Experimental study on the model-based control of a 2-degree-of-freedom spherical parallel robot camera stabilizer based on multi-thread programming concept

Abstract

This article aims at proposing a real-time controller for a camera stabilizer using a 2-degree-of-freedom spherical parallel robot with simultaneous display of the control results using multi-threading programming concept. The main contribution of this article can be regarded as employing (a) a 2-degree-of-freedom spherical parallel robot as a camera stabilizer, (b) introducing approximated model and Jacobian model, and (c) using multi-thread programming in order to create equal conditions for comparing accuracy of designed controllers and simultaneous controlling and running of graphical user interface. The experimental setup consists of a 2-degree-of-freedom spherical parallel robot in which a camera is attached to its end-effector plus a 3-degree-of-freedom passive rotational platform, which provide the possibility to apply random perturbations on the base of the foregoing 2-degree-of-freedom spherical parallel robot. At the end-effector of the robot, a 6-degree-of-freedom sensor is installed which sends rotational data to a micro controller, wirelessly. To this end, transceiver boards are constructed to create connection between PC controller and micro-controller. A PC controller is designed in order to ensure that the installed cameras orientation will remain fixed for a prescribed orientation. In this regard, a controller without encoder and a Jacobian-based controller are employed for the under study spherical 2-degree-of-freedom parallel robot. Then, multi-thread programming is used to eliminate complexities of controller structures. Based on the experimental results obtained by implementing both controller, outputs are compared and mean error of each control method and the related RMSE are reported for the sake of proposing the most promising controller.