Showing papers on "Temperature control published in 2014"

Ev multi-mode thermal management system

Abstract: A multi-mode vehicle thermal management system is provided that allows efficient thermal communication between a refrigerant-based thermal control loop and three non-refrigerant-based thermal control loops, where one of the non-refrigerant-based loops provides temperature control over the vehicle's passenger cabin, a second of the non-refrigerant-based control loops is thermally coupled to the vehicle's battery system and the third of the non-refrigerant-based control circuits is thermally coupled to the vehicle's drive train. The refrigerant-based control loop may be operated either in a heating mode or a cooling mode and is coupled to the vehicle's HVAC system using a refrigerant-air heat exchanger, and to one or more of the non-refrigerant-based control loops using refrigerant-fluid heat exchangers. A valve assembly is used to couple and/or decouple the battery and drive train thermal control loops, thereby allowing these two thermal control loops to operate either in parallel or in series.

Effects of tool–workpiece interface temperature on weld quality and quality improvements through temperature control in friction stir welding

Abstract: A real-time wireless temperature measurement system has been developed and successfully implemented for closed-loop control of tool shoulder–workpiece interface temperature. The system employs two thermocouples in through holes and measures the shoulder and pin interface temperatures with an angular resolution as small as 10°. Both temperatures correlate with weld quality (mechanical testing and weld cross sections), e.g., all welds in 4.76-mm-thick 6061-T6 with an average shoulder interface temperature below 520 °C and an average pin interface temperature below 460 °C fail in the weld zone instead of the heat-affected zone, have unacceptable tensile strengths and in some cases voids. Similarly, welds with shoulder temperatures above the solidus temperature result in a degradation of the weld quality. It was found that a shoulder interface temperature of 533 °C results in the highest weld quality; hence, this temperature should be used as the setpoint temperature in the control system with a constant travel speed of 400 mm/min. The temperature measurement strategy was shown to be able to indicate welds with insufficient shoulder–workpiece contact, thus potentially identifying and preventing welds with detrimental weld quality due to lack of penetration. It was shown that backing plates of different thermal diffusivity change the heat flow out of the weld zone, hence weld temperature, and caused a measurable impact on the weld strength. By changing other process parameters, e.g., through a temperature control system, weld quality can be maintained in the presence of such changing thermal boundary conditions.

Nano-Kelvin thermometry and temperature control: Beyond the thermal noise limit

Abstract: We demonstrate thermometry with a resolution of 80nK/Hz using an isotropic crystalline whispering-gallery mode resonator based on a dichroic dual-mode technique. We simultaneously excite two modes that have a mode frequency ratio that is very close to two (±0.3ppm). The wavelength and temperature dependence of the refractive index means that the frequency difference between these modes is an ultrasensitive proxy of the resonator temperature. This approach to temperature sensing automatically suppresses sensitivity to thermal expansion and vibrationally induced changes of the resonator. We also demonstrate active suppression of temperature fluctuations in the resonator by controlling the intensity of the driving laser. The residual temperature fluctuations are shown to be below the limits set by fundamental thermodynamic fluctuations of the resonator material.

Thermoelectric Cooling for Power Electronics Circuits: Modeling and Active Temperature Control

Abstract: This paper discusses the modeling and application of thermoelectric cooling (TEC) in power electronics circuits. To investigate the benefits and challenges of using TEC, a temperature-dependent thermoelectric model which includes both power electronics circuits and TEC device is presented. With this model, both steady-state and small signal analyses can be carried out, and this paper is more focused on the steady-state part. For the steady-state analysis, the results have identified the allowed operation range which could be used as guidelines for system design. Also, with TEC device, the case temperature and junction temperature of power electronics switches can be dynamically controlled. Therefore, the switches' thermal cycling problem could be alleviated, and the switch lifetime and overall system reliability will be improved. Both simulation and experimental results are presented in this paper to verify the analysis.

Temperature Control using Fuzzy Logic

Abstract: The aim of the temperature control is to heat the system up todelimitated temperature, afterwardholdit at that temperature in insured manner. Fuzzy Logic Controller (FLC) is best way in which this type of precision control can be accomplished b y controller. During past twenty yearssignificant amount of research using fuzzy logichas done in this field of control of non-linear dynamical system. Here we have developed temperature control system using fuzzy logic.Control theory techniques are the root from which convention controllers are deducted . The desired response of the output can be guarante ed by the feedback controller.

