Low-cost Digital Controller Research Articles

An Experimental Set-up Involving Low-cost Digital Controller to Study the Magnetizing Inrush Current in a Transformer using Point-on-Wave Switching Technique

Abstract Generally in under-graduate studies, magnetizing inrush current (MIC) is discussed theoretically without giving much practical exposure. This paper presents the development of a low cost experimental set-up using a digital controller to study the MIC and the different parameters which can affect the same. This also helps to show how the inrush current can be minimized. This set-up also provides a hands-on experience of MIC and its control in under-graduate study, which can help an upcoming practitioner in industry as well as in further research. This paper presents a brief description of MIC, followed by a short analysis. Here, a pair of anti-parallel thyristors are connected in series with the primary winding of a single-phase power transformer. The turningon instant of this switch, with respect to the zero-crossing instant of the input supply voltage, may be adjusted through a firmware, in a PIC18F4620 from Microchip Technology microcontroller development board from Microchip Technology to control the transformer energisation instant. The firmware is developed in MPLABX-IDE from Microchip Technology, and the scheme is verified via simulations in Proteus simulation software. A suitable circuit to support the microcontroller development board to achieve the above function is designed and fabricated.

Area, Delay, and Energy-Efficient Full Dadda Multiplier

The Dadda algorithm is a parallel structured multiplier, which is quite faster as compared to array multipliers, i.e., Booth, Braun, Baugh-Wooley, etc. However, it consumes more power and needs a larger number of gates for hardware implementation. In this paper, a modified-Dadda algorithm-based multiplier is designed using a proposed half-adder-based carry-select adder with a binary to excess-1 converter and an improved ripple-carry adder (RCA). The proposed design is simulated in different technologies, i.e., Taiwan Semiconductor Manufacturing Company (TSMC) 50[Formula: see text]nm, 90[Formula: see text]nm, and 120[Formula: see text]nm, and on different GHz frequencies, i.e., 0.5, 1, 2, and 3.33[Formula: see text]GHz. Specifically, the 4-bit circuit of the proposed design in TSMC’s 50[Formula: see text]nm technology consumes 25[Formula: see text]uW of power at 3.33[Formula: see text]GHz with 76[Formula: see text]ps of delay. The simulation results reveal that the design is faster, more power-energy-efficient, and requires a smaller number of transistors for implementation as compared to some closely related works. The proposed design can be a promising candidate for low-power and low-cost digital controllers. In the end, the design has been compared with recent relevant works in the literature.

A Low-Cost Control Architecture for Buck Converter Fed VSI Based BLDC Motor Drive

In this paper, a novel low-cost digital controller to drive a buck converter fed voltage source inverter (VSI) based brushless DC (BLDC) machine has been proposed. This controller is designed to be implemented solely in digital platforms and has multiple numbers of predefined discrete duty ratios. In conjunction with buck converter fed VSI, the controller is beneficial to enhance the speed and resultant torque profile of BLDC motor drive as compared to conventional bang-bang or on-off controller. The controller also incorporates a current limiter to avoid the over-current loading of the motor. The sampling time and the design of the current limiter are mathematically derived in the paper. The working efficiency of the developed controller for the BLDC motor drive has been examined for various vital and steady-state conditions. The speed ripples, settling time, tolerance to the commanded speed, and load variations are validated and presented in this paper. The proposed controller has been performed and implemented in the field-programmable gate array platform and compared to generic pre-existing controllers to validate the cost-effectiveness of the controller.

Experimental testing of a real aggregator system performing rigorous optimal control of electrical and thermal storage

This paper provides an experimentally validated optimal control approach based on a Hamilton–Jacobi–Bellman (HJB) model for optimising aggregated distributed energy resources across multiple energy carriers. The research incorporates nonlinear effects arising from storage degradation, conversion efficiency and self-discharge as well as multiple energy carrier storage. A semi-Lagrangian HJB solver was implemented on low-cost digital controllers, and integrated into a real fully functional cloud-based aggregation platform. The computational cost is kept at a minimum, enabling on-line computations on the low-cost controller, while maintaining a rigorous proof of convergence to the theoretical value function of the nonlinear, non-convex optimal control problem.The controller links into a distributed optimal control platform that is using local as well as cloud-based information and performs all the computation and decision-making locally. The distributed controllers were tested and validated on site with an electrical and a thermal storage device. Experimental results confirm that the framework is practical, accommodates nonlinear effects and inaccurate external forecasts, has a small computational cost, is robust and can deliver significant cost benefits to the stakeholders.

