bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Control of Backlash in the Drive Mechanism of a Radially Rotating Compliant Beam
Authors: Chalhoub Nabil G. , Zhang Xiaoying
Published: February 2008

The exclusion of the dynamic characteristics of indirect drives, from the controller design, has often led to a degraded performance in precision servomechanisms. In this study, the adverse effects of backlash, in the drive mechanism of a radially rotating flexible beam, are examined. The topological variations of the structure are handled by latent constraint equations which can be rendered active through the monitoring of the contact torque as well as kinematic indicators. A “backlash controller” is introduced to replace the original controller of the beam only during the period of gear disengagement. The experimental and numerical results provide a qualitative validation of the backlash model. The relationships with which the backlash in gearing would interact with both the servo-loop controller and the structural flexibility of the system are investigated. In addition, the digital simulations have proven that the “backlash controller” provides a viable approach in reducing the adverse effects of backlash on the overall system response.
Bond Graph Models for Linear Motion Magnetostrictive Actuators
Authors: Bryant M. D.
Published: February 2008

Bond graph models for the audio range response of a dynamically continuous, linear motion magnetostrictive actuator are formulated and presented. The actuator involves a continuous rod of magnetostrictive material that extends, contracts, and vibrates in modes when energized by magnetic flux produced by a coil. The left end is fixed, force is extracted from the right end. The bond graph model includes dynamics of the energizing coil, the flux routing circuit, magnetic to mechanical energy conversion, and mechanical elements. Constitutive relations for magnetostriction suggest use of a multipart capacitor with ports for magnetic and mechanical power flow; constraints imposed by modal dynamics require a separate mechanical port for each vibration mode. Values were assigned to bond graph parameters in a non-empirical manner: solely from theory and handbook data. State equations and transfer functions were extracted from the bond graph. For audio range operation, theory (the bond graph model) compared well with experiment (measurements taken on a magnetostrictive actuator designed and built by the author).
An Analysis of the Effects of Torque, Engine Geometry, and Speed on Choosing an Engine Inertia Model to Minimize Prediction Errors
Authors: Pan Chung-Hung , Moskwa John J.
Published: February 2008

Constant inertia engine models have been used for years by control engineers to attain real-time engine simulations. The accuracy of the estimation largely depends on the selection of the constant engine inertia value used in these engine models. A methodology that uses the least squares method to calculate the engine inertia value for constant inertia engine model is developed. This methodology enables the constant inertia engine model simulations to have minimum acceleration estimation errors. The effects of net external torque, engine geometry, and speed on the inertia value computation are also investigated. Since most of the constant inertia engine models use the averaged engine inertia as the constant inertia value, comparisons of these two inertia values in engine operation simulations are presented. Discussions of the advantages and disadvantages of both methods are also included. Precautions and restrictions of using the methodology are discussed as well.
Experimental Robustness Study of a Second-Order Sliding Mode Controller
Authors: Blom Andre´ , de Jager Bram
Published: February 2008

The design of a Second-Order Sliding Mode Controller is discussed and guidelines are given for tuning. The robustness to unmodeled dynamics and parameter-errors is investigated and tested in an experimental case study. The experimental results, as far as robustness to unmodeled dynamics is concerned, are not better than for a traditional PD-controller. When robustness to parameter-errors is concerned the Second-Order Sliding Mode Controller performs slightly better.
On Position/Force Control of Robot Interacting With Dynamic Environment in Cartesian Space
Authors: Vukobratovic´ Miomir , Stojic´ Radoslav
Published: February 2008

In this paper, the problem of simultaneous stabilization of both the robot motion and interaction force in Cartesian space, based on the unified approach to contact task problem in robotics [1], is considered. This control task is solved under the conditions set on environment dynamics which are less restrictive than those in [1] where some particular environment properties are required to ensure overall system stability. Furthermore, the one-to-one correspondence between closed-loop motion and force dynamic equations is obtained and unique control law ensuring system stability and preset either motion or force transient response is proposed.
Parallel Computational Algorithms for the Kinematics and Dynamics of Planar and Spatial Parallel Manipulators
Authors: Gosselin C. M.
Published: February 2008

This paper introduces a novel approach for the computation of the inverse dynamics of parallel manipulators. It is shown that, for this type of manipulator, the inverse kinematics and the inverse dynamics procedures can be easily parallelized. The result is a closed-form efficient algorithm using n processors, where n is the number of kinematic chains connecting the base to the end-effector. The dynamics computations are based on the Newton-Euler formalism. The parallel algorithm arises from a judicious choice of the coordinate frames attached to each of the legs, which allows the exploitation of the parallel nature of the mechanism itself. Examples of the application of the algorithm to a planar three-degree-of-freedom parallel manipulator and to a spatial six-degree-of-freedom parallel manipulator are presented.
Pneumatic Assist Device for Gait Restoration
Authors: Shiraishi M. , Watanabe H.
Published: February 2008

