电子机械制动执行器的摩擦力矩和能耗分析

为了实现在设计阶段对系统摩擦力矩的合理预估,提高执行器性能预测的准确性,以行星齿轮滚珠丝杆式电子机械制动执行器为研究对象,分析系统摩擦的主要来源及其对执行器性能的影响;建立执行器系统动力学模型和摩擦力矩模型,将理论计算与实验相结合,对模型参数进行了辨识,基于理论计算和实验辨识结果的对比分析讨论了两者存在差异的原因;同时分析摩擦模型参数对制动间隙消除时间和最大制动夹紧力的影响,各部件摩擦对系统摩擦力矩的影响及其随转速和载荷的变化规律,以及紧急制动过程中执行器产生的摩擦能耗.结果表明:影响制动间隙消除时间的摩擦主要来源于电机和滚珠丝杆;影响制动夹紧能力的摩擦主要来源于滚珠丝杆、电机和推力轴承,随着制动夹紧力的增加滚珠丝杆和推力轴承对系统摩擦的影响增大,而电机的影响显著降低;紧急制动过程中,执行器产生的有效力矩传递比仅为73.56%,摩擦能耗高达48.1%.

Calculation and Analysis of Friction Torque and Energy Dissipation of Electromechanical Brake Actuator

To realize the rational prediction of system friction torque in the design phase and improve the correctness of performance prediction for the actuator, taking the electronic mechanical brake (EMB) actuator with planetary gear and ball screw as the study object, the main source of system friction and its influence on the EMB actuator were analyzed. Firstly, the dynamic model and friction torque model were established according to the structure and load of EMB. The prediction of the friction torque model was compared with the experimental results, and the reason of the difference between the experimental and predicted results was discussed. Based on the dynamic model and friction torque model, the influence of parameters in the friction torque model on the gap closing time and maximum clamping force was studied. The energy dissipation during braking with the maximum clamping force was calculated. The proportion of the friction torque at each component and the influence of rotation rate and clamping force on these friction torques were analyzed. It was found that the frictions which influence the gap closing time come from ball screw and motor, while the frictions which affect the capability to clamp are generated by ball screw, motor and thread bearing. With the increase of the clamping force, the influence of the frictions due to ball screw and thread bearing increased significantly, while the impact of friction from motor decreased greatly. During emergency braking, the effective torque transfer ratio was 73.56%, and the energy dissipation ratio was 48.1%.