Control Strategies for a Cable-Driven Parallel Robot with Varying Payload Information

Abstract

A suspended Cable-Driven Parallel Robot (CDPR) composed of eight cables and a moving platform (MP) is used in a pick-and-place application of metal plates with different shapes, sizes and masses. In order to ensure robust control despite mass variation, several combinations of control schemes and control laws have been experimented on a prototype at IRT Jules Verne, France. The main objective of this paper is to provide recommendations on the selection of a control strategy depending on the available information on the carried mass, and the presence or absence of force sensors. Three scenarios are considered representing a degradation of the information on the carried mass to observe the impact on the performance of applicable control strategies. In a first case, force sensors are assumed available to measure cable tension, allowing the real-time estimation of the carried mass. In a second case, the mass of the MP is known, but not the mass of the carried metal plate whereas the third case considers no information at all on both the MP and the carried metal plate. The tested control laws include a standard proportional-derivative controller (PD), and a recently developed nonlinear controller balancing between sliding mode and linear algorithms (SML). The performances of each control strategy are analyzed along a test trajectory for several payloads, and a decision tree is proposed.

Modeling, analysis and control of robot–object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

“…The complementarity constraint manages the taut/slack state of the cable (cables can pull, not push), and the model is complete if an impact model is added to (70) (inelastic collisions are usually chosen [242,243]). The same approach can be used to model tethered satellites, cable-driven robotic systems in crane configuration [48,49,244,245,246], helicopters or quadrotors with cable-suspended loads [242,247,248,249,250], manipulation of objects with cables [218,219,77], gantry cranes with liquid-sloshing payloads [251,252] (then the object has a complex dynamics, which can be approximated with multibody dynamics models [253,Chapter 5]). As explained in [6, Example 1.6], the cables can also be controlled with a force exerted at one tip, or with one of the tip's position (e.g, the attachment point on the aircraft example).…”

“…Manipulation with quadrupeds and cables [219] typically falls into the MR-MO class: quadrupeds (each comprising a robot and an object part), the manipulated object (subject to friction), and the cables (creating a complementarity constraint). A cable-driven parallel robot [245] where the frame to which cables and winches are bound, is itself floating (in addition to the internal moving platform), also has an MR-MO structure. Manipulation of floating objects with tugboats [77] typically yields MR-MO systems.…”

Human-cable collision detection with a cable-driven parallel robot

“…These are first due to the imprecise knowledge of the friction model and the lack of an elasticity model of the cables which imply a reduced positioning accuracy resulting in model geometry errors, especially in the computation of the Wrench matrix. Adding such an elastic model has shown important accuracy improvements for suspended CDPRs [30]. Neglecting the acceleration and Coriolis terms also induces errors on the model, however, the error is more significant when 560 the cable is stopped, suggesting a predominant impact of the friction model over the errors related to the dynamic effects.…”

Performance and interaction quality variations of a collaborative Cable-Driven Parallel Robot

“…CDPRs provide large translation workspaces and are easier and more affordable to deploy than classical parallel robots. CDPRs are well fitted for tasks requiring a large translational workspace [3], a high payload/weight ratio [4,5] or reconfigurability [6]. CDPRs are adapted to industrial tasks such as painting [6], intra-logistics [7] and large part printing [8].…”