bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Stability of Closed-Loop Systems Resulting From Nonsequential MIMO-QFT Design
Authors: Zhao Yongdong , Jayasuriya Suhada
Published: February 2008

Considered in this paper is the question of whether a compensator realized by the MIMO-QFT nonsequential method robustly stabilizes the entire plant family. In order to establish our results, first the classic small gain theorem for robust stability is modified to allow uncertain plant families with poles arbitrarily crossing the imaginary axis, or equivalently, plants in which the number of unstable poles does not remain fixed over all uncertainties. The conventional assumption that the number of unstable poles remain fixed over all uncertainties can be quite restrictive, especially, in the case of plants with structured uncertainties. It is shown that to assure robust stability of the closed loop, resulting from the MIMO-QFT nonsequential approach, one more requirement must be added to the procedure. The needed extra condition can be quite naturally incorporated during the execution of the nonsequential technique. As a result, the proposed condition does not significantly alter the basic MIMO-QFT nonsequential procedure.
Smooth Robust Adaptive Sliding Mode Control of Manipulators With Guaranteed Transient Performance
Authors: Yao Bin , Tomizuka Masayoshi
Published: February 2008

A systematic way to combine adaptive control and sliding mode control (SMC) for trajectory tracking of robot manipulators in the presence of parametric uncertainties and uncertain nonlinearities is developed. Continuous sliding mode controllers without reaching transients and chattering problems are first developed by using a dynamic sliding mode. Transient performance is guaranteed and globally uniformly ultimately bounded (GUUB) stability is obtained. An adaptive scheme is also developed for comparison. With some modifications to the adaptation law, the control law is redesigned by combining the design methodologies of adaptive control and sliding mode control. The suggested controller preserves the advantages of both methods, namely, asymptotic stability of the adaptive system for parametric uncertainties and GUUB stability with guaranteed transient performance of sliding mode control for both parametric uncertainties and uncertain nonlinearities. The control law is continuous and the chattering problem of sliding mode control is avoided. A prior knowledge of bounds on parametric uncertainties and uncertain nonlinearities is assumed. Experimental results conducted on the UCB/NSK SCARA direct drive robot show that the combined method reduces the final tracking error to more than half of the smoothed SMC laws for a payload uncertainty of 6 kg, and validate the advantage of introducing parameter adaptation in the smoothed SMC laws.
LP-Neuro Method—A New Approach for Solving Neural Network Problems
Authors: Balasubramanian R. , Sharan A. M.
Published: February 2008

In this work, a new algorithm called LP-Neuro method is developed to solve artificial neural network problems. In this algorithm, the weights are obtained by a combination of linear programming having a sparse coefficient matrix and a single variable nonlinear optimization routine. The results are illustrated by solving three different problems, two of which are useful in the on-line control of robotic manipulators.
A Higher-Order Method for Dynamic Optimization of a Class of Linear Systems
Authors: Agrawal S. K. , Veeraklaew T.
Published: February 2008

This paper deals with optimization of a class of linear dynamic systems with n states and m control inputs, commanded to move between two fixed states in a prescribed final time. This problem is solved conventionally using Lagrange’s multipliers and it is well known that the optimal solution satisfies 2n first-order linear differential equations in the state and Lagrange multiplier variables. In this paper, a new procedure for dynamic optimization is presented that does not use Lagrange multipliers. In this new procedure applied to a class of linear systems with controllability index p = (n/m), optimal solution satisfies m differential equations of order 2p. The boundary conditions on these m variables are computed in terms of higher derivatives (up to p − 1) at the initial and final time. These higher-order differential equations are solved using classical weighted residual methods, methods relatively unknown to controls community but extremely popular with researchers in mechanics. This new procedure for dynamic optimization, higher order necessary condition solved by weighted residual method, is computationally more efficient compared to other conventional procedures, offering benefits for real-time applications.
Transient Response of Repetitive Control Systems
Authors: Garimella S. S. , Srinivasan K.
Published: February 2008

Upper bounds on transient response magnitudes for a SISO continuous-time repetitive control system are derived. Limiting the size of these transients is shown to be related to limiting the ∞-norm of a transfer function product of filters used in the repetitive controller. The decay rate of the transients is related to the peak of a function of frequency called the regeneration spectrum, which has previously been shown in the literature to be a measure of the relative stability of the system. Bounds derived here, although conservative, can be useful in the design of the repetitive controller, as illustrated by means of an example.
Stability of Hydraulic Motion Control Systems
Authors: Margolis D. L. , Hennings C.
Published: February 2008

High performance hydraulic motion control systems typically consist of a two-stage spool valve which controls flow into an actuator. Feedback of load motion allows an electrical signal into the valve to control large amounts of hydraulic power. These servo-systems are well known to exhibit an instability where they “sing” or “chirp” at high frequency. This instability seems to be configuration-dependent. Here, two submodels are proposed that expose a fluid flow induced instability, and a mechanical instability. The result is parameter groupings which expose these instabilities in a fundamental way.
Measurement and Signal Reconstruction of Transient Nitric Oxide Emissions in the Exhaust of a Turbocharged Diesel Engine
Authors: Chan S. H. , Chen X. S. , Arcoumanis C.
Published: February 2008

