Showing papers in "Journal of Dynamic Systems Measurement and Control-transactions of The Asme in 1987"
1,542 citations
TL;DR: In this article, a digital feed-forward control algorithm for tracking desired time varying signals is presented, which is particularly suited to the general motion control problems including robotic arms and positioning tables.
Abstract: A digital feedforward control algorithm for tracking desired time varying signals is presented. The feedforward controller cancels all the closed-loop poles and cancellable closed-loop zeros. For uncancellable zeros, which include zeros outside the unit circle, the feedforward controller cancels the phase shift induced by them. The phase cancellation assures that the frequency response between the desired output and actual output exhibits zero phase shift for all the frequencies. The algorithm is particularly suited to the general motion control problems including robotic arms and positioning tables. A typical motion control problem is used to show the effectiveness of the proposed feedforward controller.
1,477 citations
TL;DR: In this article, des observateurs glissants de systemes non lineaires possedant en presence de bruit du aux mesures and d'erreur de modelisation des proprietes interessantes.
Abstract: Presentation des observateurs glissants de systemes non lineaires possedant en presence de bruit du aux mesures et d'erreur de modelisation des proprietes interessantes
732 citations
178 citations
TL;DR: It is shown that for a given path, the problem of optimal control of robotic manipulators is reduced to a search over the velocity of one moving manipulator link.
Abstract: The problem of optimal control of robotic manipulators is dealt with in two stages: (1) optimal trajectory planning, which is performed off-line and results in the prescription of the position and velocity of each link as a function of time along a “given” path and (2) on-line trajectory tracking, during which the manipulator is guided along the planned trajectory using a feedback control algorithm. In order to obtain a general trajectory planning algorithm which could account for various constraints and performance indices, the technique of dynamic programming is adopted. It is shown that for a given path, this problem is reduced to a search over the velocity of one moving manipulator link. The design of the algorithm for optimal trajectory planning and the relevant computational issues are discussed. Simulations are performed to test the effectiveness of this method. The use of this algorithm in conjunction with an on-line controller is also presented.
141 citations
TL;DR: In this paper, a computer-controlled vehicle that is part of a mobile nursing robot system is described, which applies a motion control strategy that attempts to avoid slippage and min imize position errors.
Abstract: A computer-controlled vehicle that is part of a mobile nursing robot system is described. The vehicle applies a motion control strategy that attempts to avoid slippage and min imize position errors. A cross-coupling control algorithm that guaran tees a zero steady-state orientation error (assuming no slippage) is proposed and a stab ility analysis of the control system is presented. Results of experiments performed on a prototype vehicle verify the theoretical analysis.
115 citations
TL;DR: In this paper, a nonlinear active vibration damper was developed which uses a spatially distributed piezoelectric actuator, polyvinylidene flouride, to achieve active vibration control of a cantilever beam.
Abstract: A nonlinear active vibration damper has been developed which uses a spatially distributed piezoelectric actuator, polyvinylidene flouride, to achieve active vibration control of a cantilever beam. The control algorithm was derived using Lyapunov’s Second Method. All modes of the beam can be controlled simultaneously if the angular velocity of the tip of the beam is known. A simulation algorithm was developed to predict the effect of the control on the free decay of a single mode. A parameter study for the first mode was performed and compared to experimental results. The active damper has been tested successfully on two different scale structures.
104 citations
TL;DR: In this paper, a rigid and flexible motion controller is derived to introduce additional damping into the flexible motion by using additional sensors to measure the compliant link vibrations and feed them back to the controller.
Abstract: The operation of high precision robots is severely limited by. their manipulator dynamic deflection, which persists for a period of time after a move is completed. These unwanted vibrations deteriorate the end effector positional accuracy and reduce significantly the robot arm production rate. A “rigid and flexible motion controller” is derived to introduce additional damping into the flexible motion. This is done by using additional sensors to measure the compliant link vibrations and feed them back to the controller. The existing actuators at the robot joints are used (i.e., no additional actuators are introduced). The performance of the controller is tested on a dynamic model, developed in previous work, for a spherical coordinate robot arm whose last link only is considered to be flexible. The simulation results show a significant reduction in the vibratory motion. The important issue of control and observation spillover is examined and found to present no significant practical problems. Partial evaluation of this approach is performed experimentally by testing two controllers, a “rigid body controller” and a “rigid and flexible motion controller,” on a single joint of a spherical coordinate, laboratory robot arm. The experimental results show a significant reduction in the end effector dynamic deflection; thus partially validating the results of the digital simulation studies.
