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In this paper, we propose a new coupled dynamical model of a horizontal axis wind turbine (HAWT). The proposed model takes into consideration the dynamic coupling of the flexible tower with both bending and torsion of the flexible blades. This model also accounts for the dynamics of an additional point mass located in one of the blades to simulate a crack. In addition, a finite element model (FEM) analysis along with an experimental study is conducted in this research to validate the modal analysis of a HAWT prototype. Data from the analytical, numerical, and experimental investigations were collected and showed comparable findings. Using the analytical model, the modal analysis and the steady-state response of the HAWT prototype are performed for two configurations: with and without a crack. In this paper, we also propose a new model-based technique for the detection of cracks in the HAWT.

Developing a flywheel energy storage system (FESS) with permanent magnetic bearing (PMB) and spiral groove bearing (SGB) brings a great challenge to dynamic control for the rotor system. In this paper, a pendulum-tuned mass damper is developed for 100 kg-class FESS to suppress low-frequency vibration of the system; the dynamic model with four degrees-of-freedom is built for the FESS using Lagrange's theorem; mode characteristics, critical speeds, and unbalance responses of the system are analyzed via theory and experiment. A comparison between the theoretical results and the experiment ones shows that the pendulum-tuned mass damper is effective, the dynamic model is appropriate, and the FESS can run smoothly within the working speed range.

This paper proposes a novel computationally efficient dynamics modeling approach for down-hole well drilling system. The existing drilling modeling methods are either computationally intensive such as those using finite element method (FEM) or weak in fidelity for complex geometry such as those using transfer matrix method (TMM). To take advantage of the benefits of FEM and TMM and avoid their drawbacks, this paper presents a new hybrid method integrating both of the aforementioned modeling approaches, enabled by the unique structural geometry of the drilling system. The new method is then applied to the down-hole well drilling system modeling, incorporating the dynamics of top drive, drill-string, bottom-hole-assembly (BHA), and bit–rock interaction. The hybrid integration approaches for both the axial and torsional dimensions are explicitly derived, and we also give directions on how to resolve those for flexural dimension. To this end, numerical simulation results are presented to demonstrate the effectiveness of the proposed hybrid modeling approach.

In differential drive robots, wheel slip severely affects the ability to track a desired motion trajectory and the problem is exacerbated when differential drive robots are used in applications involving coordination of multiple robots. This problem is investigated and, based on the wheel–ground traction forces, a simple slip avoidance control strategy is discussed. Differential drive robots with two driven wheels and one or more ball-type caster wheels are considered. The traction forces between the wheels and the ground surface are determined by assuming rigid wheel, rigid ground interaction. These traction forces are used to determine the maximum value of the input wheel torque that can be applied on the wheel before it slips. To avoid wheel slip, this limiting torque value is used to set a saturation limit for the input torque computed by a trajectory tracking controller. Stability of the closed-loop system with the slip avoidance strategy is shown. Experiments are conducted with this strategy using a single robot as well as multiple robots in a platoon. A representative sample of the experimental results is presented and discussed.

This paper presents the analysis, design, and simulation of a novel microrobotic platform that is able to perform translational and rotational sliding with submicrometer positioning accuracy and develop velocities up to 1.5 mm/s. The platform actuation system is novel and based on centripetal forces generated by vibration micromotors. The motion principle is discussed in detail, and the dynamic model of the platform and of its actuation system is developed. Analytical expressions for the distinct modes of operation of the platform are derived and used to provide system design guidelines. Simulations are performed that verify the analytical results, demonstrate the platform capabilities, and examine its transient response. The microrobot design is simple, compact, and of low cost. In addition, the energy supply of the mechanism can be accomplished in an untethered mode using simple means, such as single-cell batteries. DOI: 10.1115/1.2168472

A procedure for determining the cooperative system nominal motion whereby the system’s desired motion belongs to a set of nominal motions, is proposed. The procedure originates from the solution of the elastic structure cooperative motion taking into account all specific properties of the cooperative manipulation. The starting basis of the procedure is determined by some essential properties of the mathematical model of the dynamics of the cooperative manipulation of the object by the nonredundant manipulators with 6 degrees of freedom (DOFs), whereby the problem of the force indefiniteness is solved by introducing elastic properties for a part of the cooperative system.

