Showing papers on "Temperature control published in 1991"

Self-programmable temperature control system for a heating and cooling system

Abstract: The present invention provides for a self-programming temperature control system for automatically adjusting the temperature control setpoint of a heating and cooling system of a space in accordance with the present or anticipated occupancy status of the space The temperature control system comprises: a) detecting means for detecting the occupancy status of the space and providing an output of the occupancy status of the space; b) timing means for providing time intervals to the control system; c) storage means for storing the output of the detecting means in relation to the time interval provided by the timing means to provide a stored past occupancy record of the space; and d) programmed processor means including programmed instructions for reading and processing the past occupancy record of the space stored in the storage means to derive an anticipated occupancy status for the space and thereby control the temperature of the space in accordance with the programmed instructions and the stored past occupancy record of the space

Real-time multi-zone semiconductor wafer temperature and process uniformity control system

Abstract: A real-time multi-zone semiconductor wafer temperature and process uniformity control system for use in association with a semiconductor wafer fabrication reactor comprises a multi-zone illuminator (130), a multi-point temperature sensor (132), and process control circuitry (150). The method and system of the invention significantly improved wafer (60) temperature control and process uniformity. The multi-zone illuminator module (130) selectively and controllably heats segments of the semiconductor wafer (60). Multi-point temperature sensor (132) independently performs pyrometry-based temperature measurements of predetermined points of the semiconductor wafer (60). Process control circuitry (150) operates in association with the multi-zone illuminator (130) and the multi-point temperature sensor (132) for receiving the temperature measurements and selectively controlling the illuminator module to maintain uniformity in the temperature measurements. A scatter module (116) also provides input to process control circuitry (150) for real-time emissivity compensation of the pyrometry-based temperature measurements of semiconductor wafer (60).

Free-space, broadband measurements of high-temperature, complex dielectric properties at microwave frequencies

Abstract: A free-space microwave measurement system that is used for the high-temperature measurement of dielectric constants and loss tangents of homogeneous materials and that is applicable to composite materials as well is discussed. The system is capable of operating in the 5.85-40-GHz frequency range and ambient to 850 degrees C temperature range. A computer is used to control and coordinate furnace temperature, network analyzer functions, and data storage. Dielectric constants and loss tangents of the materials are calculated from the measured values of S/sub 21/. The measurement system, including the high-temperature furnace and the calibration technique, is described. Dielectric constants and loss tangents are presented for fused quartz and boron nitride grade HP in the frequency range 13.0-17.4 GHz and the temperature range from ambient to 850 degrees C. >

Conveyor oven control

Abstract: A control device for a multi-zone conveyor oven constructed according to the present invention comprises a microprocessor-based controller, appropriate control software, a keyboard and display for interaction with a user, means for sensing the conveyor speed and the heating chamber temperature, and means for controlling the power supplied to the conveyor motor and the heating elements The controller provides facilities for user programming of sets of oven parameters, each set corresponding to a particular food product to be cooked in the oven Each set of parameters includes the total cook time for the product and a desired temperature which is independently selectable for each heating zone Once a set of parameters has been programmed, it is assigned to a particular key on the keyboard, and the user may select that entire set of parameters by simply pushing the assigned key The parameters are stored in the EEPROM to prevent their loss during electrical power inteerruptions High-accuracy, low hysteresis temperature control of the oven is provided by pulse-width-modulating the power supplied to the heating elements Accurate and repeatable control of cooking time is provided by controlling the speed of the motor driving the product transport conveyor Such control is provided by pulse-width-modulating the powere supplied to the motor according to motor speed information derived by sensing the motor shaft position The controller also provides extensive fault detection, and degrades oven preformance as gracefully as possible

Active anticipatory control

Abstract: A space temperature control which prevents overshoot and undershoot of a desired space temperature by adjusting a subsequent sensed space temperature as a function of a previous sensed maximum space temperature to deenergize a space conditioning device at the adjusted temperature to maintain the desired space temperature.

