BSH Electrodomésticos (Spain)

Multiple-burner induction-heating cooking appliances are suitable for using multiple-output inverters. Some common approaches use several single-output inverters or a single-output inverter multiplexing the loads along the time periodically. By specifying a two-output series-resonant high-frequency inverter, a new inverter is obtained fulfilling the requirements. The synthesized converter can be considered as a two-output extension of a full-bridge topology. It allows the control of the two outputs, simultaneously and independently, up to their rated powers saving component count compared with the two-converter solution and providing a higher utilization of electronics. To verify theoretical predictions, the proposed converter is designed and tested experimentally in an induction-heating appliance prototype. A fixed-frequency control strategy is digitally implemented with good final performances for the application, including ZVS operation for active devices and a quick heating function. Although the work is focused on low-power induction heating, it can be probably useful for other power electronic applications.

In this paper, a comparison is performed between four inverter topologies commonly used in induction cookers. The considered topologies are the full-bridge inverter, the half-bridge inverter, and two single-switch inverters. All of them are designed for the same specifications and they are compared in aspects such as power device stresses, efficiency, frequency control and electromagnetic emissions.

We present a simple method to calculate the winding resistance of a litz-wire inductor in an induction cooking appliance, taking into account eddy-current losses, including conduction losses and proximity-effect losses. The method, which uses numerical calculation of the magnetic field, can be used to determine the optimum number of strands in the litz wire. The effects of the temperature on the winding total resistance are included in the calculation. We have built a prototype to verify the calculation method and its limitations. We consider the accuracy limits of the method.

Optimization of the efficiency of an induction heating application is essential in order to improve both reliability and performance. For this purpose, multistranded cables with litz structure are often used in induction heating applications. This paper presents an analysis and optimization of the efficiency of induction heating systems focusing on the optimal copper volume of the winding with respect to different constraints. The analysis is based on the concept of a one-strand one-turn coil, which captures the dissipative effects of an induction heating system and reduces the number of variables of the analysis. An expression for the efficiency of the induction heating system is derived. It is found that, with the geometry and the other parameters of the system fixed, efficiency depends on the copper volume of the windings. In order to use this result to optimize the efficiency of an application, volume restrictions, the packing factor and the window utilization factor are also considered. The optimum frequency for an induction heating system is also studied in this study. An experimental verification for both planar and solenoidal cases is also presented.

This paper presents a field-programmable gate array (FPGA) implementation of a digital circuit that measures in real time the output power of medium-frequency (25-50 kHz) induction-heated cooking appliances. The voltage and current are sensed using first-order sigma-delta (SigmaDelta) analog-to-digital converters. The power-measuring algorithm is very simple while maintaining good accuracy. The algorithm is developed using a hardware description language (VHDL). The digital circuit, the power converter, the signal conditioning circuits, and the SigmaDelta modulators are simulated all together using a mixed-signal (analog + digital) simulation tool. The algorithm error is obtained in simulation computing the average power using VHDL-Analog and Mixed-Signal Extension Language (VHDL-AMS), and the influence of different parameters is analyzed. Finally, the digital circuit is implemented in the FPGA, and the simulations are experimentally verified.

As one of the main aims of "Ambient Intelligence" is natural human interaction with the environment and one the most suitable is the home environment. Fagor has been working several years to develop a power-line network where all its household appliances, security sensors and actuators, heating systems and antiintrusion systems are connected and managed by a central controller named Maior-Domo. As a result of GENIO project, the user can dialog with his home and asks the services and functionalities he wants by talking as he was talking to a friend. The controller Maior-Domo has a human representation that the user can see and can interact with. When the user talks the Maior-Domo extracts the different commands from those vocal orders and controls the home devices. These orders are not specific commands that the user has to learn but natural speaking language without any need of learning. In the same way, any event or information from any device of the network is transmitted to the user by voice. In order to achieve a demonstrator of this Ambient Intelligence application, a real kitchen and sitting room have been built where the users can command the home talking naturally (in Spanish). Possible actions are: reading e-mails, programming the washing machine, checking the goods in the fridge, creating the shopping list, doing shopping with a PDA in the supermarket, activating the dishwasher, being guided on how to prepare a recipe for the oven checking if there are the needed goods to do it, listening some music stored at home, watching some photos, watching some selected video and so on. Every user has a wireless microphone in his/her shirt's pocket. This microphone captures his/her voice and all the sounds around him/her and sends them to a developed board which filters the voice frequency range from other sounds. From here the voice recognition system "understands" the pronounced sentence and process it. A quite extended number of sentences, called grammar, make up the possible dialogue between the person and the whole system. The user can address the whole system in different ways using a lot of expressions, talking naturally and spontaneously and dialoguing to the home. The defined grammar is so extended that almost the total speaker independence has been achieved.

