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

Abstract: Dimensional measurements obtained with Coordinate Measuring Machines (CMMs) are negatively affected by self-induced structural vibrations. In this paper, a control strategy that reduces the structural vibrations in a CMM is outlined and experimentally demonstrated. The control strategy, designated the Feedforward Filter, is developed by establishing the relationship between contemporary controller input shaping techniques and traditional notch filtering methods. Issues on both robustness and multiple mode vibrations are addressed. Controller input development takes place in the discrete time domain. This method provides results identical to those for optimal command input preshaping obtained through non-linear programming methods and requires considerably less computational effort. Experimental results show a 50 percent reduction in the peak-to-peak magnitude of structural vibrations as compared to unshaped bang-bang trajectories.

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

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

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

Abstract: The problem of adaptive noise cancellation in an acoustic duct is discussed. An adaptive controller design approach based on parametrizing the set of stabilizing controllers using the Youla parametrization and tuning the Youla parameter to achieve regulation was presented in a companion paper [3], Three controller adaptation algorithms are imple­ mented to solve the noise cancellation problem in an acoustic duct. The experimental results indicate a mixed performance for each of the adaptation algorithms, with good performances observed only in some frequency ranges. The discrepancy between the expected and the observed performances is attributed to unmodeled nonlinearities in the speakers.

Abstract: In biaxial contour tracking applications, the main concerns are the tangential and the contour errors. This paper presents a tangential-contouring controller to achieve effect and decoupled control of these concerns. The proposed controller is based on a coordinate transformation between the X-Y frame and a tangential-contouring (T-C) frame that is defined along the contour. Experimental evaluation for the proposed controller is conducted on a biaxial positioning table.

Abstract: This paper presents the active vibration control of an axially moving string system through a mass-damper-spring (MDS) controller at its right-hand side (RHS) bound-ary. A nonlinear partial differential equation (PDE) describes a distributed parameter system (DPS) and directly selected as the object to be controlled. A new boundary control law is designed by sliding mode associated with Lyapunov method. It is shown that the boundary feedback states only include the displacement, velocity, and slope of the string at RHS boundary. Asymptotical stability of the control system is proved by the semigroup theory. Finally, finite difference scheme is used to validate the theoretical results.

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

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

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

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

Abstract: A worst-case evaluation method is presented in this paper. The objective of this method is to identify worst-case maneuvers so that the performance of dynamic systems under extreme conditions can be evaluated. Depending on the dynamics and information structure of the system, the worst-case evaluation problems can be classified into four sub-cases. Classical optimal control and game theories are used to construct algorithms to obtain linear solutions analytically. When the plant and/or the control algorithm is nonlinear, the true worst-case solution can be obtained from numerical methods. Two case-study examples are presented. A linear example presents the time domain and frequency domain results comparing the four linear algorithms. The generation of the worst-case steering and braking maneuver to rollover an articulated vehicle is then presented as a "real" application example. Interested reader can download the PC-based software and generate the simulation results by visiting the website

Abstract: This technical brief addresses the vibration control of a flexible beau structure using ER ( electro-rheological) dampers. A clamped-clamped flexible beam system supported by two short columns is considered. An ER damper which is operated in shear mode is designed on the basis of Bingham model of the ER fluid, and attached to the flexible beam. After deriving the governing equation of motion and associated boundary conditions, a sliding mode controller is formulated to effectively suppress the vibration of the beam caused by external forces. In the formulation of the controller, parameter variations such as frequency deviation are treated to take into account the robustness of control system. The effectiveness of the proposed control system is confirmed by both simulation and experimental results.

Abstract: One of the major difficulties in neural network applications is the selection of the parameters in network configuration and the coefficients in learning rule for fast convergence. This paper develops a network design by combining the Taguchi method and the back-propagation network with an adaptive learning rate for minimum training time and effective vibration suppression. Analyses and experiments show that the optimal design parameters can be determined in a systematic way thereby avoiding the lengthy trial-and-error.

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

Abstract: In this paper, we consider the system modeled by an axially moving string and a mass-damper-spring (MDS) controller, applied at the right-hand side (RHS) boundary of the string. We are concerned with the nonlinear string and the effect of the control mechanism. We stabilize the system through a proposed boundary velocity feedback control law. Linear and nonlinear control laws through this controller are proposed. In this paper, we find that a linear boundary feedback caused the total mechanical energy of the system to decay an asymptotically, but it fails for an exponential decay. However, a nonlinear boundary feedback controller can stabilize the system exponentially. The asymptotic and exponential stability are verified.

Abstract: This paper deals with the problem of measuring the inertia tensor of rigid bodies. An original approach is adopted, different from classical modal analysis techniques. The rigid body is forced by a spatial mechanism to rotate around different axes. Once the mechanism is calibrated, i.e., its inertia and stiffness matrices are known, the inertia tensor of the rigid body may be determined by measuring the frequencies of the small oscillations around the selected axes and then solving a least-squares identification problem. Two prototypes of the spatial mechanism were built. The first was used to perform tests and to measure the inertia tensor of some compressors for domestic refrigeration. The second was constructed to measure the inertia tensor of large mechanical systems.

Abstract: In this research, the control and containment forces and moments acting on the swash plate of an axial-piston pump are examined. From a practical standpoint, swash plate control and containment devices take on many different designs; however, they must all resist the same essential moments and forces that attempt to dislocate the swash plate from its proper position. By considering the basic machine design without its control and containment mechanisms, this work generally derives the needed forces and moments for insuring proper swash-plate motion and thereby gives the designer of these machines a useful tool for designing control and containment devices of any type. The success of the actual control and containment devices will be measured by how well they exert the proper forces and moments on the swash plate which are presented here.

