Gait Assistive Shoulder Prosthesis:
Shoulder Control Moment Gyroscope (SCMG)


The human arm contributes significantly to our stability and efficiency when we walk. For shoulder disarticulation and forequarter amputees who have lost an entire arm, these dynamics are no longer a part of their biomechanics. A novel prosthesis is proposed herein that focuses on restoring some of the complex dynamics of the arm for whole-arm amputees. While most prostheses for arm amputees focus on restoring the user's capabilities for dextrous manipulation, this prosthesis remains affixed to the shoulder and exerts a moment on the user's trunk similar to that of the arm during walking for dynamic motion assistance. The size, ease of use, and relatively low cost to maufacture of the proposed device makes it an attractive complement or alternative to standard prostheses, especially for amputees who pursue rigorous or prolonged physical activity.

The device may be applied in several ways to improve the lives of amputees, including:
  • everyday use, particularly for users who are active or are endurance athletes
  • acute and long-term rehabilitation following amputation
  • integration into existing biomimetic prostheses
Device concept rendering.


A prototype actuator and sensing module are currently under test as of January 2017. The prototyping process identified unforeseen considerations, risks, and features that will be incorporated into the design of a next generation device that can be tested on human subjects. The current actuator and sensor prototypes will undergo testing in Spring 2017 to verify key functional requirements of the proposed design, including:
  • actuator torque multiplication capabilities
  • actuator bandwidth
  • gait sensing capabilities for shoulder mounted sensing architecture and data processing algorithms
  • device mass and power consumption
Click to see video of the gyroscope prototype.
[May 2017 Update]
The prototype actuator has successfully produced moments in excess of those exerted by the arm during walking, at a similar speed. The disk weighs approximately 2lbs, considerably less than the average weight of the human arm, meaning that a final device has room to be customized for each user to match the weight of the missing arm. Upcoming development will focus on fabrication of a second generation device that can be worn on the body, and development of a gait identifying control scheme based on IMU signals from the shoulder. VA, DoD, and private funding is being solicited for this development and an ensuing clinical trial.

Awards, Presentations, and Media:

Presenter, Dynamic Walking Conference, Mariehamn, Finland, June 2017 — Robotics and prosthetics are a central topic in this year's Dynamic Walking Conference. SCMG will be presented over the course of the four day conference. View abstract:

Muller, M. and Popovic, M, Shoulder Mounted Gyroscopic Prosthesis for Assisting Arm Amputees During Walking, Dynamic Walking Conference 2017. Mariehamn, Finland, June 4-9 2017.

1st overall, Investing in Ideas with Impact (i3), WPI, April 2017 — i3 promotes the spirit of entrepreneurship by allowing student researchers to give a 3-minute pitch advertising their research's commercial viability to a panel of distinguished entrepreneurs and business leaders. Selected first overall from a pool of 20 finalists.

Honorary Mention, Graduate Research Innovation Exchange (GRIE), WPI, April 2017 — Sponsored by the Office of the Provost and the Dean of Graduate Studies, the GRIE poster competition highlights the breadth, diversity, and quality of WPI's graduate research. Chosen as a finalist from over 170 entries, and awarded Honorary Mention from 68 finalists.

Presenter, Northeast Bioengineering Conference, NJIT, April 2017 — Accepted under Device Technologies & Biomedical Robotics track, presented at Sunday morning digital poster session. View slides here.

Muller, M. and Popovic, M, Shoulder Mounted Gyroscopic Prosthesis for Assisting Arm Amputees During Walking, Northeast Bioengineering Conference 2017, Newark, New Jersey, US, April 1-2, 2017.

Also demonstrated at the Cambridge Science Festival 2017, Science Carnival and Robot Zoo, Cambridge, Massachusetts, US, April 15, 2017.

Current Researchers:

Mitchell K Muller and Marko B. Popovic

Past Researchers:

This project represents a continued interest in actuated shoulder cap. Previous effort has been focused on linearly and not rotationally moving mass. For more details see Actuated shoulder cap and arm movements in walking.

It all started back in spring 2012 when MIT Professor Seth Teller asked Professor Popovic to create a better shoulder prosthesis for forequater amputation, namely a re-designed shoulder cap that can provide an appropriate mass in place to counterbalance the existing limb, to address evolving skeletal abnormalities such as gait disturbance, spinal rotation, and neck, back and hip strain due to the lack of efficient biomechanical counterbalance.