Showing papers on "Harmonic published in 1985"

Dynamic Models for Control System Design of Integrated Robot and Drive Systems

Abstract: The design of high performance motion controls for industrial robots is based on accurate models for the robot arm and drive systems. This paper presents analytical models and experimental data to show that interactions between electromechanical drives coupled with compliant linkages to arm link drive points are of fundamental importance to robot control system design. Flexibility in harmonic drives produces resonances in the 5 Hz to 8 Hz range. Flexibility in the robot linkages and joints connecting essentially rigid arm members produces higher frequency modes at 14 Hz and 40 Hz. The nonlinear characteristics of the drive system are modeled, and compared to experimental data. The models presented have been validated over the frequency range 0 to 50 Hz. The paper concludes with a brief discussion of the influence of model characteristics on motion control design.

Relative dominance of individual partials in determining the pitch of complex tones

Abstract: These experiments were conducted to determine the dominance of each partial in determining the residue pitch of a complex tone. Subjects were required to make pitch matches to a complex tone which had one partial slightly mistuned from its ‘‘correct’’ harmonic value. The shift in residue pitch was measured as a function of the frequency shift of the harmonic, for each harmonic in turn. For mistunings up to ±2%–3% the shift in residue pitch was approximately a linear function of the shift in the harmonic, but for greater mistunings the shift in residue pitch was reduced. The degree to which a given harmonic can influence residue pitch gives a measure of the dominance of that harmonic. The dominant harmonics were always contained within the lowest six harmonics (for fundamental frequencies of 100, 200, and 400 Hz), but there were marked individual differences in the exact distribution of dominance across harmonics. The level of a harmonic relative to adjacent harmonics can have a significant effect on its dominance. The implications of the results for theories of pitch perception are discussed.

Intermodulation and harmonic distortion in InGaAsP lasers

Abstract: A theoretical and experimental study is presented of intermodulation and harmonic distortion in high-speed 1.3 and 1.5 ?m InGaAsP lasers modulated at frequencies up to 8 GHz. It is found that all lasers measured, including Fabry-Perot and distributed feedback lasers, generate approximately the same distortion levels for a given modulation depth and relaxation resonance frequency. There are minor differences between lasers, which result from differences in the damping of the small-signal resonance peak.

Thresholds for the detection of inharmonicity in complex tones

Abstract: Thresholds were measured for the detection of inharmonicity in complex tones. Subjects were required to distinguish a complex tone whose partials were all at exact harmonic frequencies from a similar complex tone with one of the partials slightly mistuned. The mistuning which allowed 71% correct identification in a two‐alternative forced‐choice task was estimated for each partial in turn. In experiment I the fundamental frequency was either 100, 200, or 400 Hz, and the complex tones contained the first 12 harmonics at equal levels of 60 dB SPL per component. The stimulus duration was 410 ms. For each fundamental the thresholds were roughly constant when expressed in Hz, having a mean value of about 4 Hz (range 2.4–7.3 Hz). In experiment II the fundamental frequency was fixed at 200 Hz, and thresholds for inharmonicity were measured for stimulus durations of 50, 110, 410, and 1610 ms. For harmonics above the fifth the thresholds increased from less than 1 Hz to about 40 Hz as duration was decreased from 1610–50 ms. For the lower harmonics (up to the fourth) threshold changed much less with duration, and for the three shorter durations thresholds for each duration were roughly a constant proportion of the harmonic frequency. The results suggest that inharmonicity is detected in different ways for high and low harmonics. For low harmonics the inharmonic partial appears to ‘‘stand out’’ from the complex tone as a whole. For high harmonics the mistuning is detected as a kind of ‘‘beat’’ or ‘‘roughness,’’ presumably reflecting a sensitivity to the changing relative phase of the mistuned harmonic relative to the other harmonics. The results are discussed in relation to theories of pitch perception.

A multifrequency phase fluorometer using the harmonic content of a mode-locked laser

Abstract: We describe the construction and operation of a cross-correlation phase and modulation fluorometer which uses the harmonic content of a high repetition rate mode-locked laser as the excitation source. A mode-locked argon ion laser is used to synchronously pump a dye laser. The pulse train output from the dye laser is amplitude modulated by an acousto-optic modulator and then frequency doubled with an angle tuned frequency doubler. With the particular dye utilized in these studies, the ultraviolet light obtained was continuously tunable over the range 280-310 nm. In the frequency domain the high repetition rate pulsed source gives a large series of equally spaced harmonic frequencies. The frequency spacing of the harmonics is determined by the repetition frequency of the laser. Amplitude modulation of the pulse train permits variation of the frequency quasi-continuously from a few hertz to gigahertz. Use of cross-correlation techniques permits precise isolation of individual frequencies. The cross...

