544 research outputs found
Identification of MIMO LPV models based on interpolation
No full textThis paper presents SMILE (State-space Model Interpolation of Local Estimates), a new technique to estimate linear parameter varying state-space models for multiple-input multiple-output systems whose dynamics depends on a single varying parameter, called the scheduling parameter. The SMILE technique is based on the interpolation of linear time-invariant models that are valid for fixed operating conditions of the system, that is, for constant values of the scheduling parameters. The methodology yields affine LPV models that are numerically well-conditioned and therefore suitable for LPV control synthesis procedures. The underlying interpolation technique is formulated as a nonlinear least-squares optimization problem that can be efficiently solved by standard solvers. Application of the proposed methodology to a vibroacoustic setup, whose dynamics are highly sensitive to the ambient temperature, clearly demonstrates the potential of the SMILE technique. © 2008 by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved.sponsorship: The author J. F. Camino is supported through grants from CAPES, CNPq and FAPESP. The authors J. De Caigny and J. Swevers are supported through the following funding: project G.0446.06 of the Research Foundation Flanders (FWO Vlaanderen), K.U.Leuven BOF EF/05/006 Center-of-Excellence Optimization in Engineering and the Belgian Programme on Interuniversity Attraction Poles, initiated by the Belgian Federal Science Policy Office. The scientific responsibility rests with its author(s). (CAPES, CNPq, FAPESP, Research Foundation Flanders (FWO Vlaanderen)|G.0446.06, K.U.Leuven|BOF EF/05/006, Center-of-Excellence Optimization in Engineering, Belgian Programme on Interuniversity Attraction Poles, Belgian Federal Science Policy Office)status: Publishe
Experimental robot identification: Advantages of combining internal and external measurements and of using periodic excitation
No full textThis paper discusses the advantages of using periodic exitation and of combining internal and external measurements in experimental robot identification. This discussion is based on the robot identification method developed by Swevers et al.. a method that is effective means of robot identification that is frequently used, recognized by, industry as an Hirzinger, G., Fischer M., Brunner A, Koeppe. R., Otten M.. Grebenstein, M., and Schafer I, 1999, "Advances is Robotics: The DLR Experiment," The International Journal of Robotics Research, Vol. 18, No. II, pp. 1064-1087 [3]. Experimental results on a KUKA IR 361 show that the periodicity of the robot excitation is a key element of this method. Nonperiodic robot excitation complicates the signal processing preceding the parameter estimation, often yielding less accurate parameter estimates. An extension of this identification method Combines internal and external measurements, chenut, X., Samin, J. C, Swevers, J.. and Ganseman, C., 2000, "Combining Internal and External robot Models,for improved Model parameter Estimation, " Mechanical systems and Signal processing. Vol. 14. No. 5. pp. 691-704 [4]. yielding robot models that allow, to accurately predict the actuator torques and the of the robot on its base plate. which are both important for the path planning. This paper presents and critically discusses the first experimental results obtained with this method
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No full textIn this paper, we discuss a new experimental robot load identification method that is used in industry. The method is based on periodic robot excitation and the maximum likelihood estimation of the parameters, techniques adopted from Swevers et al. (1997 IEEE Transactions on Robotics and Automation 13(5):730–740). This method provides: (1) accurate estimates of the robot load inertial parameters; and (2) accurate actuator torque predictions. These are both essential for the acceptance of the results in an industrial environment. The key element to the success of this method is the comprehensiveness of the applied model, which includes, besides the dynamics resulting from the robot load and motor inertia, the coupling between the actuator torques, the mechanical losses in the motors and the efficiency of the transmissions. Accurate estimates of the robot link and motor inertial parameters, which can be considered identical for all robots o
