Showing papers on "Temperature control published in 1994"

Method and apparatus for electrosurgically treating tissue

Abstract: Tissue impedance or tissue impedance in combination with tissue temperature is used to control electrosurgical tissue treatment. Tissue impedance alone provides better control of electrosurgical treatment by determining an initial maximum tissue impedance, a minimum tissue impedance selecting a point between the maximum and minimum impedances, preferably the average, as an impedance threshold, and turning off rf power to the electrosurgical instrument when the impedance reaches the threshold as it rises from the minimum. Control may also be by the combination of tissue impedance and temperature. Temperature is controlled to maintain a selected preferred temperature and a maximum temperature is also selected so that if the tissue reaches the maximum temperature, power is turned off. Impedance control is combined with temperature control so that the temperature of the instrument is maintained at a selected preferred temperature unless a maximum temperature is exceeded, which normally will not happen. The impedance is also monitored with maximum and minimum values being determined as well as a threshold impedance between the max and the min. When the threshold, preferably the average impedance, is reached, power is removed from the instrument.

Apparatus and method for controlling distribution of electrical energy to a space conditioning load

Abstract: An apparatus and method for controlling energy supplied to a space conditioning load and for overriding a load control operation in response to measuring certain space temperatures within a closed environment. The load control apparatus includes a control device connected to an electrical distribution network and to a space conditioning load and a temperature sensing device connected to the control device. The control device conducts a load shedding operation to control distribution of electrical energy to the space conditioning load in response to command signals supplied by a remote command center. The temperature sensing device operates to override the load shedding operation by outputting a control override signal to the control device in response to sensing certain space temperatures within the closed environment. If the temperature control device is connected to an air conditioning system, the temperature sensing device causes the control device to terminate the load shedding operation prior to expiration of a selected time period in response to measuring a space temperature that exceeds a maximum space temperature limit. In contrast, if the temperature control device is connected to a forced air heating system, the temperature sensing device causes the control device to terminate the load shedding operation when a measured space temperature drops below a minimum space temperature limit. The maximum space temperature limit is greater than the control temperature setpoint of a thermostat that controls the space conditioning operations, whereas the minimum space temperature limit is less than the control temperature setpoint.

Method and apparatus for controlling temperature in rapid heat treatment system

Abstract: A temperature control method in a rapid heat treatment apparatus comprising simulatively heating dummy wafers in a process tube and previously detecting and grasping by temperature sensors a wafer temperature rising pattern, a heater temperature rising pattern and an internal atmosphere temperature rising pattern, arranging wafers to be processed in the process tube, detecting a temperature of each zone and that of each heater element by the temperature sensors, upon heating the wafers, and controlling each heater element on the basis of the detected temperatures and the wafer, heater and internal atmosphere temperature rising patterns by a controller to rapidly and uniformly raise the temperature of each wafer until the temperature of the wafers in each zone reaches the intended one and becomes stable

Three‐Dimensional Thermal Modeling of Lithium‐Polymer Batteries under Galvanostatic Discharge and Dynamic Power Profile

Abstract: A three-dimensional model is developed to simulate and compare heat generation and transport within a lithium polymer electrolyte battery under galvanostatic discharges and a dynamic power profile [the Simplified Federal Urban Driving Schedule (SFUDS)]. Emphasis is placed on the maintenance of the operation temperature and temperature uniformity within a battery by designing a suitable thermal management system. The results indicate that the anisotropic thermal conductivity within the battery is an important factor influencing thermal performance and should be taken into consideration in battery design. On the one hand, because of the low effective thermal conductivity across a laminated cell stack, steep temperature distributions may be caused if cooling channels or electric heaters are placed at the two ends of a cell stack. On the other hand, the relatively large average thermal conductivity along the width and height directions allows more efficient heat removal or addition, and thus facilitates the maintenance of uniform operating temperature. Under the SFUDS power profile, the time-averaged heat generation rate is low, and therefore a high-performance insulation material is required to maintain the operating temperature. The thermal model has been applied to study the effectiveness of different arrangements of cooling channels and electric heaters and tomore » select suitable heating intensities and insulating materials.« less

