Showing papers on "Proportional control published in 2005"

Control of Robot Manipulators in Joint Space

Abstract: Part I: Preliminaries.- Introduction to Part I.- What Does 'Control of Robots' Involve?.- Mathematical Preliminaries.- Robot Dynamics.- Properties of the Dynamic Model.- Case Study: The Pelican Prototype Robot.- Part II: Position Control.- Introduction to Part II.- Proportional Control plus Velocity Feedback and PD Control.- PD Control with Gravity Compensation.- PD Control with Desired Gravity Compensation.- PID Control.- Part III: Motion Control.- Introduction to Part III.- Computed-torque Control and Computed-torque+ Control.- PD+ Control and PD Control with Compensation.- Feedforward Control and PD Control plus Feedforward.- Part IV: Advanced Topics.- Introduction to Part IV.- P'D' Control with Gravity Compensation and P'D' Control with Desired Gravity Compensation.- Introduction to Adaptive Robot Control.- PD Control with Adaptive Desired Gravity Compensation.- PD Control with Adaptive Compensation.- Appendices.- A. Mathematical Support.- B. Support for Lyapunov Theory.- C. Proofs of some Properties of the Dynamic Model.- D. Dynamics of Direct-current Motors.

A novel motor drive design for incremental motion system via sliding-mode control method

Abstract: This paper proposes a particular motor position control drive design via a novel sliding-mode controller. The newly designed controller is especially suitable for the motor incremental motion control which is specified by a trapezoidal velocity profile. The novel sliding-mode controller is designed in accordance with the trapezoidal velocity profile to guarantee the desired performance. A motor control system associated PC-based incremental motion controller with permanent-magnet synchronous motor is built to verify the control effect. The validity of the novel incremental motion controller with sliding-mode control method is demonstrated by simulation and experimental results.

New modified Smith predictor scheme for integrating and unstable processes with time delay

Abstract: The paper extends a recently published Smith predictor scheme for controlling integrating and unstable processes with time delay, which results in a simpler control structure and improved tuning capacities for reference inputs and load disturbances. In the proposed scheme, a proportional controller is subtly employed to stabilise the setpoint response, and then an H2 optimal controller is analytically designed for setpoint tracking. To obtain the integral-squared-error (ISE) performance objective, a practically desired disturbance rejection transfer function is proposed to design the disturbance estimator in the inner closed loop of the proposed control structure. Essentially, the proposed control structure gives two-degrees-of-freedom (2DOF) control and correspondingly the setpoint and load disturbance responses can each be tuned conveniently by a single control parameter. Hence the setpoint response is decoupled from the load disturbance response, and both can be quantitatively estimated in terms of the proposed analytical tuning procedures. Simulation examples are included to show the superiority of the proposed method.

Advances in the linear/nonlinear control of aeroelastic structural systems

Abstract: Active aeroelastic control is a recently emerging technology aimed at providing solutions to a large class of problems involving the aeronautical/aerospace flight vehicle structures that are prone to instability and catastrophic failures, and to oscillations that can yield structural failure by fatigue. In order to prevent such damaging phenomena to occur, the linear/nonlinear aeroelastic control technology should be applied. Its goals are among others: (i) to alleviate and even suppress the vibrations appearing in the subcritical flight speed range, (ii) to enlarge the flight envelope by increasing the flutter speed, and (iii) to enhance the post-flutter behavior by converting the unstable limit cycle oscillation to a stable one. A short review of the available control techniques and capabilities is presented first. Attention is focused on the open/closed-loop of 2D and 3D lifting surfaces as well as on panels exposed to supersonic flowfields. A number of concepts involving various control methodologies, such as proportional, velocity, linear quadratic regulator, modified bang-bang, sliding mode observer, time-delay control, fuzzy, etc., as well as results obtained with such controls are presented. Emphasis is placed on theoretical and numerical results obtained with the various control strategies that are considered in a comparative way. Finally, conclusions and directions for further work are presented.

Synchronised trajectory-tracking control of multiple 3-DOF experimental helicopters

Abstract: A synchronised trajectory-tracking control strategy is proposed for multiple experimental three-degrees-of-freedom helicopters. The model-based controller includes a feedforward compensation term and a PD feedback control term. Asymptotic convergence is achieved for both trajectory tracking and motion synchronisation. A proposed generalised synchronisation error concept allows the design of different synchronisation strategies so that different synchronisation performance can be reached. Experimental results verify the effectiveness of the proposed controller.

