A high-stability air temperature control system

There are many design methods for the multiloop control system, but a method to exactly evaluate the stability margin for multiloop control systems has not been established yet. It is very important for the designers to exactly know the stability margin of the flight control system, because it directly comes to bear on flight safety. Previous research has proposed the “-1/ξ locus” analysis method for the exact evaluation of the stability margin of multiloop flight control systems. -1/ξ is an open loop transfer function of multiloop control systems that is considered as an extension of that for single-loop control systems. In this paper, the relation between the response of the closed loop and the stability margin is considered by using the -1/ξ locus. Lateral-directional flight control system was taken for instance, important points to pay attention to use the -1/ξ locus method for designing the flight control system are presented.

The applicability of the steady-state Relative Gain Array (RGA) to measure dynamic process interactions in a multiloop control system was investigated. Several transfer function matrices were chosen, and the gains, time constants, and dead times of their elements were varied to represent the systems with dominant dynamic interactions. It was shown that the steady-state RGA method predicted the controller pairing accurately if the pairing elements recommended by RGA had the bigger gains and the same or smaller time constants compared to other elements in the corresponding rows. When these conditions were not met, the RGA would give a wrong result, and dynamic interaction measurements, such as the Average Dynamic Gain Array (ADGA) and the Inverse Nyquist Array (lNA), should be used instead to determine the best controller pairing in a multiloop control system. Keywords: Control pairing, dynamic process interaction, multiloop control systems, Relative Gain Array (RGA), and steady state.

This work is devoted to the technique of solving the problem of structural-parametric synthesis of typical controllers in a multiloop cascade automatic control system, which is developed on the basis of the alternance method of parametric optimization that provides the maximum degree of invariance of local control loops relative to external perturbations with given limitations on the peak of amplitude-frequency characteristics of closed loops of the synthesized automatic control system. The task of optimizing the subsystem for controlling the fuel oil temperature in a multiloop control system of primary oil refining on an atmospheric and vacuum crude distillation unit is considered as an example, which is of independent interest.

The cooperative control of both electrode remelting rate and position was applied in order to obtain optimal electro-slag remelting metallurgy effect and improve melting production efficiency. The nonlinear dynamic model of electro-slag remelting process was linearized. And the lineariztion model was analyzed including its stability, coupling property and variable matching strategy. The multi-loop PID controllers with cascade PID controllers were applied to the linearization model based on matching strategy. The dynamic performance was analyzed to electro-slag remelting control system. Study results show that linearizition model of electro-slag remelting process have characteristic of stability and weakly-coupled property. Multi-loop PID control system can realize stable control both electrode melting rate and electrode position. The control system has faster dynamic response and better anti-interference capability.

The paper presents the algorithm of a simultaneous control of multiple HVDC links and series FACTS devices (such as phase angle regulator) to improve stability of an AC power system. The purpose of the study is to demonstrate that such stabilizing control, optimal from the perspective of the whole AC power system and insensitive to the loading condition and network configuration (robust control) may be clearly determined mathematically. The proposed method of control was derived using the direct Lyapunov method. The control system is a multi-loop control system using state variables as input signal, activated in the transient state and supplementary to the main steady-state control designed for regulating the power flow. Efficiency of the methods was confirmed with computer simulations. The algorithm perfectly damps the inter-area power swings, showing at this very high robustness to changes in network configuration, loading conditions. Moreover, the proposed control produces additive damping i.e. each controlled HVDC line and/or FACTS device contributes to positive damping in AC power system.

A Filter Based Approach for Estimation of PI Achievable Performance

Singular value analysis can give conservative stability margin results. Applying structure to the uncertainty can reduce this conservatism. This paper presents flight-determined stability margins for the X-29A lateral-directional, multiloop control system. These margins are compared with the predicted unscaled singular values and scaled structured singular values. The algorithm was further evaluated with flight data by changing the roll-rate-to-aileron command-feedback gain by +/- 20 percent. Minimum eigenvalues of the return difference matrix which bound the singular values are also presented. Extracting multiloop singular values from flight data and analyzing the feedback gain variations validates this technique as a measure of robustness. This analysis can be used for near-real-time flight monitoring and safety testing.

