Closed-loop Temperature Control Research Articles

Analysis and Experimental Verification of the Demagnetization Vulnerability in Various PM Synchronous Machine Configurations for an EV Application

Safety is a critical feature for all passenger vehicles, making fail–safe operation of the traction drive system highly important. Increasing demands for traction drives that can operate in challenging environments over wide constant power speed ranges expose permanent magnet (PM) machines to conditions that can cause irreversible demagnetization of rotor magnets. In this paper, a comprehensive analysis of the demagnetization vulnerability in PM machines for an electric vehicle (EV) application is presented. The first half of the paper presents rotor demagnetization characteristics of several different PM machines to investigate the impact of different design configurations on demagnetization and to identify promising machine geometries that have higher demagnetization resistance. Experimental verification results of rotor demagnetization in an interior PM (IPM) machine are presented in the latter half of the paper. The experimental tests were carried out on a specially designed locked-rotor test setup combined with closed-loop magnet temperature control. Experimental results confirm that both local and global demagnetization damage can be accurately predicted by time-stepped finite element (FE) analysis.

Recoverable Autonomous Sonde for subglacial lakes exploration: heating control system design

AbstractDrilling and sampling are the most direct and effective methods available to study Antarctic subglacial lakes. Based on the Philberth probe, a Recoverable Autonomous Sonde (RECAS) allows for in situ lake water measurement and sampling, through the addition of an upper thermal tip and a cable recoiling mechanism. RECAS-200, a prototype of RECAS, has a drilling depth of 200 m, a surface supply voltage of 800 VAC and a downhole power of ~9.6 kW during drilling. In this study, a heating control system for RECAS-200 was designed. The system avoids the need for high-power step-down converters, by separating heating power from control power, thereby reducing the overall weight of the probe and avoiding the need to increase cable diameter. We also introduce a self-developed, small, solid-state, 800 VAC power regulator and a fuzzy PID temperature control algorithm. Their purpose was to manage the power adjustment of each heating element and to provide closed-loop temperature control of certain heating elements which can easily burn out due to overheating. Test results indicated that the proposed RECAS-200 heating control system met all our design specifications and could be easily assembled into the RECAS-200 probe.

Dynamic and Post-Dynamic Recrystallization of Haynes 282 below the Secondary Carbide Solvus

Thermomechanical processes, such as forging, are important steps during manufacturing of superalloy components. The microstructural development during processing, which controls the final component properties, is complex and depends on e.g., applied strain, strain rate and temperature. In this study, we investigate the effect of process parameters on the dynamic and post-dynamic recrystallization during hot compression of Ni-base superalloy Haynes 282. Specifically, we address the effect of deformation below the grain boundary carbide solvus temperature. During deformation, discontinuous and continuous dynamic recrystallization was observed at the grain boundaries, and particle-stimulated nucleation occurred at primary carbides. Strain rate was determined to be the governing factor controlling the recrystallization fraction for strain rates up to 0.5 s−1 above which adiabatic heating became the dominating factor. Careful examination of the temperature development during deformation showed that the response of the closed-loop temperature control system to adiabatic heating can have important effects on the interpretation of the observed behavior. During a 90 s post-deformation hold, grain growth and an increasing fraction of twin boundaries significantly changed the deformation-induced microstructure and texture. The microstructure developed during post-dynamic recrystallization was mainly controlled by the temperature and only weakly coupled to the prior deformation step.

Expanding the limits towards 'one-pot' DNA assembly and transformation on a rapid-prototype microfluidic device.

