But most humanoid robots use motor and gears to power their joints, and these mechanisms are not backdrivable—due to energy losses in the gears and you can’t relate the electrical current in the motors to force. That’s why they need force sensors if you want to move in a compliant way; it’s called active compliance. Romeo is different. It has no gears. We transmit the motion from the motors to the joints using screws and cables. This system is backdrivable.