Showing papers on "Temperature control published in 1989"

Toward intelligent control

Abstract: The problem of automatic tuning of simple regulators is examined. The key idea is to design an aid for the process operator, which should use minimal prior information about the system. This is a typical example of a case where it is essential to develop techniques that will give crude but robust estimates. The development has resulted in a novel generation of the classical PID (proportional, integral, and derivative) controller. An application of relay autotuning to temperature control of a distillation column is considered as an example. Adaptive control is then treated. The adaptive algorithms can be viewed as local gradient methods. They require prior information but, given the information, can give very good control performance. The use of an expert system to integrate the two approaches is then discussed. >

Physical modeling of the composting ecosystem.

Abstract: A composting physical model with an experimental chamber with a working volume of 14 × 103 cm3 (0.5 ft3) was designed to avoid exaggerated conductive heat loss resulting from, relative to field-scale piles, a disproportionately large outer surface-area-to-volume ratio. In the physical model, conductive flux (rate of heat flow through chamber surfaces) was made constant and slight through a combination of insulation and temperature control of the surrounding air. This control was based on the instantaneous conductive flux, as calculated from temperature differentials via a conductive heat flow model. An experiment was performed over a 10-day period in which control of the composting process was based on ventilative heat removal in reference to a microbially favorable temperature ceiling (temperature feedback). By using the conduction control system (surrounding air temperature controlled), 2.4% of the total heat evolved from the chamber was through conduction, whereas the remainder was through the ventilative mechanisms of the latent heat of vaporization and the sensible temperature increase of air. By comparison, with insulation alone (the conduction control system was not used) conduction accounted for 33.5% of the total heat evolved. This difference in conduction resulted in substantial behavioral differences with respect to the temperature of the composting matrix and the amount of water removed. By emphasizing the slight conduction system (2.4% of total heat flow) as being a better representative of field conditions, a comparison was made between composting system behavior in the laboratory physical model and field-scale piles described in earlier reports. Numerous behavioral patterns were qualitatively similar in the laboratory and field (e.g., temperature gradient, O2 content, and water removal). It was concluded that field-scale composting system behavior can be simulated reasonably faithfully in the physical model.

Bulk optic wavelength division multiplexer

Abstract: An optical multiplexing/demultiplexing device (10) combines an etalon (12) and weak diffraction grating (18) along with temperature control to finely tune local resonant stations along the etalon to separate and/or combine a plurality of optical signals that are finely spaced in wavelength.

Controlled ink drop spreading in hot melt ink jet printing

Abstract: In the particular embodiments described in the specification, a hot melt ink jet system includes a temperature-controlled platen (16) provided with a heater (25) and with a thermoelectric cooler (28) electrically connected to a heat pump (26), and a temperature control unit (22) for controlling the operation of the heater (25) and the heat pump (26) to maintain a substrate (10) on the platen (16) which receives the ink (15) at a temperature which provides a desired spot size without causing print-through. In certain embodiments, the substrate temperature is from about 20°C above to about 20°C below the melting point of the ink and is determined by subtracting half the difference between the jetting temperature and the temperature at which the ink has a viscosity of about 200-300 cp from the latter temperature.

Motor driver circuit for resonant linear cooler

Abstract: A direct current powered, linear resonant cryocooler having a compressor in which the piston is reciprocated by a linear motor at substantially resonant frequency and the length of stroke of the piston is varied as a direct function of cryocooler temperature. There are two control loops, a temperature control loop and a voltage control loop which is independent of the temperature control loop. In the temperature control loop, temperature is sensed at the cryocooler or expander and the temperature signal is compared with a reference temperature signal to produce a temperature error signal or voltage. The voltage control loop controls motor voltage. As input to the voltage control loop, the linear motor voltage is fed back and compared with the temperature error voltage V TE to produce a voltage level signal V L in the input of the voltage control loop, representative of the correction required to obtain and then to maintain the cryocooler temperature represented by the reference temperature voltage. Either a pulse width modulated, variable amplitude sine wave signal or a constant duty cycle, pulse width modulated, square wave signal powers the linear motor.

LSI temperature control system

Abstract: An LSI temperature controlling system has closed LSI cooling water circuit, and a refrigeration circuit including a motor-driven refrigerant compressor, a first heat exchanger for exchanging the heat of the LSI cooling water and the refrigerant and a second heat exchanger for exchanging the heats of the refrigerant and another fluid. The motor speed is controlled by an inverter the operation of which is controlled based on the temperature of the LSI cooling water measured by a temperature detector. A heater is used to suppress dew formation on LSI substrates.

