Commutation Period Research Articles

An Improved Torque Sharing Function to Minimize Torque Ripple and Increase Average Torque for Switched Reluctance Motor Drives

—This article presents a novel torque ripple minimization approach based on the genetic algorithm (GA) for the switched reluctance motor (SRM) drives. The fitness function of the GA is designed on the basis of two main optimization criteria. The first optimization criteria; three objectives are defined to optimize commutation angles minimizing torque ripple and copper loss. The second optimization criteria; an objective is defined to eliminate the negative torque which decreases the average torque in SRM drives. The achievement of all objectives depends on the adjusting appropriate the commutation angles of the torque sharing functions (TSF) during the commutation period. All of conventional TSFs are dependent on three different commutation angles, namely turn-on, turn-off, and overlapping. Due to the nonlinear phase inductances of SRM, the delay of current rising and falling time are not unity in overlapping commutation region. To overcome the separation of the incoming and outgoing phase currents during the commutation region, rise angle, and fall angle are used instead of overlapping angle. GA is used to optimize the commutation angles of conventional (sinusoidal) TSF and improved (sinusoidal) TSF. At the same time, the elimination negative torque effects on torque ripple, average torque, and copper loss is investigated.

Implications of attending the closest school on adolescents’ physical activity and car travel in Dunedin, New Zealand

BackgroundHome-to-school distances and the need for students to be driven to/from school may limit adolescents' physical activity levels. School choice and school zoning policies can influence rates of active transport to/from school, and traffic volumes during school commuting times. This study aimed to quantify the effects of adolescents' enrolment in the closest school or not, on private vehicle use and adolescents’ physical activity levels in Dunedin city, New Zealand. MethodsNew Zealand Travel Survey data (2003–2013; 2493 Dunedin respondents) were analysed to examine school-travel related private motorised trips. Dunedin-specific data from adolescents (from six Dunedin non-integrated public schools without school zoning) were analysed including self-reported survey data on school travel modes (797 adolescents), distance to the current and closest schools (797 adolescents) and accelerometer-measured moderate-to-vigorous intensity physical activity (MVPA) (121 adolescents). ResultsDuring the school commute time (8–9 am and 3–4 pm), an estimated 11.5% of car trips (95% CI 7.8%–16.8%) and 12.5% of car distance driven (95% CI 8.8%–17.7%) were related to secondary-school travel with approximately half of these involving trip-chaining. Compared to adolescents living beyond cycling distance (>4 km) from their current school, adolescents living within walkable distance (≤2.25 km) and cyclable distance (>2.25-≤4 km) accumulated an additional 12.1 min (95% CI 7.0 to 17.2) and 6.1 min (95%CI 1.0 to 11.2) of daily MVPA during the school commute time, respectively. If adolescents currently enrolled at a distant school were to attend the closest school, they could accrue an additional 3.4 min MVPA during the 2-h school commute time period and school travel-related private car trips would be reduced by 7%. ConclusionsIn Dunedin, New Zealand, modest reductions in private vehicle traffic, particularly around schools, and increases in adolescents’ MVPA during the school commute period would be expected if all adolescents attended the closest school.

A Hybrid Torque Sharing Function with Controlled Commutation Period for Torque Ripple Minimization in SRM

A Hybrid Torque Sharing Function with Controlled Commutation Period for Torque Ripple Minimization in SRM

Torque ripple suppression of brushless DC motor drives using an alternating two‐phase and three‐phase conduction mode

Commutation torque ripple is an important factor affecting the performance of brushless DC (BLDC) motor drives. In order to suppress this torque ripple, an alternating conduction control strategy between the two-phase and three-phase conduction mode has been proposed in this study. During the non-commutation periods, the conventional two-phase conduction mode is selected to drive the BLDC motor. While during the commutation period, the commutation torque ripple is reduced by employing an alternating two-phase and three-phase conduction mode. By calculating the duty cycle of the three-phase conduction mode, which indicates whether the rate of change in current in the incoming and outgoing phase is equal during the commutation interval, the commutation torque ripple is effectively reduced, while the current in the non-commutated phase is maintained constant. Simulation and experimental results show that the proposed method can suppress the commutation torque ripple efficiently, particularly at high rotational speeds of the motor.

