Yinong Li

Integrated control on MR vehicle suspension system associated with braking and steering control

This article presents a hierarchy control strategy for magneto-rheological suspension system integrated with active braking and active front steering subsystems. This is proposed for the improvement of ride comfort and vehicle stability under different kinds of driving conditions. A nonlinear complicated full vehicle model which includes the longitudinal, lateral and vertical motions is established and combined with a modified coupling ‘Magic Formula’ tyre model. Subsequently, the global state identification and task assignment logic are formulated by adopting several driving conditions such as the straight driving and cornering state. A fuzzy control strategy is then used for the suspension system, while a sliding mode control technique is utilised for both braking and steering systems. In order to demonstrate the effectiveness of the proposed control methodology, control performances such as roll angle, yaw rate and vehicle trajectory are evaluated and presented.

Effect of vertical and lateral coupling between tyre and road on vehicle rollover

The vehicle stability involves many aspects, such as the anti-rollover stability in extreme steering operations and the vehicle lateral stability in normal steering operations. The relationships between vehicle stabilities in extreme and normal circumstances obtain less attention according to the present research works. In this paper, the coupling interactions between vehicle anti-rollover and lateral stability, as well as the effect of road excitation, are taken into account on the vehicle rollover analysis. The results in this paper indicate that some parameters influence the different vehicle stabilities diversely or even contradictorily. And it has been found that there are contradictions between the vehicle rollover mitigation performance and the lateral stability. The direct cause for the contradiction is the lateral coupling between tyres and road. Tyres with high adhesion capacity imply that the vehicle possesses a high performance ability to keep driving direction, whereas the rollover risk of this vehicle increases due to the greater lateral force that tyres can provide. Furthermore, these contradictions are intensified indirectly by the vertical coupling between tyres and road. The excitation from road not only deteriorates the tyres’ adhesive condition, but also has a considerable effect on the rollover in some cases.

Global integrated control of vehicle suspension and chassis key subsystems

Abstract This paper presents a new integrated control methodology for vehicle chassis subsystems associated with controlled suspension, braking system, and steering systems. In order to reflect the practical vehicle better, a non-linear complicated full-vehicle model which includes longitudinal, lateral, and vertical dynamics is established and combined with the modified non-linear tyre model. Then, a main objective-oriented hierarchical control strategy is proposed for global integrated control of chassis subsystems to improve the vehicle performance during different kinds of driving condition. The proposed hierarchical strategy consists of two layers. The upper layer is a system supervisory layer which is used to identify the vehicle states and to assign the task for each controllable subsystem based on their effective regions and the detected state signals of the system. The lower layer is the executive layer interfaced to actuators of the chassis subsystem. In this layer, different controllers which can be switched to a special vehicle state are designed by using fuzzy control and integral sliding-mode control methods. The effectiveness of the proposed control strategy is verified via computer simulations, showing the results of three typical driving conditions.

Vehicle Lateral Stability Control Based on Sliding Mode Control

In view of the vehicle cornering or path changing under ultimate handling maneuver, a 4-DOF nonlinear vehicle dynamics model which takes the longitudinal velocity, lateral velocity, yaw rate and body roll angle as the state variables is presented. Based on the dynamic analysis, the method which using additional yaw moment produced by different longitudinal braking force among each wheels to improving vehicle handling stability in emergency situations is discussed. Considering the slip angle of the centroid as the one of the vehicle state variables is difficult to measuring, the slip angle estimation method based on vehicle dynamic model and kinematics is designed. And then, based on the theory of sliding model control, the combining sliding mode control system is founded, which taking the vehicle yaw rate and body centroid slip angle errors between the estimated and the real as the input variables, and taking the braking torque and the steering angle as control aims. The simulation results indicate that the control method can effectively improve the vehicle lateral handling stability.

Effect of the unbalanced vertical force of a switched reluctance motor on the stability and the comfort of an in-wheel motor electric vehicle

Switched reluctance motors are well suited to in-wheel-motor-driven electric vehicles because of their numerous advantages, such as a high torque density, a high operating efficiency and excellent power–speed characteristics. However, these advantages are overshadowed by their inherent high torque ripple and vibrations. The unbalanced radial force of the switched reluctance motor is one of the main reasons for vibrations of the switched reluctance motor but has attracted less attention for in-wheel motor applications according to previous research. In this paper, the vertical component of the residual unbalanced radial force of the switched reluctance motor, i.e. the vertical force of the switched reluctance motor, is taken into account in the stability and comfort analysis for in-wheel-motor-driven electric vehicles. The results in this paper indicate that the vertical force of the switched reluctance motor has a great effect on the lateral and anti-rollover stabilities of the vehicle. The direct cause of this phenomenon is that the vertical force of the switched reluctance motor is directly applied on the wheels, which will result in a significant variation in the tyre load, and the tyre can easily jump off the ground. Furthermore, the frequency of the vertical force of the switched reluctance motor covers a wide bandwidth which involves the resonance frequencies of the vehicle body’s vibrations and the wheel bounce. As a result, the comfort of the vehicle is greatly harmed. Therefore, the effect of the vertical force of the switched reluctance motor on the the comfort of the vehicle is also considerable in some resonance situations. The conclusion is that the vertical force of the switched reluctance motor not only causes the stability of the vehicle to deteriorate but also has a considerable effect on the the comfort of the vehicle, and an appropriate control method for the switched reluctance motor is desired.