A well-developed technique, based upon a combined experimental and phenomenological modeling approach, has been adopted for the measurement of nitric oxide (NO) emissions in a diesel engine exhaust under transient engine operation. The dynamic behavior of the chemiluminescent analyzer used for the measurement of NO emissions is characterized by a single gas diffusion model followed by three perfect gas-mixing models. The response of the analyzer is obtained using a computer-controlled transient NO emission simulator, which randomly generates a square-pulse train of NO gas and concurrently measures its signal output. Signal prediction and reconstruction analysis were performed, which has demonstrated the predictive and reconstructive capabilities of the phenomenological analyzer model. On-line nitric oxide emission measurements were obtained in a computer-controlled dynamic engine test bed having three different control modes and fuel injection timing settings. The results have shown that the transient nitric oxide concentration is very sensitive to the engine operating condition prior to the transients as well to the amount of fuel injected into the combustion chamber at the start of the transient operation.
A Superconducting Maglev Vehicle/Guideway System With Preview Control: Part I—Vehicle, Guideway, and Magnet Modeling
Authors: Nagurka M. L. , Wang S. K.
Published: February 2008

Part I of this paper presents a dynamic model of magnetically-levitated (maglev) vehicle/guideway interaction. The vehicle employs a superconducting electromagnetic suspension system with canted magnets to provide simultaneous levitation and guidance in the face of guideway irregularities and cross-wind gusts. The dynamic simulation model includes a five degree-of-freedom nonlinear vehicle model, a superconducting magnet model, and a multi-span flexible guideway model. The formulation accounts for the dynamic loading on the guideway due to time-varying, distributed magnetic forces imposed by the vehicle. The maglev vehicle/guideway model is the basis for designing and testing a proposed preview control strategy in Part II of this paper.
A Superconducting Maglev Vehicle/Guideway System With Preview Control: Part II—Controller Design and System Behavior
Authors: Wang S. K. , Nagurka M. L.
Published: February 2008

Part II of this paper proposes the use of optimal preview control with integral action for a maglev vehicle with a superconducting electromagnetic suspension system operating on an elevated, flexible guide-way. The control system is designed based on a linearized model and then applied to a full-scale nonlinear simulation model of the maglev vehicle, magnet modules, and guideway (derived in Part I—Vehicle, Guideway, and Magnet Modeling). Simulation studies demonstrate the effectiveness of the controller and evaluate the vehicle performance under the influences of guideway flexibility, guideway irregularities, and aerodynamic disturbances.
Practical Design of a Sliding Mode Controller for Pneumatic Actuators
Authors: Pandian Shunmugham R. , Hayakawa Yasuhiro , Kanazawa Yoshinori , Kamoyama Yoshiyuki , Kawamura Sadao
Published: February 2008

Pneumatic robot manipulators are characterized by high-order, time-variant actuator dynamics, nonlinearities due to compressibility of air, external disturbances such as static and Coulomb friction, and wide range of payload variations. Conventional PID controllers suffer from problems of gain tuning under these conditions. In this paper, a new control algorithm is proposed for the position and trajectory control of pneumatic actuators based on the sliding mode control approach. The stability of motion is proved for the case of a linear, time-invariant switching surface. A disadvantage of using sliding mode control for third- and higher-order mechanical systems is the need for acceleration feedback. In this paper, to overcome this difficulty we propose the use of differential pressure. The proposed controller is simple, easy to implement, and robust to payload and parametric variations. The effectiveness of the new scheme for position and trajectory control is illustrated by experiments on an industrial piston-driven cylindrical actuator with proportional valves.
Progressive Learning: A New Approach to Stable Adaptive Control of High Relative-Degree Systems
Authors: Yang Boo-Ho , Asada Haruhiko H.
Published: February 2008

A novel approach to stable adaptive control of complex systems with high relative orders is presented. A series of reference inputs are designed so that the system can learn control parameters stably and progressively, starting with the ones associated with low frequencies and moving up to those having a full spectrum. This progressive excitation method, termed “progressive learning,” allows for stable adaptive control even when a system’s relative order is three or higher. An averaging method is used to obtain stability conditions in terms of the frequency contents of the reference inputs. Based on this analysis, we prove that the stable convergence of control parameters is guaranteed if the system is excited gradually in accordance with the progress of the adaptation by providing a series of reference inputs having appropriate frequency spectra. A numerical example is provided to verify the above analysis.
Consistent Task Specification for Manipulation Systems With General Kinematics
Authors: Prattichizzo Domenico , Bicchi Antonio
Published: February 2008

