BiPneu: Design and Control of a Bipolar-Pressure Pneumatic System for Soft Robots

2026-05-12

AI Summary

This study addresses the challenges in bidirectional pressure control for soft robotics, which are hindered by asymmetric inflation–deflation dynamics, valve nonlinearities, and disturbances during mode transitions. To overcome these limitations, the authors present BiPneu—a scalable, low-cost, multi-channel pneumatic system—and develop a dual-mode sliding mode controller (DM-SMC) based on a hybrid electro-pneumatic model. A novel hysteresis-based supervisory mechanism is introduced to suppress transition-induced disturbances. The proposed approach achieves high-precision, fast-response pressure regulation across a wide operating range while maintaining compatibility with high-level software ecosystems. Experimental results demonstrate significant performance improvements: in multi-step and sinusoidal tracking tasks, the average absolute errors are reduced to 1.44 kPa and 4.23 kPa, representing reductions of 11.9% and 35.6% compared to conventional PID control, respectively. The method’s efficacy is further validated on both a soft parallel manipulator and a bellows actuator.

Abstract

Positive-negative pressure regulation is critical to soft robotic actuators, enabling large motion ranges and versatile actuation modes. However, achieving high-performance regulation across both pressure polarities remains challenging due to asymmetric inflation-deflation dynamics, valve nonlinearities, and switching-induced flow disturbances. This paper presents BiPneu, a scalable and cost-efficient multi-channel bipolar-pressure pneumatic system for soft robots that enables wide-range, accurate, and responsive pressure regulation while providing seamless compatibility with high-level software ecosystems. A dual-mode sliding-mode controller (DM-SMC) with hysteresis-supervised mode selection is proposed based on a hybrid electro-pneumatic model. Extensive simulation and experiments demonstrate the superior performance of DM-SMC in tracking step and sinusoidal pressure references compared with both advanced model predictive controllers and well-tuned PID controllers. Experimental results show average absolute errors of 1.44 kPa in multi-step tests and 4.23 kPa in sinusoidal tracking, corresponding to reductions of 11.9% and 35.6% relative to PID control, along with improved control effort, valve switching rate, and transient response. Robustness of DM-SMC is further verified on a bellow actuator with pressure-dependent volume. Finally, BiPneu's capability is demonstrated via two soft robotic examples, quick ball-maneuvering with a soft parallel manipulator and real-time finite element method (FEM)-based teleoperation of a soft bellows actuator.

Problem

• bipolar-pressure
• soft robots
• pressure regulation
• asymmetric dynamics
• valve nonlinearities

Innovation

• bipolar-pressure pneumatic system
• dual-mode sliding-mode control
• soft robotics
• hysteresis-supervised mode selection
• pressure regulation