Showing papers on "Temperature control published in 1993"

Portable temperature control system

Abstract: A light-weight portable temperature control system which includes form fitting disposable therapy pads for selected body parts having serpentine fluid channels therethrough, a programmable microprocessor for controlling the temperature type and length of cycle, quick disconnects for the therapy pad, a thermoelectric cooler with a liquid heat exchanger and a pump for circulating the fluid through the system.

Monitoring and diagnosing process control performance: the single-loop case

Abstract: We present a hierarchical method for monitoring and diagnosing the performance of single-loop control systems based primarily on typical operating plant data. It identifies significant deviations from control objectives, determines the best achievable performance with the current control structure, and identifies steps to improve the current performance. Within the last point, the method can isolate whether poor performance is due to the feedforward loop or the feedback loop. If in the feedback loop, it is sometimes possible to determine whether the cause of poor performance is plant/model mismatch or poor tuning. The methods are based on simple but rigorous statistical analysis of plant time series data using autocorrelation and cross correlation functions. The theoretical basis of the method is developed, and it is applied to simulation studies which clarify the principles. Then, results of studies on two industrial processes are reported. The first is a heat exchanger feedback temperature controller, and the second is a feedforward-feedback tray temperature controller in a 50-tray distillation column. The initial diagnosis and subsequent control performance improvements are reported for both cases

Residential heating and air conditioning control system

Abstract: A temperature control system for a residential zoned forced air system which maintains programmed temperature setpoints for specific periods in each zone having hold, override, and vacation modes which can temporarily alter the programmed temperature setpoints and time periods for either individual zones or all zones until the next programmed time or the temporary modes are released.

Thermostat with selectable temperature sensor inputs

Abstract: A thermostat has terminals to receive at least two temperature sensor signals, and changes the one of these terminals which provides the feedback signal for temperature control responsive to a detected condition. This condition may be a manual input, expiry of a time interval, reaching a time of day, or the relative magnitudes of the temperatures encoded in the sensor signals.

Method and apparatus for hydrophobic treatment

Abstract: Adhesion apparatus for applying a hydrophobic treatment to a semiconductor wafer comprises a tank housing a treating agent of liquid HMDS and a process chamber into which a mixed gas consisting of a vaporized HMDS coming from the tank and a carrier gas is supplied for applying a hydrophobic treatment to a wafer surface. A supporting table on which the wafer is disposed during the hydrophobic treatment is provided within the process chamber. A heater and a cooling water passageway are housed in the supporting table for controlling the wafer temperature. A concentration measuring section for measuring the HMDS concentration in the waste gas is connected to the discharge pipe of the process chamber. The concentration measuring section is connected to a CPU serving to derive a temperature control signal from the measured value of the HMDS concentration. The temperature control signal is transmitted to a temperature control section. Upon receipt of the temperature control signal, the temperature control section permits controlling the current supply to the heater or the cooling water supply to the cooling water passageway so as to change the temperature of the supporting table.

Temperature control system and controller therefor

Abstract: A temperature control system for a building structure such as a household is divided into a plurality of zones. A controller acts between temperature sensing devices in each of the zones and an adjustable thermostat which allows the desired temperature in the building structure to be selected. The controller allows individual zones to be selected to receive conditioned air and allows one of the selected zones to be designated as a control zone. A heating or cooling decision for the temperature control system for all of the selected zones is made based on the difference between the thermostat setting and the output of the temperature sensing device in the control zone. The control zone can be changed manually to the next available selected zone. Different visual indications are given for the control zone and the selected zones. Zones with faulty temperature sensing devices cannot be control zones or selected zones.

Environmental control system using poled diodes to allow additional controlled devices in existing four wire system

Abstract: An environmental control system for controlling heating, ventilation, humidification and air conditioning equipment located in plant area of a house includes a kit consisting of a remote control unit located in a living space of a house that is linked by a four wire link to a main control unit located in or adjacent the plant area. The remote control unit has a temperature control device, a humidity control device, and a fan control device. Additionally, the remote control unit may include indicating devices and/or an internal battery charger for a rechargeable battery that may be used to operate electronic circuits and controls in the remote unit. AC power from an AC transformer in the plant area is supplied to each of the control devices via the four wire link. The main control unit has relay coils coupled to the four wires in the wire link via selectively poled diodes. The selective energizing of these relay coils results in the opening and closing of relay contacts in the main control unit through which AC power is supplied to the heating, ventilation, humidification and air conditioning equipment located in the plant area to thereby control the operation of that equipment.