A model for rapid thermal processing: achieving uniformity through lamp control

Abstract: A first-principles approach to the modeling of a rapid thermal processing (RTP) system to obtain temperature uniformity is described. RTP systems are single wafer and typically have a bank of heating lamps which can be individually controlled. Temperature uniformity across a wafer is difficult to obtain in RTP systems. A temperature gradient exists outward from the center of the wafer due to cooling for a uniform heat flux density on the surface of the wafer from the lamps. Experiments have shown that the nonuniform temperature of a wafer in an RTP system can be counteracted by adjusting the relative power of the individual lamps, which alters the heat flux density at the wafer. The model is composed of two components. The first predicts a wafer's temperature profile given the individual lamp powers. The second determines the relative lamp power necessary to achieve uniform temperature everywhere but at the outermost edge of the wafer (cooling at the edge is always present). The model has been verified experimentally by rapid thermal chemical vapor deposition of polycrystalline silicon with a prototype LEISK RTP system. The wafer temperature profile is inferred from the poly-Si thickness. Results showed a temperature uniformity of +or-1%, an average absolute temperature variation of 5.5 degrees C, and a worst-case absolute temperature variation of 6.5 degrees C for several wafers processed at different temperatures. >

Growth of Si1−xGex by rapid thermal chemical vapor deposition and application to heterojunction bipolar transistors

Abstract: Rapid thermal chemical vapor deposition has been applied towards the growth of Si and Si1−xGex structures on a 100 A scale. In this paper the relative merits of gas switching versus temperature switching for the growth of such structures are discussed. Active temperature control in the 600–700 °C range using infrared transmission for temperature measurement is demonstrated. The growth technique is applied to 45 A period superlattices with individual layer temperature control, and to heterojunction bipolar transistors with near‐ideal electrical characteristics.

Mixture thin film forming apparatus

Abstract: The present invention is directed to a mixture thin film forming apparatus for accumulating gasified components on a substrate which is arranged in a reaction chamber. According to the present invention, respective components of a gas supply system, which are different in heat capacity from each other, are independently controlled in their temperatures by temperature control parts respectively, so that the respective components can be adjusted to desired temperatures. Thus, the gas supply system is prevented from deviation of temperature distribution, whereby the overall gas supply system can be adjusted within a prescribed temperature range. Thus, raw materials are prevented from precipitation, irregular reaction or the like, to enable stable gas supply.

A laser heating system that stabilizes and controls the temperature : diamond anvil cell applications

Abstract: A laser heating system is described for use with diamond anvil high pressure cells that directly senses and stabilizes visible thermal radiation emitted by hot samples. This technique stabilizes sample temperatures better than other methods and allows superior temperature control. Calibration of the system was checked by measuring the melting temperatures of five metals at ambient pressure. Assuming literature values for spectral emissivity, the calibration was found to be accurate to 3.3% (based upon one standard deviation of the percentage error from published melting temperatures). Performance of the laser heating system was verified by heating iron foil at 13 GPa. With the sample intensity unstabilized, mean temperature was 3003 K with a standard deviation of 144 K, while with it stabilized, mean temperature was 3051 K with a standard deviation of 8 K. For a given wavelength‐dependent emissivity, the difference between the actual temperature and the greybody temperature increases as the temperature in...

Improvement of the response of an SMA actuator using a temperature sensor

Abstract: The ordinary control method, pulse width modulation (PWM) control method, for the shape memory alloy (SMA) actuator has a basic defect: the response of an SMA actuator controlled by this method is very slow, because the maxi mum voltage supplied to the SMA must be kept low in order to prevent the SMA from burning because its temperature is unknown. In this paper, a new control method is proposed to improve the response speed of the SMA actuator by limiting the temperature of the SMA to below the limited value in stead of by limiting the maximum voltage supplied to the SMA. Therefore this new control method allows us to use powerful drivers for supplying voltage to an SMA so as to in crease the heating speed of the SMA. First, a temperature sensor system to detect the SMA's temperature was developed by solving several problems. Next, experiments of the position control by a new SMA actuator system with a temperature threshold for SMA were carried out. Results show that the re sponse speeds are much faster ...