101 citations
TL;DR: In this paper, a reduced-order model of a biped locomotion system and its theoretical basis are presented based upon the concept of local feedback, and it has been reported from physiological studies that local feedback at each articular joint exists in human motor control.
Abstract: A new reduced order model of a biped locomotion system and its theoretical basis are presented based upon the concept of local feedback. It has been reported from physiological studies that local feedback at each articular joint exists in human motor control, and the authors have already studied from the viewpoint of control engineering that local feedback makes the total system robust. A theorem is presented by which two dominant modes are obtained by the application of local feedback at each articular joint in the biped locomotion machine and it is shown that these two modes correspond to inverted-pendulum modes. The reduced order model derived by using these two modes contains the effect of the motion of body and swing leg which is indispensable for the control of biped locomotion. It is shown that this model can approximate very well the original higher model in almost all walking phases containing start-up and stopping motions.
93 citations
TL;DR: In this article, the manipulator inverse is used as a feed forward controller in order to achieve trajectory tracking by the joint angles, and an adaptive feedback controller and an auxiliary signal enhance closed-loop stability and achieve faster adaptation.
Abstract: An approach in which the manipulator inverse is used as a feedforward controller is employed in the adaptive control of manipulators in order to achieve trajectory tracking by the joint angles. The desired trajectory is applied as an input to the feedforward controller, and the controller output is used as the driving torque for the manipulator. An adaptive algorithm obtained from MRAC theory is used to update the controller gains to cope with variations in the manipulator inverse due to changes of the operating point. An adaptive feedback controller and an auxiliary signal enhance closed-loop stability and achieve faster adaptation. Simulation results demonstrate the effectiveness of the proposed control scheme for different reference trajectories, and despite large variations in the payload.
89 citations
TL;DR: The paper presents the results of an ongoing research project where the objectives are to evaluate medium access control protocols in view of the requirements for distributed digital flight control systems (DDFCS) of advanced aircraft and to recommend a specific protocol for their prototype development.
Abstract: The paper presents the results of an ongoing research project where the objectives are to evaluate medium access control (MAC) protocols in view of the requirements for distributed digital flight control systems (DDFCS) of advanced aircraft and to recommend a specific protocol for their prototype development. The selection of an appropriate MAC protocol is critical for the dynamic performance of an aircraft because the DDFCS, in addition to the sampling time delay, is subject to time-varying transport delays due to data latency of messages at different terminals of the control loop. The SAE linear token bus, SAE token ring and the conventional MIL-STD-1553B protocols have been analyzed using combined discrete-event and continuous-time simulation techniques. The impact of data latency on the dynamic performance of an advanced aircraft is illustrated by simulation of the closed loop DDFCS.
TL;DR: In this article, a nonlinear robust control methodology for robot control under the influence of uncertainties is proposed, which decouples a robot dynamics and obtains a set of equations in joint or hand coordinates.
Abstract: Manufacturing tasks often require short cycle time and consistent quality. To meet these demands, a robot control system must achieve fast and precise robot position control, and/or maintain proper force control at the robot's end-effector. Many control schemes were proposed in the literature for robot position control formulated in either joint or cartesian coordinates. Some robot control schemes were also proposed for hybrid (force and position) control in the cartesian coordinate. Nevertheless, when uncertainties such as modeling errors or unknown external disturbances exist, performance of these schemes substantially degrades.
This dissertation proposes a nonlinear robust control methodology for robot control under the influence of uncertainties. The control input consists of a nonlinear part and a linear part. The nonlinear part decouples a robot dynamics and obtains a set of equations in joint or hand coordinates. The linear part utilizes robust servo-mechanism theory to suppress position or force tracking error in each respective coordinate. Based on this nonlinear robust control concept, the following schemes for robust robot control are proposed: (1) A nonlinear robust control scheme for robot position control in joint coordinates. (2) A nonlinear robust control scheme for robot position control in cartesian coordinates. (3) A nonlinear robust control scheme for robot hybrid control in cartesian coordinates.
These nonlinear robust control schemes were applied to a two-joint SCARA-type robot through computer simulation. The results demonstrate that these schemes exhibit excellent robustness properties and can achieve satisfactory robot position or force control under severe modeling errors.
TL;DR: In this article, a commande numerique permettant lusinage de pieces avec des sections non circulaires sur un tour is presented, and a demonstration de la fiabilite de l'algorithme de commande propose par simulation and experimentation.
Abstract: Conception et mise en œuvre d'une commande numerique permettant l'usinage de pieces avec des sections non circulaires sur un tour. Demonstration de la fiabilite de l'algorithme de commande propose par simulation et experimentation
TL;DR: Conception d'un bras de manipulateur en boucle ouverte avec des tenseurs d'inertie independants de la configuration and decouplage as discussed by the authors.
