Showing papers in "Journal of Dynamic Systems Measurement and Control-transactions of The Asme in 1992"

Input/Output Linearization Using Time Delay Control

Abstract: A control procedure that uses Time Delay Control to achieve input/output linearization of a class of nonlinear systems is presented. The control system is characterized by a simple algorithm and enhanced robustness properties in comparison with current control algorithms. The paper first reviews the fundamentals of input/output linearization. The use of Time Delay Control is then shown to result in an exact linear system for sufficiently small delay time. Modified controllers for systems with a low-pass filter are also investigated. Simulation results show that the algorithm works well with measurement noise. The controller is also tested on a single-link flexible arm to show the effectiveness of the simple algorithm in the control of complicated systems.

Synchronization of Two Motion Control Axes Under Adaptive Feedforward Control

Abstract: In this paper, motion synchronization of two d-c motors, or motion control axes, under adaptive feedforward control is considered. The adaptive feedforward control system for each axis consists of a proportional feedback controller, an adaptive disturbance compensator and an adaptive feedforward controller. If the two adaptive systems are left uncoupled, a disturbance input applied to one of the two axes will cause a motion error in the disturbed axis only, and the error becomes the synchronization error. To achieve a better synchronization, a coupling controller, which responds to the synchronization error, i.e., the difference between the two motion errors, is introduced. In this case, when a disturbance input is applied to one axis, the motion errors appear in the undisturbed axis as well as in the disturbed axis. The motion error in the undisturbed axis is introduced by the coupling controller and the adaptive feedforward controller. The adaptive synchronization problem is formulated and analyzed in the continuous time domain first, and then in the discrete time domain. Stability conditions are obtained. Effectiveness of the adaptive synchronization controller is demonstrated by simulation.

Stability and Performance Limits of Interaction Controllers

Abstract: Theoretical performance limits of controlled systems which interact with dynamic environments are analyzed from consideration of simple, single-axis mass-spring-damper systems. A measure of interaction control performance is defined which is independent of environment dynamics. It is shown that unmodelled dynamics between actuators and sensors places severe constraints on interaction control performance. An ultimate performance limit to guaranteed-stable interaction control is derived

Modeling and Validation of Automotive Engines for Control Algorithm Development

Abstract: There is considerable interest in coordinated automotive engine/transmission control to smooth shifts, and for traction control of front wheel vehicles. This paper outlines a nonlinear dynamic engine model of a port fuel-injected engine, which can be used for control algorithm development. This engine model predicts the mean engine brake torque as a function of the engine controls (i.e., throttle angle, spark advance, fuel flow rate, and exhaust gas recirculation (E. G. R.) flow rate)

Extended Bandwidth Zero Phase Error Tracking Control of Nonminimal Phase Systems

Abstract: This paper describes a new feedforward algorithm for accurate tracking control of nonminimal phase systems. Accurate feedforward calculation involves a prefilter design using the inverse system model. Nonminimal phase systems cause problems with this prefilter design, because unstable zeros become unstable poles in the inverse model. The zero phase error tracking control algorithm (ZPETC) consists of a substitution scheme, which removes the unstable zeros

Vehicle Lateral Velocity and Yaw Rate Control With Two Independent Control Inputs

Abstract: In automatic lateral control, which will play a key role in highway automation, vehicles must follow a given path and vehicle direction must be controlled as desired. Therefore, the ideal is for the lateral motion and yaw motion of the vehicle to be controlled independently. The requires at least one additional control input which is independent of the front steering angle. This paper explores the use of two independent control inputs, which are the front steering angle and an extra control input

A system level study of the longitudinal control of a platoon of vehicles

Abstract: This paper presents a preliminary system study of a longitudinal control law for a platoon of nonidentical vehicles using a simplified nonlinear model for the vehicle dynamics This study advances the art of automatic longitudinal control for a platoon of vehicles in the sense that is considers longer platoons composed of nonidentical vehicles; furthermore, the longitudinal control laws presented in this study take advantage of communication possibilities not available in the recent past

Analysis of Linear Time Invariant Systems With Time Delay

Abstract: Time Delay Control has recently been suggested as an alternative scheme for control of systems with unknown dynamics and unpredictable disturbances. The proposed control algorithm does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it uses information in the recent past to directly estimate the unknown dynamics at any given instant, through time delay. In earlier papers, analysis and implementation of Time Delay Controller for nonlinear systems were discussed. This paper analyzes the continuous Time Delay Controller for a class of linear systems and presents necessary and sufficient conditions for control system stability

