Showing papers on "Temperature control published in 2010"

Real-Time Temperature Compensation of MEMS Oscillators Using an Integrated Micro-Oven and a Phase-Locked Loop

Abstract: We present a new temperature compensation system for microresonator-based frequency references. It consists of a phase-locked loop (PLL) whose inputs are derived from two microresonators with different temperature coefficients of frequency. The resonators are suspended within an encapsulated cavity and are heated to a constant temperature by the PLL controller, thereby achieving active temperature compensation. We show repeated real-time measurements of three 1.2-MHz prototypes that achieve a frequency stability of ± 1 ppm from -20°C to +80°C, as well as a technique to reduce steady-state frequency errors to ±0.05 ppm using multipoint calibration.

System, method and apparatus for just-in-time conditioning using a thermostat

Abstract: Systems and methods for reducing the cycling time of a climate control system. For example, one or more of the exemplary systems can receive from a database a target time at which a structureis desired to reach a target temperature. In addition, the system acquires the temperature inside the structure and the temperature outside the structure at a time prior to the target time. The systems use a thermal characteristic of the structure and a performance characteristic of the climate control system, to determine the appropriate time prior to the target time at which the climate control system should turn on based at least in part on the structure, the climate control system, the inside temperature and the outside temperature. The systems then set a setpoint on a thermostatic controller to control the climate control system.

Heater block for a rapid thermal processing apparatus

Abstract: The present invention relates to a heater block for a rapid thermal processing apparatus, and more particularly, to a heater block in which heating lamps are densely arranged in a tessellation. The tessellation has a structure such that the plurality of heating lamps are arranged at right angles to form a zigzag line, and the thus-formed zigzagged line is repeated such that the zigzagged line is combined with the adjacent zigzagged line. According to the present invention, a temperature gradient caused by a void between heating lamps is prevented, and heating lamps are densely arranged to increase heat density for a heat radiation area as opposed to conventional heater blocks, thus achieving improved heat treatment efficiency using less energy. In addition, fully uniform temperature control is enabled, in terms of sector allocated temperature control, even when the area to be independently controlled is enlarged as opposed to conventional heater blocks, thereby simplifying the configuration of a temperature control circuit.

Temperature Control of the BTX Divided-Wall Column

Abstract: The control of a divided-wall column is more difficult than the control of a conventional two-column separation sequence for the separation of ternary mixtures because there is more interaction among control loops. In a previous paper, a control structure using four composition loops was shown to provide effective control of the purities of the three product streams and also achieve minimum energy consumption for both feed flow rate and feed composition disturbances. The numerical example studied the separation of benzene, toluene, and o-xylene. The four manipulated variables were reflux flow rate (R), side-stream flow rate (S), reboiler heat input (QR), and liquid split (βL) at the top of the wall. In this paper we explore the use of temperatures to avoid expensive and high-maintenance composition analyzers. Two types of temperature control structures are studied. In the first, three temperatures located in the main column and one temperature on the prefractionator side of the wall are used to adjust the...

Design of high torque and high speed leg module for high power humanoid

Abstract: The high power ability of humanoid is desired for application of nursing or running or jumping motions. Achievement of the actuator of light and powerful equivalent to humans is required. In this paper, we propose a method to extract inherent performance from motors by an active temperature control. The method safely improves the output of motors. The active temperature control is achieved by combining the estimation of an internal temperature of the motor with the forced cooling by liquid. We also developed high power motor drivers for the proposed method. An experiment of a high power joint test bench is shown. In this paper, we show a high power prototype biped robot for application of nursing, running or jumping motions. High power actuator system and robust internal body network are developed for high power robot. Basic demonstration experiments of high power motion are shown.

