Chang Liu designed and constructed an “S-Curve” mechanism. The mechanism is mounted (upside down) on a table, and tasked to repeatedly kick a weight mounted on a linear slide above it. Due to its incorporation of kinematic singularities, the series-elastic actuator (SEA) which powers the mechanism is capable of storing the motor’s energetic output when out-of-contact with the weight, then immediately releasing it upon contact through a mechanical reflex. This is done in the absence of motor control. The result is a repeated dynamic kicking motion. To compare the S-Curve mechanism to a point of reference, the same uncontrolled SEA is hooked up to a basic slider-crank.

C. Liu and M. Plecnik, 2022. “Experimental Validation of the Usage of Kinematic Singularities to Produce Periodic High-Powered Motion,” Accepted to the IEEE 2022 International Conference on Robotics and Automation (ICRA). (link)