bluuebunny/crossref_metadata_2025 huggingface dataset:
Data Dependent Systems Approach to Modal Analysis Via State Space
Authors: Pandit S. M. , Mehta N. P.
Published: July 2009

The application of the Data Dependent Systems (DDS) methodology is proposed for the modal identification and characterization. Difference equation models derived from sampled free and forced response information are shown to quantitatively define the dynamic properties of the system. A modal decomposition of the DDS models, based on modern linear system theory in the state space format and analysed from the standpoint of theoretical modal analysis, yields the system eigenvalues and eigenvectors, and the parameters of a lumped structural model. The theoretical background is presented in detail; its validity is established by means of a simulation study. Advantages of the DDS approach are discussed. Although the simulation study, and to some extent the terminology, are based on mechanical systems, the method has applications in wider fields, e.g., electromagnetic radiation and scattering.
Control of Stability and the Synchronous Vibration of a Flexible Rotor Supported on Oil-Film Bearings
Authors: Sahinkaya M. N. , Burrows C. R.
Published: July 2009

The relationship between eigenvalue loci for the rotor-bearing systems and the onset of instability due to oil-whirl, is utilized to derive an algorithm to control the onset of instability. Implementation of the algorithm is discussed. It is shown how this can be combined with an open-loop adaptive control strategy to ensure the stability of a flexible rotor and also minimize the synchronous vibration throughout the operational speed range.
Adaptive Kalman Filtering: A Simulation Result
Authors: Sasiadek J. Z. , Wojcik P. J.
Published: July 2009

This paper presents the algorithm for on-line adaptive Kalman filtering of sensor signals with unknown signal to noise ratio. A first order spectrum of a pure signal and white Gaussian measurement noise have been assumed. The results of the performance tests of the algorithm as well as the design methodology of the adaptive filter are given.
An Investigation Into the Compliance of SCARA Robots. Part I: Analytical Model
Authors: ElMaraghy H. A. , Johns B.
Published: July 2009

A special class of robots suited for assembly tasks called SCARA (Selective Compliance Assembly Robot Arm) provides a degree of built-in flexibility due to robot structure. In such robots there are three revolute joints and a prismatic joint. They offer four degrees of freedom consisting of rotation about two vertical and parallel axes at the revolute joints, and translation and rotation about the tool axis. Some models offer additional degrees of freedom at the end effector. Structural compliance can arise due to the stiffness of the robot links, drive system, grippers as well as the assembled parts. The largest effect is due to the drive torsional stiffness followed by the grippers, workpieces and the robot tool link. Knowledge of the inherent flexibility is extremely useful in designing tooling and fixtures, in laying out the assembly work cell according to the amount of compliance available in various regions of the robot work envelope, in guarding against wedging and jamming and in specifying external Remote Centre Compliance devices (RCC) if necessary. In this paper the various sources of compliance built into a SCARA robot system are outlined together with their relative significance. A mathematical model which expresses the end effector deflection as a function of the robot Jacobian and the drive compliance parameters in Cartesian coordinates has been developed. The modified generalized assembly force model developed for the Selective Compliance Assembly Robot Arms (SCARA), used in this investigation, is described. Constraints required to prevent jamming and wedging of parts during assembly are outlined. The application of this compliance model for both rotational and prismatic part insertion is described. The conditions required to obtain true or semi-compliance centres for the SCARA robot end effector are derived and discussed.
An Investigation Into the Compliance of SCARA Robots. Part II: Experimental and Numerical Validation
Authors: ElMaraghy H. A. , Johns B.
Published: July 2009

A model of inherent elastic compliance was developed for general position-controlled SCARA, with conventional joint feedback control, for both rotational and prismatic part insertion (Part I). The developed model was applied to the SKILAM and ADEPT I robots for validation. Experimental procedures and numerical solution methods are described. It was found that the ADEPT I robot employs a coupled control strategy between joints one and two which produces a constant, decoupled end effector compliance. The applicable compliance matrix, in this case, is presented and the experimental results are discussed. The model may be used to develop compliance maps that define the amount of end effector compliance, as a function of the joints compliance, as well as its variation for different robot configurations. This is illustrated using data for the SKILAM SCARA robot. Results are plotted and discussed. The most appropriate robot postures for assembly were found for both rotational and prismatic parts. The conditions necessary to achieve compliance or semicompliance centers with the SKILAM robot were examined. The results and methods demonstrated in these examples may be used to select appropriate robots for given applications. They can also guide robot designers in selecting joint servo-control gains to obtain the desired joints compliance ratio and improve assembly performance.
Robust Controller Design for Robot Manipulators
Authors: Sugie T. , Yoshikawa T. , Ono T.
Published: July 2009