Thermostat with means for disabling pid control

Abstract: A thermostat is disclosed which includes a Proportional-Integral-Derivative (PID) controller and a means for disabling the PID controller for selected periods. The PID controller is disabled during a temperature recovery period, which can be triggered by the occurrence of one or more of many preselected events. The PID controller is re-enabled when the thermostat setpoint less a void offset temperature is reached. To reduce error in future temperature recovery periods, the void offset temperature is adjusted after a temperature recovery by adding the amount of error to the void offset temperature to create a new void offset temperature for use in a next temperature recovery period.

Active control of convection

Abstract: It is demonstrated theoretically that active (feedback) control can be used to alter the characteristics of thermal convection in a toroidal, vertical loop heated from below and cooled from above. As the temperature difference between the heated and cooled sections of the loop increases, the flow in the uncontrolled loop changes from no motion to steady, time‐independent motion to temporally oscillatory, chaotic motion. With the use of a feedback controller effecting small perturbations in the boundary conditions, one can maintain the no‐motion state at significantly higher temperature differences than the critical one corresponding to the onset of convection in the uncontrolled system. Alternatively, one can maintain steady, time‐independent flow under conditions in which the flow would otherwise be chaotic. That is, the controller can be used to suppress chaos. Likewise, it is possible to stabilize periodic nonstable orbits that exist in the chaotic regime of the uncontrolled system. Finally, the controller also can be used to induce chaos in otherwise laminar (fully predictable), nonchaotic flow.

Self-adjusting recovery algorithm for a microprocessor-controlled setback thermostat

Abstract: A recovery algorithm for a setback thermostat uses the intersection of the space temperature with a sloped recovery temperature line which approximates the change in temperature as a function of time during recovery of the temperature controlled space from a setback temperature, to determine the time at which recovery to the occupancy temperature should begin. The thermostat starts recovery when the current space temperature crosses the recovery temperature line. A useful feature of the apparatus and method which implement the invention, computes and constantly updates the slope of the recovery temperature line. The update of the recovery temperature line slope is based on miss time, i.e., the time between actually achieving the desired next set point temperature and the next set point time associated with the next set point temperature. If the heating or cooling load on the space changes, the recovery temperature will frequently cross the recovery temperature line at a different time, causing recovery to start at a time more compatible with the current heating or cooling load in order to complete recovery at or near the desired time.

Fryer temperature control system

Abstract: An oil fryer control system simultaneously controlling oil temperature and cooking time. A proportional, integral and derivative temperature control is used to maintain the oil temperature below and above a predetermined set point temperature. In addition, a cooking time control varies the cooking time within a predetermined range of temperature error as a function of a stored time-temperature relationship. The invention provides the capability of cooking different products having different cooking parameters in the same or different oil vats.

Control system for air-conductioner

Abstract: The control system for the air-conditioner disclosed herein comprises means for setting a set value of a room temperature, means for detecting an actual value of the room temperature, means for detecting a radiant heat from walls etc. of the room as a radiation temperature, and an operational control means. The operational control means stores a comfort line which defines an inverse proportional relation between the room temperature and the radiation temperature, said comfort line depending upon set value of the room temperature. The operational control means calculates a first control index which is represented by a difference between the actual value and the set value of the room temperature and a second control index which is represented by a difference between the comfort line and the current temperature condition represented by the actual room temperature and the radiation temperature. The room temperature set value is modified in the operatal control means, according to fuzzy rule, on the basis of said first and second control indexes. The operational control means controls the air-conditioner, depending upon a difference between the modified value of the room temperature and the actual value of the room temperature, thereby providing a comfortable air-conditioned environment to a person staying in the room.

Temperature control device for fluid filled pad

Abstract: A control circuit for a fluid-filled heating pad is described. The control circuit is unique in that it includes a thermistor that is located in close proximity to the heating pad. The circuit is also unique in that it includes a single high-precision reference resistor to self-calibrate the control circuitry.