Abstract: The control structure for automated vehicles in an Automated Highway System is based on the idea of multiple-surface sliding control. The upper surface determines a desired net torque while the lower surface determines the required throttle angle or brake pressure needed to achieve the desired torque. This paper presents an upper surface control law for performing longitudinal transition maneuvers. The maneuvers use desired velocity trajectories which are based on maintaining safety and comfort throughout the maneuver. The control law chosen is a sliding controller due to the nonlinearities in the dynamics and the uncertainties in the parameters. Adaptive techniques were also implemented to help improve the velocity tracking. The controller was implemented on experimental vehicles and tested at highway speeds.

Abstract: A method for generating on-off command profiles for flexible systems is presented. The command profiles move a system without residual vibration while using a specified amount of actuator fuel, Robustness to modeling errors can be incorporated into the design of the command signals. Techniques are presented that facilitate implementation and indicate prudent choices for the amount of fuel to be used. The method is compared to other command generation techniques that balance fuel usage and slew time.

Abstract: The tracking control problem of robot manipulator is considered in this paper. A sliding mode controller design with global invariance is proposed using the concept of extended system and feedback linearization. The sliding surface is assigned such that the sliding mode motion will occur while the proposed control law is applied. This results in a system with global invariance. The stability and performance of the resulting system can be guaranteed by the proposed systematic design procedure.

Abstract: Because the conventional formula for turbulent orifice flow rate has an infinite derivative when the pressure difference is zero, ODE solvers may fail during numerical simulation of fluid power circuits. To remedy this, a two-regime orifice flow formula is proposed in which an empirical polynomial laminar flow function is used for small pressure differences. The proposed formula has a smooth transition between laminar and turbulent regimes, and its derivative does not have any singularities.

Abstract: Dynamic simulation of systems, where the differential equations of the system are solved numerically, is a very important tool for analysis of the detailed behavior of a system. The main problem when dealing with large complex systems is that most simulation packages rely on centralized integration algorithms. For large scale systems, however, it is an advantage if if the system can be partitioned in such a way that the parts can be evaluated with only a minimum of interaction. Using transmission line models, with distributed parameters, physically motivated pure time delays are introduced in the communication between components. These models can be used to represent both lines in a hydraulic system and springs in mechanical systems. As a result, components and subsystems can be simulated more independently of each other. In this paper it is shown how flexible joints based on transmission line modeling (TLM) with distributed parameters can be used to simplify modeling of large mechanical link systems interconnected with other physical domains. Furthermore, it provides a straightforward formulation for parallel processing.

Abstract: This paper presents robust vibration and position tracking control of a flexible smart structure featuring a piezoceramic actuator. A cantilever beam structure with a surface-bonded piezoceramic actuator is proposed, and its governing equation of motion and associated boundary conditions are derived from Hamilton's principle, The transfer function from control input voltage to output displacement is then established in Laplace domain considering the hysteresis behavior as a structured plant uncertainty. A robust QFT (quantitative feedback theory) compensator is designed on the basis of a stability criterion which prescribes a bound on the peak value of an M-contour in the Nichols chart (NC). In the formulation of the compensator disturbance rejection specification and tracking performance bounds are specified to guarantee the robustness of the system to the plant uncertainty and external disturbance. A prefilter is also designed for the improvement of step and sinusoidal tracking control performances. Forced-vibration and tracking control performances are investigated through computer simulation and experimental implementation in order to demonstrate the efficiency and robustness of the proposed control methodology.

Abstract: In this paper we will present a model for an array of microcantilevers that are used in Atomic Force Microscopy and nano-scale manufacturing. The microcantilevers are connected to each other through a common base, and are individually actuated. The sensors are also integrated on each microcantilever. We consider the problem of controlling a tightly packed array of identical microcantilevers that are dynamically coupled. This system is an example of a spatially-invariant system with a distributed array of sensors and actuators. We exploit the spatial invariance of the problem to design optimal H 2 controllers for this array. An analytic expression for the optimal controller is derived in the transformed domain, and estimates of the coupling range of the controller is obtained.

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

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

Abstract: Zero dynamics is an important feature in system analysis and controller design. Its behavior plays a major role in determining the performance limits of certain feedback systems. Since the intrinsic zero dynamics can not he influenced by feedback compensation, it is important to design physical systems so that they poss red ero dynamics. In the Part I paper, a method is proposed to derive the zero dynamics of SISO systems from bond graph models. Using this approach, the design of physical systems, including the consideration of zero dynamics, can be performed in a systematic way. In this paper, the extension of the proposed method for MIMO systems is presented. It is shown that for MIMO systems the input-output configurations determine the existence of vector relative degrees. If a system has a vector relative degree, it's zero dynamics can be identified by a straightforward extension of the proposed method. If a system does not have a vector relative degree, a dynamic extension procedure may be used to fix the structure. By doing so, the zero dynamics can still be identified in a similar manner. It is also shown that if the input-output configurations are ill-designed, not only the relative degrees do not exist, but also the zero dynamics can not be reasonably defined. In that case, independent tracking controls for all the outputs are impossible. Therefore, the results in this paper provide a guideline for the design of the input-output configurations as well as the zero dynamics of MIMO systems.