Changes to IEEE 421.5 recommended practice for excitation system models for power system stability studies

Abstract: IEEE standard 421.5 on excitation system models for power system stability studies is in the process of being updated. Additional control functions have been added and the existing ones experienced significant modifications. This paper outlines these changes. Other related papers will cover the topics of Under / Over Excitation Limiters and var/PF controllers and regulators.

Model-based control and estimation of cavity flow oscillations

Abstract: Techniques for feedback control of oscillations in the flow past a cavity are presented. Low-order models are obtained using two methods (empirical Galerkin models, and a simple nonlinear oscillator model), and validated against 2D direct numerical simulations of the flow, which is actuated by a body force at the leading edge of the cavity. The models are used to construct dynamic observers, which reconstruct the flow state from a single pressure sensor, and perform much better than static estimators commonly used for flow estimation. Several control approaches are compared, including simple proportional control with a phase lag, LQG control using Galerkin models, and a dynamic phasor approach based on the work of Noack et al (2003). All three controllers are implemented in the full simulation, and able to reduce the amplitude of oscillations. The LQG regulator requires careful tuning, and the closed-loop behavior often does not match that predicted by the model, but the dynamic phasor approach eliminates the oscillations completely in the full simulation, with a transient response that matches that predicted by the loworder model.

PID Controller Design for a Flexible-Link Manipulator

Abstract: This paper investigates the application of the H ∞ proportional-integral-derivative (PID) control synthesis method to tip position control of a flexible-link manipulator. To achieve high performance of PID control, this particular control design problem is cast into the H ∞ framework. Based on the recently proposed H ∞ PID control synthesis method, a set of admissible controllers is then obtained to be robust against uncertainty introduced by neglecting the higher-order modes of the link and to achieve the desired time-response specifications. The most important feature of the H ∞ PID control synthesis method is the ability to provide the knowledge of the entire admissible PID controller gain space which can facilitate controller fine tuning. Finally, experimental results are given to demonstrate the effectiveness of H ∞ PID control.

Nonlinear PD Synchronized Control for Parallel Manipulators

Abstract: A simple synchronized control algorithm is proposed, by incorporating cross-coupling technology into a common PD control architecture, for control of parallel manipulators. A saturated proportional (S-P) control and a linear proportional derivative (PD) control plus gravity force compensation is implemented for synchronization and position control, respectively. The proposed control law is easy to implement and is able to stabilize motion of each actuator while synchronizing all actuators’ motions, so that differential position errors amongst actuators converge to zero. It is shown that the proposed method guarantees global asymptotical stability of the closed-loop system. Experiments performed on a three-DOF parallel manipulator demonstrate the effectiveness of the proposed approach.

Time-Delay Effects on Linear/Nonlinear Feedback Control of Simple Aeroelastic Systems

Abstract: A study of the effects of time delay on the linear/nonlinear feedback control of two-dimensional lifting surfaces in an incompressible flowfield is presented. Specifically, the case of a one-degree-of-freedom system is considered in detail, and in that context, both the structural and the unsteady aerodynamics models are assumed to be linear. The study of the stability/instability behavior of nonlinear feedback time-delay closed-loop aeroelastic systems

Modeling and control of two stage twin spool servo-valve for energy-saving

Abstract: A control strategy of two stage twin spool servovalves in the load-sensing mobile applications is presented. The twin spool valve differs from the conventional valve in that it provides the ability to control flow into and out of valves independently. In this paper, the nonlinear valve model and a control scheme for a two stage twin spool servo-valve are developed featuring energy saving. The multiple sliding surface mode control method is then utilized to accomplish the motion control while regulating back pressure. The simulation verifies that the proposed control scheme for the twin spool valve, can offer the more significant energy-saving even with load-sensing pump application than the traditional proportional valves.

