Pulse Width Modulation Duty Cycle Research Articles

Formation of magnetic double emulsions under steady and variable magnetic fields from a 3D-printed coaxial capillary device

BackgroundDouble emulsions (DEs) have attracted researchers’ attention to be utilized as a promising platform in biomedical and chemical applications. Several actuation mechanisms have been proposed for the generation of DEs. The conventional DE formation approaches (e.g. two-stage emulsification) suffer from low monodispersity. The electric actuation (i.e. coaxial electrospray technology) has been demonstrated as a controllable method for the DE formation, while the capability of magnetic actuation has not been studied yet. ResultIn the present study, the generation of ferrofluid double emulsions (FDEs), made from water-based ferrofluid as a core and oil as a shell, under the magnetic actuation of a permanent magnet with a steady magnetic field and an electromagnet with DC and pulse width modulation (PWM) magnetic fields was investigated with a simple controllable setup fabricated using 3D printing. The effect of various parameters affecting the FDE formation, such as the fluid flow rates, the magnetic field type, the magnetic flux density, and the PWM frequency and duty cycle, on the FDE formation characteristics, including the inner and outer equivalent diameters, and the formation frequency was studied. Under the steady magnetic field, two regimes of the FDE formation were identified: inertia-dominated and magnet-dominated. SignificanceWireless power-free magnetic actuation provides better control over the FDE formation, enhancing this process by increasing the FDE formation frequency with high monodispersity. The PWM magnetic field offers excellent controllability over the FDE formation with low-volume or no, in some cases, satellite droplets by tuning the PWM frequency and the duty cycle.

Characteristics of common code conducted emission of multi-boost converters

One of the primary challenges faced when utilizing power converters such as a DC boost converter is electromagnetic interference (EMI) issues, one of which is common-mode (CM) noise. In order to mitigate the unwanted EMI from converters and design proper EMI filters, it is imperative to possess comprehensive insight into the characteristics of CM noise generated from the converters. This study presents the investigation regarding the characteristic of CM noise emitted by multi-boost converters when operated under varying duty cycle conditions. The research was conducted by measuring and analyzing the CM noise generated by three identical boost converters arranged in a parallel configuration. The result shows that the amplitude of each harmonic of CM noise generated by the multi-boost converters is 5 dB to 10 dB higher than CM noise from a single-boost converter. This is due to each converter being configured in the same conditions, producing a constructive interaction of the generated CM noise. Moreover, the duty cycle of pulse-width modulation (PWM) has a strong influence on the characteristic of the amplitude of each harmonic frequency. It is proven by the amplitude pattern of each harmonic of CM noise. Under duty cycle variations, the converters generate similar peaks and valley amplitude patterns as the Fourier transformation of the trapezoidal waveform used in the PWM setting.

Suppression Strategy of Differential Mode Circulating Current in Parallel Three-Phase PWM Converter

Parallel three-phase pulse width modulation (PWM) converter is a useful technique for increasing the capacity of a power system, but it also introduces the issue of circulating current, which can cause an increase in the loss of power electronics (PE) switches and even lead to over-current, which can affect the overall performance of the system. In this paper, a strategy is proposed for suppressing the differential mode circulating current (DMCC) in each phase of the parallel converter, which is less dependent on system parameters. Based on the mathematical model of the parallel converter, the relationship between the PWM duty cycle and circulating current is derived, which provides a basis for adjusting the switching operation of PE switches. This method requires no additional hardware and is simple to implement with a fast dynamic response. The simulation results verify the correctness of the theoretical analysis, and it can effectively achieve the balanced suppression of DMCC in each phase, which indicates that the method is suitable for the application scenario of parallel current sharing of multiple converters.

