Better Than Biology Actuators

Robots deployed by the DoD, in industry, and in consumer devices increasingly require the ability to perform safely and effectively around humans. In many task scenarios, it is desirable for a robot and human to work cooperatively together. For example, a human-robot team could unload a cargo container of rations, assist a person from the ground to a stretcher, or jointly assemble devices on a manufacturing line. A critical technology required to enable these scenarios is a lightweight robot actuator with high performance force sensing and control. Such an actuator should meet or exceed the efficacy of human muscle. It should exhibit a low minimum stiffness and low stored energy to enable safety around humans. Finally, to enable commercial viability the primary technology must be low cost and straightforward to fabricate. Meka Robotics, in collaboration with the Stanford Robotics Laboratory and SRI International, is pleased to propose a novel method for robot actuation. The proposed technology is low-cost, efficient, lightweight, and capable of human-level force density, high-bandwidth force control, and safe operation around humans. The electric motor actuator has three key technologies: 1) A novel rotary-to-linear transmission that is durable, lowcost, and lightweight, 2) a small and a large motor acting in parallel to achieve high bandwidth force output, and 3) use of a novel high power density electric motor technology. This novel design overcomes traditional safety limitations of joint torque control and the performance limitations of compliant actuators. In our design, two actuators are connected in parallel. Torque generation is partitioned into low and high frequency components. The smaller actuator produces low torques at high frequencies to provide disturbance rejection and high-performance dynamic control. The larger actuator provides large forces at low frequencies to offset static loads such as gravity. We propose in Phase I to accomplish: 1) modeling and simulation of the actuator, 2) performance comparison to human muscle, 3) a preliminary mechatronic design including specification of performance characteristics.