Temperature control system for a heat detector on a heat exchanger

Abstract: A control system for regulating the temperature of a heat detector disposed on a heat exchanger. The control system includes a temperature detector (42) for determining the temperature of the hot spot sensor (32), non-liquid cooling means (50,52) for cooling the detector when its temperature is above the desired temperature range, and non-liquid heating means (48,53) for heating the detector when its temperature is below the temperatures range. The control system includes control means (82) coupling the temperature sensing means to the non-liquid heating and cooling means. By keeping the heat detector at a generally constant temperature, the accuracy of the hot spot sensor on the heat exchanger is improved.

Temperature control system for semiconductor wafer or substrate

Abstract: A temperature control system is used in conjunction with sputtering, CDV, etching, and the like apparatuses for processing a substrate on which semiconductor devices are integrated. This system responds quickly to any change in the temperature of the substrate being processed, by heating or cooling the substrate to an appropriate temperature and maintaining it constant at such temperature. The heating is accomplished by radiant heaters which heat a gas flowing through the apparatus, which in turn transfers heat to the substrate mounted on the apparatus.

Temperature control system for zoned space

Abstract: A variable air volume control system has a temperature system management device which calculates an air flow setpoint in a temperature zone as a function of a proportional term that accommodates gross temperature-setpoint errors, and integral term that provides heating or cooling load matching, and a derivative term that accommodates rapid fluctuations in the cooling or heating load, and communicates the flow setpoint to a terminal control unit to adjust the air flow to a space The terminal control unit will implement a flow setpoint as a function of the gross error in temperature in the space and a default temperature comfort setpoint upon failure of the temperature system management device to maintain a temperature in the zone

Power system battery temperature control

Abstract: Protection of rechargeable battery in power system by placing it in insulated chamber under temperature control of thermoelectric devices operated by the power system to pump heat out of the chamber or by the battery to pump heat into the chamber.

Self-adaptive design of a nonlinear temperature control system

Abstract: The paper describes the design and implementation of an unusual self-adaptive temperature control system for a nonlinear heated bar system. The design is based on a proportional-integral-plus (PIP) control scheme, combined with a special recursive algorithm which continually updates the estimates of the rapidly variable parameters which characterise a piecewise-linear model of the heated bar system. Amongst the novel features of this true digital control (TDC) system design are: the nonminimum states-space (NMSS) formulation of the control problem, which allows for state-variable feedback pole assignment using only sampled input and output signals in the control law; the incorporation of a priori information on the physical nature of the system into the recursive estimation algorithm in order to enhance its parameter tracking capabilities; the exploitation of multirate sampling; and the implementation of the linear PIP control law in a bang-bang mode using pulsewidth modulation.

Transient experimental investigation of micro heat pipes

Abstract: An experimental investigation was conducted on several small, tapered micro heat pipes specifically designed for use in the thermal control of ceramic chip carriers to verify the operation, measure the performance limits and transient behavior, and determine the accuracy of a previously developed numerical model. Several heat pipes were evaluated for transient conditions, i.e., startup or rapid changes in the thermal load. The experimental data are compared with the results of a previously developed analytical model to determine the accuracy of the model and verify the predicted trends. The experimental results indicated that the transient numerical model is capable of accurately predicting the maximum transport capacity prior to the onset of dry out, the temperature distribution throughout the longitudinal position, and the temperature difference between axial locations on the heat pipe to within 0.3°C. Although the numerical model was found to accurately predict the steady-state behavior, the numerical model substantially underestimated the transient response.

Laser system and method with temperature controlled crystal

Abstract: A laser produces a light beam which is passed through a nonlinear crystal along a beam path. The noncritical phase matching axis of the nonlinear crystal is offset at a slight angle from the beam path. The angle of exit of the second harmonic light from the nonlinear crystal varies with the temperature of the crystal. A segmented photodetector detects this beam angle and generates a temperature error signal. A temperature control element receives a temperature error signal and causes the temperature of the crystal to be adjusted.

Temperature control system for motors and power components of a material handling vehicle

Abstract: The present invention features a system and method for preventing overheating of a motor and/or power amplifier of a material handling vehicle by controlling the performance of the vehicle as a function of motor and/or power amplifier temperature. Temperature sensors are connected to the motor and power amplifier for determining their operating temperatures. A controller is connected to each temperature sensor and to the motor for controlling acceleration of the motor as a function of either or both temperatures, so that both the motor and the power amplifier will not overheat. In controlling acceleration of the motor, the invention provides a mechanism for changing acceleration by discrete steps or continuously according to a performance curve which may be linear or otherwise.

