Microprocessor-based System Research Articles

A microprocessor-based piezoelectric quartz microbalance system for compound-specific detection

The authors describe the implementation of a portable, microprocessor-controlled, piezoelectric quartz microbalance (PQM) system suitable for remote and autonomous monitoring of air quality around hazardous waste sites or chemical spills. The system has been designed to detect nanogram-level mass change or sorbed compounds sensitive to the specific coating materials used. Miniaturized modular hybrid crystal clock oscillators were used to construct a four-sensor array. The quartz crystals of the four modules were exposed and coated with chemically specific compounds so that they would act as sorption detectors. These sensor elements were enclosed in a small flow-through gas chamber along with a fifth module which was left sealed and was used as a reference oscillator. The frequency of each sensor was separately mixed with that of the reference oscillator and multiplexed into the microprocessor. The difference frequencies were measured by the microprocessor through a programmable timer/counter chip. The temperature within the gas chamber was maintained constant by means of a PID (proportional-integral-derivative) controller implemented in software. A Peltier device was used as a heating/cooling element of the gas chamber. >

A microprocessor-based semiconductor solar radiometer

The photocurrent produced by a silicon PN junction is used as a solar radiation transducer. It has high and linear sensitivity in the main part of open sunlight spectrum. Using a commerical device as sensor, a low-cost solar radiometer can be constructed. The photocurrent produced is electronically tailored to store solar radiation data in a microprocessor-based data acquisition system. This portable instrument can be used in remote sites and substitutes solar monitor, integrator and data-logger equipment. The data can be transported by a RS-232 port or in a nonvolatile static RAM card, interfaceable with personal microcomputer.

Microprocessor-based voltage controller for wind-driven induction generators

A microprocessor-based closed-loop system has been developed for wind-driven self-excited induction generators using a controlled rectifier to maintain a constant DC load voltage with varying rotor speeds. The configuration and implementation of the control scheme are described. Test results on a self-excited induction generator demonstrate the satisfactory performance of both the hardware and the software of the control scheme, and the utility of the set-up as a whole. The steady-state analysis of the generator is extended to include the controlled rectifier, and the performance characteristics are predicted. >

Development of a microprocessor-based four probe DC resistivity setup for T/sub c/ measurement of superconducting materials

The design of a microprocessor-based resistivity measurement system for high transition temperature (T/sub c/) superconducting materials is described. This design includes interfacing an Intel 8085 microprocessor system with an IBM-compatible personal computer (PC) through RS-232C serial communication. This design is used to measure resistivity for superconducting samples of YBa/sub 2/Cu/sub 3/O/sub 7-x/ and strontium/potassium substituted YBa/sub 2/Cu/sub 3/O/sub 7-x/. A correction method is described for the parameters whose values are changing throughout the measurement period to minimize the measurement errors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An efficient algorithm for the control of a microprocessor-based single-phase to three-phase cycloconverter

An efficient algorithm is designed to calculate the intersection points of a cosine wave and a reference wave in a cycloconverter. The proposed algorithm requires a smaller number of comparisons to calculate the required intersections than the conventional linear search method; hence, processor time is reduced. The algorithm can be implemented on a microprocessor-based cycloconverter multiple feedback system. The reduced number of comparisons as compared with the linear search method make the algorithm useful for many applications in microprocessor-based control circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Engineering workstation as a training tool for process control design and implementation

This paper describes the total role of a PC-based Engineering Workstation (EWS) in designing and implementing the control functions. The plant is controlled, monitored, and managed by a microprocessor-based distributed control system that interfaces with EWS. The steps and procedures of the work for design using EWS are described. EWS is also used as a personal computer, and many off-line calculations are performed. The plant for the demonstrated case is a chiller system. The role of EWS as a significant training tool for control design and implementation, which received wide acceptance and has user appeal, has been demonstrated. The main advantages of EWS have been: (1) the ability to configure and edit all control system configurations before installation is complete, (2) to have on-site permanent drawings of control logics at any time, (3) to integrate various control symbols and load them onto control modules by operator-friendly software, and (4) to monitor the process operation for diagnosis and troubleshooting as a support to the user. In the body of the paper all hardware and software of the EWS are fully described along with the control logic diagrams in drawing format and CRT displays.