Although most of the literature on manipulation systems deals with systems with as many degrees of freedom as the dimension of their task space, or even with more (redundant manipulators), kinematically defective manipulation systems are often encountered in robotics, in particular when dealing with simple industry-oriented grippers, or when the whole surface of the manipulator limbs is exploited to constrain the manipulated object, as in “whole-arm” manipulation. Kinematically defective systems differ from nondefective and redundant manipulation systems in many ways, some of which have been addressed in the literature. In this paper, we focus on one of the central problems of manipulation, i.e., controlling the manipulator in order to track a desired object trajectory, while guaranteeing that contact forces are controlled so as to comply with contact constraints (friction bounds, etc.) at every instant. We attack this problem by an unified approach that is appropriate for manipulation systems with general kinematics. When dealing with kinematically defective systems, it is not possible to assign arbitrary trajectories of object motions and contact forces. To understand what restrictions position and force reference trajectories should exhibit in order to be feasible by a given system, is the central issue of this work.
On-Line Estimation of Laser Weld Penetration
Authors: Tu Jay F. , Lankalapalli Kishore N. , Gartner Mark , Leong Keng H.
Published: February 2008

High-power CO2 laser welding has been widely used in the industry because of its high productivity and excellent weld quality. In order to tap the potential of this process completely, it is important to have on-line weld quality inspection methods to improve the process productivity and reliability by achieving 100 percent weld inspection. Weld penetration is one of the most important factors critical to the quality of a laser weld. However, it is very difficult to directly measure the extent of penetration without sectioning the workpiece. In this paper a model-based penetration depth estimation technique suitable for the production environment is developed. The proposed model relates the temperature measured on the bottom surface of the workpiece, weld bead width, laser beam power and welding speed to penetration depth. The closed-loop depth estimator combines the model and a model-error compensator to compensate for the uncertainty in the measurement of the laser power and absorptivity. Other effects considered are the averaging due to the finite size of the sensor, delay based on the sensor location and the process and sensor dynamics. Several bead-on-plate and butt welds were made on low carbon steel plates to validate the static process models and the depth estimation scheme. Temperatures on the bottom surface of the workpiece during welding were measured using infrared thermocouples. The welds were sectioned longitudinally to obtain the penetration profile. The penetration profiles estimated by the depth estimator matched satisfactorily with the measured penetration profiles. The results validate the capability of the proposed depth estimator to estimate penetration depth and its ability to trace the dynamic changes in penetration depth.
Dynamic Modeling and Optimal Control of Rotating Euler-Bernoulli Beams
Authors: Zhu W. D. , Mote C. D.
Published: February 2008

The nonlinear integro-differential equations, describing the transverse and rotational motions of a nonuniform Euler-Bernoulli beam with end mass attached to a rigid hub, are derived. The effects of both the linear and nonlinear elastic rotational couplings are investigated. The linear couplings are exactly accounted for in a decoupled Euler-Bernoulli beam model and their effects on the eigensolutions and response are significant for a small ratio of hub-to-beam inertia. The nonlinear couplings with a resultant stiffening effect are negligible for small angular velocities. A discretized model, suitable for the study of large angle, high speed rotation of a nonuniform beam, is presented. The optimal control moment for simultaneous vibration suppression of the beam at the end of a prescribed rotation is determined. Influences of the nonlinearity, nonuniformity, maneuver time, and inertia ratio on the optimal control moment and system response are discussed.
Controller Design of a Distributed Slewing Flexible Structure—A Frequency Domain Approach
Authors: Yang S. M. , Jeng J. A. , Liu Y. C.
Published: February 2008

The vibration control of a slewing flexible structure by collocated and noncollocated feedback is presented in this paper. A stability criterion derived from the root locus method in frequency domain is applied to predict the closed-loop system stability of the distributed parameter model whose analytical transfer functions are formulated. It is shown that the control law design requires neither distributed state sensing/estimation nor functional feedback gain; moreover, the spillover problem associated with discrete parameter model can be prevented. Implementation of the noncollocated feedback in a slewing beam experiment validates that the control law is effective in pointing accuracy while suppressing the tip vibration.
Discrete-Time Sliding Mode Control: The Linear Case
Authors: Misawa E. A.
Published: February 2008

This paper discusses the application of a class of discrete-time sliding mode controllers (DSMC) which was previously shown to be robustly stable. Further insight into design and performance of DSMC is obtained considering the case of linear plants. A simple numerical example is used to illustrate the properties of this technique.
Dynamic Analysis of Flexible Manipulator Arms With Distributed Viscoelastic Damping
Authors: Zijie Fan , Bingheng Lu , Ku C. H.
Published: February 2008