Adaptive sampling control of high-gain stabilizable systems

Abstract: It is well known that proportional output feedback control can stabilize any relative-degree one, minimum-phase system if the sign of the feedback is correct and the proportional gain is high enough. Moreover, there exist simple adaptation laws for tuning the proportional gain (so-called high-gain adaptive controllers) which do not need to know the system and do not attempt to identify system parameters. In this paper the authors consider sampled versions of the highgain adaptive controller. The motivation for sampling arises from the possibility that the output of a system may not be available continuously, but only at sampled times. The main point of interest is the need to develop techniques for adapting the sampling rate, since the stiffness of the system increases as the proportional gain is increased. Our main result shows that adaptive sampling stabilization is possible if the product hk of the decreasing sampling interval h and the increasing proportional gain k decreases at a rate proportional to 1= log k.

Intelligent control scheme for twin rotor MIMO system

Abstract: This paper presents a control problem involving an experimental propeller setup that is called the twin rotor multi-input multi-output system (TRMS). The control objective is to make the beam of the TRMS move quickly and accurately to the desired attitudes, both the pitch angle and the azimuth angle in the condition of decoupling between two axes. It is difficult to design a suitable controller because of the influence between the two axes and nonlinear movement. For easy demonstration in the vertical and horizontal separately, the TRMS is decoupled by the main rotor and tail rotor. An intelligent control scheme which utilizes a hybrid PID controller is implemented to this problem. Simulation results show that the new approach to the TRMS control problem can improve the tracking performance and reduce control energy.

Separated steering device for vehicular four wheels and its control method

Abstract: The invention relates to domain of special purpose vehicle and especially to a separate four-wheel steering device of vehicle and controlling means, which is mainly used in steering system of special purpose vehicle to guarantee steering behavior. The device comprises steering knuckle arm, steering hydraulic cylinder, electro-hydraulic proportional control valves, and accumulator, easing valve, hydraulic pump, clarifier and electronic control system. The invention is characterized in that every wheel is controlled by independent oil-hydraulic cylinder, electronic control system comprises steering emulator, signal processor and measuring apparatus of displacement line and hydraulic pump driven by engine in steering hydraulic system controls hydraulic cylinder of steering system via electro-hydraulic proportional control valves of steering system. Hydraulic cylinder connects with linear movement pickup to feed variable of displacement line of hydraulic cylinder back to CPU. System adopts closed-loop control. Control circuit equips system failure diagnosis element to realize alarm when system steering error occurs and steering mode switching control unit to complete steering mode switching of vehicle.

Disturbance modeling and control design for self-servo track writing

Abstract: The major disturbances in self-servo track writing are identified and modeled. Based on the disturbance models, an H/sub 2/ controller together with a feedforward compensator is designed via linear matrix inequality approach to minimize the propagation tracking error from one track to the next. Furthermore, the error propagation containment effectiveness of the optimal H/sub 2/ control is compared with that of proportional-integral-derivative (PID) and proportional-derivative (PD) feedback controls with the feedforward compensators. Our results show that the propagation tracking error is improved by 27% with the H/sub 2/ control compared with that by PID control.

Performance control of PMSM drives using a self-tuning PID

Abstract: In this paper a self-tuning PID controller based on generalized minimum variance method is applied to the permanent-magnet synchronous motors (PMSM) speed control system. The proposed method has approximate minimum variance properties, and can guarantee the stability of the close-loop system by pole-assignment, which is based on the discrete-time mechanical equation and dynamic model of the q-axis current control loop of the PMSM drive system. The complete vector control scheme using the self-tuning PID is implemented in real-time based on a digital signal processor (DSP) for a surface PMSM. Comparing conventional PID regulator, the proposed self-tuning regulator makes the speed control of the PMSM drive more robustness and high performance. Experiments are carried out at low and high speeds, results verified the efficacy of the proposed method

Effects of velocity on human force control

Abstract: Although many robots and haptic interfaces are of the impedance type, admittance-type devices offer distinct advantages, such as high damping and stiffness display, particularly in applications requiring precise motion control. This study seeks to quantify human force control limitations in admittance control systems, where robot velocity is controlled to be proportional to the force applied by a human operator. Measurements of human force control in both admittance- and velocity-controlled scenarios were used to quantify force control precision, as well as to find a threshold over which a human cannot control a constant force and determine if that threshold depends on admittance gain or velocity. Experimental results show that robot velocity, not admittance, determines force control precision. Thus, velocities in admittance control systems should be limited to ensure that human force inputs remain precise.