Fast Hardware Approach to Determining Mutual Coupling of Series–Series-Compensated Wireless Power Transfer Systems With Active Rectifiers

Maximum energy efficiency tracking of series–series-compensated wireless power transfer systems with active rectifiers require the information of mutual coupling coefficient or correlated variables, which are conventionally monitored based on the feedback signals from the receivers to the transmitters via a wireless communication system. In this article, a very fast hardware-based front-end monitoring strategy is proposed to determine the mutual coupling coefficient of the system within typically 62 ms without any wireless communication system. Compared to existing mathematical model-based methods, the proposed strategy is much faster and more cost-effective by using fewer sensors and simpler equations. The proposed method can therefore be implemented in low-cost digital controllers. Importantly, the parameter values of the transmitter and receiver resonators are not required by the proposed method. Both simulation and experimental results are included to validate the high accuracy and fast speed of the proposed monitoring strategy to monitor the coupling coefficient. Comparative results among the proposed and existing monitoring strategies are also presented.

Decomposition-Based New Space Vector Modulation Algorithm for Three-Level Inverter with Various ADSVPWM Strategies

The three-level inverter is extensively preferred in medium-voltage industrial applications over the conventional inverter due to its benefits. The performance of inverter is better when the space vector modulation (SVM) approach is preferred. However, the implementation of conventional SVM approach is more complex. In this paper, a decomposition-based new SVM algorithm for three-level inverter is proposed to reduce computational complexity and implementation time using a low-cost digital controller. Initially, the performance of the proposed SVM algorithm is studied through MATLAB simulation using the conventional switching sequence 0127. Further enhancing the performance, the proposed algorithm is implemented with various advanced discontinuous SVPWM strategies using the advanced switching sequences of 1012–2721 and 0121–7212. The no-load motor current THD and switching loss analysis for ADSVPWM and conventional SVPWM strategies at different modulation indices are presented is this paper for a comparison point of view. The no load motor current THD results obtained through simulation are validated experimentally by implementing the proposed algorithm on real-time interface tool through dSPACE, which is used to control constant V/F-controlled three-level inverter-fed induction motor. Further to show the effectiveness of the proposed technique, the experimental investigation is done on induction motor at loaded condition and the results are presented.

Digital Implementation of Adaptive Synchronous Rectifier (SR) Driving Scheme for High-Frequency LLC Converters With Microcontroller

Synchronous rectifiers (SRs) are important for high-output-current LLC converters in order to reduce the secondary conduction loss. Conventional SR driving schemes are not suitable for high-frequency LLC converters: the analog driving schemes will lose a large portion of duty cycle due to SR parasitic inductance; and the digital driving schemes will require a much higher cost digital controllers in high-frequency operation. In this paper, a digital implementation of adaptive SR driving scheme for high-frequency LLC converters with cost-effective microcontroller is proposed. The proposed SR driving scheme senses SR drain–source voltage in order to detect body diode conduction, and tune the SR on-time every several switching cycles using ripple (asynchronous) counter to minimize body diode conduction. The proposed digital implementation has a simple control scheme, requires only low-cost digital controllers and minimizes controller resources utilization. More importantly, to cooperate with the closed-loop control, adaptive SR driving and closed-loop control are executed synchronously and SR on-time is modified accordingly during fast transient response to guarantee safe operation. With these techniques, the proposed adaptive SR driving can be embedded into the digital controllers with little extra cost. Experimental results are demonstrated on a 500-kHz 1-kW 400 V/12 V LLC converter with a 60-MHz microcontroller and a ripple counter.

Digital Position Control Strategy of Traveling-wave Ultrasonic Motors

Since a conventional controller is continuous one, control period is normally set for a long time. When applying that controller for a travelling-wave ultrasonic motor whose parameters and performance are time-varying as a result of increasing temperature and operating condition, it is consequently resulted in degradation of the control performance. In this paper, a digital control algorithm is proposed for position control of the motors to shorten the long control period to maintain the stability of the motor performance. The proposed controller is digitally implemented by a SH7125 microcomputer utilizing a high-performance embedded workshop. The state quantities such as acceleration, speed and position, which are necessary for digital implementation, are provided by a rotary encoder. However, the optical encoder causes quantization errors in the speed information. To overcome the problem, a digital Variable Structure System (VSS) observer is also included to estimate the state quantities. The control input will be calculated after comparing the measured values and the estimated values given by the VSS observer. In short, a small, low cost and fast responsive digital controller is designed, based on a digital VSS observer, by using the SH7125 microcomputer. Effectiveness and reliability of the proposed digital controller are experimentally verified.

