Research On Emergency Braking Control Methods Of Motor For An Electric Bus

Recent years,with the emphasis on global warming and environmental protection,the development of new energy vehicles has come into a new stage.Many countries and cities take public transportation as their primary development goal.On this basis,electric buses have also become the focus of development.At the same time,active safety technologies,such as advanced emergency braking system,are gradually marching towards the market.Therefore,an advanced emergency braking control algorithm is designed and simulated based on an electric bus.Then proposing a sliding mode control algorithm to improve emergency braking performance and a compensate algorithm to control the torque oscillation of the elastic half-shaft system on an electric bus.Firstly,according to the characteristics of an electric bus,simulations of an advanced emergency braking control algorithm is executed.Based on the estimated collision time,an early warning braking and an emergency braking triggered time are determined.And the stationary and moving targets are simulated and analyzed to verify the effectiveness of the algorithm.Then,the factors which may affect the results of the advanced emergency braking,including self-vehicle speed,initial distance between the two vehicles,emergency braking trigger time and the secondary warning time,are analyzed.After the analysis,the recommended values of emergency braking trigger time and the secondary warning time are given.Next,the possibility of the motor participating in anti-lock braking is explored.Then,a sliding variable structure control algorithm is proposed.Based on this algorithm,simulations and hardware-in-the-loop tests are carried out.In order to verify the control results,a motor Proportion-Integration-Differentiation control strategy is also recommended and tests are executed under the same scenarios.Test results show that the emergency braking performance and the braking comfort are both improved comparing to the pure air-pressure control strategy and the motor PID control strategy.Finally,an elastic half-shaft model is established with the purpose of exploring the effects of an elastic half-shaft on emergency braking performance.After determining the effects of the elastic half-shaft,a compensation control algorithm is developped to alleviate the oscillation of the transmitted torque and the control difficulties caused by the elastic half-shaft.After compensation,both the torque oscillation and braking comfort are improved greatly.At the same time,the motor torque exit speed is adjusted owing to the influence during the motor exit process.With the adjustment,the torque oscillation during the exit process is alleviated according to the simulation results,which verifies the feasibility and the effectiveness of the developed control algorithm.