Maxwell电磁力驱动快速刀具伺服系统轨迹跟踪控制

Trajectory Tracking Control of a Fast Tool Servo System Driven by Maxwell Electromagnetic Force

  • 摘要: Maxwell电磁力驱动避免了压电驱动器行程小和音圈电动机驱动力不足的固有缺点,在快速刀具伺服(fast tool servo,FTS)系统中极具应用前景。针对Maxwell电磁力驱动FTS系统的高性能轨迹跟踪问题,提出以阻尼控制改善被控对象基本动力学特性,再基于频域整形方法优化设计高增益PID控制器,实现FTS的高带宽控制。为降低阻尼控制系统名义模型阶次,提出以比例增益近似替代阻尼控制系统传递模型,并结合扰动观测器对前馈增益未建模部分进行估计与主动补偿。以所设计的一种Maxwell电磁力驱动FTS为对象,借助扫频激励辨识了系统名义模型,并据此设计了各控制器参数。试验测试结果表明:所设计的阻尼控制器可以有效抑制系统谐振并提高PID控制系统带宽,基于扰动观测的前馈补偿器的引入可大幅降低轨迹跟踪误差。最终对25 μm幅值、25 Hz频率的谐波轨迹跟踪获得了±0.16 μm的误差。

     

    Abstract: Maxwell electromagnetic actuator can overcome the inherent small stroke limitation of piezoelectric actuators as well as the insufficient driving force of voice coil actuators, and tends to be very promising for applying in fast tool servo (FTS). To achieve a high-performance trajectory tracking, a damping controller is designed for the FTS to modify its basic dynamics, and a high-gain PID controller is accordingly developed through the loop-shaping method to gain a wide bandwidth. To decrease the model order of the damped control system, a static gain is adopted as the feedforward compensator where the unmodeled part is estimated and compensated by a disturbance observer. By conducting sweep excitation of a designed FTS actuated by the Maxwell electromagnetic force, the nominal transfer function is identified, and the controller parameters are accordingly determined. Experiment result demonstrates that the designed damping controller can effectively suppress the resonance and improve the closed-loop bandwidth of the FTS, and the disturbance observation-based feedforward compensation can significantly reduce the trajectory tracking error. Finally, the obtained motion error is about ±0.16 μm for tracking a harmonic trajectory with 25 μm amplitude and 25 Hz frequency.

     

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