Abstract: The subject invention provides a parallel or closed loop mechanism for moving and positioning a member in space. The mechanism includes three branches each provided with at least two link members being serially connected together by a spherical elbow joint whereby the first and second link members are rotatable with respect to each other about any axis passing through a center of the first joint. The mechanism is provided with actuators for moving each branch and the first links of each branch are rigidly connected at an end portion thereof to the actuator means. The mechanism includes three revolute joints each defining a longitudinal axis of rotation. Each revolute joint is connected to an associated second link member so that the longitudinal axes of all third joints intersect at a point and the revolute joints are interconnected so that the three branches form three parallel or closed loops.

Abstract: A four degree of freedom manipulator which comprises a pair of elongate rigid legs connected by a joint. The joint acts as an end-effector or an end-effector is attached thereto, The legs effectively intersect at a point in the joint. The positioning end of each leg is attached to a two degree of freedom positioning mechanism that can position it in a two dimensional plane. The connection between the leg and the positioning mechanism has two passive rotational degrees of freedom. Preferably five bar mechanisms are used as the positioning mechanisms. The manipulator can control the position and orientation of an end-effector.