Stewart-Gough Platform: Design and Construction with a Digital PID Controller Implementation

This document presents the design of a digital PID control for a Stewart-Gough platform, delimited by six degrees of freedom (DoF) that allow the final effector to have displacement in the XYZ axes and rotation with warpage, pitch, and yaw restrictions. It includes the study and resolution of the direct and inverse kinematics of the platform, as well as the workspace described by the final effector and its corresponding simulation of movements and joints to study extreme points and possible singularities. From the definition of characteristics, the CAD design generated from the generalized mathematical model of the public domain, and the general selection of materials for the construction of the functional prototype, a study of applied forces is generated to observe the points with stress concentrators, the safety factor, and possible deformations. The estimation of the sampling period for the selection of the microcontroller and an approximate definition of the response time are also considered. The development of this prototype and its documentation are proposed as didactic material for the study, design, and control of parallel mechanisms.

Calibration of Reconfigurable Stewart-Gough Platform for Mobile Machining Application

This paper considers the problem of calibrating a reconfigurable Stewart-Gough platform for mobile machining applications using partial information measurements. The motivation for the work comes from the wind turbine industry, where cost reduction for machining of large components is desired. In the paper kinematic description of an actual prototype machine, together with description of partial information calibration methods of which simulated and experimental results are shown. Results of the proposed calibration methods, where only positional data of the machine was measured by a laser tracker, showed great improvement of the machine performance. Results from experiments showed achievable positioning tolerances of maximum 65μm after an initial factory calibration, and 146μm for a secondary calibration, where fewer parameters were included to reduce lost machining time during configuration change. Machining tests furthermore indicated that it is possible to continue machining across different configurations.