In our previous work we have introduced the Distributed Active/Semi-Active actuation concept. This paper presents the design of a novel three Degrees-of-Freedom (DOF) robot manipulator based on the DASA actuation approach. The robot is developed as a proof-of-concept prototype intended to demonstrate the capacity of the DASA approach to achieve a high degree of interaction safety as well as performance. Magneto-Rheological (MR) clutches form the basis of the Semi-active actuation component, while a unidirectional motor provides the active drive for the robot. An antagonistic clutch configuration is implemented at the joints to achieve bi-directional actuation without reversal of the motor. MR clutches have been shown to exhibit excellent torque-to-inertia and torque-to-mass ratios making them likely candidates for the development of human-safe actuators. In this paper, the safety characteristics of the DASA approach are qualitatively discussed. Experimental results highlighting the performance capability of the developed robot are given.

This paper presents the design and development of a novel two Degrees-Of-Freedom (DOF) safe robot manipulator. Magneto-Rheological (MR) clutches are incorporated in the design to enable antagonistic actuation at the joints. A single unidirectional motor supports bidirectional actuation of all joints. Unlike most current safe robots, high quality actuation is preserved, while the manipulator weight and effective inertia are reduced. This is achieved by relocating the driving motor to the base of the robot. Moreover, MR clutches have been shown to pose superior torque to mass, and torque to inertia characteristics over conventional servo motors, further contributing to the reduction of manipulator mass and inertia. The manipulator exhibits both high performance and intrinsic safety as a result of mechanically passive dynamics. A set of experiments is performed to validate the manipulator performance.

In this paper we present the design and experimental validation of a Magneto-Rheological (MR) clutch developed for servo control applications in human friendly robotic systems. The clutch is developed as a practical prototype for potential industrial applications in the low to mid torque range. Conventional servo motors have been shown to lack the necessary properties to deliver intrinsically safe actuation for physical interaction with humans. Several human safe actuation paradigms have been proposed, however, tend to increase mechanical complexity as well as require more sophisticated control strategies. Furthermore, many of the proposed solutions have failed to demonstrate a practical implementation that provides the necessary performance capabilities required for practical applications in automation, as well as more general servo control applications. MR clutch devices have been shown to provide favorable characteristics for such tasks, however have focused primarily on haptic systems or low torque applications. The developed prototype MR clutch is capable of transmitting up to 75 Nm, and has a control bandwidth of approximately 30 Hz.

For several decades now, the robotics industry has postulated the emergence of a new breed of manipulators capable of safely interacting with humans. The integration of robots into human environments has always possessed a unique set of challenges. The primary concern has always been for the safety of the human coworkers. Insuring their safety has led to the desire to design manipulators with intrinsic safety characteristics. Specifically, it is noted that modern `human-safe' manipulators are successful if they have minimized both their weight and reflected actuator inertia. The leading research accomplishing this relies on complex actuation systems. Such systems commonly suffer from degraded performance and high cost of development. Magneto- and electro-rheological fluids are a class of smart-materials that can instantaneously, and reversibly alter their rheological properties under the influence of an applied field. Devices developed with such fluids are known to possess superior torque-to-inertia characteristics over conventional servo systems. Moreover, their simple mechanical construction suggests that manipulators using such devices could be developed at a lower cost. In this paper, we will discuss the potential benefits rheological fluids can bring to the field of human friendly manipulators.