The WAM arm : modelling, control and its application in a HMI based on gaze tracking

Abstract

In this thesis we describe the design and implementation of a Human Machine\nInterface (HMI) based on gaze tracking proposed to control robot prostheses. Robot\nmanipulators hold a strong similarity with arm prosthetics, we used a 7 degrees\nof freedom (DOF) whole arm manipulator to test our HMI in the execution of\nreaching and grasping tasks. We showed that the interface worked under different\ncontrol strategies using several velocity profiles. The system was tested by ten\nsubjects with encouraging results. We analysed the performance of the 7-DOF\nrobot manipulator in order to determine the suitability of its application in the\ndevelopment of this project. The original setup of the manipulator worked under\njoint Proportional and Derivative (PD) control but considering the results of the\ninitial analysis of the system we proposed two alternative control strategies aimed\nto improve the performance of the manipulator: a feedforward friction compensation\ntechnique and joint Proportional Integral and Derivative control (PID). We created\na dynamic model of the 7-DOF manipulator in Simmechanics in order to have a\nbetter understanding of the system. The friction phenomena of the manipulator\nwas identified, represented through a fitted model and included in the system’s\nmodel with the aim of incrementing its accuracy with respect to the real system.\nThe characteristics of the model made it suitable to test and to design control\nstrategies for motion and friction compensation in MATLAB/Simulink. The model\nof the system was validated using data from the real robot arm and it was used\nlater to tune the PID controllers of the joints of the 7-DOF manipulator using\nIterative Feedback Tuning (IFT). Both experimental data and model simulations\nwere used for the tuning procedure considering two different approaches. The data\nobtained from the friction identification process was used to implement a module for\nfeedforward friction compensation over the pre-configured joint PD control of the\nmanipulator. The responses of the system when using joint PID control and joint\nPD control with gravity and friction compensation were compared in the execution\nof motion tasks.