# Design and development of a modular wrist rehabilitation robot with impedance control and gravity compensation

## TL;DR

A modular wrist rehabilitation robot was developed to improve stroke recovery by adapting to different needs and providing precise control.

## Contribution

The novel modular design with impedance control and gravity compensation enables adaptable and precise wrist rehabilitation.

## Key findings

- Impedance control alone achieved an RMS error of about 7 degrees in simulations.
- Adding gravity compensation reduced maximum error to 0.79 degrees.
- Experimental tests confirmed effective user-robot interaction for rehabilitation.

## Abstract

The number of stroke patients is steadily increasing, highlighting the critical need for rehabilitation to restore motor function. The shortage of rehabilitation specialists and the repetitive nature of traditional exercises underscore the advantages of robotic systems. However, many existing rehabilitation robots are not adaptable to various therapeutic requirements. Modular robots, with their reconfigurability and ease of assembly, provide a practical solution. This study presents the design and development of a modular wrist rehabilitation robot, consisting of three identical modules that provide the necessary degrees of freedom for wrist movement. The modular structure allows for easy assembly, adjustment for different hand sizes, and adaptability to various configurations. To improve control performance, an impedance control strategy was implemented along with a gravity compensation method. Simulation results show that impedance control alone resulted in an RMS error of approximately 7 degrees, while adding gravity compensation reduced the maximum error to 0.79 degrees. The proposed controller was implemented on the robot and validated through experimental tests with individuals. The results confirmed that impedance control effectively facilitates interaction between the robot and the user, demonstrating the system’s potential for improving rehabilitation outcomes.

The online version contains supplementary material available at 10.1038/s41598-025-31185-w.