DNA assembly and transformation are crucial to the building process in synthetic biology. These steps are significant roadblocks when engineering increasingly complex biological systems. To address this, recent development of widespread 'biofoundry' facilities has employed automation equipment to expedite the synthetic biology workflow. Despite significant progress, there is a clear demand for lower-cost and smaller-footprint automation equipment. The field of microfluidics have emerged to provide automation capabilities to meet this demand. However, we still lack devices capable of building large multi-gene systems in a consolidated process. In response to this challenge, we have developed a digital microfluidic platform that performs "one-pot" Golden Gate DNA assembly of large plasmids and transformation of E coli. The system features a novel electrode geometry and modular design, which make these devices simple to fabricate and use, thus improving the accessibility of microfluidics. This device incorporates an impedance-based adaptive closed loop water replenishment system to compensate for droplet evaporation and maintain constant assembly reaction concentrations, which we found to be crucial to the DNA assembly efficiency. We also showcase a closed-loop temperature control system that generates precise thermodynamic profiles to optimize heat shock transformation. Moreover, we validated the system by assembling and transforming large and complex plasmids conferring a biosynthetic pathway, resulting in performance comparable to those of standard techniques. We propose that the methods described here will contribute to a new generation of accessible automation platforms aimed at speeding up the 'building' process, lowering reagent consumption and removing manual work from synthetic biology.

Closed-Loop Temperature Control Based on Fiber Bragg Grating Sensors for Laser Ablation of Hepatic Tissue.

Laser ablation (LA) of cancer is a minimally invasive technique based on targeted heat release. Controlling tissue temperature during LA is crucial to achieve the desired therapeutic effect in the organs while preserving the healthy tissue around. Here, we report the design and implementation of a real-time monitoring system performing closed-loop temperature control, based on fiber Bragg grating (FBG) spatial measurements. Highly dense FBG arrays (1.19 mm length, 0.01 mm edge-to-edge distance) were inscribed in polyimide-coated fibers using the femtosecond point-by-point writing technology to obtain the spatial resolution needed for accurate reconstruction of high-gradient temperature profiles during LA. The zone control strategy was implemented such that the temperature in the laser-irradiated area was maintained at specific set values (43 and 55 °C), in correspondence to specific radii (2 and 6 mm) of the targeted zone. The developed control system was assessed in terms of measured temperature maps during an ex vivo liver LA. Results suggest that the temperature-feedback system provides several advantages, including controlling the margins of the ablated zone and keeping the maximum temperature below the critical values. Our strategy and resulting analysis go beyond the state-of-the-art LA regulation techniques, encouraging further investigation in the identification of the optimal control-loop.

Concepts, Roadmaps and Challenges of Ovenized MEMS Gyroscopes: A Review

The MEMS gyroscope by means of oven control, or the so-called ovenized MEMS gyroscope, isolates the die from the external environment and utilizes a closed-loop temperature control system. It is thought to be important as it does not produce bias, scale factor drift made by thermal variations. Hence, a better temperature stability of the device is expected, which potentially benefits greatly the next generation of high-performance MEMS sensor. Herein, we attempt to provide a comprehensive review of many areas of the ovenized gyros, consisting of principle, key technology, the state-of-the-art results and suggestions. The thermal error mechanism and the importance of temperature control are introduced. The descriptions of the principles and characteristics of both on-chip and off-chip architectures are provided. To suppress heat dissipation at the package level, thermal resistance models based on conduction, convection, and radiation are established and analyzed. In terms of heating drive energy efficiency, comparisons have been made within VCCS (Voltage-Controlled Current Source), V-I (Voltage-to-Current) converters and PWM (Pulse Width Modulation), followed by the analysis of SSP (Single Set Point) and MSP (Multiple Set Point) algorithms. With regards the feedback control system, a systematic discussion on its common temperature detection methods, including CMOS PTAT (Proportional To Absolute Temperature), RTD (Resistance Temperature Detector) and TCF (Temperature Coefficient of Frequency) is presented. The control algorithms and limitations for the temperature control are also presented. At the end, we compared and discussed the most representative ovenized gyros to date, followed by suggestions to future development trends.