An assist device for gait restoration powered by body weight has been developed using pneumatic equipment. The aim of this system is to assist people who have weakened lower limbs and require rehabilitation for walking. An experimental design system based on a mechanical bracing structure demonstrates the possibility of using upper body weight to power a pneumatically operated assistive walking system for weakened lower limbs. Continuous forward stepping can be achieved by shifting the upper body weight consecutively from one walking stick to the other through the upper limbs. The main feature of the proposed device is that an individual “walks” using his own energy.
Experimental Results of Adaptive Periodic Disturbance Cancellation in a High Performance Magnetic Disk Drive
Authors: Sacks Alexei , Bodson Marc , Khosla Pradeep
Published: February 2008

This paper considers the implementation of an adaptive algorithm for periodic disturbance cancellation. It is shown that the maximum rate of adaptation can be calculated precisely based on measurements of the system’s frequency response. The response of the closed-loop system to additional disturbances can also be computed on that basis. The results are verified experimentally on a high track density magnetic disk drive. Excellent matching between the theoretical and experimental results is observed. An improved method is also proposed that leads to faster convergence of the adaptive algorithm and better disturbance rejection capabilities. The results of this paper significantly enhance the ability of the control engineer to design and analyze adaptive feedforward algorithms for a variety of applications where periodic disturbances are encountered.
Sensing of Motion Related Errors in Multiaxis Machines
Authors: Lin P. D. , Ehmann K. F.
Published: February 2008

The aim of this paper is the formulation of the principles for the development of optical measurement systems for the measurement of motion related errors in multiaxis machines. Basic system configurations for rotary and prismatic joints are discussed, and their governing linearized equations derived in explicit analytical form.
Comparison of Sliding Mode Control With State Feedback and PID Control Applied to a Proportional Solenoid Valve
Authors: Gamble J. B. , Vaughan N. D.
Published: February 2008

A novel nonlinear sliding mode controller has recently been developed for direct acting proportional solenoid valves. This paper presents a comparison between the valve performance using this controller, and that obtained using two alternative control strategies; state feedback and PID control. Each controller is described in turn, and experimental step response results are presented to demonstrate the validity of each strategy. These results are compared on the basis of response time, overshoot, and steady-state error. The time taken to design each controller, and the required level of knowledge of the valve dynamics, are also assessed. The ability of each controller to reject flow reaction forces is evaluated by observing the changes in the step response when oil is passed through the valve. The results demonstrate that the sliding mode controller results in a faster, more robust closed-loop response. In addition, only minimal knowledge of the valve dynamics is required in order to design the controller.
Part II: Control of a One-Degree-of-Freedom Active Hydraulic Mount
Authors: FitzSimons P. M. , Palazzolo J. J.
Published: February 2008

In the first part of this investigation, a model of an active hydraulic mount was developed using the method of conic sector bounding to capture plant nonlinearities. The purpose of the mount is to make a mass that is driven by an external force and a hydraulic actuator behave as if it were a prescribed mechanical impedance driven solely by the external force. A two-degree-of-freedom control system, that consists of a feedback controller and a prefilter, is proposed as a solution. A position-velocity-acceleration (PVA) feedback controller using classical root locus methods and an H2-optimal feedback controller are designed using the plant model. A prefilter is then used to prescribe the mechanical impedance of the mount. The performance of these control systems is investigated in the frequency domain using Robust Control Theory. Finally, numerical simulations of a high-fidelity nonlinear model are used to assess the performance of each controller in the time domain.
Servo Design for a 3-D Laser-Tracking Measurement System
Authors: Yen Jia-Yush , Jeng Chao-Si , Fan Kuang-Chau
Published: February 2008

This paper addresses the servo design for a real-time, laser-tracking, three-dimensional (3-D), position measurement system. The 3-D measurement system uses two sets of tracking mirrors to shine laser beams toward the measurement point. By examining the angles of these mirrors, one can calculate the position of this point. The servo loop in the measurement system corrects the mirror orientations by continuously checking and compensating the offset between the out going laser beam and the beam reflected from a retro-reflector attached to the measurement point. To achieve high speed and high accuracy measurement, the tracking servo system has to compensate for the highly nonlinear nature of the system and maintain the laser beams close to the measurement point. This paper derives the relationship between the tracking angle rotations and the measured beam offsets. By including this relationship in the system model, the linear H∞ optimization technique can be applied for controller synthesis. All the design specifications are then directly implemented.
An LQ Approach to Active Control of Vibrations in Helicopters
Authors: Bittanti Sergio , Lorito Fabrizio , Strada Silvia
Published: February 2008

