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Five-phase induction machines are generally modeled using multiple dq planes or using a phase variable model. This paper considers modeling five-phase induction machines using a voltage-behind-reactance (VBR) configuration. This c...
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Five-phase induction machines are generally modeled using multiple dq planes or using a phase variable model. This paper considers modeling five-phase induction machines using a voltage-behind-reactance (VBR) configuration. This configuration lends itself suitable for time-domain circuit-based simulators as the MATLAB/Simulink SimPowerSystems (SPS) toolbox. The stator electrical dynamics are represented in five-phase coordinates, while the rotor electrical circuit is modeled using rotor flux linkage as the state variable and expressed in the dq stator reference frame. The VBR model is equivalent to a conventional dq model; however, it facilitates the connection of an external inductance without affecting numerical accuracy and calculation efficiency. It also facilitates the simulation of different winding connections, series-connected multimotors, and open phase(s) conditions. The model is, first, derived for a magnetically linear system and then it is extended to include the effect of magnetic saturation. The flux correction method is used to represent the effect of magnetic saturation with a simple modification to represent the effect of cross coupling between fundamental and third sequence planes due to saturation effect. The dynamic cross saturation is considered by adding compensating terms that depend on magnetizing inductance variation. The proposed model is experimentally verified using a prototype 1.5-hp five-phase induction machine under different operating conditions.
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Explicit nonasymptotic upper bounds on the sizes of multiple-deletion correcting codes are presented. In particular, the largest single-deletion correcting code for $q$-ary alphabet and string length $n$ is shown to be of size at...
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Explicit nonasymptotic upper bounds on the sizes of multiple-deletion correcting codes are presented. In particular, the largest single-deletion correcting code for $q$-ary alphabet and string length $n$ is shown to be of size at most $ {{ q^{n}-q}over { (q-1)(n-1)}}$. An improved bound on the asymptotic rate function is obtained as a corollary. Upper bounds are also derived on sizes of codes for a constrained source that does not necessarily comprise of all strings of a particular length, and this idea is demonstrated by application to sets of run-length limited strings. The problem of finding the largest deletion correcting code is modeled as a matching problem on a hypergraph. This problem is formulated as an integer linear program. The upper bound is obtained by the construction of a feasible point for the dual of the linear programming relaxation of this integer linear program. The nonasymptotic bounds derived imply the known asymptotic bounds of Levenshtein and Tenengolts and improve on known nonasymptotic bounds. Numerical results support the conjecture that in the binary case, the Varshamov–Tenengolts codes are the largest single-deletion correcting codes.
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A highly sensitive CMOS-based sensing system is proposed for permittivity detection and mixture characterization of organic chemicals at microwave frequencies. The system determines permittivity by measuring the frequency differen...
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A highly sensitive CMOS-based sensing system is proposed for permittivity detection and mixture characterization of organic chemicals at microwave frequencies. The system determines permittivity by measuring the frequency difference between two voltage-controlled oscillators (VCOs); a sensor oscillator with an operating frequency that shifts with the change in tank capacitance due to exposure to the material under test (MUT) and a reference oscillator insensitive to the MUT. This relative measurement approach improves sensor accuracy by tracking frequency drifts due to environmental variations. Embedding the sensor and reference VCOs in a fractional-$N$ phase-locked loop (PLL) frequency synthesizer enables material characterization at a precise frequency and provides an efficient material-induced frequency shift read-out mechanism with a low-complexity bang–bang control loop that adjusts a fractional frequency divider. The majority of the PLL-based sensor system, except for an external fractional frequency divider, is implemented with a 90-nm CMOS prototype that consumes 22 mW when characterizing material near 10 GHz. Material-induced frequency shifts are detected at an accuracy level of 15 ${hbox{ppm}}_{rm rms}$ and binary mixture characterization of organic chemicals yield maximum errors in permittivity of ${<}$1.5%.