Hydrophobic surfaces are of high interest to industry. While surface functionalization has attracted significant interest, from both industry and research, the durability of engineered surfaces remains a challenge, as wear and scratches deteriorate their functional response. In this work, a cost-effective combination of surface engineering processes on stainless steel was investigated. Low-temperature plasma surface alloying was applied to increase surface hardness from 172 to 305 HV. Then, near-infrared nanosecond laser patterning was deployed to fabricate channel-like patterns that enabled superhydrophobicity. Abrasion tests were carried out to examine the durability of such engineered surfaces during daily use. In particular, the evolution of surface topographies, chemical composition, and water contact angle with increasing abrasion cycles were studied. Hydrophobicity deteriorated progressively on both hardened and raw stainless steel samples, suggesting that the major contributing factor to hydrophobicity was the surface chemical composition. At the same time, samples with increased surface hardness exhibited a slower deterioration of their topographies when compared with nontreated surfaces. A conclusion is made about the durability of laser-textured hardened stainless steel surfaces produced by applying the proposed combined surface engineering approach.

This article presents an inductively coupled heating application, that is, a combination of wireless power transfer and induction heating. The addition of a secondary inductor with a resonant capacitor directly beneath and attached to the ferromagnetic load allows us to improve induction heating adaptation of loads of different sizes to the primary inductor, enhancing power distribution and extending load distance while avoiding increased power losses and stress on electronic components. The extended distance can be used to implement the seamless induction concept, where the typical ceramic glass is substituted by the kitchen surface itself. Finite-element analysis simulations are carried out to determine the suitability of each possible design, and a scoring system is applied to determine the optimal solution, bearing in mind the delivered power, power factor, power distribution, and efficiency. A near optimal design is chosen to develop as a prototype. The prototype is tested under working conditions up to 3680 W at several distances, validating the simulations' impedance parameters and verifying power distribution with a water boiling test and a dry test with a thermographic camera.

Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical composition, morphology, and roughness of surfaces (wettability), cleaning (remove contaminants), reducing internal stresses of metals (hardening, tempering), surface energy (polymers, metals), increasing the adhesion (hybrid joining, bioengineering) and decreasing the growth of pathogenic bacteria (bioengineering). This paper is a continuation and extension of our previous studies in laser-assisted texturing of surfaces. Three different patterns (crater array-type C, two ellipses at 90° overlapping with its mirror-type B and 3 concentric octagons-type A) were applied with a nanosecond pulsed laser (active medium Nd: Fiber Diode-pumped) on the surface of a ferritic stainless steel (AISI 430). Micro texturing the surface of a material can modify its wettability behavior. A hydrophobic surface (contact angle greater than 90°) was obtained with different variations depending on the parameters. The analysis performed in this research (surface roughness, wettability) is critical for assessing the surface functionality, characteristics and properties of the stainless steel surface after the LST process. The values of the surface roughness and the contact angle are directly proportional to the number of repetitions and inversely proportional to the speed. Recommendations for the use of different texturing pattern designs are also made.

Nowadays users of domestic induction cookers demand heating areas larger than traditional ones because they are able to heat larger pan diameters. These heating areas consist of several concentric planar windings which have to be fed. A possible solution is to replace the traditional single-output inverter topologies by multiple-output inverter topologies. Proposed is a topology for three concentric planar windings based on an electronic board of a domestic cooker and an adaptation board. The different configurations according to the pan diameter are detailed and some experimental results are presented. The proposed topology minimises the semiconductor stress of the devices.

