Data Acquisition And Control System Research Articles

The control and data acquisition system of a laser in-vessel viewing system

This paper presents the dedicated control and data acquisition system (CADAS) of a new laser in-vessel viewing system that has been developed for inspection purposes in fusion experiments. CADAS is based on a MC68060 microprocessor and on-site developed VME instrumentation. Its main aims are to simultaneously control the laser alignment system as well as the laser beam deflection for in-vessel scanning, acquire a high-resolution image and support real-time data flow rates up to 2 Mbyte/s from the acquisition modules to the hard disk and network. The hardware (modules for control and alignment acquisition, scanning acquisition and monitoring) as well as the three levels of software are described.

DETERMINATION OF THE PRODUCT REFRIGERATION LOAD IN VACUUM COOLING OF LETTUCE

This article discusses the relationship between product refrigeration load and vacuum rate for the vacuumcooling of lettuce. A theoretical relationship is developed based on evaporation temperature of water as a function ofpressure and the rate at which the pressure decreases in a vacuum cooler. It was assumed that the temperature of theproduct followed the evaporation temperature of water. The slope of the temperature-time function was used as a measureof the rate of heat transfer from the lettuce, and of the product refrigeration load. A laboratory-scale vacuum cooler, withair leaks controlled by solenoid valves, was modified so the retort pressure could be controlled using a data acquisitionand control system. Air entered the retort at a rate such that the pressure of the retort decreased in an exponential mannerat different rates to simulate various sizes of vacuum pumps. Lettuce was instrumented with thermocouples to measure thetemperature throughout the cooling process. Using the collected data from different vacuum rates, the maximum slope ofthe temperature-time data was determined and used to calculate the maximum product refrigeration load. These resultswere compared to the theoretical predictions. An empirical model was developed to predict the peak refrigeration loadbased on the experimental data. It was observed that there was a heat transfer lag when the vacuum rate was high,though the lag decreased when the rate of vacuum application was reduced. Results from this study allow for the peakproduct refrigeration load to be predicted based on the volume of the retort and the mass of the lettuce to be cooled.

CODAS: The JET Control and Data Acquisition System

The hardware and software structure of the control and data acquisition system (CODAS) of the Joint European Torus is described. CODAS is a large distributed real-time process control system. The operation is centralized in two adjacent control rooms through a fully programmable man-machine interface. The plant interface is based on CAM AC instrumentation and Eurocard signal conditioning. The system is based on a network of minicomputers with a link to a host mainframe.

Authors

Authors

The JET Magnet Power Supplies and Plasma Control Systems

During a Joint European Torus pulse, the main tokamak loads [the toroidal coils, the transformer coils, the plasma equilibrium coils, and the additional heating devices (not described in this work)] require a total amount of energy of 10000 MJ and a peak power in excess of 1000 MW.The main power source is the U.K.’s Central Electricity Generating Boards’ electric power system supplemented by two identical local motor flywheel generators.Since the tokamak loads require a direct-current (dc) supply, the alternating-current power from the energy sources is converted into dc by a combination of thyristor bridges (static units for the plasma position and shaping control, for the additional heating devices, and partially for the toroidal coils) and diode bridges, directly connected to the output of the two generators for the tokamak transformer coils and partially for the toroidal coils.The ohmic heating circuit modulates the flow of power from the flywheel generator to the transformer coils, and its duty is to establish and control the plasma current: It can deliver currents up to 80 kA and supply voltages up to 40 kV. Together with the static units (poloidal vertical, poloidal radial, and poloidal shaping magnetic field amplifiers) to control the plasma position and shape, it constitutes the poloidal circuit.The toroidal circuit is made up of two toroidal field (TF) static units and by the other flywheel generator conventor: It produces and controls the TF current during the pulse, with a maximum current of 67 kA and maximum voltage of 9 kV.The operation of the power supplies is coordinated by the control and data acquisition system (CODAS), which supplies approximate waveforms to each power supply controller, following a predetermined sequence of commands issued by the central timing system.The plasma position and current control is made up of a feedback system built in a conventional way, using magnetic probes and flux loops as sensors and analog electronics for measurement of position, comparitors, and controllers. The control voltages are transmitted to the power sources of the poloidal field to control plasma current, plasma position, and shape.Experimental evidence of the correct functioning of all power supplies and of their control is given by summarizing the key features of a 3.65-MA pulse.

