Pulse Width Modulation Signal Research Articles

Coupled Inductor Based Bidirectional Resonant Converter With Sine Wave Modulation in Wide Voltage Range

This letter proposes a coupled inductor based bidirectional series resonant converter (CIBSRC). In addition, a sine-wave modulation (SWM) with fixed frequency is also proposed to achieve load independent voltage gain for wide voltage range. The proposed CIBSRC integrates a boost stage and a resonant stage by a coupled inductor which replaces boost inductor, resonant inductor, and high frequency transformer. Compared with the bidirectional integrated resonant topologies, the number of magnetic components is less. Under proposed SWM, only one set of pulsewidth modulation signal is needed and zero voltage switching (ZVS) of all switches could be realized. Besides, the resonant current is a sine-wave which can simplify ZVS analysis and reduce current harmonics. A 500-W prototype with 100–200 V input voltage and 360 V output voltage was built and the results proved the reliability and validity.

An Improved Full-Bridge Converter With a Five-Diode Rectifier for High Efficiency in Wide Voltage Range

This article presents an improved full-bridge converter with a five-diode rectifier. The primary side circuit is composed of a full bridge with two transformers and two split capacitors. On the secondary side, five diodes are employed in the rectifier stage. By using the asymmetrical pulse width modulation (PWM) signals, this converter can realize the zero-voltage switching (ZVS) of all switches and reduce the circulating current. The two transformers share the load power equally in whole load range. Compared with the other dual transformer isolated full-bridge converters, the transformers in the proposed converter are easy to optimize because of the load power equal sharing. Furthermore, the output filter inductance is reduced, which reduces the loss and volume. According to the loss analysis, the proposed converter has higher efficiency compared with some other dc-dc converters. The experimental results of a prototype with 300–400 V input voltage and 250 V/4 A output verify the performance of the proposed converter.

Multi-objective cost function based finite control set-sliding mode control strategy for single-phase split source inverters

This paper proposes a multi-objective cost function-based finite control set sliding mode control (SMC) strategy for single-phase split-source inverters (SSI). The single-phase SSI is a fourth order system in which the control of four (inductor current and capacitor voltage in DC-side and inductor current and capacitor voltage in AC-side) variables is essential. Moreover, a complex modulation scheme is needed to generate the pulse width modulation signals for the switching devices of SSI. The proposed control strategy is based on a multi-objective cost function finite control set SMC approach. As a consequence of using multi-objective cost function, the control of DC- and AC-side variables can be accomplished simultaneously. Moreover, the use of finite control set eliminates the modulation scheme requirement. Also, the use of multi-objective cost function together with the finite control set simplifies the controller design as the hysteresis band and its tuning requirement are not needed. The robustness of proposed control strategy against parameter variations is investigated and compared with that of the hysteresis band-based SMC and conventional MPC methods. Experimental results are presented to verify the effectiveness of the proposed control strategy.

A Design of FPGA-Based Neural Network PID Controller for Motion Control System.

In the actual industrial production process, the method of adaptively tuning proportional–integral–derivative (PID) parameters online by neural network can adapt to different characteristics of different controlled objects better than the controller with PID. However, the commonly used microcontroller unit (MCU) cannot meet the application scenarios of real time and high reliability. Therefore, in this paper, a closed-loop motion control system based on BP neural network (BPNN) PID controller by using a Xilinx field programmable gate array (FPGA) solution is proposed. In the design of the controller, it is divided into several sub-modules according to the modular design idea. The forward propagation module is used to complete the forward propagation operation from the input layer to the output layer. The PID module implements the mapping of PID arithmetic to register transfer level (RTL) and is responsible for completing the output of control amount. The main state machine module generates enable signals that control the sequential execution of each sub-module. The error backpropagation and weight update module completes the update of the weights of each layer of the network. The peripheral modules of the control system are divided into two main parts. The speed measurement module completes the acquisition of the output pulse signal of the encoder and the measurement of the motor speed. The pulse width modulation (PWM) signal generation module generates PWM waves with different duty cycles to control the rotation speed of the motor. A co-simulation of Modelsim and Simulink is used to simulate and verify the system, and a test analysis is also performed on the development platform. The results show that the proposed system can realize the self-tuning of PID control parameters, and also has the characteristics of reliable performance, high real-time performance, and strong anti-interference. Compared with MCU, the convergence speed is far more than three orders of magnitude, which proves its superiority.

