Showing papers on "Temperature control published in 1999"

An Intelligent Environment Must Be Adaptive

Abstract: Michael C. Mozer, University of Colorado What will the home of the future look like? One popular vision is that household devices-appliances, entertainment centers, phones, thermostats, lights-will be endowed with microprocessors that allow the devices to communicate with one another and with the home’s inhabitants. The dishwasher can ask the water heater whether the water temperature is adequate; inhabitants can telephone home and remotely instruct the VCR to record a favonte show; the TV could select news stones of special interest to the inhabitant; the stereo might lower its volume when the phone rings; and the clothes dryer might make an announcement over an intercom system when it has completed its cycle.

Impact of nonlinear heat transfer on temperature control in regional hyperthermia

Abstract: We describe an optimization process specially designed for regional hyperthermia of deep-seated tumors in order to achieve desired steady-state temperature distributions. A nonlinear three-dimensional heat transfer model based on temperature-dependent blood perfusion is applied to predict the temperature. Using linearly implicit methods in time and adaptive multilevel finite elements in space, we are able to integrate efficiently the instationary nonlinear heat equation with high accuracy. Optimal heating is obtained by minimizing an integral objective function which measures the distance between desired and model predicted temperatures. A sequence of minima is calculated from successively improved constant-rate perfusion models employing a damped Newton method in an inner iteration. We compare temperature distributions for two individual patients calculated on coarse and fine spatial grids and present numerical results of optimizations for a Sigma 60 Applicator of the BSD 2000 Hyperthermia System.

Temperature control system for process chamber

Abstract: Temperature control of a process chamber 25 is achieved by directing a flow of gas at an external surface 100 of the chamber 25. In one aspect, gas directed at the chamber 25 passes through a gas flow amplifier 115 that increases the gas flow. Gas for the temperature control can be drawn in from the ambient air and, after passing over the process chamber 25, the gas can flow out through an outlet 150. Data is presented demonstrating superior temperature control performance over a conventional system.

Temperature control system for a thermal reactor

Abstract: A temperature control system for a thermal reactor is disclosed that addresses many of the problems in the art. In accordance with one aspect of the disclosed control system, a plurality of temperature controllers are employed. Each temperature controller employs one or more dynamic models that are optimized for a given temperature range. The temperature range over which a particular controller is optimized is preferably generally exclusive of the temperature ranges over which other controllers of the plurality of temperature controllers are optimized. In accordance with another aspect of the control system, the control system employs enhanced ramp trajectory logic. In accordance with another aspect of the control system, the control system employs a virtual temperature sensor in the event of a hardware failure of the corresponding non-virtual temperature sensor. Upon the detection of a failure of the non-virtual temperature sensor, the temperature control system automatically substitutes a virtual temperature sensor in its place as a control system input. In accordance with a still further aspect of the temperature control system, the control system is provided with control logic that switches the control mode of the system in the event of a failure of a heating element. All of the foregoing aspect of the present invention may be combined into a single temperature controller. Alternatively, these temperature control system improvements may be incorporated as individual elements, without reliance on the other inventive aspects disclosed herein.

Cooling system for indwelling heat exchange catheter

Abstract: A system for exchanging heat with the body of a patient for cooling or warming the patient provides for automatic temperature control in accordance with the monitored temperature of the patient. The system comprises a temperature control module and temperature probes for making body core temperature measurements. The body core temperature measurements are used to control the temperature of fluid circulating within the fluid circuit.

Integrated devices and systems for performing temperature controlled reactions and analyses

Abstract: Reactor systems that include a reaction receptacle that includes a plurality of reservoirs disposed in the surface of a substrate. The reactor system also typically includes a temperature control element having at least a first heat exchanger thermally coupled to it. The heat exchanger is, in turn, disposed within the at least one of the reservoirs whereby the heat exchanger transfers heat to or from a fluid disposed within the reservoir, which heat is conducted to or from the temperature control element.

Processing method for motion measurement

Abstract: A processing method for motion measurement, which is adapted to apply to output signals proportional to rotation and translational motion of a carrier, respectively from rate sensors and acceleration sensors, is more suitable for emerging MEMS rate and acceleration sensors. Compared with a conventional IMU, the processing method utilizes a feedforward open-loop signal processing scheme to obtain highly accurate motion measurements by means of signal digitizing, temperature control and compensation, sensor error and misalignment calibrations, attitude updating, and damping control loops, and dramatically shrinks the size of mechanical and electronic hardware and power consumption, meanwhile, obtains highly accurate motion measurements.