Mechanistic Modeling of Broth Temperature in Outdoor Photobioreactors

Abstract: This study presents the first mechanistic model describing broth temperature in column photobioreactors as a function of static (location, reactor geometry) and dynamic (light irradiance, air temperature, wind velocity) parameters. Based on a heat balance on the liquid phase the model predicted temperature in a pneumatically agitated column photobioreactor (1 m(2) illuminated area, 0.19 m internal diameter, 50 L gas-free cultivation broth) operated outdoor in Singapore to an accuracy of 2.4 °C at the 95% confidence interval over the entire data set used (104 measurements from 7 different batches). Solar radiation (0 to 200 W) and air convection (-30 to 50 W)were the main contributors to broth temperature change. The model predicted broth temperature above 40 °C will be reached during summer months in the same photobioreactor operated in California, a value well over the maximum temperature tolerated by most commercial algae species. Accordingly, 18,000 and 5500 GJ year(-1) ha(-1) of heat energy must be removed to maintain broth temperature at or below 25 and 35 °C, respectively, assuming a reactor density of one reactor per square meter. Clearly, the significant issue of temperature control must be addressed when evaluating the technical feasibility, costs, and sustainability of large-scale algae production.

Energy-efficient variable-flow liquid cooling in 3D stacked architectures

Abstract: Liquid cooling has emerged as a promising solution for addressing the elevated temperatures in 3D stacked architectures. In this work, we first propose a framework for detailed thermal modeling of the microchannels embedded between the tiers of the 3D system. In multicore systems, workload varies at runtime, and the system is generally not fully utilized. Thus, it is not energy-efficient to adjust the coolant flow rate based on the worst-case conditions, as this would cause an excess in pump power. For energy-efficient cooling, we propose a novel controller to adjust the liquid flow rate to meet the desired temperature and to minimize pump energy consumption. Our technique also includes a job scheduler, which balances the temperature across the system to maximize cooling efficiency and to improve reliability. Our method guarantees operating below the target temperature while reducing the cooling energy by up to 30%, and the overall energy by up to 12% in comparison to using the highest coolant flow rate.

Melt Pool Temperature Control for Laser Metal Deposition Processes—Part I: Online Temperature Control

Abstract: Melt pool temperature is of great importance to deposition quality in laser metal deposition processes. To control the melt pool temperature, an empirical process model describing the relationship between the temperature and process parameters (i.e., laser power, powder flow rate, and traverse speed) is established and verified experimentally. A general tracking controller using the internal model principle is then designed. To examine the controller performance, three sets of experiments tracking both constant and time-varying temperature references are conducted. The results show the melt pool temperature controller performs well in tracking both constant and time-varying temperature references even when process parameters vary significantly. However a multilayer deposition experiment illustrates that maintaining a constant melt pool temperature does not necessarily lead to uniform track morphology which is an important criteria for deposition quality. The reason is believed to be that different melt pool morphologies may have the same temperature depending on the dynamic balance of heat input and heat loss.

A nano-ampere current reference circuit and its temperature dependence control by using temperature characteristics of carrier mobilities

Abstract: We have developed a nano-ampere CMOS current reference circuit that is tolerant to threshold voltage variations. This paper describes the circuit and its temperature dependence control technique for ultra-low power LSIs. Because the generated current increases with temperature, we propose a temperature dependence control architecture for a reference current by using the different temperature characteristics of “electron” and “hole” mobilities. Experiment results demonstrated that the circuit can generate a temperature compensated reference current of 9.95 nA and that the temperature dependence of the output reference current can be controlled by using the different temperature dependences of electron and hole mobilities. The temperature dependence controllability was 8.57 pA/˚C·bit and its total current dissipation was 68.1 nA.

Method and apparatus of a self-configured, model-based adaptive, predictive controller for multi-zone regulation systems

Abstract: A control system simultaneously controls a multi zone process with a self-adaptive model predictive controller (MPC), such as temperature control within a plastic injection molding system. The controller is initialized with basic system information. A per-identification procedure determines a suggested system sampling rate, delays or "dead times" for each zone and initial system model matrix coefficients necessary for operation of the control predictions. The recursive least squares based system model update, control variable predictions and calculations of the control horizon values are preferably executed in real time by using matrix calculation basic functions implemented and optimized for being used in a S7 environment by a Siemens PLC. The number of predictions and the horizon of the control steps required to achieve the setpoint are significantly high to achieve smooth and robust control. Several matrix calculations, including an inverse matrix procedure performed at each sample pulse and for each individual zone determine the MPC gain matrices needed to bring the system with minimum control effort and variations to the final setpoint. Corrective signals, based on the predictive model and the minimization criteria explained above, are issued to adjust system heating/cooling outputs at the next sample time occurence, so as to bring the system to the desired set point. The process is repeated continuously at each sample pulse.

