Computer-based Control Research Articles

Controlled environment strategies for tipburn management in greenhouse strawberry production

Greenhouse strawberry production is gaining interest in North America where field production is the primary source of fruit. Issues of off-season greenhouse strawberry production include tipburn, an environmentally induced localized calcium deficiency. Tipburn often increases when nighttime relative humidity (RH) is low (high vapor pressure deficit, VPD) from nighttime heating or venting with dry air in arid climate. High nighttime humidity ( 3 h nighttime high RH (<.1 kPa VPD), guttation was observed and leaf/calyx tipburn severity was low in 'Albion' (5.0±1.1 and 3.0±0.8% respectively) in 2013-2014. However, during 2014-2015, consecutive cold nights in November and December resulted in continuous nighttime heating, eliminating high humidity despite misting, which resulted in severe leaf and calyx tipburn. An additional strategy was implemented for remainder of season, covering plants on nights of anticipated continuous heating. In 2015-2016, a modified strategy of humidification and covering was developed. If 2 consecutive nights were below the 3-h, 95% RH minimum (0.1 kPa VPD maximum) requirement, plants were covered for the subsequent 2 consecutive nights, resulting in acceptably low levels of tipburn incidence (<10%). These practices suggest plants tolerate low humidity nights if Ca supply to the growing shoot tip is periodically restored. Implementation using computer-based nighttime humidity control is discussed.

A Level Training Set with both a Computer-Based Control and a Compact Controller

In engineering education, the combination with theoretical education and practical education is an essential problem.

Design of an Adaptive Human-Machine System Based on Dynamical Pattern Recognition of Cognitive Task-Load.

This paper developed a cognitive task-load (CTL) classification algorithm and allocation strategy to sustain the optimal operator CTL levels over time in safety-critical human-machine integrated systems. An adaptive human-machine system is designed based on a non-linear dynamic CTL classifier, which maps a set of electroencephalogram (EEG) and electrocardiogram (ECG) related features to a few CTL classes. The least-squares support vector machine (LSSVM) is used as dynamic pattern classifier. A series of electrophysiological and performance data acquisition experiments were performed on seven volunteer participants under a simulated process control task environment. The participant-specific dynamic LSSVM model is constructed to classify the instantaneous CTL into five classes at each time instant. The initial feature set, comprising 56 EEG and ECG related features, is reduced to a set of 12 salient features (including 11 EEG-related features) by using the locality preserving projection (LPP) technique. An overall correct classification rate of about 80% is achieved for the 5-class CTL classification problem. Then the predicted CTL is used to adaptively allocate the number of process control tasks between operator and computer-based controller. Simulation results showed that the overall performance of the human-machine system can be improved by using the adaptive automation strategy proposed.

Automated setup for ex vivo larynx experiments.

Ex vivo larynx experiments are limited in time due to degeneration of the laryngeal tissues. In order to acquire a significant and comparable amount of data, automatization of current manual experimental procedures is desirable. A computer controlled, electro-mechanical setup was developed for time-dependent variation of specific physiological parameters, including adduction and elongation level of the vocal folds and glottal flow. The setup offers a standardized method to induce defined forces on the laryngeal cartilages. Furthermore, phonation onset is detected automatically and the subsequent measurement procedure is automated and standardized to improve the efficiency of the experimental process. The setup was validated using four ex vivo porcine larynges, whereas each validation measurement series was executed with one separate larynx. Altogether 31 single measurements were undertaken, which can be summed up to a total experimental time of about 4 min. Vocal fold elongation and adduction lead both to an increase in fundamental frequency and subglottal pressure. Measurement procedures like applying defined subglottal pressure steps and onset-offset detection were reliably executed. The setup allows for a computer-based parameter control, which enables fast experimental execution over a wide range of laryngeal configurations. This maximizes the number of measurements and reduces personal effort compared with manual procedures.

A Level Training Set with both a Computer-Based Control and a Compact Controller

In engineering education, the combination with theoretical education and practical education is an essential problem.

Coalitional Control: Cooperative Game Theory and Control

The evolution of information and communication technologies has yielded the means of sharing measurements and other information in an efficient and flexible way [1], which has enabled the size and complexity of control applications to increase [2]. At the same time, the improvements in the computational and communicational capabilities of control devices have fostered the development of noncentralized control architectures, already motivated by the inherent structural constraints of large-scale systems. Computer-based control approaches such as model predictive control (MPC) are visible beneficiaries of these advances and have registered a significant growth regarding both theoretical and applied fields [3], [4].

