Showing papers on "Open-loop controller published in 2009"

A Predictive Controller for Autonomous Vehicle Path Tracking

Abstract: This paper presents a model predictive controller (MPC) structure for solving the path-tracking problem of terrestrial autonomous vehicles. To achieve the desired performance during high-speed driving, the controller architecture considers both the kinematic and the dynamic control in a cascade structure. Our study contains a comparative study between two kinematic linear predictive control strategies: The first strategy is based on the successive linearization concept, and the other strategy combines a local reference frame with an approaching path strategy. Our goal is to search for the strategy that best comprises the performance and hardware-cost criteria. For the dynamic controller, a decentralized predictive controller based on a linearized model of the vehicle is used. Practical experiments obtained using an autonomous ldquoMini-Bajardquo vehicle equipped with an embedded computing system are presented. These results confirm that the proposed MPC structure is the solution that better matches the target criteria.

Reinforcement Learning Versus Model Predictive Control: A Comparison on a Power System Problem

Abstract: This paper compares reinforcement learning (RL) with model predictive control (MPC) in a unified framework and reports experimental results of their application to the synthesis of a controller for a nonlinear and deterministic electrical power oscillations damping problem. Both families of methods are based on the formulation of the control problem as a discrete-time optimal control problem. The considered MPC approach exploits an analytical model of the system dynamics and cost function and computes open-loop policies by applying an interior-point solver to a minimization problem in which the system dynamics are represented by equality constraints. The considered RL approach infers in a model-free way closed-loop policies from a set of system trajectories and instantaneous cost values by solving a sequence of batch-mode supervised learning problems. The results obtained provide insight into the pros and cons of the two approaches and show that RL may certainly be competitive with MPC even in contexts where a good deterministic system model is available.

PID-Like Neural Network Nonlinear Adaptive Control for Uncertain Multivariable Motion Control Systems

Abstract: A mix locally recurrent neural network was used to create a proportional-integral-derivative (PID)-like neural network nonlinear adaptive controller for uncertain multivariable single-input/multi-output system. It is composed of a neural network with no more than three neural nodes in hidden layer, and there are included an activation feedback and an output feedback, respectively, in a hidden layer. Such a special structure makes the exterior feature of the neural network controller able to become a P, PI, PD, or PID controller as needed. The closed-loop error between directly measured output and expected value of the system is chosen to be the input of the controller. Only a group of initial weights values, which can run the controlled closed-loop system stably, are required to be determined. The proposed controller can update weights of the neural network online according to errors caused by uncertain factors of system such as modeling error and external disturbance, based on stable learning rate. The resilient back-propagation algorithm with sign instead of the gradient is used to update the network weights. The basic ideas, techniques, and system stability proof were presented in detail. Finally, actual experiments both of single and double inverted pendulums were implemented, and the comparison of effectiveness between the proposed controller and the linear optimal regulator were given.

Application of self-tuning fuzzy pid controller on industrial hydraulic actuator using system identification approach

Abstract: In this paper, Self Tuning Fuzzy PID controller is developed to improve the performance of the electro-hydraulic actuator. The controller is designed based on the mathematical model of the system which is estimated by using System Identification technique. The model is performed in a linear discrete model to obtain a discrete transfer function for the system. Model estimation procedures are done by using System Identification Toolbox in Matlab. Data for model estimation is taken from experimental works. Fuzzy logic is used to tune each parameter of PID controller. Through simulation in Matlab by selecting appropriate fuzzy rules are designed to tune the parameters Kp, Ki, and Kd of the PID controller, the performance of the hydraulic system has improved significantly compare to conventional PID controller.

Position Control of DC Motor Using Genetic Algorithm Based PID Controller

Abstract: The aim of this paper is to design a position controller of a DC motor by selection of a PID parameters using genetic algorithm. The model of a DC motor is considered as a third order system. And this paper compares two kinds of tuning methods of parameter for PID controller. One is the controller design by the genetic algorithm, second is the controller design by the Ziegler and Nichols method. It was found that the proposed PID parameters adjustment by the genetic algorithm is better than the Ziegler & Nichols' method. The proposed method could be applied to the higher order system also.

Small-Signal Model-Based Control Strategy for Balancing Individual DC Capacitor Voltages in Cascade Multilevel Inverter-Based STATCOM

Abstract: This paper presents a new feedback control strategy for balancing individual DC capacitor voltages in a three-phase cascade multilevel inverter-based static synchronous compensator. The design of the control strategy is based on the detailed small-signal model. The key part of the proposed controller is a compensator to cancel the variation parts in the model. The controller can balance individual DC capacitor voltages when H-bridges run with different switching patterns and have parameter variations. It has two advantages: 1) the controller can work well in all operation modes (the capacitive mode, the inductive mode, and the standby mode) and 2) the impact of the individual DC voltage controller on the voltage quality is small. Simulation results and experimental results verify the performance of the controller.

