In this paper, the feedforward controller design problem for high-precision electromechanical servo systems that execute finite time tasks is addressed. The presented procedure combines the selection of the fixed structure of the feedforward controller and the optimization of the controller parameters by iterative trials. A linear parametrization of the feedforward controller in a two-degree-of-freedom control architecture is chosen, which results in a feedforward controller that is applicable to a class of motion profiles as well as in a convex optimization problem, with the objective function being a quadratic function of the tracking error. Optimization by iterative trials avoids the need for detailed knowledge of the plant, achieves the controller parameter values that are optimal with respect to the actual plant, and allows for the adaptation to possible variations that occur in the plant dynamics. Experimental results on a high-precision wafer stage and a desktop printer illustrate the procedure.

Abstract-The control design for the variator in a pushbelt continuously variable transmission (CVT) is investigated. The variator enables a stepless variation of the transmission ratio within a finite range. A conventional variator control design is typically obtained by the use of a variator model, which is highly uncertain and, therefore, limits the variator efficiency. In this paper, a variator control design is proposed, which simultaneously satisfies the variator control objectives: 1) tracking a transmission ratio reference, 2) optimizing the variator efficiency. Furthermore, the variator control design, which consists of a combination of extremum seeking control (ESC) and tracking control (TC), only uses measurements from sensors that are standard. Experiments illustrate that the variator control design achieves the variator control objectives and show that a conventional variator control design is outperformed.

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