ABSTRACT The aerodynamic interaction between rotor wake and surrounding obstacles is complex, and generates high compensatory workload for pilots, degradation of the vehicle handling qualities and performance, and unsteady forces on the structure of the obstacles. The interaction also affects the minimum distance between rotorcraft and obstacles to operate safely. A vortex-based approach is here employed to investigate the complex aerodynamic interaction between rotors and ground obstacles and identify the distance where the interaction ends. This is also one of the objectives of the GARTEUR AG22 effort. In this approach, the aerodynamic loads of the rotor blades are described through a panel method, and the unsteady behavior of the rotor wake is modelled using a vortex particle method. The effects of the ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to "Large" and "Wee" rotor near the ground and obstacle and compared with earlier experiments carried out at the University of Glasgow. The results show that the predicted rotor induced inflow, and flow-field compare reasonably well with the experiments in terms of magnitude and phase, for the peaks of the radial outwash and vertical downwash. Furthermore, at certain conditions the tip vortices are pushed upwards and are re-ingested into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover, contrary to cases without the obstacle, the peak and thickness of the radial outwash near the obstacle is lower due to blockage effects, and an up-wash is observed. Additionally, as the rotor closes to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the up-wash near the obstacle is faster, indicating a stronger interaction between the rotor wake and the obstacle. Also, contrary to the case without the obstacle, the fluctuations of the rotor thrust, roll and pitch moments are obviously strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the obstacle is small.

Tan, Jianfeng, Barakos, George, Sun, Yiming, Zhou, Tianyi, Green, Richard

Research on the Dynamic Integration Control for Distributed-Traction Electric Vehicle with Four-Wheel-Distributed Steering System

2018-01-08144/3/2018

With rapid development of the automobile industry and the growing maturity of the automotive electronic technologies, the distributed-traction electric vehicle with four-wheel-distributed steering/braking/traction systems is regarded as an important development direction. With its unique chassis structure, it is the ideal benchmark platform used to evaluate active safety systems. The distributed-traction electric vehicle with four-wheel-distributed steering system is essentially full drive-by-wire vehicle. With its flexible chassis layout and high control degrees-of-freedom, the full drive-by-wire electric vehicle acted as a kind of redundant system is an ideal platform for the research of integrated control. In this treatise, the longitudinal dynamics of the electric vehicle as well as its lateral and yaw motions are controlled simultaneously. In the motion control layer, the total force and total torque of the vehicle motion control are obtained by using the sliding mode controller, and the elimination of chatter is achieved by using the terminal sliding mode control technique for the yaw motion control. In the tire force allocation layer, the axial load transfer issue is taking into consideration during the process of tire force distribution, and then, the optimal allocation problem is transformed into a quadratic programming issue with constraint. In the executive layer, the target tire force output from the tire force allocation layer are ultimately achieved by controlling the drive/braking torque of the wheel motor and the steering angle of steering motor. The results demonstrate the effectiveness of the designed controller and it is shown via the co-simulation that the proposed control algorithm can coordinating with drive and steering system better, in which the electric vehicle can track the target vehicle and ideal yaw rate.

Wang, Jiantao, Zong, Changfu, Zheng, Hongyu, liu, Chen, Cheng, Cheng

Parameters Analysis of on-Center Handling for Articulated Trucks

2018-01-01364/3/2018

On-center handling is one of the most important test conditions which are used to evaluate the handling performance of both passenger cars and commercial vehicles. This paper aims at investigating and verifying the influence of parameters on on-center handling of articulated trucks. A full vehicle model, including the steering system, suspension system, cab, frame, trailer and so on, was established in first by measuring the parameters of each component. The comparison of simulation and test results shown that the simulation precision of the vehicle model was up to 80%. Based on the model, the influence analysis of parameters, such as stiffness of steering drag link, steering ratio, kingpin friction, were carried out and were verified through the handling test. The analysis results indicated that larger stiffness of steering drag link, smaller gear ratio could enhance the steer sensitivity and steer stiffness, small kingpin friction is beneficial to the steering return ability.