Making a commercial atomic force microscope more accurate and faster using positive position feedback control

Abstract: This paper presents experimental implementation of a positive position feedback (PPF) control scheme for vibration and cross-coupling compensation of a piezoelectric tube scanner in a commercial atomic force microscope (AFM). The AFM is a device capable of generating images with extremely high resolutions down to the atomic level. It is also being used in applications that involve manipulation of matter at a nanoscale. Early AFMs were operated in open loop. Consequently, they were susceptible to piezoelectric creep, thermal drift, hysteresis nonlinearity, and scan-induced vibration. These effects tend to distort the generated image and slow down the scanning speed of the device. Recently, a new generation of AFMs has emerged that utilizes position sensors to measure displacements of the scanner in three dimensions. These AFMs are equipped with feedback control loops that work to minimize the adverse effects of hysteresis, piezoelectric creep, and thermal drift on the obtained image using proportional-plus-integral (PI) controllers. These feedback controllers are often not designed to deal with the highly resonant nature of an AFM's scanner nor with the cross coupling between various axes. In this paper we illustrate the improvement in accuracy and imaging speed that can be achieved by using a properly designed feedback controller such as a PPF controller. Such controllers can be incorporated into most modern AFMs with minimal effort since they can be implemented in software with the existing hardware. Experimental results show that by implementing the PPF control scheme, relatively good images in comparison with a well-tuned PI controller can still be obtained up to line scan of 60 Hz.

Touchless control of a control device

Abstract: A method and a system are provided for controlling a controller without physically touching the controller. A hand or other object interacts with a field surrounding the controller, altering the field. A change in characteristic of the altered filed causes a corresponding movement of the controller that, in turn, corresponds to an amount of change ina parameter of a target device being controlled by the controller. The parameter of the target device is controlled by the controller while a user has no physical contact with the controller.

Further results on event-based PID controller

Abstract: In this paper, some improvements of the simple event-based PID controller presented by K-E A rzen in [2] are proposed. This controller, contrary to a time-triggered controller which calculates the control signal at each sampling time, calculates the new control signal only when the measurement signal sufficiently changes. In the original work of A rzen, a safety maximum period is added forcing the control to be recomputed even if the measurement signal remains unchanged. The contribution of this paper is to propose a scheme to avoid this re-computation. Besides a noticeable reduction of the mean control computation cost, the performance of the closed loop system is also improved.

Arbitrary Decay Rate for Euler-Bernoulli Beam by Backstepping Boundary Feedback

Abstract: We consider a problem of stabilization of the Euler-Bernoulli beam. The beam is controlled at one end (using position and moment actuators) and has the ldquoslidingrdquo boundary condition at the opposite end. We design the controllers that achieve any prescribed decay rate of the closed loop system, removing a long-standing limitation of classical ldquoboundary damperrdquo controllers. The idea of the control design is to use the well-known representation of the Euler-Bernoulli beam model through the Schrodinger equation, and then adapt recently developed backstepping designs for the latter in order to stabilize the beam. We derive the explicit integral transformation (and its inverse) of the closed-loop system into an exponentially stable target system. The transformation is of a novel Volterra/Fredholm type. The design is illustrated with simulations.

Direct synthesis-based controller design for integrating processes with time delay

Abstract: Using the direct synthesis method, a PID controller in series with a lead/lag compensator is designed for control of open loop integrating processes with time delay. Set-point weighting is considered for reducing the undesirable overshoot. Guidelines are provided for selection of the desired closed loop tuning parameter in the direct synthesis method and set point weighting parameter. The method gives significant load disturbance rejection performances. Illustrative examples are considered to show the performances of the proposed method. Significant improvement is obtained when compared to recently reported methods.