Laser polishing as a new post process for 3D-printed polymer parts

A process strategy – a quasi-top-hat scanning strategy with closed-loop temperature control – for laser polishing of additively manufactured polymer parts is developed to reduce the process to its two main process parameter, polishing temperature and melt duration. A study for SLS-printed PA12 results in an achievable roughness reduction from an initial roughness of Sa = 10.2 µm to Sa = 0.61 µm. Further investigations are performed for PP, TPU, ABS and PEEK.

Designing of Fuzzy rule based switching mechanism for IMC controller for temperature controlling process

A fuzzy rule based switching mechanism for IMC controller is reported here. The switching scheme is realized through online adjustment of the controller settings between smooth control and tight control methodologies based on nine fuzzy rules. Initial settings of IMC controller is done by SIMC [5] tuning. The tuning parameters of SIMC controller i.e. closed-loop time constant (λ) and integral time (τI) are modified depending on the instantaneous process behaviour instead of their fixed settings as with conventional IMC tuning. Thus, due to proposed switching, closed-loop time constant (λ) and integral time (τI) of the IMC controller gets varied instead of their fixed tuning. Superiority of the reported scheme is verified based on practical experimentation of a closed-loop temperature control process.

A novel power stability drive system of semiconductor Laser Diode for high-precision measurement

In view of the strict requirements of the current high-precision measurement system for stable output power of the semiconductor LD (Laser Diode), a semiconductor LD stable power drive and multi-closed-loop control system are proposed after analyzing the semiconductor laser’s P–I (Power–Current) characteristics and temperature characteristics. The system uses a microcontroller as the core control unit and realizes the stable power output control of the semiconductor laser by controlling the current, power and temperature parameters. In this system, first, the control structure model of the controlled object has been designed. Second, a controllable closed-loop constant current feedback drive circuit has been designed and a high-precision controllable constant current drive circuit of the semiconductor laser has been obtained. Furthermore, the control circuit has been designed based on the neural PI (Proportional-Integral) control model and realizes the short-term stable power output of the semiconductor LD. Finally, a closed-loop temperature control system is designed to ensure that the operating temperature of the semiconductor laser is relatively stable and a long-term stable power output is obtained. By designing the hardware and software of the control system and conducting long-term experiments in the laboratory, we found that the system can guarantee the output power within 1 W of PD (Proportional-Differential) LD, and its long-term power stability can reach 1%. This system has a certain reference significance in using semiconductor lasers for high-quality detection when there are stringent requirements for power.

Integration of World-to-Chip Interfaces with Digital Microfluidics for Bacterial Transformation and Enzymatic Assays.

Digital microfluidics (DMF) represents an alternative to the conventional microfluidic paradigm of transporting fluids in enclosed channels. One of the major benefits of DMF is that fluid motion and control is achieved without external pumps. The automation component of DMF have pushed the barriers of this "lab-on-chip" technology. However, integration with external components (i.e., "world-to-chip") interfaces have been a challenge. Two common "world-to-chip" challenges are (1) delivering biological samples to DMF devices and (2) accurately controlling temperatures on device. To address these challenges, this work describes two "world-to-chip" interface features that have been integrated on a DMF platform: a reagent delivery system and a thermal control apparatus. This platform enables a variety of biological or chemical experiments to be conducted on-chip while reducing manual intervention. Specifically, our platform increases reagent volumes available to device reservoirs volume by at least 50-fold eliminating the need to manually refill reservoirs while improving droplet dispensing reproducibility. In addition, we have integrated a closed-loop temperature control system that offers precise temperature control on-chip. To validate our "world-to-chip" interface, we have automated bacterial transformation and enzymatic assay protocols, showing that such a system enhances DMF performance. Overall, we propose that this system will improve biological experimentation which requires fluidic and temperature control integrated on DMF platforms.

