Using Pose-Dependent Model Predictive Control for Path Tracking with Bounded Tensions in a 3-DOF Spatial Cable Suspended Parallel Robot

Abstract

This paper proposes the preliminary results on a novel control architecture based on model predictive control (MPC) for cable-driven parallel robots (CDPRs) and applies them to a three degrees of freedom (3-DOF) robot with a suspended configuration, leading to a cable-suspended parallel robot (CSPR). The goal of the control scheme is ensuring accurate path tracking of the reference end-effector path, while imposing a priori positive cable tensions. To handle the nonlinearities characterizing the dynamic model that governs this kind of multibody system and to keep the computational effort low, a position-dependent MPC algorithm with an embedded integrator is designed to compute the optimal cable tensions required to track the end-effector commanded path. Such tensions must belong to the feasible domain defined through a lower bound, which is slightly greater than zero, to ensure that cables pull the end-effector, and an upper bound, to represent the maximum stress that cables can withstand without breaking. The resulting controller is nonlinear, although it performs a local linearization in the prediction at each time step to reduce the computational effort. The optimal tensions are then transformed into the commanded motor torques through the inverse dynamic model of the servomotors driving the winches, since no force measurement is adopted in the controller implementation. The control architecture is designed and numerically validated through a spatial CSPR with lumped end-effector, and driven by three cables (i.e., with a non-redundant configuration). Four different paths are assumed to highlight various features of the proposed controller.

Model predictive control for path tracking in cable driven parallel robots with flexible cables: collocated vs. noncollocated control

“…In this work, a novel control architecture based on MPC is proposed for precise path tracking control in CDPRs by investigating the more challenging case of a fully-actuated, nonredundant robots with suspended configuration. Some preliminary results of this research have been proposed in [19,20] by applying the controller to an ideal system with rigid cables and by neglecting the presence of the actuator and sensor dynamics. An extension of the control scheme, with an enhanced architecture, is here proposed to cope with a more realistic scenario by also providing a comprehensive approach for the controller design and analysis.…”

Load observer for cable failure detection in Cable Driven Parallel Robots: a machine learning approach

“…Cable driven parallel robots (CDPRs) are gaining an increasing attention in the field of multibody system dynamics due to their benefits in terms of large workspaces and payloads, and small energy requirement. On the other hand, the features of cables set challenges in design [1,2], modeling [3,4], motion planning [5] and control [6,7]. Besides these difficulties, CDPR can be affected by cable failures that severely compromise the robot operation and cause hazardous situations that might result in damages to the system itself and the surroundings.…”

Synchronization Control with Dynamics Compensation for Three-Axis Parallel Motion Platform

“…Despite the parallel platform offering numerous advantages, it presents certain challenges concerning the mutual pulling and control difficulties among joint motors during motion [7,8]. To overcome these issues, advanced modeling theories and control strategies need to be researched and developed continuously to enhance the system's motion performance.…”