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Development of control systems for laser powder bed fusion

INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2023年第11-12期129卷 5493-5514页

作者： Taherkhani, Katayoon Cantzler, Gerd Eischer, Christopher Toyserkani, Ehsan Univ Waterloo Multiscale Addit Mfg Lab Waterloo ON Canada Univ Waterloo Dept Mech & Mechatron Engn Waterloo ON N2L 3G1 Canada EOS Krailling Germany

This article aims to highlight the development of an intermittent controller designed to compensate and rectify the lack of fusion (LoF) zones that are induced during the LPBF process. The initial step involved the usage of the self-organizing map (SOM) algorithm to identify the location of LoF defects. Subsequently, the identified defects undergo clustering through the K-means algorithm to form a matrix of cells on the build plate. The center of each cell that encompasses the defective area is then selected as the optimal position for increasing laser power during the subsequence printed layer. To identify the optimum laser power value, various artificial voids, mimicking actual defects, are embedded in the coupons. The capping layer that closes the artificial void is then fabricated with different laser powers to heal the underlying defects. Based on the optimum laser power and defect size, several controlling rules are defined to change the laser power in situ in the targeted cells located within the capping layer of defects. The change in laser power is transferred as a laser correction file (LCF) to the actuator via the Message Queuing Telemetry Transport (MQTT) broker. Finally, the performance of the controller is evaluated by designing and fabricating two new sets of experiments, including artificial and randomized defects. The results are validated by performing a micro CT scan, in which the density of defects is analyzed on parts produced with and without the controller. The results suggest that the use of the controller increased the density of the sample with randomized defects by up to 1%.

关键词： Additive manufacturing Laser powder bed fusion In-situ monitoring Quality assurance Lack of fusion Intermittent controller closed-loop controller

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Active closed-loop vortex-induced vibration control of an elastically mounted circular cylinder at low Reynolds number using feedback rotary oscillations

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ACTA MECHANICA 2018年第1期229卷 231-250页

作者： Hasheminejad, Seyyed M. Rabiee, Amir H. Bahrami, H. R. T. Iran Univ Sci & Technol Sch Mech Engn Ctr Excellence Expt Solid Mech & Dynam Acoust Res Lab Tehran *** Iran

An active rotary oscillation feedback control methodology is adopted to suppress the flow-induced transverse vibration (VIV) of an elastically supported impenetrable circular cylinder in a uniform low Reynolds number flow (). The coupled fluid-structure interaction is replicated by applying the moving mesh technique via a user-defined function (UDF) in the main code of a commercial CFD solver. The closed-loop VIV control action is realized by active forced rotational oscillations of the circular cylinder about its axis based on the feedback signal of the lift coefficient. This prevents the occurrence of resonance by shifting the vortex shedding frequency away from the natural oscillator frequency. Three different active closed-loop proportional controllers are implemented, and their superior performance in cylinder VIV suppression is demonstrated against that of a representative open-loop control system with pre-specified rotational oscillations. It is shown that, in comparison with the open-loop system, the selected closed-loop controller achieves a better cylinder VIV response suppression with a much lower control effort along with considerable reductions in the associated lift/drag coefficients. Furthermore, the closed-loop controller is very effective in a wide range of reduced velocities and does not need to find the "lock-on" forcing frequency for proper de-synchronization. Moreover, the imposed feedback cylinder rotary oscillation is found to considerably affect the spatial characteristics of the wake flow structure by changing the 2S-Coalescent wake pattern (C-2S-mode) of an uncontrolled cylinder into the classical von Karman vortex street (2S-mode), very similar to that of a stationary obstacle. Lastly, when the system is in the fully developed condition, the proportional controller can be complemented by a fuzzy logic inference system for intelligent tuning of gain parameter in order to suppress the impulsive upsurge observed in the cylinder force coeffici

关键词： proportional controller closed-loop controller Reasoning System vibration control LIFT COEFFICIENTS low Reynolds number circular cylinders feedback signal forcing frequency fuzzy logic system fuzzy inference system gain parameter

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Development and performance assessment of a DC electric variable-rate controller for use on grain drills

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COMPUTERS AND ELECTRONICS IN AGRICULTURE 2010年第1期73卷 56-65页

作者： Jafari, M. Hemmat, A. Sadeghi, M. Isfahan Univ Technol Coll Agr Dept Farm Machinery Esfahan *** Iran