Optical crystal temperature tuner based on feedforward-feedback compound control

To tune the output wavelength of the laser, the operating temperature of the optical crystal needs to be controlled precisely in a wide range. In this paper, a temperature tuning control method for optical crystals with high temperature control precision and large temperature control range based on semiconductor refrigerator (TEC) was studied. The operating characteristics of TEC,the thermal effects and heat transfer mechanisms of optical crystals were analyzed. A temperature-current double closed loop temperature control model was established. This temperature-current double closed loop control model takes control of both the electrical characteristic's variations of working TEC and the temperature variations of the optical crystal. To overcome the inherent hysteresis characteristic of feedback control, the feedforward compensation control based on the double closed loop control was introduced. The TEC driver module based on the ARM+FPGA architecture was designed to achieve the high-frequency and high-precision PWM drive control. In conclusion, an optical crystal temperature tuning system was completed. Experimental results show that the overall temperature control accuracy of this system is better than 0.002ºC and the system can quickly stabilize at any set point temperature in a wide temperature range of -30-130ºC, and it has good robustness to abnormal environment, which meets the requirements of tunable laser for temperature range and accuracy of optical crystal.

In Situ Joining of Unidirectional Tapes on Long Fiber Reinforced Thermoplastic Structures by Thermoplastic Automated Fiber Placement for Scientific Sounding Rocket Applications

Automated Fiber Placement allows the automated lay-up of tailored laminates in aerospace quality. For thermoplastic matrix materials, the use of closed-loop temperature control enables an in situ consolidation. This makes autoclave curing superfluous and increases the overall process efficiency. Scientific sounding rockets typically consist of several aluminum modules carrying the scientific payload. The design of a module includes a cylindrical outer shell and two load input rings with a defined assembly interface. Reducing the structural weight would allow higher payloads, higher apogees or reduced fuel consumption. A new manufacturing concept using the Thermoplastic Automated Fiber Placement (TP-AFP) process was developed to manufacture a lightweight composite module.This paper presents the developed concept and focuses on the characterization of an in situ joint of TP-AFP tapes on a long fiber reinforced thermoplastic (LFT) structure. This represents the joint of the cylindrical shell on the load input rings of the rocket module. The joint was characterized with single lap shear tests for two different sample extraction areas at room temperature and at elevated temperature on pre-treated and untreated LFT surface.The variations did not show significant effects on the resulting shear strength. The results were considered for the design of the composite module allowing a weight reduction of more than 40 % compared to the aluminum modules. The new module proved its airworthiness as part of the sounding rocket mission REXUS-23 in March 2019. Beyond sounding rockets, the concept of in situ bonded TP-AFP tapes on complex LFT structures has many potential applications within aerospace but also automotive structures.

Исследование температурного режима элементов конструкции вакуумной электропечи сопротивления методом структурного математического моделирования

The article demonstrates the importance of developing a structural mathematical model of a high-temperature vacuum electrical resistance furnace (ERF) for studying the thermal processes in it with determining the temperature of each furnace element, predicting the service life of heating elements, screens, and other furnace structural elements, selecting the temperature sensor installation place, and making relevant adjustment of the temperature control system. The commonly used model, in which the furnace is represented by a first-order inertial section, does not provide such possibility, because the furnace average temperature is calculated in that case. Therefore, it is necessary to construct a model based on the energy balance equations for macro elements (heater, each of the screens, loading, etc.) taking into account radiant heat transfer between the macro elements. A mathematical structural model of a Tamman vacuum high-temperature electric furnace equipped with a heater in the form of a coal or graphite pipe and thermal insulation in the form of graphite cylinders-screens has been developed and implemented in the Simulink software package. The thermal resistance of graphite screens thermal conductivity, which is commonly neglected in design calculations of widely used thin metal screens, was taken into account in simulating the thermal processes. The temperature operating conditions of individual structural elements (heaters, screens, etc.) are analyzed, both at constant power supply voltage of the heaters and in using a closed-loop temperature control system. The effect the temperature sensor installation place has on the automatic temperature control quality is shown. The advisability of using the developed model for adjusting the proportional-integral-differential controller to ensure the required control quality is substantiated.