Smart city oriented optimization of residential blocks on intensive urban sensing data based on fuzzy evaluation algorithm

The unreasonable planning of land use in residential blocks affects the quality of the city and the comfort and convenience of urban residents. How to improve the vitality of the street from the source is an urgent problem to be solved in urban and rural planning disciplines. This paper selects 18 residential districts in Xi’an, and uses a multivariate linear stepwise regression to establish a relationship model between street vitality and intensive land use indices in three different periods of non-commuting, weekly commuting, and weekend. Using fuzzy evaluation techniques, the degree of land use intensification in different residential blocks was analyzed. Using the relational model and evaluation conclusions, the appropriate range of street vitality in residential blocks was determined, and the constructed model was used to obtain the suitable index range for intensive land use under street vitality. The results show that the street vitality and building density, the proportion of commercial space along the street and the red line width of the street are most affected during the non-commuting period during the week. The street vitality during the commute period is most closely related to the building density, building mix and street network density. Street dynamics are most closely related to building density, building mix, and street red line width during weekends. The conclusions of the study provide theoretical support and data support for the optimization and transformation of land use in residential blocks, and ultimately aim to stimulate street vitality and promote the realization of intensive land use in residential blocks.

Torque Ripple Minimization of a Switched Reluctance Motor using a Torque Sharing Function based on the Overlap Control Technique

The torque ripple produced in a switched reluctance motor (SRM) can be seen as one of its major drawbacks. It occurs mainly due to the sequential switching of the motor phases and changes in the length of the air gap. The torque sharing functions (TSFs) are the more effective and favorable techniques developed to reduce the torque ripple in SRMs. However, the time responses of instantaneous torque for incoming and outgoing phases during commutation period (CP) are different. In addition, with increasing motor speed the CP decreases and the torque response of the outgoing phase oversteps it. In this paper, a modified torque sharing function based on the change of the overlap angle during the commutation process depending on the motor speed is presented. In the designed control algorithm of the TSFs, the motor speed is has become an input besides the rotor position and the torque command. The commutation time is precisely adjusted enough for the commutating process. The proposed method gives good results in a wide speed range. To deduce the magnetic characteristics of the SRM, finite element analysis (FEA) is applied and a look-up table model is derived. The effectiveness and robustness of the proposed control technique are exhibited in the simulation results.

Modeling of ZSI based BLDCM For Reduction of Commutation Torque Ripple

This paper proposes a new technology, which reduces ripple context in Brush less DC Motor. This technology is having the similar modulation modes in conduction period and commutation period. In Grid applications, Brush less DC motor produces a torque ripple, hence for the reduction of ripple content, a ZSI based BLDCM is proposed in this technology. The buck-boost property of a ZSI gives a effective reduction of the ripple content and also improves the DC voltage utilization. The MATLAB/Simulink/Simpower system were selected to design and implement a ZSI based BLDCM for less torque ripple content.

Novel modulation method for torque ripple suppression of brushless DC motors based on SIMO DC–DC converter

In this paper, a novel modulation method is proposed for the torque ripple suppression of a brushless DC motor (BLDCM) during both the commutation period and the speed regulation period. The main sources of torque ripple are the imbalance current during commutation and the PWM during speed regulation. A single-inductor multiple-output (SIMO) Buck DC–DC converter is adopted to generate input voltage for the inverter driver of a BLDCM. During the commutation period, the input voltage of an inverter can be adjusted to four times the back electromotive force (EMF), which suppresses the torque ripple caused by imbalance commutation current. Meanwhile, by changing the output voltage of a SIMO DC–DC, the speed of a BLDCM can be regulated without PWM on the inverter switches, which also suppresses the torque ripple. A control algorithm is applied on a Field Programmable Gate Array (FPGA), and the proposed BLDCM drive prototype is fabricated and tested. Measurement results show that with the proposed speed regulation strategy, the torque ripple is suppressed from 33.3% to 20.1%, and that with the proposed suppression strategy in commutation, the torque ripple is suppressed further to 5.3%.