Vehicle battery temperature control system and method

Abstract: A vehicle battery temperature control system includes a battery (14), a housing (16), a heat exchanger (18) and a sensor (32). The battery (14) has a heat sink (20). The housing (16) has a chamber (24) that contains the battery (14) and saturated liquid coolant (26) that substantially immerses the heat sink (20) to receive the thermal energy to cause a phase change of the coolant (26) from a liquid to a vapor. The heat exchanger (18) removes thermal energy from the vapor to change the vapor to liquid, and returns the liquid to the chamber (24). Either a valve (38, 40) selectively conveying coolant (26) between the chamber (24) to an air-conditioning system or a heating device (52) is controlled based on a characteristic of the coolant (26) detected by the sensor (32) to remove or provide thermal energy to or from the coolant (26) based on a relationship between the characteristic of the coolant (26) and a threshold.

Feedback Thermal Control for Real-time Systems

Abstract: Thermal control is crucial to real-time systems as excessive processor temperature can cause system failure or unacceptable performance degradation due to hardware throttling. Real-time systems face significant challenges in thermal management as they must avoid processor overheating while still delivering desired real-time performance. Furthermore, many real-time systems must handle a broad range of uncertainties in system and environmental conditions. To address these challenges, this paper presents Thermal Control under Utilization Bound (TCUB), a novel thermal control algorithm specifically designed for real-time systems. TCUB employs a nested feedback loop that dynamically controls both processor temperature and CPU utilization through task rate adaptation. Rigorously modeled and designed based on control theory, TCUB can maintain both desired processor temperature and CPU utilization, thereby avoiding processor overheating and maintaining desired soft real-time performance. A salient feature of TCUB lies on its capability to handle a broad range of uncertainties in terms of processor power consumption, task execution times, ambient temperature, and unexpected thermal faults. The robustness of TCUB makes it particularly suitable for real-time embedded systems that must operate in highly unpredictable environments. The advantages of TCUB are demonstrated through extensive simulations under a broad range of system and environmental uncertainties.

Temperature Control in Spark Plasma Sintering: An FEM Approach

Abstract: Powder consolidation assisted by pulsed current and uniaxial pressure, namely, Spark Plasma Sintering (SPS), is increasingly popular. One limitation however lies in the difficulty of controlling the sample temperature during compaction. The aim of this work is to present a computational method for the assembly temperature based on the finite elements method (FEM). Computed temperatures have been compared with experimental data for three different dies filled with three materials with different electrical conductivities (TiAl, SiC, Al2O3). The results obtained are encouraging: the difference between computed and experimental values is less than 5%. This allows thinking about this FEM approach as a predictive tool for selecting the right control temperatures in the SPS machine.

PID Control of Heat Exchanger System

Abstract: exchanger system is widely used in chemical plants because it can sustain wide range of temperature and pressure. The main purpose of a heat exchanger system is to transfer heat from a hot fluid to a cooler fluid, so temperature control of outlet fluid is of prime importance. To control the temperature of outlet fluid of the heat exchanger system a conventional PID controller can be used. Due to inherent disadvantages of conventional control techniques, model based control technique is employed and an internal model based PID controller is developed to control the temperature of outlet fluid of the heat exchanger system. The designed controller regulates the temperature of the outgoing fluid to a desired set point in the shortest possible time irrespective of load and process disturbances, equipment saturation and nonlinearity. The developed internal model based PID controller has demonstrated 84% improvement in the overshoot and 44.6% improvement in settling time as compared to the classical controller.

