bluuebunny/crossref_metadata_2025 huggingface dataset:
Similarity and Invariance in Scaled Bilateral Telemanipulation
Authors: Goldfarb Michael
Published: February 2008

This paper addresses the issue of dynamic similarity and intensive property invariance in scaled bilateral manipulation, and offers a design methodology based on these considerations. The methodology incorporates dimensional analysis techniques to define a set of necessary and sufficient conditions to preserve the dynamic similarity of any physical environment. These techniques are utilized to demonstrate that any combination of kinematic and force scaling in a bilateral manipulator control structure will preserve the dynamic similarity of any physical environment. Any combination of kinematic and force scaling, however, will not in general maintain intensive property invariance between the original and scaled physical environments, and thus will result in lost information. As such, the dimensional analysis methods are further utilized to form the basis of a constrained optimization problem that enables selection of a force scaling factor that minimizes the intensive distortion of the environment. The proposed formulation is applicable to any physical environment, including those that are nonlinear and contain multiple degrees of freedom. Further, the formulation does not require an exact environmental model, provided the parameters that influence the environment are known. The proposed techniques are particularly relevant to bilateral manipulation of a microscopic environment (i.e., macro-micro bilateral manipulation), since such environments are difficult to model exactly and are largely influenced by nonlinear effects.
The Algorithms of the Cross-Coupled Precompensation Method for Generating the Involute-Type Scrolls
Authors: Chin Jih-Hua , Lin Hu-Wai
Published: February 2008

Cross-coupled precompensation method (CCPM) has been proven efficient in tracking nonlinear spatial curves. It requires a path generating algorithm derived from the mathematical equation of the target curve. This paper discussed the time base transform of target curve from a parametric form. The time based path generating algorithm for the extended involute scroll was then proposed. A comparison among three kinds of tool path generating algorithms were performed. The proposed path algorithms, along with other two algorithms, were implemented and tracked by four different control schemes, US (uncoupled-unprecompensated system), CCS (cross-coupled system), PPM (path precompensation method), and cross-coupled precompensation method (CCPM). The proposed path algorithm for extended involute scroll provided the best accuracy. The proposed algorithm tracked by CCPM achieved the most precise profile especially at high feedrates.
Generalized Optimal Zero Phase Error Tracking Controller Design
Authors: Yamada Manabu , Funahashi Yasuyuki , Riadh Zaier
Published: February 2008

This paper presents a simple design method of discrete-time feedforward controllers that provide the overall transfer function with the following frequency characteristics. (i) The phase is equal to zero for all frequencies. (ii) The gain is equal to one at given frequencies. (iii) The error between the gain and unity for a given frequency range is minimized under given preview steps. The contributions of this paper are as follows. First, a new approach based on the spectral factorization is proposed and the class of all controllers satisfying the above conditions (i) and (ii) is parametrized using the solution of a Diophantine equation, i.e., the controller is obtained in an explicit form. With this explicit parametrization, the optimal feedforward controller is obtained by an ordinary least square method. The design method proposed in this paper is simple and straightforward, whereas the design method in previous result requires the solution of an optimization problem with troublesome inequality constraint and involves trial and error. Secondly, the frequencies at which the gain is made equal to unity can be chosen arbitrarily, while, in previous result, the frequency is restricted to zero. Finally, the effectiveness of the proposed controller is demonstrated by simulation.
Optimal Design of a Vibration Isolation Mount Using Physical Programming
Authors: Wilson Bruce H. , Erin Cem , Messac Achille
Published: February 2008

Vibration isolation tables find application in diverse production and research environments. The structure of a table is such that a designer is forced to compromise among design metrics such as transmissibility, force-disturbance rejection, and controller effort. As both structural and controller parameters impact these design metrics, we chose to perform simultaneous control-structure integrated design (CSID) to optimize the overall performance. We employed a new model that enhances physical insight and used physical programming as the optimization framework. We explored several design scenarios and effectively uncovered the appropriate compromises among the competing objectives. The results highlight the utility of the new model in this design context and the usefulness of physical programming in performing simultaneous CSID.
On the Limitations of Force Tracking Control for Hydraulic Servosystems
Authors: Alleyne Andrew , Liu Rui
Published: February 2008

This paper presents analysis of a particular force tracking control problem for rectilinear hydraulic actuators governed by a servovalve. It presents no new theory, but rather uses a revealing model reduction insight coupled with Classical analysis to explain a physical phenomenon. As such, this work is an attempt to explain why a seemingly innocuous problem is more subtle than initially believed. A motivation for this problem is given along with prior attempts at a simple solution. It is shown that simple controller solutions are quite adequate for other types of control objectives such as force regulation or position tracking. However, most simple solution methods are shown to be inadequate for force tracking due to fundamental limitations of the problem formulation. Due to an inherent feedback mechanism, the poles of the plant being forced by the hydraulic actuator become zeros of the open loop force transfer function. Therefore, more advanced control algorithms are shown to be a necessity rather than a luxury.
Dynamic Modeling of Capsule Separator for Control of Hydraulic Capsule Pipelines
Authors: Du Hongliu , Nair Satish S.
Published: February 2008