A new approach for commutation torque ripple reduction of FPGA based brushless DC motor with outgoing phase current control

ABSTRACT Brushless Direct Current Motor (BLDC) has been deployed across several kinds of applications. However, attaining a smooth torque ripple with fast response is relatively tough, as usually this is based on the varied slew rate line current in the commutation period. Hysteresis Current control has been widely used in earlier works for the maintaining incoming and outgoing phase current at the same rate throughout the commutation period. Additionally, this also helps in reducing the commutation torque ripple and delivers successful commutation. The proposed work here uses a relatively simple control technique that is primarily derived on the basis Outgoing-phase Current Discharge Hysteresis Control (OCDHC). This has been characterized to produce low response time and reduced torque ripple which has been suggested to execute in both conduction and commutation intervals. For the implementation of digital controller, we chose Xilinx Spartan 6 FPGA board. The digital controller algorithm is written using VHDL and is dumped on the FPGA. For this purpose we use Xilinx ISE and iMPACT tools. FPGA receives hall sensor output and current from BLDC motor with reduced torque ripple and generates the gate pulses which drive the IGBT switches using OCDHC control. This condition shows that the performance of the system is not primarily based on the motor parameters, excluding the stator resistance. Lastly, results obtained from the simulation and experimental results validate the significance of the proposed control technique based on response time at load conditions that vary at different junctures.

Research on Novel Direct Instantaneous Torque Control Strategy for Switched Reluctance Motor

In order to solve the frequent problem of breaking shaft in the starter/generator system of switched reluctance motor, a novel Direct Instantaneous Torque Control (DITC) is proposed to control the torque ripple in this paper. Instead of the hysteresis controller in traditional DITC, the PWM is introduced to modulate the torque deviation; the optimal switching signal is selected according to the PWM modulation signal and the sector where the rotor position is located. Based on the torque characteristic curves, the torque ripple during commutation period is analyzed and the compensation methods are proposed. Simulation results prove that the compensated PWM-DITC can suppress the torque ripple of switched reluctance motor effectively.

Improved PWM-OFF-PWM to Reduce Commutation Torque Ripple of Brushless DC Motor Under Braking Conditions

This paper proposes an improved PWM-OFF-PWM of the brushless DC motor under braking condition which can reduce commutation torque ripple. Compared with other brake modulation methods, PWM-OFF-PWM can restrain non-commutation torque ripple attributed to non-conductive freewheeling, while incapable of suppressing commutation torque ripple at low speeds effectively. Therefore, to solve commutation torque ripple caused by the turn-off time being shorter than turn-on time, an improved PWM-OFF-PWM is proposed in this paper. Moreover, to describe the influence factors of commutation torque ripple, the formulas of the duty cycle of switching tube in the commutation period and that during non-commutation period is derived. We can conclude from mathematical analysis that when duty cycles of outgoing and incoming phases satisfy derived formula, the non-commutation current in commutation interval will be more stable, which can contribute to suppress the commutation torque ripple at low speed under PWM-OFF-PWM mode and to improve the operation stability of BLDCM. The correctness and feasibility of the proposed method can be proved by simulation and experimental results.

High Load Fast Startup Sensorless Control of Wheel BLDC Motor with Line-to-Line Back EMF Extraction Using Least Pth-Norm IIR Digital Filter

In this paper, an effective scheme of on-load startup with reduced current has been proposed for BLDC motor and the steady as well as dynamic performance in all four quadrants was verified. Hysteresis band-limited back EMF noise provides the starting pulses, the frequency of which depends on the threshold factor in speed proportional threshold. Scheme is quite fast, comparatively to the state-of-the art schemes of startup and less complex than time-consuming initial position detection (IPD) algorithm. Second-order least [Formula: see text]th-norm infinite impulse response (IIR) digital low pass filter realized in MATLAB/Simulink has been used for extraction of line-to line back EMF from line-to-line terminal voltages measured with two voltage sensors. Proposed filter has wide flexibility of online variation of cut-off frequency, gain and phase without any circuit-based modification due to variability of filter coefficients. This enables the smooth filtering with minimized phase delay in low speed range irrespective of any duty cycle and PWM frequency. Linear compensation of phase error or phase advancement for desired current profile can easily be achieved by the varying the threshold factor. In this experiment, the threshold factor of 1/1460 has been found most suitable for smooth sensorless startup without jerk, vibration and reverse rotation, as the motor operates in advanced mode with this value. First, the performance of Hall sensor-based drive was studied using open loop variable duty cycle speed control. The controller was designed in MATLAB/Simulink platform and implemented using TMS320F28069M DSP control stick with Code composer Studio V5. Later on, a complete controller for proposed sensorless scheme was developed in MATLAB/Simulink environment and was implemented using NI-PCI6221 Controller installed in PC. The proposed sensorless drive has been found capable of operating at very low speed of 50[Formula: see text]rpm in voltage control mode and 85[Formula: see text]rpm in current chopping PWM mode. Approximately 85[Formula: see text]ms less time was taken by sensorless drive to reach the same speed when compared with Hall-based control for identical loading. Also less overshoots during startup was observed. Overlap time of 0.05[Formula: see text]ms between phase currents has been achieved during commutation period.

