Showing papers on "Proportional control published in 2006"

Passive Bilateral Teleoperation With Constant Time Delay

Abstract: We propose a novel control framework for bilateral teleoperation of a pair of multi-degree-of-freedom nonlinear robotic systems under constant communication delays. The proposed framework uses the simple proportional-derivative control, i.e., the master and slave robots are directly connected via spring and damper over the delayed communication channels. Using the controller passivity concept, the Lyapunov-Krasovskii technique, and Parseval's identity, we can passify the combination of the delayed communication and control blocks altogether robustly, as long as the delays are finite constants and an upper bound for the round-trip delay is known. Having explicit position feedback through the delayed P-action, the proposed framework enforces master-slave position coordination, which is often compromised in the conventional scattering-based teleoperation. The proposed control framework provides humans with extended physiological proprioception, so that s/he can affect and sense the remote slave environments mainly relying on her/his musculoskeletal systems. Simulation and experiments are performed to validate and highlight properties of the proposed control framework

New self-tuning fuzzy PI control of a novel doubly salient permanent-magnet motor drive

Abstract: In a doubly salient permanent-magnet (DSPM) motor drive, it is difficult to get satisfied control characteristics by using a normal linear proportional plus integral (PI) controller due to the high nonlinearity between speed and current or torque. Hence, a new self-tuning fuzzy PI controller with conditional integral, which is performed by a single-chip N87C196KD, is proposed. The initial parameters of the controller are optimized by using genetic arithmetic. Simulation and experiments on the newly proposed 8/6-pole DSPM machine have shown that the proposed new self-tuning fuzzy PI controller offers better adaptability than the normal linear PI control and that the developed motor drive offers better steady-state and dynamic performances.

Integration of saturated PI synchronous control and PD feedback for control of parallel manipulators

Abstract: High-precision motion of parallel manipulators depends not only on the position accuracy of each actuator, but also on the position synchronization of all actuators. This paper presents a simple synchronized control algorithm for the setpoint position control of parallel manipulators, by incorporating cross-coupling technology into a common proportional-derivative (PD) control architecture. An integrated controller is developed, consisting of a PD control and a saturated proportional-integral (S-PI) control with feedback of the differential position errors amongst actuators (defined as the synchronization errors). The controller can stabilize the motion of each actuator, and meanwhile synchronize all actuators' motions so that both position and synchronization errors converge to zero. The control algorithm does not use the modeling parameters in the controller formulation, and thus permits easy implementation in practice. It is proved that the proposed method can guarantee global asymptotical stability of the system. Experiments conducted on a planar three-degree-of-freedom parallel manipulator demonstrate the effectiveness of the proposed approach.

Combined Feedback Linearization and Constrained Model Predictive Control for Entry Flight

Abstract: The advantages of constrained model predictive control over proportional integral derivative (PID) control applied to a feedback-linearized entry flight-control problem are discussed. The feedback linearization is based on the full rotational equations of motion rather than on a conventional model derived from time-scale separation. Input and state constraints are applied to avoid input saturations, to guarantee a minimum level of tracking performance, and to avoid physical vehicle state constraints violation. A constraint mapping algorithm is developed to map the input and state constraints on the new inputs after feedback linearization. The performance of the constrained model predictive control design is compared with that of two PID control designs. Simulation of a complete entry flight demonstrates the advantages of the constrained model predictive control design, because control surfaces do not saturate, control actions are more smooth and efficient, no gain scheduling is required, and all performance requirements are satisfied.

Neuroadaptive Combined Lateral and Longitudinal Control of Highway Vehicles Using RBF Networks

Abstract: A neural network (NN) adaptive model-based combined lateral and longitudinal vehicle control algorithm for highway applications is presented in this paper. The controller is synthesized using a proportional plus derivative control coupled with an online adaptive neural module that acts as a dynamic compensator to counteract inherent model discrepancies, strong nonlinearities, and coupling effects. The closed-loop stability issues of this combined control scheme are analyzed using a Lyapunov-based method. The neurocontrol approach can guarantee the uniform ultimate bounds of the tracking errors and bounds of NN weights. A complex nonlinear three-degree-of-freedom dynamic model of a passenger wagon is developed to simulate the vehicle motion and for controller design. The controller is tested and verified via computer simulations in the presence of parametric uncertainties and severe driving conditions