Design of a soft bionic elbow exoskeleton based on shape memory alloy spring actuators

Abstract. Shape memory alloy (SMA) is a kind of active deformation material with a self-sensing and driving ability. It is very similar to the performance of human muscles, and through temperature changes to produce phase changes to output force and displacement, it has the ability to restore the initial shape and size. The combination of SMA and wearable robotic technology has the advantages of being light weight, energy-saving, and having great human–exoskeleton interaction. However, the existing flexible exoskeletons driven by SMA are only designed with bionic primary muscles, ignoring the role of antagonistic muscles. This study presents a novel soft bionic elbow exoskeleton based on SMA spring actuators (Sobee-SMA). The exoskeleton adopts a bionic design, combining active deformation material SMA and a high-elastic-material rubber band to simulate the contraction and relaxation of elbow skeletal muscles. Through a pulse width modulation (PWM) experiment, the driving voltage is selected as 12 V, the PWM duty cycle is 90 % during heating, and the PWM duty cycle is 18 % during heat preservation. In a relaxed state of healthy subjects, the range of motion of the elbow is about 0–80∘, and the maximum temperature is about 60–70 ∘C. During the circular movement of the elbow, the maximum temperature can be maintained within the SMA operating temperature without a high temperature. In conclusion, the exoskeleton provides elbow-assisted motion and ensures the safety of the heating process.

Design and Experiments of a Two-Stage Fuzzy Controller for the Off-Center Steer-by-Wire System of an Agricultural Mobile Robot

This paper focuses on the steering motion control of an in-wheel motor-drive robot. The influence of the pulse-width modulation (PWM) duty cycle on steering motion and the steering control method have not yet been proved. Thus, this study aimed to design a steering controller for the off-center steer-by-wire system of a robot. The influence of the PWM duty cycle on the steering motion under different conditions is firstly tested on a test bench. Based on the optimal duty cycles of different cases found in the test, a two-stage fuzzy controller of the duty cycle is designed for the steering system. The first stage of the controller is used to dynamically adjust the PWM duty cycle of the electromagnetic friction lock (EFL). The second stage is designed to realize the self-tuning of the fuzzy controller’s quantization factor and the scale factor. Through two-stage control, the motion of the in-wheel motor and the EFL can be coordinated to realize stable and rapid steering. Considering the robots’ primary application in field roads at present, road tests were ultimately conducted to verify the proposed method. The test results show that the angle response rate of the steering arm is elevated with the increase in the steering angle signal. The proposed controller can sensitively track the target angles with smaller overshoot, yaw rate and lateral acceleration, and better steering accuracy than the PID (proportional–integral–differential) controller under different working conditions.

Pneumatic pressure control based on improved NMPC and its application to aeroengine surge simulation

In the semi-physical simulation of aeroengines, using the pneumatic pressure servo control technology to provide realistic pneumatic excitation to the sensors and electronic controller can improve the confidence of the simulation and reduce the test cost and risk. However, the existing methods could not satisfy the precise simulation of large-amplitude and high-frequency pulsating pressure during aeroengine surge. In this paper, a pneumatic pressure control system with asymmetric groups of the High-Speed on–off Valve (HSV) is designed, and an Improved Nonlinear Model Predictive Control (INMPC) method is proposed. First, the volumetric flow characteristics of HSV are tested and analyzed with Pulse Width Modulation (PWM) signal input. Then, a simplified HSV model with the volume flow characteristic correction is developed. Based on these, an integrated model for the whole system is further established and used as the prediction model in INMPC. To improve the computational speed of the rolling optimization process, the mapping scheme from control signal to PWM duty cycle of HSVs and the objective function with exterior penalty function are designed. Finally, the random step, sinusoidal and real engine surge data are set as the reference pressure in multiple comparative experiments to verify the effectiveness of the pressure tracking system.

Implementation and Validation of Maximum Power Point Tracking (MPPT) of the Photovoltaic System on Arduino Microcontroller

In this research paper, we introduce real-time implementation, using Matlab and Simulink environments. The purpose is to study our proposed system, consisting of a photovoltaic, boost converter, and Arduino mega board. The latter communicates with the physical environment from the current and voltage sensors and executes the proposed MPPT commands (perturb-and-observe, short circuit current, incremental conductance, and open circuit voltage), varying the duty cycle of the signal PWM (Pulse Width Modulation) static converter.

