Design, modeling, and control of coaxial integrated macro–micro composite actuator with high-precision and long-stroke

This paper presents a coaxial integrated macro–micro composite actuator. The macro-actuator of the macro–micro composite actuator is similar to a moving coil type voice coil motor, and a giant magnetostrictive actuator is installed coaxially inside it as a micro-actuator. In this work, kinetic models are established for both the macro-actuator and micro-actuator, and based on the models, an automatic disturbance rejection controller is adopted to control the macro-actuator, and a fuzzy sliding mode controller is adopted for the micro-actuator. In order to verify the actual performance of the proposed macro–micro composite actuator, a prototype was fabricated, and experimental results show that the macro-actuator can achieve a 10 mm step positioning error of 9 μm and a 30 mm step positioning error of 11 μm under a load of 1 kg. The resolution of the minimum PWM square wave change identification of the controlled micro-actuator is 0.047 μm, and the minimum displacement resolution of the micro-actuator is 0.15 μm. The micro-actuator is capable of achieving 1 μm steps with no displacement overshoot. In addition, when the positioning distance is 5 μm, there is a small amplitude overshoot of 0.18 μm. The final positioning accuracy of macro–micro composite positioning is within 350 nm.