Papers by Keyword: Pulse Width Modulation

Abstract: People with disabilities find it difficult to operate wheelchairs especially those with disabilities who do not have hands and feet or are disabled. The aim of this research is to improve safety control for electric wheelchairs by detecting obstacles and detecting areas that minimize collisions against obstacles. The contribution of this research is the use of the HC-SR04 ultrasound sensors to avoid a wheelchair colliding with an obstacle using the Pulse Width Modulation (PWM) method which is set based on the distance of the obstacle and the detection of free areas and corridor areas using the PWM method which is adjusted based on following the wall. The HC-SR04 ultrasound sensor is used as input and is processed on the Arduino nanomicrocontroller series to produce a value of PWM. Measuring the HC-SR04 ultrasound sensor against obstacles obtained the largest deviation of 0.72 and average 148,6 cm at a distance of 150 cm and the smallest deviation at a distance of less than 50 cm and the wheelchair can move at slow, medium and fast speeds with the measurement results on Duty Cycles of 71%, 82% and 94%. The results showed that the final distance of the wheelchair against obstacles was less than 50 cm and the wheelchair moved at a distance of 34 - 53 cm following the wall. The results of this study can control motor speed based on obstacles that can be implemented in electric wheelchairs to improve safety and ease of operation for people with disabilities.

Abstract: This paper compares overall efficiency of trapezoidal BLDC motor which is excited by trapezoidal drive and sinusoidal drive. The different characteristics and performance of trapezoidal Brushless DC (BLDC) motor is formed by driving methods. Sinusoidal drive that excites trapezoidal BLDC motor generates greater maximum torque than trapezoidal drive. However, with regard to high frequency loss caused by a pulse width modulation (PWM) carrier and switching loss, the trapezoidal drive has potential to achieve higher efficiency than the sinusoidal drive. Thus, these two drive methods excite trapezoidal BLDC motor are compared to study the efficiency performance. The motors drives are simulated by using MATLAB and their efficiency are measured. The results show that the trapezoidal BLDC motor with trapezoidal drive has higher efficiency compared to trapezoidal BLDC motor with sinusoidal drive.

Abstract: This paper presents an evaluation study of two pwm techniques applied to a three-phase voltage source inverter supplied by photovoltaic (PV) energy sources. A Pspice-based model of the pv array is developed and tested. The power and currant of the pv array versus the voltage is plotted. Then the pv array is connected to a basic three phase voltage source inverter VSI. Two control techniques are used. The first one is the classic sinusoidal pulse width modulation spwm, which is based on the comparison of two signals, the sinusoidal reference and a triangular carrier. The second one is based on the principle of harmonic elimination. The system is simulated using orcad-pspice, the results are given, discussed and compared based on different performance indices (output quality, thd, frequency).

Abstract: This paper proposed the Weighted Least Square method (WLS method) to identify the output filter of three-phase PWM converter, which incorporates the signal processing as well as mathematical techniques into conventional Least Square method. It sets different weights to different measurements according to the phase where it locates, based on the discovery of the correlation between accuracy and phase of current. The algorithm is tested in both simulation and experimental environment, and the results validate that proposed method gives accurate estimation in steady state, and can response within 10ms in when grid voltage drops. This method can work under both balanced and unbalanced operating conditions, therefore provides a powerful tool for various control strategies to better understand the operating conditions. Compared with the invasive method, which intentionally inject a series of white noise in the system, proposed WLS method does not bring any turbulence, while compared with conventional Least Square method, it possesses better stability as well as higher accuracy.

Abstract: There is not a component which can implement the algorithm of space vector pulse width modulation (SVPWM) in the PSCAD/EMTDC. The principle of SVPWM is explained firstly. Then the creating process of the self-defined component and the program flowchart of SVPWM are presented. The algorithms of the subroutine are also discussed in detail. Finally, the simulation is performed by using the self-defined component in the system. Simulation results demonstrate the correctness and validity of the inverter and self-defined component.

Abstract: According to the working condition and characters of pneumatic servo system, the mathematic model of switching valve and executing cylinder controlled by pulse width modulation were built. The mathematic model was made use of in the flow regulator used on gas generator and the simulation model was built with Simulink in Matlab. According to the simulation model, the dynamic characteristic was analyzed.

Abstract: Although class D amplifier has the merits of high efficiency, a little heat and small Bulk, its distortion is larger than linear counterparts due to switching behaviour of power transistors. Its principle and several new pivotal control technologies were presented in this paper. In this way, efficiency of 90% can be achieved and the degree of the distortion can be less than 0.4%.

Abstract: Plasma chemical vaporization machining (PCVM) is an ultraprecise figuring technique for optical components without introducing the subsurface damage. In our previous study, the material removal volume was controlled by changing the scanning speed of the worktable. However, because of inertia of the worktable, a discrepancy between the theoretical scanning speed and the actual scanning speed will occur if the spatial change rate of speed is rapid. Therefore, we proposed the application of the pulse width modulation (PWM) control and the amplitude modulation (AM) control of the applied RF power to control the material removal rate (MRR). Experimental results showed that the relationship between the MRR and the average RF power had high linearity, the control range of the PWM control mode was from 0.19 x 10^-2 mm³/min to 3.90 x 10^-2 mm³/min (from 5% to 100%), which was much wider than that of the AM control mode.

Abstract: In this paper, the implementation of Z-Source Inverter based on Maximum power point tracking scheme (MPPT) for photovoltaic (PV) System is employed. This proposed work has the advantage of more power yield with reduced switching elements in power conditioner. Also a single stage power conversion circuit possessing Z-source network which replaces the boost converter set up in conventional mundane maximum power tracking circuits. The maximum power tracking is the trickiest part which is embedded within the inverter control. Therefore the control over inverter not only operates the PV panel at its maximum possible power but also have a check at the capacitor voltage of the Z-source network, thereby making the system more reliable and power efficient.

Abstract: Simulation of single phase buck boost rectifier with reduced input current THD using single phase matrix converter topology is describing in this paper. Due to the bidirectional feather the operation for buck-boost rectifier can be made through matrix converter topology. And this is possible by the proper switching algorithm to control the switches for their boost and buck operation. The input current nature is almost sinusoidal with low current total current harmonics and the level of THD is below than limit that was defined in the standards of IEEE. With the proper variation in modulation index corresponding changes in the output voltage is observed of buck-boost rectifier. For the synthesis of the output voltage Pulse width modulation (PWM) technique is used. The simulation results using MATLAB/Simulink are providing to validate the feasibility of this proposed method