2 research outputs found
Linear matrix inequality based synthesis of PI controllers for PMSM with uncertain parameters
This paper addresses the design of robust PI controllers for permanent magnet synchronous motors in terms of a linear matrix inequality based problem. A polytopic model of the plant is obtained and validated for the motor uncertain parameters belonging to intervals. The design procedure proposed here encompasses: i. suitable plant uncertainties inclusion and the use of practical design control constraints; ii. robust PI computation based on linear matrix inequalities with a very fast solution; iii. simulation analyses; and iv. experimental evaluations. The robust PI controller can produce superior speed regulation than a PI controller designed only for the nominal parameters, including better disturbance rejection and H-infinity performance. Experimental results confirm the viability of the proposal, which can be seen as an efficient alternative to trade off performance and robustness for PI controllers in this application233310319CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES306197/2015-4não te
RECENT TECHNIQUES ON OBSERVER DESIGN FOR DISTURBANCE ESTIMATION AND REJECTION IN PERMANENT MAGNET SYNCHRONOUS MOTORS
Permanent magnet synchronous machines (PMSMs) (either motor or generator) have
attracted attention of research community comparing to other types of AC machines
in the recent two decades. PMSMs are preferable than other AC machines in terms
of large power-factor, broad speed of operation, compact proportions, and effective
operation. Unfortunately, different sources of nonlinearities, model uncertainties,
and external perturbations determine severity in a design of accurate speed control
scheme for PMSMs. In the era of developing science and technologies, many advanced
control solutions are proposed to control PMSMs. Although new solutions show
their advantages comparing to traditional methods in terms of performance evaluation,
practical realization of those algorithms could require expensive hardware with high
computational capabilities. Furthermore, people in industry with less knowledge about
the motor control may experience difficulties in using such advanced controllers on
their own.
Traditional PI/PID control schemes still work as a major control technique in modern
industry, and in motor control as well. Numerous positive facts about the PI/PID
schemes make such superiority of these control schemes. Firstly, the PI/PID can be
implemented easily on most industrial software and hardware components. Secondly,
while its scheme has clear mechanism of operation, most industrial processes could be
controlled via the PI/PID scheme. These schemes are good in terms of small number
of parameters to tune and tuning process itself could be very straightforward. Finally,
implementation of the PI/PID controllers would require smaller time comparing to most
proposed complex control solutions.
It is studied that the traditional PI/PID controllers usually cannot deal with
unpredictable disturbances, which in turn leads to degraded performance of an overall
control system. Inspired by the advantages and widespread application of PI/PID
control structure in industry, we propose a disturbance observer based composite
control scheme which uses the PI-like controller for the feedback regulation and
disturbance observer for estimation of lumped disturbances presented in a PMSM
control system. Under this circumstance, this thesis work proposes three different
control solutions for PMSM such as High-order disturbance observer-based composite
control (HDOBCC), Disturbance rejection PI (DR-PI) control, and Hierarchical optimal
disturbance observer-based control (HODOBC). Furthermore, to deeply understand the
similarity and difference between the traditional disturbance observer-based control (DOBC) and active-disturbance rejection control (ADRC) schemes, this thesis also
presents results of unification of these two control approaches in the speed control of a
PMSM.
The HDOBCC as the first method proposed in this thesis is designed to improve
reference speed tracking performance of a PMSM under various operational conditions.
A structure of the HDOBCC comprises a fuzzy-PI controller in a feedback stabilization
part and novel high-order disturbance observer in a feedforward compensation part of
the speed control system. The proposed controller is designed based on the research
questions such as: firstly, although a fixed gain traditional PI controller is able to present
satisfactory performance at some extent, still it does not guarantee such performance
when sudden disturbances occur in a system; secondly, many disturbance observers
designed for a PMSM in literature consider only a load torque as a disturbance,
neglecting model uncertainties and parameter variations in design stage. Therefore, the
HDOBCC is proposed such that it utilizes a fuzzy approach to determine parameters of
the PI controller to overcome limitations of the fixed gain PI controller. Furthermore,
the proposed scheme includes a high-order disturbance observer, which estimates not
only the load torque, but also disturbances due to model uncertainties and parameter
variations. Moreover, extended simulation and experimental studies are conducted to
affirm performance of the HDOBCC under various form of the load torque. In addition
to commonly tested step form of a load torque, severe forms of the load torque such as
triangular form and sinusoidal form are tested with the proposed controller. Stability
analysis of the closed-loop HDOBCC system is further provided.
The next proposed method, DR-PI control, is designed by seeking answer for
questions such as: firstly, although the traditional DOBC scheme applied for PMSM
shows reasonable results in a PMSM control, its design can be limited to known actual
parameters of the PMSM. In practice, actual parameters are usually not available, hence
it could be hard to design the traditional DOBC in the absence of a plant information;
secondly, for tuning a PI controller the traditional Ziegler-Nichols tuning approach still
remains as one of the popular tuning approaches, however it does not give a rigorous
explanation on selection of parameters during its design. Consequently, to answer these
questions, the DR-PI control is designed for the PMSM speed control. The DR-PI
control is designed such that it has a simple PI-like structure with intrinsic disturbance
rejection mechanism determined by the parameters of a filtering element, desired plant
model, and desired closed-loop system. Simulation and experimental validations are
provided to validate the performance of the DR-PI. Furthermore, gain tuning mechanism
and stability analysis of the closed-loop DR-PI-based speed control are also presented.
The HODOBC scheme as a third proposed control scheme targets on the next
research questions as: first, parameters of the traditional PI controller are mostly
obtained by trial-and-error approach, which in turn may not guarantee satisfactory results; in a cascaded PMSM control, the outer speed loop performance highly depends
on the performance of the inner current loop. The well-tuned speed control loop may
degrade in performance, if the inner current loop is not tuned properly. To address
these questions, we propose the HODOBC scheme, which consists of optimal PIlike
controller in the feedback stabilization part and optimal extended-state observer
(ESO) in the disturbance compensation part. The proposed HODOBC showed better
performance when it is compared with other traditional controllers via experiments.
Stability analysis is provided via the root locus approach.
The study on unification of the DOBC and ADRC schemes has the following research
question: the DOBC and ADRC are both used in estimation of total disturbance, but
these two schemes are considered differently in literature. Hence, the study of both
scheme is conducted to show the condition at which these two schemes show identical
performance. The analysis of the traditional DOBC and ADRC schemes concludes that
both scheme are equivalent in terms of performance characteristics if the dynamical
delays of disturbance observers in each scheme are same. The results of analysis reveal
that both scheme can be utilized to design a robust control system for PMSM, i.e.
once the gains of disturbance observers can be calculated under the DOBC framework,
further the disturbance rejection mechanism can be achieved via the ADRC framework.
The results of PMSM control with the proposed control schemes have been tested on
the Lucas-Nuelle DSP-based experimental setup