Fluid temperature monitoring system

Abstract: A fluid temperature monitoring system is characterized by an adjustable variable voltage divider for selecting a desired temperature range, a temperature detector for detecting whether the fluid temperature is above, below, or at the desired range, and a temperature indicator for emitting three different temperature indicating signals in accordance with temperatures above, below, or at the desired temperature range.

Nonlinear Predictive Control of a Semi Batch Polymerization Reactor by an Extended DMC

Abstract: In this paper a new nonlinear model predictive control law is applied to a semi-batch polymerization reactor. The particular model used in this study is the free radical polymerization of polymethylmethacrylate. The principal nonlinearities are due to the reaction rates and the gel effect. Two cases are considered: jacket temperature controlling the reaction temperature, and a MIMO structure where both the reaction temperature and the molecular weight are controlled by the jacket temperature and the initiator feed. The proposed control algorithm uses an explicit nonlinear process model and some of the elements of the classical DMC to solve the nonlinear input-output operator equation without computing the derivatives of the states and output equations. Constraints are not included in the present method.

Humidity control system

Abstract: A system for HVAC and humidification includes a control signal source which supplies two distinct control signals over two wires of a four wire link The control signals are supplied to a temperature control signal source and for a fan/humidity control signal source The temperature control signal source generates a temperature control signal and transmits the temperature control signal to a temperature signal decoder by means of a third wire of the four wire link The temperature signal decoder decodes the temperature control signal and turns on either a furnace or an air-conditioner The furnace and the air-conditioner each have a connection to a fan so that the furnace and the air-conditioner can each signal the fan to blow the heated or cooled air into the living area The fan/humidity control source operates independently of the temperature control signal source and generates a fan/humidity control signal for transmission over a fourth wire of the four wire link The fan/humidity control signal is received over the fourth wire of the four wire link by a fan/humidity signal decoder The signal decoder decodes the fan/humidity control signal and turns on either the fan or a humidifier The humidifier has a connection to the fan enabling the humidifier to control the fan and blow humidified air into the living area

Remote controlled high force actuator

Abstract: A piston (14) is slidably received in a chamber (10). The chamber is filled with an expandable medium (16), such as wax, that expands and contracts significantly as it undergoes a phase change from a solid to a liquid state. A Peltier effect chip (20) selectively adds and removes heat energy from the chamber, hence the medium, to cause the medium to change phase. A temperature control (26) maintains the temperature of the medium substantially at the phase change temperature such that the addition of heat causes an isothermal melting (hence, expansion) and the removal of heat causes an isothermal solidification (hence, contraction). The chamber defines a plurality of thin branches (42) such that the heat is transferred more effectively.

Environmental response control apparatus and method

Abstract: A control apparatus for controlling the temperature of an environmental chamber within which a device is tested for thermal characteristics employs a pair of control elements connected in cascade. The first element produces a required air temperature in response to a desired temperature and to the temperature of the device; the second produces a temperature set point in response to the required and actual air temperatures. Possible stress on the device is avoided by limiting the range of required air temperature. Response is accelerated by a pass-through circuit, parallel to the first element, which responds to a change in the desired temperature by adding to the required air temperature of value proportional to the change.

Analysis system having a removable reaction cartridge and temperature control

Abstract: An analysis system for analyzing a biological fluid or the like for a constituent of the interest includes metal body structure with sample flow path channel structure that serially interconnects heater chamber structure, recess structure for receiving a reaction chamber cartridge and an analysis region to which a measuring system is coupled. The reaction chamber cartridge preferably includes reaction chamber structure with an immobilized enzyme in the reaction chamber that is capable of converting the constituent of interest to a constituent detectable by the measuring system. Cooperating with the metal body structure is a transparent face plate structure which permits visual observation of the sample flow path in the metal body structure. Thermally coupled to the metal body immediately adjacent the analysis region are a temperature sensor that provides a temperature signal to a control unit and a thermal source that receives control signals from the control unit as a function of signals from the temperature system for stabilizing the temperature of the metal body structure (including the reaction chamber structure, the heater chamber and the analysis region) at a desired analysis temperature.

Apparatus for controlling temperature of machine tool

Abstract: A temperature control apparatus for a machine tool includes four temperature sensors for detecting a reference temperature, outlet temperature of heat transfer fluid at an outlet of a heat exchanger, and temperatures of the heat transfer fluid at both inlet and an outlet of a machine tool element having a heat generating source. The four temperature sensors are arranged to constitute a differential temperature detecting means that activates control means to control temperature of the heat transfer fluid from the heat exchanger so as to minimize both deviations of heat transfer fluid temperature and steady-state deviations of machine tool body temperature.

