Pneumatic and tendon actuation coupled muti-mode actuators for soft robots with broad force and speed range

Broad output force and speed ranges are highly desired for actuators to endow soft robots with high performance, thereby increasing the range of tasks they can accomplish. However, limited by their low structural stiffness and single actuation method, most of the existed soft actuators are still difficult to achieve a broad force and speed range with a relatively compact body structure. Here, we propose a pneumatic and tendon actuation coupled soft actuator (PTCSA) with multiple actuation modes, mainly composing of a multi-joint thermoplastic polyurethanes (TPU)-made skeleton sealed in a film sleeve. The TPU skeleton with certain structural stiffness combined with soft joints allows PTCSA to output small force and respond rapidly under pneumatic actuation, as well as output high force and flexibly regulate response speed under tendon actuation, therefore achieving a broad force and speed range with a compact structure. The multiple modes constructed from the two actuation methods with different force and speed properties can cover diverse application scenarios. To demonstrate its performance, PTCSA is further used to construct a soft robotic arm (with a maximum lifting speed of 198 degrees/s and can easily lift a load of 200 g), an inchworm-inspired wheel-footed soft robot (moves at a high speed of 2.13 cm/s when unload or pulls a load of 300 g forward), and a soft gripper (can grasp diverse objects, from 0.1 g potato chips to an 850 g roll of Sn-0.7Cu wire, from a high-speed moving tennis ball to an upright pen). This work indicates the potential of combining multiple complementary actuation methods to improve the force and speed range of soft actuators, and may provide inspiration for related research.