The main objective of this work is to predict the effect of distributed viscoelastic damping on the dynamic response of multilink flexible robot manipulators. A general approach, based on the principle of virtual work, is presented for the modeling of flexible robot arms with distributed viscoelastic damping. The finite element equations are developed, and a recurrence formulation for numerical integration of these equations is obtained. It is demonstrated, by a numerical example, that the viscoelastic damping treatments have a significant effect on the dynamic response of flexible robot manipulators.
Reciprocal Variable Feedback: Induced Sensing for Nonlinear Systems Design and Control
Authors: Gogoussis Aristides , Donath Max
Published: February 2008

System performance can be significantly improved when both the design of the plant and of the controller are considered concurrently. Control theory can be applied to a broad variety of systems, including those that are physical in nature and many that are not. Despite the generality of control theory, there are many situations in which opportunities are missed for using less conservative control laws and simpler overall implementations. This is due to the use of formulations that do not explicitly reveal the existence of intrinsic information pertaining to the particular domain of application. Such is the case with many physical systems. However, the various constraints associated with physical reality (in the form of principles, laws, etc.) open up several possibilities which can be exploited for system design and control. In this paper, we propose the Reciprocal Variable Feedback principle as a means for facilitating the control of plants with complicated nonlinear dynamics in the presence of parameter and/or structural uncertainty. The RVF principle exploits the effort-flow relationships associated with power interactions in order to assist in the design and control of physical processes. This is accomplished by using appropriate sensors instead of computation based on models (e.g., feedback linearization) and can be implemented within many physical domains. A motion control example is used to provide insight into the nature of the principle. It is expected that in the future, additional principles will be identified and introduced for integrating design with the control of dynamical systems.
Conditions for the Input-Output Relation of Perfect-Mixing Processes to be First Order With Application to Building Ventilation Systems
Authors: Federspiel C. C.
Published: February 2008

Perfect-mixing models are commonly used for analyzing the performance of building ventilation systems. Recently, they have been used to estimate the strength of gas sources in buildings. However, buildings are generally partitioned in such a way that scalar first-order models are insufficient to completely describe the dynamic behavior of the gas transport in buildings. This paper addresses the question of when scalar, first-order differential equations are useful for describing the aggregate dynamical behavior of multi-variable perfect-mixing processes. Sufficient conditions for the input-output relation of a multi-variable perfect-mixing process to be a first-order differential equation are derived. The conditions are related to sensor location and system design. It is shown that the design condition is too restrictive to be widely applicable. Therefore, an alternative first-order relationship is derived by replacing the design condition with a leakage condition. The results enable the estimation of aggregate parameters of multi-zone ventilation systems from scalar, first-order differential equations, which substantially simplifies the estimation problem.
A Frequency Domain Model-Order-Deduction Algorithm for Linear Systems
Authors: Wilson B. H. , Taylor J. H.
Published: February 2008

Physical system modeling, whether automated or manual, requires a systematic procedure to choose the appropriate order of a system model. This can be most readily accomplished by determining the appropriate order of the component submodels. With previous schemes, the primary means to determine the required order of component submodels has been to focus on the eigenvalues of the model, specifically, the behavior of the eigenvalues inside of a circle in the complex plane defining a given spectral radius. In this paper we develop a new algorithm, FD-MODA, that uses changes in a model’s frequency response as an algorithm-stopping-criterion. The model’s frequency response provides a more comprehensive indication of model performance and adequacy than just the eigenvalues, and is more meaningful in the context of frequency-domain controller design methods.
Flight Control Law Design Using Dynamic Inversion for Linear Parameter Varying Systems
Authors: Malloy D. , Chang B. C.
Published: February 2008

A regulator design technique is presented for linear parameter varying (LPV) systems. This technique may be applied to many different types of systems, including nonlinear, due to the broad class of systems that may be represented by LPVs. The regulator, consisting of an inner loop and an outer loop, renders the closed-loop system’s steady-state input-output to be linear time invariant (LTI) and causes the output to track a commanded trajectory. With real-time, accurate parameter data, the inner loop effectively cancels the parameter dependent terms. The outer loop is designed using LTI H∞ synthesis to enable the closed loop system to meet stability and performance goals. Due to the inner loop controller and imperfect parameter cancellation, the complete closed-loop system is likely to be a nonlinear function of the parameters and their derivatives. To assess the stability using the quadratic Lyapunov test, we model the closed-loop system as a polytopic system. The key ideas are illustrated with a nonlinear aircraft flight control example.
Parameter Sensitivity Analysis for Design and Control of Force Transmission Systems
Authors: Hayward Vincent , Cruz-Herna´ndez Juan Manuel
Published: February 2008

We apply sensitivity analysis to the design and control of force transmission systems. With this approach, the effect of the values of the system parameters on the response can be investigated: transmission ratio, sensor placement, damping, and allowable load variation. It is then found that feedback must be applied to reduce the sensitivity of the system response to the load. Based on these observations, a loop shaped feedback compensator design is proposed. Such compensators can compensate for the nonlinear behavior of the transmissions due to friction, while exhibiting good disturbance rejection and robustness. This is achieved without detailed knowledge of friction behavior and without measurement nor estimation of velocity. Experimental results using a test bench are discussed.
Yaw Rate Estimation for Vehicle Control Applications
Authors: Sivashankar N. , Ulsoy A. G.
Published: February 2008

