Twisted String Actuators

About

Summary Stanford engineers have developed a low cost, energy-efficient, compact mechanism to enable two-way operation of a twisted string actuator (TSA). Conventional TSAs offer a simple, robust system with high gear ratio to convert the rotation of a motor into a linear motion. However, they only work in one direction – contracting to pull an object – and are unable to return an object to the starting position. This new mechanism employs a soft buckling device fitted around the strings so it pulls like a traditional TSA, but also quickly lengthens and pushes in certain configurations. The apparatus stores energy during contraction and returns it to re-extend the TSA with nearly-constant extension force using no external power. This capability greatly increases the functionality of TSAs, with expanded applications in robotics and prosthetic devices.   Applications Robotics - simple two-way linear actuation (push and pull) with high gear ratio, with end-user applications such as: robotic hands or grippers wearable exoskeletons prosthetic limbs industrial robotics surgical robotics   Advantages Two-way operation - adds lengthening/pushing capability to conventional unidirectional twisted string actuators Energy-efficient, simple, robust and compact: standard twisted string actuation is a simple, robust alternative to geartrain systems buckling mechanism returns to initial elongated state with no extra motor or complex clutch system required Full operation range - unlike traditional spring recoil mechanisms, the buckling design offers a nearly-constant returning forces which allows the actuator to fully contract and then return to its initial elongated position