Altering user’ acceptance of automation through prior automation exposure

Air navigation service providers worldwide see increased use of automation as one solution to overcome the capacity constraints imbedded in the present air traffic management (ATM) system. However, increased use of automation within any system is dependent on user acceptance. The present research sought to determine if the point at which an individual is no longer willing to accept or cooperate with automation can be manipulated. Forty participants underwent training on a computer-based air traffic control programme, followed by two ATM exercises (order counterbalanced), one with and one without the aid of automation. Results revealed after exposure to a task with automation assistance, user acceptance of high(er) levels of automation (‘tipping point’) decreased; suggesting it is indeed possible to alter automation acceptance.Practitioner Summary: This paper investigates whether the point at which a user of automation rejects automation (i.e. ‘tipping point’) is constant or can be manipulated. The results revealed after exposure to a task with automation assistance, user acceptance of high(er) levels of automation decreased; suggesting it is possible to alter automation acceptance.

A systematic design approach of an embedded-control material-strength testing system

In this paper, an embedded control system is developed to measure the yield strength of the material plate with an applied load. A systematic approach is proposed to handle special requirements of embedded control systems, which are different from computer-based control systems, as there are much less hardware resources and computational power available. An efficient control algorithm has to be designed to remove the CPU burden so that the microcontroller has enough power available. A three-step approach is proposed to address the embedded control issue: firstly, the mathematical description of the whole system is studied using both theoretical and experimental methods. A mathematical model is derived from the physical models of each component used, and an experiment is retrieved by employing Levy’s method and least-square estimation to identify specific parameters of the system model. Secondly, a feedforward plus feedback controller is designed and simulated as a preparation for the embedded system implementation. The cerebellar model articulation controller (CMAC) is chosen as the feedforward part, and a PD controller is used as the feedback part to train the CMAC. Finally, the proposed algorithm is applied in the embedded system, and experiments are conducted to verify both the identified model and designed controller.

Cyber-Physical System Security of a Power Grid: State-of-the-Art

As part of the smart grid development, more and more technologies are developed and deployed on the power grid to enhance the system reliability. A primary purpose of the smart grid is to significantly increase the capability of computer-based remote control and automation. As a result, the level of connectivity has become much higher, and cyber security also becomes a potential threat to the cyber-physical systems (CPSs). In this paper, a survey of the state-of-the-art is conducted on the cyber security of the power grid concerning issues of: (1) the structure of CPSs in a smart grid; (2) cyber vulnerability assessment; (3) cyber protection systems; and (4) testbeds of a CPS. At Washington State University (WSU), the Smart City Testbed (SCT) has been developed to provide a platform to test, analyze and validate defense mechanisms against potential cyber intrusions. A test case is provided in this paper to demonstrate how a testbed helps the study of cyber security and the anomaly detection system (ADS) for substations.

Optimization of the generation of temperature waves in flow metrology

ABSTRACTTemperature waves are used in metrology to determine flow velocities, as well as the coefficient of thermal diffusion, chemical composition, and other parameters of the flowing medium. This study presents a method for precise generation of temperature waves in flows, based on digitally controlled electronic system. A mathematical model and structure of the system implementing the method is described. The system consists of a wire temperature wave transmitter, supplied by the system setting the preset temperature function in time. The mathematical model of such system, together with results of model and optimization testing are presented. The system allows one to generate temperature waves of the shape preset by a digital signal, generated by a computer-based control system. Such a system may be used in analytical instrumentation.

Computer-based controlon mathematical education of the future engineers

There was offered the computer-based management of the scientific-cognitive activity of the future engineers and organization of control on mathematical education using the attainments of the modern information technologies. There were analyzed the e-school-books elaborated by the higher mathematics teachers of the Donbass state academy of mechanical engineering and Donetsk national technical university. There was grounded an expediency of the use of aforesaid school-books during the lectures or independent students’ work and at the control on education of the future specialists of engineer branch that is considered as the category of management as the relatively independent final element of managerial cycle of educational process. There were offered methodological recommendations of the use of e-educational technologies at mathematical studies. There was elucidated how the introduction of educational materials from internet-resource with the access mode http://vmdbi.net.ua/ favors the computer-based control on education: oral questioning of students, written control works, tests and so on. There was proved that the use of offered means at the control on mathematical education gives the possibility to establish the reverse connection at studying mathematics and comprehensively examine the level of knowledge and skills of the studied discipline in students

We’re on a mission. Libraries for the nation. We can do this

Using primary source material, contemporary accounts and personal recollection the author traces the emergence of the National Library of Australia’s confident view of itself as a library for all other Australian libraries, with a special responsibility for computer-based bibliographic control systems at the centre of national library cooperation. The paper focuses on the period 1968–1979, a time of unprecedented growth in library and information services – a time when the computers came.