Characterisation of activation pressure, flowrate and spray angle for hollow-cone nozzles controlled by pulse width modulation

Pulse width modulation (PWM) solenoid valves are used for controlling flowrates of hollow-cone nozzles on variable-rate air-assisted orchard sprayers. However, little information is available on the spray characteristics of these PWM-controlled nozzles. Laboratory tests were performed to evaluate the influences of duty cycles of two different design PWM solenoid valves along with five operating pressures on spray characteristics of five hollow-cone nozzles with different disc-core combinations. Parameters of the spray characteristics investigated were nozzle flowrates, upstream and downstream pressures of the PWM valves, nozzle activation pressures and times, and spray angles of water discharged from nozzles. Test results illustrated that these parameters except for the spray angle were greatly affected by the operating pressure, nozzle selection (disc orifice size and quantity of holes on core), PWM duty cycle and solenoid valve design. Spray angles were affected by the duty cycle but not by the PWM valve design. In general, nozzles with larger disc orifice and higher operating pressures resulted in higher flowrates as expected, whilst the nozzle activation pressure and the spray angle decreased as the duty cycle decreased. Thus, when designing orchard sprayers for precision variable-rate pesticide applications, variations in spray characteristics of disc-core type hollow-cone nozzles controlled by PWM solenoid valves should be considered and minimised. This prospect could be facilitated by establishing a digital database of these characteristics.

A Direct Modulation for Matrix Converters Based on the One-Cycle Atomic Operation Developed in Verilog HDL

This article presents a fast direct pulsewidth modulation (PWM) algorithm for the conventional matrix converters developed in Verilog hardware description language. All PWM duty cycle calculations are performed in one cycle by an atomic operation designed as a digital module using field-programmable gate array basic blocks. The algorithm can be extended to any number of output phases. The improved version of the discontinuous direct analytic voltage PWM (DAV-PWM) method is proposed, in which the use of trigonometry, angles, and program loops has been eliminated. The proposed DAV-PWM is equivalent to the space vector modulation; it can be applied during input asymmetry and also allows for the control of the displacement input angle. The proposal has been verified using the circuit simulation in PSIM, digital structure modeling in ModelSim, and finally through an experiment.

Analysis of the Influence of Parameters of a Spraying System Designed for UAV Application on the Spraying Quality Based on Box–Behnken Response Surface Method

With the development of precision agriculture (PA), low-altitude and low-volume spraying based on unmanned aerial vehicles (UAVs) is playing an increasingly important role in the control of crop diseases, pests, and weeds. However, the aerial spraying quality and droplet drift are affected by many factors, some of which are controllable (e.g., flight and spraying parameters) and some of which are not (e.g., environmental parameters). In order to study the influence of spraying parameters on the UAV-based spraying performance, we propose a UAV-compatible spraying system and a customized experimental platform in this work. Through single-factor test and Box–Behnken response surface methods, four influencing factors, namely spraying height, flow rate, distance between nozzles, and pulse width modulation (PWM) duty cycle, were studied under indoor conditions. Variance analysis and multiple quadratic regression fitting were performed on the test data by using Design-Expert 8.0.5B software, and quadratic polynomial regression models of effective spraying width, droplet coverage density, coefficient of variation, and droplet coverage rate were established. Based on the Z-score standardization, a mathematical model of the comprehensive score with four factors was established to evaluate the spraying quality and predict optimal spraying parameters. Test results indicate that the effect intensity of four influencing factors from strong to weak is PWM duty cycle, flow rate, distance between nozzles, and spraying height, and their optimal values are 98.65%, 1.74 L/min, 1.0 m, and 1.60 m, respectively. Additionally, verification experimental results demonstrate that the deviation between the predicted comprehensive score and the actual value was less than 6%. This paper can provide a reference for the design and optimization of UAV spraying systems.

