bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Linear-Optimal Control Laws for Active Suspension Systems
Authors: Ray L. R.
Published: March 2008

The stability robustness of linear-optimal control laws for quarter-car active suspension systems is evaluated using stochastic robustness analysis. Simultaneous parameters variations and neglected actuator and sensor dynamics are considered for LQ active suspension systems and for a single-measurement LQG system to determine the effects of uncertainty on system stability. The results indicate that neglected actuator and sensor dynamics have a small effect on stability robustness, while parameter uncertainty, particularly that of the “sprung mass” is of great concern. The effectiveness of Loop Transfer Recovery on active suspension systems with both parameter uncertainty and higher-order uncertainty is discerned. The analysis shows that when Loop Transfer Recovery is applied arbitrarily to uncertain systems, both estimator performance and system robustness can decrease. Nevertheless, it is concluded that the impact of the robustness recovery method is determined by stochastic stability robustness analysis, and the recovery design parameter that provides sufficient robustness with minimal performance degradation is readily identified. The effect of LQ design parameters on robustness also is considered. The paper presents robustness analysis and synthesis methods for a quarter-car model that can be applied to higher-order active suspension systems.
A Low Cost Active Anti-Roll Suspension for Passenger Cars
Authors: Darling J. , Dorey R. E. , Ross-Martin T. J.
Published: March 2008

This paper examines, through simulation, a low cost active suspension system intended for use on passenger vehicles. The system retains the conventional suspension spring and damper elements and replaces the anti-roll bar with an active device, responding to transducer signals on the vehicle. Whilst conventional passive suspensions are at best a compromise solution to the conflicting requirements of ride and handling, this new system aims to prevent roll and thus improve passenger comfort and safety. The ride and handling of a standard production vehicle with a passive suspension is studied using a simulation model incorporating measured parametric data. A model of the same vehicle with active roll control is developed and the improvements in ride and handling are established. The effect of limited bandwidth performance from the central controller and hydraulic components is investigated by simulation. The vehicle model can be used to predict performance and help the automotive engineer in the difficult task of system design.
Walking Without Impacts as a Motion/Force Control Problem
Authors: Blajer W. , Schiehlen W.
Published: March 2008

The paper deals with the synthesis of control for impactless bipedal walking. In order to avoid impacts, both the specified motion of the biped and its ground reactions are controlled, yielding a combined motion and force control problem. A method for modeling and solving such problems is proposed, and then illustrated by the example of an impactless planar walk of a seven-link bipedal robot. Some numerical results of the motion simulation are reported.
Models of a Pneumatic PWM Solenoid Valve for Engineering Applications
Authors: Ye N. , Scavarda S. , Betemps M. , Jutard A.
Published: March 2008

PWM (Pulse width modulated) solenoid valves possess the advantages of low cost, high flow rate gain, and simple structure. However, the use of a PWM solenoid valve causes both discontinuity and nonlinearity of the flow rate; this results in difficulties of modeling and of control. This paper presents our work on modelling a pneumatic PWM solenoid valve for engineering applications. Two models are presented: one is the instantaneous mass flow rate model which can be used in the simulation to study the dynamic behavior of pneumatic PWM control systems; another model is the equivalent mass flow rate model which is developed for facilitating the synthesis of pneumatic PWM servomechanisms. An equation for determining the maximum operating modulation ratio of the PWM solenoid valve is also presented. Simulated results using the established models are compared with the experimental results for both the static characteristics of a PWM solenoid valve and the dynamic behavior of a system composed of a PWM solenoid valve and a constant volume chamber.
Computer Simulation of a Test Rig to Model Sloshing in Spin-Stabilized Satellites
Authors: Flugrad D. R. , Obermaier L. A.
Published: March 2008

Certain communications satellites carry liquid stores on board for station tending and attitude adjustment. However, sloshing of the liquid can cause an undesirable nutational motion of the spin-stabilized vehicle. In previous work a test rig was designed, built and instrumented to study the interaction between the rotating structure and liquid. To augment that experimental project, a computer model of the test rig has been developed to simulate the dynamic motion of the system for various parameter values. The sloshing liquid was replaced by a two degree-of-freedom pendulum in the mathematical model. Simulation results were compared with those from a general multibody dynamics program and with experimental measurements of the test rig motion to demonstrate the mathematical model’s validity. Good agreement was achieved in both instances.
An Optimal Multivariable Controller With Application to Steam Temperature Control in a Boiler
Authors: Surgenor B. W. , Pieper J. K.
Published: March 2008

