Optimization of design parameters and improvement of human comfort conditions in an upper-limb exosuit for assistance

Exoskeleton robots have a wide range of applications in industrial field as well as for patients with locomotor disability. Among them, the flexible exoskeleton, known as “exosuit”, has attracted great interest from researchers. They are usually made up of flexible components such as cables and pieces of fabric. Since there are no rigid frames and links in the exosuits, they are much lighter and have less misalignment problems than the rigid exoskeletons. However, excessive pressure exerted by cables on soft tissues and skeleton of the human will lead to discomfort or even injuries. In this paper, a cable transmission system is incorporated into the exosuit system for gravitational compensation. The human body is assumed to be upright in the cable-driving wearable robot modeling. Then, a multi-criteria optimization approach, based on swarm intelligence, has been developed and adopted for reducing the uncomfortable forces applied on the user. Furthermore, the energy consumption is also taken into account in the design phase. Numerical simulation results demonstrate that the proposed exosuit design results in a reduction of more than 50% and 34% in the forces exerted on human body with loads of 0.5 kg and 5 kg, respectively. The energy loss was also reduced by up to 63% and 21% in these two cases.