Manual Control Mode for Autonomous Mobile Robots Using Velocity-Based Impedance Control

In this industry-oriented research and development project, we studied the introduction and implementation of autonomous mobile robots (AMRs) for transporting equipment and parts in manufacturing facilities of aircraft equipment. In the relationship between the operator and AMR, it is crucial to implement an autonomous driving mode as well as enable the operator to control the operation by directly interacting with the AMR, such as when moving in complex locations. In such cases, a manual control mode is useful and often required. This study proposes a method of AMR motion that enables the operator to physically interact with the robot without the use of a force sensor and perform a power assist function according to longitudinal velocity-based impedance control. The power assist scheme can also be applied to other AMRs, particularly those with commercial motor-in-wheel drive systems, in which the design parameters, current, and torque of the motors cannot be measured or monitored in real time. For the control scheme, we designed a dynamic observer based on a mathematical model of the robot to estimate the force exerted when the operator contacts the body of the robot. Additionally, we developed a complementary algorithm that enables the movement of the robot on inclined surfaces. Comprehensive experimental analysis of the AMR under different operating cases demonstrates the feasibility and efficacy of the proposed power-assist control scheme.