In this paper, Linear Quadratic (LQ) optimal control concepts are applied for the active control of vibrations in helicopters. The study is based on an identified dynamic model of the rotor. The vibration effect is captured by suitably augmenting the state vector of the rotor model. Then, Kalman filtering concepts can be used to obtain a real-time estimate of the vibration, which is then fed back to form a suitable compensation signal. This design rationale is derived here starting from a rigorous problem position in an optimal control context. Among other things, this calls for a suitable definition of the performance index, of nonstandard type. The application of these ideas to a test helicopter, by means of computer simulations, shows good performances both in terms of disturbance rejection effectiveness and control effort limitation. The performance of the obtained controller is compared with the one achievable by the so called Higher Harmonic Control (HHC) approach, well known within the helicopter community.
Examination of Different Control Strategies of Heavy-Vehicle Performance
Authors: Palkovics L. , El-Gindy M.
Published: February 2008

Heavy vehicles play an economically important role in the transportation process, and their numbers have been increasing for several decades. The active safety of the highway system is an important consideration in the design of a heavy vehicle combination. In this paper, the handling characteristics of a 5-axle tractor-semitrailer is examined and used to test for the desired features of the vehicle’s handling and stability. Using these results the optimal control criterion is derived for the vehicle. Four different control strategies are examined by using the Linear Quadratic Regulator (LQR) approach. These are, active steering of the rear wheels of the tractor; active steering of the wheels of the trailer; active torque control in the fifth-wheel joint; and active yaw torque acting on the tractor. These controllers are designed and examined using a simplified linear vehicle model. In addition to discussing the above-mentioned approaches, this paper discusses a method of modifying the slip angles at the tractor’s rear (driven) axles, however the yaw torque at the tractor cg also can be controlled using what is called “unilateral braking.” As well, the replacement of the active torque control at the fifth wheel joint, by a control strategy based on the usage of controllable dampers at the fifth-wheel joint, will also be examined. In this case, a nonlinear mathematical model of the vehicle is used and a modified control strategy called the RLQR/H∞ approach is used to ensure the vehicle’s performance in the presence of parametric uncertainties. The examination of these control strategies is conducted by using a sophisticated non-linear vehicle model, and the influence of these control strategies on the vehicle’s directional and roll stability during severe path-follow lane-change manoeuvre is discussed.
Control of Suspensions for Vehicles With Flexible Bodies—Part II: Semi-Active Suspensions
Authors: Hac´ Aleksander , Youn Iljoong , Chen Hsien H.
Published: February 2008

Two methods of control of semi-active suspensions that specifically address the problem of structural vibrations of the vehicle body are considered. These control strategies are based on those developed for active suspension systems in Part I of this study and rely on either modifications of suspension control forces that account for body compliance or on the addition of a proof-mass actuator to reduce structural vibrations. A half-car model that includes body compliance is used to evaluate the effects of these control strategies on the performance of the suspensions with two-state and continuously modulated dampers. The performances of the systems are evaluated in both the time and frequency domains. The effect of time delays in the process of actuating the adjustable dampers is investigated. Significant reductions of structural vibrations are observed when the nodes of body beaming modes are a sufficient distance away from the suspension mounting points, and the time delays in the control system are negligible. The results deteriorate markedly when two-state dampers are used instead of continuously variable dampers or when a time delay in excess of 5 ms is present in the control loop. When the preference in suspension design shifts toward road holding it becomes increasingly difficult to improve the vehicle structural response without sacrificing other aspects of performance.
Vehicle/Guideway Dynamic Interaction in Maglev Systems
Authors: Cai Y. , Chen S. S. , Rote D. M. , Coffey H. T.
Published: February 2008

The importance of vehicle/guideway dynamics in maglev systems is discussed. The particular interests associated with modeling vehicle/guideway interactions and explaining response characteristics of maglev systems for a multicar, multiload vehicle traversing on a single- or double-span flexible guideway are considered, with an emphasis on vehicle/guideway coupling effects, comparison of concentrated and distributed loads, and ride comfort. Coupled effects of vehicle/guideway interactions over a wide range of vehicle speeds with various vehicle and guideway parameters are investigated, and appropriate criteria for decoupling at critical vehicle speeds or crossing frequencies are identified.
Control of the Fabrication of Long Slender Workpieces of Arbitrary Shape—Part I: Open-Loop Control of the Multi-Axis Bending Process
Authors: Luo J. X. , Joynt D. L. , Stelson K. A.
Published: February 2008

Computer numerically controlled (CNC) multi-axis bending is a new metal-forming process used to fabricate long slender workpieces of arbitrary shape and cross section. This process can achieve higher productivity and flexibility than conventional forming processes. However, a manual trial-and-error process has been adopted to find control commands that would produce accurate part shape in mass production. This traditional approach which completely relies on the skills of the machine operator often results in long lead-times and great cost in setting up the bender for a new part. A new methodology has been developed, using the geometrical concept of intrinsic part representation, to model the workpiece and fabricating process. The process model compensates for elastic and fabricating process. The process model compensates for elastic springback, and can be used to predict a set of initial multi-axis control commands which will eventually converge to the final commands through a feedback process. The effectiveness of the method has been demonstrated experimentally.
Robust Joint and Cartesian Control of Underactuated Manipulators
Authors: Bergerman Marcel , Xu Yangsheng
Published: February 2008