Image Based Visual Servoing through Nonlinear Model Predictive Control

Abstract: Image based visual servoing (IBVS) is a vision sensor based control architecture. In classical approach, an image Jacobian matrix maps image space errors into errors in Cartesian space. Then a simple proportional control law can be applied guaranteeing local convergence to a desired set point. One of the main advantage of IBVS is its robustness w.r.t camera and robot calibration errors and image measurement errors. Nevertheless, this scheme can not deal with nonlinear constraint such as joint limits and actuator saturation. Visibility constraint is not ensured with classical IBVS. A new IBVS scheme based on Nonlinear Model Predictive Control (NMPC) is proposed considering the direct dynamic model of the robot, its joint and torque limits, the camera projection model and the visibility constraint. Simulations exhibit the efficiency and the robustness of the proposed solution to control a 6 degrees of freedom mechanical system.

Design of feedback controls supporting TCP based on the state-space approach

Abstract: This paper investigates how to design feedback controls supporting transmission control protocol (TCP) based on the state-space approach for the linearized system of the well-known additive increase multiplicative decrease (AIMD) dynamic model. We formulate the feedback control design problem as state-space models without assuming its structure in advance. Thereby, we get three results that have not been observed by previous studies on the congestion control problem. 1) In order to fully support TCP, we need a proportional-derivative (PD)-type state-feedback control structure in terms of queue length (or RTT: round trip time). This backs up the conjecture in the networking literature that the AQM RED is not enough to control TCP dynamic behavior, where RED can be classified as a P-type AQM (or as an output feedback control for the linearized AIMD model). 2) In order to fully support TCP in the presence of delays, we derive delay-dependent feedback control structures to compensate for delays explicitly under the assumption that RTT, capacity and number of sources are known, where all existing AQMs including RED, REM/PI and AVQ are delay-independent controls. 3) In an attempt to interpret different AQM structures in a unified manner rather than to compare them via simulations, we propose a PID-type mathematical framework using integral control action. As a performance index to measure the deviation of the closed-loop system from an equilibrium point, we use a linear quadratic (LQ) cost of the transients of state and control variables such as queue length, aggregate rate, jitter in the aggregate rate, and congestion measure. Stabilizing gains of the feedback control structures are obtained minimizing the LQ cost. Then, we discuss the impact of the control structure on performance using the PID-type mathematical framework. All results are extended to the case of multiple links and heterogeneous delays.

Control of a pwm inverter using proportional plus extended time-delayed feedback

Abstract: Pulse width modulation (PWM) current-mode single phase inverters are known to exhibit bifurcations and chaos when parameters vary or if the gain of the proportional controller is arbitrarily increa

Active control of structures using time delayed positive feedback proportional control designs

Abstract: This paper explores a new methodology for the active control of structures through the use of time delayed, positive feedback proportional control. The idea is to utilize intentional time delays, which may not necessarily be small when compared with the natural periods of vibration of a structure. Such time delayed systems are infinite dimensional. Analytical and computational results related to both system and non-system poles are herein provided for the first time. Results related to the stability of the presented control methodology are given. The efficacy of the control design is illustrated by applying it to a structure modelled as a single-degree-of-freedom system subjected to strong earthquake ground shaking. It is shown that while displaying good stability characteristics, the performance of such time delayed positive feedback proportional control can be even superior—in terms of both, reduced structural response, and reduced control effort—to standard proportional negative feedback control designs with no time delay. Copyright © 2005 John Wiley & Sons, Ltd.

Precise motion control of a nanopositioning PZT microstage using integrated capacitive displacement sensors

Abstract: We propose a hysteresis and drift compensation scheme using proportional-integral feedback control for a nanopositioning Pb(ZrTi)O3 (PZT) microstage. A multi-degree of freedom PZT microstage with integrated differential capacitive displacement sensors has been fabricated and tested, demonstrating the feasibility of compensating for hysteresis and creep. The feedback signal to the PZT actuators is fed from differential capacitive sensors of the displacement of the microstage. Experimental results show that the sensitivity of the displacement sensor is approximately 0.53 V µm−1. A maximum resolution of 16 nm is achieved when hysteresis is compensated for, and the minimum detectable variation of capacitance ΔC is 1.25 × 10−3 pF. The hysteresis of the system varies with the proportional gain Kp, integral time constant Ti and reference input frequency. By using feedback control with a proportional and integration (PI) controller, the hysteresis decreases from 30% in open-loop operation to approximately 1% in closed-loop operation at a gain of 20, when the frequency of the sine reference input is 1 Hz and Ti is 20 ms. Efficient compensation of hysteresis is validated by the closed-loop control, especially when the frequency of the reference input is low. Elimination of creep/drift is also verified by the closed-loop control.

