116 research outputs found
Identification and Adaptive Control for High-performance AC Drive Systems.
High-performance AC machinery and drive systems can be found in a variety of applications ranging from motion control to vehicle propulsion. However, machine parameters can vary significantly with electrical frequency, flux levels, and temperature, degrading the performance of the drive system. While adaptive control techniques can be used to estimate machine parameters online, it is sometimes desirable to estimate certain parameters offline. Additionally, parameter identification and control are typically conflicting objectives with identification requiring plant inputs which are rich in harmonics, and control objectives often consisting of regulation to a constant set-point. In this dissertation, we present research which seeks to address these issues for high-performance AC machinery and drive systems.
The first part of this dissertation concerns the offline identification of induction machine parameters. Specifically, we have developed a new technique for induction machine parameter identification which can easily be implemented using a voltage-source inverter. The proposed technique is based on fitting steady-state experimental data to the circular stator current locus in the stator flux linkage reference-frame for varying steady-state slip frequencies, and provides accurate estimates of the magnetic parameters, as well as the rotor resistance and core loss conductance. Experimental results for a 43 kW induction machine are provided which demonstrate the utility of the proposed technique by characterizing the machine over a wide range of flux levels, including magnetic saturation.
The remainder of this dissertation concerns the development of generalizable design methodologies for Simultaneous Identification and Control (SIC) of overactuated systems via case studies with Permanent Magnet Synchronous Machines (PMSMs). Specifically, we present different approaches to the design of adaptive controllers for PMSMs which exploit overactuation to achieve identification and control objectives simultaneously. The first approach utilizes a disturbance decoupling control law to prevent the excitation input from perturbing the regulated output. The second approach uses a Lyapunov-based adaptive controller to constrain the states to the output error-zeroing manifold on which they are varied to provide excitation for parameter identification. Finally, a receding-horizon control allocation approach is presented which includes a metric for generating persistently exciting reference trajectories.PhDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120862/1/davereed_1.pd
Degraded planetary tracking control of an omni-directional vectored-thruster aerostat
The problem of horizontal-plane tracking control of an omni-directional, four vectored-thruster aerostat when subjected to actuator failure is considered. The actuator failures result in the aerostat becoming underactuated, so it can only effect surge force and pure yaw moment about the body centre. To achieve accurate position control in the horizontal plane, direct position control is used instead of heading control. This mode of controller is called degraded tracking control in contrast to full authority control of the overactuated four vectored-thruster aerostat. This degraded tracking controller uses commanded yaw rate to track lateral position, and yaw moment to eliminate lateral position error, therefore yaw angle is not directly controlled. To guarantee the stability of the yaw motion, a Virtual Reference Point (VRP) tracking strategy is proposed, where the VRP is used instead of the body center (BC) in position tracking. The VRP generates a negative compensated force in the surge direction which makes the side-force and yaw moment have the same sign and so ensure that the aerostat is in a stable tracking configuration. Meanwhile the VRP also decreases the transmission ratio of commanded yaw rate to commanded lateral velocity, making the aerostat's yaw motion vary slowly during transitional phase, so steady position tracking is obtained
Control of an over-actuated nanopositioning system by means of control allocation
This Master’s Thesis is devoted to the analysis and design of a control structure for
the nanopositioning system LAU based on the dynamic control allocation technique.
The objective is to control the vertical displacement with nanometer precision under a
control effort distribution criterion among the actuator set. In this case, the pneumatic
actuator is used as a passive gravity compensator while the voice coil motor generates
the transient forces. The analysis of the system characteristics allows defining the
design criterion for the control allocation. In this direction, the proposed dynamic
control allocation stage considers a frequency distribution of the control effort. The
lower frequency components are assigned to the pneumatic actuator while the higher
frequencies are handled by the voice coil drive. The significant actuator dynamics are
compensated through a Kalman filter approach. The position controller is based on a
feedback linearization framework with a disturbance observer for enhanced robustness.
The experimental validation demonstrates the feasibility of the proposed technique.Diese Masterarbeit widmet sich der Analyse und dem Entwurf einer Regelungsstruktur
fĂĽr das Nanopositioniersystem LAU. Dabei werden Methoden untersucht, welche das
notwendige Stellsignal auf zwei Aktoren aufteilen. Ziel ist es, die vertikale Verschiebung
des LAU mit Nanometerpräzision zu regeln. In diesem Fall wird der pneumatische
Aktor als passiver Schwerkraftkompensator verwendet, während die elktromagnetische
Tauchspule die transienten Kräfte erzeugt. Die Analyse der Eigenschaften des LAUSystems
ermöglicht die Definition der Entwurfskriterien zur Aufteilung der Stellgröße. In
dieser Richtung berĂĽcksichtigt die vorgeschlagene dynamische Methode eine Aufteilung
der Stellgröße bezüglich der Frequenzanteile. Die niederfrequenten Komponenten
werden dem pneumatischen Aktor zugeordnet. Dem elektromagnetische Aktor werden
die verbliebenen hochfrequenten Anteile zugeordnet. Die signifikanten Effekte der
Aktordynamik in Bezug auf die Bewegungsdynamik werden durch einen Kalman-
Filteransatz kompensiert. Nichtlineare Streckenanteile werden basierend auf dem
Modell und einem Störbeobachter kompensiert, sodass der verbleibende Anteil des
Positionsreglers mit linearen Methoden entworfen werden kann. Die experimentelle
Validierung zeigt die Effektivität des untersuchten Konzeptes.Tesi
Advanced Feedback Linearization Control for Tiltrotor UAVs: Gait Plan, Controller Design, and Stability Analysis
Three challenges, however, can hinder the application of Feedback
Linearization: over-intensive control signals, singular decoupling matrix, and
saturation. Activating any of these three issues can challenge the stability
proof. To solve these three challenges, first, this research proposed the drone
gait plan. The gait plan was initially used to figure out the control problems
in quadruped (four-legged) robots; applying this approach, accompanied by
Feedback Linearization, the quality of the control signals was enhanced. Then,
we proposed the concept of unacceptable attitude curves, which are not allowed
for the tiltrotor to travel to. The Two Color Map Theorem was subsequently
established to enlarge the supported attitude for the tiltrotor. These theories
were employed in the tiltrotor tracking problem with different references.