A Temperature Compensation Circuit for Thermal Flow Sensors Operated in Constant-Temperature-Difference Mode

Abstract: This paper presents a new temperature compensation technique for thermal flow sensors that are operated in a constant-temperature-difference (CTD) mode by means of a simple analog circuit. The resistive heater of a thermal flow sensor is maintained at a constant temperature some tens of Kelvins above fluid temperature with the help of a Wheatstone bridge circuit. In case of a change in media temperature, an adjustment of the heater temperature is necessary; otherwise, the temperature difference falls/rises with respect to the temperature change, and the sensor output signal deviates from its calibration. Temperature compensation can be performed by the use of an additional resistive temperature sensor. The circuit design presented here includes a potentiometer that is capable of changing the resistance of the temperature sensor and its temperature coefficient of resistance (TCR) for an easy adjustment for temperature compensation. This gives the freedom to use any material such as platinum, aluminum, or, in our case, an alloy of tungsten and titanium (WTi) for the temperature sensor, regardless of its resistance value and TCR with respect to the heater of a thermal flow sensor.

Optical System for On-Line Monitoring and Temperature Control in Selective Laser Melting Technology

Abstract: A monitoring system is developed to visualize and to control the process of Selective Laser Melting (SLM) of metallic powder. The system is integrated with industrial PHENIX PM-100 machine. Visualization is carried out using LED illumination and CCD-camera; a home developed pyrometer is applied for monitoring of thermal phenomena in the zone of laser impact. Deviation of temperature from its optimal value is chosen as a criterion for the express method of quality control.

Power switch temperature control device and method

Abstract: An embodiment method for power switch temperature control comprises monitoring a power transistor for a delta-temperature fault, and monitoring the power transistor for an over-temperature fault. If a delta-temperature fault is detected, then the power transistor is commanded to turn off. If an over-temperature fault is detected, then the power transistor is commanded to turn off, and delta-temperature hysteresis cycling is disabled.

A Smart Multiple-Loop Automotive Cooling System—Model, Control, and Experimental Study

Abstract: The integration of computer-controlled electro-mechanical components in ground vehicle cooling systems can improve coolant temperature regulation and servomotor power consumption. Advanced thermal management systems for internal combustion engines can better regulate the combustion process by harmoniously controlling the cooling system's actuators to obtain desired thermal conditions in a power-efficient manner. In this paper, a comprehensive nonlinear control architecture is proposed for transient temperature tracking in multiple cooling circuits, which builds on single-loop studies. An experimental engine and transmission cooling system have been assembled that feature a variable-position smart thermostat valve, two variable-speed electric pumps, variable-speed electric radiator fan, engine block, transmission, radiator, steam-based heat exchanger, and sensors. Representative experimental results are discussed to demonstrate the functionality of the multiloop thermal management system under normal and elevated ambient temperatures. The presented results clearly show that the proposed robust controller-based thermal management system can accurately track prescribed engine and transmission temperature profiles.

Boundary Observer for Output-Feedback Stabilization of Thermal-Fluid Convection Loop

Abstract: In this paper, we consider a 2-D model of thermal fluid convection that exhibits the prototypical Rayleigh-Bernard convective instability. The fluid is enclosed between two cylinders, heated from above, and cooled from below, which makes its motion unstable for a large enough Rayleigh number. We design an stabilizing output feedback boundary control law for a realistic collocated setup, with actuation and measurements located at the outer boundary. Actuation is through rotation (direct velocity actuation) and heat flux (heating or cooling) of the outer cylinder, while measurements of friction and temperature are obtained at the same boundary. Though only a linearized version of the plant is considered in the design, an extensive closed loop simulation study of the nonlinear model shows that our design works for reasonably large initial conditions. A highly accurate approximation to the control kernels and observer output injection gains is found in closed form.

Automatic bread maker

Abstract: In an automatic bread maker, after the temperature of temperature control means (7) reaches a predetermined temperature, the rate of energization of a heater (2) is fixed by control means (14), and by doing so, bread, having a predetermined baking color, can be stably prepared.