High-precision fitting of plant growth spectra by multi-LED lighting systems based on segment fitting method

We present a tunable, general-purpose, light-emitting diode-based spectrally tunable light source that achieves high-precision fitting of chlorophyll b absorption spectra from 400 to 700 nm using 11 LEDs with different peak wavelengths. The target spectrum is divided into gentle and steep segments, and the optimal number of LEDs to be used at different wavelengths is determined by the segment fitting method. Then, the results were further optimized by fitting experiments, and finally the best combination consisting of 11 different peak wavelength LEDs was obtained. The results showed that the correlation coefficient R2 reached 0.9664. The precise control of each LED current by means of the pulse width modulation signal output from the microcontroller, and the output spectrum of the system was measured using a spectrometer. The results show that the correlation coefficient R2 reaches 0.9315.

Nonlinear Adaptive Control with Asymmetric Pressure Difference Compensation of a Hydraulic Pressure Servo System Using Two High Speed On/Off Valves

A hydraulic pressure servo system based on two high-speed on/off valves (HSV) is a discontinuous system due to the discrete flow of HSV when driven by pulse width modulation (PWM) signal. Pressure variation in the testing chamber is determined by the flow rate difference between the charging and discharging HSV. In this paper, a pressure controller consisting of a differential PWM (DPWM) scheme, asymmetric pressure difference compensation (APDC) and nonlinear adaptive control (NAC) is proposed to precisely control the pressure. The DPWM scheme is designed to improve the resolution of the net flow rate into the testing chamber. Furthermore, due to the strong asymmetry between the charging and the discharging process, the APDC method is proposed to design the two initial duty cycles of the DPWM signal which help to balance its charging and discharging ability under different working pressure points. Since the pressure system is a nonlinear, uncertain system due to oil compression and leakage, the NAC is designed to calculate the control duty cycle of the DPWM signal, which is used to overcome the unmodeled dynamic and parameter uncertainties. Comparative experiments indicate that the proposed controller can ensure good pressure tracking performance and enhance system robustness under different working pressure points and tracking frequencies.

PWM CONVERTER BASED ON TAKAGI-SUGENO FUZZY LOGIC INFERENCE FOR INTERNET OF THINGS SYSTEMS

The aim of the study is to apply fuzzy logic in IoT systems to estimate various environmental factors such as temperature, humidity, etc., and to convert them using the Takagi-Sugeno algorithm into a pulse-width modulation (PWM) signal to control motor speed, thermal power of heaters and other parameters in an energy efficient way. The paper explores the use of fuzzy data converters based on intelligent fuzzy inference systems in Internet of Things systems. An approach has been developed for converting fuzzified input parameters read from sensors in a PWM signal based on the Takagi-Sugeno fuzzy algorithm. Based on the proposed method, an IT-based smart fan was developed that supports a PWM signal. Therefore, the proposed fuzzy PWM converter method was used to simulate the operation of a fuzzy model using three parameters: temperature, relative humidity, and carbon dioxide (CO2) concentration in relation to the PWM signal. The proposed method demonstrates the ease of training a reasonable fan control system and enables efficient energy consumption.

Close-Loop Current Control With Current-Sensing Resistor for Electromagnet Driven by Full-Bridge PWM Inverter

The full-bridge pulse-width-modulation (PWM) inverter is wildly applied to drive the electromagnet and enables advanced technologies, such as the active magnetic bearing (AMB) and the permanent-electro magnetic suspension (PEMS). However, the characteristic relationship between the current through the electromagnet and the duty cycle of the PWM signal has strong nonlinearity around the zero current. Moreover, the electromagnet possesses the induction that results in the time constant and significantly hinders the change of the current. Hence, the open-loop control of the full-bridge PWM inverter cannot accurately or timely tune the current through the electromagnet, especially around the zero current. This work proposes a closed-loop current control approach by three steps: (1) inserting a current-sensing resistor into the middle of the electromagnet, (2) obtaining the current signal with an analog signal-processing circuit, and (3) generating the PWM signal with the bang-bang control circuit. The proposed approach innovatively arranges the current-sensing resistor to take advantage of the symmetry and to minimize the influence from the high-frequency switching of the inverter, so that the measured current signal is comparable to the hall-effect current sensor. The experimental results demonstrate the effectiveness and efficiency of the proposed closed-loop current control approach, though the weak charging capability of the full-bridge PWM inverter still hinders its performance.

