面向混联液压机械臂的高精度运动控制方法

High Precision Motion Control Method for Hybrid Hydraulic Manipulator

针对串并混联液压臂中因结构耦合和系统非线性导致其末端位置控制精度差的问题,基于虚拟分解建模方法和液压系统控制理论,提出了一种混联液压臂的高精度运动控制方法。该方法通过对系统进行精确建模,消除了传统液压臂控制方法由于忽略结构耦合和系统非线性而引入的误差,从而提高了运动控制精度。首先,将混联液压臂复杂的串并联驱动结构分为摆动缸驱动的开链结构、活塞缸驱动的闭链结构和活塞缸驱动的并联结构3类,并根据3类结构的特征将机械臂进一步虚拟分割成简单的子系统;然后,根据刚体动力学方程和流量连续方程分别建立了各子系统的动力学模型和液压执行器驱动模型,通过引入基于模型的前馈控制量和实时位置误差的反馈控制量设计了面向混联液压机械臂的高精度运动控制器。在七自由度混联液压机械臂试验平台上对该方法的有效性进行验证,结果表明:与传统PID控制器相比,采用该方法后液压臂末端在x和z方向的误差分别从59.63mm和19.6mm降低至11.17mm和6.48mm,仅为PID控制器的18.73%和33.06%,有效提高了混联液压机械臂的运动控制精度。

To address the problem of low position control accuracy of the end-effector in a series-parallel hybrid hydraulic manipulator due to structural coupling and system nonlinearity,a high-precision motion control method for the hybrid hydraulic manipulator was proposed based on virtual decomposition modeling method and hydraulic system control theory.This method eliminated the errors introduced by traditional hydraulic manipulator control methods that ignore structural coupling and system nonlinearity by accurately modeling the system,thereby improving the motion control accuracy.Firstly,the complex series-parallel driving structure of the hybrid hydraulic manipulator was divided into three types:open-chain structure driven by swing cylinder,closed-chain structure driven by piston cylinder,and parallel structure driven by piston cylinder,and the manipulator was further virtually decomposed into simple subsystems based on the characteristics of these three types of structures.Then,dynamic models of each subsystem and drive models of the hydraulic actuator were established based on rigid body dynamics equations and flow continuity equations,and a high-precision motion controller for the hybrid hydraulic manipulator was designed by introducing model-based feedforward control and real-time position error feedback control.The effectiveness of this method was verified on a seven-degree-of-freedom hybrid hydraulic manipulator test platform.The results showed that compared with a traditional PID controller,the end-effector errors of the proposed method in x and z directions were reduced from 59.63 mm and 19.6 mm to 11.17 mm and 6.48 mm respectively,which were only 18.73%and 33.06%of a PID controller’s error,effectively improving the motion control accuracy of the hybrid hydraulic manipulator.