Temperature regulated specimen transporter

Abstract: A temperature regulated specimen transporter for controlling the temperature and environment of a clinical specimen during transportation thereof comprising an insulated and thermally conductive storage compartment; a heat sink mechanism coupled to the storage compartment for heating and cooling the storage compartment; a temperature control mechanism coupled to the storage compartment for setting a plurality of desired temperature set points; a temperature sensing mechanism coupled to the heat sink mechanism and temperature control mechanism, the temperature sensing mechanism having a first orientation for allowing the heat sink mechanism to heat the storage compartment and a second orientation for allowing the heat sink mechanism to cool the storage compartment based on the desired temperature set points; and a power source mechanism for energizing and de-energizing the heat sink mechanism, temperature control mechanism, and temperature sensing mechanism.

Temperature control system having central control for thermostats

Abstract: Disclosed herein is a temperature control system for multi-zone temperature control with setback control. The system includes a thermostat (10) associated with each zone of a building, and a central control unit (12) which communicates with each thermostat (10) to send temperature setpoint values to each thermostat (10) for the purpose of conserving energy and reducing energy consumption during certain times of the day. Each thermostat (10) is associated with either a heating or cooling device (14), where setup temperature values are sent from the central control unit (12) to the thermostats (10) where cooling devices are used in place of heating devices. The thermostats (10) are designed to operate as stand-alone units which control the temperature within a zone based upon a temperature setpoint stored at the unit. The temperature setpoint values are replaced by the higher or lower temperature setpoint values transmitted to the thermostats by the control units during setback or setup time periods. To avoid the requirement of installing communication wires between the central control unit (12) and thermostat (10), each thermostat (10) and the central control unit (12) includes communications circuitry (30, 46) which allows the thermostats (10) and control unit (12) to communicate over the power conductors (36, 38) within the building.

Modeling, Identification, and Control of Rapid Thermal Processing Systems

Abstract: A wafer temperature control system is developed for rapid thermal processing (RTP) semiconductor manufacturing equipment. The control algorithm is based on a physical model describing the heat transfer effects in advanced RTP equipment. A model identification procedure is proposed to estimate the uncertain parameters of the model from a set of experiments. Through singular value analysis, the impact of equipment design on feedback controller development is studied. An internal model control (IMC) design methodology is used to develop a low‐order multivariable feedback control algorithm. The feedback controller is coordinated with additional modules including feedforward control and gain scheduling to achieve improved performance and flexibility. The algorithms are applied to three different multizone RTP systems. Temperature controlled ramps are demonstrated from 20 to 900°C at 45°C/s with less than ±5°C during the ramp at high temperatures and less than ±1°C average nonuniformity during steady state as measured by three radially distributed temperature sensors.

Temperature control for a variable frequency CPU

Abstract: A thermal control system for variable speed microprocessor with a piecewise estimate of temperature change. The estimate is modeled after actual temperature change measurements of a microprocessor operating at low and high speeds and is recorded in a digital format in storage registers, one set of registers for each operating frequency. A counter counts sample microprocessor clock signals for a time over which the microprocessor speed is operating at a specific speed and provides a basic count signal. This basic count signal is incremented or decremented by comparison with stored values of the piecewise estimate of temperature change. As the basic signal increases or decreases, new slopes are provided to the counter for adjusting the basic count, upwards or downwards, depending on whether the system speed is high, intermediate or low. The adjusted counter output is also fed to comparators, which monitor a desired upper and lower temperature limit. As the upper limit is approached, control logic implements a throttling algorithm to maintain temperature in the desired range. The present invention takes into account the operating history of the system in a particular environment since the system powers on, including idleness of the system.