In this paper we give a control method for robot manipulators which takes account of both the command response and the robustness in a systematic way by utilizing two-degree-of-freedom controller configuration. A simulation result is given to show the validity of our method.
Controller Design For Nonlinear Systems Based on Simultaneous Stabilization Theory and Describing Function Models
Authors: Nassirharand A. , Taylor J. H. , Reid K. N.
Published: July 2009

A new systematic and algebraic linear control system design procedure for use with highly nonlinear plants is developed. This procedure is based on simultaneous stabilization theory and sinusoidal-input describing function models of the nonlinear plant, and is presently applicable to single-input single-output, time-invariant, deterministic, stable, and continuous-time systems which are representable in standard state-variable differential equation form. Three software utilities to implement the controller design procedure are also outlined. This method and the associated software is applied to a position control problem of the sort encountered in robotics, and the results are compared with those previously obtained using both linear and nonlinear PID control.
Measurement Signal Selection and a Simultaneous State and Input Observer
Authors: Stein J. L. , Park Y.
Published: July 2009

An observer that can simultaneously identify the state variables and inputs of a linear time-invariant system from outputs (measurements) and their first derivatives is derived. The sufficient conditions for the existence of the observer are also derived. These conditions provide the basis for a procedure to choose the minimum set of measurements necessary to observe the behavior of a system with unknown inputs. The technique can also provide a set of measurement signals that decrease the noise effects on the estimated result. An example is used to illustrate the measurement signal selection procedure. Simulation is used to demonstrate that the observer works well, even in the presence of measurement noise. The measurement signal selection technique can be utilized with other estimation methods such as various deconvolution techniques, which do not provide any criteria for measurement selection. Application of this observer to machine diagnostics is discussed.
Modeling and Experimental Evaluation of Asymmetric Pantograph Dynamics
Authors: Eppinger S. D. , O’Connor D. N. , Seering W. P. , Wormley D. N.
Published: July 2009

High-performance pantograph design requires control of pantograph dynamic performance. Many pantograph dynamic models developed to aid in the design process have employed two degrees of freedom, one for the head mass and one for the frame. In this paper, the applicability of these models to symmetric and asymmetric pantograph designs is reviewed. Two degree-of-freedom models have been shown to be appropriate to represent a number of symmetric pantograph designs. To represent the asymmetric designs considered in this paper, an additional degree of freedom representing frame dynamics has been introduced to yield a three degree-of-freedom nonlinear dynamic performance model. The model has been evaluated with experimental data obtained from laboratory dynamic testing of an asymmetric pantograph.
A Lagrangian Formulation of the Dynamic Model for Flexible Manipulator Systems
Authors: Low K. H. , Vidyasagar M.
Published: July 2009

This paper presents a procedure for deriving dynamic equations for manipulators containing both rigid and flexible links. The equations are derived using Hamilton’s principle, and are nonlinear integro-differential equations. The formulation is based on expressing the kinetic and potential energies of the manipulator system in terms of generalized coordinates. In the case of flexible links, the mass distribution and flexibility are taken into account. The approach is a natural extension of the well-known Lagrangian method for rigid manipulators. Properties of the dynamic matrices, which lead to a less computation, are shown. Boundary-value problems of continuous systems are briefly described. A two-link manipulator with one rigid link and one flexible link is analyzed to illustrate the procedure.
Modeling and Analysis of the Dynamics of a Variable-Displacement Vane-Pump With a Pivoting Cam
Authors: Karmel A. M.
Published: July 2009

Variable-displacement vane-pumps, modulated by a pivoting cam, are used extensively in modern automotive transmissions. This paper presents a study of the dynamic and steady-state characteristics of such pumps. Their dynamics concern issues such as pressure fluctuations due to the dynamics of the internal mechanism and transient response-time. Their steady-state characteristics concern limits on the operating envelope and the relationships among the operating variables. These analyses required the development of several models for this type of pump at different levels of detail.
Stability and Regulation of a Variable-Displacement Vane-Pump
Authors: Karmel A. M.
Published: July 2009

Pressure fluctuations may develop in the hydraulic system of automatic transmissions, even under steady-state conditions. To analyze this phenomenon, a dynamic model was developed for a system which consists of a variable-displacement vane-pump, a regulator, and a resistive load. The model was linearized and reduced to generate a stability criterion for the pressure-regulation circuit. This criterion determines a critical frequency that the natural frequency of the pressure-regulation valve must exceed to assure stability. This critical frequency depends primarily on the damping of the spool of the pressure-regulation valve and on its position; the latter is a function of the regulation-chamber leakage characteristics. The analysis shows that line pressure, flow and leakage, along with production tolerances and different opening conditions, have a significant effect on the stability of the hydraulic system. Test data support the analysis.
Adaptive Tracking Control of Industrial Robots
Authors: Ambrosino G. , Celentano G. , Garofalo F.
Published: July 2009