Dual Mode Controller-Based Solar Photovoltaic Simulator for True PV Characteristics

Integration of solar photovoltaic (PV) panels with existing utilities requires effectively controlled converters. While developing and testing such converters, it is difficult to test them with actually installed PV panels owing to unavailability of practical onsite conditions for all the time. For such cases, PV simulators are preferred, which are required to exhibit PV system behavior under working conditions without the use of real outdoor installation. This reduces the time and cost of experimentation. In this paper, a real-time PV simulator based on a dc-dc buck converter is investigated to obtain true PV characteristics. The practical difficulty with PV simulators is that they often get oscillations in the constant current region or constant voltage region of PV characteristics, particularly when the controller is designed using a low-cost digital controller. This paper introduces a novel hysteresis controller to ensure effective operation in both these regions. This dual control strategy ensures effective control in both regions and provides smooth trajectories as per mathematical model or lookup table to mimic any PV characteristics under various temperatures and insolations with the use of the low-cost digital controller. The hardware prototype is constructed with the digital signal controller to demonstrate the efficacy of the proposed simulator.

Hysteretic Transition Method for Avoiding the Dead-Zone Effect and Subharmonics in a Noninverting Buck–Boost Converter

A new hysteresis window method is proposed as a solution for avoiding the operational dead zone that exists at the transition between buck and boost operating modes in all noninverting buck-boost converters. In addition, this method also eliminates the discontinuities in the converter's steady-state output voltage transfer characteristic, which is a function of the duty cycle. The converter's output voltage function is surjective and, therefore, smooth mode transitions are achieved. The negative effects of operating within the dead zone are shown by the presence of subharmonics in the output voltage, increased output voltage ripple, poor regulation, and the instability of the converter during the transition between buck and boost operating modes. The dead-zone avoidance technique proposed in this paper eliminates all these issues while at the same time ensures highly efficient operation of the converter. An additional advantage of the technique is its simplicity, which allows for implementation into low-cost digital signal controllers, as well as into analog control circuits. The advantageous features of the proposed approach were evaluated on the basis of comparisons with three other dead-zone avoidance approaches and the initial case, which does not utilize any dead-zone avoidance technique. All the experiments were carried out on a purpose-built prototype of a noninverting buck-boost converter with magnetically coupled inductors.

A Low-Complexity Dual-Voltage-Loop Digital Control Architecture With Dynamically Varying Voltage and Current References

In this paper, a low-complexity dual-voltage-loop digital control architecture is presented for voltage regulators (VRs), delivering power to processors. The proposed digital control architecture uses low speed and less complex digital-to-analog converters instead of high-speed analog-to-digital converters, thus significantly reducing the system complexity and cost. In this control architecture, there are two voltage loops, and the voltage reference is dynamically generated to selectively track one of them, as compared to other control methods where the output voltage tracks the voltage reference. Moreover, a straightforward control law is used, which does not require any compensator, making the proposed digital architecture simple and easy to implement. The dual-voltage-loop architecture breaks dependence between the system transient response and the system control bandwidth. One voltage loop is designed for the stable system operation, and the other is dedicated for the load transient response. Thus, the digital controller can be designed in such a way that the VR operates at a relatively low switching frequency to reduce power losses, and at the same time, it is also able to provide fast transient response. The proposed small signal model reveals that the inner current loop is analog and the voltage loop is digital. The proposed controller thus can benefit from both: having valuable features of digital control but without limitations such as limit cycle, which is eliminated by the inherent dithering characteristic. Theoretical, simulation and experimental results prove the effective operation and excellent dynamic performance of the low-complexity digital controller, thus making it a valuable candidate for a high-volume, low-cost digital controller for processors' VRs.

Power Factor Correction Without Current Sensor Based on Digital Current Rebuilding

A new digital control technique for power factor (PF) correction is presented. The main novelty of the method is that there is no current sensor. Instead, the input current is digitally rebuilt, using the estimated input current in the current loop. The circuit measures the input and output voltage by means of low cost <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ad hoc</i> analog-to-digital converters (ADCs). Taking advantage of the slow dynamic behavior of these voltages, almost completely digital ADCs have been designed, leaving only a comparator and an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> filter in the analog part. Avoiding measuring current can provide a significant advantage compared to analog controllers and this also helps to reduce the total cost. The ultimate objective is to obtain a low-cost digital controller that can be easily integrated as an intellectual property (IP) block into a field-programmable gate array, or an application-specific integrated circuit. The experimental results show a reasonably high PF, despite not measuring the input current, and therefore the feasibility of the method.