PWM Control Techniques for Rectifier Filter Minimization

Abstract: Minimization of input/output filters is an essential step towards manufacturing compact low-cost static power supplies. Three PWM control techniques that yield substantial filter size reduction for three-phase (self-commutated) rectifiers are presented and analyzed. Filters required by typical line-commutated rectifiers are used as the basis for comparison. Moreover, it is shown that in addition to filter minimization two of the proposed three control techniques improve substantially the rectifier total input power factor.

Angular-gain spectrum of free-electron lasers

Abstract: The theory of free-electron lasers is extended to include the new coupling between an electron beam and optical wave propagating at an angle theta in an arbitrary harmonic. The coupling allows the laser to be tuned to a wider range of wavelengths and to include the effects of emittance in the electron beam. The formulation of the results in terms of coupling constants means that the existing knowledge of high gain, low gain, weak optical fields, strong optical fields, and short pulses in free-electron lasers can be immediately generalized to off-axis propagation in an arbitrary harmonic.

Evidence for ultrasonic finite‐amplitude distortion in muscle using medical equipment

Abstract: Finite‐amplitude distortion of ultrasonic waves from medical equipment has been observed to occur following transmission through calf muscle in human volunteers. Measurements were made using both dynamic pulse‐echo imaging equipment and physiotherapy equipment. In both cases irradiation was carried out under operating conditions commonly used clinically. Pressure waveforms were measured at the skin surface using a broadband polyvinylidene difluoride membrane hydrophone. Using a pulsed, weakly focused 2.5‐MHz beam with input peak pressure of 0.8 MPa and a pressure gain of 5.3 at the focus, the mean second harmonic peak magnitude (16 measurements) was 17 dB below the fundamental peak. A 1.1‐MHz continuous wave therapy set with input peak pressure of 0.5 MPa showed mean second harmonic magnitude 23 dB below the fundamental.

A Harmonic Gradient Method for Unsteady Supersonic Flow Calculations

Abstract: An accurate and effective method for calculations of unsteady three-dimensional supersonic flow has been developed. The present method is capable of handling general cases of planar, coplanar, and nonplanar wing planforms in the complete frequency domain. A harmonic-gradi ent potential model is provided for elementary doublet panels to be made compatible with the wave number generated. Consequently the number of panel elements required is least affected by the given Mach number and reduced frequency. Thus, the required panel number can be optimized to as few as 30, a fraction of the number required by the existing methods. To assess the accuracy and effectiveness of the present method, comparison with various available data is given. ACP h L m

A New Control of PWM Inverter Waveform for Minimum Loss Operation of an Induction Motor Drive

Abstract: A simplified method to calculate harmonic currents of an induction motor and optimum PWM switching patterns to minimize the harmonic loss are presented. Neglecting the harmonic iron loss, the harmonic loss of the motor is proportional to the square of the rms current. The waveform of the harmonic current is approximately equal to that of the leakage reactance applied to the same PWM voltage. Its approximation error is very small under normal operating condition. The main results obtained using these approximation are as follows: 1) the optimum PWM patterns of the pulsenumber from seven to 41; 2) how to choose the optimum pattern and calculate it by using a computer; 3) the effect of a resistance of the windings and skin effect of the secondary conductor; and 4) microcomputer PWM optimum voltage control schemes. Comparison with other controls is shown by using experimental and calculating results and confirms the effectiveness of this control scheme.

Harmonic Filters for Six-Phase and Other Multiphase Motors on Voltage Source Inverters

Abstract: Inverter-driven motors having five, six, or more phases have smaller torque pulsations and lower rotor I 2 R loss due to harmonics than do their three-phase counterparts. However, they generally have higher stator harmonic currents. For example, six-phase motors, supplied by a six step voltage source inverters have fifth and seventh harmonic currents which are from two to five times as large as in a comparable three-phase motor. If the motor has five or more phases, these currents can be substantially reduced by the harmonic filter described. The filter consists of transformer-like devices connected in the leads between the inverter and motor. The coils on these are interconnected in a prescribed way so that they add negligible impedance for fundamental currents, but they add considerable impedance for most harmonics. Since the filters do not affect fundamental current, they do not affect the speed-torque characteristic. These filters are described for any number of phases, and equations to determine their inductance values for the various harmonics are developed. Their effectiveness is demonstrated by experimental results.