Cutting brushes are used at relatively low speeds by various municipal vehicles and in particular road sweeping units. As the name suggests such brushes are designed to “cut” through debris, especially compacted sand or similar matter. The main deflection plane of a bristle (or tine) is along the mount radius, making the tines very stiff in the direction of rotation, hence the cutting action when the brush is rotated. Exploring the literature shows that very little is known, or understood, about the operation of brushes for mechanical sweeping. In this paper a pseudo-static discretized model is developed to investigate the deformations and forces acting on brushes during ideal operation of a horizontal brush on a flat plane. Due to the numerous different sweeper brushes on the market, one common configuration is used as the basis of the model and the paper will detail only the characteristics of this brush. The brush to be investigated is a “cutting brush,” introduced above, where the tines can only deflect along the mount radius. Having developed a model it is used to predict the forces and torques generated within a horizontally rotating brush. The influence of centrifugal force is analyzed although transient effects are neglected and steady state conditions assumed. The predictions of the model are compared to practical results taken from a test rig and the validity of the model is discussed. Agreement between the model and the practical results will be shown to be good, considering the complexities and practical realities involved in analyzing any system which is friction dependent.

In this paper, an analysis is provided for the steering of a long, warped web that is transported between two rollers. The web is modeled using the Timoshenko beam theory, which admits small amounts of elastic bending and transverse shearing. Closed-form solutions are obtained for three commonly encountered forms of in-plane imperfection: (1) a splice, (2) a sinusoidal warpage, and (3) a cambered web with a constant radius-of-curvature. The fact that partial wrinkling in the web can affect the lateral dynamics is demonstrated in a simple example. This analysis reveals information on the phenomenon of weave regeneration and will be useful to designers of transport systems who wish to control the lateral tracking of webs with geometrical flaws.

This paper presents kinematic and dynamic analysis of a holonomic vehicle with continuously-variable transmission. Four ball wheels, independently actuated by DC motors, enable for moving the vehicle in any direction within the plane and rotating it around its center. The angle between the two beams holding the balls can be changed to alter the gear ratio and other dynamic characteristics of the vehicle. This feature is exploited in augmenting the vehicle stability, optimizing output power, selecting an appropriate gear ratio, and in impedance matching. A simple adaptive friction-compensation-based controller is proposed to handle the complex friction properties.

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.

We treat the question of position and force control of a three-axis elastic robotic system on a constraint surface based on nonlinear inversion of an input-output map and linear feedback stabilization. Unlike the rigid robots, the feedback linearizing control of end point motion gives rise to unstable zero dynamics. Instability of zero dynamics is avoided by controlling a parameterized output vector corresponding to a point close to the end point of the arm. Zero dynamics are stable or almost stable as long as the parameter in the output vector does not exceed a critical value. Using the inverse controller, the control of the force and the position of the end point is possible while the end effector moves on the constraint surface. However, this excites the elastic modes. For the final capture of the terminal state and vibration suppression, a linear stabilizer is designed. Simulation results are presented to show that in the closed-loop system trajectory and force control on the constraint surface is accomplished.

A low-speed axial research compressor has been fitted with movable inlet guide vanes to allow for feedback stabilization of rotating stall. A model exists whose structure captures the input-output behavior, and stabilization of rotating stall is possible using this model. Quantitative identification of the parameters in the rotating stall model requires the ability to identify MIMO dynamics, which may be unstable, during closed loop operation. The ‘instrumental variable’ technique is presented as the basic approach to this problem. The necessary extensions to the basic technique are discussed, and the resulting algorithm is applied. Experimental results are presented which verify that the methodology yields useful estimates.

