Identification and control of a 3-X cable-driven manipulator inspired from the bird neck

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

SMA Antagonistic-Micro-Wire Bundle: First Measurement Results

Shape memory alloys (SMA) are used as an attractive technology in the field of actuators and sensors due to their versatile geometry, lightweight, high energy density, and low cost. The thermal activation principle, however, makes SMA application generally suitable for low-frequency (few Hz) regimes. In this work, a novel SMA-based antagonistic actuation system and its manufacturing process are presented for the first time. The main feature of the novel actuator concept is the possibility of being operated at frequencies up to at least 20 Hz. It spares the usual complex and time-consuming manufacturing of such a system. First parameter studies of a rotary actuation system are performed. The relationship existing between the pulse energy, frequency, and the resulting rotation angle is investigated through an extensive experimental campaign.

Explorative study on adaptive facades with superelastic antagonistic actuation

Glass facades and enclosures are highly attractive structures with increasing popularity between architects and engineers. These structures show very specific design requirements so as to guarantee an efficient interaction with the other building components. This is especially true in the case of "adaptive" glass systems, with continuously changing configurations according to a given design criteria. The main goal of this explorative study is the design of an adaptive facade module with antagonistic actuation. The geometry of the glazing system is controlled by pairs of superelastic cables actuated against each other in a reversible way.Superelasticity is here exploited so as to improve the structural behavior of the facade system subjected to wind loads. The efficiency of the proposed design concept is demonstrated via Finite-Element numerical analyses and also from test data obtained from an experimental prototype. It is shown that the the proposed control approach can yield substantial structural enhancements and benefits for the adaptive facade module, which are substantiated by important reductions of maximum deformations and stresses in the cladding elements.