Search

We develop a rotary motor to reduce backward motion in stick–slip with an active clamp mechanism. Backward motion refers to the undesired movement observed when operating a rotary stick–slip motor powered by a piezoelectric actuator under actual conditions, where the rotor rotates in the opposite direction to the intended rotation. This could cause imprecision and inaccurate motion. The conventional stick–slip motor relies on contact with the rotor to induce rotation. The proposed active clamp mechanism adjusts the contact distance with the rotor, ensuring contact is maintained only when the rotor is rotating. This helps reduce backward motion. Additionally, implementing this mechanism using the conventional method requires one stick–slip module for rotation and two inchworm drive modules for clamping. In contrast, the proposed mechanism consists of a single module each for the driving actuator and clamping actuator. A preliminary model with a dimension of 34 × 27 mm was constructed for experimentation. Through the experiments, it was confirmed that the proportion of backward motion relative to the initial movement in one step decreased by approximately 20%. Furthermore, with the reduction in backward motion, the rotational displacement per step was confirmed to improve by about twice, increasing from 17 to 33 millidegrees. [ABSTRACT FROM AUTHOR]

A thin film shape memory alloy bimorph actuator developed by depositing CuAlNi shape memory alloy (SMA) on a curved Kapton polyimide sheet substrate can be used in position control without any biasing element or external sensor. Self-sensing capability makes SMA best suited for small size and low weight applications in the fields of medicine and aerospace. The dynamic behaviour of the bimorph actuator is analyzed with various inputs such as step, pulse and sine voltages, with and without load. The actuation of SMA bimorph exhibits nonlinear hysteresis. Also, the results show that some oscillations are present during heating when the bimorph is not loaded and these oscillations are absent/eliminated when under load. The SMA bimorph actuator's performances are approximated as the ARX441 model using the system identification technique. Further, the self-sensing model of the SMA bimorph actuator is developed using polyfit and ANN techniques and verified with the actual values. [ABSTRACT FROM AUTHOR]