Hydraulic capsule pipelines concepts are novel as compared to existing commercial pipeline systems. The complexity of such novel systems places greater demands on sensing, automation, and control strategy design for such systems as compared to existing commercial pipeline systems. These issues, as well as hydraulic design automation and control strategies, are reported. A novel capsule separator design has also been proposed to ensure reliable functioning of ‘booster’ stations for such pipelines. Detailed dynamic modeling of the proposed capsule separator is performed for generating design and control guidelines. Validation of the overall hydraulic capsule pipeline design and control, and limited validation of the proposed capsule separator subsystem, are provided using a prototype hardware computer controlled pipeline model.
Dynamics of Systems That Include Wings in Autorotation
Authors: Seter D. , Rosen A.
Published: February 2008

A general multibody model, appropriate for investigating the autorotation of various systems of rigid bodies, is presented. Using the Newton-Euler approach, a generic modular matrix form of the equations of motion is obtained. The general nature of this detailed, nonlinear model allows the description of a large variety of autorotating systems. The calculations of the aerodynamic loads that act on the blades include the use of empirical data combined with an extended blade element/momentum analysis. The model is first validated by comparing its results with analytical results for simple cases. Then the use of the model to investigate the autorotation of a rotor model in a wind tunnel is presented. Good agreement between the experimental and theoretical results is shown.
Performance Improvement of Industrial Robot Trajectory Tracking Using Adaptive-Learning Scheme
Authors: Sun Dong , Mills James K.
Published: February 2008

More and more industrial robot operations demand high-accuracy trajectory performance which may not be achievable by using conventional PID control. This paper describes a new adaptive control method with a learning ability in the repetitive tasks, called the Adaptive-Learning (A-L) scheme. The method is based on the proposed theory of two operational modes: the single operational mode and the repetitive operational mode. In the single operational mode, the control is an adaptive control with a new parameter adaptation law using information from the previous trials. In the repetitive operational mode, the control is a model-based iterative learning control. The advantage of the A-L scheme lies in the ability to guarantee convergence in both modes. Theoretical analysis and experimental evaluation on a commercial robot demonstrate the effectiveness of the A-L scheme in controlling an industrial robot manipulator.
Joint Impedance Pneumatic Control for Multilink Systems
Authors: Gorce P. , Guihard M.
Published: February 2008

In this paper, we propose a general controller for complex tasks such as coordination or manipulation for grasping systems or dynamic gaits for legged robots. Moreover, this controller is adapted to pneumatic actuated structures. The aim is then to ensure a dynamic tracking of position and force for systems which may interact with the environment or cooperate with each other. For that, we propose a nonlinear controller based on a computed torque method taking into account the actuator and the mechanical models. The originality lays in the consideration of impedance behaviour at each joint during free and constrained tasks. It leads to continuous control laws between contact and non-contact phases. The asymptotic stability is ensured using Popov criteria. The application proposed is the control of one pneumatic leg of a biped robot. We present a dynamic model of the leg and chosen trajectories. Simulation results of this new controller are presented, leading to a good behaviour of the leg during a whole walking cycle at relatively high velocities.
Suboptimality of a Decentralized Feedback Control Law
Authors: Boukas El Kebi´r , Swierniak A. , Yang H.
Published: February 2008

In this note, a new estimating method for the upper bound of the cost of the uncertain linear system used by Trinh and Aldeen (1993) is proposed. We have also estimated the absolute cost loss and relative cost loss of this kind of optimization problem. To show the usefulness of our results a numerical example has been developed.
Sliding Mode Control of a Hydraulic Industrial Robot
Authors: Habibi S. R.
Published: February 2008

A general mathematical function for hydraulic actuators is reviewed in this paper. This model is used for the application of Computed Torque and Variable Structure controllers to a hydraulic industrial robot, the Workmaster, formerly manufactured by Thorn EMI Robotics. The model based controllers are examined to demonstrate the effectiveness of feedback and feedforward compensation in hydraulic systems. It is shown that a large performance improvement is obtained through feedforward and feedback compensation. A sliding mode component is added to model based compensation in order to improve the system’s performance by providing additional control action when there are modeling inaccuracies resulting from nonlinear friction effects.
Robotic Force Control Using Virtual Trajectory Generation
Authors: Fielding Timothy S. , Mills James K.
Published: February 2008