This paper describes a method for vehicle yaw rate estimation using two accelerometers and a steer angle sensor. This yaw rate estimate can be used as an inexpensive alternative to commercial yaw rate sensors in vehicle control applications. The proposed method combines two complementary approaches to yaw rate estimation using accelerometers. This new method is superior to either method used by itself. This paper presents the new approach, supporting analyses, simulation results and experimental validation. The simulation results are based upon both linear and nonlinear vehicle dynamics models and include important effects such as sensor drift and noise, disturbances acting on the vehicle, and model uncertainties. The experimental validation is based on test data from a specially instrumented vehicle driven on a test track. These results indicate that the proposed yaw rate estimation scheme performs well for a wide range of operating conditions and is not difficult to implement.
The Design of a Control Coupled Observer for the Longitudinal Control of Autonomous Vehicles
Authors: Choi Seibum Ben
Published: February 2008

This paper presents a distance observer that was developed for the longitudinal control of autonomous vehicles. The observer is implemented on a platoon of test vehicles as part of the California PATH research program. The experimental results show that the observer filters out the sensing error very effectively without any noticeable phase lag.
Robust H∞ State Feedback Control With Regional Pole Constraints: An Algebraic Riccati Equation Approach
Authors: Wang Zidong
Published: February 2008

This paper focuses on the controller design for uncertain linear continuous-time systems with H∞ norm and circular pole constraints and addresses the following multiobjective simultaneous realization problem: designing a state feedback controller such that the closed-loop system, for all admissible parameter uncertainties, simultaneously satisfies the prespecified H∞ norm constraint on the transfer function from disturbance input to output and the prespecified circular pole constraint on the closed-loop matrix. An effective, algebraic, modified Riccati equation approach is developed to solve this problem. The existence conditions, as well as the analytical expression of desired controllers, are derived. A numerical example is provided to show the directness and effectiveness of the present approach.
Boundary Control of an Axially Moving String Via Lyapunov Method
Authors: Fung Rong-Fong , Tseng Chun-Chang
Published: February 2008

This paper presents the active vibration control of an axially moving string system through a mass-damper-spring (MDS) controller at its right-hand side (RHS) boundary. A nonlinear partial differential equation (PDE) describes a distributed parameter system (DPS) and directly selected as the object to be controlled. A new boundary control law is designed by sliding mode associated with Lyapunov method. It is shown that the boundary feedback states only include the displacement, velocity, and slope of the string at RHS boundary. Asymptotical stability of the control system is proved by the semigroup theory. Finally, finite difference scheme is used to validate the theoretical results.
Zero Dynamics of Physical Systems From Bond Graph Models—Part I: SISO Systems
Authors: Huang S. Y. , Youcef-Toumi K.
Published: February 2008

Zero dynamics is an important feature in system analysis and controller design. Its behavior plays a major role in determining the performance limits of certain feedback systems. Since the intrinsic zero dynamics can not be influenced by feedback compensation, it is important to design physical systems so that they possess desired zero dynamics. However, the calculation of the zero dynamics is usually complicated, especially if a form which is closely related to the physical system and suitable for design is required. In this paper, a method is proposed to derive the zero dynamics of physical systems from bond graph models. This method incorporates the definition of zero dynamics in the differential geometric approach and the causality manipulation in the bond graph representation. By doing so, the state equations of the zero dynamics can be easily obtained. The system elements which are responsible for the zero dynamics can be identified. In addition, if isolated subsystems which exhibit the zero dynamics exist, they can be found. Thus, the design of physical systems including the consideration of the zero dynamics become straightforward. This approach is generalized for MIMO systems in the Part II paper.
Tangential-Contouring Controller for Biaxial Motion Control
Authors: Lo Chih-Ching , Chung Ching-Yei
Published: February 2008

In biaxial contour tracking applications, the main concerns are the tangential and the contour errors. This paper presents a tangential-contouring controller to achieve effect and decoupled control of these concerns. The proposed controller is based on a coordinate transformation between the X-Y frame and a tangential-contouring (T-C) frame that is defined along the contour. Experimental evaluation for the proposed controller is conducted on a biaxial positioning table.
Robust Control for Constrained Robot Manipulators
Authors: Mnif F. , Boukas E. K. , Saad M.
Published: February 2008

In this paper, a robust control law for constrained manipulators with parametric uncertainties is derived. Two schemes are presented; the first, based on The Corless-Leitmann approach, will guarantee ultimate uniform stability of the system, and hence uniform boundedness errors convergence. As a second approach, a class of continuous feedback controls is proposed to guarantee asymptotic stability of the uncertain system. The analysis is based on a theoretical result of asymptotic stability. In this approach, due to the continuity of the control and asymptotic stability of the system, we can achieve acceleration convergence and, thus, constraint force convergence.
Lane Geometry Perception and the Characterization of Its Associated Uncertainty
Authors: Lin Chiu-Feng , Ulsoy A. Galip , LeBlanc David J.
Published: February 2008