A design procedure for the synthesis of an adaptive controller for a robotic manipulator is presented. The design involves the evaluation of a nominal input signal by using a model of the manipulator with nominal values of the loads, and of an adaptive component by means of the sole knowledge of the maximum possible size of the uncertain parameters of the model. The proposed control scheme also guarantees an accurate tracking of a planned path when an approximate model of the manipulator is used and/or load variations occur during operation. Moreover, the resulting control signal is smooth.
Adaptive Pulse Width Control for Precise Positioning Under the Influence of Stiction and Coulomb Friction
Authors: Yang Sangsik , Tomizuka Masayoshi
Published: July 2009

Conventional linear digital control fails to provide precise positioning of a control object under the influence of static friction, Coulomb friction, and backlash. This paper presents an adaptive pulse width control (PWC) scheme for a precise point-to-point positioning system. This scheme is developed based on the relationship between the displacement of a control object due to a single pulse input and the pulse width. The coefficient appearing in this relationship is estimated by a parameter adaptation algorithm. Sufficient conditions for asymptotic stability of this adaptive scheme are developed using Popov hyperstability theorem. This adaptive PWC is tested on a laboratory positioning table and is shown to be effective.
An Analysis of a Pneumatic Servo System and Its Application to a Computer-Controlled Robot
Authors: Liu S. , Bobrow J. E.
Published: July 2009

Pneumatic actuators are capable of providing high power output levels at a relatively low cost. In addition, they are clean, lightweight, and can be easily serviced. The difficulty of achieving a high-bandwidth, stable, pneumatic control system has limited its use in robotic position control applications. For open-loop control applications, such as many robot grippers, pneumatic actuators are often used. In this paper, direct-drive pneumatic servo-actuators are examined for their potential use in robotic applications. A complete mathematical model of the actuator is derived, and several control algorithms are tested numerically and experimentally. Our analysis shows that pneumatic systems are practical for use in servo-control applications. The main limitation is that of the system response time, which is determined by the valve flow characteristics and supply pressure. Large output forces can be obtained and accurately controlled with the servo-valve and differential pressure transducer used in the experiments.
Robot Finger Stiffness Control in the Presence of Mechanical Nonlinearities
Authors: Vossoughi R. , Donath M.
Published: July 2009

Stiffness control provides a mechanism for controlling finger position or force, and facilitates stable behavior during the transition between unconstrained motion and sudden contact with the environment. The method proposed here provides uniformity of response upon finger contact for any contact stiffness, as long as no separation occurs. The stiffness control system of a finger joint in a robot hand was partitioned into linear and nonlinear subsystems. The controller design used pole placement techniques based on the linear subsystem while the mechanical nonlinearities (i.e., load and velocity dependent nonlinear friction and nonlinear damping) in the drive were modeled separately. The parameters of the nonlinear model were experimentally identified off-line. These identified parameters were then used in a real-time estimator for compensation of the nonlinear effects while the system was under stiffness control. The technique was implemented successfully at 40 HZ on the actual finger under investigation. The results are a significant improvement on traditional techniques for nonlinear systems which result in large offsets or unstable behavior.
Observation and Estimation in Linear Descriptor Systems With Application to Constrained Dynamical Systems
Authors: Shin Kyung-Chul , Kabamba Pierre T.
Published: July 2009

This paper considers the problems of simultaneous observation or estimation of the positions, velocities, and contact forces in a constrained dynamical system. The equations of such systems are not ordinary differential equations, but descriptor equations, i.e., differential equations where the coefficient of the highest order derivative is singular. An asymptotic observer in descriptor form based on pole assignment techniques is used in the time-invariant case to reconstruct the positions, velocities, and contact forces. For time invariant constrained dynamical systems subject to random disturbances, an optimal estimator in descriptor form is designed based on Wiener-Hopf theory. Constrained dynamical systems yield descriptor systems that are uncontrollable and unobservable at infinity. As a consequence, the observer and estimator may not change the infinite eigenstructure of the system. Examples are given to illustrate the use of our method.
Nonlinear Modeling and Control of Overhead Crane Load Sway
Authors: Moustafa Kamal A. F. , Ebeid A. M.
Published: July 2009

In this paper, we derive a nonlinear dynamical model for an overhead crane. The model takes into account simultaneous travel and transverse motions of the crane. The aim is to transport an object along a specified transport route in such a way that the swing angles are suppressed as quickly as possible. We develop an antiswing control system which adopts a feedback control to specify the crane speed at every moment. The gain matrix is chosen such that a desired rate of decay of the swing angles is obtained. The model and control scheme are simulated on a digital computer and the results prove that the feedback control works well.
The Dynamic Response of a System With Preloaded Compliance
Authors: Shaw S. W. , Tung P. C.
Published: July 2009

