Ziyou Song

Rule-based fault diagnosis of hall sensors and fault-tolerant control of PMSM

Hall sensor is widely used for estimating rotor phase of permanent magnet synchronous motor(PMSM). And rotor position is an essential parameter of PMSM control algorithm, hence it is very dangerous if Hall senor faults occur. But there is scarcely any research focusing on fault diagnosis and fault-tolerant control of Hall sensor used in PMSM. From this standpoint, the Hall sensor faults which may occur during the PMSM operating are theoretically analyzed. According to the analysis results, the fault diagnosis algorithm of Hall sensor, which is based on three rules, is proposed to classify the fault phenomena accurately. The rotor phase estimation algorithms, based on one or two Hall sensor(s), are initialized to engender the fault-tolerant control algorithm. The fault diagnosis algorithm can detect 60 Hall fault phenomena in total as well as all detections can be fulfilled in 1/138 rotor rotation period. The fault-tolerant control algorithm can achieve a smooth torque production which means the same control effect as normal control mode (with three Hall sensors). Finally, the PMSM bench test verifies the accuracy and rapidity of fault diagnosis and fault-tolerant control strategies. The fault diagnosis algorithm can detect all Hall sensor faults promptly and fault-tolerant control algorithm allows the PMSM to face failure conditions of one or two Hall sensor(s). In addition, the transitions between health-control and fault-tolerant control conditions are smooth without any additional noise and harshness. Proposed algorithms can deal with the Hall sensor faults of PMSM in real applications, and can be provided to realize the fault diagnosis and fault-tolerant control of PMSM.

Interaction of In-wheel Permanent Magnet Synchronous Motor with Tire Dynamics

Drive wheel systems combined with the in-wheel permanent magnet synchronous motor (I-PMSM) and the tire are highly electromechanical-coupled. However, the deformation dynamics of this system, which may influence the system performance, is neglected in most existing literatures. For this reason, a deformable tire and a detailed I-PMSM are modeled using Matlab/Simulink. Furthermore, the influence of tire/road contact interface is accurately described by the non-linear relaxation length-based model and magic formula pragmatic model. The drive wheel model used in this paper is closer to that of a real tire in contrast to the rigid tire model which is widely used. Based on the near-precise model mentioned above, the sensitivity of the dynamic tire and I-PMSM parameters to the relative error of slip ratio estimation is analyzed. Additionally, the torsional and longitudinal vibrations of the drive wheel are presented both in time and frequency domains when a quarter vehicle is started under conditions of a specific torque curve, which includes an abrupt torque change from 30 N · m to 200 N · m. The parameters sensitivity on drive wheel vibrations is also studied, and the parameters include the mass distribution ratio of tire, the tire torsional stiffness, the tire damping coefficient, and the hysteresis band of the PMSM current control algorithm. Finally, different target torque curves are compared in the simulation, which shows that the estimation error of the slip ratio gets violent, and the longitudinal force includes more fluctuation components with the increasing change rate of the torque. This paper analyzes the influence of the drive wheel deformation on the vehicle dynamic control, and provides useful information regarding the electric vehicle traction control.

Influence of tire dynamics on slip ratio estimation of independent driving wheel system

The independent driving wheel system, which is composed of in-wheel permanent magnet synchronous motor(I-PMSM) and tire, is more convenient to estimate the slip ratio because the rotary speed of the rotor can be accurately measured. However, the ring speed of the tire ring doesn’t equal to the rotor speed considering the tire deformation. For this reason, a deformable tire and a detailed I-PMSM are modeled by using Matlab/Simulink. Moreover, the tire/road contact interface(a slippery road) is accurately described by the non-linear relaxation length-based model and the Magic Formula pragmatic model. Based on the relatively accurate model, the error of slip ratio estimated by the rotor rotary speed is analyzed in both time and frequency domains when a quarter car is started by the I-PMSM with a definite target torque input curve. In addition, the natural frequencies(NFs) of the driving wheel system with variable parameters are illustrated to present the relationship between the slip ratio estimation error and the NF. According to this relationship, a low-pass filter, whose cut-off frequency corresponds to the NF, is proposed to eliminate the error in the estimated slip ratio. The analysis, concerning the effect of the driving wheel parameters and road conditions on slip ratio estimation, shows that the peak estimation error can be reduced up to 75% when the LPF is adopted. The robustness and effectiveness of the LPF are therefore validated. This paper builds up the deformable tire model and the detailed I-PMSM models, and analyzes the effect of the driving wheel parameters and road conditions on slip ratio estimation.

Wheel Slip Control Using Sliding-Mode Technique and Maximum Transmissible Torque Estimation

This paper presents the analysis and design of a novel traction control system (TCS) based on sliding-mode control (SMC) and maximum transmissible torque estimation (MTTE) technique, which is employed in four-wheel independent drive electric vehicles (EVs) without detecting the vehicle velocity and acceleration. The original MTTE technique is effective with regard to the antislip control; however, it cannot sufficiently utilize the adhesive force from the tire–road surface. In the proposed TCS algorithm, only front wheels are equipped with the MTTE technique, while rear wheels are equipped with the SMC technique. As a result, the front wheel is critically controlled by the MTTE technique. Thus, its rotary speed can be used to approximately estimate the chassis velocity and acceleration, which are key input parameters of the SMC. The rear wheel slip ratio can be therefore controlled by the SMC which is robust against uncertainties and disturbances of parameters for exploiting more transmissible friction force. In addition, the stability of MTTE is analyzed in this paper because an important parameter is neglected in the original MTTE technique. As a result, the stability condition is changed, and the MTTE is modified in the proposed TCS according to the new conclusion. A half four-wheel drive (4WD) EV model is initially built using matlab/simulink. This paper investigates the proposed TCS for various adhesive conditions involving abrupt change in road friction. Compared with the original MTTE technique, the comprehensive performance, particularly the acceleration ability, is significantly improved by the proposed controller. The simulation result validates the effectiveness and robustness of the proposed TCS.

Traction Control System for EV Based on Modified Maximum Transmissible Torque Estimation

Traction control system (TCS) of electric vehicles (EVs) without detecting vehicle velocity is drawing more and more attention. The most challenging problem in TCS is controlling the drive wheel with indirect control inputs. The maximum transmissible torque estimation (MTTE) method which is effective in terms of antiskid control has been proposed, however, this method is conservative because it cannot take sufficient advantage of adhesive force under constant torque condition even if the road is slippery. Therefore, a modified maximum transmissible torque estimation (M-MTTE) algorithm with a various relaxation factor is proposed in this paper. By analyzing and comparing the simulation results with prior control method, it is validated that M-MTTE is robust on antiskid control and achieves a better acceleration control effect.

Optimal torque distribution strategy considering energy loss and tire adhesion for 4WD electric vehicles

Distributed electric vehicles are typical over- actuated systems, therefore, the optimal torque distribution can be realized through the driving wheels. It is meaningful to extend driving range and reinforce stability of vehicles by using optimal torque allocation methods. In this paper, a quadratic programing based torque allocation strategy is proposed to minimize the drivetrain power loss and utilize the tire-road friction of each wheel reasonably. A co-simulation using CarSim and Simulink is conducted to prove the effectiveness of the proposed algorithm under different conditions.