The selection of a vessel by an induction-hob user has a significant impact on the performance of the appliance. Due to the induction heating physical phenomena, there exist many factors that modify the equivalent impedance of induction hobs and, consequently, the operational conditions of the inverter. In particular, the type of vessel, which is a sole decision of the user, strongly affects these parameters. Besides, the ferromagnetic properties of the different materials the vessels are made with, vary differently with the excitation level, and given that most of the domestic induction hobs are based on an ac-bus voltage arrangement, the excitation level continuously varies. The algorithm proposed in this work takes advantage of this fact to identify the equivalent impedance of the load and recognize the pot. This is accomplished through a phase-sensitive detector that was already proposed in the literature and the application of deep learning. Different convolutional neural networks are tested on an augmented experimental-based dataset and the proposed algorithm is implemented in an experimental prototype with a system-on-chip. The proposed implementation is presented as an effective and accurate method to characterize and discriminate between different pots that could enable further functionalities in new generations of induction hobs.

Polymer injection-molding is one of the most used manufacturing processes for the production of plastic products. Its electricity consumption highly influences its cost as well as its environmental impact. Reducing these factors is one of the challenges that material science and production engineering face today. However, there is currently a lack of data regarding electricity consumption values for injection-molding, which leads to significant errors due to the inherent high variability of injection-molding and its configurations. In this paper, an empirical model is proposed to better estimate the electricity consumption and the environmental impact of the injection-molding process. This empirical model was created after measuring the electricity consumption of a wide range of parts. It provides a method to estimate both electricity consumption and environmental impact, taking into account characteristics of both the molded parts and the molding machine. A case study of an induction cooktop housing is presented, showing adequate accuracy of the empirical model and the importance of proper machine selection to reduce cost, electricity consumption, and environmental impact.

In this paper, a method to improve efficiency in half-bridge series resonant inverter applied to domestic induction heating is presented. Low and medium output powers required for this application implies the use of higher switching frequencies, which leads to an efficiency decrease. Asymmetrical duty cycle (ADC) modulation scheme is proposed to improve efficiency due to its switching frequency reduction and absence of additional hardware requirements. Study methodology comprises, in a first step, a theoretical analysis of power balance as a function of control parameters: duty cycle and switching frequency. In addition, restrictions due to snubber and dead time, and variability of the induction loads have been considered. Afterwards, an efficiency analysis has been carried out to determine the optimum operation point. Switching and conduction losses have been calculated to examine global importance of each one for different switching devices. ADC modulation efficiency improvement is achieved by means of a switching frequency reduction, mainly at low-medium power range and low quality factor (Q) loads. The analytical results obtained with this study have been validated through an induction heating test-bench. A discrete 3-kW RL load has been designed to emulate a typical induction heating load. Then, a commercial induction heating inverter is used to evaluate ADC modulation scheme.

The wide variability of the load is the main problem of domestic induction-heating technology. The considered power control strategy should guarantee stability and regulation with a suitable response time and no overshoot independently of any perturbation or load variation. In addition to this, it has to ensure the operation under safety conditions. This paper is focused on the power control applied to one heating unit by means of continuous modulations. An inverse-based power controller is proposed for dealing with load uncertainties. The proposed power control combines different variable frequency pulsewidth modulation strategies (constant duty cycle, constant on-time, and constant off-time modulations) for reaching the target power level while minimizing the switching frequency. Finally, simulation and experimental results compared with other techniques in a prototype of an induction-heating system are presented in order to validate the proposed control strategy.

Litz wires with large number of strands are usually manufactured by twisting several bundles of a moderate number of strands. Apart from manufacturing advantages, this technique also provides extra characteristics as current balancing between strands and, consequently, power loss balancing and optimal use of cross sectional copper area. However, complex twisting configurations carry analysis, modeling and design problems which make choosing the parameters of a particular arrangement difficult. A complete 3D finite element model that explicitly includes the effect of twisting at several bundle levels is introduced. This model captures the twisting details and allows observing the actual current density in the strands at the different positions in the wire for both net driven current and induced current by an external field. The model is implemented by using the rigourous mathematical description of trajectories of strands and it is used to analyze the effect of several parameters as bundle levels, pitch and isolation between strands.

The equivalent load of an induction hob is strongly dependent on many parameters such as the switching frequency, the excitation level and the size, type, and material of the vessel. However, real-time methods with the ability to capture the variation of the load with the excitation level have not been proposed in the literature. This is an essential issue as most of the commercial induction hobs are based on an ac-bus voltage arrangement. This article proposes a method based on a phase-sensitive detector that offers an online tracking of the equivalent impedance for this type of arrangements. This algorithm enables advanced control functionalities such as clustering of vessels, material recognition, and premature detection of ferromagnetic saturation, among others. After simulation and experimental validation, the method is implemented into a prototype with a system-on-chip to verify its real-time behavior. The proposed approach is applied to different real-life situations that prove its great performance and applicability.