This paper presents a semiactive suspension control algorithm to reduce dynamic tire forces and it includes the development and application of observers for bilinear systems with unknown disturbances. The peak dynamic tire forces, which are greatly in excess of static tire forces, are highly dependent on the dynamic characteristics of vehicle suspensions. One way to reduce dynamic tire forces is to use advanced suspension systems such as semiactive suspensions. Semiactive control laws to reduce dynamic tire forces are investigated and a bilinear observer structure for bilinear systems with unknown disturbances is formulated such that the estimation error is independent of the unknown external disturbances and the error dynamics are stable for bounded inputs. The motivation for the development of a disturbance decoupled bilinear observer comes from the state estimation problem in semiactive suspensions. An experimental study on the performance of a semiactive suspension to reduce the dynamic tire forces is made via a laboratory vehicle test rig. The semiactive suspension has been implemented by using a modulable damper, accelerometers and a personal computer. Experimental studies show that the performance of the semiactive suspension is close to that of the best passive suspension for all frequency ranges in the sense of minimizing the dynamic tire forces and that the dynamic tire force can be replaced by the estimated one. The dynamic tire forces for both passive and semiactive control test cases are compared to show the potential of a semiactive suspension to reduce the dynamic tire forces.

A desire to improve the positioning accuracy of ball screws prompted an investigation into the dynamics of nanometer motion. Characterization of the ball screw indicated that nanometer motion is possible prior to friction breakaway via elastic deformation of the frictional contacts while macroscopic motion involves slipping across the friction interfaces. The observed dynamics are nonlinear, and consequently result in inconsistent and unpredictable closed-loop response while under PI position control. The ball-screw can be modeled in two stages: The microdynamic stage includes “elastic” friction while the macrodynamic stage incorporates kinetic (sliding) friction. A two-stage model reference adaptive control (MRAC) strategy is adopted and a Lyapunov design technique is applied to derive the adaptive laws. Experimental results obtained via a DSP implementation of the adaptive controller indicate that the each stage of the adaptive control performs well within the respective dynamic regions, but performance deteriorates as either controller is operated near the boundary of the regions.

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

A research tool was developed for the dynamics and control of a single-flexible-link arm based on the Equivalent Rigid Link System (ERLS) dynamic model and the inverse dynamics of the arm and the actuator. The arm moved in a vertical plane and was actuated by an electrohydraulic motor. The required torque was computed based on the inverse dynamics of the ERLS model. The driving current was then predicted by the inverse actuator dynamics. This paper also presents a 16-bit microcomputer-based low-cost implementation of a nonlinear motion tracking control. The dynamic behavior of the control system was studied through the computer simulation and the experiment. Furthermore, the superiority of the flexible-body control was also proved through the comparison to the rigid-body control.

The purpose of this investigation is to study the formulation of equations of motion for flexible robots containing translationally moving elastic members that traverse a finite number of distinct support points. The specific system investigated is a two-degree-of-freedom manipulator whose configuration is similar to that of the Stanford Arm and whose translational member is regarded as an elastic beam. Equations of motion are formulated by treating the beam’s supports as kinematical constraints imposed on an unrestrained beam, by discretizing the beam by means of the assumed modes technique, and by applying an alternative form of Kane’s method which is particularly well suited for systems subject to constraints. The resulting equations are programmed and are used to simulate the system’s response when it performs tracking maneuvers. The results provide insights into some of the issues and problems involved in the dynamics and control of manipulators containing highly elastic members connected by prismatic joints.

This article describes the dynamics, control, and stability of extenders, robotic systems worn by humans for material handling tasks. Extenders are defined as robot manipulators which extend (i.e., increase) the strength of the human arm in load maneuvering tasks, while the human maintains control of the task. Part of the extender motion is caused by physical power from the human; the rest of the extender motion results from force signals measured at the physical interfaces between the human and the extender, and the load and the extender. Therefore, the human wearing the extender exchanges both power and information signals with the extender. The control technique described here lets the designer define an arbitrary relationship between the human force and the load force. A set of experiments on a two-dimensional non-direct-drive extender were done to verify the control theory.