Models of a Pneumatic PWM Solenoid Valve for Engineering Applications

Abstract: PWM (Pulse width modulated) solenoid valves possess the advantages of low cost, high flow rate gain, and simple structure. However, the use of a PWM solenoid valve causes both discontinuity and nonlinearity of the flow rate; this results in difficulties of modeling and of control. This paper presents our work on modelling a pneumatic PWM solenoid valve for engineering applications

Modeling and Control of Single- Link Flexible Arms With Lumped Masses

Abstract: This paper deals with the modeling and control of a special class of single-link flexible arms. These arms consist of flexible massless structures having some masses concentrated at certain points of the beam. In this paper, the dynamic model of such flexible arms is dewloped and some of the control properties are deduced. A robust control scheme to remove the effects of friction in the joins is proposed. The control scheme consists of two nested feedback loops, an inner loop to control the position of the motor and an outer loop to control the tip position. The inner loop is described in other publications. A simple fedforward-feedback controller is designed for the outer loop to driw the beam accurately along a desired trajectoty. Effects of the changes in the tip’s mass are studied. This modeling and control method is then generalized to the distributed-mass flexible beam case. Finally, experimentaf results are presented. This paper deals with the modeling and control of a special class of single-link, lumped-mass, flexible arms. These arms consist of massless flexible structures that have masses concentrated at certain points of the beam (see Fig. 1). Although the translations of these masses produce stresses in the flexible structure, their rotations do not generate any torque in the beam. Therefore, the number of vibrational modes in the structure coincides with the number of lumped masses. Book (1979) studied the case of two rigid masses connected by a chain of massless beams having an arbitrary number of rotation joints. Our problem differs from this in the sense that our structure has only one rotation joint and an arbitrary number of lumped masses. These two particular structures are studied because: Some lightweight robots and other applications can be reasonably approximated by these models. Their dynamics may be easily modeled as compared to distributed-mass flexible arms. Interesting properties for the control of flexible arms are deduced from their dynamic models. A method to control these arms is inferred from the structure of the model. The influence of changes in the tip’s mass are easily characterized. Given a distributed-mass flexible arm, there always exits a truncated dynamic model which is of the same form as the lumped-mass flexible arm model and which reproduces the dynamics of the measured variables. This allows us to generate the above mentioned control method to the case of distributed-mass flexible arms. - Contributed by the Dynamic Systems and Control Division for publication

Estimation of Vehicle Shaft Torque Using Nonlinear Observers

Abstract: Current closed-loop automotive shift control algorithms could greatly benefit if a measurement of the drive axle shaft torque was available. Direct measurements using strain gauges are too expensive for commercial applications. Magnetic pickup sensors that count the passage of gear teeth provide very inexpensive RPM measurements and are currently being used in production vehicles. This paper shows through simulations how these sensors can be used with a nonlinear observer technique (sliding mode) to estimate axle shaft torque from measurements of transmission output speed and driven wheel speed

Independent Modal Space Control With Positive Position Feedback

Abstract: An independent modal space control (IMSC) algorithm is presented, whose modal control forces are generated from a positive position feedback (PPF) strategy. The proposed algorithm combines the attributes of both the IMSC and the PPF, and maintains the simplicity of the IMSC as it designs the controller of a complex structure at the uncoupled modal level. The effectiveness of the algorithm in damping out the vibration of flexible structures is validated experimentally. A simple cantilevered beam is employed as an example of a flexible structure whose multimodes of vibration are controlled by a single actuator. Performance of the active control system is determined in the frequency and the time domains. The experimental results indicate the potential of the proposed methodology as a viable method for controlling the vibration of large flexible structures.

Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings

Abstract: The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally

Effects of Noise on Sensor Placement for On-Orbit Modal Identification of Large Space Structures

Abstract: A method of sensor placement for the purpose on-orbit modal identification and test-analysis correlation is presented. The method is an extension of the affective Independence method presented in past work to include the effects of a general representation of measurement noise. Sensor noise can be distributed nonuniformly throughout the structure as well as correlated between sensors. The only restriction is that the corresponding noise covariance intensity matrix is positive definite

Transferring Manipulative Skills to Robots: Representation and Acquisition of Tool Manipulative Skills Using a Process Dynamics Model

