Frequency response based multivariable control design for motion systems

In this paper, we discuss the design of multivariablemotion controllers exploiting crosscouplings in the controller for open loop decoupling, disturbance rejection and feedforward decoupling. Using specific properties of motion systems, we illustrate that frequency response design methods can be extendedto handle several multivariable control problems. Application to high performance motion systems shows significant improvement

Multivariable control design for fixed direction disturbances

In this paper, a blind identification method is employedto model multivariable disturbances with fixed direction.The multivariable disturbance model is used to design nondiagonalweighting filters for Hinf control. It is demonstratedthat in this way, intuitive shaping of the directions of closed loop transfer functions is facilitated, maximally exploiting design freedom that has no analogue for scalar systems

MIMO jerk derivative feedforward for motion systems

This paper shows that flexible modes in motion systems result in residual dynamics that can not be reduced using conventional acceleration feedforward and static decoupling. When reference trajectories with low frequency excitation are applied, low frequency tracking errors and cross-talk errors occur as peaks during jerk phases of a motion. A multivariable jerk derivative feedforward controller is presented which compensates for the joint contribution of all flexible modes in the low frequency region. Furthermore it is shown that no higher order (than 4) feedforward controller is required to improve low frequency tracking performance. A simulation example of a positioning device shows a significant improvement of the tracking performance

Rejection of disturbances in multivariable motion systems

Due to ever increasing demands in industry, the number of applications of multiple input multiple output (MIMO) control systems has increased drastically in the last decades. Although considerable progress has been made in the development of theoretical tools, feedback control design for MIMO systems still poses complexity issues for both academia and the practising engineer. In an effort to reduce design complexity, many aspects of MIMO systems are disregarded in most practical applications, at the cost of potential achievable performance. One of the important tasks of feedback control is the ability to reject disturbances. In MIMO systems, gain, phase, and directions play an important role in the systems ability to reject disturbances. The directional, multivariable, aspects of disturbances necessitate approaching the MIMO control problem in its full complexity. The goal of this work is to make directional aspects an integral part of MIMO control design. Herein, the focus is on applications of motion control systems. The contribution of this work is two-fold. The first contribution of this work is the development of techniques to characterize multivariable disturbances. A non-parametric component analysis method is developed to identify both the directional aspects of disturbances and the root cause (source) of disturbances in multivariable closed loop controlled systems. Indices are developed to quantify directionality of disturbances and, possibly, simplify multivariable control design. These techniques are applied to an active vibration isolation platform. It is shown how the location of sources can be recovered using only closed loop measurements. Furthermore, it is demonstrated how multivariable control design can be simplified. With this, it is demonstrated how multivariable aspects of disturbances can be interpreted physically and exploited in control design. The second contribution of the work involves the development of control design methods that take advantage from the multivariable aspects of disturbances. The focus is on systems where the plant dynamics are decoupled while disturbances may act on may decoupled parts of the plant at the same time. Methods are developed to design non-diagonal weighting filters for H1 control synthesis. Furthermore, manual frequency domain loopshaping techniques are developed for the design of centralized MIMO controllers that accommodate directions of disturbances and sensor noise. It is illustrated with several examples that, using these developed techniques, directions of disturbances and noise can be successfully integrated in control design for multivariable motion systems

Jerk derivative feedforward control for motion systems

This work discusses reference trajectory relevant model based feedforward design. For motion systems which contain at least one rigid body mode and which are subject to reference trajectories with mostly low frequency energy, the proposed feedforward controller improves tracking performance significantly. The feedforward controller may be of much lower order than the plant. The proposed feedforward controller is introduced using a model of an industrial XY-table as an application exampl

Jerk derivative feedforward control for motion systems

This work discusses reference trajectory relevant model based feedforward design. For motion systems which contain at least one rigid body mode and which are subject to reference trajectories with mostly low frequency energy, the proposed feedforward controller improves tracking performance significantly. The feedforward controller may be of much lower order than the plant. The proposed feedforward controller is introduced using a model of an industrial XY-table as an application exampl

Blind identification of multivariable disturbances

Abstract onl

Rejection of fixed direction disturbances in multivariable electromechanical motion systems

This work discusses rejection of disturbances with known directions in multivariable motion systems. It is shown how frequency domain tradeoffs in multivariable control motivate a design where the directions of disturbance are considered explicitly. A design method is presented to design multivariable centralized controllers to reject disturbances only in relevant directions. A model of an industrial motion system is used to demonstrate this method. It is shown how the proposed design method resembles the solution of a competing H8 design and offers the ability to interpret H8 centralized control solutions understanding the inherent tradeoffs of multivariable feedback control. Crown Copyright © 2009