Browse Topic: Slip

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Flight Test Evaluation of Center of Gravity Effects on a Coaxial Ultralight HelicopterF-0082-2026-02165/5/2026
This paper presents results of flight tests conducted on a coaxial ultralight helicopter. An automated flight test evaluation method is presented and exemplified through its application to steady horizontal flight. The results shown include pilot controls, helicopter attitude angles, power, thrust and torque distribution between the rotors, rotor harmonic thrust components, and teeter angles, along with their rotor harmonic components across varying flight speeds. This study focuses on the dependencies of these parameters on center of gravity position and sideslip angle.
Mindt, Maximilian, Gradkowski, Piotr, Matthia, Jonas, Mahlstedt, Dominik
CFD Based Interaction Modeling for Improving Rotorcraft AnalysisF-0081-2025-02105/20/2025
This paper introduces a comprehensive model, specifically developed to inherently capture interactional effects. Due to the high computational cost associated with the large analysis matrix including variations in angle of attack, angle of sideslip, velocity, and weight, a surrogate model is used in creating aerodynamic databases. This database, which reflects interactional effects under a wide range of flight speed, angle of attack, angle of sideslip, and weight configuration, is integrated into a rotorcraft analysis tool. Simulations are performed, and results are compared against flight test data for the T625 Gökbey, covering low-speed, high-speed, rightward and climb conditions. The results highlight the impact of interactional aerodynamics on flight characteristics and load predictions. Overall, the study emphasizes the importance of including interactional effects to ensure accurate and reliable rotorcraft design in the early design stages without requiring flight test data.
Erkan, Mehmet Ali, Madenci, Mustafa Alperen, Güngör, Osman, Şenipek, Murat, Ezertaş, Ahmet Alper
Aerodynamic investigation of a helicopter rotor hovering in the vicinity of a buildingF-0074-2018-126905/7/2024
ABSTRACT At the end of 2014, the Group for Aeronautical Research and Technology in EURope (GARTEUR) launched an action group (named AG22) in order to address both experimentally and numerically the issue of rotor wake interacting with obstacles. Within this group, several different experiments were set up and the results were provided to all the partners in order to compare and improve their numerical methods aimed at capturing interaction effects. In the present paper, we numerically investigate the experimental database provided by Politecnico di Milano (Polimi). A low fidelity method based on free wake approach and also CFD computations with different level of modeling are compared to experimental data. It shows that free wake approach is perfectly suitable to predict interaction effects on the rotor loads as long as there is no wake re-ingestion by the rotor. In other cases, the use of CFD is mandatory. However, computational cost can greatly be reduced using some approximation (no fuselage, immersed boundary method approach for the building, wall slip boundary condition on the ground) without significant loss in the rotor loads accuracy. Moreover, such approximation still gives acceptable results with regards to the effects of the rotor wake on the building itself and across the flowfield.
Boisard, Ronan
Flight Test Measurement of Quadrotor Performance at Varying Sideslip AnglesF-0078-2022-176425/10/2022
ABSTRACT
McCrink, Matthew, Seth,  Dhuree, Herz, Sage
Speed Limiter Using Disturbance Observer2021-01-01024/6/2021
This paper suggests disturbance observer which improves performance of speed limit assist control. The nonlinear disturbance observer was designed so that disturbance caused by parameter and load uncertainties is able to be estimated exponentially. With the contribution of the observer, feed-forward and integral controllers can be omitted while improving steady-state error elimination and overshoot reduction. The acceleration observer is also designed to reduce the effect of wheel slip and changing slope. The performance of the controllers has been verified not only on flat roads, but also on wave road and rapidly changing ramps.
Son, Huiun, Jo, Kyuhwan, Kim, Sangjoon, Cho, Jinkyeom, Jeon, Sungbae
Electronic Differential Control of Rear-Wheel Independent-Drive Electric Vehicle10-04-01-000412/2/2019
To track desired slip ratios and desired longitudinal speeds at the centers of driving wheels in the curve, this article proposes a hierarchical structured electronic differential control (EDC) of rear-wheel independent-drive electric vehicle (EV). In the high-level control, a fuzzy algorithm-based coefficient is computed according to the driver’s emotional intention of acceleration. The fuzzy algorithm-based coefficient is used to correct the desired driving torque of vehicle transmitting to the medium-level control. In the medium-level control, an optimization algorithm is developed to allocate the desired torques with requirement of as much accurate yaw moment as possible by the desired driving torque of the vehicle and yaw moment. And the desired longitudinal speeds at the centers of the rear left and right wheels are corrected twice, respectively, by Ackermann steering principle, considering the slip angle of the wheel and yaw moment. Based on the desired torques and desired longitudinal speeds at the centers of the rear left and right wheels from the medium-level control, desired slip ratios and desired angular speeds of the rear left and right wheels which are control signals for in-wheel-motor controllers are computed sequentially by adopting an inverse model of the Magic Formula. The square root of the sum of squares (SRSS) of tracking errors of the rear left and right wheel is adopted as the tracking error index of longitudinal speeds at the centers and slip ratios of the rear left and right wheels. In steering maneuvers of step steering and double lane change, simulation results based on MATLAB/Simulink indicate that the proposed EDC can improve tracking accuracy of longitudinal speeds at the centers and slip ratios of the rear left and right wheels compared with two EDCs for comparison. The two EDCs are an EDC based on Ackermann steering principle and an EDC based on the proposed EDC with the simplified desired longitudinal speed at the center of the wheel. The proposed EDC has better performance in tracking road trajectory, the desired vehicle longitudinal velocity and desired yaw rate compared. Finally, the robustness of the proposed EDC is verified under the slalom test.
He, Ren, Yun, Hang
Algorithm Gives Robots a Faster GraspTBMG-3561512/1/2019
A robot that's sorting through a bin of objects and attempting to get a good grasp on one of them is performing a computationally taxing maneuver. Before even attempting the move, it must calculate a litany of properties and probabilities such as the friction and geometry of the table, the pen, and its two fingers, and how various combinations of these properties interact mechanically based on fundamental laws of physics.
An Experimental Study to Evaluate the Droplet Impinging Erosion Characteristics of an Icephobic, Elastic Soft Surface2019-01-19976/10/2019
Elastic soft material/surface, such as Polydimethylsiloxane (PDMS), is a perspective, useful and low-cost hydrophobic and icephobic coating. While it has been reported to have good mechanical durability, its erosion durability under the high impacting of water droplets pertinent to aircraft inflight icing phenomena has not been explored. In this study, the droplet imping erosion characteristics of an icephobic PDMS surface/material is evaluated systematically upon the dynamic impinging of water droplets at different impact velocities (~ up to 75m/s), in comparison with other state-of-the-art icephobic materials/surfaces, such as superhydrophobic surface (SHS) and slippery liquid-infused porous surface (SLIPS). Surprisingly, the contact angle (CA) of the elastic PDMS is shown to have an over 20° increase (from 105° to 128°), which represents better hydrophobicity, after the erosion test which is mainly contributed to the higher roughness of the eroded PDMS surface. As for the icephobicity evaluation, intact PDMS was found to has ultra-low ice adhesion (~8 kPa), in comparison with SHS (i.e., ~100kPa) and SLIPS (i.e., ~35kPa). PDMS also shows outstandingly stable ice adhesion during the erosion test (i.e., fluctuation only within ~4kPa) as a result of the growth of cracks on the PDMS surface and the increased surface energy.