A Fast-Acting DC-Link Voltage Controller for Three-Phase DSTATCOM to Compensate AC and DC Loads

Abstract: The transient response of the distribution static compensator (DSTATCOM) is very important while compensating rapidly varying unbalanced and nonlinear loads. Any change in the load affects the dc-link voltage directly. The sudden removal of load would result in an increase in the dc-link voltage above the reference value, whereas a sudden increase in load would reduce the dc-link voltage below its reference value. The proper operation of DSTATCOM requires variation of the dc-link voltage within the prescribed limits. Conventionally, a proportional-integral (PI) controller is used to maintain the dc-link voltage to the reference value. It uses deviation of the capacitor voltage from its reference value as its input. However, the transient response of the conventional PI dc-link voltage controller is slow. In this paper, a fast-acting dc-link voltage controller based on the energy of a dc-link capacitor is proposed. Mathematical equations are given to compute the gains of the conventional controller based on fast-acting dc-link voltage controllers to achieve similar fast transient response. The detailed simulation and experimental studies are carried out to validate the proposed controller.

Event-driven intermittent control

Abstract: An intermittent controller with fixed sampling interval is recast as an event-driven controller. The key aspect of intermittent control that makes this possible is the use of basis functions, or, equivalently, a generalised hold, to generate the intersample open-loop control signal. The controller incorporates both feedforward events in response to known signals and feedback events in response to detected disturbances. The latter feature makes use of an extended basis-function generator to generate open-loop predictions of states to be compared with measured or observed states. Intermittent control is based on an underlying continuous-time controller; it is emphasised that the design of this continuous-time controller is important, particularly in the presence of input disturbances. Illustrative simulation examples are given.

Quadrilateral Modelling and Robust Control of a Nonlinear Piezoelectric Cantilever

Abstract: Piezocantilevers are commonly used for the actuation of micromechatronic systems. These systems are generally used to perform micromanipulation tasks which require high positioning accuracy. However, the nonlinearities, i.e., the hysteresis and the creep, of piezoelectric materials and the influence of the environment (vibrations, temperature change, etc.) create difficulties for such a performance to be achieved. Various models have been used to take into account the nonlinearities but they are often complex. In this paper, we study a one degree of freedom piezoelectric cantilever. For that, we propose a simple new model where the hysteresis curve is approximated by a quadrilateral and the creep is considered to be a disturbance. To facilitate the modelling, we first demonstrate that the dynamic hysteresis of the piezocantilever is equivalent to a static hysteresis, i.e., a varying gain, in series with a linear dynamic part. The obtained model is used to synthesize a linear robust controller, making it possible to achieve the performances required in micromanipulation tasks. The experimental results show the relevance of the combination of the developed model and the synthesized robust H infin controller.

Simultaneous tracking and balancing of humanoid robots for imitating human motion capture data

Abstract: This paper presents a control framework for humanoid robots that uses all joints simultaneously to track motion capture data and maintain balance The controller comprises two main components: a balance controller and a tracking controller The balance controller uses a regulator designed for a simplified humanoid model to obtain the desired input to keep balance based on the current state of the robot The simplified model is chosen so that a regulator can be designed systematically using, for example, optimal control An example of such controller is a linear quadratic regulator designed for an inverted pendulum model The desired inputs are typically the center of pressure and/or torques of some representative joints The tracking controller then computes the joint torques that minimize the difference from desired inputs as well as the error from desired joint accelerations to track the motion capture data, considering exact full-body dynamics We demonstrate that the proposed controller effectively reproduces different styles of storytelling motion using dynamics simulation considering limitations in hardware

Robust Yaw Stability Controller Design and Hardware-in-the-Loop Testing for a Road Vehicle

Abstract: Unsymmetrical loading on a car like mu-split braking, side wind forces, or unilateral loss of tire pressure results in unexpected yaw disturbances that require yaw stabilization either by the driver or by an automatic driver-assist system. The use of two-degrees-of-freedom control architecture known as the model regulator is investigated here as a robust steering controller for such yaw stabilization tasks in a driver-assist system. The yaw stability-enhancing steering controller is designed in the parameter space to satisfy a frequency-domain mixed sensitivity constraint. To evaluate the resulting controller design, a real-time hardware-in-the-loop simulator is developed. Steering tests with and without the controller in this hardware-in-the-loop setup allow the driver to see the effect of the proposed controller to improve vehicle-handling quality. The hardware-in-the-loop simulation setup can also be used for real-time driver-in-the-loop simulation of other vehicle control systems.

Setting Up PID DC Motor Speed Control Alteration Parameters Using Particle Swarm Optimization Strategy

Abstract: In this paper, an intelligent controller of DC Motor drive is designed using particle swarm optimization (PSO) method for formative the optimal proportional-integral-derivative (PID) controller Tuning parameters. The proposed approach has superior feature, including easy implementation, stable convergence characteristics and very good computational performances efficiency. The DC Motor Scheduling PID-PSO controller is modeled in MATLAB environment. Comparing with fuzzy logic controller using PSO intelligent algorithms, the planned method is more proficient in improving the speed loop response stability, the steady state error is reduced, the rising time is perfected and the disturbances do not affect the performances of driving motor with no overtaking.

