Improving Human-Robot Cooperation by Measuring Muscle Co-activation with EMG (Grafakos, 2016)

Abstract

The majority of work performed daily in the production industry and in the field of medical robotics incorporate processes that require high accuracy and minimize processing time. In the last decades, robotic arms in these areas have achieved a significant improvement of results and due to the flexibility, high working accuracy in repeatability and resistance that they present. In order to improve the human - robot cooperation in cases that the environment modeling is impossible, new control strategies are developed. The impedance and the admittance control are new types of control schemes, which are able to achieve the process goals even in unstructured environments. The operator has the ability to chance the robotic arm position immediately by changing the position of the robot’s end-effector, without using any type of teleoperation system. By applying these methods it is possible, for the human factor, to take part in the operation process and increase the human - robot immediacy.

The main purpose of this student thesis is the improvement of the impedance control methods considering the human intention for the cooperation. The basic idea comes from several applications which monitor the human arm muscle system with the aim of improving the stability of the impedance model. More specific we have created two improved control strategies which are able to change the desired dynamic model of the robotic arm in real time, by changing the damping coefficient, depending on the muscle co-activation of the operator’s arm. The first method increases the damping coefficient of the robotic arm when muscle co-activation is occurred. The second method is completely opposite because the damping coefficient is decreased in case of muscle co-activation rising.

Several people will evaluate the performance of the new methods in an experiment that simulates high accuracy movement. More specific they were asked to move the robotic arm end point following a wire with predetermined geometry. The results of the new method will be compared with the impedance control strategy of stable gains by evaluating the trajectory accuracy, the process time, the operator energy consumption and the user opinion. Last but not least we will try to define if the operator is able to combine the change of muscular activation with the dynamics of the robotic arms. We are investigating if the cooperation with the proposed control strategies will increase the operator’s performance.

The results are encouraging since there is a reduction of energy consumption while there is a tendency to improve the accuracy of motion of the working tip with both methods. The greatest improvement is noted with the method which increases the damping of the robotic arm when muscle co-activation is occurred. Contestants couldn't be trained by new admittance control strategies. Despite the fact that were able to recognize how the methods work but they couldn't exploit their advantages and improve their performance.

 

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