A measurement oriented formulation of rigid body dynamics is applied to a special class of planar linkage systems. It leads to a diagonal moment of inertia matrix, and thus simplifies the feedforward computations in the controller. On the other hand, if measurements are not available or measurements are not allowed, the computational burden shifts to the feedback computation of the generalized or internal forces. This formulation may find applications in off-line digital computer simulations and on-line control of the rigid body systems via the inverse dynamics methods. It may also underly computations in natural and biological systems that are rich with sensory modalities and processes. The computational burden in this model is shifted from the inverse of moment of inertia matrix to the derivation of the forces of constraint, contact, connection, internal or generalized. When these forces are available from measurements, the computations are indeed reduced and consequently on-line control problems are rendered easier. As a consequence of this representation the problems of transmission delay, and predictive compensation become important as is shown via an example. The investigation of the range of intermediate representations where computations and measurements are combined remains a fertile subject.

The “exact” and pole/zero transfer functions are developed for a flexible beam-like single link arm with actuator on one end and payload on the other. This model represents a broader class of actuator hub and payload mass properties than is found in prior literature. The dependence of dynamics on the hub and payload inertia characteristics are studied and graphs are provided to facilitate estimation of poles and zeroes for any similar plant. It is shown that a 10:1 reduction in fundamental frequency and substantial change in the zeroes results from variations in payload through a practical range. Payload rotary inertia is shown to cause a qualitative change in the arm tip zeroes resulting in loss of observability/controllability in some cases. Results provide insight into the two-link problem and it is shown that complex values zeroes may result if the second arm is allowed to “fold back.” Implications to plant modeling and control design are discussed including sensor placement and model order reduction issues. Analytical results are compared to those measured on an experimental arm and show very good agreement in modal frequency and shape.

A nonlinear, lumped parameter pantograph model including geometric and coulomb friction nonlinearities and variable stiffness has been developed. The model performance has been compared with experimental dynamic response data measured on a prototype pantograph. Responses of the model and the experimental data including subharmonic and harmonic resonances are in close agreement for motions excited by comparable forcing functions for input frequencies of 0 to 12 Hz. The model has been used to identify the primary parameters and nonlinear effects which influence dynamic pantograph performance.

This is a dynamic analysis of a three-mass, hinged beam model representing a standing human struck suddenly with a posterior, horizontal, step impact force. The results of parametric studies, presented in terms of nondimensional system variables, show the essential features of the dynamic moment responses in the lower leg. Included are the effects of the distribution of body mass, the location of the impact force, and the base fixity, with and without slip. Closed-form results show that the point of impact is not always the point of maximum bending moment on the lower leg. For step impact loads applied near the knee joint, peak moments are predicted near the midlength of the lower leg, the location coincident with about half of the observed fractures to the tibia and fibula of pedestrians struck by car bumpers near the knees.

Five methods are outlined in this paper for determining the screw parameters of the instantaneous motion of rigid bodies from given velocity and position data of three noncollinear points. The five methods are compared on the basis of their computational efficiency and accuracy. It is found that the method based on vector algebra is much more efficient computationally than any of the other four methods, but has some limitations of applicability. In terms of accuracy, the methods are equivalent when working with exact data. It is recommended that the method based on vector algebra be used for computing screw parameters from position and velocity data when this computation is performed frequently, as in the case of trajectory planning for robotics application. But method hopping be employed where inexact data are used, employing the method which gives the best speed/accuracy combination.

A feedback control problem for a constrained mechanism is formulated and solved. The mechanism is controlled by forces applied to the mechanism which are to be adjusted according to a linear control law, based on feedback of the positions and velocities of the mechanism and feedback of the constraint force on the mechanism. The control objective is to achieve accurate and robust local regulation of the motion of the mechanism and of the constraint force on the mechanism. Derivation of a suitable control law is significantly complicated by the nonclassical nature of the differential-algebraic model of the constrained system and by the nonlinear characteristics of the model. The control design approach involves use of a certain nonlinear transformation which leads to a set of decoupled differential-algebraic equations; classical control design methodology can be applied to these latter equations. An example of a planar mechanism is studied in some detail, for two different regulation objectives. Specific control laws are developed using the described methodology. Comparisons are made with a closed loop system, where the control law is derived without proper consideration of the constraint force. Computer simulations are presented to demonstrate the several closed-loop properties.