Motion stabilization in the presence of friction and backlash: a hybrid system approach
No full textIn this paper a hybrid system approach is considered to deal with backlash and
friction induced nonlinearities in mechanical control systems. To describe the low velocity
frictional behaviour a linearized friction model is proposed. The novelty of this study is that
based on the introduced friction model, the stability theorems developed for hybrid systems can
directly be applied for controller design of mechanical systems in the presence of Stribeck friction
and backlash. During the controller design it is assumed that the size of the backlash gap is
unknown and the load side position and velocity cannot be measured. For motion control an LQ
controller is applied. A condition is formulated for the control law parameters to guarantee the
asymptotic stability of the control system. Simulation measurements were performed to confirm
the theoretical results
Gain-scheduled Hoo-control of discrete-time polytopic time-varying systems
No full textThis paper presents synthesis procedures for the design of both robust and gain-scheduled H∞ static output feedback controllers for discrete-time linear systems with timevarying parameters. The parameters are assumed to vary inside a polytope and have known bounds on their rate of variation. The geometric properties of the polytopic domain are exploited to derive a finite set of linear matrix inequalities that consider the bounds on the rate of variation of the parameters. A numerical example illustrates the proposed approach. © 2008 IEEE.sponsorship: The authors J. F. Camino, R. C. L. F. Oliveira and P. L.D. Peres are supported through grants from CAPES, CNPq and FAPESP. The authors J. De Caigny and J. Swevers are supported through the following funding: project G.0446.06 of the Research Foundation Flanders (FWO Vlaanderen), K.U.Leuven BOF EF/05/006 Center-of-Excellence Optimization in Engineering and the Belgian Programme on Interuniversity Attraction Poles, initiated by the Belgian Federal Science Policy Office. The scientific responsibility rests with its author(s). (CAPES, CNPq, FAPESP, Research Foundation Flanders (FWO Vlaanderen)|G.0446.06, Center-of-Excellence Optimization in Engineering|EF/05/006, Belgian Programme on Interuniversity Attraction Poles, initiated by the Belgian Federal Science Policy Office)status: Publishe
Gemengde-Geheeltallige Optimalisatie en Model-Gebaseerd Voorspellend Regelschema Toegepast op Hybride Voertuigen
No full textIn my PhD dissertation, three different algorithms will be presented and evaluated with the help of a series of numerical experiments.
The first algorithm takes the name of Proximal Outer Approximation (POA). POA results from the merging and harmonization of the characteristics of two different approaches to mixed-integer convex optimization: Outer Approximation (OA) and Feasibility Pump (FP). The algorithm seeks to find an adaptive balance between the more feasibility-focused FP-like iterations and the more optimality-focused OA-like iterations. The collected empirical evidence suggests that, on the analyzed benchmark, Proximal Outer Approximation is capable of yielding faster and more robust convergence with respect to the classical OA algorithm.
Next to be presented is the Mixed-Integer Real-Time Optimal Control (MIRT-OC) algorithm, a mixed-integer convex Model Predictive Control (MPC) approach that, inspired from the success of single-tree optimization schemes for mixed-integer convex optimal control, reduces the whole MPC process to a single tree search. The algorithm, rather than dealing with each MPC iteration separately, makes use of two specialized routines in order to adapt the optimization data and the search-tree collected during one MPC iterationo into optimization data and a partially explored search-tree for the subsequent iteration. Such strategy allows for maximal reuse of the collected information and, as confirmed by the performed numerical experiments, provides sizeable computational savings.
