Abstract
This paper proposes an anti-windup like scheme for an LTI plant with rate-limits. The plant is controlled using a model-reference adaptive controller, making the anti-windup design problem highly nonlinear. It is assumed that the rate-limit is modelled as a first order feedback loop for which the state is unavailable, but that the bandwidth of this loop is known. The anti-windup scheme uses a “hedging” term and a “positive μ” term. The structure of the problem makes the rate-limit case considerably more difficult than the magnitude limit case. Nevertheless it is proved that convergence of the system state to the ideal model can be accomplished under conditions similar to those found in anti-windup compensation for purely linear systems.
Highlights
The idea behind anti-windup is to introduce an extra element into the control system which monitors the control signal and, if it experiences saturation, modifies the control system so that it behaves better during and after these periods of saturation
In model reference adaptive control (MRAC), it is typically assumed that only the structure of the plant is known, with many of its parameters unknown
The choice of Γx, Γu and Q was based on some initial simulation and was straightforward; it seemed to enable swift adaptation but without too much control activity; other choices are possible. This adaptive controller works well in the absence of saturation, but the system is very sensitive to saturation [16]
Summary
An ever-present nonlinearity, are often a thorn in the side of control engineers, sometimes causing well-behaved systems to exhibit unexpectedly poor behaviour. In model reference adaptive control (MRAC), it is typically assumed that only the structure of the plant is known, with many of its parameters unknown For this reason the anti-windup schemes described above are not appropriate, without significant alteration. Unlike most of the approaches for handling saturation in adaptive controllers mentioned above, the so-called positive-μ scheme described in [14] (see [24]), functions somewhat differently and, when expressed appropriately, one can observe an anti-windup structure in the algorithm [21]. This anti-windup scheme features a classical anti-windup element (the μ parameter) which feeds back the difference between the control signal and its saturated version to the controller output. This paper considers SISO systems, an extension to MIMO systems could be performed using similar ideas
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
