Impedance Parameter Update Method of Dual-arm Manipulators based on Human Muscle Activation

Abstract

In this paper, using EMG sensors and Vive-trackers, dual-arm manipulators mimic human arm movements and propose how to update impedance parameters.

To allow the dual-arm manipulators to work for a specific purpose, it is necessary to carry out a motion planning that meets the constraints. However, due to the high degree of freedom of the dual-arm manipulators, It is difficult to design the robot's motion under conditions that are prone to collision due to overlapping workspaces. However, if the robot can imitate the movements of the human arm, these problems can be easily disappear. Therefore, in this paper, four trackers are worn on each person's hands and elbows, and EMG sensors are attached to the person's upper arm to allow the robot to mimic information about the movement and force of the person's arms.

The dual-arm manipulator is a robot with redundancy that is more flexible and human-like than six degrees of freedom robot when performing certain tasks. The robot with redundancy creates self-motion, which is controlled by null-space of Jacobian. Using dual-arm manipulators , this self-motion can lead to a collision between two elbows, but in this paper, instead of null-space control, the robot's elbow moves along the human elbow position to prevent collisions and make it more similar motion to human.

Since both hands of the robot are modeled with a mass-spring-damper system, the impedance parameters obtained from the EMG sensor are affected by the modeled mass, inertial matrix. Also the robot may become unstable if the impedance parameter is used as it is. This is because the farther the robot's arm moves away from the body, the closer it becomes to the singularity, and the inertial matrix grows infinitely as the Jacobian rank falls. Therefore, if the impedance parameters are normalized by dividing the value obtained by the EMG sensor by the diagonal component of the inertial matrix, the robot will show a slightly more stable appearance even if it approaches the singularity.