An optimal multivariable controller has been designed for superheater steam temperature control in a drum boiler. The controller takes the form of a linear quadratic regulator with supplementary states for added integral action. By means of a nonlinear model of the power plant, the performance of the controller is compared with that of the existing plant control system which consists of a set of PI controllers with feedforward action. The simulation results indicate that the superior performance of the digital controller justifies the expense of a control system retrofit.
Noncolocated Control of a Damped String Using Time Delay
Authors: Yang B.
Published: March 2008

Recent research studies noncolocated control of flexible mechanical systems using time delay. The developments are limited to undamped flexible systems; damped flexible systems have not been considered. This paper investigates noncolocated vibration control of a viscously damped string using time delay. The control system is formulated in the Laplace transform domain. Based on the understanding of the system eigenstructure, a modified Bode plot of the feedback controller is introduced in a design region. The Bode plot designed, along with a specific time delay in the feedback loop, proper sensor and actuator positions, and proper control gain, guarantees stabilization of vibration of the damped string.
Discrete-Time Repetitive Control System Design Using the Regeneration Spectrum
Authors: Shaw F.-R. , Srinivasan K.
Published: March 2008

The stability, transient response, and stability robustness of discrete-time repetitive control systems characterized by large values of the time delay inherent in such systems are examined here using a function of frequency termed the regeneration spectrum. The ability to infer different aspects of controlled system performance from the regeneration spectrum, and its ease of computation, makes it a valuable tool for controller analysis and synthesis. A design procedure for discrete-time repetitive control systems, based on the regeneration spectrum, is outlined and a controller form suggested to effectively handle the trade-off between the different aspects of controlled system behavior. The controller design procedure is applied to an electrohydraulic material testing application characterized by strong nonlinearities, and shown experimentally to be effective in improving the controlled system performance.
Robust Time-Delay Control
Authors: Singh T. , Vadali S. R.
Published: March 2008

A method is presented to minimize residual vibration of structures or lightly damped servomechanisms. The method, referred to as the proportional plus multiple delay (PPMD) control, involves the use of multiple time delays in conjunction with a proportional part to cancel the dynamics of the system in a robust fashion. An interesting characteristic of the controller involves addition of a basic single time-delay control unit in cascade to the existing controller, for every additional requirement of robustness. It is shown that the proposed time-delay controller produces results that are exactly the same as those obtained by the shaped input technique. In addition, it is simpler to arrive at the relative amplitudes of the time-delayed signals for any number of delays even in a multi-input setting.
A 50-Year History of the Dynamic Systems and Control Division
Authors: Franke M. E. , Lynch P. M. , Healey A. J.
Published: March 2008

The Division began as a technical committee in 1936 and became the Industrial Instruments and Regulators Division in 1943. Significant events and broadening technology that led to Division name changes and evolution are described. The Division received its current name in 1977. The leadership role of the Division in the field of dynamic systems and control is outlined. Objectives, scope, and activities of the Division are discussed, and statistical data and trends are given.
The Computer as Liberator: The Rise of Mechanical System Control
Authors: Auslander David M.
Published: March 2008

In this essay, on the observance of the 50th anniversary of the founding of ASME’s Dynamic Systems and Control Division, I try to connect the technology of control to the way in which control practitioners think. Despite some tension between the conclusions implied in the introductory paragraphs and conclusions drawn later in the essay, I have left them to stand in their original form to emphasize tensions in control thinking, for which the source might not be apparent. The opinions expressed here are strictly my own, but I must acknowledge the creative proddings of my colleagues in getting these thoughts recorded at all.
Controlled Motion in an Elastic World
Authors: Book Wayne J.
Published: March 2008

The flexibility of the drives and structures of controlled motion systems are presented as an obstacle to be overcome in the design of high performance motion systems, particularly manipulator arms. The task and the measure of performance to be applied determine the technology appropriate to overcome this obstacle. Included in the technologies proposed are control algorithms (feedback and feedforward), passive damping enhancement, operational strategies, and structural design. Modeling of the distributed, nonlinear system is difficult, and alternative approaches are discussed. The author presents personal perspectives on the history, status and future directions in this area.
Modeling and Control of Manufacturing Processes: Getting More Involved
Authors: Hardt David E.
Published: March 2008

The discipline of control has had numerous yet sporadic contacts with the manufacturing world over the past few decades, almost always as an afterthought or addendum, and typically in the role of machine and not as process control. Much of this detachment comes from an absence of control techniques that can deal directly with the actual manufacturing process, i.e., a material transformation process that produces a desired object both in terms of specific geometry and internal properties. Instead, most efforts have focused on using existing methods on process independent problems, such as position control and trajectory following, or on straightforward process parameter control, thereby only indirectly influencing the actual process output. This paper presents the reasons behind and the means to eliminate this estrangement, using the author’s own research as an example of a more direct approach to process modeling and control.
Lateral and Longitudinal Dynamic Behavior and Control of Moving Webs
Authors: Young G. E. , Reid K. N.
Published: March 2008