Jiang, Xuefeng, Liu, Xiang, Chen, Wei, xie, hao, Sun, Zhe

Dynamic Characteristics Analysis of an Ambulance with Hydraulically Interconnected Suspension System

2018-01-08154/3/2018

The vibration and instability experienced in an ambulance can lead to secondary injury to a patient and discourage a paramedic from emergency care. This paper presents a hydraulically interconnected suspension (HIS) system which can achieve enhanced cooperative control of roll, pitch and bounce motion modes to improve the ambulance's ride comfort and handling performance. A lumped-mass model integrated with a mechanical and hydraulic coupled system is developed by using free-body diagram and transfer matrix methods. The mechanical-fluid boundary condition in the double-acting cylinders is modelled as an external force on the mechanical system and a moving boundary on the fluid system. A special modal analysis method is employed to reveal the vibration characteristics of the ambulance with the HIS. A series of frequency analyses, including free vibration with identified eigenvalues and eigenvectors, vibration transmissibility and force vibration with stochastic road inputs, are performed to evaluate the vehicular performance between an ambulance with a conventional suspension and one with the HIS. The results show that the proposed HIS system is able to reduce the roll and pitch motion of sprung mass to improve the handling stability, meanwhile provide softer bounce stiffness to maintain the ride comfort. Furthermore, the vibration decay rate of sprung mass is significantly increased.

Tan, Bohuan, Wu, Yang, Zhang, Nong, Zhang, Bangji, Zheng, Minyi, Qi, Hengmin

Handling Improvement for Distributed Drive Electric Vehicle Based on Motion Tracking Control

2018-01-05644/3/2018

The integrated control system which combines the differential drive assisted steering (DDAS) and the direct yaw moment control (DYC) for the distributed drive electric vehicle (DDEV) is studied. A handling improvement algorithm for the normal cornering maneuvers is proposed based on motion tracking control. Considering the ideal assistant power character curves at different velocities, an open-loop DDAS control strategy is developed to respond the driver’s demand of steering wheel torque. The DYC strategy contains the steering angle feedforward and the yaw rate feedback. The steering angle feedforward control strategy is employed to improve yaw rate steady gain of vehicle. The maximum feedforward coefficients at different velocities are obtained from the constraint of the motor external characteristic, final feedforward coefficients are calculated according to the ideal assistant power character curve of the DDAS. Meanwhile, an integral anti-windup PI control is proposed to track reference yaw rate based on linear single track model. In addition, a torque allocation algorithm is proposed to coordinate the driver’s accelerate intention with the additional vehicle yaw moment demand. Simulations and field tests under multiple maneuvers have been carried out. The results indicate that the proposed controller can reduce driver operating burden by decreasing the steering wheel torque while the transient response and the steady gain of the yaw rate are improved. The algorithm can also effectively rectify the under steering caused by accelerating and enhance the handling performance of the DDEV significantly.

Yang, Xing, Xiong, Lu, Leng, Bo, Li, Yue

Simulation Research of a Hydraulic Interconnected Suspension Based on a Hydraulic Energy Regenerative Shock Absorber

2018-01-05824/3/2018

The current paper proposes a hydraulic interconnected suspension system (HIS) based on a hydraulic energy-regenerative shock absorber (HESA) comparatively with the passive suspensions. The structure and working principles of the HIS system are introduced in order to investigate the damping performance and energy regeneration characteristics of the proposed system. Then, the dynamic characteristics of the HIS-HESA system have been investigated based on a 4-DOF longitudinal half vehicle model. In the simulation, two different road inputs were used in the dynamic characterization of the HIS-HESA; the warp sinusoidal excitation, and the random road signal. In addition, a comparative analysis was provided for the dynamic responses of the half vehicle model for both the HIS-HESA and the conventional suspension. Furthermore, a parametric analysis of the HIS-HESA has been carried out highlining the key parameters that have a remarkable effect on the HIS-HESA performance. The dynamic performance evaluation includes both of the body acceleration and the pitch angle as the main analysis criteria of the vehicle dynamic performance. The results showed that the vehicle with the HIS-HESA system has good anti-pitch performance and excellent ride performance against the traditional suspensions. Moreover, the HIS-HESA suspension system can regenerate some of the dissipated power due to the damping process.