This paper addresses the reconstruction of down-range road geometry from imaging sensors for application to motor vehicle active safety systems. This study assumes measurements of lane marker locations in the previewed scene are available from an imaging sensor. An algorithm is developed to extend the perception range of a single-far-field sensor to alleviate the field of view problem. Two steady-state Kalman filters and a least square curve fitting scheme are developed to compute estimates of the road geometry. Simulations are used to compare the performance of the different road modeling schemes for different roadway scenarios, providing insights useful for selecting model-based road geometry estimation techniques. Finally, an algorithm to characterize the uncertainty in road geometry perception is proposed and validated.
Passivity-Based Versus Disturbance Observer Based Robot Control: Equivalence and Stability
Authors: Bickel Robert , Tomizuka Masayoshi
Published: February 2008

Disturbance observer based robot control algorithms provide good control performance while giving a straightforward method of gain selection. Unfortunately, the stability of these algorithms has not been shown rigorously for nonlinear systems such as robots. This paper demonstrates that a disturbance observer based algorithm can be made equivalent to the well-known passivity-based approaches of Sadegh and Horowitz, and Slotine and Li. This is accomplished by choosing a specific design of the Q(s) filter (described in the paper) of the disturbance observer. By doing so, the stability of the disturbance observer based approach can be proven rigorously. An additional benefit of the equivalence of the two approaches is the ability to combine an adaptive controller to the disturbance observer based approach.
Dynamics of Golf Ball-Hole Interactions: Rolling Around the Rim
Authors: Hubbard Mont , Smith Tait
Published: February 2008

A previous study of a golf ball rolling on the rim of a cup neglected the spin of the ball about a line perpendicular to the plane of contact. The capture process is studied here by numerically solving the equations for rolling without slipping on the rim. The boundary in the velocity-impact parameter space separating roll-in and roll-out trajectories corresponds to initial conditions for a set of near guasi-equilibrium trajectories. Stability of the equilibrium trajectories is investigated using symbolic linearization of perturbation solutions from them. Although the locally unstable equilibrium trajectories themselves are not attainable from the two-space of pure rolling initial conditions, the boundary is nevertheless a “barrier” in that it corresponds to long contact times and large roll around angles.
A Dynamic Model for Condition Monitoring of a High-Power CO2 Industrial Laser
Authors: Tu J. F. , Katter J. G. , Monacelli L. E. , Gartner M.
Published: February 2008

Industrial laser systems handle high power consumptions and may function under undesirable operating conditions if the systems are not properly maintained. It is sometimes difficult to diagnose why a laser is not functioning properly because the optical output is the result of complex interactions among many parameters such as the total gas pressure, effectiveness of the laser cooling system, operating environment, and gradual deterioration of laser components. In this paper, a dynamic power distribution model is developed to characterize the power distribution of a high-power transverse-flow DC-excited CO2 laser to account for dynamic effects such as continuously ramping up and down the laser output power and the cyclic nature of the chiller. The model contains the essential dynamic features of a CO2 laser system and yields solutions sufficiently accurate for practical diagnostic purposes.
Control of Sensory Perception in Discrete Event Systems Using Stochastic Dynamic Programming
Authors: Hovland G. E. , McCarragher B. J.
Published: February 2008

The problem of controlling sensory perception for use in discrete event feedback control systems is addressed in this paper. The problem consists of the real-time dynamic selection of different discrete event recognition techniques, which produce confidence levels of the recognized events. For a discrete event control system running in normal operation, the confidence levels are typically large and only a few event recognizers are needed. Then, as the event recognition becomes harder, the confidence levels will decrease and additional event recognizers are utilized by the sensory perception controller. The final product is an intelligent architecture with the ability to actively control the use of sensory input and perception to achieve high performance discrete event recognition.
Robust Disturbance Rejection for Left-Invertible Linear Systems With Nonlinear-Uncertain Structure
Authors: Koumboulis F. N. , Skarpetis M. G.
Published: February 2008

The problem of robust disturbance rejection for left invertible linear systems, with nonlinear uncertain structure and with measurable and nonmeasurable disturbances, is solved via an independent from the uncertainties static measurement output feedback law. The necessary and sufficient conditions for the problem to have a solution are established. The general explicit expression of the measurement output feedback matrix and the measurement disturbances feedback matrix are derived. The feedback invariant poles are determined. Sufficient conditions for robust disturbance rejection with simultaneous robust stability are also established. The rejection of the influence of the rotary gust disturbing the vertical velocity of the longitudinal motion of an aircraft is achieved.
Robust Tracking Control of a Direct Drive Robot
Authors: Kang Bong Soo , Kim Soo Hyun , Kwak Yoon Keun , Smith Craig C.
Published: February 2008

