无速度传感器音圈式快速刀具的阻尼闭环控制

Damping Feed-forward Closed-loop Control for Voice-coil Fast Servo Actuator without Velocity Sensor

针对音圈式快速刀具阻尼较小、超调较大的开环特性,经典控制采用速度环和位置环双闭环反馈控制,但速度传感器增加了系统的复杂度,且易带来附加噪声。基于二阶积分器串联系统的最速控制方法,提出了采用最速过渡环节调节输入或控制信号阻尼,进而改善无速度传感器的输出阻尼前馈控制方法,设计了相应闭环控制方案,在DSP控制平台上进行刀具动态性能测试,并进行了球形透镜阵列的加工实验。实验结果表明:所提出的控制方法能有效改善快速刀具的阻尼特性,刀具方波响应超调约4%,上升时间仅为3 ms,所加工球透镜阵列具有良好的面形精度及表面粗糙度,PV值约为0.228λ,表面粗糙度Ra小于15 nm。

Low damping and large overshoot of voice-coil fast servoactuator（VCA） were its natural open-loop characteristics.In order to improve the dynamic performance and steady accuracy of VCA,a double closed-loop feedback control structure was used with a velocity loop and a position loop in classical control strategy.It was inevitable to add complexity and bring additional noise to fast tool servo（FTS） system for the use of velocity sensor.Based on the time-optimal control idea of the two order integrator series system,the damping feed-forward control method was put forward.The output damping could be improved by modulating the damping of input signal or the controlling signal through a time-optimal process（TOP） with no use of velocity sensor.The corresponding controlling projects were designed,dynamic performances were tested and typical microlens array was fabricated.The testing and experimental results indicated that the proposed damping feed-forward control method could improve the system damping effectively,the overshoot of square wave exciting response was 4% and the setting time was only 3ms.The machined workpiece had better form accuracy and surface finish.The PV value of form error was only 0.228λ and the Ra of surface finish was less than 15nm.