An Automated Grid-Based Robotic Alignment System for Pick and Place Applications

This paper proposes an automated grid-based alignment system utilizing lasers and an array of light-detecting photodiodes. The intent is to create an inexpensive and scalable alignment system for pick-and-place of industrial objects (titer plates) using a SCARA robot manipulator. The system utilizes the robot trajectory, the transformation matrix, and geometric and trigonometric principles to determine the movements to align the robot with a grid-based array of photodiodes. The alignment system consists of a sending unit utilizing lasers, a receiving module consisting of photodiodes, a data acquisition unit, a computer-based control system, and the robot manipulator. The control system computes the robot movements needed to position the lasers based on laser positions detected by the photodiodes. With a spacing of 10mm between sensors, the system shows a resolution of 0.5mm along both the X and Y-axes, with a maximum single-point X-position detection error of 2.9mm and a maximum single-point Y-position detection error of 2.0mm. After the alignment, the maximum positional errors for both X and Y-position is 1.4mm. With a grid spacing of 10mm from center-to-center between each photodiode, the system still shows a high relative resolution. The results, along with system improvements, show potential for the system being a viable and relatively simple solution for 2D alignment.

An investigation of general predictors for cognitive–behavioural therapy outcome for anxiety disorders in a routine clinical setting

IntroductionCognitive–behavioural therapy (CBT) is effective for treating anxiety disorders and is offered in most mental health services around the world. However, a relatively large number of patients with anxiety disorders...

Monitoring the Turmeric Finger Disease and Growth Characteristics Using Sensor Based Embedded System —A Novel Method

In this cyber era, novelty plays a prime role in the field of agriculture that majorly depends on computer-based measurements and control. Herein before, it was totally controlled and performed by the agriculturists. One of the technological innovative methods to measure and monitor the turmeric finger growth characteristics is the embedded system that is based on sensor array module such as flex sensor, temperature sensor and pH sensor. The experimental work has been designed and tested with five set of nodes and the growth of turmeric finger is tenuously monitored by measuring the change in flex resistance. Out of five nodes, two nodes were diseased. Deliberately, one node was left as such and the other node was treated with natural pesticides (pseudomonas and viride) to restrict the rhizome rot disease attack. After cultivation, it was found that the rhizome rot disease attack on the node which was treated with pesticides was comparatively lesser than the other node. The five different nodes have been used in the experimental work with an average flex sensor resistance of 3.962 cm/kΩ. In a nutshell, this proposed method manifests the farmers to detect the rhizome rot disease at its earlier stage and to prevent it as well by screening the growth of the turmeric fingers when it is under the soil.

Study of a Computer-Based Control System with Fault-Tolerant and Fail-Safe Behavior

Abstract The software and hardware of Safety Critical Systems - SCS, which control special critical technology process or operation, are subject of enhanced requirements for reliability and inadmissibility of any incorrect controlling influences (safety) after failures. This paper suggests and investigates a hybrid computerbased fail-safe/fault-tolerance FST-structure with single reservation, which has the qualities to meet these requirements. The base system 2 ∨ 2, based on which it is built, is studied in the previous edition of Information Technjlogies and Control. For derivation of probabilistic models through which to establish the efficiency of the strutucral redundancy in a fault-tolerant structure, in this paper are used the published results. Formulas are derived for the probability of failure-free operation (availability coefficient), for safe failure and for unidentified (dangerous) failure. Models are found for calculation of the enhancement of reliability and the variation of safety relative to the base system 2 ∨ 2. Subject of analysis are type software and hardware modifications of the proposed general scheme used in the practice of different companies, which manufacture and operate SCSs. It is proven that at the expense of acceptable hardware redundancy and insignificant increase of dangerous failures the probability of interruption of the operation of the FST- system and its down-time due to failure may decrease by tenths of thousands of times.

Reliability benefit of smart grid technologies: A case for South Africa

The South African power industry faces many challenges, from poor performing networks, a shortage of generation capacity to significant infrastructure backlog and an ageing work force. According to the Development Bank of South Africa (DBSA), the key challenge facing the industry is ageing infrastructure. Smart grid technologies are a class of technologies that are being developed and used by utilities to deliver electrical systems into the 21st century using computer-based remote control and automation. The main motive towards smart grid technologies is to improve reliability, flexibility, accessibility and profitability; as well as to support trends towards a more sustainable energy supply. This study identifies a number of smart grid technologies and examines the impact they may have on the distribution reliability of a test system. The components on the selected test system are the same as those found on a South African feeder. The bulk of the load in test system was modelled using load data collected in South Africa. This study will consider a number of different cases, with the base case incorporating the impact of aged infrastructure on the reliability of the system. The smart grid technologies were then introduced into the system and their impact on distribution reliability was determined. These different cases were also compared to the alternative of replacing the aged and worn out infrastructure with new infrastructure. The findings of this study indicate that the identified smart grid technologies improve the reliability of the system, mainly by decreasing the outage duration experienced by customers on the network. An even better performance was achieved when the ageing infrastructure was replaced with new infrastructure.