Microprocessor-based on-line monitoring and characterization of power factor of a synchronous motor

An attempt is made to develop a microprocessor-based system for online monitoring of the power factor of a synchronous motor. The method is based purely on software design with the use of two resistors (of small ohmic values and high current carrying capacity) connected in series with the field circuit and load circuit, which generate the reference signals for the microprocessor. However, for mechanical loading, the resistance in the load circuit may be replaced by a torque transducer. The interesting feature of the system is its capability to characterize the status (i.e. leading, lagging, or unity) of the power factor. The system is helpful in providing necessary information for power factor corrections leading to the best utilization of the synchronous motor. >

Digital parameter-adaptive control for a solar concentrator

The discrete-time control algorithm of a solar concentrator unit is presented. This system is required to supply thermal energy so that the outlet working fluid temperature could be kept constant. A simple linear finite-difference approximation of the process dynamics provides the basis for the controller design. No initial knowledge of the values of the approximate process model parameters is necessary as the on-line identification procedure is incorporated in the contrll algorithm. Control design and Recursive Estimation Methods has been combined toobtain Self-Tuning Regulators. The results of computer simulation indicate that a very satisfactory performance of the solar collector can be achieved using self-tuning regulators. Moreover the proposed regulators are suitable for microprocessor-based system implementation.

Elastic Feed Control Systems

The manufacture of certain garments, such as underwear, requires the attachment of tensioned elastics and tapes to workpieces. If the elastic is incorrectly tensioned, when it returns to its original length the garment will be too tight or too loose, and a sub-standard garment is produced. Two distinct processes are involved in the feed of elastic for such an operation. These are precise control of the elastic tension and of the rate of feed of the workpiece into the sewing machine. The former can be achived with a fully automated control system while the latter usually involves an operator, thus requiring a man/machine inteface.This paper describes the design and development of an adaptive microprocessor-based control system to implement the above operations. The system employs closed-loop control to maintain precise elastic tension. It also uses an adaptive control loop to compensate for practical problems such as manual workpiece feed rate, elastic feed path friction, and changes in the physical characteristics of the elastic. The system has been implemented with a 68000 single board computer for all control calculations, a stepper motor, a force transducer, and optical sensors. The performance simulation results are given and compared to those of conventional open-loop systems. Practical operational data is also presented.

Parallel linkage steering for an automated guided vehicle

The computer-aided design of suitable control strategies for parallel linkage steering of an experimental automated guided vehicle is described. The microprocessor-based steering control system is modeled, and stability characteristics using proportional control are investigated by means of describing functions. Although the approximation is coarse, the analysis indicates an upper bound for gain and suggests derivative action for improved control. For better accuracy, a flexible and fast simulation program that makes possible an efficient search for optimal control laws for operation of the vehicle under the constant speed mode and slow-down mode is developed. Time-independent control laws are investigated, and solutions are found that give tolerable tracking over 90 degrees arcs of 0.5 m radius. The simulation results show that time-dependent control laws are essential for improved, nonoscillatory tracking.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microprocessor-based 250-1100 nm photometer with flat spectral response

The digital photometer system developed earlier has been upgraded by incorporating a microprocessor-based system with it. The optical response of the system is uniform in the detection range of 250-1100 nm. The associated non-linearity of measurements of high irradiance has also been removed by suitable circuit modifications. The system is now capable of storing time profiles of photometric data and has enhanced user-friendly options.

A microcomputer-based agricultural digger control system

Considerable skill is required to operate an agricultural digger accurately and efficiently, and an analysis of the different procedures and operator skills is given. From this a specification of a microprocessor-based control system for a tractor-mounted digger is derived to give: linear bucket blade movement, accurate gauging of the pitch of sloping cuts, and a learn-and-repeat facility. A closed-loop control system is described using an 8085A microprocessor with an AM9511 arithmetic processor for real-time floating-point calculation. Precision potentiometers were used for position feedback and proportional solenoid valves for control of the hydraulics. A firmware option also allowed the system to be operated open loop to emulate a conventional digger. For novice users the cutting of straight profiles was facilitated but the time for digging operations showed no consistent improvements. This is probably because the decision-making process in lever selection is not eliminated and a telechiric system would be more effective. The open-loop system has the advantages, over conventional mechanical control, of ease of installation and reduced lever loads.