Fluid flow and temperature control apparatus

Abstract: Apparatus is provided to supply a liquid, for example water, at a constant temperature, for example to a shower by mixing two supplies of the liquid, one hot and the other cold. Control of the output temperature is effected by measuring and controlling the flow rate in one or both of the supplies by way of flow meters having a rapid response time and motor driven valves. In the case where the flow rates in both supplies are measured and controlled it is possible further to control the output flow rate in addition to and independently from the output temperature, also by controlling the flow rates in the supplies. Further accuracy may be achieved by sensing the input supply temperatures in addition to the flow rates.

Optimal design and operation of batch reactors. 2. A case study

Abstract: The optimal design and operation methodology developed in part 1 will be illustrated in a batch polymerization reactor system (polymerization of methyl methacrylate (MMA) initiated by azobis(isobutyronitrile) (AIBN) in toluene). Following the steps of the methodology, first a mathematical model of the process (which accounts for gel effect and volume shrinkage) is developed and then the performance indices and mode of operation are selected. The optimal loading conditions and reactor temperature profile (which minimize the polydispersity of the final polymer product and minimize the monomer conversion constrained to a desired value of the weight-average molecular weight at the end of the batch time) are computed numerically. After designing the heating/cooling equipment, its flexibility, controllability,and safety, as well as the feasibility of the computed optimal operating conditions, are investigated. A nonlinear temperature controller is finally synthesized to enforce the reactor startup conditions and the optimal temperature profile

Wavelength stabilizing apparatus

Abstract: An injection current controller 113 is provided to supply a given injection current. A semiconductor laser (LD) 112 receives the injection current from the injection current controller to output a laser beam. An etalon 114 discriminates the wavelength of the laser beam output from the semiconductor laser. A photodetector (PD) 116 is provided to detect the intensity of the output beam from the etalon. An LD temperature controller 117 performs temperature control of LD so as to bring the output of PD to a predetermined value and, when the output of PD becomes the predetermined value, reserves a corresponding temperature of LD and, at the next temperature control start time, initiates temperature control based on a finally reserved temperature of LD.

Variable speed HVAC without controller and responsive to a conventional thermostat

Abstract: A system for conditioning air in a space by heating or cooling the air to change its temperature. A thermostat located within the space generates a two state temperature signal having a cyclic parameter which corresponds to the temperature of the air in the space as it rises and falls. A compressor supplies refrigerant to a heat exchanger by means of which changes are made in the temperature of the air. A variable speed motor drives the compressor in response to a motor control signal. A controller responds to the temperature signal and senses the cyclic parameter of the temperature signal. The controller generates the motor control signal as a function of the sensed cyclic parameter whereby the motor control signal is provided to the motor to control the torque or speed of the motor.

Dual temperature control of refrigerator-freezer

Abstract: A dual compartment single evaporator refrigerator and temperature control apparatus that effectively controls two compartment temperatures by making the evaporator fan control independent of the compressor cycle. The compressor cycle is initiated by the fresh food compartment temperature, runs for a predetermined minimum time, and is terminated by the freezer temperature. The evaporator fan runs with the compressor and is terminated by the freezer control temperature. A small portion of the evaporator air circulation flows through the fresh food compartment and compartment temperatures are balanced according to the freezer temperature settings during the post-compressor cycle fan control. The temperature control set points to operate the compressor and fan are based on algorithms that compensate the control for the combination of freezer and fresh food temperature settings.

Control circuit for regulating temperature in an ink-jet print head

Abstract: A temperature control circuit regulates temperature in an ink-jet print head. The control circuit includes a thermal sensor mounted on the print head to measure its temperature and a temperature level detector to determine whether the measured print head temperature exceeds a threshold temperature. The temperature level detector outputs a first signal when the measured print head temperature exceeds the threshold temperature and a second signal when the measured print head temperature does not exceed the threshold temperature. The control circuit also has first logic circuitry to output warming pulses upon receipt of the second signal. The warming pulses have energy insufficient to deposit an ink drop from the print head. Second logic circuitry is configured to output warming pulses to non-selected nozzles of the print head and firing pulses to selected nozzles. In this manner, the print head is automatically warmed via the warming pulses so long as the print head temperature is below a prescribed level. An ink-jet print head incorporating the control circuit is also disclosed.