Spray drift characteristics of pulse-width modulation sprays in wind tunnel

Pulse-width modulation (PWM) sprays can improve flow accuracy by adjusting duty cycle and frequency signal which accurately controls the relative proportion of opening time of solenoid valve. The objective of this research was to determine the impacts of PWM duty cycle and frequency on spray drift characteristic. Spray tests were conducted in a wind tunnel with a PWM variable-rate spraying system. The airborne drift and sediment drift were determined with tracer method, and the drift potential reduction (DPR) compared with reference condition of 100% duty cycle at vertical profile and horizontal planes were calculated, respectively. The results show that, at a given frequency, droplet size decreases with the increase of duty cycle, the main reason is that the liquid does not reach full pattern development at lower duty cycle. Duty cycle has a greater impact than the frequency on spray drift, the influence weights of duty cycle on airborne drift and sediment drift were 88.32% and 77.89%, respectively. At a lower PWM frequency, in addition to the droplet size, the spray drift may be affected by the pulsed spray pattern. From the perspective of reducing spray drift, it is recommended that the PWM duty cycle should be set in the range of 20%-70% to reduce the potential drift in PWM sprays. This research provides a pesticide drift reduction scheme for variable spraying technology, which can serve as a theoretical basis for PWM parameter selection. Keywords: nozzle, spray drift, pulse-width modulation, drift potential reduction, droplets spectral DOI: 10.25165/j.ijabe.20221504.7440 Citation: Li L L, Chen L P, Zhang R R, Tang Q, Yi T C, Liu B Q, et al. Spray drift characteristics of pulse-width modulation sprays in wind tunnel. Int J Agric & Biol Eng, 2022; 15(4): 7–15.

Characterization of “cool” and “warm” white light-emitting diodes for low-cost spectrophotometry

The emission properties of “cool” and “warm” white light-emitting diodes were studied in the context of low-cost spectrophotometry. The suitability of pulse-width modulation as a method to control the diode brightness was examined. Both types of light-emitting diode demonstrated emission standard deviation minima at a pulse-width modulation frequency greater than 2000 Hz. The functional wavelength ranges of the light-emitting diodes were approximated using the linearity of brightness as a function of pulse-width modulation duty-cycle and the root mean squared deviation from mean for absorbance measurements. Both light emitting diode types demonstrated good stability in absorbance measurements over long operation times. The “warm” light emitting diode demonstrated a broader range of wavelengths useful for spectrophotometry.

Capacity control of a vehicle air-conditioning system using pulse width modulated duty cycle compressor

The air conditioning system is the most significant auxiliary load on a vehicle where the compressor consumed the largest from the engine, leading to high fuel consumption. Depending upon nature, the variable-capacity compressor reduces cycling on/off. It delivers cooling/heating to a cabin without adjusting the engine rpm, offering superior part-load performance to improve comfort. Consequently, power consumption is growing as an increase in inefficiency. Additionally, systems with continuous compressor modulation can automatically change their energy consumption as required. The paper aims to save energy by reducing fuel consumption in the system. It is because this technology helps us to deduct energy consumption. The test facilities were designed to determine the system capacity with refrigerant side capacity measurement with a mass flow rate of the refrigerant and enthalpy difference across the evaporator. R-134a is considered a refrigerant in this system. Pulse width modulation (PWM) with a duty cycle is used as a command controller or method of reducing power by pulsing its electrical current by effectively chopping it into discrete parts to control the capacity. The results demonstrate that a system consumed 1.2 kW power at 900 rpm, having 4 kW of the capacity. The system also utilized 2 kW power at 2500 rpm with 4.6 kW capacity, which directs the slight increase in power consumption with a significant increase in capacity. Systems with continuous compressor modulation automatically adjust their energy consumption according to the needs of the application. By using this technology of air conditioning, the owner can reduce energy consumption.