A control method is introduced to permit the retrofit of a large class of commercially available industrial robots with a contact force control capability. In this control algorithm, the outer force loop modifies the desired position input trajectory by solving two sets of differential equations as initial value problems. Experimental results, obtained on a CRS Robotics Corporation A460 six degree of freedom industrial robot, are presented which demonstrate the effectiveness of the proposed approach.
A Fast and Robust Algorithm for General Inequality/Equality Constrained Minimum-Time Problems
Authors: Driessen B. J. , Sadegh N. , Parker G. G. , Eisler G. R.
Published: February 2008

This work has developed a new robust and reliable O(N) algorithm for solving general inequality/equality constrained minimum-time problems. To our knowledge, no one has ever applied an O(N) algorithm for solving such minimum time problems. Moreover, the algorithm developed here is new and unique and does not suffer the inevitable ill-conditioning problems that pre-existing O(N) methods for inequality-constrained problems do. Herein we demonstrate the new algorithm by solving several cases of a tip path constrained three-link redundant robotic arm problem with torque bounds and joint angle bounds. Results are consistent with Pontryagin’s Maximum Principle. We include a speed/robustness/complexity comparison with a sequential quadratic programming (SQP) code. Here, the O(N) complexity and the significant speed, robustness, and complexity improvements over an SQP code are demonstrated. These numerical results are complemented with a rigorous theoretical convergence proof of the new O(N) algorithm.
Automatic Loop-Shaping of QFT Controllers Via Linear Programming
Authors: Chait Yossi , Chen Qian , Hollot C. V.
Published: February 2008

In this paper we focus on the following loop-shaping problem: Given a nominal plant and QFT bounds, synthesize a controller that achieves closed-loop stability, satisfies the QFT bounds and has minimum high-frequency gain. The usual approach to this problem involves loop shaping in the frequency domain by manipulating the poles and zeroes of the nominal loop transfer function. This process now aided by recently-developed computer-aided design tools, proceeds by trial and error, and its success often depends heavily on the experience of the loop-shaper. Thus, for the novice and first-time QFT users, there is a genuine need for an automatic loop-shaping tool to generate a first-cut solution. Clearly, such an automatic process must involve some sort of optimization, and, while recent results on convex optimization have found fruitful applications in other areas of control design, their immediate usage here is precluded by the inherent nonconvexity of QFT bounds. Alternatively, these QFT bounds can be over-bounded by convex sets, as done in some recent approaches to automatic loop-shaping, but this conservatism can have a strong and adverse effect on meeting the original design specifications. With this in mind, we approach the automatic loop-shaping problem by first stating conditions under which QFT bounds can be dealt with in a non-conservative fashion using linear inequalities. We will argue that for a first-cut design, these conditions are often satisfied in the most critical frequencies of loop-shaping and are violated in frequency bands where approximation leads to negligible conservatism in the control design. These results immediately lead to an automated loop-shaping algorithm involving only linear programming techniques, which we illustrate via an example.
Moving Force Identification—A Frequency and Time Domains Analysis
Authors: Law S. S. , Chan Tommy H. T. , Zeng Q. H.
Published: February 2008

This paper addresses the problem of identifying a system of forces from vehicle crossing a guideway using only the vibration responses caused by the forces as the input without knowledge of the vehicle characteristics. The vehicle is modeled as a single axle and two-axle loads with fixed axle spacing moving on a simply supported beam with viscous damping. The equations of motion of the beam are obtained through modal coordinate transformation, and the resulting set of equations relating the Fourier transforms of the responses and the moving forces are converted into time domain by a new method proposed by the authors. Correctness of the identified forces are checked by the correlation between the measured responses and the responses reconstructed with the identified forces moving on the beam. Experimental result shows that the method is effective to give good correlation when both measured bending moment and acceleration are used, and it is faster and it gives more accurate estimate of the total mass of the vehicle than an existing method.
Explicit Energy Storage Fields and Their Application to Structural Property Inspection of Physical Systems
Authors: Huang Shih-Ying , Youcef-Toumi Kamal
Published: February 2008

Bond graph models provide very useful insights into the structure of dynamic systems. One major advantage of using these models is the clear representation of constraints and independent state variables. However, certain over-constrained structures are not dealt with adequately with this approach. Such a situation arises when several energy storage elements of the same type are directly coupled by a junction structure. In these models, although the representations are legitimate in terms of physical meaning, the resultant excess states cause pitfalls in the inspection of system properties. This paper proposes the use of explicit fields to eliminate such ambiguities. It was found that the excess states caused by the topological structures can be totally eliminated by explicit fields. The excess states caused by the imposed sources then can be identified properly. Several applications are presented to illustrate the use of explicit fields.
An Optimal Differential Sensitivity Approach to Pole Assignment for Structurally Perturbed Systems
Authors: Tam Hei Ka , Lam James
Published: February 2008

