Characterisation of brushed DC motors used in H-Man : a 2DOF planar robot for stroke rehabilitation

• Main Author: Lim, Ke Zhang
• Other Authors: Domenico Campolo
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150802
• Institution: Nanyang Technological University

Stroke is a common condition in today’s world and often leads to a wide range of disabilities. Survivors of stroke often experience motor dysfunctions, which negatively impacts their quality of life. Rehabilitation has often proved to be useful in helping patients regain such motor functions. In recent years, an increasing number of robotic devices have been developed to aid therapists in stroke rehabilitation. The H-Man, a 2DOF planar robot targeted for stroke rehabilitation of upper extremity motor dysfunctions, is an example of one such device. The H-Man has a handle as an end-effector which is connected to cables actuated by brushed DC motors, and its effectiveness in rehabilitation is determined by the haptic interactions between itself and users, implemented through virtual forcefields. To properly implement these virtual forcefields, the performance of the brushed DC motors used in the H-Man must be known. Thus, in this project, a setup was implemented to characterise the brushed DC motors by determining important parameters relating to the performance of the motor, and to also observe the effects that age of a motor may have on these parameters. This setup consisted of a DC motor connected directly to a robotic actuator from HEBI robotics, and different experiments were performed to determine the various parameters. At the end of the experiments, the setup was found to be reliable in determining the armature constant ka and terminal resistance R of the motor. Furthermore, it was observed that age of a motor had little effect on its armature constant, while resistance R increases as the motor undergoes wear and tear. However, as the HEBI was unable to detect small changes in torque, the setup was unreliable in determining the moment of inertia of the armature Jm and the damping coefficient due to friction in the armature Bm.