PARALLEL-COUPLED MICRO-MACRO ACTUATORS

This paper presents a new actuator system consisting of a microactuato r and a macro-actuator coupled in parallel via a compliant transmissio n. The system is called the parallel-coupled micro-macro actuator or P aCMMA. In this system, the micro-actuator is capable of high-bandwidth force control owing to its low mass and direct-drive connection to th e output shaft. The compliant transmission of the macro-actuator reduc es the impedance (stiffness) at the output shaft, and increases the dy namic range of force. Performance improvement over single-actuator sys tems was expected in force control, impedance control, force distortio n, and transient impact force reduction. Several theoretical performan ce limits are derived from the saturation limits of the system. A cont rol law is presented A prototype test bed was built and an experimenta l comparison was performed between this actuator concept and two singl e-actuator systems. A set of quantitative measures is proposed and the actuator system is evaluated against them with the following results: force bandwidth of 56 Hz, torque dynamic range of 800:1, peak torque of 1,040 mNm, and minimum torque of 1.3 mNm. Peak impact force,force d istortion, and back-driven impedance of the PaCMMA system are shown to be better than either of the single-actuator configurations considere d.