Scroll compressor having high temperature control

Abstract: A thermal protection system for a scroll compressor has a temperature sensor which is positioned directly within the discharge passage of the scroll compressor by being directed through an access passageway between the discharge zone and the suction zone of the compressor. The lead wires from the temperature sensor are wired in series with the normal motor temperature sensor circuit to provide the scroll discharge temperature control function as an integral part of the motor temperature control system located within the hermetic shell of the compressor. An additional embodiment of the present invention not only detects discharge gas temperatures but it also has the ability to detect the actual temperature of other selected compressor components.

Windshield temperature control system

Abstract: A windshield temperature control system (200) monitors aircraft operating (240) and environmental (246) conditions, and determines, based on the fixed physical properties of the windshield (250,251 ), a required film temperature necessary to produce a heat output to maintain the internal and/or external temperature of the windshield at a desired temperature. The heat output is based on a total heat loss including internal heat loss and external convective, evaporative, sensible and radiation heat loss, and a film temperature error defined as the difference (340) between required film temperature and actual film temperature is applied via proportional (355) and integral (350) control paths to produce zero steady state film temperature error. The desired external temperature is selected to be sufficiently above freezing, i.e., 0° C., to prevent ice formation on the windshield, and the desired internal temperature is selected to be sufficiently above the cockpit air dew point to prevent condensation on the internal surfaces of the windshield. During start-up at low film temperature, film temperature error is filtered (315) to gradually heat up the film at a rate dependent upon the magnitude of the error. After a warm-up delay (307), film temperature error is compared to a fixed temperature error limit (385), the exceedance of which will cause termination of film heating (390) to thereby prevent over temperature of the windshield.

Barrel temperature state controller for injection molding machine

Abstract: An improved temperature control system using a state controller with two degrees of freedom to regulate the temperature of the barrel of an injection molding machine is disclosed. The control system divides the temperature of the barrel into longitudinally-extending zones and radially extending layers within each zone. Heat transfer calculations which include the effects of heat transfer between all the layers within the zones are performed for a set time in the future to accurately determine the heat needed from the heater band to reach the operator set point temperature. The duty cycle for the heater bands is thus accurately set to give a more responsive and accurate control than heretofore possible. The controller additionally includes factors for accounting for heat disturbances present in the injection molding process. In addition each system is calibrated for each machine to insure accurate formulation of machine specific parameters such as heat transfer co-efficients used in the control.

Temperature controller for ink jet printing

Abstract: A temperature control unit is incorporated directly into the printhead (10) of an ink jet printing system to provide temperature control. The temperature control system includes a heat pump assembly consisting of at least one thermoelectric device (40, 63, 64), coupled to a heat exchanger (42, 62) through which the ink flows. The thermoelectric device (40, 63, 64) conveys heat to or from the heat exchanger (30) carrying the ink depending upon actual ink temperature versus a desired temperature. If the ink is too hot, excess heat is dumped to the heat exchanger (30) (or second heat exchanger (42, 62)) which may be air or liquid cooled. In the event that the ink is too cool, the electrical current to the TED (40, 63, 64) is reversed and heat is pumped to the ink from the heat exchangers (30, 42, 62).

Gas/air ratio control apparatus for a temperature control loop for gas appliances

Abstract: The invention relates to a gas/air ratio control apparatus for a temperature control loop for household gas appliances, in particular for domestic/direct hot water units and combined direct hot water/central heating units, for temperature control of domestic and/or heating water The invention is particularly suitable for household appliances up to 120 KW The gas/air ratio control apparatus comprises a controllable fan (3) for supplying a predetermined air stream (2-2) to a burner (4) in dependence on the detected actual temperature (T Actual ) and the desired target temperature (T Target ) of the heating and/or domestic hot water; and a pressure-controllable valve (8) for controlling the supply of a specified fuel quantity (1) to the burner (4) in dependency exclusively on the absolute pressure of the air stream (2-2) produced by the controllable fan (3) The inventive temperature control apparatus operates in an air/fuel regulating range of 20% to 100%, the controllable valve (8) supplying a fuel quantity (1) to the burner (4) having a pressure at a ratio of 1:1 to the absolute pressure of the air stream (2-2) produced by the controllable fan (3) The system uses only one pressure sensing line (11) and can always be brought into a safe condition when faults appear in the burner (4)

