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The extended pole placement (EPP) method extends the well-known pole placement method to digital servo-control with known control inputs. A servo-control system designed using the EPP method achieves an accurate command response through the use of a noncausal reference model and an accurate approximation of nonminimum-phase zeros. The phase error of the command response between the desired output and the actual output may be made arbitrarily small, while its gain extends uniformly to a selectable bandwidth. A selectable feedforward bandwidth is important in controlling flexible structures where unmodeled resonances might be excited by rough feedforward inputs. Experimental results on a machine tool slide show that a controller designed by the EPP method yields better servo performance for cornering and contour tracking tasks than an E-filter-enhanced zero phase error tracking controller.

Mechanical descriptor systems, i.e., constrained mechanical systems, have many applications in practice. This paper studies the control of mechanical descriptor systems. First, a class of the state feedback controllers assigning the finite poles of mechanical descriptor systems at any desired locations is presented. Second, based on the degrees of freedom of pole-assignment controller, an optimization method for designing the controller that assigns the finite poles of closed-loop mechanical descriptor system and simultaneously minimizes a quadratic performance index is proposed. The necessary condition for the pole-assignment controller to be optimal is derived and the corresponding algorithms are discussed. An example is given to illustrate the validity of method in this paper.

The frequency domain design methodology developed in Jayasuriya and Franchek (1988) for the synthesis of controllers that maximize the allowable size of an unknown-but-bounded disturbance in the presence of several time domain constraints is revisited. It is shown that (i) the basic ingredients of the methodology stays essentially the same for systems with nonminimum phase zeros and/or unstable poles, and (ii) two modifications can facilitate the loop shaping step. In particular, a nonminimum phase problem may be converted to one of frequency shaping a minimum phase loop; and a prestabilization scheme may be used for unstable systems. Two examples illustrate the proposed modifications with one compared to results obtained by the so called Set-Theoretic (ST) approach.

This paper presents an approach for optimal digital feed-forward tracking controller design. The tracking problem is formulated as a model matching problem, in which the distance between a specified tracking reference model and the achievable tracking performance by feedforward compensation is minimized. Desired input/output characteristics, finite length preview action, tracking of specific classes of constrained signals, time domain reference signal velocity or acceleration bound, and frequency domain weighting are conveniently incorporated in the proposed controller design and their roles in tracking performance are discussed. The tracking error bound is also explicitly expressed in terms of the controller design parameters. An [l.sub.1] norm optimal tracking controller is proposed as a solution to the mechanical tolerance control problem. A motion control example illustrates the design approach and several aspects of the resulting optimal feedforward controller, including the optimality of the zero phase error tracking controller.

This paper addresses the analysis and design of digital motion control system with machine vision as a feedback measurement in the servo loop. The camera vision is modeled as a discrete time-delayed sensor. A multirate formulation is proposed based on the fact that vision update rate is slower than the digital servo-control update rate and is analyzed through the lifting technique which converts the periodic time varying multirate system to a time invariant one. Some interesting properties of this specific multirate system are found and are utilized in control system design. An l-1 norm optimal control problem is formulated to minimize the maximum time domain error, which has direct connection to camera field of view and mechanical tolerance. A numerical example is given to demonstrate the presented methods.

This paper presents the development of robust digital tracking control algorithms and their real-time implementation on an electrohydraulic servo-actuator for tool positioning in noncircular machining. Robust adaptive feedforward controller for tracking arbitrary signals and robust repetitive controller for tracking periodic signals against disturbances and unmodeled dynamics have been developed. Experimental results are presented to illustrate the control system synthesis procedures and tracking performance.

The fine positioning problem of the gripper of flexible robotic manipulators is addressed in this study. A two-axis cartesian micro-manipulator is implemented to reduce the sensitivity of the gripper to the structural deformations of a single flexible link. A laser head with a dual axis photodetector are used to provide direct measurements of the transverse deflections at the free-end of the beam and to detect mechanical inaccuracies caused by manufacturing imperfections and assembly misalignment. The advantages of the integrated system of the micro-manipulator with a single compliant beam are demonstrated and compared to the one without the micro-manipulator for two different control schemes, 'rigid body controller (RBC)' and 'rigid and flexible motion controller (RFMC).' Both theoretical and experimental results have proven the capability of the micro-manipulator in significantly improving the gripper positional accuracy. Furthermore, it was demonstrated that the micro-manipulator tends to complement rather than overlap the efforts exerted by the host beam controller.

New digital control algorithms have been developed to achieve the desired transmissibility function for a microgravity isolation system. Two approaches have been presented for the controller design in the context of a single degree of freedom system for which an attractive electromagnet is used as the actuator. The relative displacement and the absolute acceleration of the mass have been used as feedback signals. The results from numerical studies are presented. It has been found that the resulting transmissibility is quite close to the desired function. Also, the maximum coil currents required by new algorithms are smaller than the maximum current demanded by the previously proposed lead/lag method.