Adapting to Flexibility: Model Reference Adaptive Control of Soft Bending Actuators

Soft pneumatic actuators enable robots to interact safely with complex environments, but often suffer from imprecise control and unpredictable dynamics. This letter addresses these challenges through the use of model reference adaptive control, which modulates the input to the plant to ensure that it behaves similarly to a reference dynamic model. We use adaptive control to standardize the performance of soft actuators and eliminate their nonlinear behavior. We implement an adaptive controller chosen for its simplicity and efficiency, and study the ability of this controller to force different soft pneumatic actuators to behave uniformly under a variety of conditions. Next, we formulate an inverse dynamic feedforward controller, allowing soft actuators to quickly follow reference trajectories. We test the performance of the proposed feedforward controller with and without the adaptive controller, to study its open-loop effectiveness and highlight the improvements the adaptive controller offers. Our experimental results indicate that soft actuators can follow unstructured continuous signals through the use of the proposed adaptive control approach.