Pseudo-derivative Feedback Controller Research Articles

Environmental control for plants using intelligent control systems

Greenhouses provide a protected environment in which crops can be grown under a tightly controlled climate. The efficiency of plant production in greenhouses depends significantly on the adjustment of optimal climate growth conditions to achieve high production at low expense, good quality and low environment load. To achieve these goals several components, temperature and air humidity, must be optimally contro, lled through heating, ventilation, humidification and/or dehumidification. This paper focuses on the control of greenhouse air temperature and humidity ratio by means of simultaneous ventilation and humidification. The control process is divided into two distinct control loops, one maintaining the temperature by adjusting the ventilation rate, and the other maintaining the humidity ratio by adjusting the water capacity of the fog system. Several types of conventional control structures are employed to control the greenhouse environments, however, their parameters should be tuned if the operating conditions are changed. Fuzzy logic controllers are more flexible compared with these conventional controllers. This paper introduces Fuzzy Pseudo-Derivative Feedback (FPDF) controller that results from the fertelization of the PDF controller with fuzzy set theory. The parameters of the classical PDF and the FPDF controllers were optimized using a genetic algorithm (GA). Best results were achieved using the proposed controllers compared with the conventional PDF controller

Pseudo-derivative feedback-based identification of unstable processes with application to bioreactors

The use of a pseudo-derivative feedback structure for closed-loop parameter identification of unstable first-order plus dead-time processes is investigated in this paper. Two alternative identification methods are presented. The proposed identification methods require small computational effort and they are particularly useful for on-line applications. The new methods and the simpler structure of the pseudo-derivative feedback controller used ensure considerably smoother response (i.e., less overshoot), than other well-known identification methods based on standard PI/PID controllers, and better accuracy along with simplicity in implementation. The synergism of intelligent tools, which can be based on functional and linguistic rules for advanced decisions at the supervisory level, with low-level process PD-0F controllers and identifiers, can provide adaptive systems. These can optimize for both the long-term objectives and the short-term process dynamics.

Pseudo-Derivative Feedback Based Identification of Unstable Processes with Application to a Bioreactor

The use of a pseudo-derivative feedback structure for parameter identification of unstable first order plus dead-time processes is investigated. Two alternative identification methods are presented. The proposed identification methods require small computational effort and they are particularly useful for on-line applications. They ensure considerably smoother response (i.e. less overshoot), than known identification methods based on standard PI/PID controllers, while providing better accuracy and more simplicity in implementation, due to the simpler structure of the pseudo-derivative feedback controller used.

Electro-hydraulic proportional control of twin-cylinder hydraulic elevators

The large size of the cab of an electro-hydraulic elevator necessitates the arrangement of two cylinders located symmetrically on both sides of the cab. This paper reports the design of an electro-hydraulic system which consists of three flow-control proportional valves. Speed regulation of the cab and synchronization control of the two cylinders are also presented. A pseudo-derivative feedback (PDF) controller is applied to obtain a velocity pattern of the cab that proves to be close to the given one. The non-synchronous error of the two cylinders is kept within ±2 mm with a constrained step proportional-derivative (PD) controller. A solenoid-actuated non-return valve, i.e. a hydraulic lock, is also developed to prevent cab sinking and allow easy inverse-fluid flow.

Application of pseudo-derivative-feedback algorithm in greenhouse air temperature control

Pseudo-Derivative-Feedback (PDF) control is compared to PI control through simulation using an approximated dynamic system thermal model of the greenhouse. The effects of time delays on control system performance for both PDF and PI control are demonstrated. Results showed PDF control to have a better load handling capability than PI control. PDF control was exceptionally better than PI for systems without time delay and significantly better for systems with time delay. The algorithm was then tested to control a greenhouse section and showed satisfactory results.