An Adaptive Sampling-Interval Generator for Digital Relaying

A method for measuring frequency at a fixed sampling rate is described, and a variable-rate method is introduced. An algorithm based on a digital Fourier transform, which locks the sampling frequency in a microprocessor-based system to the fundamental of an incoming voltage waveform, is devised. The algorithm also intrinsically provides a measurement of the frequency. The algorithm is applied to the case of a volt/hertz relay. >

An adaptive sampling-interval generator for digital relaying

A method for measuring frequency at a fixed sampling rate is described, and a variable-rate method is introduced. An algorithm based on a digital Fourier transform, which locks the sampling frequency in a microprocessor-based system to the fundamental of an incoming voltage waveform, is devised. The algorithm also intrinsically provides a measurement of the frequency. The algorithm is applied to the case of a volt/hertz relay.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Microprocessor-Based System for Monitoring Gas Turbines

The development and testing of hardware and software for a microprocessor-based monitoring system for gas turbines is described in this paper. The operators of gas turbines can be trained to monitor running hours, slip between high and low pressure compressor spools and torque on the reduction gear-box under various conditions ofoperation. The system will replace the traditional method of monitoring these parameters which are more time consuming and error prone.

Data acquisition and control system for experimental thin-layer drying study

A microprocessor-based system was constructed to control experimental conditions in the study of the moisture content of agricultural products. The equipment also recorded the condition of the air and the sample weights during the thin-layer drying tests for these products. This paper describes the hardware and software which were developed for use in the study of the properties of parboiled rice. Two samples were studied simultaneously at 13 combinations of relative humidity and temperature. The drying conditions were held constant enough that the variation in conditions in the drying chamber was shown to have no measurable effect on the thin-layer drying data, producing data repeatable to 0.001 moisture content dry basis.

Fabrication of Custom Designed Telephone Exchange Microchip

This chip was design basically to replace 28 standard integrated circuits on the subscriber module of a 8088 A microprocessor-based PAX system. The circuit was fabricated using silicon gate NMOS process developed at CEERI. The threshold voltages were controlled by ion-implantations and tested on the test structures on wafer after fabrication. The minimum feature size is 6 micron and the chip containing about 500 components is of 3.35 × 3.35 mm size. The circuit chip was bonded and encapsulated in 44 lead ceramic chip carrier. The packaged chips passing all the set specifications were put in the system and found to work satisfactorily.

Verification Method of Software for Microprocessor-Based Protection System of Nuclear Power Plants

This paper proposes a new concept for efficient verification of software for the protection systems of nuclear power plants. In this idea, all possible input combinations are applied to each module comprising the software and the module responses are compared with their correct responses which are provided beforehand. To realize the concept, algorithms have been developed for observing module responses through an external tester and for generating a quasi minimal test pattern set capable of testing all modules. This approach remarkably reduces the number of required test input combinations in comparison with that of the combinations without observation of module outputs. In addition, most software errors are expected to be uncovered more efficiently with less effort and time.

Automated analysis of prerecorded evoked electromyographic activity from rat muscle

An automated microprocessor-based data acquisition and analysis system has been developed specifically to quantify electromyographic (EMG) activity induced by the convulsant agent catechol in the anaesthetized rat. The stimulus and EMG response are recorded on magnetic tape. On playback, the stimulus triggers a digital oscilloscope and, via interface circuitry, a BBC B microcomputer. The myoelectric activity is digitized by the oscilloscope before being transferred under computer control via a RS232 link to the microcomputer. This system overcomes the problems of dealing with signals of variable latency and allows quantification of latency, amplitude, area and frequency of occurrence of specific components within the signal. The captured data can be used to generate either signal or superimposed high resolution graphic reproductions of the original waveforms. Although this system has been designed for a specific application, it could easily be modified to allow analysis of any complex waveform.

Microprocessor-based system for colour TV testing during manufacture

The design, implementation, and evaluation of a prototype test set-up for colour TV sets is presented. The system is microprocessor based, and trial runs were successfully performed on the production lines of a company in the electronics industry. Both hardware and software aspects are outlined.