Temperature share scheme

Abstract: An improved temperature control system for a power conversion circuit having two or more power converters operating in parallel and providing output power to a single load. The temperature control system maintains the temperature of each of these power converters at approximately the average temperature of the power converters. A detector coupled to each power converter detects the temperature of the power converter and generates a measurement signal that is a function thereof. A reference signal is generated that is a function of each measurement signal. A control circuit responsive to the measurement signal of each power converter adjusts the output power of that respective converter as a function of the difference between that converter's measurement signal and the reference signal such that the temperature of each power converter approximates the average of temperature of the power converters.

The controlled cooling of hot rolled strip: a combination of physical modeling, control problems and practical adaption

Abstract: The control of the temperature and the cooling patterns of a hot strip mill, in which hot rolled steel is cooled with water directly after the finishing mill and before the material is coiled, is discussed. The control of the temperature and the cooling patterns are important because of the physical transitions in the steel. For this control, linearized models are used in an online computer. These models are deduced from theoretical models and adapted to practice. The parameter estimation for some of these models is done offline, other parameters can be estimated online. Since it is possible to deduce several different physical models for the waterjet cooling it is not feasible to design an accurate online water cooling model. Therefore, a combination of models was designed and run parallel to the process. Using statistical analysis the best fitting form is chosen. >

A Microwave Oven with Variable Continuous Power and a Feedback Temperature Controller

Abstract: The unique property of microwaves to penetrate and produce heat deep within food materials providing sig nificant reductions in process time makes this form of heat transfer very attractive to consumers, researchers, and the food industry. In the food industry, processes that are generally considered suitable for microwave applications include dehydration, freeze-drying, blanching, baking, thawing, pasteurization, sterilization, and curing. A review of work both completed and in progress in these areas was given by Decareau (1985). Unlike convection heating, where the solid temperature can never exceed that of the external air stream, there is no such limiting temperature in microwave heating except in the ideal situation where only the free water absorbs electric energy, in which case the maximum temperature is the boiling point of the liquid. In practice, when the moisture content is high, it often appears that there is sufficient moisture present to act as a sink for the energy absorbed by the solid. At lower moisture contents, the sink becomes increasingly ineffective and the temperature rises again, even though the loss factor

System and method for determining ambient temperature outside of a vehicle

Abstract: A microprocessor based temperature determination system for displaying outside ambient temperature inside of an automotive vehicle. The system utilizes sensors for vehicle speed, engine temperature and exterior temperature measurements in order to accurately determine a true temperature indication, taking into account non-ambient heat sources. The temperature displayed to the vehicle's occupants is either the current reading from the exterior temperature sensor, or is an averaged temperature value. The averaged temperature value is determined by averaging the value of the temperature sensor's readings over a ten second interval, taking a sample every one half second.

Apparatus and method for controlling temperature of a turf field

Abstract: A subsurface hydronic heat-exchanging apparatus and method are provided for controlling the temperature of a turf field. A temperature-controlling fluid is circulated from a temperature-controlled fluid source through a supply header laterally disposed to the field and coupled to an array of hollow tubular heat-exchanging elements underlying the field. Fluid is recirculated to the fluid source from the tubes through a return header laterally disposed to the field and coupled to the tubes. Temperature sensors are disposed adjacent the turf field which detect the temperature of the field and a temperature control device is provided which is responsive to the detected temperature.

Design of decentralized robust controllers for multizone space heating systems

Abstract: Temperature control of multizone environmental spaces is studied. A bilinear model of a multizone space heating (MZSH) system is developed. The MZSH system is acted upon by constant unknown disturbances and step changes in the desired set-points. Robust decentralized controllers are designed with linear and nonlinear models, using two different methods based on optimization of quadratic performance criteria. In each case, the output responses of the resulting closed-loop bilinear system are examined. Simulation results showing the regulation properties of the decentralized and centralized controllers are presented. The results show that the system performance with decentralized control is very close to the performance of the system with centralized control. A decentralized controller is also designed for the bilinear model based on minimizing not only the output error and energy input, but also a measure of sensitivity to parameter variations. Simulation results for the corresponding bilinear closed-loop system are presented. >

Temperature control during laser vessel welding

Abstract: A technique is described for the computer control of temperature during laser vessel welding. The technique is based on the use of thermal feedback from a calibrated IR sensor. The utilization of thermal feedback makes it possible for welding to be performed at a quasiconstant temperature. An experimental system based on this concept has been developed and evaluated in mock anastomoses with vascular tissue. A computer simulation of laser vessel welding with a one-dimensional heat conduction model has been performed. Model parameters have been adjusted so that the relative effect of laser penetration depth and tissue dehydration as well as the role of thermal feedback in limiting the peak surface temperature can be studied. The results of the mock anastomoses are discussed in light of the computer model.

