Deformation Control in Rest‐to‐Rest Motion of Mechanisms with Flexible Links

Abstract

This paper develops and validates experimentally a feedback strategy for the reduction of the link deformations in rest-to-rest motion of mechanisms with flexible links, named Delayed Reference Control (DRC). The technique takes advantage of the inertial coupling between rigid-body motion and elastic motion to control the undesired link deformations by shifting in time the position reference through an action reference parameter. The action reference parameter is computed on the fly based on the sensed strains by solving analytically an optimization problem. An outer control loop is closed to compute the references for the position controllers of each actuator, which can be thought of as the inner control loop. The resulting multiloop architecture of the DRC is a relevant advantage over several traditional feedback controllers: DRC can be implemented by just adding an outer control loop to standard position controllers. A validation of the proposed control strategy is provided by applying the DRC to the real-time control of a four-bar linkage.

An Updating Method for Finite Element Models of Flexible‐Link Mechanisms Based on an Equivalent Rigid‐Link System

“…e use of linearized models is very satisfactory in the case of small deformations about operating points and hence can be successfully used in the synthesis of control schemes and state observers [23,24]. Additionally, mode shapes and eigenfrequencies can be easily computed.…”

Reduced‐Order Observers for Nonlinear State Estimation in Flexible Multibody Systems

“…However, flexibility often results in unwanted vibrations that limit motion accuracy and imposes advanced control schemes accounting for the flexible dynamics. High-performance control schemes are typically model-based [1][2][3][4][5] and often require the knowledge of a large set of state variables [3][4][5]. For example, a common application requiring the whole state vector (i.e., position and speed of all the state variables) is active control through state feedback to assign the desired modal characteristics [6,7].…”