Ma, Liqun, Zhang, Zichen, Liu, Yang, Hu, Hui
A Novel Heating-Coating Hybrid Strategy for Wind Turbine Icing Mitigation2019-01-20296/10/2019
The electro-thermal method is most commonly used for wind turbine anti-/de-icing. The upmost drawback of such systems is the high power consumption. In the present study, we proposed to use a durable slippery liquid-infused porous surface (SLIPS) to effectively reduce the power requirement of the heating element during the anti-/de-icing process. The explorative study was conducted in the Icing Research Tunnel at Iowa State University (ISU-IRT) with a DU91-W2-250 wind turbine blade model exposed under severe icing conditions. During the experiments, while a high-speed imaging system was used to record the dynamic ice accretion process, an infrared (IR) thermal imaging system was also utilized to achieve the simultaneous surface temperature measurements over the test model. In comparison to the traditional electrical heating strategies to brutally heat massive area of entire turbine blades, a novel heating-coating hybrid strategy, i.e., combining a leading-edge (LE) heating element to cover the first 30% of the chord length (C) along with using SLIPS to coat entire blade surface, was found to be able to keep the entire blade surface completely free of ice, but with only an approximately 30% of the required energy consumption. The readily bouncing of the water droplets upon impinging onto the durable SLIPS and the much lower ice adhesion strength/capillary force over the SLIPS coated surface are believed to be the reasons to lead the better anti-/de-icing performance of the heating-coating hybrid strategy to prevent ice accretion/formation over the surfaces of the wind turbine blades.
Gao, Linyue, Ma, Liqun, Liu, Yang, Hu, Hui
An Experimental Investigation of a Wind-Driven Water Droplet over the Slippery Liquid Infused Porous Surface2019-01-19516/10/2019
The promising anti-icing performance of the slippery liquid infused porous surface (SLIPS) has been recently demonstrated for various engineering applications. The runback icing for aircraft and wind turbines could be effectively mitigated considering the timely removal of water droplet by the wind shearing force due to the low adhesion on the SLIPS. In this study, the flow field both inside and around the wind-driven droplet over the SLIPS was experimentally investigated by using Particle Image Velocimetry (PIV) technique. Previous studies majorly focus on the internal flow pattern before the droplet incipient motion. In this study, the flow field inside a moving droplet was firstly investigated. As a result of the low surface adhesion of the SLIPS, droplet oscillations were eliminated and the droplet internal flow field could be corrected from the optical distortion. Besides the discussion on the wind speed, the droplet viscosity was also studied by varying the water concentration of the glycerin-water solution. It was found that the internal circulation was highly related with the droplet viscosity. The inner circulations within the water droplet would be reduced, or eliminated, when the droplet viscosity was increased, which would change the droplet motion from sliding into rolling. It was suggested that the internal flow should be considered when theoretically modeling the wind-driven droplet movement over the SLIPS. This study could provide experimental evidence for a broader application of the SLIPS in the icing-related industrial world.
Ma, Liqun, Hu, Hui
Event Data Recorder Performance during High Speed Yaw Testing Subsequent to a Simulated Tire Tread Separation Event2019-01-06344/2/2019
This paper presents event data from the Sensing and Diagnostic Module (SDM) of a 2004 Chevrolet Malibu during high speed yaw testing. Yaw tests were performed using tires that were intact and tires that had the tread removed. The tires that had the tread removed were placed at various wheel positions on the vehicle (e.g. leading side - front, leading side -rear, trailing side - rear). This testing simulates the loss of control phase subsequent to a tread separation. Speeds up to 117 km/h (72.9 mph) were achieved. A simple electro-mechanical device was incorporated to the dynamic testing to simulate a low-severity non-deployment event that triggered the recording of pre-crash data by the SDM. The SDM data from the tests was imaged and compared to reference data from vehicle-mounted instrumentation recording wheel speed, steering angle, measured vehicle sideslip angle and GPS calculated over the ground speed. This paper examines the dynamic effect of high sideslip angles and changes to tire rolling radius, as a result of a tread separation, as it pertains to the accuracy of EDR reported vehicle speed.
Bortles, William, Koch, Daniel, Beauchamp, Gray, Pentecost, David, Rayburn, George, Hostetler, Ryan
Model-Based Approaches in Developing an Advanced Aftertreatment System: An Overview2019-01-00261/15/2019
Cummins has recently launched next-generation aftertreatment technology, the Single ModuleTM aftertreatment system, for medium-duty and heavy-duty engines used in on-highway and off-highway applications. Besides meeting EPA 2010+ and Euro VI regulations, the Single ModuleTM aftertreatment system offers 60% volume and 40% weight reductions compared to current aftertreatment systems. In this work, we present model-based approaches that were systematically adopted in the design and development of the Cummins Single ModuleTM aftertreatment system. Particularly, a variety of analytical and experimental component-level and system-level validation tools have been used to optimize DOC, DPF, SCR/ASC, as well as the DEF decomposition device. The highlights of this work can be summarized as follows: a). internal dosing is more efficient than external dosing to control HC slip; High CPSI DOCs show better HC oxidation performance at high SV due to enhanced mass transfer; b). the adopted advanced DPF technologies enable greater ash capacity for long maintenance intervals; c). SCR performance was optimized with the use of a hydrothermally robust Cu-Zeolite catalyst coated on high CPSI substrates.
Su, Changsheng, Brault, Joseph, Munnannur, Achuth, Liu, Z. Gerald, Milloy, Sean, Harinath, Arvind, Dunnuck, David, Federle, Ken
Boundary Layer Dynamics and Sound Generation2018-01-190010/5/2018
In recent years, characteristic structures in the boundary layer of high-load contacts such as brakes have been reported, which substantially influence the dynamics of the tribological contact. Usually, local assumptions concerning the friction behavior of these patches are used to reach global conclusions about the brake system. Several numerical methods (e.g. Cellular Automata) have been developed which employ such assumptions. The validation of these methods through measurement data tends to be laborious and costly. Sprag-Slip elements are friction elements that are exclusively subjected to static friction, never undergoing sliding friction. Implementing such elements on a mesoscopic scale, it is possible to generate global descriptions of macroscopic stick and slip friction phenomena. Locally, these Sprag-Slip elements are similar to the patch structures in the tribological boundary layer of brakes. The Sprag-Slip elements are suitable for describing the basic physics in the boundary layer between brake pad and rotor. Previous works have established their ability to depict principle macroscopic brake friction curves. In this paper, it is shown that characteristic boundary layer oscillations can represent characteristic braking behaviors, such as squealing and creep groan.