Half-bridge series resonant inverter for induction heating applications with load-adaptive PFM control strategy

Abstract: This paper presents an effective control scheme incorporated in a voltage-fed half-bridge series resonant inverter for induction heating applications, which is based upon a load-adaptive tuned frequency tracking control strategy using a PLL (phase locked loop) and its peripheral control circuit. The proposed control strategy ensures stable operation characteristics of the overall inverter system and ZVS (zero voltage switching) operation in spite of sensitive load parameters variations as well as power regulation, especially for nonmagnetic heating loads. The operating principle and the design procedure of the inverter system with the proposed control scheme are described. Also, simulation results and performance characteristics in the steady-state are shown as compared with experimental results for a prototype induction cooking system rated at 1.2 kW.

Temperature control of electronic devices using power following feedback

Abstract: A method for controlling a device temperature measures a parameter related to device power consumption and utilizes the parameter to control the device temperature. This can be achieved with a system including a heat exchanger, a power monitor, and a circuit which controls the temperature setting of the heat exchanger. The circuit uses as inputs the power level, heat exchanger temperature, and set point. The system thus eliminates the need for temperature sensing devices in or connected to a chip, responds to the temperature of the device and not the package, can be used for high volume chip manufacturing, does not require significant surface area of a device for temperature sensing, and eliminates the need for chip power profiles. Significantly, the system allows a set point to be maintained with minimal overshoot or undershoot.

Thermostat incorporating thin film carbon dioxide sensor and environmental control system

Abstract: A system for monitoring and modifying the quality and temperature of air within a conditioned space includes a blower unit, a damper unit for selectively admitting outside air into the conditioned space, a temperature moderating unit and a control unit. The control unit includes a thermostat and conventional temperature control apparatus for selectively activating the temperature moderating unit to maintain the desired temperature in the conditioned space. The control unit also incorporates CO2 concentration measuring and control apparatus which includes a small CO2 sensor. The CO2 sensor includes a cathode, an anode and a solid electrolyte disposed intermediate and electrically in contact with each of the cathode and the anode to effect a primary electrical cell. A heater and a heater thermostat serve to maintain the temperature of the cell at about 250° C. The cathode and anode materials and the chemical composition of the electrolyte are further selected such that the voltage generated across the heated cell varies in accordance with the CO2 concentration. CO2 concentration modifying apparatus is responsive to sensing a first predetermined CO2 concentration for turning on the blower unit and to sensing a second, higher, predetermined CO2 concentration for actuating the damper unit to admit outside air.

Temperature control system and method for efficiently obtaining and maintaining the temperature in a conditioned space

Abstract: A method for efficiently maintaining the temperature of fluid in a conditioned space at a predetermined set point temperature, the method comprising the steps of: (a) operating the temperature control system in a first operating mode; (b) sensing the temperature of the conditioned space fluid; (c) calculating the Integral Error of the temperature of the conditioned space fluid; and (d) if the Integral Error equals or exceeds a predetermined Integral Error threshold value for the first operating mode, switching the unit to a second operating mode.

Apparatus, method and system of liquid-based, wide range, fast response temperature control of electric devices

Abstract: An active temperature control system for a DUT utilizes a heat sink containing HFE7100 liquid and an electric heater. The liquid is cooled below the set point and the heater is used to bring the DUT up to the set point. Set points in the range of −10 degrees C. to +110 degrees C. can be achieved. The heat sink utilizes only a single coolant for all of the set points, allowing set points to be changed within a few minutes. At a given set point, the heater provides a quick response to offset the effect of self-heating and keep the set point deviation to within a few degrees C. Power following techniques can be utilized to achieve the quick response.

Calculation of a two-temperature plasma composition : bases and application to SF6

Abstract: In this paper we discuss the use of generalized Saha and Guldberg-Waage equations for calculating the composition of a two-temperature SF6 plasma in a pressure range 0.1-1.6 MPa, for an electron temperature in the range 300-20 000 K. We compare two sets of two-temperature laws and we recommend the expressions proposed by the team from Eindhoven. Furthermore, knowing the great influence of the choice of the excitation temperature on the plasma composition, we propose, on the basis of a chemical kinetics approach, a simple general relation allowing the calculation of this temperature versus the electron temperature, the heavy particle temperature and the electron number density. The application of these relations to a real case of a two-temperature SF6 arc plasma gives a realistic radial profile of the electron number density.