Underactuated manipulators are robot manipulators composed of both active and passive joints in serial chain mechanisms. The study of underactuation is significant for the control of a variety of rigid-body systems, such as free-floating robots in space and gymnasts, whose structure include passive joints. For mechanisms with large degrees of freedom, such as hyper-redundant snake-like robots and multi-legged machines, the underactuated structure allows a more compact design, weight decrease, and energy saving. Furthermore, when one or more joints of a standard manipulator fail, it becomes an underactuated mechanism; a control technique for such system will increase the reliability and fault-tolerance of current and future robots. The goal of this study is to present a robust control method for the control of underactuated manipulators subject to modeling errors and disturbances. Because an accurate modelling of the underactuated system is more critical for control issues than it is for standard manipulators, this method is significant in practice. Variable structure controllers are proposed in both joint space and Cartesian space, and a comprehensive simulation study is presented to address issues such as computation, robustness, and feasibility of the methods. Experimental results demonstrate the actual applicability of the proposed methods in a real two-degrees-of-freedom underactuated manipulator. As it will be shown, the proposed variable structure controller provides robustness againstboth disturbances and parametric uncertainties, a characteristic not present on previously proposed PID-based schemes.
Model Error Compensation for Bearing Temperature and Preload Estimation
Authors: Tu Jay F. , Stein Jeffrey L.
Published: February 2008

A simple to apply, two-step observer design methodology is developed for a general class of systems with model uncertainty. This approach is applied to estimate bearing internal temperatures and the bearing preload of a machine tool spindle. The first step is the design of a model error compensator (MEC) to account for the model error associated with the bearing friction heat generation. The second step includes a conventional observer based on the nominal model that results from the implementation of the MEC. The sufficient condition for constructing an effective MEC loop for the target spindle system is derived. The effectiveness of the MEC loop is demonstrated experimentally by comparing several different conventional observer designs, with and without the MEC. A comparison of the measurements to the estimation results indicate in all cases tested the MEC improves the performance of the conventional observers. In addition, the results clearly show the distinctly different bearing outer ring/housing, rolling elements, and inner ring temperature behaviors. From the temperature estimation results, it is shown that previously published data on initial transient error associated with preload estimation is mainly due to the estimation error in the rolling element temperature. The proposed two-step observer methodology appears to be well suited for bearing temperature and preload monitoring problems.
Stability and Performance Robustness Analysis of Repetitive Control Systems Using Structured Singular Values
Authors: Gu¨venc¸ Levent
Published: February 2008

The structured singular value method is applied to continuous-time SISO repetitive control systems in order to determine their stability and performance robustness in the presence of structured parametric modeling error in the plant. Performance measures for repetitive control systems are introduced and the robust performance analysis using structured singular values is modified, taking the alternating magnitude behaviour of the sensitivity function of a repetitive control system into account. The analysis procedure is simplified considerably in the case of large time delay by noting that the upper and lower envelopes of the structured singular value plots are obtained from corresponding finite dimensional systems without any time delay. The analysis procedures developed are applied to an example on repetitive control of an electrohydraulic material testing machine, available in the literature, to demonstrate their usefulness.
Adaptive Rejection of Periodic Disturbances With Unknown Period
Authors: Hillerstro¨m G. , Sternby J.
Published: February 2008

A disturbance cancellation extension by means of Youla parametrization to a stabilizing nominal controller is investigated. In the case of a known disturbance model, disturbance frequencies or period time, it may be implemented directly as an add-on device to the existing control system. The nominal control system may be designed without consideration of the deterministic disturbances. This way it may suffice with a PID controller. It may also be a more complex one e.g., designed to obtain certain robustness properties. For known relation between the disturbance frequencies (one or more periodic signals) but unknown fundamental frequency, a frequency shaped disturbance model estimation scheme is utilized. This makes it possible to e.g., adapt the disturbance model to minimize the error directly with respect to the output. For periodic disturbances the scheme implements a self-tuning discrete time repetitive controller. To illustrate the feasibility of the approach taken it is used for rejecting a periodic disturbance acting on a nonminimum-phase plant.
A New Algorithm for Testing the Stability of a Polytope: A Geometric Approach for Simplification
Authors: Shaw Jinsiang , Jayasuriya Suhada
Published: February 2008