Iterative learning control of electro-hydraulic proportional feeding system in slotting machine for metal bar cropping

Abstract: A non-linear method, iterative learning control (ILC), is proposed to control the electro-hydraulic feeding process of a new slotting machine. The method attempts to acquire high precision of feeding length and trapezoid feedrate, whereas the complexity of iterative learning control algorithm does not increase much more than that of industrial PID controller. After an analysis of the two-way proportional feeding system, a non-linear dynamical mathematic model with system delay, saturation and dead-zone is developed. The computer flowrate control and the ILC controller are investigated in detail. PID controller, ILC of displacement and ILC of feedrate are compared with the dynamical model under the same desired trajectory. It is experimentally found that the proposed control scheme is more effective to improve the tracking accuracy of hydraulic feeding system of the slotting machine than that of fuzzy PID controller.

A hybrid neuro-fuzzy controller for brushless DC motors

Abstract: In this paper, a hybrid neuro-fuzzy controller (NFC) is presented for the speed control of brushless DC motors to improve the control performance of the drive under transient and steady state conditions In the hybrid control system, proportional-derivative (PD) type neuro-fuzzy controller (NFC) is the main tracking controller, and an integral compensator is proposed to compensate the steady state errors A simple and smooth activation mechanism described for integral compensator modifies the control law adaptively The presented BLDC drive has fast tracking capability, less steady state error and robust to load disturbance, and do not need complicated control method Experimental results showing the effectiveness of the proposed control system are presented

Investigating Control Schemes for an Ideal Thermally Coupled Distillation Column (ITCDIC)

Abstract: The control schemes of an ITCDIC are addressed. A modified IMC scheme (M-IMC) is proposed to overcome model/plant mismatch of the Internal Model Control scheme (IMC). Predictive PID control (P-PID) and Adaptive Predictive control (AP-PID) schemes are also presented to improve effectively the response speed of the multi-loop PID control (M-PID) and eliminate its residual error. A detailed comparative investigation on the above five control schemes was performed. Simulation results demonstrate all the schemes are able to keep two end products within their specifications. M-IMC is the best one with the fastest response speed. AP-PID is the second choice since it is better at dealing with sudden set-point transitions and complex external disturbances than P-PID. M-PID cannot compete with AP-PID and P-PID due to its slow servo response speed and large residual error. IMC ranks last as it is extremely sensitive to changes in the operating conditions.

Feedback Control of Manipulator Using Machine Vision for Robotic Apple Harvesting

Abstract: The challenges in developing a fruit harvesting robot are recognizing the fruit in the foliage, detaching the fruit from the tree, and the coordination of the vision system and the hand system. This paper presents the development of a feedback control of manipulator using machine vision. To measure the distance of the fruit from the camera, the laser ranging sensor is used. The detected fruit should be in the center of the image for its distance to be measured, so the camera should be positioned using the manipulator to position the fruit in the center of the image. A feedback control using machine vision is used for this positioning procedure. Two controllers are considered; threeposition on-off controller and proportional controller with variable gain. Both controllers were implemented in a simulation. Simulation results showed that both controllers were able to guide the manipulator to position the fruit in the center of the image.

Steering system with leads and pulls compensation

Abstract: A power assist steering system including a valve housing and a proportional control valve supported within the valve housing, further includes a pressure transducer arranged with respect to the proportional control valve for determining an amount of actuation of the proportional control valve. A pressure signal is sent from the pressure transducer to a control for determining an amount of current to be sent to an electromagnetic apparatus within the power assist steering system for overcoming a pull force.

System, apparatus and method for controlling temperature of an integrated circuit under test

Abstract: A system, apparatus and method for controlling temperature of an integrated circuit in a chip tester is disclosed. Embodiments include supplying a chilled fluid to a cold plate at a first flowrate, where the first flowrate is associated with a first valve setting based on at least a desired temperature setpoint and an applied power. Embodiments may determine a change in applied power and modify the chilled fluid flowrate in response to a change in testing conditions to a second flowrate associated with a second valve setting associated with at least the desired temperature setpoint and the changed testing conditions. This feed forward loop may be supplemented by a feedback loop that includes modifying the energy supplied to a cold plate heater in response to a comparison of a current temperature and the temperature setpoint. The valve may be a proportional control valve or the like.