We consider the dynamic response of a single degree of freedom system with preloaded, or “setup,” springs. This is a simple model for systems where preload is used to suppress vibrations. The springs are taken to be linear and harmonic excitation is applied; damping is assumed to be of linear viscous type. Using the piecewise linear features of the model equations we determine the amplitude and stability of the periodic responses and carry out a bifurcation analysis for these motions. Some parameter regions which contain no simple stable periodic motions are shown to possess chaotic motions.
Multidimensional State Estimation With Multiple Composite Hypothesis Testing in the Presence of Interference
Authors: Demirbas K.
Published: July 2009

A new state estimation scheme is presented for multidimensional dynamic systems with arbitrary independent interference and noises, and is based upon quantization, multiple composite hypothesis testing, and a suboptimum decoding technique of Information Theory. The estimation of the state vector is sequentially done, component-by-component, in parallel and in blocks. “Component-by-component” estimation results in a considerable memory reduction for the implementation of the scheme, while estimation is blocks makes the implementation independent of time. Simulation results, some of which are presented, have shown that the new scheme performs well, whereas the classical estimation techniques are not, in general, applicable to the state estimation problem in the presence of arbitrary interference.
Generalization of Newton-Euler Formulation of Dynamic Equations to Nonrigid Manipulators
Authors: Huang Y. , Lee C. S. G.
Published: July 2009

A recursive lumped mass/spring approximation model, based on the Newton-Euler formulation, is proposed to model the dynamics of manipulators with link flexibility. The model assumes that the displacement and rotation due to the link flexibility are measurable. For a small link deformation, a first-order lumped mass/spring approximation model is proposed, in which the parameters of each link are lumped to its joint and the link flexibility is modeled as a spring at each joint. For a larger deformation, the first-order lumped mass/spring approximation model is extended to model each nonrigid link by a series of small rigid segments connected by “pseudo-joints.” The link flexibility is modeled as a spring in each pseudo-joint. In both cases, the effects of torsion and extension are not included in the modeling. An anlaytical error analysis is performed to justify the approximation, and the mathematical relation between the maximum modeling error and the number of pseudo-joints in each link is derived. As the number of pseudo-joints approaches infinity, the joint torques computed by the extended lumped mass/spring approximation model approach the joint torques computed by other models obtained from the Lagrange’s equation.
Modeling and Identification of a Class of Servomechanism Systems With Stick-Slip Friction
Authors: Cheok Ka C. , Hu Hongxing , Loh Nan K.
Published: July 2009

This paper describes a technique for modeling and identifying a class of nonlinear servomechanism systems with stick-slip friction. The physics of the stick-slip friction is considered in modeling the process. Identification of the system parameters is formulated as a nonlinear optimization problem. A modified simplex algorithm is proposed as the optimization procedure. The difficulties encountered in choosing identification algorithm and input signals for the problem are discussed. A simulation example of a servomotor system is provided.
Design of a Disturbance Accommodating Adaptive Control System and Its Application to a DC-Servo Motor System With Coulomb Friction
Authors: Nikiforuk P. N. , Tamura K.
Published: July 2009

This paper discusses the design of a model reference type of adaptive control system for a linear unknown plant with system and observation disturbances. The disturbances are assumed to be approximately expressed by step, sinusoidal, and other analytical functions. The design of a controller, called a disturbance accommodating adaptive controller (DAAC), which eliminates the effect of these disturbances at the plant output, is described. Two types of bias DAAC are given as examples and are applied to the adaptive control of a DC-servo motor system. The plant (the DC-servo system) consists of two unknown loads connected through an electrical clutch and Coulomb friction. The effect of the friction on the plant is considered as an unknown bias disturbance and the DAAC is implemented on an analog computer. Experimental results for the position control of the DAAC system are given.
Self-Adjusting Model Algorithmic Control of a Three-Phase Electric Arc Furnace
Authors: Nadira Ramo´n , Usoro Patrick B.
Published: July 2009

An advanced control strategy, based on the principles of Self-Adjusting Model Algorithmic Control (SAMAC), for regulating the energy input to a nonlinear electric arc furnace system is presented in this paper. The SAMAC strategy is an extension of Model Algorithmic Control (MAC) designed to accommodate the nonlinear and time-varying characteristics of the arc furnace process. Simulation results show that SAMAC yields an improved performance over both the traditional MAC strategy and a conventional analog control system (typical of many existing furnace installations) in terms of commonly used classical measures of response characteristics, including speed of response, settling time, overshoot, cumulative error, and sensitivity to variations in plant parameter values (robustness).
Stable Model Reduction by Impulse Response Error Minimization Using Michailov Criterion and Pade’s Approximation
Authors: Puri N. N. , Lan D. P.
Published: July 2009

A stable model reduction technique based upon minimum impulse response error is presented. By using a stability equation along with Pade’s approximation, the proposed method maintains stability. Two parameters used in the reduced model provide the additional degree of freedom and are optimized to reduce the impulse response error. Three simple numerical examples are presented for comparison among different reduced model methods and validate the advantage of this method.
Constitutive and Modulation Structure in Bond Graph Modeling
Authors: Beaman J. J. , Rosenberg R. C.
Published: July 2009

