CN-116512934-B - Torque distribution control method for realizing energy consumption optimization of three-motor four-drive electric automobile

CN116512934BCN 116512934 BCN116512934 BCN 116512934BCN-116512934-B

Abstract

A torque distribution control method for realizing energy consumption optimization of a three-motor four-drive electric automobile belongs to the technical field of torque distribution control of electric automobiles. The invention aims to obtain a prediction model of an MPC controller by utilizing a dynamic model of a tire longitudinal slip rate and wheel driving torque, design a plurality of cost functions and adjusting weights to distribute total driving torque to three driving motors, design driving torque constraints of a front shaft motor and two rear shaft driving motors, ensure driving safety, and finally design a torque distribution control method of a performance evaluation index function for realizing energy consumption optimization of a three-motor four-drive electric automobile. In order to realize better stability and economical coordinated control, the cost function is designed to enable each power source to generate reasonable yaw moment in the torque distribution process so as to ensure stability, and simultaneously enable the front axle motor and the two rear wheel hub motors to work in a high-efficiency area as much as possible, so that the energy-saving aim of the vehicle is realized to the greatest extent on the premise of not influencing the operation stability.

Inventors

WANG PING
REN QIAO
LIN JIAMEI
HU YUNFENG
CHEN HONG

Assignees

吉林大学

Dates

Publication Date: 20260505
Application Date: 20230515

Claims (1)

1. A torque distribution control method for realizing energy consumption optimization of a three-motor four-drive electric automobile is characterized by comprising the following steps: S1, a prediction model based on energy consumption optimization MPC controller is obtained by utilizing a dynamic model of tire slip rate and wheel driving torque, wherein state variables of the prediction model consist of four wheel slip rates, and the control quantity is driving wheel torque; ① Calculating a total torque demand command for the driver based on the desired longitudinal vehicle speed ; ② Solving for yaw moment for stabilizing vehicle driving by tracking expected values of vehicle centroid slip angle and yaw rate ; S2, obtaining a prediction model of the energy consumption optimized MPC controller The controller is designed, wherein state variables of a prediction model consist of four wheel slip rates, the control quantity is driving wheel torque, and the prediction model is as follows: (6) Wherein the method comprises the steps of , , For the effective radius of the tire, The state vector is defined as: Control amount Torque is output for four drive wheels: wherein A driving torque is output for the front axle motor, For front axle motor to left and right wheels a distribution coefficient of the driving torque of the motor; wheel moment of inertia; Is the tire longitudinal stiffness; Representing a wheel Slip ratio of (b) subscript Respectively representing a left front wheel, a right front wheel, a left rear wheel and a right rear wheel; And The motor on the left side of the rear axle outputs driving torque and the motor on the right side of the rear axle outputs driving torque respectively; s3, designing 4 cost functions respectively including a first objective function Second objective function Third objective function And a first objective function The first objective function is designed to distribute total required traction torque to a driving motor and enable each driving wheel to generate yaw moment to ensure steering stability, the second objective function is designed to reduce tire dynamic slip energy dissipation, the third objective function is designed to a punishment matrix aiming at excessive slip phenomenon of tires, the longitudinal slip of the tires is restrained, meanwhile, better stability performance is obtained, the fourth objective function is designed to reduce energy efficiency loss of the motor, polynomial fitting is conducted for 6 times respectively according to efficiency Map diagrams of a front shaft motor and a rear shaft motor, and under the condition of meeting the total driving force requirement, the motor efficient operating point is solved based on MPC rolling optimization on-line optimizing; The objective function is obtained as follows: (18) S4, when the driving torque of the front axle and the rear axle is distributed, the driving torque of the front axle is not larger than the driving torque of the rear axle, the constraint of the controller is designed, the objective function is optimized and solved, and the control quantity is the driving torque of the wheels; S5, designing performance index evaluation functions from four aspects of steering stability, motor energy-saving performance, tire slip energy loss and longitudinal vehicle speed tracking.

Description

Torque distribution control method for realizing energy consumption optimization of three-motor four-drive electric automobile Technical Field The invention belongs to the technical field of torque distribution control of electric automobiles. Background In order to alleviate the problems of global energy shortage, environmental pollution and the like, the field of the electric automobile which is more environment-friendly and energy-saving is developed faster and faster. Compared with the traditional automobile, the electric automobile can improve the efficiency of the whole electric automobile system through light design and efficient electric drive system configuration, and particularly the distributed four-wheel drive electric automobile, because the transmission system is omitted, the whole automobile structure is simplified, the design is more flexible, and the operability of control is optimized. When the vehicle is in the running process, under the constraint of the power performance of the whole vehicle, the torque distribution among the power sources can be more freely realized, and the running economy of the vehicle is improved. The torque distribution control of the distributed driving electric vehicle mainly takes four-motor full-drive as a research object at present, the four-motor full-drive vehicle is high in configuration cost, and four motors work simultaneously to easily cause power redundancy so as to increase energy loss, so that an ideal energy-saving effect is difficult to achieve. The following problems still exist at present: 1. The research on the energy conservation of the three-motor four-drive electric automobile at present focuses on how to distribute total required torque to a front axle motor and two rear wheel hub motors so as to reduce motor efficiency loss, mainly expands around global optimization and instantaneous optimization, and under the relatively fixed linear working condition, the global optimization is mainly used for providing basis for the torque distribution ratio among all driving motors based on global optimization results. 2. The research of the distributed driving stability control which is carried out at present always strictly ensures the stability of the vehicle through yaw moment control, which limits the torque distribution ratio of the left motor and the right motor, and does not consider whether the side torque distribution can cause energy loss of the motors or not, thereby influencing the economical efficiency of the vehicle. In addition, dynamic coordination of stability and economy cannot be achieved because stability is severely constrained. 3. When the vehicle runs under dynamic working conditions such as acceleration and deceleration, the problem of energy dissipation of longitudinal sliding of the tire caused by driving force saturation due to load change of front and rear axles is not considered in the current research, and meanwhile, the problem of safety caused by locking of the wheels due to unreasonable torque distribution under the working conditions is not considered. Disclosure of Invention The invention aims to obtain a prediction model of an MPC controller by utilizing a dynamic model of a tire longitudinal slip rate and wheel driving torque, design a plurality of cost functions and adjusting weights to distribute total driving torque to three driving motors, design driving torque constraints of a front shaft motor and two rear shaft driving motors, ensure driving safety, and finally design a torque distribution control method of a performance evaluation index function for realizing energy consumption optimization of a three-motor four-drive electric automobile. The method comprises the following steps: S1, a prediction model based on energy consumption optimization MPC controller is obtained by utilizing a dynamic model of tire slip rate and wheel driving torque, wherein state variables of the prediction model consist of four wheel slip rates, and the control quantity is driving wheel torque; ① Calculating a total torque demand command for the driver based on the desired longitudinal vehicle speed : (1) Wherein, the ,As a parameter of the PI controller,,Tracking reference longitudinal speed and vehicle longitudinal speed respectively; ② Solving for yaw moment for stabilizing vehicle driving by tracking expected values of vehicle centroid slip angle and yaw rate ; S2, obtaining a prediction model of the energy consumption optimized MPC controller ① The steady state tire slip ratio is defined as: (2) Wherein, the For the rotational speed of the tire,Is the wheel slip ratio, whereinRespectively representing a left front wheel, a right front left rear wheel and a right rear wheel,The effective radius of the tire; The longitudinal force is positively correlated with the tire slip ratio, and the linearity of the longitudinal force is expressed as: (3) In the middle of 、The longitudinal and vertical forces of the ith tire,Is the moment