Recke, Bastian, Ostermeyer, Georg
GPS Enabled Semi-Autonomous RobotTBMG-289045/1/2018
The primary objective of this research is to integrate GPS and local sensory data to allow a robot to operate semi-autonomously outside of a laboratory environment. The Pioneer 3-AT, a robust platform capable of operating in the outdoors, is utilized in this project. The P3-AT has acoustic sensors that can calculate distances to obstacles and encoders that calculate how much each wheel has turned. In a laboratory environment, sensory and encoder information can be used to triangulate position or measure distance and direction traveled from a known starting point. Operating outdoors limits the effectiveness of both systems as the obstacles are not known and wheels can often slip and slide on different surfaces. This necessitates external data to determine the location of the robot. GPS was chosen to provide that data. GPS, acoustic, and encoder data were integrated within MATLAB and provided control signals to the robot.
Vehicle Sideslip Angle Estimation Considering the Tire Pneumatic Trail Variation2018-01-05714/3/2018
Vehicle sideslip angle is significant for electronic stability control devices and hard to estimate due to the nonlinear and uncertain vehicle and tire dynamics. In this paper, based on the two track vehicle dynamic model considering the tire pneumatic trail variation, the vehicle sideslip angle estimation method was proposed. First, the extra steering angle of each wheel caused by kinematics and compliance characteristics of the steering system and suspension system was analyzed. The steering angle estimation method was designed. Since the pneumatic trail would vary with different tire slip angle, distances between the center of gravity (COG) and front&rear axle also change with the tire slip angle. Then, based on the dynamic pneumatic trail and estimated steering angle, we modified the traditional two track vehicle dynamic model using a brush tire model. This model matches the vehicle dynamics more accurately. In addition, we designed two extended Kalman filters (EKF) based on the traditional two track vehicle dynamic model and modified two track vehicle dynamic model to estimate the vehicle sideslip angle. In the end, the extended Kalman filters were validated under simulations under multi-maneuvers in high friction road. The estimation results were compared with the actual sideslip angle which shows the accuracy of extended Kalman filter with modified two track dynamics model is higher than the extended Kalman filter with traditional two track dynamic model.
Xia, Xin, Xiong, Lu, Lin, Xuefeng, Yu, Zhuoping
Vehicle Sideslip Angle Estimation: A Review2018-01-05694/3/2018
Vehicle sideslip angle estimation is of great importance to the vehicle stability control as it could not be measured directly by ordinary vehicle-mounted sensors. As a result, researchers worldwide have carried out comprehensive research in estimating the vehicle sideslip angle. First, as the attitude would affect the acceleration information measured by the IMU directly, different kinds of vehicle attitude estimation methods with multi-sensor fusion are presented. Then, the estimation algorithms of the vehicle sideslip angle are classified into the following three aspects: kinematic model based method, dynamic model based method, and fusion method. The characteristics of different estimation algorithms are also discussed. Finally, the conclusion and development trend of the sideslip angle estimation are prospected.
Liu, Wei, Xiong, Lu, Xia, Xin, Yu, Zhuoping
A Computational and Experimental Investigation into the Effects of Debris on an Inverted Double Wing in Ground Effect2018-01-07264/3/2018
Cars in several motor sports series, such as Formula 1, make use of multi-element front wings to provide downforce. These wings also provide onset flows to other surfaces that generate downforce. These elements are highly loaded to maximise their performance and are generally operating close to stall. Rubber debris, often known as marbles, created from the high slip experienced by the soft compound tyres can become lodged in the multiple elements of a front wing. This will lead to a reduction in the effectiveness of the wing over the course of a race. This work will study the effect of such debris, both experimentally and numerically, on an inverted double element wing in ground effect at representative Reynolds numbers. The wing was mounted at two different ride heights above a fixed false-floor in the Loughborough University wind tunnel and the effect of debris blockage modelled by closing sections of the gap between elements with tape. The reduction in downforce compared to the clean wing was measured and the sensitivity to the size and position of the blockage studied. It was found that debris near the centre of the element has a greater impact. CFD simulations were also carried out that were able to correctly predict the trend of downforce with blockage position. The CFD was also used to computationally remove the effects of the tunnel. This confirmed the result seen in experiment that the blockage has more effect on a more highly loaded wing.
Corfield, Emma, Hodgson, Graham, Garmory, Andrew
Vehicle Stability Criterion Research Based on Phase Plane Method2017-01-15603/28/2017
In this paper, a novel method is proposed to establish the vehicle yaw stability criterion based on the sideslip angle-yaw rate (β-r) phase plane method. First, nonlinear two degrees of freedom vehicle analysis model is established by adopting the Magic Formula of nonlinear tire model. Then, according to the model in the Matlab/Simulink environment, the β-r phase plane is gained. Emphatically, the effects of different driving conditions (front wheels steering angle, road adhesion coefficient and speed) on the stability boundaries of the phase plane are analyzed. Through a large number of simulation analysis, results show that there are two types of phase plane: curve stability region and diamond stability region, and the judgment method of the vehicle stability domain type under different driving conditions is solved. Finally, different conditions of stability boundary plane database look-up tables are set up, besides, the effects of different conditions on the stability boundary’s relevant design parameters are investigated. This research provides a theoretical basis for the intervention of the stability control system algorithms.
Liu, Wei, Xiong, Lu, Leng, Bo, Meng, Haolan, Zhang, Renxie
A Hybrid Approach to Model the Temperature Effect in Tire Forces and Moments2017-01-96763/14/2017
Tire is an integral part of any vehicle which provides contact between the vehicle and the surface on which it moves. Forces and moments generated at the tire-road interaction imparts stability and control of motion to the vehicle. These forces and moments are functions of many variables such as slip, slip angle, contact pressure, inflation pressure, coefficient of friction, temperature, etc. This paper deals with the effect of temperature on the lateral force, the longitudinal force and the self-aligning moment. The analysis is done at different tire surface temperatures such as 20°C, 40°C, and 60°C. Since the experimental set up with the mounted tire is complex and expensive, we use a hybrid approach in which we take the results from the experiments done by the researchers on a sample piece of tire rubber at various temperatures. Then, we do the steady state analysis in ABAQUS considering the variation of coefficient of friction, slip speed and the elastic modulus of rubber with temperature. The steady state numerical results from ABAQUS at different surface temperatures are compared with the modified PAC2002 tire model to capture the temperature effect. After validating the variations of steady state forces and moments from ABAQUS with the modified PAC2002, we use these steady state tire models to do the transient analysis in order to capture the effect of temperature on the transient response of tire forces and moments for different driving conditions of acceleration, braking and double lane change using MSC ADAMS/CAR.
