Design, modeling and optimization of a high torque asymmetric dual chamber soft actuator

This article presents a study on a new high torque asymmetric dual chamber soft actuator (ADCSA), aimed to discover the bending performance of ADCSA as an actuator on the human knee for assistance. First, a novel ADCSA design concept for lower limb is proposed, which can be used as an actuating module in an assistance exoskeleton. An ADCSA is composed of two single soft actuators (SSAs) in different sizes. Secondly, multiscale models are established to describe mechanical characteristics of SSAs and ADCSAs. The models are used to optimize the optimal solution for ADCSA. Thirdly, the length of the small SSA in the ADCSA is optimized to get a better actuating effect (i.e., bending torque, hindering torque, bending angle and stiffness) and wear comfort. In the end, we selected a length of 78mm for the small SSA in ADCSA. The bending torque can reach 33.89Nm (400kPa), the hindering torque can reach 11.75Nm (400kPa), the bending angle can reach 1.57rad and the stiffness can reach 21.72Nm/rad. The proposed ADCSA has potential applications in bionic and assistance robots. [Display omitted] •A novel high torque asymmetric dual chamber soft actuator design concept for lower limb is proposed.•Multiscale models are established to describe mechanical characteristics of SSAs and ADCSAs. The models are used to optimize the optimal solution for ADCSA.•The bending torque can reach 33.89 Nm (400 kPa), the hindering torque can reach 11.75 Nm (400 kPa), the bending angle can reach 1.57 rad and the stiffness can reach 21.72 Nm/rad.