A Commutation Torque Ripple Suppression Strategy for Brushless DC Motor Based on Diode-Assisted Buck–Boost Inverter

Based on diode-assisted buck–boost inverter, this paper proposes a new commutation torque ripple suppression strategy for brushless dc motor (BLDCM). Four types of switching vectors are constructed, according to the working pattern of the diode-assisted inverter and the operation mode of the BLDCM. Moreover, the effects of switching vector combination on commutation torque ripple suppression and motor speed regulation are analyzed in the commutation and normal conduction periods, respectively. Based on this analysis, the duration of switching vectors within each modulation cycle is derived and the sequence of vectors is arranged at the same time in these two periods. The proposed method can effectively suppress the commutation torque ripple over the full speed range by unified switching vectors during the commutation period, without needing to switch control strategies according to the speed range. In addition, the increase of the voltage stress of switching devices in the inverter bridge can be avoided by designing the duration and sequence of switching vectors during the commutation and normal conduction periods. The effectiveness of the presented method is validated by the experimental results.

Commutation Torque Ripple Reduction for Brushless DC Motor Based on an Auxiliary Step-Up Circuit

There exists torque ripple in the commutation process of brushless DC motor (BLDCM), which seriously restricts its application in the high-performance field. This paper proposes an auxiliary step-up circuit to suppress the commutation torque ripple of BLDCM, and the auxiliary step-up circuit consists of a transformer, a capacitor and a switch circuit. For effective suppression of the commutation torque ripple, the capacitor is charged in the non-commutation period. When the commutation occurs, the charged capacitor is added on the power source through a switch circuit to step up the dc-bus voltage in the commutation period, and the three-phase inverter is regulated to make the motor’s input voltage is equal to four times the back electromotive force (back EMF) amplitude. The auxiliary step-up circuit only transfers partial power required in the commutation process of the motor, and the capacity of the power components is reduced accordingly. The inductive energy stored in the transformer is returned to the power source in each switching cycle, which improves the energy utilization rate. In addition, this method can also shorten the commutation time. The validity and effectiveness of the proposed method is verified through experimental results.

Commutation Torque Ripple Suppression Strategy for Brushless DC Motors With a Novel Noninductive Boost Front End

This paper first presents a novel boost front end simply with a diode, a MOSFET, and a DC-link capacitor. Without extra inductors or other power components, the boost font end could boost the capacitor voltage with the motor stator inductances, thus reducing the influence of the limited DC-link voltage on commutation torque ripple reduction to a large extent. A unified commutation torque ripple suppression strategy is further proposed with the front end adopted based on the analysis about the effects of four switching vectors on motor speed regulation and DC-link capacitor voltage regulation. The proposed strategy can boost the DC-link capacitor voltage via properly selection of switching vectors under the premise of guaranteeing normal speed regulation in noncommutation period, and reduce both the commutation torque ripple and commutation time by two consistent switching vectors with the boosted DC-link capacitor voltage in commutation period. Finally, the proposed method is theoretically analyzed with respect to the capacitance selection and the boot capacity of noninductive boost front end. The correctness of the analysis and the effectiveness of the presented method are validated by the experimental results.

High-Precision Sensorless Drive for High-Speed BLDC Motors Based on the Virtual Third Harmonic Back-EMF

In order to improve the performance of the high-speed brushless direct current motor drives, a novel high-precision sensorless drive has been developed. It is well known that the inevitable voltage pulses, which are generated during the commutation periods, will impact the rotor position detecting accuracy, and further impact the performance of the overall sensorless drive, especially in the higher speed range or under the heavier load conditions. For this reason, the active compensation method based on the virtual third harmonic back electromotive force incorporating the SFF-SOGI-PLL (synchronic-frequency filter incorporating the second-order generalized integrator based phase-locked loop) is proposed to precise detect the commutation points for sensorless drive. An experimental driveline system used for testing the electrical performance of the developed magnetically suspended motor is built. The mathematical analysis and the comparable experimental results have been shown to validate the effectiveness of the proposed sensorless drive algorithm.

