Abstract: A robot arm includes a first kinematic chain from a first actuator to an end-effector platform, providing a first degree of freedom for positioning the end-effector platform; a second kinematic chain from a second actuator to the end effector platform, providing a second degree of freedom for positioning the end effector platform; a third kinematic chain from a third actuator to the end-effector platform, providing a third degree of freedom for positioning the end-effector platform; and a fourth kinematic chain configured to transmit movement of a fourth actuator to a corresponding orientation axis of an end-effector. The fourth kinematic chain includes an orientation linkage mounted to an inner arm assemblage via at least one bearing mounted to the end-effector platform, wherein the orientation linkage includes an end-effector rotation link and joints that provide at least two degrees of freedom for each end joint of the end-effector rotation link.