Team Members

Julian Arias, Will Aston, Patrick Bain, Erin Endrulat, Ethan Lann, David Shi, Chris Thatcher, Paul Valvo


The SPAR System, or Spring Pulley Active Reduction System, is an active body weight
support structure designed for patient use during electrically stimulated elliptical therapy. SPAR
was designed to keep the patient safe while contributing to the maximum therapeutic benefit of
elliptical therapy. The SPAR frame is mobile and customizable for each customer’s needs. It is
designed to be centered over a seated patient. Four custom springs are attached to the patient
harness; two secure the upper chest and two secure the upper back to ensure a stable offset
weight support during therapy. The springs are designed to provide optimum stiffness for a
consistent weight offset while providing a comfortable user experience. The opposing spring
ends are fixed to steel cables that secure to an electric winch through a series of pullies and cable
connectors. The patient is then lifted and centered over the elliptical. In active closed-loop
control, the winch actuates the applied spring force by changing the length of the springs. The
applied spring force is measured using an in-line force sensor at the main pulley cable
connection. The load cell meets both strength and endurance requirements for this application.
SPAR is completely computer controlled. An intuitive customer interface is fixed to the SPAR
frame where any laptop device is connected to the controller using a USB port. The application
display panel allows the patient and therapist to adjust the desired weight offset and inform the
therapist of current system diagnostics.