Experimental investigation on high-performance coordinated motion control of high-speed biaxial systems for contouring tasks

The recently developed global task coordinate frame (TCF) is utilized to synthesize a high-performance contouring controller with cogging force compensation for a linear-motor-driven biaxial gantry to test the practically achievable high-speed/high-accuracy contouring performance. Specifically, the approach employs the global task coordinate formulation to meet the stringent control performance requirements for high-speed and large-curvature coordinated contouring tasks. Moreover, the approach explicitly takes into account the specific characteristics of cogging forces existed in linear motors for the controller design as model compensation to further improve practical contouring performance. Physically intuitive discontinuous projection modifications are used to ensure all the on-line estimates within their known bounds. Robust control terms are also constructed to effectively attenuate the effect of model compensation errors due to various uncertainties for a theoretically guaranteed transient performance and steady-state tracking accuracy in general. Comparative experiments are carried out on an industrial linear-motor-driven biaxial gantry and the results verify the effectiveness of the proposed cogging force compensations - a contouring tracking accuracy improvement of 30% is achieved. Experimental results also validate the rather excellent contouring performance of the proposed controller for high-speed/high-accuracy contouring tasks in actual implementation in spite of various parametric uncertainties and uncertain disturbances. (C) 2011 Elsevier Ltd. All rights reserved.