Compact separation system with snap-in columns

Abstract: The present invention is projected for use in chemical analyses based on separation techniques such as used in gas chromatography. The invention has a separating column encapsulated in a closed container of small volume, through which a temperature control fluid is circulated by means of a small pump, when the capsule is coupled to the instrument. This fluid is heated with temperature control and monitoring carried out electronically. The instrument also has a sample injector, a detector to indicate the separated components of the sample after their passage through the column and an electronic system to amplify and store the signal originated in the detector. An external control panel permits command of all its functions by an operator.

Heat seal temperature control

Abstract: Method and circuitry is disclosed for controlling and stabilizing temperature of a resistance heat sealing element used in packaging operations. Temperature of the heat sealing element is measured by monitoring its resistance by means of a current sensing resistor placed in series with the heat sealing element. The resistivity of the heat sealing element is a function of temperature and current measurement, assuming substantially constant applied voltage, is an accurate measure of sealing element temperature. The circuitry reduces application of electric power to the sealing element in response to current in the sealing element dropping below a predetermined level. The circuit either continues application of electric power, or increases it, in response to the current being above the predetermined level. Circuitry is also provided for compensating for undesirable line voltage changes to maintain the heating element at a constant temperature. Means is provided for adjusting the predetermined temperature at which power cut off occurs. The circuit and sealing element can be operated in either a continuous manner of in a "one-shot" fashion which has been determined as particularly useful for making seals which bear embossed indicia.

Adaptive optimal control of steam temperatures for thermal power plants

Abstract: This paper describes a new adaptive optimal control method for boiler steam temperature control of thermal power plants. Fig. 1 shows a schematic diagram of the adaptive optimal control system. A coal-fired power plant and the automatic plant control (APC) system are assumed to be a single controlled object in order to allow the APC to continue controlling the power plant, even if the adaptive optimal control system fails. A process dynamics model, composed of the above mentioned controlled object and a disturbance source, is proposed. The process dynamics model is represented by a multi-input and output autoregressive moving average (ARMA) model to predict future trends in process behavior. The disturbance source is the central load dispatching office. Parameters of the process dynamics model are identified during high and low load level power plant operation on a real-time basis when load fluctuations are relatively small. Optimal controller gains are calculated using the identified model by the dynamic programming (DP) method and adapted on-line when process characteristics change as a result of changing fuel heating value or during the course of long-term operation. These control gains suppress fluctuations in both main and reheater steam temperatures.

Air conditioner for vehicle

Abstract: PURPOSE:To make continuous, smooth temperature control performable by estimating each manipulated variable of an air-conditioning device and a cooling device from temperature inside and outside the vehicle through a fuzzy inference, and making these air-conditioning and cooling devices so as to be controlled by this manipulated variable. CONSTITUTION:Each detected signal is inputted into a controlling device 1 from a solar radiation sensor 5, a cooling water temperature sensor 4, an outside temperature sensor 3, an inside temperature sensor 2, a humidity sensor 22, a smoke detecting sensor 23 and a throttle opening sensor 21. The controlling device 1 estimates each manipulated variable of both air-conditioning and cooling devices in a way of a fuzzy inference with information to be inputted by a prearranged control law. With the inferred manipulated variable, an air-mix door 12, a blower motor 8 and a compressor 19 are controlled. With this constitution, the temperature control can continuously and smoothly be carried out.

Semiconductor wafer heating device

Abstract: A semiconductor wafer heating device includes a hollow heating stage. A semiconductor wafer is disposed over one surface of the heating stage and a heater is provided over the other surface thereof. A fluid having an excellent heat conductivity which is filled in the hollow space of the heating stage is stirred uniformly. In consequence, the surface temperature of the heating stage can be made uniform without employing a thick heating stage, and an excellent temperature control of the heating stage can be ensured.

Adaptive process control system, especially for control of temperature of flowing fluids

Abstract: A control system (method and apparatus) is adaptive on-line with changing process conditions, for example, the specific heat of a liquid used in a process. The system regulates a variable of a process (temperature of the liquid used in the process) and has a fast dynamic response to handle temperature transients while adapting to changing process conditions. The system uses feedforward and feedback control loops, which in the case of the process involving the temperature control of a liquid are respectively responsive to the temperature of the liquid before and after a control point. The system exercises adaptive control of the feedforward control function from the feedback loop. The system is preferably implemented with a digital computer. The fast dynamic response is enhanced by applying microwave energy from a microwave generator to heat the liquid at the control point with the feedforward and feedback control loops controlling the microwave generator.