A web refers to any material in continuous flexible strip form which is either endless or very long compared to its width, and very wide compared to its thickness. This paper discusses the dynamic analysis and control of the lateral and longitudinal motions of a moving web which correspond to fluctuations perpendicular and parallel, respectively, to the primary direction of web transport. Historical perspectives are provided, from the early work of Osborne Reynolds in the late 1800s to current research. An overview of the control of both lateral and longitudinal web motion, which includes the control of tension, is presented. Present limitations in understanding and controlling lateral and longitudinal web behavior are discussed. The Journal of Dynamic Systems, Measurement, and Control has played a pivotal role in the advancement of research in this area.
Applications of Optimal Control to Advanced Automotive Suspension Design
Authors: Hrovat D.
Published: March 2008

The paper surveys applications of optimal control techniques to the design of active suspensions, starting from simple quarter-car, 1D models, which are followed by their half-car, 2D, and full-car, 3D, counterparts. The emphasis is on Linear-Quadratic (LQ) optimal control and automotive vehicles.
Engine Control Using Cylinder Pressure: Past, Present, and Future
Authors: Powell J. David
Published: March 2008

Research into the use of cylinder pressure measurements from reciprocating internal combustion engines for real time automotive engine control has been investigated for the last 20 years. The measurement has been investigated for spark timing, fuel-air ratio control, charge temperature measurements, and misfire detection. The cost of the sensors has inhibited widespread use in production vehicles; however, it was introduced in domestic Japanese production for spark control five years ago. Its use for misfire detection is also being actively considered.
Control of Uncertain Nonlinear Systems
Authors: Corless Martin
Published: March 2008

This paper describes some of my research in the analysis and control of nonlinear uncertain systems in which the uncertainties are modeled deterministically rather than stochastically. The main applications are to mechanical/aerospace systems, such as robots and spacecraft; the underlying theoretical approach is based on Lyapunov theory.
On the Design of Digital Tracking Controllers
Authors: Tomizuka Masayoshi
Published: March 2008

This paper describes my work on the design of digital tracking controllers over the past two decades. In tracking control, the control object must be moved along a time varying desired output and the transient path error must be minimized. Tracking control is discussed for the following two typical situations: one is the situation where the desired output is known in advance and the other is where the desired output itself is not known but has a certain known property, e.g., it is periodic with a known period. Control algorithms for dealing with these situations will be reviewed and applications to mechanical systems are discussed.
Robust Internal Model Control
Authors: Tsypkin Ya. Z.
Published: March 2008

This paper discusses the method of control systems design for dynamic plants under bounded uncertainty. The structure of these systems coincides with the structure of systems with an internal model. But the choice of an internal model and a controller depends on the demand of the bounded decrease of system sensitivity to the change of plant characteristics and external action and on the demand of modal control. The absorption principle is used for the synthesis of a controller of such robust modal control systems. The realization conditions of robust systems of modal control are stated.
Frequency Domain Design for Robust Performance Under Parametric, Unstructured, or Mixed Uncertainties
Authors: Jayasuriya Suhada
Published: March 2008

This article looks at direct frequency domain design for satisfying robust performance objectives in uncertain, linear time invariant (LTI) plants embedded in a single feedback loop. The uncertain plants may be described by parametric, nonparametric (or unstructured), or mixed uncertain models. Quantitative Feedback Theory (QFT) is one frequency domain design methodology that is direct and is equally effective with any of these models. It can be separated from other frequency domain robust control methods such as H∞ optimal control, μ synthesis, and LQG/LTR for at least (i) its emphasis on cost of feedback measured in terms of controller bandwidth, (ii) its ability to deal nonconservatively with parametric, nonparametric and mixed uncertainty models, and (iii) its utilization of both amplitude and phase of the loop transfer function, pointwise in frequency, for the quantification of robust performance. An exposition of these attributes, unique to QFT, and the basic design methodology, coupled with a recently developed mathematical framework and some existence results for the standard single-loop QFT problem are the salient features of this paper.
Quantitative Feedback Design of Decentralized Control Systems
Authors: Nwokah Osita D. I. , Yau Chin-Horng
Published: March 2008

In the spirit of practical applicability, design transparency and quantitative specifications, this paper presents a new robust decentralized control design framework—model reference quantitative feedback design (MRQFD)—for multivariable control systems with large plant uncertainty and strong cross-coupling. The MRQFD method provides a connection between Rosenbrock’s Nyquist array and Horowitz’s quantitative feedback theory. There are two main stages in the MRQFD method. First, an internal model reference loop, based on non-negative matrix theory, is used to obtain robust generalized diagonal dominance and hence the reduction of uncertainty in the resultant compensated internal loop system. Then a single-loop quantitative feedback design scheme is applied to solve the resulting series of individual loops to guarantee the satisfaction of predefined MIMO quantitative specifications. The design procedure can be carried out either in the direct or in the inverse plant domains, as in Rosenbrock’s Nyquist array. The conditions of robust diagonal stabilization are also given for the MRQFD framework. The effectiveness of the MRQFD method and its ease of application are demonstrated by a 3 × 3 uncertain multivariable example.
Zero Phase Error Tracking Controllers With Optimal Gain Characteristics
Authors: Funahashi Y. , Yamada M.
Published: March 2008

