Research on Torque Management Safety Monitoring Control for Hybrid Vehicles

Hybrid vehicles are driven by the vehicle controller, engine controller and motor controller through torque control, and there may be unexpected acceleration or deceleration of the vehicle beyond the driver's expectation due to systematic failure and random hardware failure. Based on the torque control strategy of hybrid vehicles, the safety monitoring model design of torque control is carried out according to the ISO 26262 safety analysis method. Through the establishment of safety goals and the analysis of safety concepts, this paper conducts designs including the driver allowable torque design for safety monitoring, the driver torque prediction design for safety monitoring, the rationality judgment design of driver torque for safety monitoring, the functional safety degradation design and the engine start-stop status monitoring, enabling the system to transition to a safe state when errors occur. Among them, the design of the driver's allowable torque includes the allowable requested torque of the accelerator pedal, the crawling allowable requested torque, and the coordination and arbitration with the external intervention torque, the Adas requested torque, and the vehicle's allowable torque based on vehicle speed and acceleration to obtain the allowable torque finally used for functional safety torque monitoring. The driver's torque prediction design for safety monitoring includes the prediction of the indicated torque of the crankshaft based on the angular acceleration signal of the crankshaft. The rationality judgment design of the driver's torque for safety monitoring includes monitoring the allowable wheel-end braking torque and the actual wheel-end braking torque, monitoring the allowable front axle and rear axle wheel-end propulsion torque and the actual wheel-end propulsion torque, and monitoring the allowable transmission input shaft propulsion torque and the actual transmission input shaft propulsion torque. Engine start-stop status monitoring includes that the start and stop requests of the engine need to pass the corresponding verification of functional safety, and only the requests that pass the verification will be responded by the actuator. Degradation design includes downgrading the engine by receiving the engine fault flag and downgrading the motor by receiving the motor fault flag. Introducing torque monitoring in the vehicle control strategy to prevent the generation of uncontrollable torque due to failure and avoid the vehicle being in dangerous states such as unexpected acceleration or unexpected deceleration.