Applying a counter-based PWM control scheme to an FPGA-based SR forward converter

Abstract: In this paper, a field programmable gate arrays (FPGA) technique applied to a forward converter with synchronous rectification (SR) is utilized to design a pulse-width-modulation (PWM) proportional-integral-derivative (PID) controller, along with protection peripherals. With only one comparator and without any analog-to-digital converter (ADC), the information on the feedback output voltage is entirely obtained according to a counter, thereby causing full digitalization and easy implementation of this control topology using system on programmable chip (SOPC). In this paper, the detailed operation of such a control topology is described, along with some experimental results to demonstrate its effectiveness.

PID control of laser surface hardening of steel

Abstract: We discuss control strategies for the laser surface hardening of steel. The goal is to achieve a prescribed hardening depth avoiding surface melting. Our mathematical model consists of a system of ordinary differential equations (ODEs) for the phase volume fractions coupled with the heat equation. The system is solved semi-implicitely using the finite element method. To obtain a uniform hardening depth the first attempt is to use proportional integral differential (PID) control to achieve a constant temperature in the hot spot of the laser beam on the surface. However, the numerical results prove that this is not sufficient. We show that the best strategy is to control the temperature close to the lower boundary of the hardening zone. Then one can compute the optimal temperature in the hot spot of the beam and use it as the setpoint for the pyrometer control of the real process

Integrated Play-Back, Sensing, and Networked Control

Abstract: Sensing, actuation, and decision units can control a remote physical environment and enable physical actions regardless of distance. However, the effectiveness of networked control depends on its ability to tolerate network non-determinism, which in turn can be enhanced by the use of play-back buffers. Although play-back has been intensively studied in multi-media applications, play-back schemes differ significantly in networked control, which is characterized by different performance metrics and a different sequence of communication events. The primary contribution of this paper is an end-to-end algorithm that integrates play-back buffering, sensor sampling, and control. The algorithm is extensively validated on simulations and realtime wide-area emulations. The integrated algorithm canceled the effect of disturbances as much as a proportional controller under ideal network conditions.

Neural model adaptation and predictive control of a chemical process rig

Abstract: An adaptation algorithm for Gaussian radial basis function (RBF) network models is proposed. The model structure is adapted to cope with operating region change, while the weight parameters are updated to model time varying dynamics or uncertainties. The special feature is that the modeling accuracy is maintained during adaptation and, therefore, the control performance will not be degraded when the model structure changes. A localized forgetting method is proposed to deal with nonlinearities in different operating regions, and is implemented with the recursive orthogonal least squares (ROLS) training algorithm. The developed adaptive model is evaluated by real data modeling of a three-input three-output chemical process rig. Online model predictive control (MPC) of the rig is also conducted. Improved tracking performance with the adaptive model is demonstrated in comparison with nonadaptive model-based control and decentralized propotional-integral-differential (PID) control

Control of linear full vehicle active suspension system using Sliding Mode techniques

Abstract: For the purpose of fault diagnosis and accommodation, a Sliding Mode Controller (SMC) is designed for a linear full vehicle active suspension system An investigation about the available sensors for the controller implementation is also presented Two levels are studied: the level of vehicle prototypes and the level of industrial vehicles Difficulties of vehicle instrumentation and possible solutions are discussed Simulation is made to illustrate the proposed controller where the active suspension system performances are compared with those of passive suspension

A learning scheme for low-speed precision tracking control of hybrid stepping motors

Abstract: Servo control of the hybrid stepping motor is complicated due to its highly nonlinear torque-current-position characteristics, especially under low operating speeds. This paper presents a simple and efficient control algorithm for the high-precision tracking control of hybrid stepping motors. The principles of learning control have been exploited to minimize the motor's torque ripple, which is periodic and nonlinear in the system states, with specific emphasis on low-speed situations. The proposed algorithm utilizes a fixed proportional-derivative (PD) feedback controller to stabilize the transient dynamics of the servomotor and the feedforward learning controller to compensate for the effect of the torque ripple and other disturbances for improved tracking accuracy. The stability and convergence performance of the learning control scheme is presented. It has been found that all error signals in the learning control system are bounded and the motion trajectory converges to the desired value asymptotically. The experimental results demonstrated the effectiveness and performance of the proposed algorithm.