Design and implementation for the PWM closed-loop feedback interface circuit of a sandwich capacitive accelerometer based on ARM

Owing to the advantages of small size and high integration that accelerometers made by MEMS technology, the Pulse Width Modulation (PWM) closed-loop feedback interface circuit of a sandwich capacitive accelerometer based on ARM is designed. Based on the design, a simulation by SIMULINK and a PCB board-level circuit are conducted. Simulation and measurement are provided to support the design. The realization of Proportion Integral Differential (PID) control algorithm and the generation of PWM are performed by STM32 microcontroller instead of the circuit in the design. The output form of the interface circuit is PWM with different duty cycle and filtered DC voltage. According to the measurement results, the output of the PWM duty cycle change is 16.9%/g, and the sensitivity is 1.045 V/g.

A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding

This article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load’s terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion (THD) of the generated load voltage. The third variant of modulation concerns maximizing the voltage transfer ratio, minimizing the number of switching, and the common-mode voltage cancellation. The discussed modulations are based on the concept of sinusoidal voltage quadrature signals, which can be an effective alternative to the classic space-vector approach. In the proposed approach, the geometrical arrangement of basic vectors needed to synthesize output voltages is built from the less number of vectors, which is equal to the number of the matrix converter’s terminals. The PWM duty cycle computation is performed using only a second-order determinant of the voltages coordinate matrix without using trigonometric functions. A new approach to the PWM duty cycles computing and the load voltage synthesis by 5 × 5 and 12 × 12 topologies has been verified using the PSIM simulation software.

Hybrid current loop timing control method for permanent magnet AC servo systems

The relationship between current loop bandwidth and time delay was analyzed on the basis of the mathematical model of a current loop. The time delays generated by double sampling and pulse-width modulation (PWM) duty cycle double update (DSDU) and immediate sampling and PWM duty cycle immediate update (ISIU) and their effects on the current loop bandwidth were compared. Combining DSDU and ISIU, a novel hybrid current loop timing control method was proposed to solve the problems of insufficient bandwidth expansion and low voltage output capability. ISIU was used when calculation delay is less than or equal to the action time of the zero voltage vector to expand the bandwidth. Meanwhile, DSDU was adopted when calculation delay is greater than the action time of the zero voltage vector to improve voltage output capability. Experimental results proved that the proposed method can reduce current loop delay to increase bandwidth without changing switching frequency and limiting output voltage.

Assessment of chemical concentration accuracy and mixture uniformity of premixing in-line injection system

A premixing in-line injection system was developed and attached as a retrofit to a laser-guided variable-rate orchard sprayer. Chemical concentration accuracy and spray mixture uniformity produced from the premixing system was investigated with various viscosities of simulated pesticides and duty cycles of pulse-width-modulated (PWM) nozzles at different positions on the sprayer. The chemical concentration accuracy was accessed by calculating the relative error (RE) between measured and target concentrations, and mixture uniformity was evaluated by the coefficient of variation (CV) of the mixture concentration. Test results showed that the measured concentration was consistent across different nozzle positions, and RE and CV were observed within desirable ranges (<5.0%) for all nozzle positions and target concentrations. The average measured concentration slightly decreased as the viscosity of simulated pesticides increased. This phenomenon was more obvious under higher target concentrations. In addition, effects of PWM duty cycle combinations on the chemical concentration accuracy and mixture uniformity varied with number of active nozzles. It was found that RE and CV were larger than the desirable level (greater than5.0%) but were lower than the acceptable level (<10.0%) under conditions that nozzles were partly activated. For other treatments which all nozzles were activated, RE and CV were under the desirable level (<5.0%) for all target concentrations and nozzle positions. Laboratory tests demonstrated that the premixing in-line injection system was able to adequately mix the simulated pesticides with water, and could provide accurate and consistent uniformity of spray mixtures for the variable-rate spray nozzles to discharge different viscosities of simulated pesticides at different duty cycle combinations.

