A Simple and Scalable Force Actuator

摘要

One problem posed by robots that must perform in unstructured environments and interact with humans is that of achieving high fidelity force control as well as compliance in a compact form factor. Force control, as opposed to only position control, allows for safe, graceful contact behavior. Having spring elements placed in series between an actuator and its output provides this desired compliance. It also provides low mechanical impedance, precise force sensing capability, and good control bandwidth, as demonstrated by Series Elastic Actuators (SEA). There have been both linear and rotary versions of SEAs, each with their own advantages and shortcomings. However, neither type of these actuators is easily miniaturized for joint mounting; linear SEAs require ball screws while conventional rotary ones require custom-made torsional springs. The aim of this work was to integrate the positive features of an SEA into a compact, easy-to-build rotary actuator. This new actuator design involves two opposing linear springs coupled to a rotary shaft. A modified potentiometer relays position information linearly proportional to spring deflection and thus applied force. The mechanism is intentionally fabricated in layers to achieve precompression/extension of the springs while maintaining construction simplicity. The result is a completely encased and scalable module made of inexpensive off-the-shelf components.