Integrated Temperature and Position Sensors in a Shape-Memory Driven Soft Actuator for Closed-Loop Control

Soft actuators are a promising option for the advancing fields of human-machine interaction and dexterous robots in complex environments. Shape memory alloy wire actuators can be integrated into fiber rubber composites for highly deformable structures. For autonomous, closed-loop control of such systems, additional integrated sensors are necessary. In this work, a soft actuator is presented that incorporates fiber-based actuators and sensors to monitor both deformation and temperature. The soft actuator showed considerable deformation around two solid body joints, which was then compared to the sensor signals, and their correlation was analyzed. Both, the actuator as well as the sensor materials were processed by braiding and tailored fiber placement before molding with silicone rubber. Finally, the novel fiber-rubber composite material was used to implement closed-loop control of the actuator with a maximum error of 0.5°.

A Pneumatic Novel Combined Soft Robotic Gripper with High Load Capacity and Large Grasping Range

Pneumatic soft grippers have been widely studied. However, the structures and material properties of existing pneumatic soft grippers limit their load capacity and manipulation range. In this article, inspired by sea lampreys, we present a pneumatic novel combined soft gripper to achieve a high load capacity and a large grasping range. This soft gripper consists of a cylindrical soft actuator and a detachable sucker. Three internal air chambers of the cylindrical soft actuator are inflated, which enables them to hold objects. Under vacuum pressure, the cylindrical soft actuator and the detachable sucker can both adsorb objects. A finite element model was constructed to simulate three inflation chambers for predicting the grasping range of the cylindrical soft actuator. The validity of the finite element model was established by an experiment. The mechanism of holding force and adsorption force were analyzed. Several groups of experiments were conducted to determine adsorption range, holding force, and adsorption force. In addition, practical applications further indicated that the novel combined soft gripper has a high load capacity (10.85 kg) at a low pressure (16 kPa) and a large grasping range (minimum diameter of the object: d = 6 mm), being able to lift a variety of objects with different weights, material properties, and shapes.

Dimension investigation to pneumatic network bending soft actuators for soft robotic applications

Soft actuators have been investigated for robots that interact with people, such as industrial robots, entertainment robots, and medical robots. Although soft actuators have been utilised in several applications, design tools that can assist in the effective and systematic design of actuators are needed. This paper focused on the most common soft actuators for bending motion, the Pneumatic Networks bending actuators. Paper presented a survey on the effects of changing the dimensions on the soft actuator and its cross-section shape on the soft actuator flexibility and the forces generated at different applied pressures. This survey can be used to optimize the dimension ratio for the soft actuator and the cross-section shape. Furthermore, this paper analyzed the possible reasons for the dimension change effect. The performance of the bending soft actuator was evaluated using ABAQUS/CAE software simulation models to provide quantitative insights into the actuators' behaviours. Thus, this paper provided a lot of insights that can be used to guide and accelerate the soft actuator design process to create strong and flexible Pneumatic Networks bending actuators. Using the paper insights outputs, a soft gripper was designed that can grasp many complex objects without needing any modification in the gripper shape. To show the proposed actuators' capacity to do complicated movements and expand their applications, a completely soft hand was created that can mimic the mobility of the human hand as nearly as possible, and this ability was verified using hand sign language settings.

Load-dependent Variable Gearing Mechanism of Muscle-like Soft Actuator

Pennate muscle is characterized by muscle fibers that are oriented at a certain angle (pennation angle) relative to the muscle’s line of action and rotation during contraction. This fiber rotation amplifies the shortening velocity of muscle, to match loading conditions without any control system. This unique variable gearing mechanism, which characterized by Architecture Gear Ratio (AGR), is involves complex interaction among three key elements: muscle fibers, connective tissue, and the pennation angle. However, how three elements determine the AGR of muscle-like actuator is still unknown. This study introduces a Himisk actuator that arranges five contractile units at a certain pennation angle in a flexible matrix, the experiment and simulation results demonstrated that the proposed actuator could vary AGR automatically in response to variable loading conditions. Based on this actuator, we present a series of actuators by simulations with the varying pennation angle (P), elastic modulus of the flexible matrix (E), and number of contractile units (N) to analyze their effects on AGR, and their interaction by three-factor analysis of variance. The results demonstrated that P and N effect on the AGR significantly, while E effects on AGR slightly, which supported the idea that the P is the essential factor for the AGR, and N is also an important factor due to the capability of force generation. This provides a better understanding of mechanical behavior and an effective optimizing strategy to muscle-like soft actuator.