This paper introduces a mathematical formula for calculating the eigenvalue differential sensitivities of the closed-loop state matrix with respect to a disturbance matrix when the closed-loop system is subjected to an additive structured perturbation. The robust pole assignment problem is then formulated as an optimization task in which the differential sensitivities of the closed-loop poles are minimized. The case of “multi-perturbations” can be considered naturally in our problem formulation. The gradient of the objective function to be minimized is then derived which permits the minimization to be proceeded effectively. Numerical examples are then employed to illustrate the design technique.
Passive and Active Closures by Constraining Mechanisms
Authors: Yoshikawa Tsuneo
Published: February 2008

This paper provides a unified theoretical framework for analytical characterization of grasping and manipulation capability of robotic grippers and hands as well as fixing capability of fixtures and vises. The concept of passive closure and active closure for general constraining mechanisms consisting of fixed and/or articulated constraining limbs is introduced. These concepts are useful for explicitly distinguishing the two kinds of capabilities of the constraining mechanism: Passive closure represents the ability of fixing devices and active closure represents the ability of manipulating devices. Passive closure is further classified into passive form closure and passive force closure. Passive form closure is essentially the same as Reuleaux’s classical form closure and passive force closure is a substantial generalization of classical force closure to the case where articulated constraining limbs exist. Conditions for these closures to hold are studied. After a brief review of conditions for passive form closure, several conditions for passive force closure are given. One outcome is that, under the assumption that the contact points are frictionless and the active contact points are independent, for the existence of passive force closure there must be at least six (three) fixed contact points and one active contact point in the case of three-dimensional (two-dimensional, respectively) space. Finally, a necessary and sufficient condition for active closure is given for the case of frictional point contacts by constraining limbs with enough degrees-of-freedom. This condition consists of a general positioning condition of contact points and the existence condition of nonzero internal force. This condition has a quite natural physical interpretation.
Naturally-Transitioning Rate-to-Force Control in Free and Constrained Motion
Authors: Williams Robert L. , Henry Jason M. , Murphy Mark A. , Repperger Daniel W.
Published: February 2008

The Naturally-Transitioning Rate-to-Force Controller (NTRFC) is presented for teleoperation of manipulators. Our goal is to provide a single controller which handles free motion, constrained motion, and the transition in-between without any artificial changes. In free motion the displacement of the master device (via the human operator’s hand) is proportional to the commanded Cartesian rate of the manipulator. In contact, the displacement of the human operator’s hand is proportional to the wrench (force/moment) exerted on the environment by the manipulator. The transition between free rate motion and applied-wrench contact with the environment requires no changes in control mode or gains and hence is termed natural. Furthermore, in contact, if the master enables force reflection, the wrench of the human operator’s hand exerted on the master is proportional to the wrench exerted on the environment by the manipulator. This article demonstrates the NTRFC concept via a simple 1-dof model and then discusses experimental implementation and results from a Merlin manipulator teleoperated via the force-reflecting PHANToM interface.
Input Shaping Design for Multi-Input Flexible Systems
Authors: Lim Sungyung , Stevens Homer D. , How Jonathan P.
Published: February 2008

This paper investigates a new design technique of input shaping filters for multi-input flexible systems using convex optimization synthesis techniques for finite impulse response filters (FIR filters). The objective of the input shaping filter design is to find the minimum length and the minimum number of nonzero impulses of the FIR filter that forces the system to track the reference command without any residual vibration, while satisfying additional performance and control constraints. This multi-objective optimization is solved using a two-step algorithm that sequentially solves two quasi-convex optimization problems. Compared with previously published nonlinear optimization approaches, this new approach does not require a priori knowledge of the forms of input shaping filters and enables much greater flexibility for including additional performance and robustness objectives. Furthermore, this convex-based approach can be applied to multi-input systems. The multiple input shaping filter has been experimentally verified on the Stanford University Two-Link Flexible Manipulator.
Combined Discrete-Distributed Control of a Single-Link Flexible Manipulator Using a Lyapunov Approach
Authors: Gu Min , Asokanthan Samuel F.
Published: February 2008

This paper presents a development of hybrid control strategies for a single-link flexible manipulator. The control system consists of two actuators; a DC servo motor at the joint and a distributed piezoelectric film actuator bonded to the surfaces of the flexible link. Equations of motion considering two control inputs were developed using the generalized Hamilton’s principle. A feedback control law has been developed based on Lyapunov’s direct method and global stability of closed-loop system is guaranteed. A loop-closure technique was introduced to simplify the design procedure for choosing the feedback gains. Simulation and the experimental results were found to be in good agreement and performance improvement obtained using the hybrid control strategy has been demonstrated.
Constant Spacing Strategies for Platooning in Automated Highway Systems
Authors: Swaroop D. , Hedrick J. K.
Published: February 2008

