A distal mechanism for providing three degrees of freedom for a rotating handle. Three stages provide a serial mechanical linkage between a handle and a platform, which may itself be moveable in three degrees of freedom. Each stage has an axis of rotation, and the three axes intersect. The first stage is mounted to the platform in such a way as to provide rotation about the first stage axis. The first stage carries the second, allowing the second stage to rotate about its axis. The second stage carries the third stage, allowing the third stage to rotate about its axis. The third stage is fixed to the handle, and the third stage axis passes along the length of the handle. Each stage has a sensor to measure its rotation, and a tendon means of transferring torque from a remote motor to torque about the rotation axis of the respective stage. The sensors have two limited angle ranges of measurement, about 110 degrees wide and on opposite sides of the rotation. The third stage has an auxiliary sensor, mounted in quadrature to the main third stage sensor. It is connected to an idler that carries the third stage tendon. The auxiliary third stage sensor measures angles of rotation that are not measured by the main third stage sensor. The two third stage sensors together provide continuous roll measurement about the third stage axis.

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A new concept of the exoskeleton-type masterarm, composed of serial links, is introduced in the paper. To provide maximum range of human motion, several redundant joints are added to the serial links. In order to reduce the number of joints to be measured, kinematics of serial links was taken into consideration in design. Three measurable, controllable joints and three redundant free joints are used for the upper arm (shoulder), similarly to the forearm (wrist) while one measurable, controllable joint is used for the elbow. In particular, a torque sensor beam is designed for fine force reflection using the strain gauge. It detects the torque as well as its direction applied by the human operator, which allows the electric brake to be used as an actuator for force reflection. The electric brake constrains the joint movement so that the operator can feel the force. This electric brake outperforms the motor in terms of torque/weight ratio and makes the device light and compact. This masterarm measures the movement of the operator’s arm precisely, and its can be used for teleoperation with a slave robot, or as a motion planner for an industrial robot.

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