Considered in this paper is the robust stability of a class of systems in which a relevant characteristic equation is a family of polynomials F: f(s, q) = a0(q) + a1(q)s + … + an(q)sn with its coefficients ai(q) depending linearly on q unknown-but-bounded parameters, q = (p1, p2, …, pq)T. It is known that a necessary and sufficient condition for determining the stability of such a family of polynomials is that polynomials at all the exposed edges of the polytope of F in the coefficient space be stable (the edge theorem of Bartlett et al., 1988). The geometric structure of such a family of polynomials is investigated and an approach is given, by which the number of edges of the polytope that need to be checked for stability can be reduced considerably. An example is included to illustrate the benefit of this geometric interpretation.
Observer-Based Feedback Linearizing Control of an Electromagnetic Suspension
Authors: Fabien B. C.
Published: February 2008

This paper develops a stabilizing observer-based feedback linearizing controller for a single-axis electromagnetic suspension. The controller uses only the measured output of the system, and is shown to be robust with respect to parameter uncertainty. The controller differs from other robust feedback linearizing controllers that have appeared in recent literature, because it is continuous, and non-adaptive. Lyapunov’s second method is used to prove stability and robustness of the controller. The controller has a simple structure and its gains are determined by solving two weakly coupled Riccati equations. Numerical simulations are performed to compare a linear feedback controller and the observer-based feedback linearizing controller. Results obtained demonstrate that the nonlinear controller yields superior performance when compared with the linear feedback controller. The controller synthesis technique developed in this paper is applicable to other fully feedback linearizable systems, not just electromagnetic suspensions.
Dynamic Response of the Manipulator Tip to a Random Excitation
Authors: Kujath Marek R. , Akpan Unyime O.
Published: February 2008

The paper describes the tip responses of a flexible articulated manipulator to a stationary random excitation of the base. The expressions for the covariance tensors of the manipulator tip motion are developed in the base and the inertia frame. The singular value decomposition technique is applied for the derivation of expressions for the principal variances. The principal variances are computed and discussed for a wide range of manipulator configurations and damping coefficients.
H ∞ Robust Control of Flexible Beam Vibration by Using a Hybrid Damper
Authors: Lee Chong-Won , Jee Won-Ho
Published: February 2008

A new hybrid damper is proposed to suppress the vibration of a flexible cantilever beam at its free end. It consists of an active piezoelectric-type servo-damper and a passive dampled vibration absorber to effectively suppress both the small and large amplitude vibrations. The H∞ control scheme is successfully applied to a laboratory test rig equipped with the hybrid damper when its overhung length is continually changed.
Nonlinear PI Compensators That Achieve High Performance
Authors: Shahruz S. M. , Schwartz A. L.
Published: February 2008

In this paper, linear time-invariant single-input single-output (SISO) systems that are stabilizable by a (linear) proportional and integral (PI) compensator are considered. For such systems a five-parameter nonlinear PI compensator is proposed. The parameters of the proposed compensator are tuned by solving an optimization problem. The optimization problem always has a solution. Additionally, a general non-linear PI compensator is proposed and is approximated by easy-to-compute compensators, for instance, a six-parameter nonlinear compensator. The parameters of the approximate compensators are tuned to satisfy an optimality condition. The superiority of the proposed nonlinear PI compensators over the linear PI compensator is discussed and is demonstrated for a feedback system.
Electromechanical Modeling of Hybrid Piezohydraulic Actuator System for Active Vibration Control
Authors: Tang Punan , Palazzolo Alan B. , Kascak Albert F. , Montague Gerald T.
Published: February 2008

Electromechanical modeling of a hybrid piezohydraulic actuator system for active vibration control was developed. The transfer function of piezoelectric actuator was derived from the electromechanical potential energy law. This transfer function represents the dynamic relationship between input electric voltage and piezoelectric actuator displacement. The hydraulic actuator was characterized by impedance matching in which its transfer functions were experimentally determined. The transfer functions were transformed into a state-space representation, which is easily assembled into an active vibration control (AVC) closed-loop simulation. Good correlation of simulation and test was achieved for the hybrid system. A closed-loop dynamic simulation for imbalance response with/without AVC of a spinning rotor test rig at NASA Lewis was performed and showed excellent agreement with test results. The simulation couples the piezoelectric, hydraulic, and structural (rotor) components.
Kalman Filtering Error Due to Inaccuracy in Filter’s Initial Condition
Authors: Gajic Z. , Boka J.
Published: February 2008

It is a very well known fact that the initial condition of the optimal linear Kalman filter has to be set at the mean value of the system initial state. In this paper, we have derived an expression for the filtering error in the case when this condition is not satisfied. Both continuous- and discrete-time domain filters are considered. The obtained results are simple and elegant and clearly indicate the effect of the erroneous filter’s initial condition. An example is included in order to demonstrate the results obtained.
Optimal Rejection of Stochastic and Deterministic Disturbances
Authors: Sparks A. G. , Bernstein D. S.
Published: February 2008