Temperature Control of Industrial Coke Furnace Using Novel State Space Model Predictive Control

Abstract: This paper proposes an enhanced model predictive control (MPC) using a new state space structure for temperature control of an industrial coke furnace. The advantage of the proposed controller lies in the fact that its implementation only requires a simple step-response process model, whereas controller design can be based on state space formulation to improve temperature regulation. To ensure control performance effectiveness under model/process mismatch and uncertainties, model predictions and the cost function optimization are done on the basis of a new improved state space model. The proposed MPC is applied to an industrial coke furnace, where the outlet temperature in the radiation room is regulated. Simulation comparisons with traditional state space MPC are illustrated first. Then experimental results are shown in comparison with the original proportional-integral differential (PID) controller, demonstrating the effectiveness of the proposed methodology.

Building Temperature Control Based on Population Dynamics

Abstract: Temperature control in buildings is a dynamic resource allocation problem, which can be approached using nonlinear methods based on population dynamics (i.e., replicator dynamics). A mathematical model of the proposed control technique is shown, including a stability analysis using passivity concepts for an interconnection of a linear multivariable plant driven by a nonlinear control system. In order to illustrate our control strategy, some simulations are performed, and we compare our proposed technique with other control strategies in a model with a fixed structure. Finally, experimental results are shown in order to observe the performance of some of these strategies in a multizone temperature testbed.

Temperature control of robotic friction stir welding using the thermoelectric effect

Abstract: Friction stir welding (FSW) of non-linear joints receives an increasing interest from several industrial sectors like automotive, urban transport and aerospace. A force-controlled robot is particularly suitable for welding complex geometries in lightweight alloys. However, complex geometries including three-dimensional joints, non-constant thicknesses and heat sinks such as clamps cause varying heat dissipation in the welded product. This will lead to changes in the process temperature and hence an unstable FSW process with varying mechanical properties. Furthermore, overheating can lead to a meltdown, causing the tool to sink down into the workpiece. This paper describes a temperature controller that modifies the spindle speed to maintain a constant welding temperature. A newly developed temperature measurement method is used which is able to measure the average tool temperature without the need for thermocouples inside the tool. The method is used to control both the plunging and welding operation. The developments presented here are applied to a robotic FSW system and can be directly implemented in a production setting.

Motor Temperature Monitoring Based on Impedance Estimation at PWM Frequencies

Abstract: This paper proposes a noninvasive temperature measurement technique of indirect type, applicable in the permanent magnet synchronous motor (PMSM) drives. The motor temperature is required for protection and monitoring purposes, as well as for updating temperature-dependent control parameters. Direct measurement with dedicated sensors requires peripherals and cabling; hence, it is quite involved and often avoided. Temperature estimation based on test signal injection contributes to torque ripple and often relies on other motor parameters. A solution is proposed here, which makes the use of intrinsic pulse-width modulation excitation and does not use electrical or thermal parameters of the considered PMSM. The temperature of the stator winding is estimated from the motor input impedance ZIN(ω) calculated over the range of frequencies starting at and going well beyond fPWM. The paper includes analytical considerations, implementation details and experimental verification obtained with a 4.5-kW PMSM used in battery-supplied propulsion systems.

Simultaneous measurement of refractive index and temperature based on surface plasmon resonance sensors

Abstract: Although the surface Plasmon resonance (SPR) sensor is a mature technology, currently, the sample temperature needs to be carefully considered and controlled because SPR signals vary with temperature. This poses a large challenge in the applications where the sample temperature changes during measurement or an SPR sensor operates in different environmental temperatures. This paper proposes and experimentally demonstrates, for the first time to our knowledge, a solution to simultaneously measuring refractive index and temperature based on conventional SPR sensors, thus, not only requiring no temperature control/calibration during the measurement but also enabling SPR sensors for in-situ operations.

Control of temperature and energy consumption in buildings - a review.