S, Bibin, Pandey, Ashok Kumar
NOx-Conversion and Activation Temperature of a SCR-Catalyst Whilst Using a Novel Biomimetic Flash-Boiling AdBlue Injector on a LD Engine2016-01-221210/17/2016
Yearly 3.3 million premature deaths occur worldwide due to air pollution and NOx pollution counts for nearly one seventh of those [1]. This makes exhaust after-treatment a very important research and has caused the permitted emission levels for NOx to decrease to very low levels, for EURO 6 only 0.4 g/kWh. Recently new legislation on ammonia slip with a limit of 10 ppm NH3 has been added [2], which makes the SCR-technology more challenging. This technology injects small droplets of an aqueous Urea solution into the stream of exhaust gases and through a catalytic reaction within the SCR-catalyst, NOx is converted into Nitrogen and Water. To enable the catalytic reaction the water content in the Urea solution needs to be evaporated and the ammonia molecules need to have sufficient time to mix with the gases prior to the catalyst. The μMist® platform technology, inspired by nature, uses heat in order to increase the fluid temperature above the required saturation temperature within its constant volume chamber. When the outlet valve is opened the liquid breaks up into small droplets which eject and mix with the gases. This paper presents an investigation on how these heated droplets with SMD around 20μm affect the catalytic conversion and achieve high conversion whilst the ammonia slip is kept to a minimum for a few different mass flows. Injected pre-heated small droplets shows over 95 % catalytic conversion of NOx at exhaust temperatures around 200°C. During continuous operation at catalyst temperatures around 350°C - 370°C several test points reaching from 0.7 kg/h to 1.1 kg/h of AdBlue mass flow, achieved EURO VI legislation at the selected experimental conditions, not included in the WHSC (World Harmonized Steady-State Cycle), for both NOx and ammonia with higher than 98 % conversion efficiency.
Larsson, Peter, Lennard, Will, Dahlstrom, Jessica, Andersson, Oivind, Tunestal, Per
A Droplet Size Investigation and Comparison Using a Novel Biomimetic Flash-Boiling Injector for AdBlue Injections2016-01-221110/17/2016
Increased research is being driven by the automotive industry facing challenges, requiring to comply with both current and future emissions legislation, and to lower the fuel consumption. The reason for this legislation is to restrict the harmful pollution which every year causes 3.3 million premature deaths worldwide [1]. One factor that causes this pollution is NOx emissions. NOx emission legislation has been reduced from 8 g/kWh (Euro I) down to 0.4 g/kWh (Euro VI) and recently new legislation for ammonia slip which increase the challenge of exhaust aftertreatment with a SCR system. In order to achieve a good NOx conversion together with a low slip of ammonia, small droplets of Urea solution needs to be injected which can be rapidly evaporated and mixed into the flow of exhaust gases. In most of today's solutions this process is enhanced with flow restricting mixers or longer path lengths but if these can be removed and shortened the flow losses can be reduced, leading to higher efficiency and lower fuel consumption as well as a more compact exhaust system. The μMist® injector, inspired by nature, takes the concept from the Bombardier beetle which induces flash-boiling in its effective defence mechanism by spraying a plume of hot poisonous fine droplets with great accuracy towards an attacker [3]. By heating up the fluid in a constant volume chamber above the saturation temperature and induce flash evaporation by opening the nozzle, the liquid breaks up into fine droplets which flow out into the target environment. This paper presents a study comparing the different effects of spray behaviour at different ratios between the saturation pressure and the target pressure. In this study the target pressure is atmospheric. The aim for the study is to gain a better understanding of the droplet sizes and the injector flow rates for different pressures and also present a limited benchmarking study of current market leading AdBlue injectors. Current testing has shown that this novel injector has the ability to produce 33% smaller droplets in SMD and 87% reduction in DV50.
Larsson, Peter, Lennard, Will, Andersson, Oivind, Tunestal, Per
Very-High Cycle Fatigue Testing Under Spectrum Loading for Endurance Limit Structural DesignF-0072-2016-115435/17/2016
A program has recently concluded that generated fatigue test data for the influence of a rotorcraft main rotor blade root bending spectrum (Helix) on the crack nucleation mechanisms in 7075-T651 aluminum. High frequency tests were performed that generated spectrum fatigue failures out to nearly 10⁹ cycles. Fractographic examination showed a distinct change in crack nucleation from slip initiated to inclusion initiated cracking as the spectrum peak stress level was increased. Spectrum life predictions were made using three different baseline constant-amplitude S-N curves, one using a traditional rotorcraft OEM fitting methodology, one using the HCF portion of a strain-life curve, and one that was fit to S-N data with test lives out to 3x10⁸ cycles. The spectrum life prediction using the S-N curve that properly modeled material behavior in the Very High-Cycle Fatigue (VHCF) regime provided a good correlation to the spectrum fatigue test data. Predictions using the other S-N curves were highly conservative.
Rusk, David, Taylor, Robert, Pregger, Bruce, Sanchez, Luis
CFD Analysis of Tail Surface Modifications and Rudder Deflection Influence on I-28B Gyroplane at High Angle of SideslipF-0072-2016-115905/17/2016
In the following work a set of CFD computational cases was calculated in order to obtain the aerodynamic characteristics of I-28 gyroplane in a wide range of sideslip angle. Severe modifications were checked out, and most important on the directional stability components of forces and moments, acting on an airframe, have been shown in aerodynamic coefficient form. A part of these calculations was to test the influence of rudder deflection on baseline gyroplane aerodynamic properties. In order to compare the results with already flying example of gyroplane, with known, good flight characteristics, a geometry was reconstructed with low accuracy, but enough to obtain reasonable sideslip characteristics, especially for high sideslip angle.
Dziubinski, Adam, Ulma, Dawid, Zurawski, Rafal
An Investigation Into New ABS Control Strategies2016-01-16394/5/2016
An investigation into two new control strategies for the vehicle Anti-lock Braking System (ABS) are made for a possible replacement of current non-optimal slip control methods. This paper applies two techniques in order to maximize the braking force without any wheel locking. The first considers the power dissipated by the brake actuator. This power method does not use slip to construct its reference signal for control. A heuristic approach is taken with this algorithm where one searches for the maximum power dissipated. This can open up easier implementation of regenerative braking concurrently with ABS on an electro-hydraulic braking system. Parameter scheduling is explored in this algorithm. The second algorithm employs the use of perturbation based Extremum Seeking Control (ESC) to provide a reference slip and a Youla controller in a negative feedback loop.