An important aspect of an Automated Highway System is automatic vehicle following. Automatic Vehicle follower systems must address the problem of string stability, i.e., the problem of spacing error propagation, and in some cases, amplification upstream from one vehicle to another, due to some disturbance at the head of the platoon. An automatic vehicle following controller design that is (asymptotically) stable for one vehicle following another is not necessarily (asymptotically) stable for a string of vehicles. The dynamic coupling between vehicles in such close-formation platoons is a function of the available information (communicated as well as sensed), decentralized feedback control laws and the vehicle spacing policy in use. In the first half of this paper, we develop a framework for establishing conditions for stability of the string in the presence of such dynamic interactions. We then develop a metric for analyzing the performance of a platoon resulting from different vehicle following control algorithms. This metric is the guaranteed rate of attenuation/non-amplification of spacing errors from one vehicle to another. In the latter half of this paper, we outline and analyze various constant spacing vehicle follower algorithms. All these algorithms are analyzed for sensing/actuation lags.
Theory and Applications of the Robust Cross-Coupled Control Design
Authors: Yeh Syh-Shiuh , Hsu Pau-Lo
Published: February 2008

The cross-coupled control (CCC) has been recognized as an efficient motion controller that reduces contouring errors, but theoretical analysis of it is lacking, and there is no systematic design approach for obtaining a CCC system with guaranteed control performance. Consequently, the compensators C in CCC are commonly implemented in a PID structure and their contouring accuracy is usually degraded in real applications under different operating conditions. In an attempt to overcome the CCC design limitations described above, this paper introduces a robust CCC design based on a novel formulation: the contouring error transfer function (CETF), leading to an equivalent formulation as in the feedback control design problem. Then, methods in robust control design can be readily employed to achieve robust CCC with specified stability margins and guaranteed contouring performance. Furthermore, the proposed design has been verified as being internally stable. All provided experimental results indicate that the proposed robust CCC design consistently renders satisfactory contouring accuracy under different operating conditions.
Friction Forces Within the Cylinder Bores of Swash-Plate Type Axial-Piston Pumps and Motors
Authors: Manring Noah D.
Published: February 2008

In this research, the friction within the cylinder bore of a swash-plate type axial-piston machine is examined. Unlike previous research, this work develops a mathematical model for the friction based upon lubricating conditions which are described by the well-known Stribeck curve. Furthermore, a test device is built for measuring the frictional characteristics during low pressure and low speed operation and these results are compared with the mathematical model. For high pressure and high speed considerations, a numerical investigation based upon the model is conducted and it is shown that the friction associated with a pumping piston is greater than the friction associated with a motoring piston. It is also shown that increased piston speeds usually reduce the friction within the cylinder bore; however, a “cross-over” condition may exist where the increased speed will actually increase the friction as a result of increased fluid shear. Furthermore, it is shown that speed changes have a more significant impact on motoring pistons as opposed to pumping pistons due to a difference in the location of hydrodynamic lubrication within the cylinder bore. It is noted that this difference exits due to the bore geometry and the direction of piston travel.
A Random Approach to Time-Optimal Control
Authors: Kulczycki Piotr
Published: February 2008

This paper concerns the time-optimal control for objects described by a random differential inclusion with discontinous right-hand side, representing the second law of Newtonian mechanics and taking into account a complex model of resistance to motion. Such a task has broad technical applications, especially in robotics. By generalizing the concept of the classic switching curve to the switching region, it is possible to construct in practice a range of convenient suboptimal control structures that provide many advantages, especially in respect to robustness.
A Simplified Robust Circle Criterion Using the Sensitivity-Based Quantitative Feedback Theory Formulation
Authors: Thompson David F.
Published: February 2008

The circle criterion provides a sufficient condition for global asymptotic stability for a specific class of nonlinear systems, those consisting of the feedback interconnection of a single-input, single-output linear dynamic system and a static, sector-hounded nonlinearity. Previous authors (Wang et al, 1990) have noted the similarity between the graphical circle criterion and design bounds in the complex plane stemming from the Quantitative Feedback Theory (QFT) design methodology. The QFT formulation has specific advantages from the standpoint of controller synthesis. However, the aforementioned approach requires that plant uncertainty sets (i.e., “templates”) be manipulated in the complex plane. Recently, a modified formulation for the QFT linear robust performance and robust stability problem has been put forward in terms of sensitivity function bounds. This formulation admits a parametric inequality which is quadratic in the open loop transfer function magnitude, resulting in a computational simplification over the template-based approach. In addition, the methodology admits mixed parametric and nonparametric plant models. The disk inequality which results represents a much closer analog of the circle criterion, requiring only scaling and a real axis shift. This observation is developed in this paper, and the methodology is demonstrated in this paper via feedback design and parametric analysis of a quarter-car active suspension model with a sector nonlinearity.
Design and Implementation of a Robust Controller for a Free Gyro-Stabilized Mirror System
Authors: Siew Boon C. , Chen Ben M. , Lee Tong H.
Published: February 2008