Notable improvements in the control signals were witnessed in the tiltrotor
simulator. Finally, we explored the control theory, the stability proof of the
novel mobile robot (tilt vehicle) stabilized by Feedback Linearization with
saturation. Instead of adopting the tiltrotor model, which is over-complicated,
we designed a conceptual mobile robot (tilt-car) to analyze the stability
proof. The stability proof (stable in the sense of Lyapunov) was found for a
mobile robot (tilt vehicle) controlled by Feedback Linearization with
saturation for the first time. The success tracking result with the promising
control signals in the tiltrotor simulator demonstrates the advances of our
control method. Also, the Lyapunov candidate and the tracking result in the
mobile robot (tilt-car) simulator confirm our deductions of the stability
proof. These results reveal that these three challenges in Feedback
Linearization are solved, to some extents.Comment: Doctoral Thesis at The University of Toky
An Omnidirectional Aerial Platform for Multi-Robot Manipulation
The objectives of this work were the modeling, control and prototyping of a new fully-actuated
aerial platform. Commonly, the multirotor aerial platforms are under-actuated vehicles, since the
total propellers thrust can not be directed in every direction without inferring a vehicle body rotation.
The most common fully-actuated aerial platforms have tilted or tilting rotors that amplify
the aerodynamic perturbations between the propellers, reducing the efficiency and the provided
thrust. In order to overcome this limitation a novel platform, the ODQuad (OmniDirectional
Quadrotor), has been proposed, which is composed by three main parts, the platform, the mobile
and rotor frames, that are linked by means of two rotational joints, namely the roll and pitch
joints. The ODQuad is able to orient the total thrust by moving only the propellers frame by
means of the roll and pitch joints.
Kinematic and dynamic models of the proposed multirotor have been derived using the Euler-
Lagrange approach and a model-based controller has been designed. The latter is based on two
control loops: an outer loop for vehicle position control and an inner one for vehicle orientation
and roll-pitch joint control. The effectiveness of the controller has been tested by means of numerical
simulations in the MATLAB
c SimMechanics environment. In particular, tests in free motion
and in object transportation tasks have been carried out. In the transportation task simulation, a
momentum based observer is used to estimate the wrenches exchanged between the vehicle and
the transported object.
The ODQuad concept has been tested also in cooperative manipulation tasks. To this aim, a
simulation model was considered, in which multiple ODQuads perform the manipulation of a
bulky object with unknown inertial parameters which are identified in the first phase of the simulation.
In order to reduce the mechanical stresses due to the manipulation and enhance the system
robustness to the environment interactions, two admittance filters have been implemented: an external
filter on the object motion and an internal one local for each multirotor.
Finally, the prototyping process has been illustrated step by step. In particular, three CAD
models have been designed. The ODQuad.01 has been used in the simulations and in a preliminary
static analysis that investigated the torque values for a rough sizing of the roll-pitch joint
actuators. Since in the ODQuad.01 the components specifications and the related manufacturing
techniques have not been taken into account, a successive model, the ODQuad.02, has been designed.
The ODQuad.02 design can be developed with aluminum or carbon fiber profiles and 3D
printed parts, but each component must be custom manufactured. Finally, in order to shorten the
prototype development time, the ODQuad.03 has been created, which includes some components
of the off-the-shelf quadrotor Holybro X500 into a novel custom-built mechanical frame
Integral sliding mode fault tolerant control allocation for a class of affine nonlinear system
This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.This paper develops novel fault tolerant integral sliding mode control allocation schemes for a class of
over-actuated affine nonlinear system. The proposed schemes rely on an existing baseline controller and the
objective is to retain the nominal (fault-free) closed-loop performance in the face of actuator faults/failures
by effectively utilizing actuator redundancy. The online control allocation reroutes the control effort to the
healthy actuators using knowledge of the actuator effectiveness level estimates. One of the proposed schemes
is tested in simulation using a well known high fidelity model of a large civil transport aircraft (B747) from
the literature. Good simulation results show the efficacy of the scheme
Survey on Aerial Multirotor Design: a Taxonomy Based on Input Allocation
This paper reviews the impact of multirotor aerial vehicles designs on their abilities in terms of tasks and system properties. We propose a general taxonomy to characterize and describe multirotor aerial vehicles and their design, which we apply exhaustively on the vast literature available. Thanks to the systematic characterization of the designs we exhibit groups of designs having the same abilities in terms of achievable tasks and system properties. In particular, we organize the literature review based on the number of atomic actuation units and we discuss global properties arising from their choice and spatial distribution in the designs. Finally, we provide a discussion on the common traits of the designs found in the literature and the main future open problems
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