Efficiency improvement of vehicle active suspension based on multi-objective integrated optimization

Active suspension can effectively resolve the contradictions between vehicle ride comfort and stability. However, a new contradiction between the active suspension performance and efficiency is aroused. Active suspension with excellent performance requires high actuation power and force in an aggressive condition, which is usually an excess capacity for normal conditions. To improve the efficiency and capacity utilization rate, this paper conducted an investigation on the efficiency and utilization rate of vehicle active suspension based on a seven degrees-of-freedom full vehicle mode with a linear quadratic Gaussian active suspension controller. The multiple objectives of active suspension performance and efficiency are integrally optimized via genetic algorithm with an elaborately designed penalty function. The proposed integration of multiple objectives is proved effective according to the comprehensive comparison analysis. The overall performance of the optimized suspension achieved the Pareto optimality. Not only a better balance between the ride comfort and stability is accomplished, but also the active suspension utilization rate is improved. By this method, the obtained Pareto optimality set can greatly improve the parameters matching and design of the active suspension.

FxLMS method for suppressing in-wheel switched reluctance motor vertical force based on vehicle active suspension system

The vibration of SRM obtains less attention for in-wheel motor applications according to the present research works. In this paper, the vertical component of SRM unbalanced radial force, which is named as SRM vertical force, is taken into account in suspension performance for in-wheel motor driven electric vehicles (IWM-EV). The analysis results suggest that SRM vertical force has a great effect on suspension performance. The direct cause for this phenomenon is that SRM vertical force is directly exerted on the wheel, which will result in great variation in tyre dynamic load and the tyre will easily jump off the ground. Furthermore, the frequency of SRM vertical force is broad which covers the suspension resonance frequencies. So it is easy to arouse suspension resonance and greatly damage suspension performance. Aiming at the new problem, FxLMS (filtered-X least mean square) controller is proposed to improve suspension performance. The FxLMS controller is based on active suspension system which can generate the controllable force to suppress the vibration caused by SRM vertical force. The conclusion shows that it is effective to take advantage of active suspensions to reduce the effect of SRM vertical force on suspension performance.

Study of grey predictive-fuzzy control for MR semi-active suspension

The bench tests of damping force controllability, response characteristic in time and frequency domain have been done for a special magneto-rheological (MR) damper. A dynamic model of quarter vehicle semi-active suspension system has been established. For improving the performance of traditional fuzzy controller (TFC) on the MR suspension, a grey predictive-fuzzy controller (GPFC) is proposed based on the grey prediction algorithm which is used to estimate the next-step output of system and then as the input of TFC. It makes the TFC possess a function of pre-compensation for the system error. Simulation contrast analysis among skyhook control, TFC and GPFC has been presented and the bench test of quarter vehicle suspension has been done so as to verify the effectiveness of the proposed control strategy. The results show that the MR damper can respond fast and as well with wide frequency bandwidth. Both the simulation and test results demonstrate that the performance of the GPFC is the best, and the time response is superior to that of TFC, but slower than that of sky-hook control.

Research on current controller of Magnetorhelogical damper system

A method of designing a linear current controller based on an H-type bridge chopper is presented with consideration of the impedance behavior and magnetic excitation requirements of the MR (Magnetorhelogical) damper system. Furthermore, parameters of the current controller affecting the performance of MR damper system are investigated. Then a dynamic model of current controller is established, and the characteristic of the model is analyzed. The results of the simulation and experiments indicate that this current controller has not only a short response time of the current, but also a good linearity between control voltage and output current. And the current supplied by the current controller has a large adjustable range.

Multi-objective optimal design of magnetorheological engine mount based on an improved non-dominated sorting genetic algorithm

A novel flow-mode magneto-rheological (MR) engine mount integrated a diaphragm de-coupler and the spoiler plate is designed and developed to isolate engine and the transmission from the chassis in a wide frequency range and overcome the stiffness in high frequency. A lumped parameter model of the MR engine mount in single degree of freedom system is further developed based on bond graph method to predict the performance of the MR engine mount accurately. The optimization mathematical model is established to minimize the total of force transmissibility over several frequency ranges addressed. In this mathematical model, the lumped parameters are considered as design variables. The maximum of force transmissibility and the corresponding frequency in low frequency range as well as individual lumped parameter are limited as constraints. The multiple interval sensitivity analysis method is developed to select the optimized variables and improve the efficiency of optimization process. An improved non-dominated sorting genetic algorithm (NSGA-II) is used to solve the multi-objective optimization problem. The synthesized distance between the individual in Pareto set and the individual in possible set in engineering is defined and calculated. A set of real design parameters is thus obtained by the internal relationship between the optimal lumped parameters and practical design parameters for the MR engine mount. The program flowchart for the improved non-dominated sorting genetic algorithm (NSGA-II) is given. The obtained results demonstrate the effectiveness of the proposed optimization approach in minimizing the total of force transmissibility over several frequency ranges addressed.