Designandmodelingofaflexibletestbedforuse in control system analysis and verification Greg Mason a, * , Anawat Pongpunwattana b , Martin Berg b a Department of Mechanical Engineering, Seattle University, Broadway and Madison, Seattle, WA 98122, USA b Department of Mechanical Engineering, University of Washington, P.O. Box 352600, Seattle, WA 98195, USA Received 2 October 2000; accepted 6 April 2001 Abstract This paper describes a test bed specifically designed for studying the effects of nonlinear friction, backlash, and drive train flexibility on structurally flexible electro-mechanical sys- tems, and for developing control algorithms that will compensate for nonlinear friction, backlash,anddrivetrainflexibilityinstructurallyflexibleelectro-mechanicalsystems.Thetest bedhasamodularandadjustabledesign.Friction,backlash,andflexibilitycanallbevariedor disabled.Amathematicalmodelofthedynamicsofthetestbedisalsodescribed.Thismodel includesstiction,Coulombfriction,backlashanddrivetrain,andlinkflexibility.Themodelis verified via comparisons of model-predicted and experimental responses. Ó 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction A control system design for real world mechanical systems is complicated by nonlinear phenomena such as stiction and backlash. A common approach is to overdesign a controller, based on a linear model, in anticipation that the controller performancewilldegradeinthepresenceoftheunmodelednonlinearities.Thereare several difficulties with this approach. First, the overdesigned controller often re- quires higher bandwidth than a design which directly accounts for nonlinearities, resulting in higher actuator costs. Second, this approach assumes that the controller Mechatronics 12 (2002) 891–904 * Corresponding author. Fax: +1-206-296-2179. E-mail address: mason@seattleu.edu (G. Mason). 0957-4158/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0957-4158(01)00028-9