Simulation of Greenhouse Air Temperature Control Using PI and PDF Algorithms

Pseudo-Derivative-Feedback (PDF) control is compared to PI control through simulation using an approximated dynamic system thermal model of the greenhouse. The effects of time delays on control system performance for both PDF and PI control are demonstrated. Results showed PDF control to have a better load handling capability than fI control. PDF control was exceptionally better than PI for systems without time delay and significantly better for systems with time delay.

Stability of PDF Controller With Stick-Slip Friction Device

This paper presents the precision control of drive devices with significant stick-slip friction. The controller design follows the Pseudo-Derivative Feedback (PDF) control algorithm. Using the second order system model, the PDF controller offers arbitrary pole placement. In this paper, the stability proof for the controller with stick-slip friction is presented. On the basis of this proof, the stability criteria are derived. The paper also includes both the computer simulation and the experimental works to confirm the theoretical result. The experiments conducted on a Traction Type Drive Device (TTDD) shows that control accuracy of as high as ±1 arc – second is achieved.

Compensation of tool axis misalignment in active magnetic bearing spindle system

The tool axis misalignment, which causes machining inaccuracies in an active magnetic bearing (AMB)-spindle system, can be compensated by tracking control of the rotor-spindle. The pseudo-derivative feedback (PDF) control scheme alone does not correct the tool axis misalignment since the integral action results in the narrow bandwidth and large phase lag in the controlled system. To improve the tracking performance, the feedback and feedforward controllers are combined with the existing proportional-derivative controller, which stabilizes the inherently unstable AMB-spindle system dynamics. The theoretical and experimental results show that proposed control scheme efficiently compensates the tool axis misalignment compared with the conventional PDF control scheme.

Fuzzy PD Control Applied to a Flexible Link Manipulator

This paper describes the application of a fuzzy PD control system to a manipulator with a single flexible link. Fuzzy systems which are inherently parallel lend themselves easily to implementation on a transputer system and should be able to take advantage of the parallel processing capabilities of transputer implementation. The system is evaluated in terms of control performance and speed. Simulation results show that the Fuzzy PD system performs better than the more conventional P, PD, PID and Pseudo Derivative Feedback (PDF) control schemes. Comparisons in performance between the transputer implementation and a simulation model written in advanced Continuous Simulation Language (ACSL) are also presented.

Control characteristics and speed controller design for a high performance permanent magnet synchronous motor drive

The theory of vector control is applied to the nonlinear model of a permanent magnet synchronous motor to develop a linear model for controller design purposes. The operation and relevant mathematics of a pseudo-derivative feedback controller are presented. Controller designs for three different speeds are then considered, and a comparative evaluation is made on the basis of their large and small-signal behavior. In order to test the large-signal response, the detailed nonlinear model of the machine and a real-time model of the inverter switches are used. Results indicate that a critically damped design done so as to ensure that all control and power signals never saturate gives an extremely poor result. Much better small and large-signal responses are achieved by avoiding this constraint and using Zener diodes instead to limit the commanded input into the inverter. Two designs using this technique are presented, an underdamped design with low speed overshoot and an overdamped design with no speed overshoot. The response of the underdamped design was much quicker than that of the overdamped. However the overdamped design has application when speed overshoot is intolerable.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The design of autopilots using the pseudo-derivative feedback algorithm

This paper is concerned with a simple method for the design of autopilots for ships, on an automatic-control-design technique termed pseudo-derivative feedback control. When properly tuned, such controllers are known to possess good transient behaviour when their set-point is altered and to be extremely good alleviating output deviations due to step-changes imposed by external loads disturbing the system. This latter properly appears to carry over when the disturbances are sinusoidal and, by implication, stochastic in form. Such behaviour is generally achieved with modest ammounts of final control-element (e.g. rudder) activity. Evaluation of the autopilot design has been done by simulation using mathematical models of the steering dynamics of a Mariner Class vessel. The evidence to date is that such autopilots may be expected to exhibit robust properties and warrant further detailed investigation.