The paper addresses feedback control of actuated prostheses based on the Stewart platform parallel mechanism. In such a problem it is essential to apply a feasible numerical method to determine in real time the solution of the forward kinematics, which is highly nonlinear and characterized by analytical indetermination. In this paper, the forward kinematics problem for a human elbow hydraulic prosthesis developed by the research group of Polytechnic of Bari is solved using artificial neural networks as an effective and simple method to obtain in real time the solution of the problem while limiting the computational effort. We show the effectiveness of the technique by designing a PID controller that governs the arm motion thanks to the provided neural computation of the forward kinematics. © 2014 Elsevier B.V.

The paper addresses closed loop control of a hydraulic prosthesis for human elbow. In such a problem it is essential to obtain quick results of simulation in order to appreciate the dynamic behavior of the entire system. In this paper, the forward kinematics problem for a hydraulic prosthesis for human arm developed by the research group of Polytechnic of Bari is solved using artificial neural networks as an effective and simple method to obtain in real time the solution of the problem without an excessive computational effort. We show the effectiveness of the method by designing a PID closed loop control that effectively controls the arm thanks to the provided neural computation of the forward kinematics.

A novel set up is proposed to measure the energy release rate versus crack propagation speed in viscoelastic materials. The new test is referred to as the square sample tear test. In comparison to other techniques as the pure shear specimen and the pure tensile specimen tests, the square sample geometry guarantees at the same time: (i) a constant flux of elastic energy at the crack tip, (ii) the full development of the annular dissipative region around the crack tip, where the material is in the transion region of the viscoelastic response spectrum. Both conditions allow to precisely control the crack propagation speed and to test the predictions of existing theories. By employing the new set-up we measure the energy release rate as a function of the crack propagation speed. We also measure with a high precision infrared camera the increase of temperature at the crack tip, showing that, notwithstanding the low speed regime considered during the experiments, the viscoelastic dissipation at the crack tip leads to a measurable temperature increase of about 1◦C

This paper presents a new mechanical architecturefor elbow powered myoelectric prostheses. New requirements for active prostheses are energetic autonomy, low production cost and human like behavior. On the scientific panorama very few examples of parallel device are available. We show an alternative device, with a simple mechanical hardware, to simulate the movements and the dynamic of human elbow. We investigated on wires used like tendons in mechanical elbow prostheses. The wire transmission architecture allows two linear actuators to control the motion of the forearm along two degrees of freedom in an enhanced work volume. The device, indeed, is designed to provide in the same mechanism flexion/extension and pronation/supination movement, which are usually decoupled in elbow and wrist mechanisms in usual commercial devices.