This document describes improvements made to a vibrotactile device used in rehabilitation training for persons with lower-limb amputations. The original device generated vibrations to simulate tactile feedback during ambulation but pilot studies showed it could be improved. Design modifications included adding a clamp to more easily attach the device to prosthetics, using multiple motor types to increase feedback strength, replacing sensors to more accurately measure gait, and modifying the actuation unit to provide stronger tactile feedback. These improvements aim to enhance the device's functionality for evaluating motor control in rehabilitation experiments.

1. Panadda Marayong, Member, IEEE1, and I-Hung Khoo, Member, IEEE2 Rae Jillian Rivera1, Jairo Maldonado1, Cody Dunn2, and Stephen Cortez2
1Department of Mechanical & Aerospace Engineering, 2 Department of Electrical Engineering
Design Improvements of a Vibrotactile Device for Prosthetic
Rehabilitation Training
ABSTRACT:
This work describes the design improvements of an
existing vibrotactile device developed for rehabilitation
training and motor control study of persons with
transtibial amputation. The device generates vibration
that simulates the tactile feedback felt on the residual
limb during a real-life perturbation and can be
synchronized with a motion analysis system. Based
on a pilot study, a number of design modifications
were made to improve its accuracy and efficiency.
INTRODUCTION:
During ambulation, individuals with lower-limb
prosthesis utilize tactile feedback felt at the skin-
socket interface to perceive the state of the
prosthesis. The loss of proprioception can affect their
stability and can contribute to an increase in falls in
this population [1]. Our group developed a portable
vibrotactile device that can generate tactile stimulation
at the skin-socket interface for use in rehabilitation
training and motor control research [2]. The
functionality and effectiveness of the first design was
evaluated in a pilot study with two subjects with
unilateral transtibial amputation [3]. The data show an
increase in their ability to perform corrective
movements with the device. From the data, design
modifications are made to improve the system
performance.
SYSTEM OVERVIEW:
REFERENCES:
[1]W.C. Miller et al. “The prevalence and risk factors of falling and fear of falling
among lower extremity amputees,” Archives of Physical Medicine and Rehab.
82:1031–1037, 2001.
[2]P. Marayong et al, “Vibrotactile device for rehabilitative training of persons with
lower-limb amputation”. IEEE HIC, p.157-160, 2014.
[3]R. Rivera, P. Marayong, B. Ruhe and I. Khoo, “Performance analysis of a
vibrotactile device for rehabilitation training of persons with transtibial
amputation”, CSUPERB Biotech Symposium, Jan, 2016.
CONCLUSION & FUTURE WORK:DESIGN IMPROVEMENTS:
Motor Housing
• To add versatility and ease of attachment, a clamping mechanism was
added to the housing allowing it to clamp onto a standard 30mm pylon.
• To increase the strength of the tactile feedback felt by the subject, a four
motor unit was designed using a combination of two motor types. The
motor combinations were determined from data collected from pilot tests.
ACKOWLEDGEMENTS:
This research was supported by the National Institute of General Medical Sciences of the
National Institutes of Health under Award Numbers; 8UL1GM118979-02; 8TL4GM118980-
02; 8RL5GM118978-02. The content is solely the responsibility of the authors and does not
necessarily represent the official views of the National Institutes of Health
• Control Unit- Houses a microcontroller, an IR receiver, and batteries.
• Sensor- measures the relative knee angle and determines the swing
state of the prosthesis.
• Vibrotactile Unit:
• Vibrating Motors- creates a dragging sensation of the foot during swing
phase.
• Solenoid- create a knocking sensation of the foot during swing phase.
Vibrotactile
Unit
Goniometer
Sensor
Control
Unit
Solenoid
Motor Housing
Motors
Fig 4. Top view of the motor
housing that mounts inline with
pylon & Goniometer Sensor.
Figure 1. A VICON motion analysiusing s system computer
generated image of a subject the Vibrotactile Device.
Fig 3. Side view of the Motor
Housing and Solenoid
Mounted.
Fig 2. Overview of the system
component of the existing vibrotactile
unit inline with the pylon.
Goniometer
Actuation Unit
• The tactile feedback felt by the patient was
increased by a custom-built spring launcher
the solenoid was replaced with.
• The force generated by a compressed
spring is used to strike the pylon. The
launcher is triggered by a rotating motor.
Fig 5. Design iterations of the motor housing unit organized from left to right.
Fig 6. Most recent design of the
spring launcher.
Inertial Measurement Unit (IMU):
• Two digital IMU’s replaced a
goniometer sensor to increase
accuracy of the relative knee
angle measurement.
• One IMU is placed on the thigh
and the other on the mid-calf to
improve the detection of the
user’s swing state.
Control Unit
• To increase efficiency, data
collected was saved onto an SD
card.
• A TFT 1.8’’ LCD display with a
joystick is added as the user
interface.
• For compactness, voltage
converter circuits are
implemented to replace 1.5V
batteries with fewer 9V batteries.
These improvements are expected to
strengthen tactile feedback and
increase the versatility of the
vibrotactile system. An experiment
with commercial motion analysis
systems will be performed to test the
functionality of these improvements.
Fig 7. IMU mounted
on a custom made
holder.
Fig 8. Top view of the
control unit showing 9V
battery holders at the top
and the LCD display at
the center of the image.
Fig 9. Side view of the
improved Motor Housing
and Actuation Unit.