Development of objective discomfort evaluation indicators for a task-oriented motion using less constrained motion concept: application to automotive pedal clutching task

This paper presents a method to develop objective discomfort evaluation indicators for a task oriented motion using the concept of less constrained movement. The basic idea is to compare imposed and less constrained movements in order to identify relevant biomechanical parameters for defining objective discomfort indicators. The task of automotive pedal clutching was chosen for illustrating the proposed method. Based on discomfort questionnaire and motion analysis of the experimental data, four discomfort indicators were proposed. Two of them were based on the ankle joint angle around flexion/extension axis at the beginning and the end of the clutch pedal depression. The third one was defined using knee flexion/extension joint torque at the end of the clutch pedal depression. The last indicator was defined as the relative lateral position of the heel compared to the average pedal lateral position for less constrained configurations. A global discomfort function was also defined as a weighted sum of all indicators. Globally, the proposed global discomfort indicator succeeded in differentiating the tested configurations in agreement with experimental observation. As expected, less discomfort rating is obtained for less constrained movement when compared with the corresponding imposed one.