The problem of optimal H2 rejection of noisy disturbances while asymptotically rejecting constant or sinusoidal disturbances is considered. The internal model principle is used to ensure that the expected value of the output approaches zero asymptotically in the presence of persistent deterministic disturbances. Necessary conditions are given for dynamic output feedback controllers that minimize an H2 disturbance rejection cost plus an upper bound on the integral square output cost for transient performance. The necessary conditions provide expressions for the gradients of the cost with respect to each of the control gains. These expressions are then used in a quasi-Newton gradient search algorithm to find the optimal feedback gains.
Dynamic Path Planning for Robot Navigation Using Sonor Mapping and Neural Networks
Authors: Yun Won Soo , Cho Dong Woo , Baek Yoon Su
Published: February 2008

This paper presents a new path planning algorithm for safe navigation of a mobile robot in dynamic as well as static environments. The certainty grid concept is adopted to represent the robot’s surroundings and a simple sensor model is developed for fast acquisition of environmental information. The proposed system integrates global and local path planning and has been implemented in a partially known structured environment without loss of generality for an indoor mobile robot. The global planner finds the initial path based on Dijkstra’s algorithm, while the local planning scheme uses three neural networks to follow the initial global path and avoid colliding with static and moving obstacles. Effectiveness of these algorithms is illustrated through simulation and experiment using a real robot. The results show that the proposed algorithm can be efficiently implemented in a time varying environment.
Active Control of a High-Speed Pantograph
Authors: O’Connor D. N. , Eppinger S. D. , Seering W. P. , Wormley D. N.
Published: February 2008

The design and performance of an active controller for a pantograph which collects current for a high-speed train are considered. A dynamic model of the pantograph/catenary system is described and control objectives are established. A design which incorporates a frame-actuated controller and requires only a single measurement is described. Over an array of train speeds, the contact force variation with the actively controlled pantograph is 50 percent less than for the equivalent passive pantograph system.
Vibration Control of Smart Structures by Using Neural Networks
Authors: Yang S. M. , Lee G. S.
Published: February 2008

Smart structure with build-in sensor(s) and actuator(s) that can actively and adoptively change its physical geometry and properties has been considered one of the best candidates in vibration control applications. Implementation of neural networks to system identification and vibration suppression of a smart structure is conducted in this paper. Three neural networks are developed, one for system identification, the second for on-line state estimation, and the third for vibration suppression. It is shown both in analysis and in experiment that these neural networks can identify, estimate, and suppress the vibration of a composite structure by the embedded piezoelectric sensor and actuator. The controller is also shown to be robust to system parameter variations.
The Role of Environment Dynamics in Contact Force Control of Manipulation Robots
Authors: Vukobratovic´ Miomir
Published: February 2008

This paper draws attention to the role of the environment dynamics in force control of robots interacting with dynamic environment. Traditional control approaches are based on restrictive assumptions, on environment properties and cannot assure stability in general. In this paper, the role of the dynamic environment is emphasized and a contribution to understanding the mechanism of elasto-dynamic interaction is given. In this paper, it has been assumed that the force is stabilized and then local stability conditions of the whole system are studied. The study has been made on basis of a linearization of the closed-loop system.
A Multivariable Decoupling Design of an ROV Depth Control System (A Direct Adaptive Fuzzy SMC Approach)
Authors: Trebi-Ollennu A. , Stacey B. A. , White B. A.
Published: February 2008

This paper describes, an Adaptive Fuzzy Sliding Mode Control (AFSMC) method applied to the control of the vertical motion of a minehunting Remotely Operated Vehicle (ROV). The effects of parameter variation of the ROV are considered, and performance and robustness to uncertainty are assessed. The proposed control methodology addresses the fundamental issues of stability, performance requirements, and model variations within a single framework. The effectiveness of the technique is demonstrated by its ability to decouple pitch and heave of the ROV subjected to parameter variations.
Sampled-Data Indirect Adaptive Control of Bioreactor Using Affine Radial Basis Function Network Architecture
Authors: Gorinevsky Dimitry
Published: February 2008

This paper considers a problem of bioreactor control, which is formulated in Anderson and Miller (1990) and Ungar (1990) as a benchmark problem for application of neural network-based adaptive control algorithms. A completely adaptive control of this strongly nonlinear system is achieved with no a priori knowledge of its dynamics. This becomes possible thanks to a novel architecture of the controller, which is based on an affine Radial Basis Function network approximation of the sampled-data system mapping. Approximation with such net-work could be considered as a generalization of a standard practice to linearize a nonlinear system about the working regime. As the network is affine in the control components, it can be inverted with respect to the control vector by using fast matrix computations. The considered approach includes several features, recently introduced in some advanced process control algorithms. These features—multirate sampling, on-line adaptation, and Radial Basis Function approximation of the system nonlinearity—are crucial for the achieved high performance of the controller.
An Experimental Study of Resolved Acceleration Control of Robots at Singularities: Damped Least-Squares Approach
Authors: Kirc´anski M. , Kirc´anski N. , Lekovic´ D. , Vukobratovic´ M.
Published: February 2008

