Abstract
Model-based optimal control of soft robots may enable compliant, underdamped platforms to operate in a repeatable fashion and effectively accomplish tasks that are otherwise impossible for soft robots. Unfortunately, developing accurate analytical dynamic models for soft robots is time-consuming, difficult, and error-prone. Deep learning presents an alternative modeling approach that only requires a time history of system inputs and system states, which can be easily measured or estimated. However, fully relying on empirical or learned models involves collecting large amounts of representative data from a soft robot in order to model the complex state space–a task which may not be feasible in many situations. Furthermore, the exclusive use of empirical models for model-based control can be dangerous if the model does not generalize well. To address these challenges, we propose a hybrid modeling approach that combines machine learning methods with an existing first-principles model in order to improve overall performance for a sampling-based non-linear model predictive controller. We validate this approach on a soft robot platform and demonstrate that performance improves by 52% on average when employing the combined model.
Highlights
Soft robots have many desirable characteristics which make them attractive candidates for a wide variety of tasks where traditional rigid robots are ill-suited
We see that Non-linear Evolutionary Model Predictive Control is capable of generating excellent control inputs for a system that is well-approximated by a surrogate deep neural network (DNN)
When non-linear evolutionary model predictive control (NEMPC) is used to control the hardware with a surrogate DNN, the results are much worse because the surrogate DNN is a poor approximation of the dynamics for the real hardware
Summary
Soft robots have many desirable characteristics which make them attractive candidates for a wide variety of tasks where traditional rigid robots are ill-suited. The main contribution we present is a methodology for learning model discrepancies for use in a real-time non-linear model predictive control (NMPC) scheme. We validate this approach in simulation and on a soft robot platform.
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