Charge-Controller Optimization on Lead-Acid Battery in Solar PV Systems: Temperature Effects and Efficiency Improvement

Long-term cell performance is very sensitive to the cell operating temperature, and cell storage capacity can degrade quickly, if the temperature is not maintained within a narrow range (25–50 °C) during charging and discharging of (solar) batteries [1]. Efforts are recently being dedicated to developing models that seek to provide insights into that issue. However, not all models consider the operation of the photovoltaic (PV) battery storage system with regard to battery optimization and temperature effects. The present work provides a controllable algorithm to help charge controllers provide exact amount of PV electricity (charge equalization) to batteries with temperature compensation included, and a proposed charging and discharging schedules of the battery storage. The temperature compensated duty cycle for charging is modelled and the pulse-width modulation (PWM) signal is programmed to change with temperature following this duty cycle model. This research work is based on the optimization of solar battery storage where the micro controller-based charge controller enhances battery life by monitoring the temperature and controlling charging voltages and float charging voltages for specific temperatures. A buck converter was simulated in Proteus, and then realized in the laboratory. The duty cycle of the buck converter was adjusted with temperature. Results collected from lab experiments were plotted on MatLab and it shows homogeneity with calculated results. Moreover, battery-charging currents, battery direct current (DC) disconnect and battery switching for charging and discharging were performed for the converter. Future work is to extend this study to large-scale solar photovoltaic systems in order to overcome the operation limits encountered.

Temperature-Aware Adaptive Control for Automotive Front-Lighting System

Adaptive front-lighting systems (AFSs) have been widely adopted to automotive industries for providing higher driver’s safety. As their light sources, multi-string light-emitting diodes (LED) arrays have been widely adopted because of their simpler driver controls. Recently, micro-structured AFSs (μAFSs) with a micro-LED (μLED) array are highly demanded for their controllability of individual LEDs. However, the integration of a μLED array and its high-power active-matrix driver are not available on the market. Moreover, a high-power driver causes not only a significant variation in driving current, but also a higher power density requiring over-temperature protection (OTP). In this paper, the average current through each μLED is adaptively controlled with pulse width modulation (PWM) in conjunction with an additional PWM control for temperature calibration. Experimental results with a 16 × 16 μLED array placed on top of the proposed driver show that a 5-bit PWM signal controls the average current through each μLED cell up to 11 mA. The maximum current error of 4.11% at 100 °C is reduced to 0.23%. When OTP is enabled, the amount of average pixel current reduction depends on the given temperature. The maximum power efficiency of the proposed μAFSs driver is as high as 92.3%.

Визначення оптимальних параметрів широтно- імпульсно модульваної напруги для живлення електромагнітного віброприводу

Goal. To determine the optimal parameters of various types of pulse-width modulated (PWM) voltage, which is used in the control systems of the electromagnetic vibration drive to create resonant vibrating machines and control the parameters of the working body of the vibrating machine in the resonant mode. Method. The work is based on the analysis of the spectrum of the main three forms of PWM signals in their low-frequency region, to which the oscillating mechanical system of vibrating machines responds. To estimate the PWM-encoded sine wave corresponding to the resonant frequency of the vibrating machine, the mean square deviation was used in the time domain, and the nonlinear distortion coefficient (harmonic) was used in the spectral domain. Results. The results. A mathematical apparatus was built and a connection was established between the oscillating mechanical system of the vibrating machine, the external PWM parameters and the characteristics of the sinusoidal signal encoded by it in the time and spectral domains. Scientific novelty. For the first time, a mathematical model was obtained and the influence of the parameters of the oscillating mechanical system of the vibrating machine and the carrier frequency of the pulse-width modulated voltage on the root-mean-square deviation and the coefficient of nonlinear distortions (harmonics) of the signal feeding the electromagnetic vibration drive was simulated. Practical significance. A technique for calculating the carrier frequency of the PWM sinusoidal voltage is proposed, which can be used to develop an algorithm for controlling power switches (transistors) and choosing the type of power switches at the stage of designing the power part of control systems with an electromagnetic vibration drive of controlled and adaptive vibration machines.

