Research on Simulation of Matching Limited-Slip Torque of ELSD with Vehicle Performance

　　Research on Simulation of Matching Limited-Slip Torque of ELSD with Vehicle Performance
　　In the wake of the development and application of new techniques, some kinds of vehicle applied control systems come forth to improve one or more kinds of performance of vehicle, such as Anti-lock Braking System(ABS), Cruise Control System(CCS), Vehicle Stable System(VS) and Anti-Slip Regulation System(ASR). ASR is the most famous among of all those control systems. For the capability of improving the steering stability and driving performance of vehicle obviously, decreasing the tyre abrasion and the neodymium standard state possibility of accident, as well as enhancing the security of the vehicle, ASR is applied widely and rapidly abroad, and paid extensive attention in our country.The main controlling modes of ASR include: regulating output torque of the engine, regulating braking torque of driving wheels, and regulating clutch or transmission and regulating differential. Among which, regulating differential is the most important mode of all. According to the regulating differential, obtained drive torque from both drive wheels can keep changing with the control instruction and road condition. When the accreting quotiety(μ)contrasts distinctly and the lowμside occurs slip rotating,the drive accreting power of highμside drive wheel can exert sufficiently, as a result, the vehicle drive power and steering stability will improve in certain degree.Electronically controlled limited slip differential (ELSD) is an active control system which works to regulate and control limited-slip performance automatically by means of electronically controlled technique. According to the condition of vehicle driving and road, ELSD can modulate its limited-slip performance by restraining excessive slip of driving wheel and redistribute drive torque between driving wheels.
　　Therefore, ELSD can fully exploit the available traction force from the road adhesion and effective improve the traction, stability, controllability, drivability and safety. ELSD is the efficient method of Torque Manage technique of Differential (TMD).The whole thesis is supported by the science development project of Jilin Province science and technology committee“Research and Development of Electronically-controlled Limited Slip Differential”. On the basis of the latest advancement of ELSD research at home and abroad, the theoretical research and development about motor-drive-type ELSD is studied. In this paper, the main research content contains:1. Study on the structure of ELSDControl system and executive system as the two main constitute of ELSD are studied in detail.Control system mainly consists of sensor, electronic unit, micro motor, speed reducer and actuating mechanism. Magneto electric speed sensor, 55LY53 type permanent-magnet direct current toque motor, harmonic reducer and cylindrical gear reducer are employed in the control system. Actuating mechanism is designed to pass axial packing force to executive system via geared sector, ball and float sleeve. Control system serves to adjust limited-slip performance of ELSD. Executive system is composed of two sections such as differential mechanism and limited-slip mechanism. Differential mechanism is to make sure the difference between half-axle by planetary gear mechanism. Limited-slip mechanism change axial packing force into limited-slip moment and realize the limited-slip performance of ELSD.The structure research and working process of ELSD are also the foundation of the design and application of ELSD.2. Study on self-adjusting control algorithm for ELSD
　　The control object of ELSD used to limit the excessive slip of the low-adhesion-side driving wheel and dynamically regulate its limited-slip performance is put forward and control strategy is constituted. Current control is adopted to adjust output torque of torque motor.To carry out its control object and control strategy, some control technique of ELSD are discussed. Firstly the application on PID control algorithm is studied. In order to improve its control effect and its robust ability, fuzzy PID self-setting control algorithm is finally chosen. Fuzzy control table is made by the off-line indirect method.The research on control algorithm of ELSD is also the foundation of the theory and application to actualize limited-slip performance.3. The model of vehicle four-wheel dynamic Based on vehicle parameter of a RWD vehicle, the four-wheel dynamic model is set up by modeling of engine, transmission, main reducer, ELSD and tyre mathematical model. And the mathematical model is also the foundation of the match between limited-slip torque of ELSD and vehicle performance.4. Study on simulation and analysis Based on the mathematical model, the simulation model is made by MATLAB/SIMULINK. The power performance and handling quality and stability of vehicle with ELSD is studied, on the construction of the simulation model.The simulation results show that: ELSD can improve on power performance. It decrease accelerating time and increase maximum grade ability on the split-μroad. It can enhance under steer and improve stability. When steady-state cornering, it augment ratio of cornering radius and difference of side-slip angles between front axle and rear axle. When slalom running, it reduce average yaw angular velocity and average side acceleration. ELSD slightly reduce the controllability. It aggrandizes average steering angle and steering torque.