Tracking control for end‐effector position and orientation of structurally flexible manipulators

Abstract

A simple and effective feedback control strategy is presented for end‐effector position and orientation tracking of structurally flexible manipulators free of external forces as in space applications. The fully feedback‐driven approach employs an augmented dynamical description in which derivatives of the control inputs are included in the state. This ensures smooth control inputs to the manipulator joints. The feedback law uses gain scheduling of a series of steady‐state regulators derived by considering the manipulator at intermediate (nominally rigid and stationary) configurations along the desired trajectory. The performance of the control method is demonstrated in simulations of a planar three‐link manipulator system. Examples show that the controller can be applied successfully in discrete‐time, and that spillover does not appear to be a problem.

The Kinematic Sensitivity of Robotic Manipulators to Joint Clearances

“…For the evaluation of the pose errors on the moving-platform, the small-displacement screw taking P i onto P ′ i has to be expressed in the reference attached to the fixed base, i.e., F i,1 . Let δ p i |F i, 1 be this smalldisplacement screw expressed in F i,1 :…”

“…As indicated in refs. [1,2], the errors due to manufacturing, assembly and compliance can be compensated through calibration and model-based control. Joint clearances, on the contrary, exhibit low repeatability, which generally makes their compensation difficult.…”

Error Modeling and Experimental Validation of a Planar 3-PPR Parallel Manipulator With Joint Clearances

“…Wei and Simaan proposed an approach for designing inexpensive planar parallel robots with prescribed backlash-free workspace by using preloaded flexible joints to replace the passive joints [14]. Among the sources of errors, the influence of assembly and manufacturing errors and actuation errors can be eliminated as indicated in [5,[15][16][17] by calibration, except joint clearances due to its low repeatability. It means that the pose errors due to joint clearances require a special consideration.…”

Motion control of flexible-link manipulators

“…Kwon and Book [10], De Luca and Siciliano [11], Feliu and Rattan [12], Ge et al [13], Qian and Ma [14], Yeung and Chen [15], and Morgul [16] proposed tip point motion control strategies for flexible one-link manipulators. In the trajectory tracking control studies for multi-link manipulators by Carusone and D'Eleuterio [17], Ider et al [18], Pfeiffer [19], Yim [20], and Zhao and Chen [21], various control strategies were developed making use of the linearized dynamic equations.…”