Loyola, Jonathan, Assadian, Francis
Fatigue Time-to-Failure Prediction Methodology for Glass (Fused Quartz) Material under Cyclic Loading2016-01-03884/5/2016
In amorphous solids such as fused quartz, the failure mechanism under cyclic loading is very different when compared to metals where this failure is attributable to dislocation movement and eventual slip band activity. Standard mechanical fatigue prediction methodologies, S-N or ε-N based, which have been historically developed for metals are rendered inapplicable for this class of material. The fatigue strength of Fused Silica or Fused Quartz (SiO2) material is known to be highly dependent on the stressed area and the surface finish. Stable crack growth in Region II of the V-K curve (Crack growth rate vs Stress intensity factor) is dependent on the competing and transitional effects of temperature and humidity, along that specific section of the stress intensity factor abscissa. Fused glass (under harsh environment conditions) finds usage in Automotive, Marine and Aerospace applications, where stress and load (both static and cyclic) can be severe. In the present work we have developed a six-step systematic approach for the probabilistic design of glass under dynamic loads. Specifically, ultraviolet irradiation reactor tubes, made of fused quartz and used to treat water, are used to demonstrate application of our methodology, and illustrate the challenges involved in the design of brittle material versus fatigue failure. Our methodology uses (1) a Weibull 2-parameter model, including the area scaling principle, (2) the shape parameter, which is essentially independent of the stressed area as well as the surface finish; and (3) the characteristic strength (based on 1cm2 uniformly stressed area). Significant variability is observed in the published material data. Monte-Carlo simulations were performed to account for experimental variability in the time-to-failure predictions.
Pandey, Abhijeet, Singhal, Mohit Kr., Kovacich, John, Rau, Christopher
Modeling of Transient Aerodynamic Forces based on Crosswind Test2016-01-15774/5/2016
The aerodynamic stability of energy-saving, lightweight, and low-drag vehicles is reduced by crosswind disturbances. In particular, crosswinds cause unsteady motion in vehicles with low-drag body shapes due to aerodynamic yaw moment. To verify fluctuations in the unsteady aerodynamic forces of a vehicle, a direct measurement method of these forces in a crosswind test was established using inertial force and tire load data. The former uses an inertia sensor comprised of a gyro, acceleration sensor, and GPS sensor, and the latter uses a wheel force sensor. Noise in the measurement data caused by the natural frequency of the tires was reduced using a spectral subtraction method. It was confirmed that aerodynamic data measured in the crosswind test corresponded to wind tunnel test data. Numerical expressions were defined to model the unsteady aerodynamic forces in a crosswind. Crosswind tests were conducted under various conditions consisting of different wind patterns and test vehicle yawing motions, to identify the model parameters in the numerical expressions by multiple linear regression analysis. The analysis results showed that dynamic aerodynamic forces can be expressed as a function of yaw rate, side slip angle, the derivative of the relative wind angle, and the relative wind angle, i.e. aerodynamic side slip angle. The transient state in a crosswind can be estimated by the proposed transient aerodynamic model more accurately than the previous static aerodynamic model. Furthermore, it was found that the dynamic aerodynamic force increases yaw rate due to crosswind disturbance, thereby deteriorating the stability of road vehicles.
Fukagawa, Tateru, Shimokawa, Shinnosuke, Itakura, Eiji, Nakatani, Hiroyuki, Kitahama, Kenichi
Analysis of Influence of Tire F and M on Improvement of Vehicle On-Center Steering2016-01-15694/5/2016
In this research, the influence of tire force and moment (F&M) characteristics on vehicle on-center steering performance was analyzed and then how to improve vehicle on-center performance was studied through controlling tire structure design parameter, tread pattern shape and tread grip characteristics. First, the relationship between vehicle on-center steering performance and tire F&M characteristics was identified by comparing vehicle steering measurements and tire F&M measurements. It was found that key factor of tire related with on-center performance is aligning torque at lower slip angles. As the aligning torque at slip angle 1° increases, on-center feel is improved. Second, the influence of tire design parameters on tire aligning torque was studied through F&M finite element (FE) analysis and measurement. It was found that the aligning torque at lower slip angle increases as stiffness of the tread and sidewall decreases. However, it shows trade-off with tire cornering force stiffness. It is necessary to optimize cornering force stiffness and aligning torque stiffness in tire structural design. In addition, as tread contact area to ground and viscosity of tread compound increase, both cornering force and aligning torque at lower slip angles increase together. Finally on-center steering performance of an Europe mid-size wagon was improved by increasing tire aligning torque at lower slip angle based on these research results.
Yum, Kiho
Sideslip Angle Estimation of a Formula SAE Racing Vehicle2016-01-16624/5/2016
A method for estimating the sideslip angle of a Formula SAE vehicle with torque vectoring is presented. Torque vectoring introduces large tire longitudinal forces which lead to a reduction of the tire lateral forces. A novel tire model is utilized to represent this reduction of the lateral forces. The estimation is realized using an extended Kalman filter which takes in standard sensor measurements. The developed algorithm is tested by simulating slalom and figure eight maneuvers on a validated VI-CarRealTime vehicle model. Results indicate that the algorithm is able to estimate the sideslip angle of the vehicle reliably on a high friction surface track.
Ghosh, Jyotishman, Tonoli, Andrea, Amati, Nicola, Chen, Weitao
The Roles of Front and Rear Cornering Stiffness in Vehicle Directional Dynamics2016-01-16514/5/2016
The transfer functions between the variables in linear bicycle models of four wheel automobiles, the input to which is steering angle, were examined. The modal response transfer functions between all of the motion outputs, with the exception of front tire slip angle, were found to be independent of front tire cornering stiffness. It is a role unique to rear cornering stiffness to define the above mentioned transfer functions. This concept was also deductively demonstrated. The concept is true in the frequency domain, therefore, it guarantees that the amplitude ratio between two outputs and the phase difference between two outputs depends only on rear cornering stiffness. However, it is necessary to be cautious, when one applies the concept to phenomena in time domain. For example, the difference in 50 % rise time of two output variables is dependent on front tire cornering stiffness.
Minakawa, Masaaki
Effect of Three Controls (Camber Angle Control, Derivative Steering Assistance Control, and Inside-Outside Wheel Braking Force and Driving Force Control in Body Slip Angle Area2016-01-16664/5/2016
In this research, we examine the three controls inside-outside wheel braking force and driving force, camber angle, and the derivative steering assistance to determine how angle differences affect cornering performance and controllability. This is accomplished by comparing body slip angle area differences in a closed loop examination of the grip to drift area using a driving simulator. The results show that inside-outside wheel braking force and driving force control in the area just before critical cornering occurs has a significant effect on vehicle stability. We also clarified that controlling the camber angle enhances grip-cornering force, and confirmed that the sideslip limit could be improved in the vicinity of the critical cornering area. Additionally, when the counter steer response was improved by the use of derivative steering assistance control in the drift area exceeding the critical cornering limit, corrective steering became easier. Moreover, the effect could be achieved by using camber angle and derivative steering assistance controls in combination over a wide area. Based on the above, we conclude that it is possible to control wide-ranging body slip angle areas by combining the three abovementioned controls.