A New Concept of PWM Duty Cycle Computation Using the Barycentric Coordinates in a Three–Dimensional Voltage Vectors Arrangement

The paper presents a novel approach to the Pulse Width Modulation (PWM) duty cycle computing for complex or irregular voltage vector arrangements in the two (2D) and three–dimensional (3D) Cartesian coordinate systems. The given vectors arrangement can be built using at least three vectors or collections with variable number of involved vectors (i.e. virtual vectors). Graphically, these vectors form a convex figure, in particular, a triangle or a tetrahedron. The reference voltage vector position inside that figure can be expressed by the barycentric coordinates , which are calculated using the second (2D case) or the third–degree determinant (3D case) – without trigonometry and angles. Thus, the speed of the PWM duty cycle computation rises significantly. The use of the triangle area or the tetrahedron volume, instead of the standard vector projection also permits for a well–defined and universal approach to identifying the reference vector position, especially for converters with complex and/or deformed space–vector diagrams (i.e. floating DC–link, multisource DC–link). The proposed computation scheme is based on simple instructions without trigonometry thereby, the DSP processor, or digital solution for field–programmable gate array, can fast–perform this operation using atomic operations. The aim of the presented considerations is not a novel PWM modulation, but a computable idea of a general calculation scheme for cases in which the distribution of vectors is non-trivial. A detailed algebraic and geometric analysis, as well as mathematical proofs on the total consistency of the results with the standard projection method, are also included. Subsequently, the Three–Dimensional Space Vector Modulation (3D–SVM), is considered as a special background to present a novel approach.

Direct Modulation for Conventional Matrix Converters Using Analytical Signals and Barycentric Coordinates

This paper proposes the generalized direct modulation for Conventional Matrix Converters (CMC) using the concept of analytical signals and barycentric coordinates. The paper proposes a novel approach to the Pulse Width Modulation (PWM) duty cycle computing, which allows faster prototyping of direct control algorithms. The explanation of the new idea using analytical considerations demonstrating the principles of direct voltage synthesis has been presented in the article. The study concerns mainly the CMC $3\times 3$ but solutions for $3\times {n}$ , $5\times {5}$ , and $5\times {3}$ topologies have also been discussed. The transformation of instantaneous input voltages to analytic signals great permits for simple presenting of real input voltage conditions such as waveform type, asymmetry or other deformation like higher–order harmonics. The proposed interpolation methods allow for determining the values of PWM duty cycles using simple formulas based on the determinants of the 2nd–degree matrices. Therefore, the proposed method, which based on the barycentric coordinates, frees an algorithm from trigonometry and angles.

Design and implementation of a 350-watt BLDC motor driver using an Insulated Gate Bipolar Transistor (IGBT)

IGBT device was not commonly used as a BLDC motor speed controller. This paper described the successful of using IGBTs in a 350Watt BLDC motor speed controller. Triple bridge configuration with PWM (Pulse Width Modulation) wave signal for power tuning was mainly integrated as a main switching method in order to drive the current commutation cycle. Also, an efficient bootstrap IC was designated to perform as the high and low side driver. The data were measured by using a current sensor and a DC voltage sensor to measure the current and the voltage delivered from the power source. Then, IGBT device was activated based on triple bridge commutation cycle and phase based on motor hall effect sensor triggering signal. The performance was also tested by varying the duty cycle input ratio and its PWM frequency. It can conclude that the BLDC motor controller can be made by using an IGBT and added gate drivers for the IGBT. Meanwhile, to adjust the commutation cycle, a high speed processor was used to generate gate activation and PWM signal. Changing the PWM duty cycle starting from 10% to 90% by turning the setting point, observed that BLDC motor rotates successfully without load and maximum power used was 111.20 watts with 2,32 amperes current at 48 volts supply voltage.