Research On Hierarchical Coordinated Control Strategy For Hub-motor Hydraulic Hybrid Vehicle

The heavy commercial vehicle plays an important role in the development of society construction.A hub-motor hydraulic hybrid system is proposed by adding hub-motors in the driven wheels of conventional vehicle and adding components include a hydraulic pump,hydraulic valves and so on.The passing ability of vehicle on the bad road can be improved by this system with bigger traction of vehicle.Depending on the road conditions and the driver's operation,the hydraulic system get involved in specific modes and is coupled to the mechanical drive system through the road.To make fully use of the advantages of the system,it is necessary to develop a control strategy which can ensure an optimal energy consume based on the improvement of dynamic performance.The main content of this dissertation includes the following elements:Firstly,a hierarchical architecture is proposed for the hub-motor hydraulic hybrid vehicle,which include the adaptive layer,the subsystem coordination layer and the actuator layer.A simulation system for hub-motor hydraulic driving vehicle is constructed in AMESim according to characteristics of the control strategy,so as to provide closed-loop simulation environment for the conduction of comprehensive control strategy.The simulation system consists of vehicle body model,engine model,hydraulic pump model,hydraulic motors model and tire model,etc.Secondly,research on hierarchical coordinated control strategy.Road properties are identified using fuzzy controllers respectively in the control strategies of the adaptive layer.The road conditions adaptability is improved as the vehicle work mode changes according to the properties of road and the operations of driver.Then,rules are extracted from wheel speed coordination and acceleration energy consumption optimization in the control strategies of subsystem coordination layer.Based on the study on response characteristic of hydraulic variable pump control system and detailed modeling,the control strategies of pump control is development to make accuracy control of pump displacement.The Triple-step control shows superiority compared with the PID control and feedback-feedforward control.Finally,the experimental verification is conducted for simulation and hardware in loop.The offline simulation platform is designed to verify the improvement of dynamic performance,and hardware in the loop simulation platform is designed and the two methods of pump displacement control is compared to improve coordination algorithm,results show the vehicle get better energy consumption with acceleration energy consumption optimization algorithm.