This paper proposes a new kind of lightweight manipulators suitable for safe interactions. The proposed manipulators use anti-parallelogram joints in series, referred to as X-joints. Each X-joint is remotely actuated with cables and springs in parallel, thus realizing a tensegrity one-degree-offreedom mechanism. As compared to manipulators built with simple revolute joints in series, manipulators with tensegrity X-joint offer a number of advantages, such as an intrinsic stability, variable stiffness and lower inertia. This new design was inspired by the musculosleketon architecture of the bird neck that is known to have remarkable features such as a high dexterity. The paper analyzes in detail the kinetostatics of a X-joint and proposes a 3-degree-of-freedom manipulator made of three such joints in series. Both simulation results and experiment results conducted on a test-bed prototype are presented and discussed.

This paper is devoted to the control and identification of a manipulator with three anti-parallelogram joints in series, referred to as X-joints. Each X-joint is a tensegrity one-degree-of-freedom mechanism antagonistically actuated with cables and springs in parallel. As compared to manipulators built with simple revolute joints in series, manipulators with tensegrity X-joint offer a number of advantages, such as an intrinsic stability, variable stiffness and lower inertia. This design was inspired by the musculosleketon architecture of the bird neck, which is known to be very dextrous. A test-bed prototype is presented and used to test computed torque control laws. Friction and cable elasticity are modelled and identified. Their effect on the performance of control laws is analyzed. It is shown that in the context of antagonistic actuation and light weight design, friction plays a leading role and the significance of modelling cable elasticity is discussed