Learning-based Approximate Model Predictive Control for an Impact Wrench Tool

TL;DR

This paper introduces a learning-based model predictive control method for impact wrenches that combines data-driven modeling and neural networks to enable real-time, safe, and accurate torque control on resource-limited embedded systems.

Contribution

It presents a novel approach integrating Gaussian process regression and neural networks for real-time predictive control in impact wrenches, suitable for embedded platforms.

Findings

Achieves microsecond-level inference times on embedded hardware.

Maintains safety constraints and improves torque tracking accuracy.

Demonstrates effectiveness through simulations and hardware tests.

Abstract

Learning-based model predictive control has emerged as a powerful approach for handling complex dynamics in mechatronic systems, enabling data-driven performance improvements while respecting safety constraints. However, when computational resources are severely limited, as in battery-powered tools with embedded processors, existing approaches struggle to meet real-time requirements. In this paper, we address the problem of real-time torque control for impact wrenches, where high-frequency control updates are necessary to accurately track the fast transients occurring during periodic impact events, while maintaining high-performance safety-critical control that mitigates harmful vibrations and component wear. The key novelty of the approach is that we combine data-driven model augmentation through Gaussian process regression with neural network approximation of the resulting control policy. This insight allows us to deploy predictive control on resource-constrained embedded platforms while maintaining both constraint satisfaction and microsecond-level inference times. The proposed framework is evaluated through numerical simulations and hardware experiments on a custom impact wrench testbed. The results show that our approach successfully achieves real-time control suitable for high-frequency operation while maintaining constraint satisfaction and improving tracking accuracy compared to baseline PID control.