Controls and data acquisition for the NRL modified betatron accelerator

A CAMAC based data acquisition and control system (DACS) has been developed for the NRL modified betatron accelerator. The design goal of the MBA is to accelerate single-shot multi-kA currents of electrons to 50 MeV. The DACS must perform three general tasks: (1) the control and shot sequencing of the accelerator, (2) the data acquisition of MBA shot data and (3) the archiving of the shot conditions, shot digitizer data, and oscilloscope data. A VAX 11 750 controlled system crate contains a serial highway driver that communicates with CAMAC crates in three remote locations via fiberoptic links. The DACS utilizes sensing and feedback to control capacitor banks, high vacuum pumping systems, high speed digitizers and the precision infector accelerator during shot sequencing. A control program written at NRL invokes CAMAC functions to perform shot sequencing, provide data acquisition, and archiving. The computer actuates switches that control equipment subsystems by operating relay logic and interlocking. Thus, the computer control functions in parallel with manual controls. The DACS logs the conditions before and after MBA shots. It also archives data acquired form the buffer memories of transient digitizers and from a PDP 11 23 controlled vidicon camera that digitizes oscilloscope photographs.

Status of the JET control and data acquisition system CODAS

This paper presents the current status of the JET Control and Data Acquisition System (CODAS). This system is the result of the effort of the whole CODAS team.

Modified Betatron Accelerator Data Acquisition and Control System

This article describes the planning and implementation of the NRL Modified Betatron Accelerator (MBA) data acquisition and control system (DACS). The design goal of the MBA is to accelerate multi-kiloampere electron beam pulses to 50 MeV. It employs an applied toroidal magnetic field in addition to the rising vertical fields of a conventional Betatron. Theoretical studies show that the toroidal field improves the stability and equilibrium properties of the device at high currents. The accelerator hardware consists of three capacitor banks, the precision injector accelerator, toroidal and vertical field coils, vacuum chamber and pumping system, and intense relativistic electron beam diode. The task of the DACS is to conduct the safe and efficient firing of the MBA and the data acquisition and archiving of accelerator function.

Evaluation of a Back-Up Activation Mechanism to Achieve Fail-Safe Operation in Distributed Multiprocess Systems

The problem of activating a back-up process in a distributed system of loosely coupled asynchronous processes is considered. The main process and its back-up communicate by messages transmitted through a network introducing random delays and maintaing the order of the messages (virtual channel service). The back-up process realizes a watch-dog function in a stand-by state. A mechanism is proposed for its activation to full back-up taking into account the characteristics of the message communicating network. The evaluation of the activation mechanism foccusses the attention on the following criteria: A) Bounding the probability of unnecesary activations, B) Bounding the mean delay of full activation of the back-up process and C) Minimization of network traffic due to messages generated by the back-up mechanism. Concluding remarks related to the implementation of the mechanism in distributed data acquisition andcontrol system are given.

Life-testing of 1.7 kW h zinc—chloride battery system: Cycles 1 – 1000

A 1.7 kW h battery system was built and tested in 1976 as one part of a program to develop the zinc—chloride battery for utility load-leveling. The two volt, multiple-cell battery stack is of particular interest because it embodies many of the design concepts utilized in the present technology at Energy Development Associates (EDA) for both electric vehicle and load-leveling applications, e.g., porous graphite—chlorine electrodes. From early 1977 onwards, cycle-testing of the system was conducted with a data acquisition and control system (DACS). As of June 1979, the system accumulated 1000 charge—discharge cycles. As indicated by the constancy of the voltaic efficiency, the performance deterioration through 1000 cycles was negligible. EDA plans to continue testing through 2500 cycles — the life target for the commercial version of the load-leveling battery.