Abstract

We consider tracking control for multibody systems which are modeled using holonomic and non-holonomic constraints. Furthermore, the systems may be underactuated and contain kinematic loops and are thus described by a set of differential-algebraic equations that cannot be reformulated as ordinary differential equations in general. We propose a control strategy which combines a feedforward controller based on the servo-constraints approach with a feedback controller based on a recent funnel control design. As an important tool for both approaches, we present a new procedure to derive the internal dynamics of a multibody system. Furthermore, we present a feasible set of coordinates for the internal dynamics avoiding the effort involved with the computation of the Byrnes–Isidori form. The control design is demonstrated by a simulation for a nonlinear non-minimum phase multi-input, multi-output robotic manipulator with kinematic loop.

Highlights

  • In the present paper, we propose a combined feedforward and feedback tracking control strategy for underactuated non-minimum phase multibody systems

  • E) We demonstrate that the combination of the feedforward and feedback control strategies is able to achieve tracking with prescribed performance for a nonlinear, non-minimum phase robotic manipulator with kinematic loop—the controller performance of the combination is favorable compared to the individual controllers (Sect. 6)

  • We illustrate our findings by a robotic manipulator which is described by a differential-algebraic equations (DAEs) that cannot be reformulated as an ordinary differential equation (ODE) and, at the same time, has unstable internal dynamics

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Summary

Introduction

We propose a combined feedforward and feedback tracking control strategy for underactuated non-minimum phase multibody systems. Since the funnel controller presented in [39] is not feasible for nonminimum phase systems, we use an extension recently developed in [9] An important tool both in feedforward and feedback control design is the Byrnes–Isidori form, which allows a decoupling of the internal dynamics of the system. D) We present a new funnel control design for nonlinear non-minimum phase systems which only have a vector relative degree E) We demonstrate that the combination of the feedforward and feedback control strategies is able to achieve tracking with prescribed performance for a nonlinear, non-minimum phase robotic manipulator with kinematic loop (described by a DAE that cannot be reformulated as an ODE)—the controller. Performance of the combination is favorable compared to the individual controllers (Sect. 6)

Nomenclature
System class
Vector relative degree
Control methodology
Organization of the present paper
Computing the internal dynamics
The general case
Position-dependent output with relative degree two
The colocated case
A feasible set of coordinates for the internal dynamics
Servo-constraints approach
Funnel-based feedback controller
A robotic manipulator with kinematic loop
Summary and conclusion
Full Text
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