Recently, a digital feedforward controller, called a Zero Phase Error Tracking Controller (ZPETC), has been proposed. In this controller, the overall frequency response between the desired output and the controlled output exhibits zero phase shift for all frequencies by using a few steps of the future desired output data. In this paper, two extensions of ZPETC’s are proposed: a ZPETC with deadbeat tracking performance and an L2-Optimal ZPETC. These ZPETC’s can provide the overall control system with not only the above phase property but also the excellent tracking performance for a desired output and the superior gain property, respectively. Moreover, a ZPETC with both the excellent tracking performance for a step-type and ramp-type desired output and the superior gain property, called an L2-Optimal ZPETC with deadbeat tracking performance, is presented.
An End-Time Constrained Receding Horizon Control Policy
Authors: MacArthur J. W.
Published: March 2008

A predictive control policy that utilizes a finite time horizon with end-time constraints is described. The control law minimizes actuator movement while satisfying both process and control output constraints imposed at the end of the time horizon. A single user definable parameter, directly related to the desired settling time of the process, can be used to tune the controller. System response to set-point and load disturbances for different linear time invariant plants is presented to illustrate the significant features of the algorithm. Performance relative to conventional PID control is demonstrated as are robustness characteristics for a specific system. Field tests in a heat pump test chamber illustrate actual nonlinear time-varying performance.
Shaped Input Control of a System With Multiple Modes
Authors: Singh T. , Heppler G. R.
Published: March 2008

This paper describes a method for limiting vibration in flexible systems that have more than one characteristic frequency and mode. It is only necessary to have knowledge of the component mode frequencies and damping ratios in order to be able to calculate the timing and magnitudes of the impulse sequence used in the shaping. Only two impulses, in the nonrobust case, or three impulses in a more robust case, are necessary regardless of the number of component frequencies. Simple tests are established to determine when this technique can be used and examples are presented.
Dynamic System Synthesis With a Bond Graph Approach: Part I—Synthesis of One-Port Impedances
Authors: Redfield R. C. , Krishnan S.
Published: March 2008

This is the first part of a two-part paper developing a procedure for impedance synthesis and dynamic system conceptual design using a bond graph approach. The first part examines impedance synthesis with bond graphs and develops some useful properties of impedance related to bond graph structure. The second part of the paper uses the impedance synthesis approach as a tool in conceptual design for generating dynamic system solutions meeting frequency domain input-output specifications. In Part I, impedance and transfer functions are directly formulated from bond graphs. An invertible procedure is developed in order to allow for synthesis. Frequency domain properties of bond graphs are developed that will aid in impedance synthesis and the synthesis of bond graph structures from impedance specifications is formulated with a view toward conceptual design. The synthesis is not unique, a given impedance can be synthesized into multiple bond graph structures depending on its complexity. The work presented focuses on the synthesis of passive impedances but may be generalized for active systems.
Dynamic System Synthesis With a Bond Graph Approach: Part II—Conceptual Design of an Inertial Velocity Indicator
Authors: Redfield R. C.
Published: March 2008

This work develops the conceptual design of an inertial velocity sensor drawing upon the impedance synthesis method in Part I of this paper. Specifications are frequency based impedances and resulting designs are configurations of dynamic energy storing and dissipation elements. The design procedure can be extended to a class of systems design problems where frequency response performance is of primary importance. A key to this work is that the method designs systems from scratch; initial configurations are unknown. As a theme example to demonstrate the utility of the method for conceptual design, constrained and unconstrained inertial velocity sensors are configured based on input-output performance requirements. Such sensors find application in many motion control problems including mechanism and manipulator control, and vibration isolation control. The design methodology generates a number of different sensors that can measure absolute velocity for some or all ranges of frequency.
Sequential Adaptation in Estimating Elastic Boundary-Condition Influence Matrices
Authors: Ben-Haim Yakov , Natke H. G.
Published: March 2008