Abstract: Conception d'un bras de manipulateur en boucle ouverte avec des tenseurs d'inertie independants de la configuration et decouplage
TL;DR: Basee seulement sur la connaissance des proprietes fonctionnelles relatives a la limite de l'incertitude variable dans le temps, une classe de commandes adaptatives bouclees est developpee.
Abstract: Basee seulement sur la connaissance des proprietes fonctionnelles relatives a la limite de l'incertitude variable dans le temps, une classe de commandes adaptatives bouclees est developpee, et qui sous certaines hypotheses realistes, assure la convergence entre le systeme dynamique incertain et le modele
TL;DR: In this article, a simple scheme for multivariable control of multiple-joint robot manipulators in joint and Cartesian coordinates is presented, which consists of two independent multi-ivariable feedforward and feedback controllers.
Abstract: The paper presents simple schemes for multivariable control of multiple-joint robot manipulators in joint and Cartesian coordinates. The joint control scheme consists of two independent multivariable feedforward and feedback controllers. The feedforward controller is the minimal inverse of the linearized model of robot dynamics and contains only proportional-double-derivative (PD2) terms - implying feedforward from the desired position, velocity and acceleration. This controller ensures that the manipulator joint angles track any reference trajectories. The feedback controller is of proportional-integral-derivative (PID) type and is designed to achieve pole placement. This controller reduces any initial tracking error to zero as desired and also ensures that robust steady-state tracking of step-plus-exponential trajectories is achieved by the joint angles. Simple and explicit expressions of computation of the feedforward and feedback gains are obtained based on the linearized model of robot dynamics. This leads to computationally efficient schemes for either on-line gain computation or off-line gain scheduling to account for variations in the linearized robot model due to changes in the operating point. The joint control scheme is extended to direct control of the end-effector motion in Cartesian space. Simulation results are given for illustration.
TL;DR: In this article, the authors deal with the fitting of a rational function to an experimentally determined frequency domain transfer function and show that the use of overdetermined fitted systems improve the identification in noisy situations.
Abstract: This paper deals with the fitting of a rational function to an experimentally determined frequency domain transfer function. Examples show that the use of overdetermined fitted systems improve the identification in noisy situations. A method is presented, enabling the determination of the number of zero/poles of the system, and the relation to the rank of the matrix used in a least square identification method.
TL;DR: In this article, the transient response of an electrohydraulic servovalve coupled to an axial piston ball motor is analyzed and the importance of coulomb friction damping is established.
Abstract: The transient response of an electrohydraulic servovalve coupled to an axial piston ball motor is analyzed. In particular, the effect of long lines between the servovalve and motor is studied together with coulomb friction effects at the motor. The dynamic characteristics of the basic system with short lines is first established via frequency response measurements coupled with a small signal linearized analysis. Longer lines are then added and the method of characteristics, coupled with a quasi-analytical solution for the motor-end equations, is used to predict the large signal transient response. The importance of coulomb friction damping is established together with damping due to servovalve dynamics.
TL;DR: In this paper, a new computational method for solving control problems, when it is desired that the control action be bang-bang is presented, where the switching times are updated to minimize the final state missed distance.
Abstract: A new computational method for solving control problems, when it is desired that the control action be bang-bang is presented. A gradient-based algorithm is developed where the switching times are updated to minimize the final state missed distance. The algorithm explains how a change in a switching time propagates through the other switching times and affects the final state. The algorithm is applicable to linear and nonlinear problems, including multiinput systems.
TL;DR: In this article, the authors discuss the strategies de relegation a l'entree de facon exacte and approchee of a systeme de commande, i.e., the relegation of the commande from a given location to another location.
Abstract: La tâche du systeme de commande est d'influencer le couplage mecanique et de permettre une commande separee des trajectoires et des forces. La relegation de la commande vers l'entree ou l'etat est possible. On etudie les strategies de relegation a l'entree de facon exacte et approchee. Application a un robot a 3 articulations
TL;DR: Commande de trajectoire d'un robot dans un espace tridimensionnel par utilisation de the notion de sous-espace direct par utilising de la notion ofêtre direct.
Abstract: Commande de trajectoire d'un robot dans un espace tridimensionnel par utilisation de la notion de sous-espace direct
TL;DR: Combination d'un invariant de reaction avec un systeme de commande a structure variable non lineaire pour controler le pH dans un reacteur de melange as mentioned in this paper.
Abstract: Combinaison d'un invariant de reaction avec un systeme de commande a structure variable non lineaire pour controler le pH dans un reacteur de melange