宏微复合运动平台的自抗扰控制研究

摩擦是影响机械导轨运动平台精度的主要原因.宏微复合运动平台将无摩擦的柔性铰链与直线平台结合在一起,利用柔性铰链的弹性变形补偿摩擦死区.然而,柔性铰链的固有频率低,其非线性弹性振动严重影响微平台定位精度.为此,本文设计视弹性振动为扰动的自抗扰控制策略,该方法避免了建立非线性弹性振动精准数学模型的困难,利用扩张状态观测器主动估计弹性振动及不确定性,并在微平台位置环补偿之,以保证微平台定位精度.与此同时,在控制律中加入加速度前馈以提高系统响应速度.对于宏平台,采用PID控制作为宏平台位置环的控制策略,并通过宏微双级驱动方式补偿受机械导轨非线性摩擦带来的影响.实验对比结果表明,自抗扰控制在受非线性弹性振动影响时,其抗扰性能、跟踪性能优于传统的PID控制,可保证微平台良好的定位精度.

On active disturbance rejection control of macro-micro composite motion platform

Friction is the main reason that affects the accuracy of mechanical guide motion platform. The macro-micro composite motion platform combines the frictionless flexible hinge with the linear platform, and compensates the friction dead zone by the elastic deformation of the flexible hinge. However, the low natural frequency of flexible hinges leads to nonlinear elastic vibration, which causes poor platform positioning accuracy. Therefore, this paper presents a strategy of active disturbance rejection control (ADRC) considering elastic vibration as a disturbance. Instead of finding an accurate mathematical model, this method uses the extended state observer (ESO) to actively estimate the elastic vibration and uncertainty, and compensates the elastic vibration in the micro-platform position loop controller to ensure the positioning accuracy. Also, acceleration feedforward is added to the control law to improve the response speed of the system. On the macro platform, PID control is used as the control strategy of the macro platform position loop while the nonlinear friction of the mechanical guide is compensated by the macro-micro dual-stage drive. Experimental comparison results show that the ADRC control ensures a good positioning accuracy of the micro platform and is superior to the traditional PID control in anti-disturbance and tracking performance under nonlinear elastic vibration.