Yamaguchi, Ryo, Nozaki, Hiromichi
Aerodynamics Evaluation of Road Vehicles in Dynamic Maneuvering2016-01-16184/5/2016
A road vehicle’s cornering motion is known to be a compound motion composed mainly of forward, sideslip and yaw motions. But little is known about the aerodynamics of cornering because little study has been conducted in this field. By clarifying and understanding a vehicle’s aerodynamic characteristics during cornering, a vehicle’s maneuvering stability during high-speed driving can be aerodynamically improved. Therefore, in this study, the aerodynamic characteristics of a vehicle’s cornering motion, i.e. the compound motion of forward, sideslip and yaw motions, were investigated. We also considered proposing an aerodynamics evaluation method for vehicles in dynamic maneuvering. Firstly, we decomposed cornering motion into yaw and sideslip motions. Then, we assumed that the aerodynamic side force and yaw moment of a cornering motion could be expressed by superposing linear expressions of yaw motion parameters and those of sideslip motion parameters, respectively. Next, we conducted CFD analyses of a vehicle in dynamic meandering motions. Then, we verified the linear aerodynamic force model with the CFD analysis results. The results revealed that the aerodynamic side force and yaw moment in dynamic meandering motion could be mostly expressed with the linear aerodynamic force model. We also clarified the aerodynamic characteristics of the vehicle in dynamic meandering motion and its generation mechanism by analyzing the surface static pressure distribution on the vehicle in dynamic meandering motion by applying the concept of the linear aerodynamic force model.
Okada, Yoshihiro, Nakashima, Takuji, Tsubokura, Makoto, Morikawa, Yousuke, Kouno, Ryousuke, Okamoto, Satoshi, Matsuhiro, Tanaka, Nouzawa, Takahide
Post-Impact Dynamics for Vehicles with a High Yaw Velocity2016-01-14704/5/2016
Calculating the speed of a yawing and braked vehicle often requires an estimate of the vehicle deceleration. During a steering induced yaw, the rotational velocity of the vehicle will typically be small enough that it will not make up a significant portion of the vehicle’s energy. However, when a yaw is impact induced and the resulting yaw velocity is high, the rotational component of the vehicle’s kinetic energy can be significant relative to the translational component. In such cases, the rotational velocity can have a meaningful effect on the deceleration, since there is additional energy that needs dissipated and since the vehicle tires can travel a substantially different distance than the vehicle center of gravity. In addition to the effects of rotational energy on the deceleration, high yaw velocities can also cause steering angles to develop at the front tires. This too can affect the deceleration since it will influence the slip angles at the front tires. This paper explores the influence of high rotational energies and impact induced steering on the deceleration experienced by a vehicle following an impact.
Rose, Nathan A., Carter, Neal, Beauchamp, Gray
New Slip Ring System for Electromagnetic Coupling in HEV Driveline2016-01-12224/5/2016
This paper describes the slip ring system for a new hybrid system using an electromagnetic torque converter or an electromagnetic coupling. The slip ring system, which enables electric power transmission between a winding rotor and an inverter fixed on a case, is a key component for establishing a new highly efficient hybrid system. Reducing the wear of the brushes in the slip ring system is a major topic of this research. To achieve this objective, brush wear characteristics were investigated using test-piece experiments that simulated the hybrid system environment. By clarifying these characteristics, the structure of a slip ring system for reducing brush wear was identified and a wear prediction method was constructed.
Asami, Shu, Watanabe, Takao, Tominaga, Satoshi, Murakami, Akira
Determination of Critical Speed, Slip Angle and Longitudinal Wheel Slip based on Yaw Marks Left by a Wheel with Zero Tire Pressure2016-01-14804/5/2016
This article presents the results of an analysis of the yaw marks left by a car with normal pressure in all tires and then normal pressure in three tires and zero in one rear tire. The analysis is a continuation of research on influence of reduced tire pressure on car lateral dynamics in a passing maneuver, discussed in the SAE paper No. 2014-01-0466. Preliminary analysis of yaw marks has shown, that a wheel with zero pressure deposits a yaw mark whose geometry differs from the yaw mark made by a wheel with normal pressure based on which we could calculate: critical speed, slip angle and longitudinal wheel slip. The aim of the presented research was to analyze the yaw marks left by car with zero pressure in one rear wheel in order to check the possibility of determining the vehicle critical speed, slip angle and longitudinal wheel slip. It was reached by performing bench and road tests during which the vehicle motion parameters were recorded using GPS Data Logging System. The results of calculations based on the geometric characteristics of yaw marks were compared with real values obtained from the measurements of vehicle motion parameters.
Zebala, Jakub, Wach, Wojciech, Ciępka, Piotr, Janczur, Robert
Vehicle Side Slip and Roll Angle Estimation2016-01-16544/5/2016
Vehicle dynamics estimation has been the subject of study for some years now. If on-board vehicle control systems can be provided with information such as side slip angle, lateral force etc. then stability of the vehicle can be improved. To estimate these dynamic variables different observers have been used e.g., sliding mode, fuzzy logic, neural networks etc. In this article the authors propose an extended Kalman filter to estimate vehicle side slip angle. Roll angle is estimated using vertical loads as input. First, a linear Kalman filter is used to filter out the vertical forces and estimate roll angle. This information is then used to estimate the vehicle side slip angle. To take into account the nonlinearities concerning lateral vehicle dynamics, Pacejka magic formula is used to model lateral forces. Estimated results are then compared with simulations, showing good accuracy.
Syed, Umair Hussain, Vigliani, Alessandro
Effect of Humidity on the Very High Cycle Fatigue Behavior of a Cast Aluminum Alloy2016-01-03714/5/2016
In this paper, fatigue tests on a cast aluminum alloy (AS7GU-T64) were performed under different frequencies and humidity levels. Tests conducted under conventional frequency in laboratory air have been compared to tests conducted under ultrasonic frequency in dry air, saturated humidity and in distilled water. It was observed that the highest and lowest fatigue lives correspond to ultrasonic fatigue tests in dry air and in distilled water, respectively. Unlike specimens tested at conventional frequency, all of the specimens tested at ultrasonic frequency presented a large amount of slip facets on the fatigue crack propagation fracture surface.