Most of the robot task space control methods based on inverse Jacobian matrix suffer from instability in singular regions of workspace. Methods based on damped least-squares algorithm (DLS) for matrix inversion have been developed but not experimentally confirmed. The application of DLS method at the kinematic control level has been reported in (Chiaverini et al., 1994). In this article, a modified DLS method combined with the resolved-acceleration control scheme, is experimentally verified on two degrees of freedom of a PUMA-560 robot. In order to decrease the position error introduced by the damping, only small singular values are damped, in contrast to the conventional damping method were all the singular values are damped. The symbolic expressions of the singular value decomposition of the Jacobian matrix were used, to decrease the computational burden.
Robot Obstacle Avoidance in n-Dimensional Space Using Planar Harmonic Artificial Potential Fields
Authors: Guldner Ju¨rgen , Utkin Vadim I. , Hashimoto Hideki
Published: February 2008

Autonomous operation of robots requires on-line obstacle avoidance. A wide-spread tool for obstacle avoidance, employed both for mobile robots and for manipulator arms, is the artificial potential field method. This paper extends previous results for planar problems to the general n-dimensional case. A significant decrease in computational complexity is achieved by projecting the n-dimensional workspace into a two-dimensional subspace called the operation plane. Furthermore, only the closest obstacle is taken into account when designing the artificial potential field. The effects of the required switching between potential fields of different obstacles are examined using sliding mode theory. A tracking controller is presented which allows exact following of the gradient of the artificial potential field. The methodology is illustrated with several numerical examples.
Modeling of Vapor Compression Cycles for Multivariable Feedback Control of HVAC Systems
Authors: He Xiang-Dong , Liu Sheng , Asada Haruhiko H.
Published: February 2008

This paper presents a new lumped-parameter model for describing the dynamics of vapor compression cycles. In particular, the dynamics associated with the two heat exchangers, i.e., the evaporator and the condenser, are modeled based on a moving-interface approach by which the position of the two-phase/single-phase interface inside the one-dimensional heat exchanger can be properly predicted. This interface information has never been included in previous lumped-parameter models developed for control design purpose, although it is essential in predicting the refrigerant superheat or subcool value. This model relates critical performance outputs, such as evaporating pressure, condensing pressure, and the refrigerant superheat, to actuating inputs including compressor speed, fan speed, and expansion valve opening. The dominating dynamic characteristics of the cycle around an operating point is studied based on the linearized model. From the resultant transfer function matrix, an interaction measure based on the Relative Gain Array reveals strong cross-couplings between various input-output pairs, and therefore indicates the inadequacy of independent SISO control techniques. In view of regulating multiple performance outputs in modern heat pumps and air-conditioning systems, this model is highly useful for design of multivariable feedback control.
Robustness of Adaptive Rotor Vibration Control to Structured Uncertainty
Authors: Knospe C. R. , Tamer S. M. , Fedigan S. J.
Published: February 2008

Recent experimental results have demonstrated the effectiveness of adaptive open-loop control algorithms for the suppression of unbalance response on rotors supported in active magnetic hearings. Herein, tools for the analysis of stability and performance robustness of this algorithm with respect to structured uncertainty are derived. The stability and performance robustness analysis problems are shown to be readily solved using a novel application of structured singular values. An example problem is presented which demonstrate the efficacy of this approach in obtaining tight bounds on stability margin and worst case performance.
Zero Phase Error Tracking System With Arbitrarily Specified Gain Characteristics
Authors: Yamada Manabu , Funahashi Yasuyuki , Fujiwara Shin-ichi
Published: February 2008

This paper considers a design problem of discrete-time preview feedforward controllers such that the gain characteristics of the overall system is within an arbitrarily specified bound subject to the zero phase error condition for a plant having nonminimum phase zeros. In order to solve this problem, a feedforward controller termed Optimal-Feedforward Controller with Zero Phase Error Tracking Controller (Optimal-FCZPETC) is introduced. With this controller, the phase characteristics of the overall system is zero for all frequencies and the maximum value of the gap between the gain of the overall system and unity, which is ideal gain characteristics, is minimized under given preview steps. The choice of the preview steps is an unsolved problem. In this paper, we investigate the Optimal-FCZPETC from the viewpoint of the preview steps. The contribution is to give explicitly the minimum value of the maximum gap between the gain of the overall system and unity for given preview steps and to show that the minimum value can be made arbitrarily small as the preview steps increase. As a result, a simple algorithm is proposed to find the minimum preview steps such that the gain characteristics of the overall system is within an arbitrarily specified bound. The effectiveness is shown by simulation results.
Assessing the Potential for Energy Regeneration in Dynamic Subsystems
Authors: Jolly M. R. , Margolis D. L.
Published: February 2008