The paper describes a general purpose digital computer model for the analysis of the pumping dynamics of positive displacement pumps employing self-acting valves. This model is verified by comparison with experimental tests on a diaphragm separator pump. Predicted and simulated cylinder pressure transients and inlet and delivery valve dynamics are compared over the complete pumping cycle. Close agreement between theory and experiment is achieved. The induction performance of the pump is examined in detail and the effects of operating conditions on volumetric efficiency are presented. The effect of inlet valve timing on delivery manifold pressure fluctuations is also discussed.

A model is developed for simulating and predicting the dynamics of intake-manifolds for automotive internal combustion engines. A thermodynamic control volume approach and bond graphs are used to derive mass and energy conservation equations. Simulation outputs include time histories of pressure, temperature, mass flow, energy flow, heat flow and overall volumetric efficiency. Cylinder pressure when the intake valve closes is intensively examined because it determines the volumetric efficiency. Increases in volumetric efficiency result from increases in pressure caused by dynamic effects. Volumetric efficiency versus rpm is used to evaluate the dynamic effects of certain intake-manifold configurations. Major design parameters are the length of the intake manifold pipe, diameter of the intake manifold pipe and length of the pipe upstream of the throttle valve. Changing manifold parameters can yield improvements in volumetric efficiency at certain engine speeds but can also cause deterioration at other speeds. Shortening the length of the upstream pipe moves the volumetric efficiency peaks to higher engine speeds.

This paper focuses on the control of systems with unknown dynamics and deals with the class of systems described by x˙=f(x,t) + h(x,t) + B(x,t)u + d(t) where h(x,t) and d(t) are unknown dynamics and unexpected disturbances, respectively. A new control method, Time Delay Control (TDC), is proposed for such systems. Under the assumption of accessibility to all the state variables and estimates of their delayed derivatives, the TDC is characterized by a simple estimation technique that evaluates a function representing the effect of uncertainties. This is accomplished using time delay. The control system’s structure, stability and design issues are discussed for linear time-invariant and single-input-single-output systems. Finally, the control performance was evaluated through both simulations and experiments. The theoretical and experimental results indicate that this control method shows excellent robustness properties to unknown dynamics and disturbances.

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.

A scheme for the design of rest-to-rest acceleration profiles to be used in the inverse dynamics approach to the control of the end-point of single link flexible arms is described. The scheme uses linear discrete models, and a stable pole-cancellation method to obtain acceleration profiles that yield inverse dynamics torques with the same supports as that of the end-point acceleration profiles; it allows for a design which reaches a balance between overshoot, peak torque and actuation time.

A new approach to the geometrical representation of manipulator dynamics is presented. The inertia ellipsoid, which is used to represent dynamic characteristics of a single rigid body, is extended to a general ellipsoid for a series of rigid bodies in order to represent the manipulator dynamics. The geometrical configuration of the generalized inertia ellipsoid (GIE) represents the characteristics of the manipulator as a whole. One can understand the complicated inertial effect and nonlinearity of multi-degree-of-freedom motion by simply investigating the GIE configuration. In the latter half of the paper, this method is applied to aid the design of a mechanical arm, in which dimensions of an arm structure and its mass distribution are optimized through the evaluation and graphical representation of the arm dynamics.

An approach for identifying the dynamics of large space structures is applied to a free-free beam. In this approach the system’s order is determined on-line, along with mode shapes, using recursive lattice filters which provide a linear least square estimate of the measurement data. The mode shapes determined are orthonormal in the space of the measurements and, hence, are not the natural modes of the structure. To determine the natural modes of the structure, a method based on the fast Fourier transform is used on the outputs of the lattice filter. These natural modes are used to obtain the modal amplitude time series from the measurements. The modal time series provides the input data for an output error parameter identification scheme that identifies the autoregressive moving average (ARMA) parameters of the difference equation model of the modes. Results using this approach for experimentally identifying the dynamics of a flexible beam hardware are presented.