Look-ahead closed-loop thermal management

Abstract: Thermal management within an electrically powered systems requires monitoring, from time-to-time, both electrical power consumption and temperature within the system The power consumption and temperature data thus obtained permits developing over time a thermal model for the system After a thermal model for the system has been thus developed, the model together with the presently sensed electrical power consumption, and the system temperature are used to predict a thermal trend for the system The predicted thermal trend thus obtained for the system is then used in effecting a temperature control strategy within the electrically powered system

Variable-air-volume diffuser, actuator assembly and method

Abstract: An adaptive control device (77) and method (102-108) for control of the operation of an actuator (72), and particularly thermally-powered actuator (72)of the type used in a variable-air-volume diffuser (71). The preferred adaptive control device is an expert system circuit which controls a heater (74) provided on a thermally-powered actuator (72) to implement an adaptive process (102-108) in which a sensed variable, such as room air temperature, is driven toward a target temperature control range. Most preferably, the process steps (106) include driving the room air temperature toward a gross (broader) temperature control range by moving a diffuser damper assembly (80) to a substantially fully open or substantially fully closed position. Thereafter, and while inside the gross temperature control range, the process steps (107, 108) include adjustments to the position of the damper assembly (80) are made only when a sensed parameter, preferably the supply air flow rate, is in a stable condition.

Seeding Effect on Batch Crystallization of Potassium Sulfate under Natural Cooling Mode and a Simple Design Method of Crystallizer

Abstract: Potassium sulfate was crystallized in a seeded batch cooling crystallizer with no temperature control or natural cooling. Above a critical seed concentration, uni-modal product of grown seeds was obtained even under a natural cooling mode with practically no nucleation. This ideal growth of seed crystals is contrary to the common belief that a natural cooling mode produces small size products with enormous secondary nucleation. The critical seed concentration can be determined easily with data from a laboratory crystallizer on the seed chart, in which the product mean mass size normalized with the seed mean mass size is plotted as a function of seed concentration with seed size as a parameter. A simple and practical method to design a batch crystallizer to be operated with no nucleation has been proposed.

Control of part weight in injection molding of amorphous thermoplastics

Abstract: Two methods are proposed for the control of part weight in injection molding. In the PT method, part weight control is achieved by controlling the temperature and pressure of the melt in the cavity at gate freeze time. This time is considered to occur when the cavity melt pressure starts to decrease from its peak value. For the purposes of control, the bulk melt temperature is estimated from measurements by surface thermocouples at strategic locations in the cavity. A cascade scheme is implemented for the control of bulk temperature from cycle to cycle. A self-tuning algorithm, with an observer, is employed for controlling the cavity pressure-time profile, to follow a set point trajectory during a cycle. In PWT control, the coolant temperature is controlled, while the peak cavity pressure is adjusted in a given cycle to compensate for bulk melt temperature deviations measured in the previous cycle. Both PT and PWT control reduce variance in part weight. PWT control appears to yield the best results.

Central venous line catheter having temperature control system

Abstract: A system for controlling patient temperature uses a central venous line catheter (20) having a heat exchange element (24). The central venous line catheter (20) is provided with one or more lumens for providing access to the central blood supply of the patient, and with additional lumens for communicating heat exchange fluid to the heat exchange element (24). Heat exchange fluid temperature is controlled through a feed back loop in which patient temperature is sensed, used to control a temperature control unit comprising a heating device, and/or cooling device in heat exchange relationship with the heat exchange fluid. A tubing set transports the heat exchange fluid between the central venous line (20), and the temperature control unit, with a pump serving to circulate the fluid in a closed fluid circuit in the system.

Method for balancing the air/fuel ratio to each cylinder of an engine

Abstract: A method for controlling delivery of fuel to each cylinder (14) of an engine (12) by adjusting the appropriate fuel valve duration times to each such cylinder (14) based upon either a desired cylinder exhaust port temperature, or a predetermined detonation level. By using the exhaust port temperature measurements and/or detonation level measurements from each individual cylinder (14) as a controlling parameter, the delivery of fuel to that particular cylinder can be trimmed to achieve the desired exhaust port temperature and/or predetermined detonation level. Balancing the exhaust port temperature and/or detonation level for each such cylinder (14) to a common desired exhaust port temperature and/or detonation level likewise produces a substantially identical air/fuel ratio in each such cylinder (14). Both the exhaust port temperature control loop (70) and the detonation control loop (94, 112) can be initiated at predetermined intervals so as to continuously maintain a balanced air/fuel ratio to each cylinder (14) in any particular engine (12) and, in certain situations, both control loops (70, 94 or 70, 94, 112) can operate simultaneously with respect to any particular cylinder (14).

Design and tuning of robust PID controller for HVAC systems

Abstract: This paper concerns the development of a new design and tuning method for use with robust proportional-plus-integral-plus-derivative (PID) controllers that are commonly used in the heating, ventilating, and air-conditioning (HVAC) fields The robust PID controller is designed for temperature control of a single-zone environmental space Although the dynamics of environmental space are described by higher-order transfer functions, most HVAC plants are approximated by first-order lag plus deadtime systems Its control performance is examined for this commonly approximated controlled plant Since most HVAC plants are complex with nonlinearity, distributed parameters, and multivariables, a single set of PID gains does not necessarily yield a satisfactory control performance For this reason, the PID controller must be designed as a robust control system considering model uncertainty caused by changes in characteristics of the plant The PID gains obtained by solving a two-disk type of mixed sensitivity problem can be modified by contrast to those tuned by the traditional Ziegler-Nichols rule The results, which are surprisingly simple, are given as linear functions of ratio of deadtime to time constant for robustness The numerical simulation and the experiments on a commercial-size test plant for air conditioning suggest that the robust PID controller proposed in this papermore » is effective enough for practical applications« less