In this paper, we investigate additional structure that might be put on bond graphs in order that (1) a bond graph has a physical realization and (2) physical realizations have bond graph within an appropriate physical domain. In particular, restrictions are proposed on the allowed form for the constitutive laws for energy storing and dissipative elements and the allowed form for the modulation of coupling elements. This added structure is proposed to ensure the existence of an energy state function, passivity, unique solutions to the model equations, and to preserve the signal nature of modulation.
Unconstrained and Constrained Mode Expansions for a Flexible Slewing Link
Authors: Barbieri Enrique , O¨zgu¨ner U¨mit
Published: July 2009

The linear equations of motion of a uniform flexible slewing link which were derived via Hamilton’s Extended Principle are considered. These equations account for the coupling between bending and rigid modes. Unconstrained and constrained mode expansions are investigated and a quantitative comparison is made between the frequency equations and associated mode shapes. A finite dimensional model is derived using the assumed modes method and the theoretical frequencies are verified with an experimental counterbalanced aluminum beam.
Nonlinear Compensation and Stochastic Control
Authors: Grimble M. J.
Published: July 2009

The usual ARMAX linear model for a discrete-time system is generalized to include a nonlinear characteristic. A nonlinear compensation scheme is proposed which enables a modified LQG control approach to be applied to the precompensated system. The solution is relatively simple and if the plant matches the modelled situation asymptotic stability is guaranteed.
Modeling Mechanical Stick-Slip Friction Using Electrical Circuit Analysis
Authors: Kolston Paul J.
Published: July 2009

A new technique for modeling stick-slip friction in mechanical systems is proposed. The technique uses an electrical circuit analysis program to analyze the electrical circuit equivalent of the mechanical system. The stick-slip characteristic can be altered to take almost any form. The method is easy to apply to a vast range of systems, and two examples are given to illustrate its validity.
On the Problem of Constrained Path Following For Manipulators
Authors: Sankaranarayanan A. , Vidyasagar M.
Published: July 2009

Force Control involves moving the end-effector of a robot manipulator on the surface of an object while ensuring that no other part of the manipulator collides with the object. Suppose C is a given contour to be followed. If the end-effector can move between two points a and b on C while meeting the collision avoidance requirement, we can say that a path exists between a and b. We begin by considering a planar manipulator and a circular contour and derive the necessary and sufficient conditions for a path to exist between a pair of points. By extending these ideas, sufficient conditions are derived for a noncircular contour. The advantages of a (kinematically redundant) 3-link planar manipulator over a 2-link manipulator are pointed out. Finally, we consider spatial manipulators and derive the necessary and sufficient conditions for the case where the contour lies on the surface of a sphere.
Bond Graph Modeling of Planar Mechanisms With Realistic Joint Effects
Authors: Zeid Ashraf
Published: July 2009

This work demonstrates that the Karnopp-Margolis method for treating derivative causality in the bond graph produces a formulation that is equivalent to the classical Lagrange λ multipliers method for the modeling of planar mechanisms. It is then demonstrated that this formulation can be used to eliminate derivative causality in general. Furthermore, the method can be used as the basis for an algorithm which automates the derivation of the dynamic equations for nonlinear systems. It is also shown that the method can be used to treat the modeling of joint nonlinearities such as joint clearances and joint compliances.
Performance Sensitivity of an Actively Damped Vehicle Suspension to Feedback Variation
Authors: Redfield R. C. , Karnopp D. C.
Published: July 2009

A two degree of freedom vehicle model is analyzed for its performance sensitivity as a function of the system’s feedback gains. Three measures of performance, namely, sprung mass isolation, suspension travel, and tire contact force variation are examined. The varied feedback gains are the spring stiffness, the passive damping coefficient, and the active damping coefficient. Both frequency response and RMS response of the performance variables are considered and surfaces are formed to examine output sensitivity to suspension feedback. The results show that RMS vehicle isolation is increased by both softening the suspension and adding active damping. RMS tire contact force is influenced mostly by passive damping and only marginally affected by active damping. Suspension stiffness is shown to have no influence suspension travel for the passive suspension modeled.
An Electronically Controlled Pressure Regulator
Authors: Trumper D. L. , Lang J. H.
Published: July 2009

This paper describes the analysis, design, implementation, and evaluation of an electronically controlled fluid back-pressure regulator system. The control scheme is unique in that it is purely electronic, and employs a nested pair of feedback loops. This approach overcomes several problems associated with purely mechanical regulation, such as friction in the control valve. Further, since the control is electronic, compensation functions are easily implemented via operational amplifier circuits. The pressure control system is derived with classical control techniques through linearization of the measured valve characteristics. The solutions to nonlinear problems encountered in the implementation are discussed. The design achieves good performance and stability over the entire pressure and flow operating regime.
Controller Design Robust to Frequency Variation in a One-Link Flexible Robot Arm
Authors: Korolov V. V. , Chen Y. H.
Published: July 2009

