闭式泵控液压-机械直线执行器的离散PID控制

Discrete PID Control of Closed Pump Control Hydraulic-mechanical Linear Actuator

液压驱动因其功率密度高、直线输出力大,广泛应用于装备制造领域。但非对称液压缸受两腔面积差的制约,在阀控系统中需要用非对称阀控制,在闭式泵控系统中需要增加额外的补油回路。而电动缸具有对称的输出力和较高的能效,解决了非对称液压缸面积差的影响,但功率密度低使电动缸难以满足低转速大扭矩的高负载工况。针对上述问题,提出了液压回转与机械直线转换相结合的新型驱动方式,采用闭式泵控马达驱动滚珠丝杠带动活塞杆动作。由于在闭环控制中单一的PID难以满足全负载工况,系统采用局部最小化优化方法自动寻找最优PID参数,生成离散PID图表并根据负载自动选择对应的PID参数控制以减小负载干扰。结果表明:离散PID自动调定的系统能避免负载变化产生较大干扰,在变负载和目标位移情况下,离散PID参数自动调整的响应曲线阶跃下降和上升的稳态误差最大分别为4.5 mm、3.0 mm。

Hydraulic drive has high power density and large linear output force,and is widely used in equipment manufacturing industry.However,the asymmetric hydraulic cylinder is restricted by the difference of the area of the two cavities,so it needs to be controlled by the asymmetric valve in the valve control system,and additional oil filling circuit needs to be added in the closed pump control system.The electric cylinder has symmetrical output force and high energy efficiency,which solves the influence of asymmetric hydraulic cylinder area difference,but the low power density makes the electric cylinder difficult to meet the high load condition of low speed and high torque.In order to solve these problems,a new driving mode combining hydraulic rotation and mechanical linear conversion is proposed.The ball screw is driven by the closed pump control motor to drive the piston rod.Since it is difficult for a single PID to meet the full load conditions in the closed-loop control,the system uses the local minimization optimization method to automatically find the optimal PID parameters,generate discrete PID charts,and automatically select the corresponding PID parameters according to the load to reduce the load interference.The results show that the system of discrete PID automatic adjustment can avoid large disturbance caused by load change.Under the condition of variable load and target displacement,the maximum steady-state error of the response curves of discrete PID parameter automatic adjustment is 4.5 mm and 3.0 mm,respectively.