A small locust inspired actuator driven by shape memory alloys and piezoelectric strips

In order to realize walking and obstacle crossing in a complex terrain, a small locust inspired soft actuator is designed and manufactured. Its appearance size and mass are 80 mm x 40 mm x 45 mm and 6 g, respectively. This actuator can realize both jumping and linear motions, mainly consisting of two shape memory alloy (SMA) springs, four flexible Polyvinyl chloride layers, and four piezoelectric (PZT) bimorphs. The former two materials (SMA and PZT) constitute the catapult mechanism for jumping and recovering; the latter one (PZT) is used as driving legs for walking. A kinematic model is established for motion analysis and parameter optimization, in order to make the actuator keep a stable jump. The calculated and measured results show that it can realize a jump of one body length, crossing an obstacle of more than 15 mm high. It takes 13 s from taking off to recovering for continuous movement. In addition, the maximum linear speed is 82.5 mm s(-1) at 160 Vp-p. This actuator with multi-mode locomotion has the characteristics of light weight, stable landing, status recovery, and continuous movement, suitable for exploration and reconnaissance in narrow space.