The end-point position control problem of a one-link flexible robot arm under wide spectrum of operating conditions is considered. Natural frequency variations may arise in practice and are treated as the uncertainty. A robust control scheme is designed for the manipulator for some guaranteed performances without the complete knowledge of uncertainty. The only required information of the uncertainty is its possible bound.
Stability Limits of Linear Feedback Control Systems
Authors: Maslen Eric , Townsend Miles
Published: July 2009

A new method is presented for determining the stability limits of open loop gains in linear feedback controlled systems. The method does not require finding the roots of multiple polynomials in k, the loop gain, as in the case of the commonly used algebraic Routh array technique. Instead, the roots of a single polynomial in s (the Laplace variable) of order at least one less than that of the system are evaluated to directly determine where the root locus crosses the imaginary axis.
An Identification Method of Multiinput, Multioutput Linear Dynamical Systems for the Experimental Modal Analysis of Mechanical Structures
Authors: Kano H.
Published: July 2009

A parameter identification method is proposed that can be used to evaluate dynamic characteristics of mechanical structures modeled as multiinput multioutput linear dynamical systems. The discrete transfer function matrix is identified in two steps, one for the denominator and the other for the numerators, where the model order is determined with the aid of a “prediction” error function. The continuous counterpart is then obtained by herein developed formula that links discrete and continuous models, from which vibration modal parameters are derived. Finally, the method is applied to the data obtained from vibration experiments of a test structure, and verified its practical usefulness.
A Suboptimum Maximum Likelihood Approach to Parametric Signal Analysis
Authors: Fassois S. D. , Eman K. F. , Wu S. M.
Published: July 2009

A computationally efficient approach to stochastic ARMA modeling of wide-sense stationary signals is proposed. The discrete estimator minimizes a modified version of the likelihood function by using exclusively linear techniques, and thus circumventing the high computational complexity of the Maximum Likelihood (ML) method. The proposed approach is thus easy to implement, requires no explicit second order statistical information, and is shown to produce high quality estimates at a very modest computational cost. A recursive version of the algorithm, suitable for on-line implementation, is also developed, and, modeling strategy issues discussed. The effectiveness of the proposed approach is finally established through numerical simulations and comparisons with other suboptimum schemes.
Variational Modal Identification of Conservative Nongyroscopic Systems
Authors: Silverberg L. , Kang S.
Published: July 2009

A new modal identification method for Conservative Nongyroscopic Systems is proposed. The modal identification method is formulated as a variational problem in which stationary values of a functional quotient are sought. The computation of the functional quotient is carried out using a set of admissible functions defined over the spatial domain of the system. Measurements of the free system response at discrete points are carried out using any combination of displacements, velocities, and/or accelerations. Three types of admissible functions have been considered—global functions, spatial Dirac-delta functions, and finite element interpolation functions. The variational modal identification method is applied to a pure bending vibration problem, to a pure longitudinal vibration problem, and to a combined bending and longitudinal vibration problem. The effectiveness of the variational modal identification method using different sets of admissible functions is examined.
The Role of Inertia Sensitivity in the Evaluation of Manipulator Performance
Authors: Wiens G. J. , Scott R. A. , Zarrugh M. Y.
Published: July 2009

The sensitivities of the eigensystem of a manipulator’s generalized inertia matrix with respect to kinematic (geometric and joint variable) parameters are used to form a set of indices as a measure of manipulator performance. The indices indicate the relative magnitude of the nonlinear forces (Coriolis and centripetal) and the effects due to the changes in geometric parameters. They also provide a new graphical means for delineating paths involving small nonlinear forces throughout the workspace. In addition, the inertia matrix is examined for invariance conditions. Finally, a design/path planning scenario is presented which utilizes the information provided by the indices.
Optimal Force Distribution for Payload Positioning Using a Planar Dual-Arm Robot
Authors: Carignan C. R. , Akin D. L.
Published: July 2009

This paper presents a parameter optimization technique for deciding the force distribution on a payload being transported along a predetermined trajectory using two planar manipulator arms. The methodology begins by transforming the singular dynamics of two-arm transport to an ordinary set of differential equations and then proceeds to obtain a relation between the torques exerted by each arm. This relation is then used in a quadratic torque cost which is subsequently minimized to yield an optimal torque distribution. Significant savings in energy were found to occur when the arms were allowed to interact by transmission of forces through the payload. Even more significant are the savings found over one-arm transport of payloads where the arm torques are fixed by the prescribed trajectory.
On the Constraint Violations in the Dynamic Simulations of Multibody Systems
Authors: Ider S. K. , Amirouche F. M. L.
Published: July 2009