An Advanced Control Scheme for Micro Hydro Power Plants

Abstract: Micro hydropower plants are emerging as a major renewable energy resource today as they do not encounter the problems of population displacement and environmental problems associated with the large hydro power plants. However, they require control systems to limit the huge variation in input flows expected in rivulets over which these are established to produce a constant power supply. This paper proposes an electric servomotor as a governor for a micro hydro power plant especially those plants that are operated in isolated mode. An advanced controller is developed combining four control schemes for the control of the governor following the concept that the control action can be split up into linear and non linear parts. The linear part of this controller contains an adaptive fast transversal filter (FTF) algorithm and normalized LMS (nLMS) algorithm. The non-linear part of the controller incorporates fuzzy PI and a neural network. The new controller has a superior performance over other control schemes.

Systematized procedure for parameter characterization of a variable-speed drive used in photovoltaic pumping applications

Abstract: This work presents a systematized procedure for the parameter characterization of a variable-speed drive (VSD) for use in applications to photovoltaic pumping systems (PVPS). The study focuses on the process of the PID controller's tuning of the VSD, in order to optimize the configuration. In this work, three methods of tuning are analyzed and the results show that the methods based on the system's response in open-loop are the most suitable, as well as the use of only the integral proportional control actions (PI). Copyright © 2005 John Wiley & Sons, Ltd.

Stabilization of an arbitrary order transfer function with time delay using PI and PD controllers

Abstract: This paper is concerned with developing a procedure for stabilizing a linear time-invariant plant of any order with time delay utilizing proportional-integral (PI) and proportional-derivative (PD) controllers. The method presented here is based on computing the stability boundary in terms of the proportional and integral gain for the PI case, and similarly, proportional and derivative gain for the PD case. The two variables are then plotted on the same coordinate system, thus obtaining the stability region for each controller used. The advantage of this procedure is the fact that it does not require the knowledge of the plant transfer function parameters, but only its frequency response. In addition, if the plant function is known, the procedure may also be used to analytically obtain the stabilizing controllers. We also present the tuning rules for user specified gain and phase margins.

EHB proportional solenoid valve with stepped gap armature

Abstract: A control valve includes a magnetic pole member. An armature is slidably supported relative to the magnetic pole member for movement between a fully open position and a closed position. A biasing spring is disposed between the magnetic pole member and the armature for forcing the armature away from the magnetic pole member. A coil is placed about the magnetic pole member and the armature for inducing a magnetic field for moving the armature toward the magnetic pole member. One of either of the magnetic pole member or the armature has a recess for non-contactingly receiving the other when the armature moves between the fully open and closed positions. The control valve can be embodied as a normally open valve or a normally closed valve. The use of dual lateral poles and triple lateral poles create a flat magnetic force versus travel curve thereby allowing for greater proportional control of the valve. Additionally, the use of double lateral gaps and triple lateral gaps respectively results in force increases of 21% and 12% respectively. Compounding the force increases results in a net additional force of 36%.

Design and tuning method of PID controller for a class of inverse response processes

Abstract: Inverse response processes are difficult to be controlled due to presence of right half plant (RHP) zeros. In this paper, firstly the RHP zeros are approximated to the form of dead time in terms of Pade approximation theory. Thus, the controlled processes can be regarded as general stable processes plus dead time without RHP zeros. Then based on the internal model control (IMC) structure, an analytical PID controller design procedure is developed for the transformed inverse response processes. The resulting controller includes a single adjustable control parameter. Through stability analysis for the proposed control system, the stable range of the control parameter is derived according to a simple method called dual-locus diagram, and meanwhile, the sufficient and necessary condition for holding the proposed closed-loop system robust stability is provided. By monotonously tuning the single controller parameter, the good compromise between the nominal performance and robust stability of the closed loop system can be realized. The simulation example demonstrates the superiority of the proposed control scheme.

