Bumpless Transfer

S F Graebe and A Ahlén

In WS Levine , ed: CRC Control Handbook , CRC Press, 1996.
Also: Internal Report UPTEC 96070R, Dept. of Technology, Uppsala University.

Summary:

This chapter discusses the problem of bumpless transfer, which is concerned with smooth switching between alternative dynamical systems. A number of situations are highlighted in which this problem arises, including switching from manual to automatic control, on-line re-tuning of filter or controller parameters and tentative evaluation of new controllers during normal plant operation.

If it is possible to manipulate the states of the controller directly, there are several techniques to compute the value of the state vector that will give the desired output. If it is not possible to manipulate the states directly, such as in an analogue controller, then the input to the controller can be used instead. Viewed in this way, bumpless transfer becomes a tracking problem, in which the inputs to the controller are manipulated so that its output will track an alternative control signal. Once bumpless transfer is recognised as a tracking problem, systematic design techniques can be applied to design appropriate tracking controllers.Advantages with this approach are outlined and its relation to some other known techniques is discussed.

Related publications:

Paper in IEEE Trans. CST 1996 on the above theme.
Report on a systematic technique for scalar anti-windup design.
Conference paper (Reglermöte 96) on multivariable antiwindup design.