This paper describes an analytical design model for a layered piezo-composite unimorph actuator and its numerical and experimental verification using a LIPCA (lightweight piezo-composite curved actuator) that is lighter than other conventional piezo-composite type actuators. The LIPCA is composed of top fiber composite layers with high modulus and low CTE (coefficient of thermal expansion), a middle PZT ceramic wafer, and base layers with low modulus and high CTE. The advantages of the LIPCA design are to replace the heavy metal layer of THUNDER by lightweight fiber-reinforced plastic layers without compromising the generation of high force and large displacement and to have design flexibility by selecting the fiber direction and the number of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use a resin prepreg system. A piezo-actuation model for a laminate with piezo-electric material layers and fiber composite layers is proposed to predict the curvature and residual stress of the LIPCA. To predict the actuation displacement of the LIPCA with curvature, a finite element analysis method using the proposed piezo-actuation model is introduced. The predicted deformations are in good agreement with the experimental ones.
A method for the shape control of double-plate structures is presented. The model consists of three plates and many ribs. Two of the plates are placed parallel to each other and clamped at one edge. The third plate connects the edges of the parallel plates that are opposite the fixed edge. Each rib is made of shape memory alloy (SMA) wire and connected to the parallel plates. Each rib generates a concentrated force and applies it to the plates in perpendicular and oblique directions. Piezoceramic patches are bonded onto the plates and exert concentrated moments upon the plates at several locations. The object of this research is to generate various structural shapes by combining the concentrated forces from the SMA wires and moments from the piezoceramic patches. The possibility of shape control is examined by finite element analysis. Numerical results show the capability of shape control by SMA wires and piezoceramics in the elastic range. Experimental results on shape control are presented to compare with the numerical results.
The rapid advancements in 3D printing technologies offer immense design flexibility and the ability to create complex structures with high resolution. Using these cutting‐edge technologies and materials (i.e., a polylactic acid and fused deposition modeling), a novel design principle is introduced for a fingerless gripper, achieved through topological optimization. To realize the grasping capabilities, a coiled garter spring made of shape memory alloy (SMA) is incorporated at the end of the flexure beams. Based on the experiments, it is found that the gripper is very quick to respond, taking only 5 s to heat up and 15 s to cool down. This promising performance is achieved by carefully balancing the net force differential between the restoring force of the flexure beam and the force of the SMA coiled garter spring. In addition to its responsiveness, the gripper demonstrates a high force‐to‐weight ratio of 5.3, allowing it to lift heavy payloads of up to 4.91 N (0.5 kgf) despite its lightweight design (total weight of 94.2 g). Overall, this work showcases the potential of 3D printed fingerless grippers in terms of high holding strength, lightweight, low cost, and simple fabrication.
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