Zou, Junyi, Guo, Xuexun, Xu, Lin, Abdelkareem, Mohamed A. A., Gong, Bian, Zhang, Jie, Tan, Gangfeng

Multi-Objective Optimization to Improve SUV Ride Performances Using MSC.ADAMS and Mode Frontier

2018-01-05754/3/2018

Ride is an important attribute which must be accounted in the passenger segment vehicles. Excessive H point acceleration, Steering wheel acceleration, Pitch acceleration can reduce the comfort of the driver and the passengers during high frequency and low frequency rough road events. Excessive Understeer gradient, roll gradient, roll acceleration and Sprung mass lift could affect the Vehicle driver interaction during Steady state cornering, Braking and Step steer events. The concept architecture of the vehicle plays an important role in how comfort the vehicle will be. This paper discusses how to improve SUV ride performances by keeping handling performance attributes same or better than base vehicle. Multi Objective Optimization was carried out by keeping spring, bushing and damper characteristic as the design variables to avoid new system or component development time and cost. The first step in this process is DOE (Design of Experiments method) which allows to select critical or highly influence input variables and to understand the effect of input variables on output performances. The consequent Optimization leads to select the optimum from various conflicting solutions.

Lenka, Visweswara Rao, Anthonysamy, Baskar, Londhe, Abhijit, Hatekar, Harshad

A Study of Suspension Tightening Torque on the R&H Performance of High Performance Vehicles

2018-01-05774/3/2018

Suspension is a system which operates dynamically according to road condition unlike other system statically mounted to the body. Especially this is more remarkable in high performance vehicle because there are more high inputs from road to suspension than normal vehicle. For this reason, the tightening torque of suspension system of high performance vehicle is more important than other systems and normal vehicle. To support the clamping between parts against force from road when cornering, optimized tightening torque is required to maximize R&H performance. For this optimization, it should be conducted first to comprehend how much performance effects on vehicle by tightening torque. This paper presents relationship between tightening torque of suspension parts hardware and R&H performance. Also for the robust mounting, it is focused on what managing method of clamping force and what kinds of mounting structure are efficient. 1 To investigate the tightening torque effect, blind driving evaluation is conducted as changing tightening torque. Basically set the tightening torque range and level first. For the next step, change the tightening torque with each level in same vehicle. Also to check the effect of mount area, change the torque in each area that is separated two section; axle area, subframe area. After changing torque, driver conducts the subjective R&H assessment without any notice of change. 2 To make robust mount in suspension system, research focused on mount type, method of managing clamping force and mount part structure type. There are two types in managing clamping force; angle controlled method and torque controlled method. Each type has different distribution of clamping force after tightened. Also each mounting part has different material and stiffness and joint type. It can influence on generating clamping force.