Fuzzy control for temperature and humidity in refrigeration systems

Abstract: In this paper, improved control strategies for refrigeration systems based on fuzzy logic are discussed. For the development of these control concepts physical understanding of the process dynamics is needed. Therefore, a thermodynamic model is used to study the dynamic properties of the cold store, with emphasis on the coupling of temperature and relative humidity. With this knowledge, together with the heuristic knowledge of refrigeration engineers, rule-based control strategies for refrigeration systems are proposed. For the implementation the fuzzy logic method is used. The design with fuzzy logic allows one to take into account the complex coupling of the dynamic variables temperature and humidity in a straightforward manner. A survey of the control structure and simulation results are presented. It is shown that the fuzzy controller gives favourable process behaviour, e.g. under the influence of disturbances or after changes of set points. >

Power control circuit for improved power application and temperature control of thermoelectric coolers and method for controlling thereof

Abstract: A power control circuit for improved temperature control of thermoelectric devices to maintain the temperature of thermoelectric devices at a set point. The circuit includes an electrical power source; a rectifying device to provide rectified alternating current from the electrical power source; a comparator device; circuitry for providing a predetermined voltage to the inverting input of the comparator device derived from the rectified alternating current; a sensor device to monitor the temperature associated with the thermoelectric device; circuitry for providing an adjustable DC voltage to the non-inverting input of the comparator; a programmable control device to receive an output from the sensor device and provide an output to the circuitry for providing an adjustable DC voltage; a switching device connected between the thermoelectric device and the rectified alternating current; and control circuitry which is coupled between the switching device and the output of the comparator device and is controlled by the output of the comparator device, the control circuitry activates and deactivates the switching device to apply power to the thermoelectric device when the operating temperature of the thermoelectric device is different than the set point temperature to maintain the thermoelectric device at the set point temperature with minimum variations therefrom. A push-pull transistor configuration is used with the "pulse positioning" power supply allowing bi-polar control of thermoelectric device assemblies.

Temperature predicting system for internal combustion engine and temperature control system including same

Abstract: A temperature projecting system includes a temperature sensor for monitoring a temperature of an objective portion where the temperature changes depending on an engine operating condition. The temperature projecting system projects an actual temperature of the objective portion based on the monitored temperature but free of a first-order lag of the temperature sensor. A temperature control system includes the temperature projecting system. The temperature control system derives a correction amount for a basic control amount of an actuator based on a difference between the projected actual temperature and a target temperature. The basic control amount is corrected by the correction amount to derive a corrected control amount which controls the engine operating condition and thus the temperature of the objective portion.

Temperature control method and apparatus

Abstract: Power demand is monitored and temperature control effected in response. If monitored power demand is below a predetermined power demand limit, a selected desired temperature setpoint is used as the temperature to be attained. If monitored power demand is above the power demand limit, a modified temperature setpoint is used. The modified temperature setpoint preferably is determined to maintain a still comfortable temperature while also reducing power demand.

Implementation of Model-Based Optimal Temperature Profiles for Autoclave Curing of Composites Using a Knowledge-Based System

Abstract: The manufacture of composite parts using the autoclave curing process requires the specification of the autoclave temperature as a function of time. It is desired to obtain a part meeting given specifications in the minimum amount of time. A recently developed methodology was used to optimize the process using a mathematical simulation of the cure process. The optimal profile so obtained was implemented on a full-sized autoclave which is interfaced to a proprietary control system running on a Hewlett-Packard computer, using a knowledge-based system (KBS) as a supervisor. In order to account for discrepancies between the simulation and the actual process, we have followed a strategy that uses process trend analysis of the simulation output as the basis for control. The whole process is split up into episodes based on an analysis of the variable profiles. This information is used in conjunction with other knowledge about the system embedded in the KBS to adjust the set point of the autoclave temperature so that the process follows the same trends as dictated by the model-based optimization. Using this system, it was possible to guide the cure robustly along anoptimal path, consistently yielding superior quality parts despite the variability of the raw materials. This procedure allows us to optimize a process independently using even an inexact simulation and apply the optimal profiles obtained therefrom

