基于混合驱动的大行程快速刀具伺服设计与控制

Design and Control of a Hybrid Actuation Based Long Range Fast Tool Servo

为获得高精度大行程快速刀具伺服(Long-range fast tool servo, LFTS)系统,以柔性铰链为运动导向机构,提出一种基于洛伦兹电磁力与压电混合串联驱动的LFTS系统构成策略。对于该混合驱动,基于洛伦兹力的音圈电机用于实现大行程运动,而高频响压电则对其进行高精度动态补偿。针对压电驱动,为提高系统输出刚度及寄生运动抑制能力,提出一种改进的具有完全对称构型的桥式柔性放大机构。两种驱动的垂直布置构型及压电驱动的完全对称性有效降低了驱动间动力学耦合。基于试凑法和智能优化算法,结合机?电?磁理论模型分别优化获得了音圈电机及压电驱动系统关键参数,并采用有限元仿真验证了设计的正确性。为获得高精度运动跟踪,提出音圈电机开环逆动力学控制及压电驱动闭环补偿LFTS整体运动误差的控制策略,借助所辨识系统动力学模型最优设计了相应控制器。最终,通过试验样机开闭环性能测试,验证了系统设计与控制策略的有效性。

To achieve a long-range fast tool servo(LFTS) with high motion accuracy, a hybrid actuation strategy with compliant mechanisms for motion guidance is proposed through serially combining the Lorentz electromagnetic force-based voice coil motor(VCM) and a piezoelectric actuator(PEA). With the LFTS, the VCM is employed for the effective generation of long stroke motions, and the PEA featuring high response speed is adopted for dynamics compensation of the VCM actuation system. Target at the output stiffness improvement and parasitic motion elimination, an improved bridge-type flexure amplifier featuring a totally symmetric configuration is proposed for motion amplification and guidance of the PEA. Herein, the mutually perpendicular arrangement of the two-actuation system as well as the symmetric structure of the flexural amplifier may contribute to the decoupled dynamics of the LFTS. Taking advantage of the developed analytical model coupling the magnetic, electric, and mechanical properties of the LFTS, structural parameters are optimally determined through both trial-error and evolutionary computation-based method. Finite element analysis is further adopted to verify the effective of the modelling and system design procedures. To obtain high accurate trajectory tracking, the dynamics inversion based open-loop control strategy is proposed for the VCM, and a closed-loop PEA control system using the total output of the LFTS as the feedback signal is further employed for error compensation of the VCM system. The optimal controller is designed in the frequency domain by referring to the identified system nominal models. Finally, the effectiveness and superiority of the LFTS are demonstrated through both open-loop and closed-loop testing of the LFTS prototype.