Development and assessment of large stroke piezo-hydraulic actuator for micro positioning applications

Abstract The primary concern with micro-positioning systems is to achieve precise positioning, coupled with the broad stroke of actuation. Over the past few years, the advancement in piezoelectric technology has adequately fulfilled the purpose of precision positioning applications. The advantages of accurate control and positioning accuracy, compactness, minimum wear and tear, enhanced stiffness in conjunction with better dynamic response has led to the extensive utilization of piezoelectric actuators as a precision positioning source. However, the inadequacies of limited positioning stroke, together with the inherent hysteresis hinder the performance of piezoelectric actuators. The present work aims at the development of a new piezo-hydraulic actuator for overcoming the disadvantage of limited stroke of the piezoelectric actuator through hydraulic displacement amplification mechanism (HDAM). The proposed piezo-hydraulic actuator works based on differential area principle and Pascal's law. The prototype of the piezo-hydraulic actuator incorporates amplified piezo actuator (APA) as a primary actuator which deflects a piston causing the fluid to get displaced from larger cross-section to smaller cross-section. This intern leads to amplified motion. An electromechanical model coupled with the Bouc-Wen hysteresis model is implemented in the present work to simulate the displacement and force characteristics of the proposed piezo-hydraulic actuator. The experimental work involved the fabrication and characterization of the proposed piezo-hydraulic actuator. The experimental results are validated by comparing with the simulated results obtained from the mathematical model. The maximum amplification factor of the piezo-hydraulic actuator achieved is about 77.00, which is in close agreement with the theoretical amplification factor of 79, with the error of about 2.53%. When the piezo hydraulic actuator is actuated at 150 V, the amplified piezo actuator achieves a maximum deflection of 129.02 μm which gets amplified to a value of about 9934.69 μm through hydraulic amplification. The fabricated prototype of piezo-hydraulic actuator achieves maximum blocking force of 0.5 N at 150 V.