Pneumatic soft robots are of great interest in varieties of potential applications due to their unique capabilities compared with rigid structures. As a part of the soft robotic system, the pneumatic system plays a very important role as all motion performance is ultimately related to the pressure control in air chambers. With the increasing flexibility and complexity of robotic tasks, diverse pneumatic robots driven by positive, negative, or even hybrid pressure are developed, and this comes with higher requirements of pneumatic system and air pressure control precision. In this study, we aim to propose a simplified pneumatic design capable of generating programmable pressure states ranging from negative to positive pressure in each air branch. Based on the design concept and system configuration, special inflation and deflation strategies and closed-loop feedback control strategy are proposed to achieve precise pressure control. Then, a prototype of the pneumatic system with six independent air supply branches is designed and fabricated. Experimental results show that the pneumatic system can achieve a wide range of pressure from -59 to 112 kPa. The speed of inflation and deflation is controllable. Finally, we demonstrate three robotic applications and design the related algorithms to verify the feasibility and practicability of the pneumatic system. Our proposed pneumatic design can satisfy the pressure control requirements of a variety of soft robots driven by both positive and negative pressure. It can be used as a universal pneumatic platform, which is inspiring for actuation and control in the soft robotic field.
Keywords: closed-loop pressure control; pneumatic system; programmable pressure supply; soft robot.