A method is discussed for adaptive estimation of the boundary-condition influence matrix of a linear elastic system, based on modal measurements (eigenvalues and eigenvectors) and on knowledge of the influence matrix of the system with respect to reference boundary conditions. The estimation is terminated adaptively by an algorithm motivated by the concept of sequential analysis. The boundary-condition influence matrix is re-estimated with measurement of each additional mode, until a termination criterion indicates that adequate accuracy has been attained. The advantage of adaptive termination of the estimation is the enhanced computational (and possibly instrumental) efficiency of estimating with minimal modal data. An analytical technique for comparing the adaptive termination with a reasonable non-adaptive method has been developed and demonstrated by application to a uniform beam. When uncertainty in the boundary conditions is represented by convex models, it is shown that the adaptive estimation can terminate much earlier than the non-adaptive procedure.
Adaptive Tracking Control of an Air Powered Robot Actuator
Authors: McDonell B. W. , Bobrow J. E.
Published: March 2008

An adaptive controller is presented for a one-degree-of-freedom pneumatic actuator. The control law uses full-state feedback for simultaneous parameter identification and tracking control. For position control, a pneumatic actuator with high bandwidth is difficult to obtain because of the compressibility of air and the nonlinear characteristics of air flowing through a variable area orifice. Most previous controllers for gas powered actuators were relatively limited fixed gain or on-off type controllers with low tracking accuracy. Experimental results demonstrate that tracking performance comparable to electric servomotors can be obtained using the algorithm presented despite the nonlinearities and compressibility of air.
A Task Streamlining Approach for Parallel Processing of the Inverse Dynamic Equations With Friction
Authors: Sharan A. M. , Dhanaraj C.
Published: March 2008

Real-time computation of the inverse dynamics of the robotic manipulators is required for ensuring robust control. This paper presents a modified Newton-Euler algorithm which makes use of symbolic programming for improved computational efficiency. Also, friction is incorporated in the dynamic model for more accurate prediction of the torques. The algorithm is parallelized using a “Task Streamlining Approach,”—a systematic mapping scheme using layered task graphs to create the list schedule and a simplified bin-packing heuristic algorithm to schedule the computations on a multiprocessor. The resulting computational load is only 12n + 9 flops (n = number of links in the manipulator), indicating a promise for application to precision robot control employing a high sampling rate. The optimal scheduling of tasks is carried out by minimizing the number of layers where tasks are performed sequentially.
Sliding Control Without Reaching Phase and Its Application to Bipedal Locomotion
Authors: Chang Tai-Heng , Hurmuzlu Yildirim
Published: March 2008

A new variable structure control law based on the Lyapunov’s second method that can be used in trajectory planning problems of robotic systems is developed. A modified approach to the formulation of the sliding domain equations in terms of tracking errors has been presented. This approach possesses three distinct advantages: (i) it eliminates the reaching phase, (ii) it provides means to predict the entire motion and directly control the evolution of tracking errors, (iii) it facilitates the trajectory planning process in the joint and/or cartesian spaces. A planar, five-link bipedal locomotion model has been developed. Five constraint relations that cast the motion of the biped in terms of four parameters are developed. The new control method is applied to regulate the locomotion of the system according to the five constraint relations. Numerical simulation is performed to verify the ability of the controller to achieve steady gait by applying the proposed control scheme. Bifurcation diagrams of the periodic motions of the biped are used to demonstrate the improvements in controller performance that arise from the application of the proposed method.
Development of a Pulse-Width Modulated Pneumatic Rotary Valve for Actuator Position Control
Authors: Royston Tom , Singh Rajendra
Published: March 2008

A new concept in the directional flow control of a high speed pneumatic actuation system is proposed. Two recent developments reported in the literature, namely (i) the application of pulse-width modulation techniques to on-off pneumatic valves and (ii) the introduction of a high speed rotary air valve, are merged in the design of a novel rotary flow control valve with built-in pulse-width modulation. Valve feasibility is demonstrated experimentally through the closed-loop position control of a pneumatic actuator. Static and dynamic performance characteristics as predicted by a detailed nonlinear lumped parameter model, compare favorably with measured data. Additionally, a simple linear time-invariant model, with a few empirical parameters, of the system is developed and validated through comparison with experiment and the nonlinear model. Then, several system design improvements based on this simple linear model are implemented and evaluated with the detailed nonlinear model.
Electromechanics and Vibrations of Piezoelectric Shell Distributed Systems
Authors: Tzou H. S. , Zhong J. P.
Published: March 2008

Smart piezoelectric structures, conventional passive materials integrated with piezoelectric sensors, actuators, and control electronics, have great potentials in many engineering applications. This paper is devoted to a new theoretical development of generic piezoelectric shell distributed systems. System electromechanical equations and boundary conditions for a thick piezoelectric shell continuum with symmetrical hexagonal structure (Class C6v = 6 mm) are derived using Hamilton’s principle and linear piezoelectric theory. Further simplification leads to a set of new electromechanical system equations, three translated coordinates and two rotary coordinates, for piezoelectric shell continua including rotary inertias and transverse shears. For thin piezoelectric shells, the second set system equations are further simplified using Kirchhoff-Love’s assumptions. The converse effect induced electric forces/moments and boundary conditions can be used to control system dynamics via open or closed-loop control systems. Applications of the theories to a plate and shells of revolution (spherical, cylindrical, and conical shells) are demonstrated in case studies.
Using Passive End-Point Motion Constraints to Calibrate Robot Manipulators
Authors: Driels M. R.
Published: March 2008

