Team Members & Role:

• Dominic Locurto – Team Lead
• Aidan Downey – Evaluation Lead
• Alex Klinkhamer – Design Lead
• Sam Naftal – Analysis Lead
• Simon Houghton – Fabrication Lead

Abstract:
The team was employed to create a variable stiffness device by the UMass Integrative Locomotion Lab (UMILL) and the Human Robot Systems Lab (HRSL) to be placed under one track of a dual-track treadmill. The issue being addressed is that this kind of device is not commercially available, and no designs are available via open-source documentation. This means that it must be designed and built from scratch. Both groups are interested in observing human walking under asymmetric walking conditions to compare results to different simulations they have run in the past. Furthermore, the labs would like to use the variable stiffness treadmill as a rehabilitation device for stroke patients. The demand for these devices is new, which is why this issue has not been solved with existing technology. This is a novel design created by the group, as nobody has thought of employing this method of varying stiffness for this use. In the past, only two variable stiffness devices have been implemented into a treadmill. However, they have many issues the sponsors of this project have deemed unacceptable. One issue is complexity, as the existing models have many moving parts and constraints, which causes them to be large and have many possibilities for failure. Both are also their own issues, as they pose safety risks to the user of the treadmill. The team addressed these issues by creating a device that is not only simple in design, but only has two degrees of freedom. The team’s design approached this problem by employing basic beam bending principles to vary stiffness by changing the effective length of a steel leaf spring. The fulcrum point of this cantilever beam will change by moving the “cart” along the track on the floor using a motor with rack and pinion.