Bidirectional Buck-Boost and Series LC-Based Power Balancing Units for Photovoltaic DC Collection System

The input-independent and output-series (IIOS) structure is often used in the high step-up ratio converters required for medium-voltage dc (MVdc) grid interface of photovoltaic (PV) systems, which achieves high voltage gain and ensures high efficiency. However, due to the characteristics of IIOS structure, when some PV arrays are shadowed or malfunction, the generated power of these modules will be mismatched. Mismatched power will result in output capacitor voltages deviating from the rated value, which is not conducive to the standardized multimodule design. Besides, voltages of some PV arrays will deviate from their maximum power point (MPP) value, leading to a decrease in the total generated power. In order to balance the module output voltages of the IIOS structure, this article proposes bidirectional buck-boost and series <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC-</i> based power balancing units (LC-PBUs) for PV dc collection systems. Compared with a traditional solution, nearly half of the switches are saved and half of the inductors are displaced by small inductors. Power balance can be achieved through the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -PBUs by controlling the duty ratio and the phase of the pulse-width modulation (PWM) signal. Simulations and experiments are carried out to verify the effectiveness of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -PBU under power sags.

Self-Localization of Tethered Drones without a Cable Force Sensor in GPS-Denied Environments

This paper considers the self-localization of a tethered drone without using a cable-tension force sensor in GPS-denied environments. The original problem is converted to a state-estimation problem, where the cable-tension force and the three-dimensional position of the drone with respect to a ground platform are estimated using an extended Kalman filter (EKF). The proposed approach uses the data reported by the onboard electric motors (i.e., the pulse width modulation (PWM) signals), accelerometers, gyroscopes, and altimeter, embedded in the commercial-of-the-shelf (COTS) inertial measurement units (IMU). A system-identification experiment was conducted to determine the model that computes the drone thrust force using the PWM signals. The proposed approach was compared with an existing work that assumes known cable-tension force. Simulation results show that the proposed approach produces estimates with less than 0.3-m errors when the actual cable-tension force is greater than 1 N.

Application of Wavelet Scattering and Machine Learning on Structural Health Diagnosis for Quadcopter

The aim of this study was to examine the health diagnosis classification method of quadcopter structures with different mixed faults. The loosening of the motor mount, damage to the propeller, and the loosening of the arm mount were the main fault conditions investigated. Data were first acquired under non-fault conditions and the conditions of the three types of fault. Then, the features of the vibration and pulse width modulation signals were extracted by root mean square, standard deviation, and sample entropy. Moreover, the features of the audio signal were extracted by wavelet scattering, which contains time-frequency domain information that provides significant power for classification. In this paper, we propose a simple machine learning method, based on the k-Nearest Neighbor (kNN), not only for classification but also demonstrating the efficacy of the features. To test the limits of accuracy, different configurations of kNN parameters are deployed, in addition to the features. In summary, as a result of the highly efficacious features, despite mixed fault conditions, the accuracy reached 90.73%. This method improves the accuracy of mixed faults’ classification and maintains a certain level of classification effectiveness.

The impact of communications channel bandwidth on the accuracy of pulse-width signal transmission

Pulse-width modulation (PWM) signals used in various areas are sent to the receiver through a communications channel that distorts their waveform due to the limitations of the frequency range. It is not always possible to reduce additive (fluctuation) noises that are also present within the PWM signal to negligible levels. Limiting the range of frequencies transmitted over a communications channel results in both the deterioration of PWM signal front slopes and the changes in the spectral specifications of the fluctuation noise. The simulation of pulse signal formation helped identify a correlation between the pulse front slope and the number of harmonic components transmitted over the communications channel. Through the analysis, we established a correlation between pulse time and the additive noise parameters along with the bandwidth of the real communications channel. These calculations might be useful for problems where it is necessary to formulate the requirements for the communications channel transmitting the PWM signal.

Correction of errors and harmonic distortion in pulse-width modulation of digital signals

Pulse-Width (PW) modulation is widely used in those applications where an analog or digital signal has to be encoded in the time domain as a binary stream, such as switched-mode power amplifiers in transmitters of modern telecommunication standards, high-resolution digital signal conversion using single-bit digital-to-analog converters, and many others. Due to the fact that digital signals are sampled in the time domain, the quality of the resulting PW modulated waveforms is worsened by harmonic distortion. Multilevel PW modulation has been proposed to reduce these adverse effects, but the modulated waveform is no longer binary. In this paper, the mechanisms by which harmonic distortion is produced are analyzed. As a result, the distortion terms are mathematically quantified and used to correct the errors. Note that a correction network based on a simple subtraction of the distortion terms from the PW modulated signal would produce a waveform that would no longer be binary. The proposed correction network is implemented in the digital domain and, by means of a sigma-delta modulator, preserves the binary feature of the PW modulated output.

