R3
c. 2013 ~ 2014
The R3 arm was designed as a low-cost, easy to repair, robot arm that emphasized fantastic force control. The original application was to be a replacement for people in factories that still did the hard things like plugging things into connectors in phones. Tasks that required great force control and good position control performance. It was meant to be easy to drop into an existing factory line and easy to set up the motion for the task. It was to be easy to repair and fast to install so that it didn’t need a 10 year life (like typical industrial robots) so less durable components and materials could be used to drop the price way down. While it was very very good at force control we did not achieve the other goals.
The R3 arm was developed as a product for Redwood Robotics which was a joint venture between Meka Robotics, Willow Garage and SRI International. Redwood Robotics was set up as a way to productize the research into actuator design Meka and SRI had been working on through DARPA projects and other grants. Redwood and Meka were acquired by Google at the end of 2013 as part of their acquihire spree to start their robotics program.
The R3 arm never made it out of the lab but Google did make a pile of them to run endless test for training machine learning models for a few years.
A very early prototype of the complete “bicep” segment. The motors didn’t have integrated encoders yet and the pullies were 3d-printed but it demonstrated the full architecture. This video specifically shows the two degrees of freedom controlled to zero torque.
Tracking a large amplitude square wave.
The module tracking sine waves in both degrees-of-freedom. This shows how the cable differential worked to translate the belt-drive outputs to the final roll and pitch motion.