From @TaoBuildsRobots earlier today: how do you deal with robot-to-robot variation across a fleet? Calibrate every Digit individually, or train policies robust enough not to care? JH: Both. Minor variations exist in motor constant or robot component mass, that remain consistent once a robot is built, but may vary across the fleet; we believe these can be calibrated. But other features vary with time or temperature or other factors, and for those we must create policies that can handle the random variation. It is important to note, though, that one cannot train a policy to be robust to everything. We, as engineers, have to decide what is likely to vary, and be choosy about what we require the policy to be robust to; mostly, that should be things that will be outside of our control, like ground height, or mass of a bin, or friction coefficients.The more robust a policy is, generally, the lower the performance. For example: If we truly have no idea what the ground friction will be, then the robot always has to walk as if it were walking on ice. If we do have some confidence in the range of uncertainty of the ground friction, we can increase our confidence appropriately for the robot performance.