Liquid Metal Magnetohydrodynamic Pump for Junction Temperature Control of Power Modules

Power modules are the most common components to fail in power converters that are employed in mass transportation systems, thus leading to high unscheduled maintenance cost. While operating, high junction temperature swings occur that result in high thermomechanical stress within the structure of the power module, reducing the lifetime of the module. Liquid metals as a cooling medium received so far little attention in the area of power semiconductor cooling, despite being able to remove high heat fluxes. This paper shows for the first time how liquid metal is used to reduce actively the junction temperature swing. A magnetohydrodynamic (MHD) pump has been designed for this purpose allowing active control of the flow rate of the liquid metal that impinges against the baseplate of the module. The pump has been 3-D printed and is attached directly to the power module. A closed-loop temperature control system is implemented, able to estimate the insulated-gate bipolar transistor's junction temperature, and thus, controls the MHD power. This paper presents simulation and experimental results showing reductions in the temperature swing over the full load cycle with 12 °C as the highest observed reduction rate. This paper also shows detailed designs of the MHD pump and the controller hardware.

Effects of laser heat treatment combined with ultrasonic impact treatment on the surface topography and hardness of carbon steel AISI 1045

The surface layers of medium-carbon steel AISI 1045 were hardened by laser heat treatment (LHT) and by ultrasonic impact treatment (UIT) applied separately and in different sequences. The advantages of the two latter combined laser-ultrasonic hardening and finishing methods (the LHT + UIT and UIT + LHT combined treatments) are also analyzed in this work. The laser transformation hardening process was implemented using a 1 kW solid-state fiber laser with scanning optics and a proportional integral derivative (PID) closed-loop temperature control. The ultrasonic strain hardening process was carried out by means of a 0.3 kW ultrasonic generator and an ultrasonic oscillatory system, which contained a piezoceramic transducer, step-like horn and the impact head with seven cylindrical pins. The single-path processes were studied. The separately applied LHT and UIT process were firstly analyzed using a response surface method (RSM) and the analysis of variance (ANOVA). The effects of the heating temperature (1050–1300 °C) and the specimen feed rate (40–140 mm/min) used at the LHT process on the features of the hardened zone and surface hardness/microhardness of subsurface layer were assessed. The effects of the vibration amplitude of ultrasonic horn (15–18 μm) and treatment duration (60–240 s) at UIT on the surface roughness/waviness and hardness were also investigated. The experimental plan is based on a miscellaneous design matrix method. The quadratic regression equations for predicting the studied output parameters were developed and the optimum regimes of the LHT and UIT processes were determined based on the highest surface hardness and minimum roughness/waviness. Then, the influences of the combined treatments on the surface topography and hardness were analyzed and compared to those of single LHT and single UIT processes. Results show that the combined treatments provide more than triple increase in the surface hardness in comparison with that of the initial state, as well as formation a regular microrelief with minimum surface roughness.

Wireless Temperature Sensing Using Permanent Magnets for Nonlinear Feedback Control of Exothermic Polymers

Epoxies and resins can require careful temperature sensing and control in order to monitor and prevent degradation. To sense the temperature inside a mold, it is desirable to utilize a small, wireless sensing element. In this paper, we describe a new architecture for wireless temperature sensing and closed-loop temperature control of exothermic polymers. This architecture is the first to utilize magnetic field estimates of the temperature of permanent magnets within a temperature feedback control loop. We further improve performance and applicability by demonstrating sensing performance at relevant temperatures, incorporating a cure estimator, and implementing a nonlinear temperature controller. This novel architecture enables unique experimental results featuring closed-loop control of an exothermic resin without any physical connection to the inside of the mold. In this paper, we describe each of the unique features of this approach, including magnetic field-based temperature sensing, extended Kalman filtering for cure state estimation, and nonlinear feedback control over time-varying temperature trajectories. We use experimental results to demonstrate how low-cost permanent magnets can provide wireless temperature sensing up to $\sim 90^{\circ }C$ . In addition, we use a polymer cure-control testbed to illustrate how internal temperature sensing can provide improved temperature control over both short and long time-scales. This wireless temperature sensing and control architecture holds value for a range of manufacturing applications.

