In-wheel Vehicle Research Articles

Control Strategy of Different Operation Modes for a Multiple Torque Component Single Air Gap Magnetless Machine

The fault-tolerant capability of the electrical machine system in the event of certain faults is critical for the application in the fields of aerospace, in-wheel vehicle, etc. This paper analyzes the operation modes and control principle of a novel type of machine with multiple electromagnetic torque components. Firstly, the topology and operation principle of the novel machine as well as the control system are illustrated, then the mathematical model, especially the torque component, and the control principle considering the characteristics of multi-torque components is analyzed. After that the operation modes of the machine under different working conditions and simulation are introduced. Finally, the experimental results are given to verify the control strategy according to different operation modes.

Multi-objective optimization of the suspension parameters in the in-wheel electric vehicle

The hub motor significantly increases the unsprung mass of electric in-wheel vehicles, which deteriorates the ride comfort and safety of vehicles and which can be effectively improved by optimizing the main suspension parameters of vehicles reasonably, so a multi-objective optimization method of main suspension parameters based on adaptive particle swarm algorithm is proposed and the dynamic model of a half in-wheel electric vehicle is established. Taking the stiffness coefficient of the suspension damping spring and damping coefficient of the damper as independent variables, the vertical acceleration of the body, the pitch acceleration and the vertical impact force of the hub motor as optimization variables, and the dynamic deflection of the suspension and the dynamic load of the wheel as constraint variables, the multi-objective optimization function is constructed, and the parameters are simulated and optimized under the compound pavement. The simulation results show that the vertical acceleration and pitch acceleration are reduced by 20.2% and 18.4% respectively, the vertical impact force of the front hub motor is reduced by 3.7%, and the ride comfort and safety are significantly improved.

Design of a New Relieving-DC-Saturation Hybrid Reluctance Machine for Fault-Tolerant In-Wheel Direct Drive

This article aims to propose a new hybrid reluctance machine equipped with relieving-dc-saturation (RDCS) ability for electric vehicle in-wheel drive. The proposed machine uses integrated ac and dc current excitation to eliminate extra dc field coils for the efficient torque generation. Besides, considering the inherent dc saturation in stator core caused by dc current excitation, slot PMs are artificially introduced to provide RDCS effect and thus boost torque density. Moreover, with a modular magnetic field configuration, the proposed topology exhibits excellent fault-tolerant potential at both open-circuit and short-circuit condition, making it suitable for safety-critical in-wheel vehicle propulsion. In this article, the machine configuration and operation principle are introduced, with emphasis on its RDCS effect and corresponding design consideration. Further, performance of this new topology is evaluated by both finite element analysis and prototype experiments. It is revealed that, with this RDCS ability, torque density of the proposed machine can be enhanced by about 25% under relatively high current density.

Novel Evaluation Systems for Compact In-Wheel Vehicles Considering Deviation of Load Torque between Left and Right Wheel

In-wheel vehicles driven by electrical energy are more efficient and emit less pollutant emissions than conventional vehicles powered by internal combustion engine. However, evaluation system for the in-wheel vehicles is not well established, the absence of the evaluation system for in-wheel vehicles is one of the major obstacles to commercialization of the in-wheel vehicles. In this study, we have suggested a new methodology of dynamometer test for in-wheel vehicle and devised simulators that can analyze the performance of in-wheel vehicles. In general, a new vehicle goes through the performance evaluation on dynamometer test which can simulate a straight motion of vehicles. Due to the characteristics of dynamometer test which simulates only a straight motion, it is not suitable for test for in-wheel vehicle. In the case of in-wheel vehicle, since driving motors on wheels are controlled independently, the stability of in-wheel vehicles during turning is important. Therefore, we have developed an in-wheel vehicle simulator to build a dynamometer test which can simulate turning motions of in-wheel vehicle. Using CarSim & Matlab/Simulink, we realized dynamic motion of a vehicle on a curved 3-demensional road. With this simulator, we could extract the load torque of each wheel during driving on the 3D virtual road. If the derived load torque is applied to motors of dynamometer test, it is possible to simulate driving on real road, through which the performance and the efficiency of in-wheel vehicles can be analyzed before the actual vehicle experiment. Also, we developed another simulator to evaluate the performance and the efficiency of in-wheel vehicles. This simulator allows us to evaluate the performance of in-wheel vehicles by using load torque derived from previous simulator. In this study, we developed two types of simulators to evaluate the performance of in-wheel vehicles in the simulation environment where the load torque for each wheel is different. One simulator derives load torque of each wheel and the other simulator evaluates the performance of in-wheel vehicles.

Multiple Fault-Tolerant In-Wheel Vehicle Control Based on High-level Control Reconfiguration

The paper deals with the fault-tolerant reconfigurable control design of a four-wheel independently-actuated (4WIA) electric vehicle. The purpose of the proposed method is to ensure the velocity and path tracking of the 4WIA vehicle in the event of a fault or performance degradation in one or even several in-wheel electric motors. The novelty of the presented method is the high-level control reallocation method based on the Linear Parameter Varying (LPV) control framework, by which the torque vectoring and steering of the vehicle are modified in order to deal with the impact of faulty in-wheel motors. The operation of the designed fault-tolerant method is validated in CarSim simulation environment.