Influence of DC-Link Voltage on Commutation Torque Ripple of Brushless DC Motors with Two-Segment Pulse-width Modulation Control Method

The commutation process causes current ripple to be generated in the drive system of brushless DC (BLDC) motor. This, in turn, leads to output torque ripple. Mechanical vibration and acoustic noise are its influences which are undesirable phenomenon in some applications. A new method is presented in this paper which reduces torque ripple and commutation period in the entire range of motor speed. This method is designed and implemented based on two-segment pulse-width modulation (PWM) and DC-link voltage doubling during commutation. Based on the presented theory and given the influence of DC-link voltage on ripple magnitude, some experiments are carried out in which simultaneous association of the above mentioned factors in reducing current ripple and commutation time in the entire speed range of rotor has been proved. The experimental results show that the current ripple magnitude in high speed range is almost 20 times less than conventional method based on H-PWM_L-ON technique.

A Novel Method of Reducing Commutation Torque Ripple for Brushless DC Motor Based on Cuk Converter

In this paper, based on Cuk converter, a novel commutation torque ripple reduction strategy is proposed for the brushless DC motor. Output modes (buck–boost mode and boost mode) of the Cuk converter during the commutation period and normal conduction period are altered by designing a mode selection circuit, which can reduce commutation torque ripple over the entire speed range. During the commutation period, Cuk converter operates in the boost mode to step up the input voltage of three-phase bridge inverter and then meet the voltage demand of commutation period, such that the commutation torque ripple can be reduced by keeping the noncommutated current steady. In order to improve the utilization rate of the converter, during the normal conduction period, Cuk converter operates in the buck–boost mode and the input voltage of three-phase bridge inverter is regulated by adopting the pulse amplitude modulation (PAM) method without the inverter pulse width modulation chopping, which can reduce the voltage spike damage to the motor windings caused by turn-on/off of MOSFET in the inverter and simplify the program of modulation method further. The experimental results verify the correctness of the theory and the effectiveness of the proposed approach.

A Torque Control Strategy for Torque Ripple Reduction of Brushless DC Motor With Nonideal Back Electromotive Force

This paper proposes a new torque control strategy to reduce torque ripple of brushless dc motor. All possible combinations of terminal voltages are obtained from different switching states of the inverter during normal conduction period and commutation period. Moreover, the expressions of torque variation rates, corresponding to different terminal voltages, are derived to analyze the sign and the magnitude of the torque variation rates. Based on this analysis, two switching tables with main vector (MV) and subsidiary vector (SV) in these two periods are established, respectively. Through the combined effect of MV and SV in each control cycle, the torque ripple caused by both nonideal back electromotive force and current commutation can be reduced effectively. Meanwhile, dynamic performance of torque and switching times are taken into account. Especially in the commutation period, a unified vector selection table is applied over the entire speed range without distinguishing high speed and low speed. Finally, the effectiveness of the proposed strategy is verified by experimental results.

Commutation Phenomena and Brush Wear of DC Motor at High Speed Rotation

Many DC commutator motors are widely used in automobiles. In recent years, as compact and high output DC motors have been developed due to advanced technology, the faster the rotational speed is required and the commutation arc causes a high rate of wear/erosion of brush and commutator. Therefore, it is important how the motor speed influences commutation phenomena such as arc duration, residual current and erosion and wear of commutator and brush in order to achieve high reliability and extensive lifespan. In this paper waveforms of commutation voltage and current are measured at the rotation speed of 1000 to 5000min-1and the relation between rotation speed and arc duration / residual current is obtained. In addition long term tests are carried out at the rotation speed of 1000 to 5000min-1 the change of arc duration and effective commutation period is examined during the test of 20hours. Further, brush wear is evaluated by the difference of brush length between before and after test. Consequently, it can be made clear that as the speed increases, the effective commutation period decreases and the arc duration is almost same at the speed up to 3000min-1 and is around 42µsec.