The concept of using a method to constrain the endpoint of a serial linkage (such as a robot manipulator) in order to identify the kinematic parameters is appealing, since it no longer becomes necessary to use ancillary equipment to measure the pose, partial or otherwise. This means that the joint angles obtained from the manipulator and knowledge of the type of constraint, are all that is needed to perform the calibration. This concept is applied to the calibration of a six-degree-of-freedom manipulator by connecting its end point to a table by means of a ball bar. The kinematic equations of the manipulator and constraint are developed, and then used to simulate the calibration process in order to determine whether the noise level present in the measurements disrupts the convergence of the process, the effect of measurement noise on the accuracy of identification and the number of experimental observations needed. The acquisition of experimental data is then described, and the results of the identification are discussed. It is concluded that for certain types of kinematic structures, this method of calibration is particularly attractive since it is rapid, simple to perform, and requires very little precision equipment.
Robust Controller for Gas Turbines Based Upon LQG/LTR Design With Self-Tuning Features
Authors: Song Q. , Wilkie J. , Grimble M. J.
Published: March 2008

A feasibility study is described for the design of a self-tuning controller for gas turbines with the multivariable discrete-time robust controller designed using a Linear Quadratic Gaussian/ Loop Transfer Recovery (LQG/LTR) design approach.
Digital Control Design Via Convex Optimization
Authors: Avedon R. E. , Francis B. A.
Published: March 2008

A design method for sampled-data systems is presented incorporating robust control theory and convex optimization techniques. The technique is developed using operator theory applied to the relevant input-output operators for both performance and stability robustness. Numerical algorithms and an example for the SISO case are presented to explore some traditional sampled-data design heuristics.
Decentralized Robust Control of Decomposed Uncertain Interconnected Systems
Authors: Cheng Cheng-Fa , Wang Wen-June , Lin Yu-Ping
Published: March 2008

In this paper, a new design technique of decentralized robust controllers for a class of uncertain interconnected system is provided. The interconnection matrices and the uncertainties of the system are decomposed into a matched and a mismatched portions. Since the matched portion can always be compensated by feedback controls, this new technique can provide local controllers to withstand strong inter-connections and large uncertainties. The relations among local feedback gains, uncertainty bounds, and interconnection strength are established to aid the robust controller design. A practical system with simulation results is given to exemplify the implementation of the controller design technique.
Long Range Predictive Optimal Control Law With Guaranteed Stability for Process Control Applications
Authors: Grimble M. J.
Published: March 2008

The Generalized Predictive Control law has been successfully applied in industrial applications but has limitations on nonminimum phase processes for some of the most obvious choices of cost-functions. The Weighted Predictive Control law proposed here is new and avoids these difficulties while maintaining a similar philosophy. It ensures guaranteed stability when the control weighting tends to zero, even if the system is nonminimum phase. The solution is relatively straightforward and is very suitable for process control applications. The cost-function includes dynamic weighting terms on both output and control signals so that robustness properties can be frequency shaped.
Modification to Overall System Response When Using Narrowband Adaptive Feedforward Control Systems
Authors: Snyder Scott D. , Tanaka Nobuo
Published: March 2008

The influence which a narrowband adaptive feedforward controller, operating in the presence of unreferenced random noise, has upon the frequency response characteristics of the controlled system away from the controller referenced frequency band is investigated. It is found experimentally that the adaptation of the controller weights is responsible for increasing the resonant peaks of the response and introducing new peaks in some instances. This phenomenon is examined analytically, where it is shown that the unreferenced frequency components can propagate through the adaptive algorithm error signal input and exert an influence on the controller output signal spectrum. This phenomenon is found to be most troublesome when there is a response peak near the feedforward system reference frequency. The only remedy for the problem is a reduction in the adaptive algorithm convergence coefficient to a value far below that dictated purely by stability considerations.
Control-Oriented Order Reduction of Finite Element Model
Authors: Yae K. Harold , Inman Daniel J.
Published: March 2008