Efficiency Optimal Control for AC Drives with PWM Inverters

Abstract: For electrical drives using pulsewidth modulation (PWM) inverters and ac motors, methods for efficiency optimal control (EOC) have been developed. They are based on the most complete motor models, including such features as rotor skin effect. Furthermore, new solutions for selected harmonic elimination (SHE) are given. These new solutions come close to EOC. Also, it has been found that EOC solutions (although basically load-dependent as opposed to SHE) do not vary much with the motor used or the motor model applied. Even using a simple R-L series circuit as motor model does not change the solutions much. It is found that using the solutions gained from such a simple model is not more than two points off the real optimum based on a very complete motor model. (For this definition, the absolute harmonic loss minimum is given as zero points, the overall maximum as 100 points with a linear scale in between.) Therefore, one can use one EOC solution for all motors with sufficient accuracy, or, as second best solution, the new form of SHE. Therefore, the EOC solution can be judged load-independent. The implementation by microprocessor-based systems is as easy for other PWM methods. EOC for three and five switching angles per quarter period is discussed, as well as the new solutions for SHE for up to nine angles.

Frequency domain solutions to multi-degree-of-freedom, dry friction damped systems under periodic excitation

Abstract: The anticipated low damping level in large space structures (LSS) has been a major concern for the designers of these structures. Low damping degrades the free response and complicates the design of shape and attitude controllers for flexible spacecraft. Dry friction damping has been considered as a means of increasing the passive damping of LSS, by placing it in the joints and connecting junctures of structures. However, dry friction is highly nonlinear and, hence, analytical investigations are difficult to perform. Here, a multi-harmonic, frequency domain solution technique is developed and applied to a multi-DOF, dry friction damped system. It is seen that the multi-harmonic method is much more accurate than traditional, one harmonic solution methods. The method also compares well with time integration. Finally, comparisons are made with experimental results.

Intensities in local mode overtone spectra: Dichloromethane and deuterated dichloromethane

Abstract: The liquid phase overtone spectrum of CD2Cl2 is measured in the CD‐stretching regions corresponding to ΔvCD=2 to 4, and the peaks are assigned in terms of the local mode model. Oscillator strengths are determined from these spectra and from the previously measured overtone spectra of CH2Cl2. A general theoretical description is developed for the overtone intensities in these molecules. The theory considers the functional dependence of the dipole moment on local coordinates, as determined from CNDO calculations and numerical differentiation techniques. Morse oscillator wave functions are used to describe the vibrational state within a symmetrized local mode description, and matrix elements of these wave functions are evaluated over powers of the local CH/CD coordinate. It is evident that any description of overtone intensities in terms of harmonic oscillator wave functions would be totally inadequate. Vibrational mixing of the symmetrized Morse oscillator product states is detemined from a harmonic couplin...

Analysis of PWM Techniques Using Uniform Sampling in Variable-Speed Electrical Drives with Large Speed Range

Abstract: In order to minimize motor losses and avoid torque pulsations in a variable-speed electric drives, it is necessary that, at low speeds, the output voltage of the inverter is characterized as far as possible by a sinusoidal shape with variable amplitude and frequency. To this aim, inverters controlled by pulsewidth modulation techniques are employed. In particular, when the subharmonic method is used in an asynchronous way utilizing the natural sampling, a dc component and subharmonics may be present, with dangerous consequences to the electric motor. To overcome these drawbacks, one can use a modulation method called ``uniform sampling,'' with symmetrical or asymmetrical modulation. Single-and three-phase analytical solutions to cover also overmodulation conditions are presented for uniform sampling, and comparisons are made between the natural and the symmetrical and asymmetrical uniform-sampling methods. The harmonic content obtainable under overmodulation conditions is investigated, useful information about the first-harmonic behavior is provided as a function of the modulating depth, and the influence of the displacement angle between the modulating and carrier waves on the first harmonic of the output voltage is evidenced particularly at low frequency values.

Method and apparatus for controlling PWM inverter

Abstract: In the control of a PWM inverter, there are various requirements such as decreasing a harmonic loss and acoustic noises, improving control response, optimizing switchings of the branches of the inverter in any condition, and simplification in circuit construction. In the present invention, the branches of the inverter are controlled in such that an evaluation function on the whole combination of the inverter and the load connected to the AC side of the inverter is made to be minimized.