Site-specific crop management is a technology that modulates the application rate of field inputs such as seeds, fertilizers, and herbicides based on the needs of each management zone within a field. There are two methods available for changing the seeding rate in fluted-feed-roll type seed drills: (1) changing the active feed-roll length and/or, (2) changing the seed meter drive shaft speed. A possible method to develop a variable-rate seeder is to add a controller to a conventional grain drill which can change the speed of the seed meter drive shaft on-the-go. This was explored in the present study with the following main objectives: (a) to design a DC electric variable-rate controller to change a grain drill from a uniform to a variable-rate seeder, and (b) to determine the response time of the system. A motor control circuit was designed which used the output signals of two encoders as feedback. The system was consisted of: (1) a DC motor with a fixed-ratio gearbox, (2) encoders for sensing the rotational speeds of the grain drill drive wheel and the motor, (3) a G PS receiver, (4) a pulse-with-modulation (PWM) DC motor controller, and (5) a laptop. Dynamic tests were conducted at application rates of 87.5(low) and 262.5 (high) kg ha(-1). Sigmoid equations were best fitted to the transition data from low-to-high and high-to-low seeding rates. Our findings showed that the response times of low-to-high and high-to-low transition rates were 7.4 and 5.2 s. respectively. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Seeder Metering mechanism closed-loop controller Precision farming

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closed-loop control of variable layer width for thin-walled parts in wire and arc additive manufacturing

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JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 2016年第0期233卷 100-106页

作者： Xiong, Jun Yin, Ziqiu Zhang, Weihua Southwest Jiaotong Univ Sch Mat Sci & Engn Chengdu 610031 Peoples R China Southwest Jiaotong Univ State Key Lab Tract Power 111Sect 1 North Second Ring Rd Chengdu 610031 Peoples R China

An intelligent single-neuron self-adjusting controller is proposed for variable layer width control in wire and arc additive manufacturing (WAAM). The travel speed is selected as the input control variable and the layer width is chosen as the output. The performance of the controller is validated by the disturbance of deposition current, inter-layer temperature, and given layer width. It is also evaluated through deposition of a 13-layered wall with variable layer width. The proposed controller is effective for increasing the process stability when the expected layer width ranges from 6 to 9 mm. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Additive manufacturing Wire and arc Variable layer width Thin-walled parts closed-loop controller

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closed-loop Spatial and Temporal Control of Cavitation Activity With Passive Acoustic Mapping

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IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 2019年第7期66卷 2022-2031页

作者： Patel, Arpit Schoen, Scott J., Jr. Arvanitis, Costas D. Georgia Inst Technol Sch Mech Engn Atlanta GA 30318 USA Georgia Inst Technol Dept Biomed Engn Atlanta GA 30318 USA

Ultrasonically actuated microbubble oscillations hold great promise for minimally invasive therapeutic interventions. However for their successful translation to the clinic, real-time methods to control the amplitude and type of micro-bubble oscillations (stable versus inertial acoustic cavitation) and ensure that cavitation occurs within the targeted region are needed. In this paper, we propose a real-time nonlinear state controller that uses specific frequency bands of the microbubble acoustic emissions (harmonic, ultra-harmonic, etc.) to control cavitation activity (observer states). To attain both spatial and temporal controls of cavitation activity with high signal-to-noise ratio (SNR), we implement a controller using fast frequency-selective passive acoustic mapping (PAM) based on the angular spectrum approach. The controller includes safety states based on the recorded broadband signal level and is able to reduce the sensing inaccuracy with the inclusion of multiple frequency bands. In its simplest implementation, the controller uses the peak intensity of the passive acoustic maps, reconstructed using the third harmonic (4.896 +/- 0.019 MHz) of the excitation frequency. Our results show that the proposed real-time nonlinear state controller-based PAM is able to reach the targeted level of observer state (harmonic emissions) in less than 6 s and remain within 10% of tolerance for the duration of the experiment (45 s). Similar response was observed using the acoustic emissions from single element passive cavitation detection, albeit with higher susceptibility to background noise and lack of spatial information. Importantly, the proposed PAM-based controller was able to control cavitation activity with spatial selectivity when cavitation existed simultaneously in multiple regions. The robustness of the controller is demonstrated using a range of controller parameters, multiple observer states concurrently (harmonic, ultra-harmonic, and broad-band), noise levels

关键词： Cavitation controller closed-loop controller passive acoustic mapping nonlinear state controller focused ultrasound image guided therapy

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Flying capacitor voltage balance and neutral point voltage regulation of PV array fed active neutral point clamped converter in real-time HIL

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IET POWER ELECTRONICS 2020年第13期13卷 2816-2823页

作者： Mishra, Nidhi Yadav, Shivam Kumar Singh, Bhim Padmanaban, Sanjeevikumar Blaabjerg, Frede IIT Delhi Dept Elect Engn New Delhi 110016 India Aalborg Univ Fac Sci & Engn Dept Energy Technol Aalborg Denmark

