Consensus Control Strategy For Heavy-duty Vehicles Platooning With Hydraulic Retarder

Cooperative adaptive cruise control(CACC)can make heavy-duty vehicles platoon to perform cooperative driving with small inter-vehicle distance by vehicle-tovehicle or vehicle-to-infrastructure communication,which greatly improves the traffic efficiency and the vehicle fuel economy.However,most researches on CACC for heavy-duty vehicles platooning mainly focus on improving the fuel economy and neglect the control performance of hydraulic retarder and the vehicle following performance during communication loss.Employing the retarder can provide the additional braking force for heavy-duty vehicles,which effectively reduces the burden of the vehicle braking system and improves the safety of heavy-duty vehicles.To solve this problem,this thesis proposes a CACC switched hierarchy control strategy for heavy-duty vehicles platooning to improve its fuel economy,the control performance of hydraulic retarder,and the vehicle following performance during communication loss.In the research of the lower-level CACC control strategy,a simulation model of a hydraulic retarder whose oil volume rate is controlled by a pneumatic system is built,and a retarder torque control strategy is also proposed.For verifying the control strategy through simulations,the hydraulic retarder simulation model is built and verified by experiments.Then,a retarder torque control strategy with a compensator is designed to reduce the delay of retarder torque and guarantee the vehicle speed tracking performance in heavy-duty vehicle longitudinal control.Then,an upper-level CACC switched control strategy is proposed,namely,different upper-level CACC control strategies will be implemented in the normaldriving situation,the retarder-running situation and the unstable communication situation,respectively.In the normal communication area,a CACC control strategy for optimizing the fuel economy and the control performance of hydraulic retarder in a heavy-duty vehicle platoon is proposed,which includes a dynamic-programming based platoon control method,a model-predictive-control(MPC)based vehicle control method,and a retarder robust control method.The dynamic-programming based platoon control method is designed to optimize the fuel economy and travel efficiency of the platoon,which can calculate the optimal vehicle speed profile and the retarder activated area for the platoon.In the normal-driving situation,the MPC based vehicle control method is implemented in each vehicle to simultaneously track the optimal vehicle speed profile and the inter-vehicle spacing policy.In the retarder-running situation,the retarder robust control method is deployed in each vehicle to attenuate the disturbance of retarder oil's temperature on the accuracy of retarder torque control and achieve the tracking of the inter-vehicle spacing policy.In the unstable communication area,a CACC control strategy for handling longterm communication loss is proposed.A reliable predecessor-following CACC control method is designed first.Then,based on the “current” model,an adaptive Kalman filter(AKF)is proposed to estimate the preceding vehicle's acceleration.When the communication loss happens,the estimated preceding vehicle acceleration can be used to substitute the desired preceding vehicle acceleration from communication in the predecessor-following CACC control method,which can maintain the vehicle following performance during communication loss.And the CACC control strategy is verified by simulations and mobile robot experiments.At last,to verify the effectiveness of the whole CACC switched hierarchy control strategy,co-simulations between the lower-level CACC control strategy and the upperlevel CACC control strategy are conducted in both homogeneous and heterogeneous platoon.The simulation results show the CACC switched hierarchy control strategy proposed in this thesis not only effectively improves the fuel economy of the platoon but also maintains the control performance of hydraulic retarder and the vehicle following performance during communication loss.