In the dynamics modeling of a structure, finite element analysis employs reduction techniques, such as Guyan’s reduction, that remove some of the “insignificant” physical coordinates, that is, degrees of freedom at a node point. Despite such reduction, the resultant model is still too large for control design. This warrants further reduction as is frequently done in control design by approximating a large dynamical system with a fewer number of state variables. A problem, however, arises because a model usually undergoes, before being reduced, some form of coordinate transformations that destroy the physical meanings of the states. To correct such a problem, we developed a method that expresses a reduced model in terms of a subset of the original states. The proposed method starts with a dynamic model that is originated and reduced in finite element analysis. The model is then converted to a state-space form, and reduced further by the internal balancing method. At this stage, being in the balanced coordinate system, the states in the reduced model have no apparent resemblance to those of the original model. Through another coordinate transformation that is developed in this paper, however, this reduced model is expressed by a subset of the original states, so that the states in the reduced model can be related to the degrees of freedom of the nodes in the original finite element model.
Synthesis of Multivariable Controller With Plant Test Data
Authors: Chan Jenq-Tzong H.
Published: March 2008

A method to synthesize decoupled multivariable control system from a batch of plant test data is introduced. The method is applicable when the system has more inputs than outputs and is open-loop stable. An advantage of this method is that explicit identification of an open-loop system model is not required for controller synthesis.
Concurrent Design Optimization of Mechanical Structure and Control for High Speed Robots
Authors: Park Jahng-Hyon , Asada Haruhiko
Published: March 2008

A concurrent design method of mechanical structure and control is developed for two-link high speed robots. An integrated design approach to achieve high speed positioning is explored, in which comprehensive design parameters describing arm link geometry, actuator locations, and feedback gains are optimized with respect to the settling time of the system. First, a two-link, nonrigid arm is analyzed and a simple dynamic model representing rapid positioning processes is obtained. Optimal feedback gains minimizing the settling time are obtained as functions of structural parameters involved in the dynamic model. The structural parameters are then optimized using a nonlinear programming technique in order to obtain an overall optimal performance. Based on the optimal design, a prototype high speed robot is built and tested. The resultant arm design shows an outstanding performance, which is otherwise unattainable if the structure and control are designed separately.
A State-Space Model for Monitoring Thermally Induced Preload in Anti-Friction Spindle Bearings of High-Speed Machine Tools
Authors: Stein J. L. , Tu J. F.
Published: March 2008

Catastrophic and premature bearing failure caused by excessive thermally induced bearing preload is a major design problem for spindle bearings of high-speed machine tools. Due to a lack of a low cost and easy to maintain on-line preload measuring technique, the traditional solution is to limit the maximum spindle speed and the initial bearing preload. This solution is incompatible with the need to increase machining productivity, which requires increasing the spindle speed, and to increase product quality (surface finish, dimensional accuracy), which requires increasing (or at least not decreasing) the preload to keep the spindle system stiff. This paper proposes a dynamic mathematical model of the spindle system, which can be used as part of a model-based monitoring system for estimating the spindle bearing preload. The model is derived from physical laws of heat transfer and thermoelasticity and represents the transient preload behavior induced by uneven thermal expansions within a bearing. The state-space structure of the model provides for efficient sensor selection and easy conversion into a state observer for on-line preload estimation. The state variables defined in the model are the temperatures of the outer ring/housing, the rolling elements, and the inner ring, while the induced preload is an algebraic function of these states. The model, which is successfully validated for two typical configurations of high speed spindle assemblies, provides a tool for understanding the basic mechanics of induced preload as a function of initial preload, spindle speed, and housing cooling conditions. Most importantly, the model meets the requirements as the basis of a preload observer developed by the authors. While the observer is not presented in this paper, basic issues related to its development are discussed.
Modeling and Control of Timeshared and Scanned Torch Welding
Authors: Doumanidis C. C.
Published: March 2008

Optimization of the weld quality and productivity requires in-process identification and simultaneous regulation of several thermal characteristics of the joint. Since in traditional single-torch welding only a few process variables can be modulated in real-time, multiple source configurations are implemented by a rapidly reciprocated (timeshared) GTAW torch to obtain decoupled control of the weld geometry, structure and properties. Further, to widen the range of achievable weld features, a scanning motion of the torch on the entire part surface generates the necessary heat distribution for any specified thermal field in the weld, which is observed through surface temperature measurements. Analytical, numerical, and experimental thermal modeling techniques are employed for the design of multivariable adaptive and distributed-parameter controllers, applied to girth and flange welding simulations, and tested in seam pipe welding experiments, for rejection of process disturbances and for weld quality regulation performance.
Application of Approximate I/O Linearization to Aircraft Flight Control
Authors: Lee A. W. , Hedrick J. K.
Published: March 2008