Abstract: A new method based on task process models for acquiring manipulative skills from human experts is presented. In performing manipulative tasks such as deburring, a human expert moves a tool at an optimal feedrate and cutting force as well as with an appropriate compliance for holding the tool. An experienced worker can select the correct strategy for performing a task and change it dynamically in accordance with the task process state. In this paper, the human expertise for selecting a task strategy that accords with the process characteristics is modeled as an associative mapping, and represented and generated by using a neural network. First, the control strategy for manipulating a tool is described in terms of feedforward inputs and tool holding dynamics. The parameters and variables representing the control strategy are then identified by using teaching data taken from demonstrations by an expert. The task process is also modeled and characterized by a set of parameters, which are identified by using this same teaching data. Combining the two sets of identified parameters, we can derive an associative mapping from the task process characteristics to the task strategy parameters. The consistency of the mapping and the transferability of human skills are analyzed by using Lipschitz’s condition. The method is applied to deburring, and implemented on a direct-drive robot. It is shown that the robot is able to associate a correct control strategy with process characteristics in a manner similar to that of the human expert.

Walking Without Impacts as a Motion/Force Control Problem

Abstract: The paper deals with the synthesis of control for impactless bipedal walking. In order of avoid impulses, both the specified motion of the biped and its ground reactions are controlled, yielding a combined motion and force control problem. A method for modeling and solving such problems is proposed. and then illustrated by the example of an impactless planar walk of a seven-link bipedal robot. Some numerical results of the motion simulation are reported.

Output Feedback Two-Time Scale Control of Multilink Flexible Arms

Abstract: Lightweight flexible arms will most likely constitute the next generation robots. The design key is the adoption of flexible links, rather than rigid links like in today's industrial robots. Despite all the potential advantages achievable with a flexible arm, the control problem is complex, due to the introduction of increasingly more complex dynamics. This paper represents an effort toward the goal of designing efficient control systems for multilink flexible arms. A two-time scale approach is pursued which allows the adoption of a composite control strategy. First a slow control can be designed for the slow (rigid) sybsystem, then a fast stabilizing control for the fast (flexible) subsystem. The main contribution of the paper is to address the problem of lack of full state measurements concerned with the fast control design. An output feedback dynamic compensator of fixed order is designed. Its optimal gains are computed according to a loop transfer recovery technique in order to obtain a robust design. The control is tested by means of simulation results for a nonlinear model of a two-link flexible arm. Introduction Lightweight flexible arms have lately been receiving the at­tention of an increasing number of researchers.. Potentially, they may improve on the performance of conventional massive rigid industrial manipulators (Book, 1985). The main problem for modeling and controlling a flexible arm is induced by the structural flexibility (Cetinkunt and Book, 1990). Several approaches have been proposed in the literature for modeling lightweight arms. One common denominator is the adoption of the Lagrangian technique which yields closed-form expressions of all dynamic terms. As for the inherently dis­tributed nature of the flexible system, finite-dimensional models are needed which approximate the exact infinite-dimensional models. The recursive formulation proposed by Book (1984), suitably combined with the assumed-modes method (Meirov-itch, 1967), leads to a number of generalized coordinates to handle for control purposes. Nevertheless, other methods have been studied, including finite elements (Sunada and Du-bowsky, 1983; Usoro et al; 1986), polynomial expansions (To-mei and Tornambe, 1988), Hamiltonian principle (Everett, 1989; Serna and Bayo, 1989), with different implications on control design complexity. On the other hand, it was stressed by Book et al. (1985) that the control problem for a flexible arm may be solved by com­bination of the following approaches:

Synthesis of Actively Adjustable Springs by Antagonistic Redundant Actuation

Abstract: A methodology for active spring generation is presented based on antagonistic redundant actuation. Antagonistic properties are characterized using an effective system stiffness. 'Antagonistic stiffness' is generated by preloading a closed-chain (parallel) linkage system. Internal load distribution is investigated along with the necessary conditions for spring synthesis. The performance and stability of a proposed active spring are shown by simulation, and applications are discussed.

Sensor-Based Chatter Detection and Avoidance by Spindle Speed Selection

Abstract: This paper presents the results of a series of experimental studies of a control system which, based on information from available sensors (in this case a microphone was primarily used), automatically adjusts the spindle speed and the feed rate so as to achieve stable milling. It is seen that by iteratively adjusting the spindle speed so that the frequency with which the teeth pass is equal to the dominant frequency in the spectrum of the sensor output, the system will very quickly be driven into a stable region, if such a stable region exists. Experimental results which confirm the applicability of this control scheme to a variety of milling operations are presented. They include slotting and partial immersion cuts in cast iron and aluminum. Since this strategy is based on information supplied by the sensors, it is capable of adapting to tool changes, thin webs, corners, etc[[ellipsis]] which cause changes in the dynamics of the machine-tool-workpiece system and therefore may cause chatter to arise during the course of a milling operation. This strategy does not require an a priori knowledge of the dynamics of the machine-tool-workpiece system as do most of the off-line methods.