Method and apparatus for catalyst temperature control

Abstract: An apparatus for minimizing the total quantity of hydrocarbon emissions from a catalytic converter in the exhaust path of an internal combustion engine includes a temperature sensor coupled to the catalytic converter for continuously generating an output signal representative of the catalyst temperature, and a controller for receiving the output signal from the temperature sensor and for enhancing the output signal to have a response time of less than one second. The controller adjusts one or more operating parameters of the engine to cause the catalyst temperature to rapidly rise when the catalyst temperature is less than the catalytic converter light-off temperature and adjusts one or more operating parameters of the engine to minimize the rate of hydrocarbon emissions output from the catalytic converter when the catalyst temperature is greater than the catalytic converter light-off temperature.

Inverse model-based real-time control for temperature uniformity of RTCVD

Abstract: A reduced-order model describing a rapid thermal chemical vapor deposition (RTCVD) process is utilized for real-time model based control for temperature uniformity across the wafer. Feedback is based on temperature measurements at selected points on the wafer surface. The feedback controller is designed using the internal model control (IMC) structure, especially modified to handle systems described by ordinary differential and algebraic equations. The IMC controller is obtained using optimal control theory on singular arcs extended for multi-input systems. Its performance is also compared with one based on the Hirschorn inverse of the model. The proposed scheme is tested with extensive simulations where the full-order model is used to emulate the process. Several cases of significant uncertainty, including model parameter errors, process disturbances, actuator errors, and measurement noise are used to test the robustness of the controller to real life situations. Both controllers succeed in achieving temperature uniformity well within the desirable bounds, even in cases where several sources of uncertainty are simultaneously present with measurement noise.

Optimizing iterative learning control of cyclic production processes with application to extruders

Abstract: Conventional and new methods for the control of cyclic processes are described and compared on the basis of their performance results achieved in an aluminum extruder plant. The thrust of the work lies in the area of iterative learning control systems. After a brief description of (linear) iterative learning control, the optimizing iterative learning control of cyclic processes is presented. In this method the control input is adjusted from cycle to cycle such that a prescribed quantitative performance index is made to take on an extremum. The results which the presented methods of cyclic control yield when applied to a simulation model of an aluminum extruder are compared with one another. Finally, results obtained in an actual industrial extruder plant are given. The new method yields an increase of production by 10% as compared to methods in current use.

Self-balancing thermal control device for integrated circuits

Abstract: A self-balancing temperature control device for an integrated circuit (IC) (12) includes a heat sink (14, 16) attached to the IC having thermomorphic fins or vanes (22). When the IC increases its heat output, the fins or vanes warm up and change their shape in a manner that increases the rate at which heat is removed from the IC.

Temperature control system for electronic devices

Abstract: An apparatus 10 for controlling a temperature of an electronic device 40 , comprising a temperature regulated surface 100 and an actuator 105 adapted to alternately pulse the temperature regulated surface 100 and electronic device 40 between thermally coupled and uncoupled positions, whereby a temperature of the electronic device 40 is controlled.

Temperature control method and structure for a battery pack

Abstract: Cylindrical battery modules (9) composed of a plurality of serially connected cells (7) and arranged in parallel and stacked in piles within a holder case (10) are cooled with a forced current of air supplied from the underside. The battery modules (9 a) located on the most upstream side of the air current are covered with film tubes (2), so as to prevent them from being cooled more than the other battery modules (9), thereby achieving uniformity in the temperatures of the battery modules. Temperature equalization is further improved by providing film tubes (2) to the several tiers of the battery modules such that the film tubes for covering upstream battery modules (9) have larger diameters than those for downstream battery modules.

A design perspective on thermal barrier coatings

Abstract: This article addresses the challenges for maximizing the benefit of thermal barrier coatings for turbine engine applications. The perspective is from the viewpoint of a customer, a turbine airfoil designer who is continuously challenged to increase the turbine inlet temperature capability for new products while maintaining cooling flow levels or even reducing them. This is a fundamental requirement for achieving increased engine thrust levels. Developing advanced material systems for the turbine flowpath airfoils, such as high-temperature nickel-base superalloys or thermal barrier coatings to insulate the metal airfoils from the hot flowpath environment, is one approach to solve this challenge. The second approach is to increase the cooling performance of the turbine airfoil, which enables increased flowpath temperatures and reduced cooling flow levels.