An Integrated, Full-Range Surge Control/Rotating Stall Avoidance Compressor Control System

Abstract: In this paper we present an integrated compressor control scheme capable of achieving simultaneous surge control and rotating stall avoidance over the full range of compressor operation. The approach adopted in this paper is based on a combination of closed-loop feedback control and open-loop feedforward control of throttle valve area. The feedback control is based on a compressor mass fiow measurment. The feedforward control is based on measuremets of inlet and outlet pressure and temperature. Both the feedback and feedforward controller parameters are continuously scheduled as a function of nominal operating conditions. This approach achieves simultaneous surge control and rotating stall avoidance, over the full range of compressor operation, in the face of i) inlet and outlet pressure and temperature disturbances, and ii) variations in the demanded values of both compressor speed and mass flow. Alternative approaches involving plenum pressure feedback, widely reported in literature, are shown to posess inherent performance limitations not possessed by the mass flow feedback scheme presented here.

Proportional temperature control of a sterilizer

Abstract: Apparatus and methods for proportional control of heating of a sterilizer chamber are disclosed in the application. A sterilizer chamber has heaters mounted on the walls, a wall temperature sensor and a chamber temperature sensor. The controller is operable to adjust the heat input by turning on the heaters for a variable fraction of a selected fixed interval and off for the remainder of the interval. When on the heaters provide a substantially constant heat input per unit time. The fraction of the interval during which the heaters are on is proportional to a temperature differential which comprises a setpoint temperature minus a temperature reading from one of the sensors. The controller has two, or in an alternate embodiment three, operating modes each having a unique temperature differential.

Thermo-electric temperature control arrangement for laser apparatus

Abstract: A thermo-electric laser temperature control apparatus is driven by a switching mode control circuit (317, 315). Driving current polarity (via 321 or 322) determines if the thermo-electric apparatus (305) is operating in a heat absorbent or heat generating mode. A sequencing control circuit (361-364) is used in association with the control circuit to define operative ranges of the thermo-electric temperature control apparatus consistent with maintaining proper temperature for a linear operative range for the laser. Feedback circuitry permits precision control of the converter output to limit the operative temperature range of the laser to a small precisely defined temperature window.

Hair styling appliances and heater control circuits therefor

Abstract: The invention is directed to a hair styling appliance having heat conductive portion for applying heat to the hair and an electrically energizable heater element located in thermal relationship with the heat conductive portion for causing it to be heated upon application of energy. A temperature sensor is located in thermal relationship with the heat conductive portion. The temperature sensor is electrically connected to the heater element and has a positive temperature coefficient of resistance. A pulse switching device is operatively coupled to the heater and responsively coupled to the temperature sensor for controlling energization of the heater with temperature. A selectable temperature setting circuit is coupled to the pulse switching device for varying energization of the heater in accordance with a selected temperature operation. In a particular embodiment, the temperature sensor has a characteristic in the form of a curve with a rate of resistance which gradually changes over the desired temperature range resulting in stable temperature control and fast recovery from thermal loads.

Optimal composite curing system and method

Abstract: An intelligent control system for directing a process for curing parts made of fiber-reinforced composite material in an autoclave. The system uses data gathered during the curing processing to calculate repetitively the temperature of the autoclave required to establish and maintain a predetermined cure temperature. The system accounts for heat generated by the exothermal reaction of the resin during polymerization. The control recalculates an optimal autoclave temperature at periodic intervals during the cure cycle on the basis of temperature data from the part being cured and temperature within the autoclave. The optimal autoclave temperature is determined from calculated values representing resin heat, maximum offset, lag time and degree of cure of the resin. Control signals produced by a computer that executes control algorithms stored in electronic memory accessible to the processor cause corresponding changes in the temperature of the autoclave needed to cure the part without overheating and in less time than with a conventional autoclave temperature control.