Song, Jieun, Lee, Byung-Kyu, Yoo, Sang-Hoon, Lee, Dae Hyeong

The Influence of Autonomous Driving on Passive Vehicle Dynamics

2018-01-05514/3/2018

Traditional vehicles are designed to be inherently stable. This is typically obtained by imposing a large positive static margin (SM). The main drawbacks of this approach are the resulting understeering behavior of the vehicle and, often, a decrease in peak lateral grip due to oversized rear tire characteristics. On the other hand, a lower SM can cause a greater time delay in the vehicle’s response which hardens the control of a vehicle at limit handling for a human being. By introducing advanced autonomous driving features into future vehicles, the human factor can be excluded in limit handling manoeuvers (e.g., obstacle avoidance occurrences) and, consequently, the need for a high SM (i.e., high controllability for human drivers) can be avoided. Therefore, it could be possible to exploit the passive vehicle dynamics and enhance the performance, both in terms of peak grip and transient response. The goal of this article is to explore if a decrease in SM can lead to a performance advantage on an obstacle avoidance manoeuver when the vehicle is driven by a robotic controller. This is achieved by analyzing the behavior of various vehicle models with different SMs and peak lateral acceleration on a nonstandard double lane change manoeuver. After having characterized the dynamic response of the various models in both steady-state and unsteady-state, several tests are run on a Driver-in-Motion (DiM) dynamic driving simulator driven by human drivers. The same tests are run again in a Model-in-the-Loop (MiL) simulation where the vehicle is controlled by means of a nonlinear model predictive control (NMPC). The results show that the robotic controller outperforms a human driver and poses interesting design challenges for autonomous vehicles in terms of passive stability and active controllers to modify vehicle stability online.

Novi, Tommaso, Liniger, Alex, Capitani, Renzo, Fainello, Marco, Danisi, Giacomo, Annicchiarico, Claudio

Comparison of Active Front Wheel Steering and Differential Braking for Yaw/Roll Stability Enhancement of a Coach

2018-01-08204/3/2018

Both active front wheel steering (AFS) and differential braking control (DBC) can improve the vehicle handling and stability. In this article, an AFS strategy and a DBC strategy are proposed and compared. The strategies are as follows: A yaw instability judging module and a rollover instability judging module are put forward to determine whether the coach is in a linear state and whether the additional torque/angle module should be actuated. The additional torque module based on linear quadratic regulator (LQR) and the additional steering wheel angle module based on adaptive proportion integral differential (PID) fuzzy controller are designed to make the actual yaw rate and sideslip angle track the reference yaw rate and sideslip angle. Under some typical driving conditions such as sinusoidal, J-turning, crosswind, and straight-line brake maneuver on the μ-split road, simulation tests are carried out for the coach with no control, DBC strategy, and AFS control, respectively. The comprehensive comparison of simulation results is made to verify the effectiveness of proposed strategies on improving vehicle handling and yaw stability. Results also show that the proposed two strategies can effectively prevent rollover of the vehicle and each has its own strengths for different maneuvers.

Zheng, Hongyu, yangyang, miao, Wang, Linlin, Zhang, Jiaxu

Fuzzy Control of Autonomous Intelligent Vehicles for Collision Avoidance Using Integrated Dynamics

06-11-01-0001

3/1/2018

This study aims to take the first step in bridging the gap between vehicle dynamics systems and autonomous control strategies research. More specifically, a nested method is employed to evaluate the collision avoidance ability of autonomous vehicles in the primary design stage theoretically based on both dynamics and control parameters. An integrated model is derived from a half car mathematical model in the lateral direction, consisting of two degrees of freedom, lateral deviation and yaw angle, with a traction mathematical model in the longitudinal direction, consisting of two degrees of freedom, the longitudinal velocity and rolling velocity of the wheel. The integrated model uses a mathematical power train model to generate the torque on the wheel and connects the two systems via the magic formula tyre model to represent the tyre non-linearity during augmented longitudinal and lateral dynamic attitudes. These mathematical models are represented using MATLAB in the time domain. Fuzzy logic is used for a path-following model to control the vehicle in the longitudinal and lateral directions. The dynamic behaviour is subjectively evaluated using an ISO 3888 test track. The vehicle dynamic response includes the vehicle’s path, steering angle, lateral acceleration, yaw rate and longitudinal velocity. The results demonstrate that the vehicle successfully selected the vehicle path within the track limits and avoided the obstacles along its path. These results highlight the importance of implementing both vehicle dynamic systems and autonomous control strategies in a meaningful integrated model for proper vehicle performance testing.

Sabry, Youssef, Aly, Mahmoud, Oraby, Walid, El-demerdash, Samir