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Identification of the Inertial and Geometric Parameters of Stäubli Robots

In this thesis report we present two main aspect of the control of a robot, the identification of the inertial parameters of the load and the geometric calibration of a manipulator. The knowledge of the values of the inertial parameters can be used to tune the control law parameters in order to improve the dynamic accuracy of the robot. They can also be exploited to verify the load transported by the robot. The methods presented have been validated using Stäubli TX 40 robot of the IRCCyn. The experimentation has been carried out using data collected from the industrial control system (version CS8 and LLI) of the manufacturer. This version allows to have access to joint positions, velocities and torques. The methods presented are based on solving linear system of equations. Calibration of a robot is the process by which we identify the real geometrical parameters in the kinematic structure of a robot. Hence, the geometric calibration of robots is the process by which the parameters defining the base frame parameters, link parameters and end-effector parameters are precisely identified, as for example the position and orientation of the joints of the robot. The methods presented have been validated using Stäubli RX 130 robot. The experimentation has been carried out using data collected from the industrial control system (version Krypton) of the manufacturer.

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2 Introduction A robot is an automatically controlled, reprogrammable, multipurpose mechanical system with several degrees of freedom, which may be either fixed in place or mobile. It has been widely used so far in various industrial automation applications. The control and simulation of robots requires the development of different mathematical models. Several levels of modeling - geometric, kinematic and dynamic - are needed depending on the objectives, the constraints of the task and the desired performance. Obtaining these models is not an easy task. Using these models in control and simulation requires efficient and easy-to-use algorithms to estimate the values of the geometric parameters and the dynamic parameters of the robot. The design and control of a robot requires the computation of some mathematical models such as:  transformation models between the joint space and task space. These transformation models are very important since robots are controlled in the joint space, whereas tasks are defined in the task space. Two classes of models are considered: direct and inverse geometric models, which give the location of the end-effector as a function of the joint variables of the mechanism and vice versa; and direct and inverse kinematic models, which give the velocity of the end-effector as a function of the joint velocities and vice versa;  dynamic models giving the relations between the input torques or forces of the actuators and the positions, velocities and accelerations of the joints. In recent literature for robots, the dynamic models are required in most of the advanced control schemes. Certain criterion namely precision, performance, stability depends on the accuracy of the parameters which describes the dynamic model. Furthermore these values are necessary to simulate the dynamic equations. The dynamic model of robots plays an important role in their design and operation [1].

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Laura Lucia Rita Bellino Contatta »

Composta da 154 pagine.

 

Questa tesi ha raggiunto 70 click dal 20/10/2011.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.