Motion control with permanent-magnet AC machines

Motion control techniques have been developed to exploit the high efficiency and extremely fast dynamic response capabilities of permanent-magnet AC (PMAC) machines. Control techniques are reviewed separately for the two major classes of PMAC machines referred to as trapezoidal (i.e., brushless DC) and sinusoidal machines. While trapezoidal PMAC machine drives are distinguished by their controls simplicity and minimal sensor requirements, sinusoidal PMAC machine drives offer opportunities for extremely smooth torque production and extended high-speed operating ranges. Advanced PMAC machine control topics including sensor elimination techniques and robust servocontrol algorithms are reviewed, concluding with a discussion of PMAC machine drive application trends     

Planar-integrated talbot array illuminators

We demonstrate the planar integration of Talbot array illuminators designed to generate one-dimensional spot arrays. The array illuminator basically consists of a phase grating and a cylindrical diffractive lens integrated as a single diffractive optical element onto a transparent glass substrate. We discuss various design aspects, and we focus on problems typical for planar-integrated free-space optics like the tilted optical axis of the system. Experimental results and measurements, which were obtained from planar-integrated setups fabricated as surface-relief structures on a transparent glass substrate by use of standard photolithography, are included.     

Optical multiplexing techniques for photonic Clos networks in High Performance Computing Architectures

Future high-performance computing (HPC) architectures will consist of whole parallel computing systems integrated on chip-level and boards mounted with lots of computing chips and chip-external main memory. Photonic networks on board and photonic network on chips (NoCs) offer the potential to fulfill the high bandwidth requirements in such systems. In addition they need less power, offer better EMC capabilities and can reduce cabling effort compared to electronic networks. Due to their non-blocking property Clos networks are frequently used in HPC architectures. Therefore we investigated how a photonic on-board Clos network can be realized using Coarse Wavelength-Division-Multiplexing (CWDM) techniques with state-of-the art components based on fiber technology. In addition we present a new photonic Clos NoC architecture based on Wavelength Interchanging (WI) elements, optical waveguide structures, mode-locked laser sources, nanophotonic microrings and passive optical deflection elements to reduce the number of switches. We discuss the benefits and drawbacks for using different optical technologies for such an architecture.     

Magnet-flux-ing control of interior PM Machine drives for improved steady-state response to short-circuit faults

This paper proposes a control method to the magnet flux in an interior permanent-magnet (IPM) motor following short-circuit-type faults in either the inverter drive or motor stator windings. Phase-based control is employed to implement the flux-ing-control method so that it is possible to take advantage of a zero-sequence current in order to minimize the current in the shorted phase. It is shown that phase-based control results in a smaller induced current than when employing a synchronous-frame dq0 current regulator. The induced torque is also less than that when employing a purposely commanded symmetrical short circuit in response to a short-circuit-type fault. In the paper, the complete magnet-flux-ing-control algorithm is derived with reference to the proposed phase-current-control method. The impact of controlling the zero-sequence current on the resulting phase currents is presented. Both simulation and experimental results are presented, verifying the operation of the proposed methods.     

Flux-Weakening Regime Operation of an Interior Permanent-Magnet Synchronous Motor Drive

The interior permanent magnet (IPM) synchronous motor is compatible with extended-speed-range constant-power operation by means of flux-weakening control. Flux weakening uses stator current components to counter the fixed-amplitude magnetic airgap flux generated by the rotor magnets, performing a role similar to field weakening in a separately excited dc motor. The nature of current regulator saturation caused by the finite inverter dc source voltage is described, marked by premature torque and power degradation at high speeds in the absence of flux-weakening control. This is followed by presentation of a new flux-weakening control algorithm developed as a modification of an established feedforward IPM torque control algorithm described previously in the literature. Attractive features of this new algorithm include smooth drive transitions into and out of the flux-weakening mode, fast response, as well as automatic adjustment to changes in the dc source voltage. Simulation and empirical test results from a 3-hp laboratory IPM motor drive are used to confirm the constant-power operating envelope achieved using the new flux-weakening control algorithm.     

Six-Phase Voltage Source Inverter Driven Induction Motor

A six-phase six-step voltage-fed induction motor is presented. The inverter is a transistorized six-step voltage source inverter, while the motor is a modified standard three-phase squirrel-cage motor. The stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees. A model for the system is developed to simulate the drive and predict its performance. The simulation results for steady-state conditions and experimental measurements show very good correlation. It is shown that this winding configuration results in the elimination of all air-gap flux time harmonics of the order (6v ±1, v = 1,3,5,...). Consequently, all rotor copper losses produced by these harmonics as well as all torque harmonics of the order (6v, v = 1,3,5,...) are eliminated. A comparison between-the measured instantaneous torque of both three-phase and six-phase six-step voltage-fed induction machines shows the advantage of the six-phase system over the three-phase system in eliminating the sixth harmonic dominant torque ripple.     

Focusing analysis of the pinhole photon sieve: individual far-field model

Recently, a new class of diffractive optical element called a photon sieve, which consists of a great number of pinholes, was developed for the focusing and imaging of soft x rays. In terms of the closed-form formula for the far field of individual pinholes and the linear superposition principle, we present a simple yet accurate analytical model for the focusing of the pinhole photon sieve. This model is applicable to arbitrary paraxial illumination with arbitrary complex amplitude distribution at the photon sieve plane. We check the validity range of this model by comparing it with the exact Fresnel diffraction integral. Some special problems, such as the individual quasi-far-field correction for very large pinholes and the related phase shift induced by this correction, are also discussed.     

Iterative optimization of phase-only diffractive optical elements based on a lenslet array

We describe the design of Fourier-type phase-only array generators. The numerical optimization employs the Fienup algorithm, where the parageometric design of the phase retardation profile, with the form of a lenslet array, is used as the initial guess of the optimization process. This approach provides designs with high performance that can be obtained with comparatively low computing effort. This is particularly true for elements generating large spot arrays. For symmetric reconstruction fields, the optimized phase profile typically has the same symmetry as that for the reconstruction field and can be easily unwrapped.     

Compact planar-integrated optical correlator for spatially incoherent signals

A new, to our knowledge, approach for the planar integration of optical correlators is demonstrated. A VanderLugt-type architecture was used to allow the processing of the spatially incoherent signals of active optoelectronic smart-pixel-device arrays. In a folded optical system all passive components were implemented as a single multiple-phase-level element. The relations among the spatial resolution, the light efficiency, and the system design parameters are derived. High signal quality and low noise levels were achieved experimentally.     

Planar-integrated optical vector-matrix multiplier

We present the design of a planar-integrated optoelectronic vector-matrix multiplier. The inherent parallel-processing potential is fully exploited by optical implementation of multiplications and summations. Planar integration makes the free-space optical system compatible with electronic VLSI technologies. It is composed of phase-only diffractive optical elements, which implement lens and multiple-beam-splitter functions. A demonstrator version of the optical system for a matrix of size 10 x 10 was fabricated on quartz glass by means of multimask lithography and reactive ion etching. It shows low cross talk and good uniformity of the signals.