This paper presents a robust controller for tracking control of a direct-drive robot. The proposed controller consists of two portions: a computed torque method which precompensates for dynamics of the modeled plant and an H∞ controller which postcompensates for residual errors which are not completely removed by the computed torque method. Experimental methods for identifying appropriate model structure and parameters are presented, and three specific controller types are compared. Using the robot designed in our laboratory, the combined controller reduced tracking errors by one half compared to computed torque control alone, and by one sixth compared to conventional independent joint control.
Hybrid Modeling for Mechanical Systems: Methodologies and Applications
Authors: Ploemen I. H. J. , van de Molengraft M. J. G.
Published: February 2008

A serial hybrid modeling approach is applied to mechanical systems. Here, hybrid means that models are based on combined structural and empirical approaches. The main system behavior is described by a physical model, while complex internal forces are modeled by black box neural networks. For a special class of systems this methodology is extended and a novel approach is presented modeling the whole system behavior by hierarchical neural networks, that fit the relation between system outputs and internal system variables. Useful information about the nonlinear system can be extracted from the resulting models. The power of hybrid modeling is illustrated with experimental results and some important issues considering the practical implementation are dealt with.
Reduction of Limit Cycle Amplitude in the Presence of Backlash
Authors: Boneh Ronen , Yaniv Oded
Published: February 2008

The majority of feedback systems driven by an electric motor can be represented by a two-mass system connected via a flexible drive element. Owing to the presence of backlash, the closed-loop performance such as precision speed, position and force control that can be achieved using a linear time invariant controller is limited, and it is expected that a nonlinear control would be superior. In this paper a nonlinear control structure is proposed and a systematic design technique presented. The advantages of the proposed design technique are: (i) It is robust to plant and backlash uncertainty; (ii) it is quantitative to specifications on the maximum limit cycle amplitude; and (iii) the closed loop is superior to a linear controller design both in lower bandwidth and in lower limit cycle amplitude. A design example is included.
Systems With Variable Geometry: Concept and Prospects
Authors: Vukobratovic Miomir , Potkonjak Veljko
Published: February 2008

The problem of active systems from the aspect of adaptation to different working conditions is discussed. The attempt to meet all the requirements very often leads to conflict situations. This paper investigates the possibility of approaching this problem through system reconfiguration. Thus, a new function is proposed to improve the basic properties of active systems: the system can, in a purposeful way, adjust its geometry to different dynamic requirements. In this way, it is possible to achieve better system performance.
State and Information Estimation for Linear and Nonlinear Systems
Authors: Mutambara Arthur G. O. , Al-Haik M. S.
Published: February 2008

A new information space based estimation algorithm for nonlinear systems is presented. First, an outline of the algebraic equivalent of the Kalman filter, the Information filter, is discussed. Employing the principles used in the derivation of the extended Kalman filter (EKF), the linear information space is then extended to nonlinear information space. In this way, the extended Information filter (EIF) is derived, which is the key contribution of the paper.
Solutions of Continuous-Time Preview Two-Player Differential Games
Authors: Ma Wen-Hou , Peng Huei
Published: February 2008

The continuous-time two-player preview game problems are studied in this paper. A preview game problem is formulated when the input signals generated by one of the two players are delayed (e.g., by actuator dynamics), and are previewed by the other player. In accordance with the control terminology, these two players are referred to as the control player and the disturbance player, respectively. Both control-advantaged and disturbance-advantaged game solutions are presented. When the solution of an infinite horizon problem exists, the response of the closed-loop system can be analyzed in the frequency domain. A vehicle handling problem is used as an example for the analysis. It is shown that the preview action of the advantaged player effectively reduces the authority of the disadvantaged player, and results in significantly improved performance compared with feedback-only game algorithms.
Robust Stochastic Stabilization of Discrete-Time Linear Systems With Markovian Jumping Parameters
Authors: Boukas El Kebi´r , Shi Peng , Benjelloun Khalid
Published: February 2008

In this paper, we study the problem of robust stabilization of discrete-time linear systems with Markovian jumping parameters (DTLSMJP) with norm bounded uncertainties. A sufficient condition guaranteeing te robust stability of the uncertain discrete-time linear systems with Markovian jumping parameters (UDTLSMJP) is presented, which is in terms of a set of coupled discrete-time algebraic Riccati inequalities (IEqs). Finally, a numerical example is given to show the potential of the proposed technique.
Optimizing the Feedback Gains of the Robust Linear Regulator
Authors: Huang Jie
Published: February 2008

This paper aims to improve the transient response of a linear regulator system by optimizing the feedback gains associated with a fixed set of desirable eigenvalues of the closed-loop system. The optimal feedback gain is such that the Frobenius norm of the steady state of the compensator is minimized. Computer simulation shows that this scheme is effective in improving the transient response of the regulator system.
Plant Template Generation for Uncertain Plants in Quantitative Feedback Theory
Authors: Chen Wen-Hua , Ballance Donald J.
Published: February 2008