In this paper, we consider the problem of designing a robust controller for a multivariable servomechanism of a free gyro-stabilized mirror system where there exists cross-coupling between the axes. The nonlinear dynamics of the system are first linearized and reformulated into an H∞ problem. A reduced order output feedback controller is then designed using the asymptotic time-scale and eigenstructure assignment (ATEA) technique. The overall design has been implemented using a personal computer with C++ and tested on the actual gyro-stabilized mirror system. Our simulation and implementation results show that the design is very successful.
The Design of Quality Engineered Control Systems
Authors: Nwokah Osita D. I. , Happawana Gemunu S. , Afolabi Dare´
Published: February 2008

Every optimization based engineering design produces a performance metric which as a function of the tolerance parameters, is structurally stable but not generic. This can lead to a severe loss of performance (catastrophes) under a smooth change in the tolerance parameters. This paper gives an exposition of how norm based optimal control methods naturally lead to performance catastrophes, as well as an alternative systematic loop shaping design methodology which corrects the problem.
Preview-Based Stable-Inversion for Output Tracking of Linear Systems
Authors: Zou Qingze , Devasia Santosh
Published: February 2008

Stable Inversion techniques can be used to achieve high-accuracy output tracking. However, for nonminimum phase systems, the inverse is noncausal—hence the inverse has to be precomputed using a prespecified desired-output trajectory. This requirement for prespecification of the desired output restricts the use of inversion-based approaches to trajectory planning problems (for nonminimum phase systems). In the present article, it is shown that preview information of the desired output can be used to achieve online inversion-based output-tracking of linear systems. The amount of preview-time needed is quantified in terms of the tracking error and the internal dynamics of the system (zeros of the system). The methodology is applied to the online output tracking of a flexible structure and experimental results are presented.
Joint Air-Fuel Ratio and Torque Regulation Using Secondary Cylinder Air Flow Actuators
Authors: Stefanopoulou A. G. , Cook J. A. , Grizzle J. W. , Freudenberg J. S.
Published: February 2008

Actuation schemes exist that permit the joint management of air and fuel flow into the cylinders of a spark ignition engine. With the exception of drive by wire systems, to-date, the transient control aspects of these schemes, collectively refered to here as secondary cylinder air flow actuators, has not received any attention from the control community. This paper takes a first step in the analysis of the simultaneous dynamic control of air fuel ratio and torque response using secondary actuators placed before the intake ports of the cylinders, when used in combination with standard fuel injectors and primary throttle regulated by the driver. The emphasis is on basic issues of designing a feedforward scheme to enhance actuator authority for feedback control, and the fundamental multivariable nature of the feedback problem. Enhanced transient air-to-fuel ratio performance improvement is shown to be possible without sacrificing engine torque response with respect to a conventional engine. In addition, this is achieved with overall higher manifold pressure, offering the possibility of reduced pumping losses in the engine, depending on the actual actuation scheme employed.
Adaptive Sinusoidal Disturbance Rejection in Linear Discrete-Time Systems—Part I: Theory
Authors: Ben Amara Foued , Kabamba Pierre T. , Ulsoy A. Galip
Published: February 2008

An adaptive regulation approach against disturbances consisting of linear combinations of sinusoids with unknown and/or time varying amplitudes, frequencies, and phases for SISO LTI discrete-time systems is considered. The new regulation approach proposed is based on constructing a set of stabilizing controllers using the Youla parametrization of stabilizing controllers and adjusting the Youla parameter to achieve asymptotic disturbance rejection. Three adaptive regulator design algorithms are presented and their convergence properties analyzed. Conditions under which the on-line algorithms yield an asymptotic controller that achieves regulation are presented. Conditions both for the case where the disturbance input properties are constant but unknown and for the case where they are unknown and time varying are given. In the case of error feedback, the on-line controller construction amounts to an adaptive implementation of the Internal Model Principle. The performance of the adaptation algorithms is illustrated through a simulation example. A companion paper [4] describes the implementation and evaluation of the algorithms for the problem of noise cancellation in an acoustic duct.
An Iterative Learning Control for Uncertain Systems Using Structured Singular Value
Authors: Doh Tae-Yong , Moon Jung-Ho , Chung Myung Jin
Published: February 2008

To deal with an iterative learning control (ILC) system with plant uncertainty, a set of new terms related with robust convergence is first defined. This paper proposes a sufficient condition for not only robust convergence but also robust stability of ILC for uncertain linear systems, including plant uncertainty. Thus, to find a new condition unrelated to the uncertainty, we first separate it into a known part and uncertainty one using linear fractional transformations (LFTs). Then, robust convergence and robust stability of an ILC system is determined by structured singular value (μ) of only the known part. Based on the novel condition, a learning controller and a feedback controller are developed at the same time to ensure robust convergence and robust stability of the ILC system under plant uncertainty. Lastly, the feasibility of the proposed convergence condition and design method are confirmed through computer simulation on an one-link flexible arm.
Adaptive Post-Linearization of Dynamic Nonlinear Systems With Artificial Neural Networks
Authors: Rabinowitz M. , Gutt G. M. , Franklin G. F.
Published: February 2008