Design of Disturbance Decoupled Observer for Bilinear Systems

Abstract: An observer for a bilinear system with an unknown unmeasurable disturbance is considered. Necessary and sufficient conditions for the existence of disturbance decoupled full order and minimal order observers are formulated. The conditions analogous to detectability and pole assignment of linear observers are also given. These conditions provide a basis for verification of observer existence and design procedures to select observer matrices using straightforward matrix calculus

On Time Delay in Noncolocated Control of Flexible Mechanical Systems

Abstract: A new method is presented for noncolocated control of flexible mechanical systems. The destabilizing effect of noncolocation of sensors and actuators is eliminated through introduction of specific time delay block(s) in the control system. The time delay constants in those blocks depend on the system eigenstructure. For a given flexible mechanical system, if there exists a time delay relation, the system response at one point can be exactly predicted from the vibration measurement at other point(s) of the system. In this case all stabilizing controllers from colocated control can be directly used

Robotic Manipulator Collisions: Modeling and Simulation

Abstract: In this paper, a new formulation of the dynamics of a robotic manipulator work environment is presented. The work environment is modeled in a way that permits the robot transition to and from contact with the work environment to be effectively simulated. This method circumvents the discontinuities inherent in previously proposed models of work environment dynamic models that have, until now, prevented researchers from considering that phase of manipulation

Dynamics and Control of a Translating Flexible Beam With a Prismatic Joint

Abstract: The complete dynamic model of a translating flexible beam, with a tip mass at one end and emerging from or retracting into a rigid base at the other, is presented. The model considers the effect of elastic and translational motions of the beam on each other. The properties of the eigenfunctions of a fixed-free beam are exploited to obtain closed-form expressions for several domain integrals that arise in the model.

Robust Linear-Optimal Control Laws for Active Suspension Systems

Abstract: 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

A Preview Steering Autopilot Control Algorithm for Four-Wheel-Steering Passenger Vehicles

Abstract: This paper addresses the control law design of a preview steering autopilot for a four-wheel-steering vehicle to perform automatic lane tracking. In the concept, an on-board computer vision system is used in lieu of the driver’s vision to track the roadway. The steering autopilot design is formulated as an optimal, discrete-time preview path tracking problem under the “perfect measurement” assumption. Simulation results indicate that the tracking performance of the steering autopilot was improved by preview relative to that calculated for an autopilot without preview. These results also indicate the existence of an effective preview time with which almost all the benefits of previewing future information can be obtained. This effective preview time is about three times the reciprocal of the autopilot’s bandwidth. Our study also indicates that preview steering autopilots can tolerate the use of actuators with a lower bandwidth than those designed without preview information.

Modeling of a Hydraulic Energy Regeneration System: Part II—Experimental Program

Abstract: This study reports experimental data taken with a hydraulic energy regeneration system and compares the measured data with analytical results. The system tested consisted of two foam-filled hydraulic accumulators, a variable-displacement piston-type pump/motor, a reservoir and a flywheel. During a series of experiments, energy was repeatedly transferred between the hydraulic accumulators and the flywheel through the pump/motor. Computed system variables compared favorably with the experimental results. At high and moderate pump/motor swivel angles, the round-trip efficiency varied from 61 to 89 percent. It was significantly lower at small angles.

Dynamic Analysis to Evaluate Viscoelastic Passive Damping Augmentation for the Space Shuttle Remote Manipulator System

Abstract: The effectiveness of constrained viscoelastic layer damping treatment designs is evaluated separately as passive control measures for low frequency joint dominated modes and higher frequency boom flexure dominated modes using a NASTRAN finite element analysis. Passive damping augmentation is proposed which is based on a constrained viscoelastic layer damping treatment applied to the surface of the manipulators's flexible booms. It is pointed out that even the joint compliance dominated modes can be damped to some degree through appropriate design of the treatment.

Failure detection diagnostics for thermofluid systems

Abstract: This paper presents experimental results for an on-board microprocessor-based failure detection package designed to assist in the diagnosis of heat pump failures. A model-free limit and trend checking scheme, and a model-based innovations detection formulation operate in parallel to detect anomalous behavior. This dual approach permits the study of tradeoffs between failure detection performance and method complexity. A series of typical anomalies are experimentally simulated in a heat pump, and results are presented to demonstrate the performance of each detection strategy