Abstract: Building sector is one of the largest energy consumers in the world and currently it utilizes 40% of the total energy in the European Union. At the beginning of the article, energy crisis related to the buildings is defined with regard to occupant thermal comfort, energy savings and temperature control. Subsequently, a brief presentation of various types of building heating models available for control purposes is given. Afterward, different approaches used for controlling the building thermal comfort and the energy consumption are shown. These strategies are primarily, classical control, advanced control, intelligent control and hybrid control. The proposed survey also provides up-to-date applications of control techniques. The overview hence affords an insight into current control systems used for temperature and energy consumption in buildings. Further, it helps to have a comprehensive understanding about the variety of control techniques in the field of HVAC (Heating, Ventilation and Air conditioning) applications, at the same time delivering information for careful design of suitable controllers. Copyright © 2014 International Energy and Environment Foundation All rights reserved.

Wireless thermostat and system

Abstract: A secure wireless thermostat and system comprising the thermostat are described and taught. The temperature control unit replaces the traditional thermostat by attaching to the wall and using the existing wiring from the traditional thermostat. This temperature control unit has no display or programming buttons, rather a user interacts with the temperature control unit via electronic devices such as smart phones, laptop computers, and desktop computers. The settings of the system can be modified by the user from these access ports. If the user opts to interact with the system via a third party IP server, a local DHCP web server can be employed to store data safely and securely.

Dish-Stirling Solar Power Plants: Modeling, Analysis, and Control of Receiver Temperature

Abstract: A simplified adiabatic model of the Stirling engine is developed for the study of a grid-connected dish-Stirling solar-thermal power plant. The model relates the average values of the engine state variables and also takes into account the engine losses. As the engine is shown to exhibit nonminimum phase behavior, an improved temperature control scheme for the engine heat absorber is developed. By including the engine speed, pressure, and solar insolation limits into the analysis, a steady-state feasible operating regime of the solar-thermal power plant is obtained. A maximum solar energy harness is shown to be achievable through the variable speed operation of the power plant.

Reduced junction temperature control during low-voltage ride-through for single-phase photovoltaic inverters

Abstract: Future photovoltaic (PV) inverters are expected to comply with more stringent grid codes and reliability requirements, especially when a high penetration degree is reached, and also to lower the cost of energy. A junction temperature control concept is proposed in this study for the switching devices in a single-phase PV inverter in order to reduce the junction temperature stress, and thus to achieve improved reliability of a PV inverter. The thermal stresses of the switching devices are analysed during low-voltage ride-through operation with different levels of reactive power injection, allowing an optimal design of the proposed control scheme with controlled mean junction temperature and reduced junction temperature swings. The effectiveness of the control method in terms of both thermal performance and electrical performance is validated by the simulations and experiments, respectively. Both test results show that single-phase PV inverters with the proposed control approach not only can support the grid voltage recovery in low-voltage ride-through operation but also can improve the overall reliability with a reduced junction temperature.

Additive manufacturing heating control systems and methods

Abstract: An additive manufacturing system includes an additive manufacturing tool configured to supply a plurality of droplets to a part, a temperature control device configured to control a temperature of the part, and a controller configured to control the composition, formation, and application of each droplet to the plurality of droplets to the part independent from control of the temperature of the part via the temperature control device. The plurality of droplets is configured to build up the part. Each droplet of the plurality of droplets includes at least one metallic anchoring material.

Temperature control device, gas turbine, temperature control method, and program

Abstract: A temperature control device includes a temperature difference calculation unit that calculates a temperature difference between an inlet and an outlet of a boost compressor on the basis of a pressure ratio of the inlet and the outlet of the boost compressor and an IGV opening degree of the boost compressor, the boost compressor outputting cooling air obtained by cooling compressed air from a compressor to a cooling target; a temperature information calculation unit that calculates temperature information for feedback control for at least one of the inlet and the outlet of the boost compressor on the basis of the temperature difference between the inlet and the outlet of the boost compressor; and a control unit that performs feedback control by using the temperature information for feedback control such that at least one of an inlet temperature and an outlet temperature of the boost compressor approaches a setting value.

Multi-density, multi-property turbine component

Abstract: A method of forming a metal component having different regions containing different grain sizes and porosities is by additive manufacturing. The method includes spreading a layer of starting powder on a temperature controlled moveable platform in a heated chamber with atmosphere and temperature control. Selected areas of the powder are melted and solidified with a computer controlled focused energy beam. The cooled platform is then indexed down and the process repeated. The grain size of the melted and solidified region can be controlled by the cooling rate during solidification which, in turn is controlled by the temperature of the chamber and the temperature of the cooled moveable platform.