Control of MMST RTP: repeatability, uniformity, and integration for flexible manufacturing [ICs]

Abstract: A real-time multivariable strategy is used to control the uniformity and repeatability of wafer temperature in rapid thermal processing (RTP) semiconductor device manufacturing equipment. This strategy is based on a physical model of the process where the model parameters are estimated using an experimental design procedure. The internal model control (IMC) law design methodology is used to automatically compute the lamp powers to a multizone array of concentric heating zones to achieve wafer temperature uniformity. Control actions are made in response to real-time feedback information provided by temperature sensing, via pyrometry, at multiple points across the wafer. Several modules, including model-scheduling and antiovershoot, are coordinated with IMC to achieve temperature control specifications. The control strategy, originally developed for prototype equipment at Stanford University, is analyzed via the customization, integration, and performance on eight RTP reactors at Texas Instruments conducting thirteen different thermal fabrication operations of two sub-half-micron CMOS process technologies used in the the Microelectronics Manufacturing Science and Technology (MMST) program. >

Fixing apparatus with variable fixing temperature

Abstract: A fixing apparatus includes a heating member (6); a temperature detecting member (4) for detecting the temperature of the heating member (6); a power supply controller for controlling the power supply to the heating member (6) so that the temperature detected by the temperature detecting element (4) during a fixing operation is maintained substantially constant at a predetermined fixing temperature; and temperature selecting means for selecting a fixing temperature in response to both the temperature or the heating member before beginning of the fixing temperature control and a rate of the temperature change of the heating member upon supplying a predetermined amount of power to the heating member or upon turning it off.

Method and apparatus for controlling device temperature during transmissions

Abstract: A communication device (200) supporting transmissions provides transmission related device temperature control The communication device (200) has a particular portion (244) subject to an increase in temperature resulting from the transmissions A message is provided for transmission by the communication device (200) which has a data communication protocol (224) governing message transmission Temperature control is effected by determining temperature information for the particular portion (244) of the communication device (200) and by modifying operation of the data communication protocol (224) based in part on the temperature information

Mobile thermostat to control space temperature in the building

Abstract: The present invention is related to many space heating and cooling systems, which include central building heating and/or cooling source, such as boiler, chiller, furnace, air handling unit, etc. and which have at least one stationary room thermostat to control climate conditions in the building. It is suggested in addition to a stationary thermostat to use an extra thermostat, so called mobile thermostat, to provide flexible room air temperature control at any building location which is critical at the particular moment, including the rooms which do not have a stationary thermostats. This mobile thermostat has an authority, if it is necessary, to be override control of the stationary thermostat at any time and, therefore, to control room space heating and/or space cooling at any particular location to provide a required comfort in any room in the building. The mobile thermostat generates a signal which is transmitted to the master controller, which is installed on central building space heating and/or space cooling plant or on room space heating and/or space cooling unit. A signal through receiving means changes the output capacity of a building plant or room unit responsively to the signal from mobile thermostat to maintain a room air temperature at the particular location in accordance with a setpoint temperature of mobile thermostat.

Control of thermoplastic tow placement

Abstract: A control architecture involves two control loops, one for controlling heat input to a moving composite structure and the other controlling the speed of the structure to control quality of the product being formed. Since velocity and heat input affect the temperature of the composite there is cross coupling between the control loops so that either or both can be used to control the temperature. Preferably the invention uses the velocity or speed of the composite as the primary control, i.e., the controller automatically seeks the proper laydown velocity for the current heat input. If the energy source is not providing sufficient heat, the process slows down until the proper temperature is reached. This ensures that the composite material passing through the process is always at the proper temperature.

