A VARIABLE STIFFNESS CONTINUUM PARALLEL MANIPULATOR WITH 3D PRINTED PNEUMATIC ARTIFICIAL MUSCLES

This paper presents a variable stiffness continuum parallel manipulator (VSCPM) with 3D printed pneumatic artificial muscles, which is inspired by parallel mechanisms and soft robotics. The proposed VSCPM is designed by connecting a fixed base and a moving platform with three pneumatic bellows muscles in parallel and circular distribution. A set of optimized 3D printing parameters for fabricating air tight pneumatic muscles by flexible Thermoplastic Polyurethane (TPU) filament is introduced, aiming at achieving rapid and low-cost manufacturing in comparison with other approach such as injecting silicon rubber into prefabricated molds. A prototype of the VSCPM is fabricated using the optimized 3D printing settings. The stiffness of a 3D printed bellows muscle under both positive and negative pressures is tested. The position and stiffness of the VSCPM controlled by both positive and negative pressures are also evaluated. Experimental results show that the VSCPM is capable of achieving a range of steering angle from 0 degrees to 360 degrees and a range of inclination angle from 0 degrees to 45 degrees. The stiffness of the VSCPM can also be adjusted by changing the air pressure supplied to the pneumatic artificial muscles. The novel VSCPM is compact, lightweight and soft to ensure the safe interaction with humans, which has a broad range of application such as wrist rehabilitation.