As a classical type of smart materials, shape memory alloys (SMAs) are of high energy density, light weight, and low actuating voltage, and therefore are of great potential to be used as actuators for robots. Major challenges in controlling an SMA-driven soft robot are the limited bandwidth and in cases with external loads. Active cooling has been demonstrated to dramatically increase its bandwidth, but external load may cause severe inaccuracy in the system modeling. Controllers that do not rely on accurate modeling of the SMA-driven soft robot is essential. In this article, we designed an elastomeric soft robotic tentacle actuated by three pieces of SMA springs with both active heating (Joule heating) and active cooling (compressed air). We proposed a multi-input-multi-output controller that directly uses the heating and cooling states of the three SMAs to control the tentacle's bending posture in three-dimensional (3-D) space. The successful implementation of the controller is attributed to a novel dual-channel control algorithm that integrates the bending motion control and swing motion control, and a state-machine controller for coordinating the three SMAs' actuations to achieve robust swing motion control. The system with such hardware and control algorithm was capable of performing bending motions with maximum actuating speed$ > $90$^\circ /$s, deactuating speed$ > $25$^\circ /$s, closed-loop motions with rapidity (6–41$^\circ /$s for heating, 4–19$^\circ /$s for cooling), accuracy (steady-state error$ < $0.1$^\circ$for no load, 0.13$\%$of the full range; steady-state error$ < $1.2$^\circ$with load of 1 bodyweight, 1.6$\%$of the full range), and load-bearing capability (dynamic load: 1 bodyweight, static load: 8.8 bodyweights). Besides, the tentacle achieved efficient motion tracking by coordinating the bending and swing motion through the controller, for both predefined trajectories and random trajectories. We demonstrated a remotely controlled 360$^\circ$image scanning of a room using our proposed robotic tentacle equipped with a camera at its top end to intuitively show its performances. We believe this work will advance the design and control of SMA-driven soft continuum robots for potential uses in surgery and explorations of unknown areas.

Recently, various soft universal grippers have been developed due to their reduced control complexity and satisfying grasping capability. The gripping range of a gripper plays a key role in its universality. This article presents a pneumatically actuated soft-rigid hybrid multifinger gripper that has a wide gripping range by adjusting its initial grasp postures. The gripper is compact (dimensions:$\text{100} \times \text{60} \times \text{170}$mm), lightweight (weight: 380 g), and modular. It consists of four modules, with each module containing three pneumatic actuators (a distance-adjusting actuator, an angle-adjusting actuator, and a finger actuator) and rigid connectors. Through initial grasp posture adjustment, and fingers with tapered angles to generate nonconstant bending while grasping, the gripper can grasp objects of a wide variety of sizes and weights, thus increasing its universality. The gripper is tested to characterize its distance adjustment range, angle adjustment range, and stiffnesses in load-bearing directions, at continuously changing pneumatic pressures. The distance adjustment range and angle adjustment range of the gripper are 0–64.4 mm (64.4% of the initial gripper length) and 0$^{\circ}$–140$^{\circ}$, respectively. The maximum stiffnesses of distance-adjusting actuator and angle-adjusting actuator are 3331 and 1.15 N$\cdot$m/rad, respectively. Finally, grasping experiments show that our gripper can successfully grasp objects with diameters ranging from 0.5 to 180 mm, lengths ranging from 10 to 325 mm, and the heaviest object it can grasp is 2.1 kg (more than five folds of its own weight). The results demonstrated that our pneumatic gripper has an increased gripping range without adding other types of energy sources and its enhanced universality will expedite various applications in daily life and industry.