Robust Dynamic Stability
At Agility Robotics we design and develop bipedal robots intended to work in the real world. The real world is full of unpredictable environments and situations that arise within them. It is essential for our robots to be able to handle those environments smoothly. In order to accomplish this we have to achieve what is considered compliant behavior within the environment. Essentially this is the biomechanical principle animals leverage to walk around and react to unexpected disturbances smoothly.
Digit is designed to work in human environments, with humans
Rather than attempt to copy what an animal does, we work to understand how they achieve it and leverage this knowledge to reach an optimized answer to a design problem. Our work is inspired by nature rather than attempting to mimic it. We do this by focusing on the performance goal rather than the structure. What we achieved through this approach is easy to observe when compared to an example from nature.
When observed side by side we see the foot first slows down, anticipating the impact of the ground. The foot starts to apply forces on the perceived ground but ultimately bursts through the tissue paper and accelerates straight towards the actual ground. The distance to the actual ground causes the foot to swing back a bit further (relative to the body) than planned. This translates to forward acceleration. This increased acceleration with the addition of the requirement to step out of the depression creates an additional unanticipated disturbance. Both bird and robot now must assume a slightly more crouched posture to maintain control. After a few strides both subjects have returned to their respective nominal speed and original height.
What's most impressive in both cases is that this transpired in a fraction of a second. If it didn't, control would be lost. The bird achieves this through realizing the benefits of millions of years of evolution. In the case of Digit, software had to be developed in order to very quickly react and make a decision about how to deal with the disturbance. Furthermore it was essential for the software to be developed in close concert with the compliant elements of the hardware, otherwise it simply wouldn't work. Ultimately this is what enables Digit to thrive in a wide variety of environments and sets us apart from many other bipedal robots.