This study deals with a new control strategy for flying capacitor (FC) based multilevel converter, in order to attain the desired reference value for five-level output voltage in active neutral point clamped (ANPC) converter. The balancing of capacitor voltages is one of the crucial aspects of grid-tied photovoltaic (PV) fed ANPC converter. The accurate reference voltage for FC is required to experience minimum power pulsation and capacitor voltage imbalance. An offset injection-based FC voltage regulator is implemented to track the desired voltage reference for FC. A simple proportional-integral controller generates the offset signal, which is added to the sinusoidal modulating wave to eliminate the FC imbalance. Moreover, neutral point voltage (NPV) balancing is achieved with the help of DC component injection control. The DC-AC power transfer, FC balance, NPV balance and unity power factor operation are achieved simultaneously. The performance of the closed-loop controller for grid-tied PV-fed ANPC converter is analysed at constant and variable irradiances. The system is modelled in MATLAB/Simulink for offline simulation. Furthermore, offline simulation results are validated using real-time controller hardware in loop (HIL) test bench. Moreover, active power is injected into the AC grid seamlessly and results are found compliant with the IEEE 519 standard.

关键词： voltage control photovoltaic power systems PI control power factor power generation control power capacitors power grids closed loop systems real-time systems Matlab power system simulation DC-AC power convertors solar cell arrays hardware-in-the loop simulation grid-tied photovoltaic minimum power pulsation offset injection-based FC voltage regulator proportional-integral controller DC component injection control unity power factor operation closed-loop controller flying capacitor voltage balance neutral point voltage regulation multilevel converter PV array fed active neutral point clamped converter real-time controller hardware in loop test bench sinusoidal modulating wave DC-AC power transfer NPV balance MATLAB-Simulink model offline simulation IEEE 519 standard

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Lift-to-drag ratio and laminar flow control of a morphing laminar wing in a wind tunnel

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SMART MATERIALS AND STRUCTURES 2011年第3期20卷 035019-1-035019-13页

作者： Coutu, Daniel Brailovski, Vladimir Terriault, Patrick Mamou, Mahmoud Mebarki, Youssef Laurendeau, Eric Ecole Technol Super Montreal PQ H3C 1K3 Canada Natl Res Council Canada Inst Aerosp Res Ottawa ON K1A 0R6 Canada Bombardier Aerosp Dorval PQ H4S 1Y9 Canada

A new hardware-in-the-loop control strategy to enhance the aerodynamic performance of a two-dimensional morphing laminar wing prototype was developed and tested. The testing was performed in a wind tunnel under cruise flight flow conditions: Mach number ranging from 0.2 to 0.3 and angle of attack from -1 degrees to 0.5 degrees. For each set of flow conditions, the shape of the upper surface of the wing was modified using two independent shape memory alloy actuators. The wing shape was morphed in two sequential steps. The initial morphed shape was controlled using open-loop architecture and the results of an anterior aero-structural numerical optimization study. The final morphed shape was closed-loop controlled using either the wind tunnel balance or an infrared camera as hardware-in-the-loop to give an instantaneous lift-to-drag ratio (L/D) or a laminar flow extension (chi(tr)/c) over the upper surface of the prototype. In respect to the aerodynamic performance of the unactuated wing profile, the L/D gain varies from 10.6 to 15% for the closed-loop control strategy compared to 10.0 to 13.7% for the open-loop control strategy. Laminar flow extension gains, Delta chi(tr)/c, measured by infrared camera, were situated in the 29-33% range for both control strategies. However, the results obtained showed that the closed-loop controller could be hindered by the noise of the hardware-in-the-loop signal.

关键词： closed-loop controller control strategy Wings HARDWARE IN THE loop aerodynamic performance closed loop CONTROL laminar boundary layer wind tunnel apparatus wind tunnels LIFT TO DRAG RATIO image morphing

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closed loop controlled deposition of Ba_xSr_1-xTiO₃ thin films in spray flames

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SURFACE ENGINEERING 2003年第3期19卷 179-184页

作者： Vukasinovic, B Sundell, S Oljaca, M MicroCoating Technol Atlanta GA 30341 USA

Control logic was developed,for automated thin film deposition in the combustion chemical vapour deposition (CCVD) process. In situ film thickness and deposition temperature measurements were used as a feedback to control film thickness and optical properties through real-time adjustment of the deposition parameters. The closed loop controller was optimised for the deposition of barium-strontium-titanate (BaxSr1-xTiO3, BST) films on sapphire but it can be used for other coating/ substrate combinations. Besides enabling repeatable depositions of BST films with optimal thickness and optical properties for electronic applications, this control process proved that unique features of the Nanomiser atomiser can be implemented to tune the film deposition rate. Comparison of scanning electron microscopy cross-sections of epitaxial BST films on sapphire substrate with the predicted film thickness suggests that the closed loop controller can be used to control the thickness of the deposited film to within +/-2%.

