As the role of robotics continues to expand beyond highly structured manufacturing applications to other domains, including medical and service applications, safe operation in the presence of people is becoming increasingly important. Many existing safety systems rely on fragile and sophisticated joint torque sensors and control models that greatly add to the expense and complexity of the robot system. This paper presents the "Fusion Clutch", a mechanical system for decoupling high-impedance actuators from the output, such as a robot arm, in the event of a collision. In its nominal configuration, the clutch couples the transmission to the output via a spring-loaded bi-stable mechanism that is able to quickly decouple the two in the event of a collision with very low activation force. After the actuator is disengaged, the clutch also applies a brake to the output that prevents it from falling under the force of gravity but allows the operator to still reposition it. This prevents a robot arm from pinning the operator after the mechanism had been activated. Experimental results validate the small force required to activate the mechanism, along with a substantial decrease in force impulse during impact.
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