Virtual Grasping: Closed-Loop Force Control Using Electrotactile Feedback

Figure 1

Experimental setup for closed-loop force control using electrotactile stimulation. The task for the subject was to generate an appropriate force to lift the target object without breaking it. The command interface was joystick and a push button. The electrotactile feedback was provided using a stimulation unit and concentric electrodes placed on the forearm of the subject. The control loop operated in real time at the sampling frequency of 100 Hz. The graphical interface for the subject included a model of the prosthesis, target object, and a force bar showing the minimal, current, maximal and breaking force. The bar plot was used at the beginning of the training to teach the subjects the task they should perform as well as the meaning of the electrotactile feedback. Otherwise, the visual force feedback was not shown on the screen. For detailed explanation see Section 2.4.