Using a measured functional relationship for draft gear characteristics a nonlinear model is developed to predict the coupler forces between cars of a railroad train. The model is then simplified, using modal expansion, to effect an economy of digital computation time.

A method is presented which permits the simulation of the coupled lateral-vertical rigid body vibration response of a rubber-tired automated guideway transit (AGT) vehicle subject to guideway random irregularities. A coupled lateral-vertical dynamic model is developed. The general motions are expressed by Euler angles and inertial displacements. Basic vehicle dynamic modes are determined. A predicted lateral acceleration spectrum of the linearized model using guideway surface profile models for inputs are compared with the measured lateral acceleration spectra and found to agree reasonably well in the lower frequency (below about 7 Hz) range. Good agreement was found to exist between the predicted and measured root mean square (rms) accelerations for a wider range of frequencies.

The accuracy of the new equations for the rail-tie structure, derived by Kerr and Zarembski and recently generalized for dynamic problems by Kerr and Accorsi, is studied. This is done by comparing the natural frequencies based on the new equations with those calculated using a finite element method for a range of fastener stiffness values and a variety of rail spacings. The comparison revealed very close agreement. The findings confirm the suitability of the new equations for dynamic analyses of cross-tie tracks in the lateral plane.

The control of d.c. motors is often complicated by the fact that the dynamics of the system to be controlled are unknown. In this paper a deterministic controller is employed to control a d.c. motor which experiences a varying inertia load, Coriolis forces and unknown friction disturbances. All of the uncertainties in the system are assumed to be bounded. A hybrid controller, using a continuous velocity loop and a digital position loop, is developed. Experimental results verify the controller efficacy in dealing with bounded deterministic uncertainties.

An analysis and digital computer program are developed to simulate vehicle and guideway dynamic response. The magnetic levitation is of the electrodynamic suspension type. The mathematical model includes effects of the following: vehicle and guideway flexible deformations, vehicle suspension and propulsion pod translation relative to the vehicle, multiple guideway spans and aerodynamic loading. The simulation is programmed in such a way that the number of sequential spans over which the vehicle travels can be increased without increasing the degrees of freedom in the simulation. Illustrative results of the simulation are presented.

Field tests with an electric Re 6/6 locomotive are summarized in this paper. The test objectives included the assessment of the lateral wheel-rail dynamics on tangent track. A method is presented which measures continuously the wheelset’s lateral and yaw displacement from track centerline and local rail deflections. The data are obtained on a spatial base through track side marks in conjunction with wheelset rotary trigger pulses. These measurements give a vivid description of the nature of wheelset motion on real track. They allow to scrutinize some of the assumptions inherent to linear rail vehicle modelling. Linearization of the creep force laws and the contact geometry is found to be questionable particularly in the presence of tractive effort, and generally for near critical speed. The results should be of interest primarily to theoretical and experimental rail vehicle dynamicists.

An important consideration in the design of air cushion and magnetic suspensions is the power required to suspend or levitate the vehicle in equilibrium. Since this power level increases with an increase in the equilibrium clearance between the base of the suspension and the guideway, it is desirable to keep the design clearance as small as possible. Ideally, the base of the vehicle would never contact the guideway. Statistically, however, contact does occur and to establish a general criteria for defining minimum clearances based on the frequency of contact would be extremely difficult since the effects of contact, such as noise, vibration, wear, etc., vary with different design configurations and materials. The criteria of a very low average contact frequency (10−3 contacts/sec) is used in this paper to define the lower bound on vehicle-guideway clearance. Results are tabulated for an optimum suspension with heave dynamics and guideway irregularity inputs only. The sensitivity of the minimum clearance to guideway irregularity amplitude and wavelength characteristics and to RMS levels of primary suspension acceleration (force) levels is demonstrated. The results indicate that equilibrium clearances on the order of 0.03 in. are tolerable for operation over guideways as smooth as welded rail and that clearances on the order of 1.5 in. may be required for operation over guideways as rough as smooth highways.

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.