关键词： sapphire substrate timing adjustment Control procedures thin films closed-loop controller film thickness Optical properties Films Sapphire deposite film

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Estimation of parameters for plasma glucose regulation in type-2 diabetics in presence of meal

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IET SYSTEMS BIOLOGY 2018年第1期12卷 18-25页

作者： Biswas, Prova Sutradhar, Ashoke Datta, Pallab Indian Inst Engn Sci & Technol Shibpur Ctr Healthcare Sci & Technol Howrah 711103 W Bengal India Swasthya Bhawan Dept Hlth & Family Welf Inst Pharm Jalpaiguri Jalpaiguri 735101 W Bengal India Indian Inst Engn Sci & Technol Shibpur Dept Elect Engn Howrah 711103 W Bengal India

In this study, the authors propose a methodology for the estimation of glucose masses in stomach (both in solid and liquid forms), intestine, plasma and tissue;insulin masses in portal vein, liver, plasma and interstitial fluid using only plasma glucose measurement. The proposed methodology fuses glucose-insulin homoeostasis model (in the presence of meal intake) and plasma glucose measurement with a Bayesian non-linear filter. Uncertainty of the model over individual variations has been incorporated by adding process noise to the homoeostasis model. The estimation is carried out over 24h for the healthy people as well as a type II diabetes mellitus patients. In simulation, the estimator follows the truth accurately for both the cases. Moreover, the performances of two non-linear filters, namely the unscented Kalman filter (KF) and cubature quadrature KF are compared in terms of root mean square error. The proposed methodology will be helpful in future to: (i) observe a patient's insulin-glucose profile, (ii) calculate drug dose for any hyperglycaemic patients and (iii) develop a closed-loop controller for automated insulin delivery system.

关键词： blood diseases biochemistry parameter estimation biological tissues liver Bayes methods nonlinear filters Kalman filters drugs drug delivery systems medical signal processing automated insulin delivery system closed-loop controller hyperglycaemic patients drug dose root mean square error cubature quadrature KF Kalman filter type II diabetes mellitus process noise Bayesian nonlinear filter glucose-insulin homoeostasis model interstitial fluid liver portal vein insulin mass biological tissues intestine stomach glucose mass meal intake type-2 diabetics plasma glucose regulation parameter estimation

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Self-balanced non-isolated hybrid modular DC-DC converter for medium-voltage DC grids

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IET GENERATION TRANSMISSION & DISTRIBUTION 2018年第15期12卷 3626-3636页

作者： Elserougi, Ahmed A. Massoud, Ahmed M. Abdelsalam, Ibrahim Ahmed, Shehab Qatar Univ Dept Elect Engn Doha Qatar Alexandria Univ Dept Elect Engn Alexandria Egypt Arab Acad Sci Technol & Maritime Transport Elect & Control Dept Cairo Egypt Texas A&M Univ Qatar Dept Elect & Comp Engn Doha Qatar

Here, a new bi-directional hybrid modular non-isolated DC-DC converter is proposed where it consists of a boost converter (BC) fed from the high-voltage (HV) side. At the BC output stage, a certain number of half bridge submodules (HB-SMs) is connected across the BC switch. During the turn-on period of BC switch, the HB-SMs are connected sequentially to the low-voltage (LV) side, which results in charging/discharging their capacitors from/into the LV side. While, during the turn-off period, the LV side is bypassed and the HB-SMs capacitors are connected in series across the BC output stage, which results in discharging/charging them into/from the HV side. The power flow is controlled in both directions by controlling the duty cycle. The proposed configuration provides self-balancing operation thanks to the sequential connection of HB-SMs capacitors, and it also provides the ability to operate with high conversion ratios. Illustration and analysis of the proposed converter and its closed-loop controller are presented. A full design of the values and ratings of the involved components are presented. Simulation study for a 2.5MW (25kV/10kV) DC-DC converter is presented. Finally, experimental results for a downscaled prototype are presented for validation.

关键词： DC-DC power convertors power grids closed loop systems load flow control power capacitors self-balanced nonisolated hybrid modular DC-DC converter medium-voltage DC grids bidirectional hybrid modular nonisolated DC-DC converter high-voltage side low duty cycle BC output stage half-bridge submodules BC switch low-voltage side HB-SMs capacitors power flow control self-balancing operation sequential connection high conversion ratios closed-loop controller power 2 5 MW voltage 25 kV voltage 10 kV

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