Stabilization of Networked Control Systems via Dynamic Output-Feedback Controllers

Abstract: This paper investigates the problem of stabilization of networked control systems via dynamic output-feedback controllers. The physical plant and the dynamic controller are in continuous time, and a communication channel exists between the output of the physical plant and the input of the dynamic controller. Three important communication features are considered: measurement quantization, signal transmission delay, and data packet dropout, which appear typically in a networked environment. Attention is focused on the design of dynamic output-feedback controllers which ensure asymptotic stability of the closed-loop systems. Linear matrix inequality (LMI)-based conditions are formulated for the existence of admissible controllers. If these conditions are satisfied, a desired controller can be readily constructed. A satellite system is used to illustrate the applicability and effectiveness of the proposed controller design method.

A Third-Order Sliding-Mode Controller for a Stepper Motor

Abstract: This paper deals with the robust control problem of a stepper motor subject to parameter uncertainties and load torque perturbation. The developed algorithm is based on third-order sliding-mode control such that a desired angular motor position is accurately tracked. The proposed scheme requires the measurement or the estimation of the motor speed and acceleration for feedback. To avoid the use of tachometers and accelerometers which add cost and energy consumption, a robust second-order sliding-mode observer is presented. Experimental results illustrate the performance and the advantages of the proposed controller.

Automatic path-tracking controller of a four-wheel steering vehicle

Abstract: The present paper proposes an automatic path-tracking controller of a four-wheel steering (4WS) vehicle based on the sliding mode control theory. The controller has an advantage in that the front- and rear-wheel steering can be decoupled at the front and rear control points, which are defined as centres of percussion with respect to the rear and front wheels, respectively. Numerical simulations using a 27-degree-of-freedom vehicle model demonstrated the following characteristics: (1) the automatic 4WS controller has a more stable and more precise path-tracking capability than the 2WS controller, and (2) the automatic 4WS controller has robust stability against system uncertainties such as cornering power perturbation, path radius fluctuation, and cross-wind disturbance.

A model-driven multivariable controller for vapor compression refrigeration systems

Abstract: A model-driven controller for vapor compression refrigeration systems is presented herein. Mathematical sub-models were developed for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The overall system simulation model was used to design a MIMO controller based on the linear-quadratic Gaussian method using a state observer of the Kalman filter type. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification and model validation exercises. It was found that the model reproduces the experimental trends of the working pressures in conditions far from the operation point (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the controller of tracking reference changes and rejecting thermal load disturbances as high as 15%.

FPGA Implementation of an Embedded Robust Adaptive Controller for Autonomous Omnidirectional Mobile Platform

Abstract: This paper presents an embedded adaptive robust controller for trajectory tracking and stabilization of an omnidirectional mobile platform with parameter variations and uncertainties caused by friction and slip. Based on a dynamic model of the platform, the adaptive controller to achieve point stabilization, trajectory tracking, and path following is synthesized via the adaptive backstepping approach. This robust adaptive controller is then implemented into a high-performance field-programmable gate array chip using hardware/software codesign technique and system-on-a-programmable-chip design concept with a reusable user intellectual property core library. Furthermore, a soft-core processor and a real-time operating system are embedded into the same chip for realizing the control law to steer the mobile platform. Simulation results are conducted to show the effectiveness and merit of the proposed control method in comparison with a conventional proportional-integral feedback controller. The performance and applicability of the proposed embedded adaptive controller are exemplified by conducting several experiments on an autonomous omnidirectional mobile robot.

Drive-Mode Control for Vibrational MEMS Gyroscopes

Abstract: This paper presents a novel design methodology and hardware implementation for the drive-mode control of vibrational micro-electro-mechanical systems gyroscopes. Assuming that the sense mode (axis) of the gyroscope is operating under open loop, the drive-mode controller compensates an undesirable mechanical spring-coupling term between the two vibrating modes, attenuates the effect of mechanical-thermal noise, and most importantly, forces the output of the drive mode to oscillate along a desired trajectory. The stability and robustness of the control system are successfully justified through frequency-domain analysis. The tracking error between the real output and the reference signal for the drive mode is proved to be converging with the increase of the bandwidth of the controller. The controller is first simulated and then implemented using field-programmable analog array circuits on a vibrational piezoelectric beam gyroscope. The simulation and experimental results verified the effectiveness of the controller.