Reaching Torque–Velocity Profiles of Human Muscles: The Adaptive Cycloidal Linear Drive

Building humanoid robots with properties similar to those of humans in terms of strength and agility is a great and unsolved challenge. In this article, we introduce an adaptive linear drive for fast and powerful motions in robotics with a light gear mechanism: Adaptive Cycloidal Linear Drive. The gear mechanism features two transmission ratios covering a nominal operation region ranging from fast low-torque motions to slow high-torque motions, with a speed–force profile similar to those of human muscles. This is contrary to the limited nominal operation region of electric motors with single-ratio gearboxes and is realized by the new idea of adaptively combining a cycloidal stage with a linear spindle drive. The operation principle of the gear mechanism and hardware design of a prototype are described. Furthermore, the properties of the prototype are measured and compared with state-of-the-art solutions in robot design as well as to the performance of human muscles.