An Improved Koopman-MPC Framework for Data-Driven Modeling and Control of Soft Actuators

The challenge of achieving precise control of soft actuators with strong nonlinearity is mainly due to the difficulty of deriving models suitable for model-based control techniques. Fortunately, Koopman operator provides a data-driven method for constructing control-oriented models of nonlinear systems to achieve model predictive control (MPC). It is called the Koopman-MPC framework, which is theoretically effective for soft actuators. Nevertheless, in this framework, a critical challenge is to select correct basis functions for Koopman-based modeling. Furthermore, there is room for improvement in control performance. To overcome these problems, this letter presents an improved Koopman-MPC framework to efficiently implement model-based control techniques for soft actuators. Firstly, we propose a systematic method for selecting the basis functions, which extends the measurement coordinates with derivative and time-delay coordinates and uses the spares identification of nonlinear dynamics (SINDy) algorithm. Secondly, an incremental model predictive control with dynamic constraints (IMPCDC) is developed based on the Koopman model. Finally, several comparative experiments are conducted to verify the utility of the improved Koopman-MPC framework for data-driven modeling and control of soft actuators.