We have applied tailor-made neural networks to the post-linearization of nonlinear systems containing memory. The problems we address involve tracking systems that contain linear dynamics together with memoryless, nonlinear sensors and amplifiers. In general, the goal is to accurately infer a system’s inputs based only on the system’s outputs, which have been corrupted by nonlinear components. The linearizing neural network is trained to emulate the inverse of the Volterra operator which describes the nonlinear system. In implementation, the network estimates the original input signal from the system’s output sequence. The post-linearizing network architecture is determined from an approximate model of the system to be linearized. The network is trained with test signals that excite the tracking system over its domain of operation and expose much of its nonlinear behavior. Network weights and biases are adjusted using a novel algorithm, batch backpropagation-through-time (BBTT). This paper presents a test case involving a sensor with an input-output relation similar to that of a scaled dc SQUID. The sensor and amplifier nonlinearities are embedded within a fourth-order dynamic system with negative feedback. The problem is generally formulated and we discuss the application of our methodology to a variety of nonlinear sensing and amplification systems.
Decentralized Sliding Mode Control for Large-Scale Time-Delayed Systems With Series Nonlinearities
Authors: Hsu Kou-Cheng
Published: February 2008

This paper presents a robust decentralized sliding mode control for large-scale systems with delays in the interconnection and series nonlinearities in the input. The proposed sliding mode control ensures the global reaching condition of the sliding mode of the composite system. Without using time-delayed interconnection terms in the local control input, the developed local sliding mode controller is really independent of coupling subsystem states. Furthermore, the sliding mode control law is improved from the point of view of control energy conservation.
Feedforward Control of Single-Link Flexible Manipulators by Discrete Model Inversion
Authors: Feliu V. , Rattan K. S.
Published: February 2008

The design of feedforward controllers to control the position of single-link flexible arms is developed in this paper. The objective is to drive the tip position along a commanded trajectory without any oscillations at the tip. The method is based on the well-known dynamics model inversion technique. Since the controllers are implemented on a computer, the dynamic inversion of the single-link flexible arm is studied from a discrete point of view. A general method to obtain a feedforward controller is developed, even in the case when the system transfer function is of nonminimum phase. The method is general in the sense that it removes oscillation in the arm with any number of vibration modes. A method to modify the transfer function of these controllers to improve the robustness is also proposed in this paper. It is shown that the input preshaping scheme developed by Singer and Seering is a special case of this method. The design technique is illustrated with numerical examples and a comparison with the input preshaping method is carried out.
A Two Regime Orifice Flow Formula for Numerical Simulation
Authors: Ellman Asko , Piche´ Robert
Published: February 2008

Because the conventional formula for turbulent orifice flow rate has an infinite derivative when the pressure difference is zero, ODE solvers may fail during numerical simulation of fluid power circuits. To remedy this, a two-regime orifice flow formula is proposed in which an empirical polynomial laminar flow function is used for small pressure differences. The proposed formula has a smooth transition between laminar and turbulent regimes, and its derivative does not have any singularities.
Recurrent Neural Networks for Fault Diagnosis and Severity Assessment of a Screw Compressor
Authors: Li C. James , Fan Yimin
Published: February 2008

This paper describes a method to diagnose the most frequent faults of a screw compressor and assess magnitude of these faults by tracking changes in compressor’s dynamics. To determine the condition of the compressor, a feedforward neural network model is first employed to identify the dynamics of the compressor. A recurrent neural network is then used to classify the model into one of the three conditions including baseline, gaterotor wear and excessive friction. Finally, another recurrent neural network estimates the magnitude of a fault from the model. The method’s ability to generalize was evaluated. Experimental validation of the method was also performed. The results show significant improvement over the previous method which used only feedforward neural networks.
Automatic Model Generation for Modular Reconfigurable Robot Dynamics
Authors: Chen I-Ming , Yang Guilin
Published: February 2008

In control and simulation of a modular robot system, which consists of standardized and interconnected joint and link units, manual derivation of its dynamic model needs tremendous effort because these models change all the time as the robot geometry is altered after module reconfiguration. This paper presents a method to automate the generation of the closed-form equation of motion of a modular robot with arbitrary degrees-of-freedom and geometry. The robot geometry we consider here is branching type without loops. A graph technique, termed kinematic graphs and realized through assembly incidence matrices (AIM) is introduced to represent the module assembly sequence and robot geometry. The formulation of the dynamic model is started with recursive Newton-Euler algorithm. The generalized velocity, acceleration, and forces are expressed in terms of linear operations on se(3), the Lie algebra of the Euclidean group SE(3). Based on the equivalence relationship between the recursive formulation and the closed-form Lagrangian formulation, the accessibility matrix of the kinematic graph of the robot is used to assist the construction of the closed-form equation of motion of a modular robot. This automatic model generation technique can be applied to the control of rapidly reconfigurable robotic workcells and other automation equipment built around modular components that require accurate dynamic models.
A Guidance and Control Algorithm for Scent Tracking Micro-Robotic Vehicle Swarms
Authors: Dohner J. L.
Published: February 2008

