Abstract: 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.

Key words: fast tool servo, hybrid actuation, compliant mechanism, optimal design, trajectory tracking