The usage of recycled polymers for industrial purposes arises as one of the most promising methods of reducing environmental impact and costs associated with scrapping parts. This paper presents a systematic study of the dimensional stability of a raw and 100% recycled polypropylene subjected to realistic environmental conditions occurring along its working life. The component studied is an internal part of an induction hob assembly. Industrial samples manufactured with both materials, in the same mold, and in the same injection machine, are subjected to ejection conditions, storage conditions (50 °C), and extreme performance conditions (80 °C). Induced dimensional changes are registered and analyzed using a coordinate measuring machine, and a tactile sensing probe. To verify the process capability of the samples manufacturing, Cp and Cpk values are calculated to evaluate the suitability of the recycled material as an alternative. Results conclude that, although the use of recycled material implies slight differences in terms of dimensional stability due to the changes induced in the polymer structure, these differences are not significant enough to affect the injection process capability. Therefore, recycling arises as one effective method to reduce both overruns associated with the consumption of raw polypropylene material and its environmental impact.

The influence of alloy composition on the environmental impact of the production of six aluminum casting alloys (Al Si12Cu1(Fe), Al Si5Mg, Al Si9Cu3Zn3Fe, Al Si10Mg(Fe), Al Si9Cu3(Fe)(Zn) and Al Si9) has been analyzed. In order to perform a more precise environmental impact calculation, Life Cycle Assessment (LCA) with ReCiPe Endpoint methodology has been used, with the EcoInvent v3 AlMg3 aluminum alloy dataset as a reference. This dataset has been updated with the material composition ranges of the mentioned alloys. The balanced, maximum and minimum environmental impact values have been obtained. In general, the overall impact of the studied aluminum alloys varies from 5.98 × 10−1 pts to 1.09 pts per kg, depending on the alloy composition. In the analysis of maximum and minimum environmental impact, the alloy that has the highest uncertainty is AlSi9Cu3(Fe)(Zn), with a range of ±9%. The elements that contribute the most to increase its impact are Copper and Tin. The environmental impact of a specific case, an LED luminaire housing made out of an Al Si12Cu1(Fe) cast alloy, has been studied, showing the importance of considering the composition. Significant differences with the standard datasets that are currently available in EcoInvent v3 have been found.

This study presents design guidelines for planar induction systems whose winding is considerably farther from its load than in usual arrangements. Optimum efficiency design is paramount for larger distances due to the magnetic field dispersion. To this end, a parameterised finite element model is used to ascertain the system's parameters in this new configuration. This model is used to test variations in frequency, inductor‐load distance and inductor diameter. From simulation results, efficiency, output power, power loss volumetric density and near field measurement predictions are obtained. Graphical representation of these results is used to determine the viability of each possible design, choosing one to develop a prototype. Moreover, a study was carried out with Pareto techniques to determine the effect of ferrite coverage and thickness, as well as its distance to the aluminium shielding on efficiency and near field predictions in order to develop a second prototype. The validity of the model is confirmed by experimental tests in small and operating signal regimes.

BACKGROUND: Exercise has been demonstrated as effective for the treatment of low back pain (LBP) in workers. OBJECTIVE: The purpose of this study was to investigate whether an exercise program adapted to the characteristics of the workplace is a useful supplement to general exercise recommendations in assembly line workers with chronic LBP. METHODS: Workers were randomly assigned to intervention group-adapted exercises plus general exercise recommendations (n = 10), and control group-general exercise recommendations (n = 8). Both received 8-week exercise program through a mobile application (APP) to manage the intervention. Outcome was based on lumbar disability (Oswestry Disability Index), interference and lumbar pain intensity (Brief Pain Inventory), and kinematic parameters. RESULTS: Significant differences were obtained for the intervention group in the "pain interference" variable, in the "mood" and "enjoyment" sub-variables, as well as in "flexion angle" variable. For the control group, significant differences occurred in the "pain intensity" variable. Adapted exercise plus general recommendations seems more effective than the general recommendations for the improvement of lumbar flexion. CONCLUSIONS: An adapted exercise program for assembly line workers with chronic LBP could be an effective treatment. Future studies with a larger sample size and with an exhaustive control of the exercise adherence are required to confirm the findings of this pilot study.