Twister

Patent Pending

Pulley Tensioning system

This was one of the projects I did for Institute of Human and Machine Cognition (IHMC) Robotics during my ​Summer 2022 internship. It was super fun and challenging to work on this project and it turned out great! We ​decided to file a patent for it as well after I wrapped up the project. That being said, I will share just the ​surface level of the project to not interfere with the patent filing process.

Traditional tensioning system for pulley system adds friction (idler ​pulley) or inertia (turn buckles) to it, making it less efficient. The idea ​for Twister is that you can “twist” part of the pulley hub to tighten the ​cables. Now that might not make a whole lot of sense but imagine ​that you have two pulleys stack inside one another. One of them is ​used to drive the cable system, and the other one is used for reeling ​in the cable so that tension can be adjusted.

I used Finite Element Analysis (FEA) to design and optimize the ​weight of the final metal parts that we manufactured. I managed to ​save around 20% of the weight while keeping the safety factor at 2.5!

I really wish I could share more pictures and how twister works, but I don’t want to risk not getting my ​second patent, sorry.

For its application, I developed this for IHMC exoskeleton team to be used with their future versions of Eva, ​an in-house developed lower-limb exoskeleton. Twister will allow the team to transition from pin joint actuator ​to remote drive, making the weight distribution a whole lot better. Not only that, but Twister is also designed to ​be used with bi-directional cable driven pulley system, which makes it even more special as a tensioner!

Twister performs well enough with 80% torque at output compared to input torque on the benchtop design ​validation setup I set up.