This paper examines the performance enhancement of a statically unstable aircraft subject to the input and state constraints. Under control saturation, i/o linearizability is destroyed and the state trajectories may not be attracted to the sliding surface. If the reference signals are sufficiently large and the zero-dynamics is lightly damped, the i/o linearizing control may become unreasonably large in magnitude, making the closed-loop system susceptible to the damaging effects of control saturation. In addition to performance degradations such as increased tracking errors, control saturation can drive the closed-loop system to instability. In this paper, a new design method called approximate i/o linearization is presented to enhance the performance of the SISO longitudinal flight control problem under saturation. The new approximate i/o linearization law is obtained by solving a pointwise minimization problem. The function to be minimized consists of a surface whose relative degree is one, its derivative, and weighted square of the input u. The advantages of the approximate i/o linearization is that the adverse effects of control saturation can be minimized by properly selecting the weight on the usage of the control. The only requirement for the new technique is that the original plant be locally i/o linearizable. Thus approximate i/o linearization does not impose additional strict requirements on the plant. In the remaining sections of the paper, stability and bounded tracking properties of the approximate i/o linearization are proven. Finally, a longitudinal flight control problem is used to demonstrate the application of approximate i/o linearization.
User-Adaptable Comfort Control for HVAC Systems
Authors: Federspiel Clifford C. , Asada Haruhiko
Published: March 2008

This paper describes a new approach to the control of heating, ventilating, and air-conditioning (HVAC) systems. The fundamental concept of the new approach is that the controller learns to predict the actual thermal sensation of the specific occupant by tuning parameters of a model of the occupant’s thermal sensation. The parameters are adjusted with respect to thermal sensation ratings acquired from the specific occupant and measurements of physical variables that affect thermal sensation so that with time the model accurately reflects the thermal sensation of the specific occupant. From a lumped-parameter model of a singleroom enclosure, it is shown that the stability of the nominal system can be maintained by utilizing a priori information about the parameters of the thermal sensation model. The method is implemented on a ductless, split-system heat pump. Experiments using human subjects verify the feasibility of the method.
Specular Reflection Probability in the Certainty Grid Representation
Authors: Lim Jong Hwan , Cho Dong Woo
Published: March 2008

A new method for solving the specular reflection problem of sonar systems has been developed and implemented. This method, the specular reflection probability method, permits the robot to construct a high quality probability map of an environment composed of specular surfaces. The method employs two parameters, the range confidence factor (RCF) and orientation probability. The RCF is the measure of confidence in the returning range from a sensor under reflective environment, and the factor will have low value for long range information and vice versa. Orientation probability represents the surface orientation of an object. Bayesian reasoning is used to update the orientation probability from the range readings of the sensor. The usefulness of this approach is illustrated with the results produced by our mobile robot equipped with ultrasonic sensors.
Impact of Flexibility on the Clock Controller of the Galileo Spacecraft
Authors: Eke F. O. , Macala G. A. , Man G. K.
Published: March 2008

This paper presents a study of the effects of structural flexibility on one of the control loops that constitute the Attitude and Articulation Control Subsystem of the Galileo Spacecraft. Both stability analysis and time domain simulation studies are discussed. Results obtained indicate that the control loop of interest—the Clock Controller—will interact stably with the spacecraft structure as long as the spacecraft scan platform boresight points at least 30 deg away from the spacecraft spin axis (poles). Flexibility effects become more and more pronounced with proximity of the bore-sight to the poles as several structural modes become excitable to resonance.
Direct Adaptive Rapid Tracking of Short Complex Trajectories
Authors: Ma C. C. H.
Published: March 2008

A direct adaptive rapid tracking methodology for tracking complex trajectories in short-duration, linear, possibly slowly varying, and/or imprecisely known, industrial processes is proposed. The rapid tracking is accomplished by injecting a supplemental control signal to the input of the plant. The direct adaptive control scheme adapts the stabilizing controller to that which will yield fast convergence of the supplemental control learning process. The complete controlled system is capable of tracking closely very complex short reference trajectories, even in the presence of plant input limitations (saturation).
Dynamic Recurrent Neural Networks for Control of Unknown Nonlinear Systems
Authors: Jin Liang , Nikiforuk Peter N. , Gupta Madan M.
Published: March 2008

A scheme of dynamic recurrent neural networks (DRNNs) is discussed in this paper, which provides the potential for the learning and control of a general class of unknown discrete-time nonlinear systems which are treated as “black boxes” with multi-inputs and multi-outputs (MIMO). A model of the DRNNs is described by a set of nonlinear difference equations, and a suitable analysis for the input-output dynamics of the model is performed to obtain the inverse dynamics. The ability of a DRNN structure to model arbitrary dynamic nonlinear systems is incorporated to approximate the unknown nonlinear input-output relationship using a dynamic back propagation (DBP) learning algorithm. An equivalent control concept is introduced to develop a model based learning control architecture with simultaneous on-line identification and control for unknown nonlinear plants. The potentials of the proposed methods are demonstrated by simulation results.