Vector-based dynamic modeling and control of the Quattro parallel robot by means of leg orientations

Abstract

One of the key steps in high-speed control of a parallel robot is to define an efficient dynamic model. It is usually not easy to have such a model for parallel robots, since many of them have complex structures. Here, we propose a vector-based approach, which employs the robot leg orientations, to obtain a simplified inverse dynamic model. At the least, this vector-based methodology is pioneering, when combined with the observation of orientations by a calibrated camera, in the sense of solving the entire control-oriented (hard) modeling problem, both kinematics and dynamics, in an almost algebraic manner through the knowledge of only a nominal set of image features: the edges of the robot legs and their time derivatives. Proposed method is verified on a simulator of the Quattro robot with a computed torque control where the leg orientations are steered.

Development of a Vision-enabled Aerial Manipulator using a Parallel Robot

“…There are many papers that propose the kinematics of the parallel manipulator using the geometric relationship only. [5][6][7] In this paper, the inverse kinematics of a quattro-parallel manipulator is derived as the vector formulation.…”

Dynamic control of the Quattro robot by the leg edges

“…In previous works [6], [7], an algebraic expression for the inverse dynamic of the Quattro robot was derived through the following procedure:…”

“…Indeed, once all the variables are known, the proposed models make only use of linear algebra. The variables related to the actuators and the end-effector can linearly be expressed from the known variables related to the lower-legs and the known constant parameters [6].…”

“…In Cartesian space, the end-effector pose χ of the Quattro, which is calculated through the linear function f χ as in [6] by using the projection-lines of the lower-legs rather than through a non-linear pose estimation from a set of points on a grid, is used as a sensor-signal in control (see Fig. 5).…”

“…This variable set should let the modules be right in step with one another, namely, make them converge to a unified single system that governs the parallel robot right on target. In this paper, the control module has been explored further in detail so as to incorporate it smoothly into and complete the desired unified system, where the integration of sensing and modeling parts have already been discussed in our previous works [6], [7], [8]. The expected contributions of this work are: (i) to propose a dynamic control through the leg contour pixels (edgels) of a parallel robot for potentially better performance, (ii) to avoid using an artificial pattern in dynamic tracking, while the parallel robot turns itself into a pattern, (iii) to increase the robustness of dynamic control since the imagespace is resistant to errors, and (iv) to give intuitions that might shed light on a complete image-based (2D) dynamic modeling and control of parallel robots.…”