The creation of templates for uncertain plants is an essential first step in Quantitative Feedback Theory (QFT) and other frequency domain methods. For plants with structured parametric uncertainty it is shown that the boundaries of templates can only be generated by the edges of the uncertain parameter set and particular critical interior points. A method to identify these critical interior points is presented. With the help of symbolic computation, a computationally tractable procedure for generating the templates is developed. The procedure is illustrated with an example of a vehicle clutch system where the uncertain parameters perturb the plant nonlinearly.
A Unified Hamiltonian Approach for LQ and H∞ Preview Control Algorithms
Authors: Mianzo Lawrence , Peng Huei
Published: February 2008

A framework for solving both the continuous and discrete-time LQ and H∞ preview control algorithms is presented in this paper. The tracking control of an automotive durability test rig is used as an application example. Simulation results are presented to illustrate the effectiveness of the preview control algorithms.
Stochastic Modeling of Fatigue Crack Damage for Risk Analysis and Remaining Life Prediction
Authors: Ray Asok
Published: February 2008

This paper presents a stochastic model of fatigue crack damage in metallic materials that are commonly encountered in structures and machinery components of complex mechanical systems (e.g., aircraft, spacecraft, and power plants). The constitutive equation of the damage model is based on the physics of fracture mechanics and is validated by Karhunen-Loe`ve analysis of test data. The (nonstationary) probability distribution function (PDF) of fatigue crack damage is generated in a closed form without numerically solving stochastic differential equations in the Wiener integral or Itoˆ integral setting. The crack damage model thus allows real-time execution of decision algorithms for risk assessment and life prediction on inexpensive platforms such as a Pentium processor. The model predictions are in close agreement with experimental data of fatigue crack growth statistics for 2024-T3 and 7075-T6 aluminum alloys.
Kinematic Control of Robots With Joint Constraints
Authors: Allotta Benedetto , Colla Valentina , Bioli Gianluca
Published: February 2008

Kinematic control of robot manipulators requires that joint mechanical limits are taken into account in order to avoid the interruption of the task at hand if joint limits are reached. A novel approach to this problem is presented and compared with state of the art techniques. The proposed control scheme allows to explicitly include in the specification of the task position, velocity and acceleration costraints for the joints. An application to an existing redundant arm is discussed and experimental results are presented.
Dynamic Modeling and Control of Dual Wheeled Mobile Robots Compliantly Coupled to a Common Payload
Authors: Vinay Thurai , Postma Bradley , Kangsanant Theo
Published: February 2008

Lagrange formalism is applied to derive a dynamic model, and design a nonlinear controller for two nonholonomic, differentially steered, wheeled mobile robots compliantly linked to a common payload. The resulting multivariable system model is of a large order and can be block decoupled by selective state feedback into five independent subsystems, two of which effectively represent the deviation dynamics of the individual robots from a prescribed path; two others represent their forward motion dynamics; while the fifth describes the payload dynamics. Controllers for each of the robot subsystems, including self-tuning adaptive controllers for the nonlinear deviation dynamics subsystems, are designed by the pole-placement technique. System performance is then evaluated via simulation for the case where each robot is undergoing curvilinear motion.
Design of An IC Engine Torque Estimator Using Unknown Input Observer
Authors: Kim Yong Wha , Rizzoni Giorgio , Wang Yue-Yun
Published: February 2008

The torque produced by each combustion in an engine is one of the most important indices tied to internal combustion engine performance. In this paper, an approach is investigated to estimate engine torque. Instead of employing expensive and delicate combustion pressure sensors to directly measure indicated pressure in each cylinder, unknown input observers are exploited to estimate cylinder indicated torque using one or more low-cost measurements of crankshaft angular position. Necessary and sufficient conditions for the existence of such torque estimators for multi-cylinder engines are presented in the paper; these include the number of angular position sensors required and their suggested placement. Model reduction issues and the number of measurements required to obtain an acceptable estimate are also considered. The approach is applied to a six-cylinder industrial diesel engine.
Brake System Modeling for Simulation and Control
Authors: Gerdes J. Christian , Hedrick J. Karl
Published: February 2008

This paper presents reduced-order models of brake system dynamics derived from a physical modeling perspective. The vacuum booster model combines a static control valve with dynamic air flows, resulting in the ability to easily reproduce both static hysteresis effects and rapid transients. Following the assumption of incompressible flow, a four-state model of the brake hydraulics is presented and, subsequently, reduced to one or two states for certain applications. Experimental results support the simplifying assumptions made during the modeling process by demonstrating better agreement with the response from pedal force to brake pressure than previously displayed in the literature. These models are intended for use in the design and analysis of vehicle control systems and the evaluation of driver/vehicle interactions through dynamic simulation.