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In this paper, harmonic rejection (HR) mixing techniques to obtain a high level of HR are described. This is achieved by reducing the sensitivity to mismatches in devices operating at high frequencies. A design fabricated in a 110...
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In this paper, harmonic rejection (HR) mixing techniques to obtain a high level of HR are described. This is achieved by reducing the sensitivity to mismatches in devices operating at high frequencies. A design fabricated in a 110-nm CMOS process rejects up to the first 14 local oscillator (LO) harmonics and achieves third, fifth, and seventh HR ratios in excess of 52, 54, and 55 dB, respectively, without any calibration or trimming. This mixer also rejects flicker noise and has improved quadrature matching and IIP2 performance. By using a clock $N$ times the desired LO frequency, this scheme rejects the $(N-1)$th LO harmonic only by an amount of $20log (N-1)~hbox{dB}$. A new technique is presented that enables better HR for the $(N-1)$th harmonic while preserving the level of rejection for other harmonics. This mixer fabricated in a 55-nm standard CMOS process has a programmable number of 8, 10, 12, or 14 mixer phases and achieves an improvement of 29 dB for the $(N-1)$th harmonic while achieving 52 dB of rejection for the third harmonic. It also rejects flicker noise and has an IIP2 performance of 68 dBm.
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This paper introduces a new Pulse-Width Modulation (PWM) control scheme for buck regulators that combines phase chopping with frequency hopping to achieve spur-free operation while delivering low output noise floor with no subharm...
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This paper introduces a new Pulse-Width Modulation (PWM) control scheme for buck regulators that combines phase chopping with frequency hopping to achieve spur-free operation while delivering low output noise floor with no subharmonics due to hopping. The proposed regulator hops between two, four, or eight switching frequencies, but chops their phases to fully eliminate spurs, even with only two frequencies. Peaking in the noise floor around the eliminated spurs is minimized by hopping as fast as every switching cycle, and by spacing the frequencies 0.5 MHz apart. This results in less than 1.7% drop in the regulator's efficiency and less than 4 mV increase in the voltage ripple. Implemented in standard 0.35-$mu{rm m}$ CMOS technology, the proposed regulator's area and power overhead beyond conventional single-switching-frequency design is only 8% and 3%, respectively. With a spur-free spectrum and low noise floor across all frequencies, the proposed architecture can serve as a low-noise regulator for powering noise-sensitive loads without post linear regulation or additional passive filtering. Moreover, spur-free operation facilitates its integration in mixed-signal systems on chip without interfering with sensitive circuits that share the same substrate or power rails. The proposed architecture is also a good candidate for implementing class-D amplifiers, as it preserves the control loop's linearity.
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In robotics and augmented reality applications, model-based 3-D tracking of rigid objects is generally required. With the help of accurate pose estimates, it is required to increase reliability and decrease jitter in total. Among ...
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In robotics and augmented reality applications, model-based 3-D tracking of rigid objects is generally required. With the help of accurate pose estimates, it is required to increase reliability and decrease jitter in total. Among many solutions of pose estimation in the literature, pure vision-based 3-D trackers require either manual initializations or offline training stages. On the other hand, trackers relying on pure depth sensors are not suitable for AR applications. An automated 3-D tracking algorithm, which is based on fusion of vision and depth sensors via extended Kalman filter, is proposed in this paper. A novel measurement-tracking scheme, which is based on estimation of optical flow using intensity and shape index map data of 3-D point cloud, increases 2-D, as well as 3-D, tracking performance significantly. The proposed method requires neither manual initialization of pose nor offline training, while enabling highly accurate 3-D tracking. The accuracy of the proposed method is tested against a number of conventional techniques, and a superior performance is clearly observed in terms of both objectively via error metrics and subjectively for the rendered scenes.
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An RF duplexer has been fabricated on a CMOS IC for use in 3G/4G cellular transceivers. The passive circuit sustains large voltage swings in the transmit path, and isolates the receive path from the transmitter by more than 45 dB ...