A coupled sliding-surface approach for the trajectory control of a flexible-link robot based on a distributed dynamic model

Abstract: This paper proposes a coupled sliding-surface method for the design of trajectory control of a flexible-link robot. First, a sliding surface, coupling the joint velocity with the link bending moment at the joint, is defined based on the energy dynamics of the flexible link. Then a new trajectory–tracking control scheme is designed based on the coupled sliding surface, and extended to an adaptive scheme to cope with parametric uncertainties, where the Lyapunov stability theorem is used as a mathematical design tool. The proposed control is a collocated control designed based on a distributed-parameter dynamic model and hence is free from the so-called spillover instability. Using only the joint actuator, the proposed control guarantees stability throughout the entire trajectory control and asymptotic stability at desired goal positions. The proposed control is a PID control for the rigid dynamics and a proportional control for the flexible dynamics, with feed-forward and dynamics compensation. As a result,...

A novel intelligent controller based on modulation of neuroendocrine system

Abstract: Based on the modulation of neuroendocrine system and the hypothalamo-pituitary-adrenal axis model, we present a novel intelligent controller (NEIC). The NEIC, with a typical two-level structure, is composed of a primary control unit and a secondary one. According to the real-time control error, the primary control unit can adjust the control parameters of the secondary unit dynamically based on the hormone-release law. The NEIC can strengthen or weaken control action during the different control error range. The simulation results demonstrate that the NEIC's control stability and adaptability are better than those of the conventional PID controller.

State-feedback-with-integral control plus repetitive control for UPS inverters

Abstract: A new control scheme featuring a combination of state-feedback-with-integral control and repetitive control is proposed for UPS inverters. A state observer is also embedded to predict output voltage and capacitor current needed by the state-feedback controller, based on the sensed values of output voltage and load current. The system exhibits high-dynamic response and near-perfect output voltage waveform

Hybrid robust tracking control for a mobile manipulator via sliding-mode neural network

Abstract: This paper develops a methodology for trajectory tracking control of a nonholonomic wheeled mobile manipulator with uncertainties and external load changes. The proposed control law consists of two levels: kinematics and dynamic levels. First, the auxiliary kinematic velocity control laws for the mobile platform and the onboard manipulator are separately proposed via backstepping. Then, a hybrid robust tracking control system is presented to ensure the velocity tracking ability in spite of the uncertainties. To achieve the goal, a neural network controller is developed to mimic an equivalent control law in the sliding-mode control, a robust controller is designed to incorporate the system dynamics into the sliding surface for guaranteeing the asymptotical stability, and the proportional controller is designed to improve the transient performance for randomly initializing neural network. All the adaptive learning algorithms for sliding-mode neural networks (SMNN) are derived from the Lyapunov stability theory so that the system tracking ability can be guaranteed in the close-loop system no matter the uncertainties occur or not. Simulation results illustrate the feasibility as well as efficacy of the proposed control strategy in comparison with the backstepping method.

Method and device for processing substrate

Abstract: PROBLEM TO BE SOLVED: To keep the floating height of a substrate whereto processing liquid is supplied in a floating carrying method in the proximity of a set value highly accurately. SOLUTION: In a compression air supply mechanism, even if an air pressure of a factory power source 140 which is a primary side pressure of a proportional control valve 146 varies largely, pressure feed back control works by the proportional control valve 146, a pressure sensor 148 and a valve controller 150, and a secondary side pressure of the proportional control valve 146 can be thereby usually made coincide with a set pressure stably. In a vacuum supply mechanism, even if the vacuum pressure of the factory power source 154 which is a primary side pressure of a conductance valve 160 varies largely, pressure feed back control works by the conductance valve 160, the pressure sensor 162, and the valve controller 164; and the secondary side pressure of the conductance valve 160 can be thereby usually made coincide with a set pressure stably. COPYRIGHT: (C)2007,JPO&INPIT

Position control of a pneumatic levitation system

Abstract: The position control of a pneumatic levitation system is described in this paper The control system uses visual feedback to compute the object position, which can be modified by means of an air blower acted by a variable-speed drive The system is employed as a test bed of control strategies A performance comparison attained by a classical PID, a robust Hinfin control law and a fuzzy controller is carried out, including tracking and disturbance rejection experiments