Closed Loop Temperature Control System Design Using Conventional and Advanced Intelligent Controller

Requirement of energy demand growing rapidly around the world due to modern suburban life styles and tendency for indoor comfort. These energy stipulation leads to design of intelligent control strategies to make the system energy efficient. Design an efficient room heater to make it energy proficient using intelligent control is an attractive research topic today. This article proposed a design of temperature controller with the purpose to sense the temperature of a room and maintain it to a fixed desired value. Conventional Proportional Integral (PI) controller as well as modern Artificial Neural Network (ANN) based PI controller have been used as the control strategies when a model of PI controller based on ANN with Levenberg-Marquardt learning algorithm has been introduced in this article. The simulation report of projected design has been shown and it has been concluded that the proposed control strategy is very advantageous due to its small overshoot, fast response, and high precision. All designs and simulations have been done in Simulink of Matllab platform.

Paper-based resistive heater with accurate closed-loop temperature control for microfluidics paper-based analytical devices

Accurate temperature controlling system is essential for temperature-sensitive applications of microfluidics technology. In this paper, for the first time, we implemented a low-cost temperature controlling system on paper to be used in paper-based microfluidics. A resistive heater was fabricated by screen-printing of conductive electric paint on paper substrate. The temperature was measured by a non-contact temperature sensor to suppress the effect of contact sensors’ thermal mass on the measured temperature. By utilizing PID controller in a closed-loop system, the accuracy of temperature is below 0.22 °C which is suitable for biological temperature-sensitive applications. A microfluidics paper-based analytical device (µPAD) is fabricated by screen-printing on filter paper and attached to the heater to be used as device under test. The fabrication and implementation procedures of the whole system including the heater, the temperature controller and the µPAD are very low-cost, fast and simple. The operation of the fabricated heater and the temperature controlling system were validated by a temperature-sensitive colorimetric test of cholesterol.

Steam temperature control of essential oil extraction system using Fuzzy-Fopi controller

This research proposed a closed-loop temperature control using a self-tuning fuzzy fractional-order PI (FOPI) controller to overcome the problem. The controller will regulate the steam temperature at a desired level to protect the oil from excessive heat. Self capability of fuzzy rules was found to facilitate the tuning using only information about output error and rate of output error. The proposed controller was found to be more in terms of energy consumption and produce better response compared to self-tuning fuzzy PI. Essential oil quality assessment was also performed for citronella oil samples that were extracted at 85ºC and 100ºC (uncontrolled). Significant improvement had been observed in the sample extracted at 85ºC based on physical and chemical evaluations using refractive index measurement and GC-MS analysis.Keywords: fuzzy control; fractional-order PID; essential oil extraction; hydro-steam distillation.

Model assisted closed-loop control strategy for selective laser melting

Selective laser melting is a growing technology for the production of complex metal parts. However, the workpiece heat conduction differs for different points due to its geometry, which results in a varying melt pool temperature and a varying part quality. A desired closed-loop control of the melt pool temperature is currently missing, because the production machines have no suitable sensors or the slow measurement hinders the in-process control. For this reason, a novel control approach is presented and verified by a proof-of-concept experiment. The control consists of a model-based feedforward control using a finite element heat simulation in combination with a robust feedback control employing a pyroelectric sensor. Simulation and experimental results prove a reduction of the temperature deviation of up to 73 % compared to an open-loop approach for the tested demonstration geometry. The feedback control concept is further shown to be capable of achieving cycle durations <50 µs, which enables in-process control.