Method and apparatus for controlling the temperature of a reforming reaction catalyst

Abstract: A method and an apparatus for controlling the temperature of a reforming reaction catalyst in which a reforming gas to be supplied to a fuel cell is produced by allowing it to react against a catalyst so that the fuel cell can provide output power to be supplied to a load. The present temperature for the reforming reaction catalyst may be modified in response to any variations in the load condition so that the amount of the combustion air output from the reforming burner can be reduced. The temperature control sequence for the reforming reaction catalyst may be performed near to the equilibrium point of the endothermic reaction following the catalytic reaction, thereby minimizing any variation that may occur in the catalyst temperature, and protecting the catalyst against its degradation. The temperature control sequence may be triggered at the time when the catalyst temperature has reached within the temperature setting range, thereby ensuring that the temperature control sequence can proceed stably and reliably.

Method and apparatus for controlling a-c power by means of thyristors for a resistance-type electric furnace

Abstract: A method of controlling a-c power by means of thyristors for resistive electric furnace for achieving a temperature control thereof, comprises providing an output which varies between O and N cycles in response to an input analog signal which also varies between 0 and 100% by a burn-on and -off control at zero crossings of an a-c power source. According to the invention, the output is uniformly distributed throughout a control period comprising N cycle times. The output pattern is transit to another output pattern in response to a new analog input signal at the desired point in time.

Room monitoring and control system

Abstract: A room monitoring and control system for use in multi-room buildings, such as hotels, institutions, apartments, and also, for example, in passenger ships, has a room information processing unit (22) for each room, a temperature sensor (28) connected to the unit for sensing the temperature in the room, a temperature control means (32) for controlling the temperature in the room and connected to the unit, a person presence sensor (26) in the room and connected to the unit so as automatically to cause the temperature control means to change the temperature to one predetermined value when a person enters the room and to change the temperature to a second predetermined value when a person is not in the room. A central processor is connected to a group of room units to receive information therefrom.

A system for supplying hot water

Abstract: A system supplies hot water by using an electrical current (30, 38) or energy source Temperature control is accomplished utilizing a digital processor (36) Energy is transferred to the water (32) in accordance with time-amplitude modulated cycles which permits the desired energy to be transferred with maximum power determined by an electric utility This permits flexible control of peak utility loads related to such systems

Heated roller temperature control system

Abstract: An automatic temperature control system for a heated roller constituting a fixing device. This control system has functions to sense the surface temperature of the heated roller, to compare with the sensed temperature and a target temperature suited for fixing toner image on a paper, and to determine a temperature gradient or a rate of temperature change with respect to time lapse of the heated roller, whereby a heater for heating the heated roller is turned on and off in accordance with the temperature state based on the comparison and the temperature gradient, that is whether the temperature of the heated roller is rising or falling. This temperature control for the heated roller is repeated on the basis of the surface temperature of the heated roller sampled by the system at fixed intervals.

Blowout temperature control system

Abstract: In a blowout temperature control system of an air conditioner for use in vehicles, a temperature detected by a ventilation duct sensor is weighted by a first weighting ratio which varies depending on a wind amount of a ventilation duct. A temperature detected by a defroster duct sensor is weighted by a second weighting ratio which is determined by the first weighting ratio. The weighted mean is calculated from the weighted detection temperatures of the ventilation duct and defroster duct, so that a substantial blowout temperature is determined. A deviation temperature between the substantial blowout temperature and an object blowout temperature is calculated and the blowout control is performed such that the deviation temperature becomes zero.

Application of H ∞ optimal design to automotive fuel control

Abstract: This study seeks to apply H∞ robust control theory to the design of an automotive diesel pump control system, and also to compare the results with those when optimal regulator theory is applied. A diesel pump control system must respond quickly and undeviatingly whenever a driver pedals the accelerator. Fuel viscosity changes due to temperature variations exert a great influence on the control system, both statically and dynamically. First, we constructed a feedback system by applying optimal regulator theory to the diesel pump control. However, the control has to be achieved by switching several feedback gains in relation to the fuel temperature variations. Thus, the aim of the present study was directed to design a robust control system that can withstand parameters perturbation. To do this, we used a type one robust feedback system constructed by application of H∞ robust control theory.

Temperature problems with rapid thermal processing for vlsi applications

Abstract: In this paper system-specific limitations of uniformity and the necessity for better temperature control for rapid thermal processing (RTP) for VLSI applications will be demonstrated. A sensitive technique feasible for temperature monitoring in production is presented which makes use of modulated optical reflectance measurements of highly implanted Si wafers after annealing. Problems with temperature calibration by thermocouples are reported which may influence, e.g., self-aligned silicide formation at ∼ 650°C. Dynamic effects leading to serious problems with temperature uniformity during short time cycles and their consequences on polysilicon emitter formation of bipolar transistors by RTP are discussed. A theoretical model is presented.