Multi-point semiconductor wafer fabrication process temperature control system

Abstract: A computer controlled system for real-time control of semiconductor wafer fabrication process uses a multi-point, real-time, non-invasive, in-situ pyrometry-based temperature sensor with emissivity compensation to produce semiconductor wafer reflectance, transmittance, and radiant heat energy measurements. The temperature values that the sensor determines are true temperatures for various points on the wafer. The process control computer stores surface roughness values for the semiconductor wafer being examined. The surface roughness values are produced by surface roughness sensor that makes non-invasive and in-situ measurements. The surface roughness sensor performs roughness measurements of the semiconductor wafer based on coherent reflectance and scatter reflectance of the wafer. Based on surface roughness measurements, the process control computer can use the real-time, in-situ measurements of the multi-point pyrometry-based sensor to obtain real-time measurements of time wafer temperature distribution. By associating a multi-zone lamp module having a real-time controller with the present invention a feedback circuit is provided for real-time precision semiconductor wafer process control.

On flow and supply temperature control in district heating systems

Abstract: This paper discusses how the control of the flow and the supply temperature in district heating systems can be optimized, utilizing stochastic modelling, prediction and control methods. The main objective is to reduce heat production costs and heat losses in the transmission and distribution net by minimizing the supply temperature at the district heating plant. This control strategy is reasonable, in particular, if the heat production takes place at a combined heat and power (CHP) plant. The control strategy is subject to some restrictions, e.g. that the total heat requirement for all consumers is supplied at any time, and each individual consumer is guaranteed some minimum supply temperature at any time. Another important restriction is that the variation in time of the supply temperature is kept as small as possible. This concept has been incorporated in the program package, PRESS, developed at the Technical University of Denmark. PRESS has been applied and tested, e.g. at Vestkraft in Esbjerg, Denmark, and significant saving potentials have been documented. PRESS is now distributed by the Danish District Heating Association.

Frequency stabilization method of semiconductor laser, frequency-stabilized light source and laser module

Abstract: A frequency stabilization method of a semiconductor laser is provided. A driving current, a forward voltage and an output light power of the laser mounted on a heat sink is detected. A temperature of the heat sink is also detected. A consumption power of the laser is obtained from the driving current and voltage thus detected, providing a relationship between the output light power and the consumption power. The driving current is controlled so that the output light power is kept constant, and the temperature of the heat sink is controlled based on the relationship so that a temperature of an active layer of the laser is maintained. The output light power is kept constant and at the same time, any temperature change of the active layer is cancelled through the temperature control of the heat sink. Even if the consumption power changes due to an leakage current and/or a recombination current without luminescence to maintain the output light power during long time operation, the temperature of the active layer is maintained by cancelling the consumption power change through the temperature control of the heat sink. Thus, the oscillation frequency of the semiconductor laser can be stabilized at a given value.

Supplemental heat control system with duct temperature sensor and variable setpoint

Abstract: A heating system has a primary heat source such as a heat pump, with a capacity that occasionally needs to be supplemented from a supplemental heat source such as an electrical resistance heater. The heating system heats and circulates a medium such as air via supply and return ducts. A thermostat responsive to the heated space has two outputs for operation at different user-selected temperatures defining stages of operation at which the primary and secondary heat sources are normally drawn upon. The invention controls the duct temperature by activating the supplemental heat source according to a further setpoint, that is adjusted by a processor or other control circuit. A temperature sensor allows the control circuit to determine the duct temperature. The control circuit is also coupled to the two thermostat outputs and to a memory register storing the variable duct temperature setpoint. The duct temperature is compared to the duct temperature setpoint and the supplemental heating means is enabled to increase the duct temperature when the duct temperature falls below the variable setpoint. The control circuit adjusts the duct temperature setpoint upwardly upon occurrence of the temperature in the heated space dropping below a lower one of the space temperature setpoints (indicating that the heat pump is not keeping up), and downwardly upon the temperature in the heated space exceeding a higher one of the two space temperature setpoints (indicating that the heating capacity is adequate and use of the resistance heater should be reduced).