Quasi-Synchronous Microcontroller-Based Highly Accurate Digital Sampling of AC Signals

An easy-to-use and low-cost quasi-synchronous multichannel digital sampler controller to aid routine laboratory ac measurements by digital sampling is described. Using a single digital sampling voltmeter, accurate measurements of ac quantities can easily be done with uncertainties of a few microvolts per volt. Measurement results and consistent uncertainty calculations are described

Sensorless direct field-oriented control of three-phase induction motors based on "Sliding Mode" for washing-machine drive applications

Sensorless direct field-oriented (SDFO) control of three-phase induction motors based on "sliding mode" has been studied and applied to domestic washing-machine drives. In this paper, three related techniques, sliding-mode flux observer, sliding-mode speed controller, and direct rotor-speed estimator are presented for the application of SDFO "sliding mode" in induction-motor control system. Specifically, the investigations focus on how improving speed regulation, system robustness, and some special technical issues in washing-machine drives. The complete control schemes have been developed and implemented in a low-cost digital signal processor-based electronic controller. Through a variety of system performance validation tests, it has been proved that the developed SDFO control not only achieves satisfied steady as well as a dynamic performance, but also is robust for washing-machine driving applications.

Feedforward current control of boost single-phase PFC converters

This paper presents the theory and application of feedforward current control for boost single-phase ac-dc converters with power factor correction. The proposed feedforward signal involves the instantaneous line voltage and the derivative of the reference current. The new control method is compared to existing feedback and feedforward control methods and is shown to significantly reduce input current harmonic distortion, particularly for applications where the current loop crossover frequency is relatively low compared to the line frequency. Implementation of the proposed control using analog devices and the associated issues, such as performance sensitivity to parameter variation and uncertainties, are presented. Analysis results are complemented by numerical simulation and experimental results from a prototype converter. Targeted applications of the proposed method are airborne systems where the line frequency is high, as well as low-cost digital control for terrestrial 50-60-Hz systems where the current loop crossover frequency is limited by the speed of the digital controller.

A Low-Cost Digital Controller for a Switching DC Converter With Improved Voltage Regulation

A new control algorithm with improved regulation is presented for a switching dc buck converter. The controller is realized with hardware description language (HDL) and can be implemented in any process. The controller uses four decision levels, combines pulse frequency modulation (PFM), pulse width modulation (PWM), and uses dithering for improved regulation. The controller is prototyped on a field programmable gate array (FPGA) and experimental results show good performance over input and load disturbances. Importantly, the controller does not require high resolution analog-to-digital conversion for signal processing, and also does not require fast digital clocking. This controller has significant potential to be widely used in industrial applications where cost and design time are of great concern.

Teaching Digital Control Using a Low-Cost Microcontroller-Based Temperature Control Kit

The design of a low-cost digital temperature control kit is described. The system enables the students to implement various control strategies using a microcontroller. The kit is intended to be helpful in a control laboratory as a complement to the digital control system theory taught to undergraduate students.

Counter-Interfaced Digital Control of Self-Sensing Magnetic Suspension Systems with Hysteresis Amplifiers.

A low-cost digital control system is developed for self-sensing magnetic suspension using hysteresis amplifiers.A unipolar-type hysteresis amplifer is designed and manufactured for experimental study.Since the switching rate of the hysteresis amplifier is sensitive to the load impedance, the gap between the electromagnet and the suspended object is estimated from the switching signal.In the developed system, the frequency of the switching signal of the amplifier is converted to a digital form by counting by a counter circuit.The converted signal is inputted to a computer calculating control input for stabilization.The developed digitally controlled magnetic suspension system succeeds in actual self-sensing operation.

Digital Control Using a Counter of Self-Sensing Magnetic Suspension with Hysteresis Amplifiers.

A low-cost digital control system is developed for self-sensing magnetic suspension using hysteresis amplifiers. A single-quadrant hysteresis amplifier is designed and manufactured for experimental study. Since the switching rate of the hysteresis amplifier is sensitive to the load impedance, the gap between the electromagnet and the suspended object is estimated from the switching signal. In the developed system, the frequency of the switching signal of the amplifier is converted to a digital form by counting by a counter circuit. The converted signal is inputted to a computer calculating control input for stabilization. The developed digitally controlled magnetic suspension system succeeds in actual self sensing operation.

Auxiliary Signal Processing System for a Multiparameter Radar

The design of an auxiliary signal processor for a multiparameter radar is described with emphasis on low cost, quick development, and minimum disruption of radar operations. The processor is based around a low-cost digital signal processor card and personal computer controller. With the use of such a concept, an auxiliary processor was implemented for the NCAR CP-2 radar during a 1991 summer field campaign and allowed measurement of additional polarimetric parameters, namely, the differential phase and the copolar cross correlation. Sample data are presented from both the auxiliary and existing radar signal processors.