This paper presents an automated and efficient mathematical model for checking the violations of the constraints in the dynamics of multibody systems. The superfluous generalized independent speeds are obtained through a new transformation matrix called a pseudo-uptriangular decomposition (PUTD). The violation of the constraints is checked using a test condition between the generalized speeds and the independent speeds. A decision is then made to whether the transformation matrix needs to be regenerated. The method presented has a number of advantages over previously developed methods, since it requires less computational time and is suited for a large class of problems. It is believed that the use of Kane’s equations as presented in this paper make the analysis of constrained multibody systems even more tractable. Some examples used for the verification of the procedure are presented.
Periodic Response of a Link Coupling With Clearance
Authors: Choi Y. S. , Noah S. T.
Published: July 2009

The nonlinear, steady-state response of a displacement-forced link coupling with clearance with finite stiffness is determined. The solution procedure is derived from satisfying the boundary conditions at the contact points and then solving the resulting nonlinear algebraic equations by setting the duration of contact as a parameter. This direct approach to determining periodic solutions for systems with clearances with finite stiffness is substantially more efficient than numerical integration schemes. Results in terms of contact forces and durations of contact are pertinent to fatigue and wear studies. Parametric relations are presented for effects of the variation of damping, stiffness, exciting displacement, and gap length on the dynamic behavior of the link pair.
Thermal-Fluid Model for Weld Pool Geometry Dynamics
Authors: Saedi Hamid Reza , Unkel William
Published: July 2009

This paper describes an experimental and analytical program to provide a predictive weld pool modeling technique useful as one component of a feed back control automatic welding machine. Stationary arc experiments were performed with stainless-steel plugs and showed two different regimes in the growth of the weld pool. Initially the surface tension driven flow was dominant in the shaping of the pool (t<3 s). Once enough material was molten, the electromagnetic (E-M) forces became the dominant factor. This behavior was also observed for the moving arc cases. Detailed measurements of the pool shape were made for steady and transient conditions. A thermal-fluid model of the weld pool was developed for the case of a stationary arc in which a deep paraboloidal pool is formed. This model uses the current and heat distribution at the anode surface as inputs. Matching of convective and conductive heat fluxes along the melt boundary was used to predict the weld pool shape. The conductive heat flux on the solid side was calculated by the finite element method. The convective heat flux on the liquid side was calculated by solving the fluid and heat transfer equations assuming a single cell circulation flow inside the weld pool. For the stationary arc cases under consideration, the E-M force field was found to dominate the flow pattern. This method was capable of determining the transient in weld pool geometry for changes in different process conditions, e.g., arc length, pulsed current. Comparison between experiments and the model showed agreement of weld pool size (top width and penetration) within 10 percent. This modeling technique can be extended to analyse weld pools with multi-cell circulation patterns which are encountered in the moving arc and the stationary arc cases with a shallow pool.
Alternative Control Laws for Automotive Active Suspensions
Authors: Yue C. , Butsuen T. , Hedrick J. K.
Published: July 2009

A two degree of freedom (1/4 car model) is used to evaluate alternative linear control laws. Control laws considered are full state feedback, sprung mass absolute velocity feedback and an LQG regulator using suspension deflection as the measurement. It is shown that all three can yield improvements to the sprung mass ride quality but that overall the LQG regulator using suspension deflection provides the best trade-off between ride quality, suspension packaging and road holding constraints.
The Pumping Dynamics of Swash Plate Piston Pumps
Authors: Edge K. A. , Darling J.
Published: July 2009

This paper describes a study of the cylinder pressure and flow in an oil hydraulic axial piston pump. A comparison is made between a theoretical model based on the effects of fluid compliance within the cylinder, and an improved model which accounts for the influence of oil momentum in the port plate region. The improved model is validated by comparison with experimental test results and is used to analyze the influence of port plate and relief groove design on cylinder pressure and pump flow ripple. A steeply sloping triangular cross-section groove was found to be the most satisfactory design.
Singular Perturbation Analysis of Speed Controlled Reciprocating Compressors
Authors: Liakopoulos A. , Boykin W. H.
Published: July 2009

A singular perturbation analysis of speed controlled reciprocating compressors is presented. For weakly perturbed systems, analytical solutions for the steady-state and transient response are given. For strongly perturbed systems numerical results in both time and frequency domains are presented. The analytical solutions are useful in calculating reaction forces and torques applied on inertially stabilized platforms, in designing feed forward compensators and in simplifying parameter identification procedures. Furthermore, they clearly exhibit the dependence of response to system parameters.
A Proportional-Integral Controller for Resistance Spot Welding Using Nugget Expansion
Authors: Chang H. S. , Cho Y. J. , Choi S. G. , Cho H. S.
Published: July 2009