A method is presented which permits the simulation of the coupled vertical and lateral rigid body vibration response of an automobile to roadway roughness inputs. A set of equations in matrix form is obtained for an assumed ten degree-of-freedom mathematical model of the vehicle-tire system using generalized linear and Euler angle coordinates. Kinematic relations for a rolling tire which treat it as an elastically supported string under tension are incorporated into the overall system model. Forces and moments that act in the tire-roadway contact interface are represented mathematically as a function of the parameters and response variables of the vehicle system. The nonlinear system equations are subsequently simplified in order to apply them to a vehicle moving along a straight roadway. The formulated model is shown to be adequate for predicting acceleration response in a frequency range of 0.1–10 Hz for the set of roadway test roadway sections considered in the present study.

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.

Field tests and accompanying data analysis to characterize the stable and hunting behavior of freight cars are discussed. These tests confirmed the fundamentally nonlinear nature of the conventional freight car. The hunting performance of an open hopper car is described by speed ranges in which intermittent hunting occurs. At speeds above the intermittent hunting speed ranges, hunting always occurs, and at speeds below these ranges, hunting does not occur. Results of evaluating the stability of the freight car in terms of the natural frequency and damping ratio of the least-damped vibration mode are presented. Anomalies in these results indicate that the damping ratio may not be an adequate stability measure for this nonlinear system. Root-mean-square values of significant vehicle motions are presented for the entire range of vehicle test speeds.

A fundamental time-scaling property of manipulator dynamics has been identified that allows modification of movement speed without complete dynamics recalculation. By exploiting this property, it can be determined whether a planned trajectory is dynamically realizable given actuator torque limits, and if not, how to modify the trajectory to bring it within dynamic and actuating constraints.

This paper presents an automated procedure useful in the study of large constrained flexible structures, undergoing large specified motions. The structure is looked upon as a “partially open tree” system, containing closed loops in some of the branches. The governing equations are developed using Kane’s equations as formulated by Huston et al. The accommodation of the constraint equations is based on the use of orthogonal complement arrays. The flexibility and oscillations of the bodies is modelled using finite segment modelling, structure analysis, and scaling techniques. The procedures developed are expected to be useful in applications including robotics, space structures, and biosystems.

A method is presented for estimating the contact force variation between a collector brush and a rigid third rail when the third rail has a surface with random irregularity. Results are obtained for a reference case where the third rail roughness is estimated from the roughness of other known surfaces. The surface roughness of an actual commercial third rail is measured and the results are used to estimate the performance of a collector on the measured sample at 300 mph. Conclusions are drawn about the feasibility of power collection at 300 mph.

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.

We analyze a model of a freight car using asymptotic methods and obtain a formula for the critical speed that is valid over a wide range of warp stiffnesses. We also discuss corrections to this formula that are engendered by the other parameters that influence the motion. The results of the analysis are compared with numerical solutions of the model in order to assess their accuracy.

The vertical and lateral acceleration response of an automobile to roadway roughness inputs was simulated using a ten degree-of-freedom mathematical model. The simulated response compared favorably with that obtained experimentally in terms of their power spectral density functions and root mean squared values in the 0.1–10 Hz frequency range. Furthermore, within the context of ride quality, a sensitivity study was conducted to determine the effect of variations in the suspension damping ratio, anti-roll bar stiffness and lateral “pneumatic” stiffness on vehicle response variables. The indication is that a trade-off exists between the reduction in lateral and roll motions due to an increase in suspension damping and the resulting increase in the higher frequency components in the vertical acceleration. The model that has been developed is well suited for performing design trade-off analysis.

The optimum linear suspension for a vehicle traveling over a guideway with random irregularities and subjected to random external force disturbances is derived. The optimization is based upon a performance index which weights mean square vehicle acceleration (a measure of passenger comfort) and mean square relative displacement between the vehicle and guideway (a measure of required suspension dynamic excursion). The form of the optimum suspension is not restricted to a specific mechanical, magnetic or fluid suspension configuration. Performance curves and numerical design examples are presented to illustrate the influence of both guideway and external force disturbances upon optimum suspension performance capability.