Joelho magneto-reológico para próteses transfemurais: prototipagem digital, fabricação e identificação experimental

Abstract

The movement performed by the knee is essential to reproduce the proper gait in transfemoral prostheses and to allow greater mobility of the amputee. The development of knee prostheses has been extensively studied in the last few decades. In general, knee actuators can be divided into three major groups: Passive, semi-active and active. In passive and semi-active knees, the amputee compensates the lack of active torque with additional hip and trunk movements. Passive prostheses, for example, do not reproduce gait pattern properly, determining an expense of 60% more metabolic energy. Despite advances and research in assistive technology and disadvantages of the semi-active and passive actuators, developed active knees still have some limitations, such as weight, low active and resistive torque and high energy consumption. This doctoral thesis proposes the development of an active magnetorheological (MR) knee for transfemoral prostheses. MR fluids are smart materials which can have their properties controlled by an induced magnetic field. MR fluids have been used in devices development such as shock absorbers for vehicle suspensions, valves, and prostheses, for they present low power consumption and high torque to weight ratio. The MR Knee consists of a motor unit (EC 60 motor, CSG-14-100-2a harmonic drive, and MR clutch) in parallel with a MR brake, so it can works as motor, clutch, or brake. During the gait the control of the knee can be done independently by the motor unit or by the MR brake, taking the best of each subsystem. Initially, the MR clutch and brake design was developed. The design was optimized using a PSO (particle swarm optimization) algorithm, aiming to reduce their weight and energy consumption. Then the digital prototype of the MR Knee was developed. The prototype properties (dimensions, mass and inertia) were used to build the dynamic model for simulations and implementation of a controller. After analyzes, the MR Knee was fabricated according to the digital prototype and tested on a test bench. The experimental dynamic model of the subsystems was measured and a preliminary torque control was developed. The results show that the MR Knee is promising for the proposed applications, which require multiple functions with compact size, low weight, low energy consumption and quick response time