A high frequency AC heater based on switched capacitors for lithium-ion batteries at low temperature

Lithium-ion batteries suffer from significant performance deterioration at subzero temperatures, which brings difficulty to the promotion of electric vehicles. In this paper, a high frequency alternating current (AC) heater based on switched capacitors is proposed which can heat batteries with fast speed and good uniformity without external energy supply. The optimal heating frequency is determined based on particle swarm optimization to obtain the fastest heating speed. The proposed heating topology only needs one pair of pulse width modulation signals to drive four MOSFETs to circulate an alternating current between the batteries and switched capacitors, leading to easy control with simple structure and low cost. The effectiveness of the proposed AC heater is validated under different heating frequencies at initial temperature −20°C and –25°C, respectively. Experimental results show that by circulating an alternating current with the optimal heating frequency of 10 kHz, the proposed heater can heat lithium-ion batteries from -20°C to 0°C within 2.2min, consuming only 5.4% cell energy, and can heat lithium-ion batteries from -25°C to 0°C within 9 min, consuming only 7.8% cell energy.

Motion Characteristics of a Clutch Actuator for Heavy-Duty Vehicles with Automated Mechanical Transmission

Clutch control has a great effect on the starting quality and shifting quality of heavy-duty vehicles with automated mechanical transmission (AMT). The motion characteristics of a clutch actuator for heavy-duty vehicles with AMT are studied in this paper to investigate the clutch control strategy further. The modeling principle of the automatic clutch system is analyzed, and a simulation analysis is given to prove its validity and rationality. Normalized velocity and velocity modulation percentage are proposed as evaluation parameters for the clutch actuator driven by pulse width modulation (PWM) signals. Based on an AMT test bench, the actuator motion characteristics are analyzed. Experimental results show that the range of normalized velocity and velocity modulation percentage are obtained for the clutch engagement and disengagement processes. By analyzing the experimental data, the engaging velocity and disengaging velocity of the actuator are estimated using the solenoid valves in combination. The research results provide a fundamental basis for precise controlling of the clutch and improving the smoothness of heave-duty vehicles.

Increasing Energy Efficiency With Fuzzy Logic Control in FPGA-Based Electromagnetic Stirrer

In this study, a new field-programmable gate array (FPGA)-based electromagnetic stirrer system was developed allowing mixing on a single axis, and the energy efficiency of the system was increased with fuzzy logic control. The electromagnetic stirrer system was designed with three phases and each phase is fed with pulsewidth modulation (PWM) voltage with 120° phase difference. Ranked control of phases in the system used the FPGA structure in the myRIO® embedded system to determine the PWM signal production, increase intervals for phase frequencies, and rotation rate of the magnetic stir bar. In the system, to increase the energy efficiency with fuzzy logic control, the ARM® microcontroller structure in the myRIO® embedded system was used. Programming of the myRIO® embedded system was provided through the graphic-based LabVIEW <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> software. In situations where the system is operated with 100% duty cycle, the force affecting the magnetic stir bar should be continuous and have fixed value until the next phase change. As a result, the magnetic stir bar performs more than 120° rotation and a braking effect of the force is observed. To resolve this situation, fuzzy logic control ensured operation of a different duty cycle without loss of speed of the stir bar. Thus, the energy efficiency of the system was increased with lower current and lower stimulation duration. Within the scope of this article, the experimental results obtained about the structure, control, and energy efficiency of the electromagnetic stirrer system are discussed in detail.

Airborne Laser Communication System with Automated Tracking

The acquisition, alignment, and tracking system is an important part of airborne laser communication and is the prerequisite and guarantee for the normal communication link. In order to solve the problem of automatic tracking of laser communication links in the airborne environment, the rapid capture, alignment, and tracking of beams between terminals are realized. This article proposes a stepping motor as a control servo system and a four-quadrant detector as an automatic tracking method for the detection unit. The pulse width modulation signal controls the rotation speed of the stepping motor and combines the position distribution of the light spot on the four-quadrant detector to achieve high-precision beam tracking. On this basis, indoor simulation experiments are carried out. After many experiments, the tracking accuracy is better than 2.5 μrad, which shows that the system can be applied to airborne laser communication, and it is verified that this method has good automatic tracking performance for airborne laser communication.