In a robotic arm structure (10) which includes at least two links (link 1, link 2), theta motion is provided about a primary axis (z1) at the proximal end portion of the proximalmost link (link 1). R motion proceeds radially from the primary axis (z1) whereby the distal end portion of the distalmost of the links (link 3) can be moved in a radially extending straight line. An end effector (18) is pivotally mounted for rotation relative to the distal end portion of the distalmost link (link 3) about an end effector axis which is parallel to the primary axis (z1). The structure (10) is improved by adding one or more of yaw, pitch and roll motors (servo motor 3) for rotating the wrist of the arm (10) about the respective axes. A sensor array senses the r, theta , z and one or more of yaw, pitch and roll motions and creates and transmits electronic signals representative thereof to a computer controller (96) which monitors and controls the r, theta, z and one or more of yaw, pitch and roll motions. Non-radial straight line motion and three-dimensional motions are possible. This has applications in picking up semiconductor wafers, flat panel displays and data storage disks even if the object is misaligned and/or the holding cassette or work station is misaligned from the usual operation plane of the arm (10).