An electrode wear has been found to cause considerable quality variation in the process of resistance spot welding. This paper presents a study on the electrode wear growth and develops a microprocessor-based feedback controller that can compensate weld quality variation due to electrode deterioration. The controller developed in this study utilizes a PI control algorithm, incorporating the electrode movement as a feedback signal. A series of experiments was performed to clarify the wear growth phenomenon and to evaluate the performance of the controller. The experimental results show that the electrode wear can significantly cause quality deterioration, but this can be effectively compensated via application of this proposed control technique.
H
∞ Optimal Robust Control of Feedback Systems
Authors: Tsai Mi-Ching , Shin Yen-Ping
Published: July 2009

In this paper, we apply and extend Young’s algorithm for the Nevanlinna-Pick problems to solve an optimal robust stabilizer in multivariable feedback control systems. A sufficient condition for the existence of a robust stabilizer, in terms of the unstable poles of a given nominal plant and its uncertainty band function, is derived and an explicit formula for synthesizing the optimal robust stabilizer is also given.
On Passive Implementation of Feedback Control Systems
Authors: Shoureshi R.
Published: July 2009

Closed-loop control systems, especially linear quadratic regulators (LQR), require feedbacks of all states. This requirement may not be feasible for those systems which have limitations due to geometry, power, required sensors, size, and cost. To overcome such requirements a passive method for implementation of state feedback control systems is presented.
Nonlinear Observers—A State-of-the-Art Survey
Authors: Misawa E. A. , Hedrick J. K.
Published: July 2009

The state-of-the-art of nonlinear state estimators or “observers” is reviewed. The use of these observers in real time nonlinear compensators is evaluated in terms of their on-line computational requirements. Their robustness properties are evaluated in terms of the extent to which the design requires a “perfect” model.
A Decentralized Multiple Model Adaptive Filtering for Discrete-Time Stochastic Systems
Authors: Watanabe Keigo
Published: July 2009

A decentralized multiple model adaptive filter (MMAF) is proposed for linear discrete-time stochastic systems. The structure of decentralized multiple model studied here is based on introducing a global hypothesis for the global model and a local hypothesis for the local model, where it is assumed that the former hypothesis includes the latter one as a partial element. Algorithms for the decentralized MMAFs in unsteady and steady-state are derived using recent results in decentralized Kalman filtering. The results can be applied in designing a system for sensor failure detection and identification (FDI). An example is included to illustrate the characteristics of such a FDI system for the estimation of lateral dynamics of the hydrofoil boat.
Utilization of Control Effort Constraints in Linear Controller Design
Authors: Ulsoy A. Galip
Published: July 2009

A linear controller design procedure, which accounts for constraints on control effort, is developed by requiring that the control system utilize the maximum energy delivering capability of the final control elements under some specified test conditions (e.g., maximum step reference input). Results using this approach are available from previous studies for low-order single-input single-output controlled systems. This paper presents results for multi-input multi-output systems where the number of inputs is equal to the number of states. Both state variable feedback control for regulation, and integral plus state variable feedback control for tracking are considered and illustrated with an example problem.
Some Bond Graph Structural Properties: Eigen Spectra and Stability
Authors: Zeid A.
Published: July 2009

What does the structure of the bond graph reveal about the eigenvalues of linear systems and about the stability of the linear and nonlinear systems they represent? In an earlier work, estimates of the eigen spectra of systems were given based on the structural classification of a canonical form of the bond graph. This work provides stability criteria based on the structure of the bond graph canonical form for linear and nonlinear time invariant dynamic systems. Tighter bounds on the eigen spectrum are also provided for the class of systems with uniform tree simple full graphs. It is shown that if a system is modeled by a standard bond graph whose canonical form is of the simple full or simple partial class, then estimates of the system stability, asymptotic stability, or instability can be obtained directly from the properties of the resistance field. The stability estimates can be automated and are obtained prior to the derivation of the dynamic equations. The stability properties can be used also as a design tool to suggest stabilizing feedback at the graphical modeling stage of the design process.
Selection of Dynamic Sensors and Actuators in the Control of Linear Systems
Authors: Norris G. A. , Skelton R. E.
Published: July 2009

This paper selects sensors and actuators (location, type, and number) from an admissible set. We seek an approximate solution to this integer programming problem. Given the optimal use of the entire admissible set of sensors and actuators, it is possible to decompose the quadratic cost function into contributions from each stochastic input and each weighted output. In the past, these suboptimal cost decomposition methods of sensor and actuator selection have been used to locate perfect (infinite bandwidth) sensors and actuators on large scale systems. This paper extends these ideas to the more practical case of imperfect actuators and sensors with dynamics of their own. Secondly, the old cost decomposition methods are discarded for improved formulas for sensor and actuator deletion (from the admissible set). These results show that there exists an optimal number of actuators (it is possible to use too few and too many). Preliminary attempts to solve this new research question are described. It is also shown that there exists optimal dynamics of the actuators. NASA’s SCOLE example demonstrates the concepts.