Automatic irrigation scheduling of apple trees using theoretical crop water stress index with an innovative dynamic threshold

An adaptive scheduling algorithm relying on a theoretical crop water stress index (CWSI) was developed to automatically irrigate apple trees. Unlike the traditional CWSI algorithm where the threshold is a constant value, in the present approach the threshold is dynamically determined by following the CWSI trend. A previous work on the energy budget analysis of a single apple leaf provided the base for calculating lower and upper boundaries of CWSI. To test the feasibility of the algorithm, it was applied to the thermal and meteorological data collected during the 2007 and 2008 growing seasons. A computer-based wireless control system was also developed to automatically schedule irrigations in three plots of apple trees in the 2013 growing season. In a small scale field experiment, two treatments were compared: (1) automatic irrigation using the new algorithm (CWSI-DT) and (2) irrigation scheduling based on weekly readings of neutron probe (NP). The soil water deficit under the CWSI-DT treatment was maintained within the well-watered range with no signs of over or under irrigation. This was better than the results in the NP treatment where there were occasions of under irrigation. Midday canopy and air temperature difference (ΔTm) exhibited a close agreement with midday stem water potential (Ψstem; R2=0.63, p<0.01). Normalizing ΔTm in the form of CWSI resulted in a much higher correlation between midday CWSI and midday Ψstem (R2=0.91, p<0.0001) suggesting CWSI as a reliable indicator of apple trees water status. The automatic control system running the new CWSI-DT algorithm was able to avoid over-irrigation under humid and cool weather conditions, and adapted itself to the changing conditions of the apple trees. The results of this study were promising in terms of using ground-based thermal sensing for automatic irrigation scheduling of sparse, discontinuous apple trees.

Co-Aperture Transceiving of Two Combined Beams Based on Adaptive Fiber Coupling Control

We demonstrate the reception and transmission of fiber laser beams using two-element adaptive fiber-optics collimator (AFOC) array under simulated turbulences. Coupling efficiency of laser beam from free space into polarization maintaining fibers is optimized with tip/tilt aberration correction. According to the principle of optical reciprocity, tip/tilt errors of the phase-conjugated collimating laser beams are compensated simultaneously. The average of normalized coupling efficiency of one AFOC increases from 0.61 without control to 0.85 under control and 0.57 to 0.85 for another. The average of diffraction-pattern centroid’s deviation of two outgoing combined beams in the far-field drops from $17.5~\mu $ rad to $2.35~\mu $ rad, and mean-square-error value drops from 6.59 to $1.35~\mu $ rad. Control bandwidth of 30 Hz for tip/tilt correction is achieved with computer-based stochastic parallel gradient descent controller with update rate of 1.15 kHz. Results indicate the potential value of the AFOC array in fiber coupling, laser communication and beam projection applications.

Tracking transience: a method for dynamic monitoring of biological events in Arabidopsis thaliana biosensors.

The activation and level of expression of an endogenous, stress-responsive biosensor (bioreporter) can be visualized in real-time and non-destructively using highly accessible equipment (fluorometer). Biosensor output can be linked to computer-controlled systems to enable feedback-based control of a greenhouse environment. Today's agriculture requires an ability to precisely and rapidly assess the physiological stress status of plants in order to optimize crop yield. Here we describe the implementation and utility of a detection system based on a simple fluorometer design for real-time, continuous, and non-destructive monitoring of a genetically engineered biosensor plant. We report the responses to heat stress of Arabidopsis thaliana plants expressing a Yellow Fluorescent Protein bioreporter under the control of the DREB2A temperature-sensing promoter. Use of this bioreporter provides the ability to identify transient and steady-state behavior of gene activation in response to stress, and serves as an interface for novel experimental protocols. Models identified through such experiments inform the development of computer-based feedback control systems for the greenhouse environment, based on in situ monitoring of mature plants. More broadly, the work here provides a basis for informing biologists and engineers about the kinetics of bioreporter constructs, and also about ways in which other fluorescent protein constructs could be integrated into automated control systems.