Dexterity is a battery problem before it's an AI problem, and force sensitivity is a control problem before it's a safety feature. US10730186B2, granted in August 2020 to Kastanienbaum GmbH and naming Sami Haddadin — a central figure in sensitive robotics — is a foundational read on how a joint can be both commanded and felt.
The B25J filing tells a different story than the keynote. Classified under B25J 9/1674 and B25J 9/1653, the patent describes switching between open-loop control (command a position and trust the motor) and closed-loop control (measure what is actually happening at the joint and correct). The reason that switch matters: a joint that only knows its commanded position will crush whatever gets in its way, while one that closes the loop on measured torque can yield to contact.
This is the mechanism behind 'collaborative' robot arms — the ones rated to share a workspace with people. A human can push the arm aside and it gives, because the controller is reading force at the joint and reacting in milliseconds. That behavior is not magic; it is the closed-loop half of this patent doing its job.
The honest constraint is bandwidth. Force-sensitive control only works if the joint can sense and react faster than a collision develops, which puts hard demands on sensor latency and actuator response. The patent's value is in managing exactly that real-time loop, and the engineering it implies is more demanding than any spec sheet conveys.
Haddadin's work threads through a whole generation of sensitive manipulators, and this 2020 grant is a clean artifact of the philosophy: a good robot joint is not the one that hits its target hardest, but the one that knows how hard it is pushing. Every humanoid that claims to handle delicate objects is implicitly making the claim this patent makes explicit.
For readers auditing manipulation claims, the tell is whether a robot can feel. A position-controlled arm is a fast machine; a force-controlled one is a safe collaborator. The difference is a control loop, and this is one of the patents that defines it.