Li, Wenkai, Engler-Pinto, Carlos, Cui, Haitao, Wen, Weidong, Su, Xuming
Experimental Evaluation of Surface Morphology Characteristics During Stick-Slip Process at Low Speed Sliding Test2015-01-26859/27/2015
The present work presents evaluation of the sliding surface morphology of brake pads during stick-slip. A low-metallic (LM) and a Non Asbestos Organic (NAO) brake friction materials were subjected to slide against a brake disc under conditions favorable to produce stick-slip phenomenon. The experiments were conducted in a laboratory-scale tribometer, which was especially designed to test brake pads used in vehicle. Delta torque divided by slip time (dT/dtslip) was the parameter used to quantify stick-slip propensity. In addition, optical microscope images of the material's surface were obtained at different stages of the braking test. These images were post-processed in appropriate computational software and by means of the segmentation technique, the real contact area, size and amount of contact plateaus related to the brake pad surface were estimated. This technique was effective to quantify the differences in the sliding surface morphology during low speed braking test. Finally, some trends related to the surface morphology of the brake pads selected in this study are shown as well as the relationship between both the material stick-slip behavior and morphological parameters is established and discussed.
Masotti, Diego, Neis, Patric, Ferreira, Ney, Gomes, Kássio, Poletto, Jean, Matozo, Luciano
A New Semi-Empirical Method for Estimating Tire Combined Slip Forces and Moments during Handling Maneuvers2015-01-91127/1/2015
Modeling the tire forces and moments (F&M) generation, during combined slip maneuvers, which involves cornering and braking/driving at the same time, is essential for the predictive vehicle performance analysis. In this study, a new semi-empirical method is introduced to estimate the tire combined slip F&M characteristics based on flat belt testing machine measurement data. This model is intended to be used in the virtual tire design optimization process. Therefore, it should include high accuracy, ease of parameterization, and fast computational time. Regression is used to convert measured F&M into pure slip multi-dimensional interpolant functions modified by weighting functions. Accurate combined slip F&M predictions are created by modifying pure slip F&M with empirically determined shape functions. Transient effects are reproduced using standard relaxation length equations. The model calculates F&M at the center of the contact patch. The developed methodology is implemented as an external tire module for the vehicle simulation software CarSim. The validation studies are conducted using the data sets from a flat belt testing machine and outdoor handling tests. The model demonstrated a high correlation with experimental results, while featuring an improved performance in parameterization and F&M estimation routines, compared to the commercially available Magic Formula tire model.
Taheri, Shahyar, Wei, Terence
Study of Stick-Slip Friction between Plunging Driveline2015-01-21716/15/2015
Driveline plunge mechanism dynamics has a significant contribution to the driver's perceivable transient NVH error states and to the transmission shift quality. As it accounts for the pitch or roll movements of the front powerplant and rear drive unit, the plunging joints exhibit resisting force in the fore-aft direction under various driveline torque levels. This paper tackles the difficult task of quantifying the coefficient of static friction and the coefficient of dynamic friction in a simple to use metric as it performs in the vehicle. The comparison of the dynamic friction to the static friction allows for the detection of the occurrence of stick-slip in the slip mechanism; which enables for immediate determination of the performance of the design parameters such as spline geometry, mating parts fit and finish, and lubrication. It also provides a simple format to compare a variety of designs available to the automotive design engineer.
Spencer, Winston, Bouzit, Djamel, Pace, Joseph, Dhillon, Sudeep
FITTING END, ACORN SHORT FLARELESS, DESIGN STANDARD, METRICMA2076A (Current)4/24/2015
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
FITTING END, ACORN FLARELESS DESIGN STANDARD, METRICMA2014A (Current)4/24/2015
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Induction Mode Operation in the Electrical Machine with DC Stator Excitation2015-01-01514/14/2015
The purpose of this paper is to investigate opportunity to create a new type AC induction motor with the salient pole rotor (without winding) and both winding AC excitation and short circuited placed on the stator. There are some advantages in this design: The suggested design has a cold rotor. The stator short circuited and excitation windings are easier for cooling. The rotor has reduced weight in compare with regular induction motor rotor. The short circuit winding can be used for the current control like in the regular induction wound-rotor machines. In this case, the problem maintenance of the slip rings is eliminated. In this paper, we discuss theoretical opportunity for realization the induction mode operation in two and three phase machines. As a base for this, it serves the analyses operation of one phase machine. This analysis is fulfilled in comparison with regular induction motors with short circuited and wound-rotor windings. Experimental verification was fulfilled in specially designed one phase machine, two phase and three phase machines. Design two and three phase machine demands use two windings for each phase like in regular induction machines. The results of this paper in connection with our previous publications shows that it is possible to design all type of traditional AC and DC machines on base of the salient pole rotor (without winding) and all winding placed on the stator.
Gladyshev, Sergey P., Okrainskaya, Irina, Gladyshev, Pavel
In-Tyre Sensors Induced Benefits on Sideslip Angle and Friction Coefficient Estimation2015-01-15104/14/2015
Aim of this study is to analyze the benefits of the measures provided by smart tyres on tyre-road friction coefficient and vehicle sideslip angle estimation. In particular, a smart tyre constituted by 2 tri-axial accelerometers glued on the tyre inner liner is considered which is able to provide the measures of the tyre-road contact forces once per wheel turn. These measures are added to the ones usually present onboard vehicle (steer angle, lateral acceleration and yaw rate) and following included into an Extended Kalman Filter (EKF) based on a single-track vehicle model. Performance of the proposed observer is evaluated on a series of handling maneuvers and its robustness to road bank angle, tyre and vehicle parameters variation is discussed.
Sabbioni, Edoardo, Ivone, Davide, Braghin, Francesco, Cheli, Federico
Methods of Test for Balanced Value and Control over Balance Continuity in Automobile ABS when ε=12015-01-06574/14/2015
This innovation is a Developed Anti-Lock Brake System (DABS for short) to automatically and precisely identify, correct and verify the peak-value slip ratio S0″ (i.e. braking force = adhesion force) when ε (namely the utilization ratio of adhesion coefficient, which is defined as the quotient of maximum braking strength divided by adhesion coefficient when ABS works) =1, and control S0″ to output continuously. It is a revision on the theory, method and algorithm of current ABS control that intermittently produces S0″. The aim is to eliminate the security risks of sideslip or ε<1 due to excessive or insufficient braking force, simplify structure, reduce cost, and improve the eligibility from ε≥0.75 to ε≥0.95.
Tu, Binglu, Shen, Kai
Study on Vehicle Stability Control by Using Model Predictive Controller and Tire-road Force Robust Optimal Allocation2015-01-15804/14/2015
The vehicle chassis integrated control system can improve the stability of vehicles under extreme conditions using tire force allocation algorithm, in which, the nonlinearity and uncertainty of tire-road contact condition need to be taken into consideration. Thus, An MPC (Model Predictive Control) controller is designed to obtain the additional steering angle and the additional yaw moment. By using a robust optimal allocation algorithm, the additional yaw moment is allocated to the slip ratios of four wheels. An SMC (Sliding-Mode Control) controller is designed to maintain the desired slip ratio of each wheel. Finally, the control performance is verified in MATLAB-CarSim co-simulation environment with open-loop manoeuvers.