In recent years, the egg industry in Iowa has been under pressure to transition to cage-free housing for egg-laying hens. As such, aviaries are becoming an increasingly common alternative housing method being implemented by egg producers in Iowa. However, a concern for many in the egg industry is the increased energy usage and electric utility costs associated with aviaries. To offset these costs, the manure drying process, one of the most energy-intensive processes in egg production, was identified as the target for this research in developing a method for improvements in energy efficiency. Common industry practice is to run the manure drying blowers continuously at full speed without adjusting for changes in environmental conditions. It was hypothesized that the changes in air velocity moving over the manure, air temperature, and relative humidity (RH) will all influence the drying rate of poultry manure. To test this hypothesis, an experiment was performed in which manure samples were dried under a range of simulated aviary conditions. The resulting data was used to produce a mathematical model of the poultry manure drying rate with respect to air velocity and temperature. The effects of RH were found to be insignificant. Using this model, a control system was developed to modulate the speed of the blower motors to provide only the minimum amount of air required for manure drying. By reducing the rotational speed of the blower motors, exponential energy savings can be expected due to the relationships between rotational speed and power consumption given by the affinity law. The economic benefits that this control system may have can vary throughout the year and across the state of Iowa. GIS maps were created to analyze the influence that changes in temperature and utility rates may have on an egg producer's electric costs. It was shown that during the winter months, little to no change in utility costs can be expected as the air temperatures are not high enough to facilitate accelerated drying rates. The highest reduction in utility costs can be seen during the summer months, where in some parts of the state it is expected that the manure drying blowers can be turned off completely, resulting in up to a 60% savings in energy usage and electrical utility costs.

Aiming at the influence of driving speed, air temperature, wind speed and other nonlinear factors on driving, the traditional PID has poor ability to adjust adaptively temperature, which it is difficult to meet the needs of self-adaptive temperature adjustment about the electric vehicle gloves. So a temperature control and thermal insulation system based on adaptive fuzzy PID for electric vehicle gloves is designed in this article. According to the fuzzy rule, the error and the rate of error change between the actual temperature and the set value of gloves are deduced, the increment DKp, DKi, DKd of Kp, Ki, Kd are obtained, then the PID control parameter Kp, Ki, Kd can be further adjusted to meet the needs of adaptive adjusting gloves temperature in different environments. The system adopts STM32F103C8T6 micro controller, voice recognition and player module, human body induction module and other sensors for hardware design, software design and experimental verification. Experimental result shows that contrasting the traditional PID control system the design in this paper significantly improves the temperature control accuracy of electric vehicle gloves, with less overshoot and stronger robustness. It is great significance to improve the reliability of the real-time temperature control system in different environments and the comfortable sensation of wearing for electric vehicle glove.

MICROCLIMATE CONTROL IN GREENHOUSES BASED ON PHYTOMONITORING DATA AND MOLLIER PHASE DIAGRAM

Age-of-information (AoI) is a metric quantifying information freshness at the receiver. Since AoI combines packet generation frequency, packet loss, and delay into a single metric, it has received a lot of research attention as an interface between communication network and application. In this work, we apply AoI to the problem of wireless scheduling for multi-loop networked control systems (NCS), i.e., feedback control loops closed over a shared wireless network. We model the scheduling problem as a Markov decision process (MDP) with AoI as its observable states and derive a relation of control system error and AoI. We further derive a stationary scheduling policy to minimize control error over an infinite horizon. We show that our scheduler outperforms the state-of-the-art scheduling policies for NCS. To the best of our knowledge, this is the first work proposing an AoI-based wireless scheduling policy that minimizes the control error over an infinite horizon for multi-loop NCS.

Three-Spool Marine Gas Turbine Multi-Objective Switching Control System Design and Optimization

A multi-loop plasma position and current control system in the Globus-M tokamak (Ioffe Institute, St. Petersburg, Russia) has been developed and modelled on a new evolution plasma code designed in MATLAB. Robust PID controllers in the plasma position control loops were tuned by the Quantitative Feedback Theory (QFT) based on the identified linear model of a nonlinear single-phase thyristor current inverter as a self-oscillating actuator.