Thermostat-type setback controller having a recovery set point which depends on the time-based value of a sensor signal

Abstract: A setback controller, typically a thermostat, controls a control unit which holds a condition within an enclosure at either a low energy consumption set point or a high energy consumption set point depending on the present time. The controller uses a recovery sensor to measure the state of a condition which can affect the rate at which recovery from the low energy to the high energy set point is likely to occur, and then starts recovery at a time consistent with the state of the condition so as to complete recovery at or near the time selected for the return to the high energy set point. The condition sensor may be located adjacent to the outside of the enclosure to sense one or more conditions. In a temperature control application, the recovery sensor may include a temperature sensor located outdoors near the controlled space and a wind velocity sensor.

Method and apparatus for monitoring temperature of blast furnace and temperature control system using temperature monitoring apparatus

Abstract: An optical fiber is laid in a spiral shape on a surface of an iron skin of a hot-air oven constituting a blast furnace facility, and one end of the optical fiber is connected to a temperature measuring apparatus. A temperature distribution of an optical fiber laid area is measured based on the intensity of Raman back scattering light of a light pulse transmitted into the optical fiber and based on a time interval until the Raman back scattering light returns to the transmission end of the optical fiber. The temperature distribution is displayed on a display screen to monitor the temperature distribution of the whole area of the iron skin of the hot-air oven to detect an abnormal condition thereof.

Substrate temperature control apparatus and technique for CVD reactors

Abstract: One of the critical experimental parameters affecting the quality and gro rate of chemical vapor deposition species, such as, diamond is the substrate temperature. An apparatus and technique for the precise control of the substrate temperature in a chemical vapor deposition environment has been developed. In a preferred embodiment, the technique uses a variable gas mixture in conjunction with the disclosed apparatus of the present invention to precisely control the temperature of the substrate to within at least ±20° C. for extended periods of time and over large area substrates on the order of 1" in diameter or larger.

Method of improving temperature uniformity of a space conditioned by a refrigeration unit

Abstract: A method of operating a refrigeration unit to improve the uniformity of temperature distribution in a conditioned space, with the refrigeration unit including a refrigerant compressor and an evaporator fan driven at a selectable one of high and low operating speeds by a prime mover arrangement. The method includes the step of periodically operating the compressor and evaporator fan at the higher of the two operating speeds, notwithstanding a set point temperature control algorithm calling for operation of the compressor at the lower of the two speeds. When the refrigeration unit is operating in a continuous mode, the value of a constant entered into an operating program by the user determines the minimum number of minutes of each hour the prime mover should be forced to operate in the higher speed mode. When the refrigeration unit is operating in a cycling start-stop mode, the value of the constant entered into the operating program by the user determines which operating cycles are to be performed with the prime mover in the high speed mode, notwithstanding a set point temperature control algorithm calling for the low speed mode.

Two terminal temperature transducer having circuitry which controls the entire operating current to be linearly proportional with temperature

Abstract: A two terminal temperature transducer which controls its operating current to indicate the temperature, by producing a linear response to temperature which can be set to extrapolate to a desired temperature. The transducer including circuitry which controls its operating current to be linearly proportional with temperature. The circuitry operates to produce a first reference voltage which is proportional to absolute temperature, produce a second reference voltage which is complementary to absolute temperature, generate a voltage drop corresponding to the operating current, compare the voltage drop to a temperature sensitive voltage corresponding to the difference between the first reference voltage and the second reference voltage, and adjust the operating current so as to equilibrate the voltage drop and the temperature sensitive voltage. According to one embodiment, the transducer includes an amplifier with a proportional to absolute temperature input offset voltage to drive a temperature proportional current through a series resistor, and includes circuitry to offset one input of the amplifier so as to cause the extrapolated slope of the temperature proportional current to pass through zero at a selected temperature.