Command Acknowledge through Tactile Feedback Improves the Usability of an EMG-based Interface for the Frontalis Muscle

Abstract

This work presents a study on the effectiveness of tactile feedback for the acknowledgement of a correct command detection in an EMG-based interface for the frontalis muscle. EMG interfaces are increasingly used in assistive robotics to control robots exploiting the repeatability and robustness of the electromyographic signal. However, in many application a feedback about the correct detection of an input is often missed and the user has to wait for the device motion in order to understand if his/her will has been correctly detected by the system. We demonstrate with a user study involving fifteen subjects, that a simple vibrotactile feedback can reduce the muscular effort and the time needed to execute a sequence of action commanded by an EMG device. As a case study, an EMG interface for the frontalis muscle has been used, however proposed results could be extended to EMG interfaces designed for other muscles, e.g., for prosthesis or exoskeleton control.

Human augmentation by wearable supernumerary robotic limbs: review and perspectives

“…In the event-driven mode, the occurrence of an event drives the evolution of a finite state machine selecting a motion primitive within a finite set, which in turn defines the reference trajectory for the robot. The event can be triggered by either a physical switch on the interface [55] or by the detection of a posture, gesture or contraction of the human body [39,54,70].…”

Integration of a Passive Exoskeleton and a Robotic Supernumerary Finger for Grasping Compensation in Chronic Stroke Patients: The SoftPro Wearable System

“…The device is designed to recognize the movement of the eyebrows through real-time sEMG measurement of the frontalis muscle ( Hussain et al, 2016 ; Salvietti et al, 2017 ). In Franco et al (2019) , the authors have shown that a vibrotactile feedback at the occipital area of the head can be used as an acknowledgement of the correct processing of the sEMG signal improving the usability of the interface. In this way, whenever the user moves the eyebrows to control the Sixth Finger, the e-Cap informs the user with a short vibration burst that the Sixth Finger is about to close or to open.…”

“…Being an sEMG-based interface, it requires a calibration before operational use. The trigger for the calibration was upgraded in comparison to previous versions ( Hussain et al, 2016 ; Franco et al, 2019 ). The physical switch was replaced by a copper pad that acts as a touch button.…”

“…The physical switch was replaced by a copper pad that acts as a touch button. The calibration procedure is as follows: the touch button toggles the e-Cap from an operational status to a calibration status; once in the calibration status, the user perceives a vibration, and must raise the eyebrows to record the maximum value of the envelope of the sEMG signal; a threshold is automatically set as described in Franco et al (2019) .…”

Flexure mechanisms for upper-limb support: towards compliant wearable assistive devices

“…The SoftPro Wearable System [19] is a wearable technology demonstrator assembled and tested by the University of Siena. It integrates the Assistive Elbow Orthosis (AEOs) from Chapter 2 with a supernumerary robotic nger called the Robotic Sixth Finger [59], a exible surface electromyography (sEMG) interface [74] embedded in a cap called e-Cap [18,26], and a haptic interface called CUFF [6]. The integrated device worn by a healthy subject is shown in 2) 2) e-Cap: f) capacitive touch sensor, g) sEMG electrodes (inside), h) power supply, i) vibrotactile motor, j) signal processing unit; 3) CUFF: k) motor housing, l) encoders and connectors, m) Velcro strap, n) fabric belt…”