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An RF duplexer has been fabricated on a CMOS IC for use in 3G/4G cellular transceivers. The passive circuit sustains large voltage swings in the transmit path, and isolates the receive path from the transmitter by more than 45 dB across a bandwidth of 200 MHz in 3G/4G bands I, II, III, IV, and IX. A low noise amplifier embedded into the duplexer demonstrates a cascade noise figure of 5 dB with more than 27 dB of gain. The duplexer inserts 2.5 dB of loss between power amplifier and antenna.
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摘要 :${rm CO}_{2}$ is a possible alternative to ${rm SF}_{6}$—which has a high global warming potential—as the interruption medium in gas circuit breakers. The performance of ${rm CO}_{2}$ is investigated in this paper by carrying ...
展开${rm CO}_{2}$ is a possible alternative to ${rm SF}_{6}$—which has a high global warming potential—as the interruption medium in gas circuit breakers. The performance of ${rm CO}_{2}$ is investigated in this paper by carrying out experiments in representative test devices and by performing computational fluid dynamic (CFD) simulations; some comparisons with ${rm SF}_{6}$ and air are given. It is found that the thermal interruption performance of ${rm CO}_{2}$ is lower than that of ${rm SF}_{6}$, but higher than that of air. The measured dielectric recovery after arcing is compared for ${rm CO}_{2}$ and ${rm SF}_{6}$; a streamer model is used to calculate the breakdown voltage in ${rm CO}_{2}$; good agreement with measurement is found. The speed of sound and the adiabatic coefficient, important parameters that influence pressure buildup and gas flow, are compared for ${rm SF}_{6}$, ${rm CO}_{2}$, and air. CFD simulations of the pressure buildup in ${rm CO}_{2}$ and ${rm SF}_{6}$ both illustrate the qualitative differences between the two and show good agreement with measurements.
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Indirect time of flight cameras are increasingly being used in a variety of applications to provide real-time full field of view range measurements. Current generation cameras suffer from systematic linearity errors due to the inf...
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Indirect time of flight cameras are increasingly being used in a variety of applications to provide real-time full field of view range measurements. Current generation cameras suffer from systematic linearity errors due to the influence of harmonics in the system and motion errors due to the requirement of taking multiple measurements. This paper demonstrates that replacing the standard phase detection algorithm with the windowed discrete Fourier transform can improve the root mean square (RMS) axial motion error with distance from $0.044pm0.002~{rm m}$ to $0.009pm 0.004~{rm m}$ and the range from $0.112pm 0.007~{rm m}$ to $0.03pm 0.01~{rm m}$ for an object with a velocity of 2 m/s using a measurement time of 125 ms. This algorithm also improves the linearity of the camera by removing systematic errors due to harmonics, decreasing the RMS linearity error from $0.018pm 0.002~{rm m}$ to $0.003pm 0.001~{rm m}$. This paper establishes the robustness of the windowed discrete Fourier transform, demonstrating that it effectively eliminates axial motion error over a variety of velocities and modulation frequencies. The potential for tailoring phase detection algorithms to specific applications is also demonstrated.
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This paper presents the concept of dynamic reconfiguration between two sliding mode current controllers for synchronous motor drives. The first one is a Direct Sliding Mode (DSM) current controller, which is based on a switching t...
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This paper presents the concept of dynamic reconfiguration between two sliding mode current controllers for synchronous motor drives. The first one is a Direct Sliding Mode (DSM) current controller, which is based on a switching table synthesized via sliding mode theory. The second one is an Indirect Sliding Mode (ISM) current controller that computes a reference voltage vector via sliding mode theory. The computed reference voltage is then applied to the terminals of the synchronous machine through a Pulse Width Modulation (PWM) process. This item studies and discusses the reconfiguration criteria and presents the main interest of using FPGA digital solutions for dynamic reconfiguration process implementation between the two sliding mode current controllers. Numerous experimental results are presented in order to confirm the interest and performances of the proposed reconfigurable sliding mode current controller.
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