基于关节力矩补偿的液压机械臂末端力软测量

Terminal Force Soft Sensing of Hydraulic Manipulator Based on Joint Torque Compensation

为满足液压机械臂在复杂环境下高精度的作业要求,需使其具备一个精确的力测量系统。由于液压机械臂工作环境复杂且末端接触负载大,力传感器容易受到破坏,因此,针对液压机械臂无末端力传感器的末端力精确感知的难题,以3自由度液压重载机械臂为研究对象,提出了基于关节力矩补偿的液压机械臂末端力软测量方法。本研究通过有限傅里叶级数模型设计激励轨迹,并采用递推最小二乘法辨识机械臂动力学参数。以非线性摩擦力矩模型代替库伦粘性摩擦模型,提升机械臂动力学模型精度。建立神经网络关节力矩补偿模型,减小不确定因素对液压机械臂动力学模型精度的影响。搭建AMESim/Simulink联合仿真模型,设计液压机械臂末端运行三角形轨迹,验证了本研究提出的动力学模型精度较高。分别在液压机械臂末端的水平方向和竖直方向施加500 N的恒力负载和0~500 N的变力负载,在恒力负载下,水平方向和竖直方向的末端力软测量精度分别为4.84%、2.79%;变力负载下,水平方向和竖直方向的末端力软测量精度分别可达5.73%、4.81%。通过与未优化前的末端力软测量精度对比,验证了本研究提出的基于关节力矩补偿的液压机械臂末端力软测量模型可有效提高末端力软测量的精度。

To meet the requirements of the high-precision operation of the hydraulic manipulator in a complex environment,it is necessary to equip it with an accurate force measurement system.Due to the large and complex endeffector contact force against the working environment,the force sensor is vulnerable to damage.Therefore,focusing on the accurate measurements of the terminal force with force sensorless,this paper proposed a force softsensing method of hydraulic manipulator based on joint torque compensation,taking 3-D of hydraulic manipulator as the research object.A finite Fourier series model was used to design the excitation trajectory,and the recursive least squares method was used to identify the dynamics parameters of the manipulator.The nonlinear friction torque model was used to replace the Coulomb viscous friction model to improve the precision of manipulator dynamics model.A neural network joint torque compensation model was established to reduce the influence of uncertain factors on the precision of the dynamics model.The AMESim/Simulink co-simulation model was built to design the triangular trajectory of the hydraulic manipulator end-effector,which verified the high accuracy of the dynamic model proposed in this research.A constant force load of 500 N and a variable force load of 0~500 N were applied to the horizontal and vertical direction of the end-effector respectively.Under the constant force load,the soft sensing accuracy of the end force in the horizontal and vertical directions is 4.84%and 2.79%,respectively.Under the variable force load,the accuracy of the soft sensor can reach 5.73%in the horizontal direction and 4.81%in the vertical direction.By comparing the end force soft sensor accuracy with that before optimization,it is verified that the force soft-sensing model of hydraulic manipulator based on joint torque compensation can effectively improve the accuracy of end-effector contact force.