Finally, the thesis presents the Disjunctive Outer Approximation for Optimal Control (DOA-OC) scheme, a specialized variation of Outer Approximation capable of efficiently solving a certain class of mixed-integer non-convex optimal control problems. The algorithm exploits the peculiar structure of the optimization problems that arise from optimal control applications and where the constraints result convex only on the continuous variables of the system. The distinctive feature of DOA-OC is its ability of efficiently generating linear relaxations for the non-convex constraints of the considered problems. The result is the possibility of avoiding the use of extremely expensive mixed-integer non-convex solution schemes or fiddly reformulations techniques, and thus, of obtaining vast reductions in computational complexity.status: Publishe
Time Optimal Control of Mechatronic Systems Through Embedded Optimization
No full textIn all levels of society, a lot of effort is put in the optimal use of resources as e.g.energy, labor and time. Resource optimization is also important in the control ofmechatronic systems. For these applications, typically either the required time orthe energy consumption to perform an action is minimized. This thesis developscontrollers which aim to minimize the time required to perform a point-to-pointmotion, i.e. the settling time of the system. These controllers are developedwithin the model predictive control framework (mpc). In this framework, thesystem input is determined by solving on-line, during every sampling period, anoptimization problem. This on-line optimization allows to take systems constraintslike actuator saturation, directly into account. The time-optimal controllers havebeen developed for mechatronic systems with sampling periods in the order ofmilliseconds. Hence, the fast solution of these problems is an important designparameter. The main contributions of this research are as follows. First, theminimization of settling time has been formulated as an optimization problemwithin the mpc framework. Then, the structure of these optimization problems hasbeen analyzed and exploited such that these problems can now be formulated withenough variables to be applicable for relevant mechatronic applications while stillbeing solvable within a few milliseconds. All developed time-optimal controllershave been validated experimentally on representative mechatronic systems as linearmotors and an overhead crane. This experimental validation shows that with thedeveloped controllers sampling periods of a few milliseconds are attainable and thatthe settling time can be reduced considerably in comparison with linear controllersand traditional mpc controllers.Within this global framework of minimizing settling time, three controllers havebeen designed. First, a time-optimal feedforward controller has been developed.This controllers generates a reference trajectory which minimizes the settling timefor point-to-point motions. This feedforward controller has been developed as amore performant alternative to linear prefilters. Then, a time-optimal feedbackcontroller has been developed. The introduction of feedback allows to rejectdisturbances and to remove steady state errors. Last, a control scheme whichcombines the time-optimal controllers with linear feedback controllers, has beenproposed. This scheme allows to fulfill the benchmark requirements of an industriallinear motor, i.e. not only a small settling time but also an absolute settlingaccuracy in the submicrometer range.status: Publishe
Resonante piëzo-elektrische motoren – Impact van mechanische productieafwijkingen en daaraan aangepaste ontwerpmethodes
No full textstatus: Publishe
Optimal Linear Controller Design for Periodic Inputs and Extended LMI Characterizations for Linear Stability and Performance
No full textPeriodische referentie- en storingssignalen komen veelvuldig voor in ing enieurstoepassingen, waarbij ze meestal veroorzaakt worden door een rote rend mechanisme of periodiek proces. In het regelaarontwerp is het uitbu iten van de eigenschappen van deze periodische signalen onmisbaar om te voldoen aan strenge vereisten voor storingsonderdrukking en trajectnavol ging in de aanwezigheid van meetruis, modelonzekerheden, ... Het eerste deel van deze thesis ontwikkelt een algemene ontwerpmethodolo gie voor lineaire regelaars in de aanwezigheid van periodische ingangssi gnalen. Deze methodologie is van toepassing op alle categorieën van rege laars die voorgesteld zijn in de literatuur, en kan hierbij de belangrij kste huidige ontwerpstrategieën reproduceren en verbeteren. Dit resultaa t is het gevolg van de volgende eigenschappen: (i) onzekerheid op de per iode wordt expliciet in rekening gebracht, (ii) verbeterde onderdrukking /navolging van het periodische ingangssignaal wordt afgewogen tegen conf licterende ontwerpvereisten, en (iii) het regelaarontwerp wordt vertaald naar een convex optimalisatieprobleem, hetgeen de efficiënte berekening van het globale optimum garandeert. Naast uitgebreide numerieke evaluat ie, wordt de praktische relevantie van de ontwerpmethodologie aangetoond door experimentele validatie op een actieve-luchtlageropstelling. Het onafhankelijke tweede deel van de thesis ontwikkelt een algemene met hodologie voor het afleiden van zogenoemde uitgebreide LMI-karakteriseri ngen voor de stabiliteit en prestatie van lineaire systemen. Deze uitgebreide LMIs laten toe om de conservativiteit te reduceren in moeili jke problemen uit de lineaire systeemtheorie en regeltechniek, zoals het regelaarontwerp met meerdere objectieven en de robuuste stabiliteit- en prestatie-analyse van systemen met onzekere parameters. Steunend op het projectie lemma, levert de voorgestelde methodologie een eenvoudig en e ensluitend bewijs voor het merendeel van de resultaten uit de literatuur , evenals voor nieuwe uitgebreide LMIs.status: Publishe
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