The utility of many controlled dynamic systems is impaired by excessive power consumption and related hardware. In this paper, the potential for energy regeneration in a broad class of dynamic subsystems is considered. In doing so, we consider the potential for a dynamic subsystem to be self-contained and self-sustaining. The development begins with a definition for subsystem passivity and new definitions for subsystem regenerativity and activity. While diagnosis of a passive subsystem can be made simply through observation of the isolated subsystem, it is shown that the diagnosis of a subsystem as either regenerative or active, in general, requires the computation of the subsystem’s average power absorption. Consequently, the accuracy of such a diagnosis depends upon the level of knowledge regarding the overall system and its inputs. Simple mass suspension examples are provided to demonstrate the developed theory.
An LQ Controller With a Prescribed Pole Region—A Data-Based Design Approach
Authors: Chan Jenq-Tzong H.
Published: February 2008

In this paper, we present a modified method of data-based LQ controller design which is distinct in two major aspects: (1) one may prescribe the z-domain region within which the closed-loop poles of the LQ design are to lie, and (2) controller design is completed using only plant input and output data, and does not require explicit knowledge of a parameterized plant model.
Coupling Between the Modeling and Controller-Design Problems—Part II: Design
Authors: Brusher G. A. , Kabamba P. T. , Ulsoy A. G.
Published: February 2008

In Part I of this paper, the coupling between the modeling and controller-design problems was quantified in terms of the size of the set of models from which satisfactory controllers may be derived. Herein, the significance of this coupling in controller design is exploited in the formulation of a simultaneous approach to modeling and controller design. The goal is to minimize the worst-case control effort subject to constraints on worst-case performance. It is proven that, by allowing the controller-design model and the controller to vary simultaneously, this approach yields a potential reduction in the control effort required to satisfy the prescribed performance goals in comparison to the traditional sequential approach. Two simple examples illustrating the benefits of this approach are also presented.
Transient Error Detection During UDUT Covariance Calculations Using Algorithm Based Fault Tolerance
Authors: Young G. E. , Moan M. R. , Misawa E. A.
Published: February 2008

Algorithm based fault tolerance is studied for use with linear estimation algorithms such as the Kalman filter. Emphasis is placed on the study of algorithm based fault tolerance used in conjunction with the UDUT covariance calculation. A real-time simulation has been performed in a VMEbus environment utilizing a single board computer and a commercial real-time operating system.
Sensitivity Reduction of Constraint Forces and Position Control for Mechanical Descriptor Systems
Authors: Jiang Dan-chi , Yan Wei-Yong , Teo K. L.
Published: February 2008

This paper deals with the position and force control for mechanical systems with holonomic constraints. Our concern is the design of a feedback controller such that the closed-loop system has a satisfactory transient response and is less sensitive to various types of disturbances. Using an appropriate transformation, the constrained system is converted into an unconstrained system of lower order. Then, an H∞, control problem involving the reduced system is formulated. In the case of state feedback, a systematic design procedure for solving the problem is presented, where the key step is the solution of an algebraic Riccati equation. An example is given to illustrate the effectiveness of the proposed method.
A Dynamic Evaluation Technique for Liquid Flow Meters Based on Hydraulic Line Dynamics
Authors: Peng Guangzheng , Zhao Tong
Published: February 2008

A new concept for the evaluation of flowmeter dynamic response is presented. A technique based on hydraulic line dynamics is applied to achieve accurate measurements of the reference flowrate. The major components in the equipment used in experimental verification of the theory were a test pipe, a pulsating flow generator, three pressure transducers, an A/D converter, and a microcomputer system. This equipment allowed the dynamic characteristics of a flowmeter to be investigated in both the time and frequency domains. Comparisons of flowrates measured using the line dynamic technique and the same flowrates recorded by the flowmeter are presented. The results confirm the feasibility and practicability of the dynamic line technique for measuring rapidly varying flows.
Application of a Least Squares Lattice Algorithm to Active Noise Control for an Automobile
Authors: Sano Hisashi , Adachi Shuichi , Kasuya Hideki
Published: February 2008

The purpose of this paper is to propose an alternative approach to active noise control (ANC) using the least squares lattice (LSL) algorithm. Typically, in ANC applications, the least-mean-square (LMS) algorithm has been used because of its simplicity. However, the LMS algorithm has the disadvantage of slow convergence speed in the case of broadband noise, such as the road noise present in the passenger compartment of automobiles traveling on rough road surfaces. In order to solve this problem, the LSL algorithm for ANC is considered. By computer simulation using actual car data, the LSL algorithm proves to be more effective than the LMS one.