I. INTRODUCTION
The PID control is considered one of the most common
control schemes and it has been applied to many industrial
processes and mechanical systems. Since the control plays a
very important role in the improvement of production quality,
accuracy and in reducing production costs, auto-tuning PIDs
including self-tuning scheme and adaptive control strategies
have been attracted a great deal of interest and several
kinds of auto-tuning PIDs including self-tuning scheme and
adaptive control strategies have been proposed. Recently, an
adaptive PID control strategies based on the almost strictly
positive real (ASPR) property of the controlled system have
been proposed [1], [2]. The adaptive PID control scheme
based on the ASPR property of the system is expected as a
prospective adaptive method for PID control, since it can
easily guarantee the asymptotic stability of the resulting
Adaptive PID control system, and the practicability and
robustness of these ASPR based adaptive PID methods have
been confirmed through several numerical simulations and
practical experiments.
On the other hand, it has been well known that there is an
input restriction in many practical systems and this restriction
deteriorates the control performance significantly as seen in
windup phenomena[3], [4]. This windup phenomenon can
be seen in the above mentioned ASPR based adaptive PID
control system too.
In this paper, we consider applying the ASPR based
adaptive PID scheme to a magnetic levitation system with
input saturation. A strategy which alleviates the windup
phenomena on the ASPR based adaptive PID control system
will be proposed. As is well known, in order to realize
the ASPR based adaptive control for non-ASPR controlled
systems, the introduction of a parallel feedforward compensator(PFC)
has been considered as one of the most common
and useful method. Unlike the common anti-windup control
strategies[5], we will provide a novel time varying PFC
I. INTRODUCTIONThe PID control is considered one of the most commoncontrol schemes and it has been applied to many industrialprocesses and mechanical systems. Since the control plays avery important role in the improvement of production quality,accuracy and in reducing production costs, auto-tuning PIDsincluding self-tuning scheme and adaptive control strategieshave been attracted a great deal of interest and severalkinds of auto-tuning PIDs including self-tuning scheme andadaptive control strategies have been proposed. Recently, anadaptive PID control strategies based on the almost strictlypositive real (ASPR) property of the controlled system havebeen proposed [1], [2]. The adaptive PID control schemebased on the ASPR property of the system is expected as aprospective adaptive method for PID control, since it caneasily guarantee the asymptotic stability of the resultingAdaptive PID control system, and the practicability androbustness of these ASPR based adaptive PID methods havebeen confirmed through several numerical simulations andpractical experiments.On the other hand, it has been well known that there is aninput restriction in many practical systems and this restrictiondeteriorates the control performance significantly as seen inwindup phenomena[3], [4]. This windup phenomenon canbe seen in the above mentioned ASPR based adaptive PIDcontrol system too.In this paper, we consider applying the ASPR basedadaptive PID scheme to a magnetic levitation system withinput saturation. A strategy which alleviates the windupphenomena on the ASPR based adaptive PID control systemwill be proposed. As is well known, in order to realizethe ASPR based adaptive control for non-ASPR controlledsystems, the introduction of a parallel feedforward compensator(PFC)has been considered as one of the most commonand useful method. Unlike the common anti-windup controlstrategies[5], we will provide a novel time varying PFC
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