Dengbo, He, Hui, Lu, Fan, Yu
Friction Estimation at Tire-Ground Contact2015-01-15944/14/2015
The friction estimation at the tire-ground contact is crucial for the active safety of vehicles. Friction estimation is a key problem of vehicle dynamics and the ultimate solution is still unknown. However the proposed approach, based on a simple idea and on a simple hardware, provides an actual solution. The idea is to compare the tire characteristic at a given friction (nominal characteristic) with the actual characteristic that the tire has while running. The comparison among these two characteristics (the nominal one and the actual one) gives the desired friction coefficient. The friction coefficient is expressed in vector form and a number of running parameters are identified. The mentioned comparison is an efficient but complex algorithm based on a mathematical formulation of the tire characteristic. The actual tire characteristic is somehow measured in real time by a relatively simple smart wheel which is able to detect the three forces and the three moments acting at the hub. A Gough-plot is derived to map the measured lateral tire force and self-aligning moment to a unique estimate of the lateral friction coefficient. Extending the Gough-plot by the (measured) longitudinal tire force due to longitudinal slip from braking or accelerating, makes the estimation method more robust. A look-up table is computed offline and allows for instantaneous friction estimation. The longitudinal friction coefficient is estimated in a similar way, making explicitly use of the longitudinal slip. Alternatively, measured tire forces and moments can be used for robust longitudinal slip estimation as well. Both the theoretical and experimental issues are presented in the paper.
Edelmann, Johannes, Gobbi, Massimiliano, Mastinu, Giampiero, Ploechl, Manfred, Previati, Giorgio
New Slip Control System Considering Actuator Dynamics2015-01-06564/14/2015
A new control strategy for wheel slip control, considering the complete dynamics of the electro-hydraulic brake (EHB) system, is developed and experimentally validated in Cranfield University's HiL system. The control system is based on closed loop shaping Youla-parameterization method. The plant model is linearized about the nominal operating point, a Youla parameter is defined for all stabilizing feedback controller and control performance is achieved by employing closed loop shaping technique. The stability and performance of the controller are investigated in frequency and time domain, and verified by experiments using real EHB smart actuator fitted into the HiL system with driver in the loop.
Soltani, Amir, Assadian, Francis
Integrated Longitudinal Vehicle Dynamics Control with Tire/Road Friction Estimation2015-01-06454/14/2015
The longitudinal dynamics control is an essential task of vehicle dynamics control. In present, it is usually applied by adjusting the slip ratio of driving wheels to achieve satisfactory performances both in stability and accelerating ability. In order to improve its performances, the coordination of different subsystems such as engine, transmission and braking system has to be considered. In addition, the proposed algorithms usually adopt the threshold methods based on less road condition information for simpleness and quick response, which cannot achieve optimal performance on various road conditions. In this paper, an integrated longitudinal vehicle dynamics control algorithm with tire/road friction estimation was proposed. First, a road identification algorithm was designed to estimate tire forces of driving wheels and the friction coefficient by the method of Kalman Filter and Recursive Least Squares (RLS). Then, a rule based integrated control algorithm which coordinate the engine torque control, brake pressure control and transmission shifting control was built to improve the vehicle driving performance. During the longitudinal dynamics control procedure, the transmission shifting control algorithm firstly decided whether the vehicle starting up at the 1st or the 2nd gear based on the road condition. Then, the engine torque control algorithm was applied to adjust the slip ratio of driving wheels. Its process was divided into three phases. In each phase, different control rules with integration of engine torque and brake torque were set by the combined feed forward and feedback methods to meet with requirements of accuracy, rapidity and stability. The brake pressure was determined by method of sliding mode control (SMC) for its rapid adjustment characteristic, in the meanwhile, it was also an important component to be considered in engine torque feedback control. Finally, the algorithm was verified by using Matlab/Simulink and CarSim co-simulation, the results show that the proposed control algorithm could regulate slip ratios of driving wheels fast and accurately, and the vehicle driving performance could be improved effectively.
Zhao, Jian, Zhang, Jin, Zhu, Bing
Prediction of Friction Drive Limit of Metal V-Belt2015-01-11384/14/2015
When fluctuations in the speed of rotation of the drive pulley are transmitted to the driven pulley via the metal V-belt, the transmitted fluctuations become attenuated as friction force approaches a state of saturation. The research discussed in this paper focused on these fluctuations in the speed of rotation and developed an index for the slip state between the belt and the pulleys. The drive and driven pulleys were regarded as a one-dimensional vibrating system connected by elastic bodies, and changes in the state matrix of the system were focused on. It was determined that when all of the eigenvalues in this state matrix become real numbers, slip speed between the belt and the pulleys increases sharply. A method was proposed of estimating this behavior of the eigenvalues from changes in the speed of rotation of the drive and driven pulleys, and indexing the current slip state. Torque fluctuations reproducing the fluctuations produced by an engine were input to the drive pulley, and pulley thrust was gradually reduced in order to measure changes in slip speed. The friction drive limit found using the proposed method matched the point of increase in slip speed and the point of maximum power transmission efficiency as obtained from measurements, verifying the effectiveness of the method. Using the proposed method, it is possible to predict the friction drive limit, a parameter that is strongly affected by individual differences between parts and age-related changes, and this will contribute significantly to the optimization of pulley thrust.
Sakagami, Kyohei
TWC+LNT/SCR Systems for Satisfying Tier 2, Bin 2 Emission Standards on Lean-Burn Gasoline Engines2015-01-10064/14/2015
A laboratory study was performed to assess the potential capability of TWC+LNT/SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. It was assumed that the exhaust system would need a close-coupled (CC) TWC, an underbody (U/B) TWC, and a third U/B LNT/SCR converter to satisfy the emission standards on the FTP and US06 tests while allowing lean operation for improved fuel economy during select driving conditions. Target levels for HC, CO, and NOx during lean/rich cycling were established. Sizing studies were performed to determine the minimum LNT/SCR volume needed to satisfy the NOx target. The ability of the TWC to oxidize the HC during rich operation through steam reforming was crucial for satisfying the HC target. Temperature studies indicated that the CC TWC needed to operate at a minimum of 500°C to provide good steam reforming activity, while the LNT/SCR needed to operate between 300 and 350°C to satisfy the NOx slip target while minimizing the slip of NH3, N2O, and HC during the purges. Sulfur poisoning increased the HC slip by degrading the steam reforming reaction, and the sulfur increased the NOx slip by decreasing the NOx storage capacity of the LNT. Both the TWC and LNT/SCR could be desulfated with rich exhaust at 700°C. However, it was projected that the ability to obtain 700°C at the underbody LNT/SCR location would be difficult without additional exhaust hardware, such as fuel injectors or air pumps. Consequently, development of the LNT/SCR system was terminated in favor of a passive TWC+SCR approach because of its superior sulfur tolerance. Investigations into the passive TWC+SCR approach are discussed in a companion SAE paper.
Theis, Joseph R., Kim, Jeong, Cavataio, Giovanni
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