Feedback stabilization of RWM with in-vessel coils

Abstract: Active control of the resistive wall modes (RWMs) is analysed for the feedback system with internal correction coils (ICs) The analysis is performed using a single mode thin-wall model in the cylindrical approximation and proportional control Three cases are considered: with radial field sensors, poloidal field sensors inside the vessel and poloidal sensors outside It is shown that, within the model, the systems with such sensors and proportional feedback have similar characteristics The feedback systems with internal and external correction coils are compared and advantages of the IC system are shown

Design and Analysis of a Self-Tuning Proportional and Integral Controller for Active Queue Management Routers to Support TCP Flows

Abstract: Active Queue Management (AQM) is an effective method used in Internet routers for congestion control, and to achieve a tradeoff between link utilization and delay. The de facto standard, the Random Early Detection (RED) AQM scheme, and most of its variants use average queue length as a congestion indicator to trigger packet dropping. This paper proposes a novel AQM algorithm, called Self-tuning Proportional and Integral RED (SPI-RED), as an extension of RED. SPI-RED is based on a Self-tuning Proportional and Integral controller, which not only considers the average queue length at the current time point, but also takes into consideration the past average queue lengths during a round-trip time. Furthermore, we give theoretical analysis of the system stability and give guidelines for the selection of feedback gains for the TCP/RED system to stabilize the average queue length at a desirable level. Extensive simulations have been conducted with ns2. The simulation results have demonstrated that the proposed SPI-RED algorithm outperforms the existing AQM schemes in terms of drop probability and stability. Keywords– Active queue management, Random early detection (RED), Congestion control, Internet traffic control, Internet Router, TCP.

A unified force controller for a proportional-injector direct-injection monopropellant-powered actuator

Abstract: This paper describes the modeling and control of a proportional-injector direct-injection monopropellant powered actuator for use in power-autonomous human-scale mobile robots. The development and use of proportional (as opposed to solenoid) injection valves enables a continuous and unified input/output description of the device, and therefore enables the development and implementation of a sliding-mode-type controller for the force control of the proposed actuator that provides the stability guarantees characteristic of a sliding mode control approach. Specifically, a three-input, singleoutput model of the actuation system behavior is developed, which takes a nonlinear noncontrol-canonical form. In order to implement a nonlinear controller, a constraint structure is developed that effectively renders the system single-input, single-output and control canonical, and thus of appropriate form for the implementation of a sliding mode controller. A sliding mode controller is then developed and experimentally implemented on the proposed actuator. Experimental results demonstrate closed loop force tracking with a saturation-limited bandwidth of approximately 6 Hz.

Stability Control of Railway Bogies Using Absolute Stiffness: Sky-Hook Spring Approach

Abstract: This paper presents a novel control method for the stabilization of railway bogies using a strategy based on the concept of an absolute stiffness, in which the control effort is proportional to the yaw movement of the wheelset alone. The idea can be considered as if a spring is connected between the sky and a wheelset, hence termed a 'sky-hook spring'. In this paper, the effectiveness of the control strategy is studied in detail and compared with other control solutions. It is shown that the new approach offers a number of advantages: it provides a robust control solution for the stability of railway wheelsets and there is no need for the measurement of bogie motions or the use of secondary yaw dampers. Sensing requirement can be readily met and control design is relatively simple.

Development and experimental evaluation of a fixed-gain nonlinear control for a low-cost pneumatic actuator

Abstract: A practical, easy-to-implement and accurate fixed-gain nonlinear position controller for a typical low-cost industrial pneumatic actuator is developed and evaluated experimentally. The positioning system comprises an inexpensive 5-port three-way proportional control valve with flow deadband, and a double-rod actuator exhibiting significant dry friction. Quantitative feedback theory is used first to systematically design a robust proportional–integral (PI) control law that minimises variations in the dynamic response of the actuator over a wide range of operating conditions and in the presence of uncertainty in the system parameters. Nonlinear modifications, which condition the integral part of the designed PI control law, are then implemented in a step-by-step fashion to further improve closed-loop performance by reducing overshoot and negating the effects of the control valve deadband and actuator friction. Experimental results clearly illustrating the effectiveness of the positioning system for a number of tracking and regulating tasks are presented.

Analysis and design of an automatic motion inverter

Abstract: In this paper, the design of an automatic motion-inverter control system for agricultural tractors has been discussed. The objective of this system is to perform a fully automatic symmetric motion inversion (e.g., from a forward speed of 10 km/h to a reverse speed of -10 km/h). The device used to control the inversion is electro-hydraulic reverser, constituted by two clutches, driven by a proportional electro-hydraulic valve (EVP) and a directional electro-hydraulic valve (EVD). The design of a motion inverter is a nontrivial task, since it is difficult to find a good compromise between speed (the inversion must be completed in a short time) and comfort (bumps and oscillations on the longitudinal speed must be minimized). All the subtasks of the inversion control systems are considered: The design of an inner loop for the control of the EVP current, the open-loop switching strategies, and the design of the outer control loop, which regulates the vehicle speed. The control strategies are experimentally validated, and satisfactory results are obtained.