A new vacuum-powered soft bending actuator with programmable variable curvatures

Vacuum-powered actuators possess inherent security, reliability, and durability compared with positivepressure-powered actuators. However, achieving the variable curvatures of such actuators with a single input is challenging and has rarely been reported so far. Herein, we develop a new vacuum-powered soft bending actuator (VPSBA) that can bend clockwise and anti-clockwise by tuning the interior angle of the chambers. The experimental results show that the actuator can yield a maximum bending angle of 127.7 degrees and 171.5 degrees for the interior angle of 76 degrees and 104 degrees, respectively. The finite element results show a great agreement with the experiment results. The maximum relative error between the FEM results and experiment results is about 8.8%. And we find that the maximum bending angle is affected by the geometrical parameters but actuating pressures. The actuating pressure and thickness of the front and back walls significantly affect the bending curvature. Consequently, a biarc approximation method, surrogate model, and multi-objective particle swarm algorithm are employed to realize the programmable variable curvatures of the VPSBA by tuning the actuating pressure and thickness of the front and back walls. We design successfully three VPSBAs whose deformation can accurately match arc and cosine curves with a single input.