sequence for reducing chain noise. The previous pitch sequence was suitably combined of links of different lengths to improve noise dispersibility for reducing chain noise. First, the object function was defined as the reduction of the peak level of 1st-order chain noise combined with a well-balanced the levels on the low and high frequency sides. Interior background noise consisting of road noise and wind noise have the characteristic that they increase as the frequency decreases. Therefore, the object function was aimed at reducing the peak level of 1st-order chain noise by shifting the chain noise energy from the vicinity of the 1st-order band to the low frequency side in consideration of the masking effect of low-frequency background noise. Next, clustering clarified the characteristics of the pitch sequence design space as a multimodal space. Finally, “Hybrid genetic algorithm”, combining a genetic algorithm and local search was developed in order to search widely and deeply in the multimodal space for global optimal solutions. Hybrid-GA found global optimal solutions from a very large design space of 380 patterns. This pitch sequence was reduced the peak level of 1st-order chain noise by 2.8 dB compared with that of the previous pitch sequence.
Miyauchi, Arata, Tsutsumi, Kenji, Miura, Yoshitaka, Kageyama, Yusuke
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