A loss minimised sinusoidal PWM inverter

Abstract: Traditional PWM AC motor drives perform well over a wide speed range and have many positive features associated with their simplicity. However, the waveforms used are significantly less than ideal at high modulation depths and low switching rates, particularly with regard to harmonically induced motor losses. An improved strategy for digitally producing PWM based on conventional triangulation methods is presented. A novel technique for reducing the harmonic losses resulting from sinusoidal PWM waveforms is analysed in depth and realised on a 40 kVA inverter. Tests with this inverter on 7.5 kW and 15 kW motors confirm that the inverter's performance is significantly enhanced for certain operating conditions, without any significant sacrifice.

Beam‐driven ion cyclotron harmonic resonances in the terrestrial foreshock

Abstract: A terrestrial upstream wave event which demonstrates multiple, ion cyclotron harmonic resonances between the interplanetary wave population and an observed proton beam is analyzed. The techniques and parameters employed in the data analysis are discussed, including the use of differential and band-pass filters. An upstream wave event demonstrating multiple harmonic waves is examined, and the instability analysis relevant to the ion beam observations thought to be responsible for that event is discussed. It is shown that an observed bi-Maxwellian ion beam is capable of generating right and left-hand polarized waves through ion cyclotron harmonic resonance.

Jamming Avoidance in the Electric Fish Eigenmannia: Harmonic Analysis of Sexually Dimorphic Waves

Abstract: 1. The present report shows an intra specific, sexually dimorphic variation in harmonic content and waveform, as well as intensity, of the Electric Organ Discharges (EODs) in the green knife fish, Eigenmannia (Figs 2, 11). There is a close correlation between harmonic content of the EODs and waveform (as defined by the ratio of intervals between zero-crossings in the two half-waves of one EOD cycle; Fig. 3). The aim of the following experiments was to determine whether the fish are sensitive to differences in stimulus waveform or harmonic content. 2. Stimulation with electric fields of various waveforms but equal peak-to-peak amplitudes at frequencies close to the fish9s frequency elicited the Jamming Avoidance Response (JAR) which is an EOD frequency change increasing the frequency difference (Watanabe & Takeda, 1963). The strength of JARs to distorted square wave and sawtooth stimuli was 25% smaller than that elicited by sine wave stimuli (Fig. 6). Undistorted square waves elicited stronger responses than sine waves, while undistorted sawtooth waves were the least effective (Table 1). The differences in response strength were proportional to differences in the intensity of the fundamental frequency or first harmonic, f 1 , of the stimulus waveforms. 3. Subharmonic stimuli of nine artificial or synthesized natural waveforms at frequencies near one-half or one-third of the EOD resting frequency elicited responses only when a strong higher harmonic, or overtone, of the stimulus was close to the EOD fundamental frequency (Fig. 7). Stimuli of different waveforms, but identical spectral amplitudes, elicited similar responses not significantly different from each other, at stimulus frequencies near one-half (Table 3) and near the EOD resting frequency (Fig. 10). 4. Eigenmannia9s JARs to synthesized male EODs at frequencies close to the fish9s frequency were weaker than those to female EODs of equal peak-to-peak amplitude. The weaker response was proportional to the weaker intensity of the first harmonic of the male EOD (Fig. 12). A stimulus frequency near one-half of the EOD baseline frequency evoked opposite results, as the second harmonic, f 2 , of the male EOD was relatively four times stronger than that of the female EOD (Table 4).

Detection of harmonic burst signals

Abstract: The proposed procedure and the corresponding circuits for the recognition of a frequency from a set of possible input frequencies in the frame of a time-window interval seem to be advantageous as they lead to simpler hardware than the well-known energy detector. A unique feature is the single channel processing possibility. In addition the decision on the presence or absence of a given frequency is much faster than with a filter bank of resonators in a nearly lossless resonators. the frequency response is however not monotonic in frequency but has a somewhat periodic shape. the cases of the real lossy or unstable circuits are also dealt with. Some aspects of circuit realizations are given.

Fourth harmonic generation of a large-aperture Nd:glass laser.

Abstract: Basic properties of the fourth harmonic conversion of 1.053-μm laser radiation with KDP crystals are experimentally determined. Optimization of crystal thickness, based on numerical simulations is discussed. A large aperture conversion cell combining second and fourth harmonic generators has been designed. Overall conversion efficiencies (ω → 4ω) in excess of 40% have been achieved for incident laser intensities between 1 and 2.5 GW/cm2.