실차 주행 조건을 고려한 인휠 차량 거동 해석 및 동력 시험계 부하 토크 인가를 위한 구동 모터의 동적 부하 도출시스템 개발

Abstract : This paper discusses about analyzing in-wheel vehicle’s dynamic motion and load torque. Since in-wheel vehicle controls each left and right driving wheels, it is dangerous if vehicle’s wheels are not in a cooperative control. First, this study builds the main wheel control logic using PID control theory and evaluates the stability. Using Carsim-Matlab/Simulink, vehicle dynamic motion is simulated in virtual 3D driving road. Through this, in-wheel vehicle’s driving performance can be analyzed. The target vehicle is a rear-wheel drive in D-class sedan. Second, by using the first In-wheel vehicle’s performance results, it derivate the drive motor’s dynamic load torque for applying the dynamometer. Extracted load torque impute to dynamometer’s load motor, linear experiment in dynamometer can replicated the 3-D road driving status. Also it, will be able to evaluate the more accurate performance analysis and stability, as a previous step of actual vehicle experiment. Key words : Inwheel(인휠), Carsim(카심), Driving performance(주행 성능), Load torque(부하 토크), Dynamo-meter(동력 시험계)

Torque Distribution Algorithm for an Independently Driven Electric Vehicle Using a Fuzzy Control Method

The in-wheel electric vehicle is expected to be a popular next-generation vehicle because an in-wheel system can simplify the powertrain and improve driving performance. In addition, it also has an advantage in that it maximizes driving efficiency through independent torque control considering the motor efficiency. However, there is an instability problem if only the driving torque is controlled in consideration of only the motor efficiency. In this paper, integrated torque distribution strategies are proposed to overcome these problems. The control algorithm consists of various strategies for optimizing driving efficiency, satisfying driver demands, and considering tire slip and vehicle cornering. Fuzzy logic is used to determine the appropriate timing of intervention for each distribution strategy. A performance simulator for in-wheel electric vehicles was developed by using MATLAB/Simulink and CarSim to validate the control strategies. From simulation results under complex driving conditions, the proposed algorithm was verified to improve both the driving stability and fuel economy of the in-wheel vehicle.

Reconfgurable Fault-Tolerant Control of In-Wheel Electric Vehicles with Steering System Failure

The paper deals with the robust and fault tolerant control of an in-wheel electric vehicle, operated by four independently actuated in-wheel motors and steer-by-wire steering system. The goal of the design is to realize velocity and road trajectory tracking of the in-wheel vehicle, even during a fault event in the steer-by-wire steering system. When such a fault is detected, the control system is reconfgured and the torque allocation of the in-wheel engines is recalculated to substitute for the yaw moment originally generated by the steering system. Thus, the vehicle is able to follow the designed path and velocity solely with torque vectoring generated by the independently-controlled in-wheel motors. The high-level motion control of the vehicle is realized founded on the LPV framework, while the reconfguration is based on constrained optimization techniques. The operation of the designed control system is demonstrated in a CarSim simulation environment.

Intelligent Sensorless ABS for In-Wheel Electric Vehicles

The design of electric vehicles (EVs) is increasingly based upon using the in-wheel technology. In this design, the use of a separate electric machine at each corner of the vehicle provides unique opportunities for innovative vehicle control strategies. In this paper, a sensorless antilock braking system (ABS) is proposed that eliminates the need for the installation of separate conventional ABS sensors and saves the costs associated with the installation and maintenance of those sensors for in-wheel EVs. The proposed ABS exploits the information carried by the back electromotive force (EMF) of the electric machines of the in-wheel vehicle to obtain accurate wheel speed estimation at each wheel and conduct road identification simultaneously. A wavelet-packet denoising method is used to maintain the accuracy of wheel speed estimation in the presence of noise. In addition to sensorless wheel speed estimation, the proposed ABS is capable of road identification by analyzing the back EMF signal using discrete wavelet transforms. The design was realized and fully tested using actual ABS hardware. The results of the sensorless technique were compared with a commercial ABS sensor. The experimental results showed that the sensorless ABS can adequately replace the conventional ABS sensor in in-wheel EVs and significantly improve the performance of the ABS.

Research and Design of a New Kind In-Wheel Driving System

In order to solve one of the main negative effects of in-wheel driving system, caused by heavy unsprung mass, a new kind of design is put forward: in which in-wheel motor is used not only as a driving part, but also as a mass element in a dynamic vibration absorber. By changing motor from unsprung mass into sprung mass, the dynamic vibration absorber is no longer constrained by in-wheel space and vehicle mass. Due to the reduction of unsprung mass, vertical performance of vehicle, especially wheel ground adhesion is improved. An efficiency, compact and reliable system is designed in the paper.