Most modern robotic systems are fast and repeatable position controlled machines. However, because of their inability to interact safely, robustly and in a versatile manner, they mostly remain confined to controlled areas where they execute specific preprogrammed actions. Providing high performance motion simultaneously with the ability to physically interact significantly remains a challenge.

Today's robotic systems are mostly rigid and position-controlled machines designed to operate in structured environments. To extend their application domains to partially unknown, dynamic, or anthropic environments, improved physical-interaction capabilities are required. In this new context, to blend the requirements for safety, robustness, and versatility is often a challenge, in part, because commonly available actuator technologies are inadequate. This paper presents our solution with the introduction of the dual-differential rheological actuator (DDRA) concept, which is based on the synergistic combination of an electromagnetic (EM) motor and two differentially coupled magnetorheological (MR) brakes. This paper describes the approach and the prototype design. It then discusses performances in force, motion, and interaction control.