The non-weighing lysimeter system in the Minqin desert areas was firstly used in the 1970 s, and mainly performed the orientation research on the water consumption by the transpiration of several desert plants and the evaporation on the surface of sand, which aimed to provide the theoretical guide for the selection of afforestation density and the utilization of sand and water in Chinese sand areas. At present the system has been running for 30 years, most of the lysimeters showed the jam and leakage phenomenon, and the observation was by conventional artificial means. All the factors seriously affected the accuracy of the data monitoring. However, on the basis of the non-weighing lysimeter system structure and its testing principle, the evapotranspiration area could be extended, the capacity of testing soil column could be increased, more real natural environment conditions could be simulated and the limitations of weighing lysimeter could be overcome, in sum, the lysimeter's application field and adaptability were extended. Owing to the problems of low automation, and lack of scalability and reliability, the non-weighed lysimeter monitoring and control system in the Minqin desert areas has been retrofitted to improve its performance based on structure characteristics. The non-weighed lysimeter proving ground of 720 m2was designed in Minqin sand areas, where 30 individual lysimeters (120 cm×120 cm) of desert plant were upgraded and 12 small groups of desert plant lysimeters (400 cm×400 cm) were expanded and built, at the same time, the lysimeter groups in different types could be used to carry out the test of water supply for plant under the constant water level of 190, 290 and 390 cm. The lysimeter proving ground upgraded and expanding-built could realize synchronous observation for evapotranspiration test from the desert plant individual scale to small group scale, and the experiment platform was provided for studying water consumption of desert plants transpiration in different scale and its coupling relationship. The distributed monitoring scheme was adopted in the new automatic monitoring system, in which the superior industrial computer was set up as the center with multiple lower machine monitoring points, such as lysimeter constant water level control and water-supplying measurement system, drainage measurement system, atmospheric precipitation monitoring system, soil moisture monitoring system, environment temperature measurement and control system, SMS cat alarm system, data remote transmission and monitoring system, and UPS over-voltage protection system, and the RS485 bus, ISM wireless communication and TCP/IP network structure were used in the system. The automatic control of the lysimeter water level, water supply and drainage, the automatic monitoring of water metering, and the soil water content were designed, and the atmospheric rainfall and the temperature indoor were monitored in real time in the new system; the system also had the functions of real-time data collection and processing, information communication and data entering, historical data storage, data report printing and remote transmission download, and the power supply system was protected against over-voltage to enhance the reliability of system operation and the stability of data acquisition. Additionally, the internet-based remote monitoring and control system was used, and the users could process the abnormal situation. According to the monitoring data analysis by the regression method, we could know that the errors of data regression analysis were ± 2.2% for the pressure sensor, ± 2.0% for the drop counter and ± 12.5% for the moisture sensors. The research extended the scale for locating observation of the desert plant and implemented the automatic monitoring for evapotranspiration of the desert plant. © 2015, Chinese Society of Agricultural Engineering. All right reserved.

Hybrid air/liquid cooling systems used in data centers enable localized, on-demand cooling, or “smart cooling” using various approaches such as rear door heat exchangers, overhead cooling systems and in row cooling systems. These systems offer the potential to achieve higher energy efficiency by providing local cooling only when it is needed, thereby reducing the overprovisioning that is endemic to traditional systems. At the heart of all hybrid cooling systems is an air to liquid cross flow heat exchanger which regulates the amount of cooling that the system provides by modulating the liquid or air flows or temperatures. Understanding the transient response of the heat exchanger is crucial for the precise control of the system. The aim of this work is the development of a rear door heat exchanger compact model using Artificial Neural Networks (ANN). The transient behavior of the heat exchanger is studied using a Finite Difference (FD) model. Different temperatures perturbations are introduced in the heat exchanger model to study its transient response. The finite different results are then used to train an ANN compact model. Both models are compared in terms of accuracy and computational resources.