Cooperative micro-robotic scent tracking vehicles are designed to collectively “sniff out” locations of high scent concentrations in unknown, geometrically complex environments. These vehicles are programed with guidance and control algorithms that allow inter cooperation among vehicles. In this paper, a cooperative guidance and control algorithm for scent tracking micro-robotic vehicles is presented. This algorithm is comprised of a sensory compensation sub-algorithm using point source cancellation, a guidance sub-algorithm using gradient descent tracking, and a control sub-algorithm using proportional feedback. The concepts of social rank and point source cancellation are new concepts introduced within. Simulation results for cooperative vehicles swarms are given. Limitations are discussed.
A Measure of Stability for Mobile Manipulators With Application to Heavy-Duty Hydraulic Machines
Authors: Ghasempoor A. , Sepehri N.
Published: February 2008

This paper describes the development of a suitable algorithm to compute the potential of tipping-over for vehicles that carry manipulators. The energy method developed by Messuri and Klein (1985) is extended here to quantitatively reflect the effect of forces and moments arising from the manipulation of the implement. The amount of the impact energy that can be sustained by the vehicle without tipping-over, about each edge of potential overturning is computed. First, the instantaneous onset of instability configuration of the machine about the edge is determined by constructing an equilibrium plane. Next, the work done by all acting forces and moments when the machine is virtually brought to this unstable stance from the current state, is calculated. This work is the indication of the proximity of the machine to tipping-over around that edge. The application of this study is directed at industrial mobile machines that carry human-operated hydraulic manipulators. The algorithm is therefore used to study the stability of an excavator based log-loader. Simulation studies clearly show the importance of inertial loads in determining the stability of such machines.
On Disturbance Decoupled Observers for a Class of Bilinear Systems
Authors: Zasadzinski M. , Rafaralahy H. , Mechmeche C. , Darouach M.
Published: February 2008

In this paper, the class of bilinear systems subjected to unknown inputs for which there exists a disturbance decoupled observer with linear error dynamics is characterized. It is shown that the design of this kind of observer is equivalent to the design of a disturbance decoupled observer for a linear system. This result simplifies considerably the observer design compared to those proposed in the literature, and the observer existence conditions can be easily deduced. As a corollary of this result, necessary and sufficient conditions for the existence of disturbance decoupled linear observers for bilinear systems subjected to unknown inputs are derived. This approach is extended to the fault detection of bilinear systems.
P-D Feedback for Decoupling and Pole Assignment of Singular Systems
Authors: Koumboulis F. N. , Mertzios B. G.
Published: February 2008

The problem of reducing a multi input-multi output system to many single input-single output systems, namely the problem of input-output decoupling, is studied for the case of singular systems i.e., for systems described by dynamic and algebraic equations. The problem of input-output decoupling with simultaneous arbitrary pole assignment, via proportional plus derivative (P-D) state feedback, is extensively solved. The general explicit expression of all P-D controllers solving the decoupling problem is determined. The general form of the diagonal elements of the decoupled closed-loop system is proven to be in a form having a fixed numerator polynomial and an arbitrary denominator polynomial. The necessary and sufficient conditions for the solvability of the problem of decoupling with simultaneous asymptotic stabilizability or arbitrary pole assignment are established. Furthermore, the necessary and sufficient conditions for decoupling with simultaneous impulse elimination, as well as the necessary and sufficient conditions for decoupling with arbitrary assignment of the finite and infinite poles of the closed-loop system, are established.
Gain-Bandwidth Optimal Design for the New Formulation Quantitative Feedback Theory
Authors: Thompson David F.
Published: February 2008

Recent work in Quantitative Feedback Theory (QFT) has extended the methodology to include a more mathematically tractable formulation which allows consideration of both parametric and non-parametric uncertainty. An issue that remains largely unsolved is that of constructive existence conditions for optimal QFT controllers. The methodology developed in Thompson and Nwokah (1994) was to build upon the classical Bode analysis approach to loop shaping by defining the structure and parameters of an acceptable initial QFT controller a priori; locally optimal controllers of this structure could then be computed via a constrained nonlinear programming algorithm. The primary purpose of this paper is to extend this methodology to the sensitivity-based, “new formulation” QFT bounds. This technique is demonstrated for the nonminimum-phase problem of Nordgren et al. (1994).