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Traditional analysis and design of induction machines have been largely based upon lumped-parameter models. An alternative tool used for field-based evaluations of an induction machine is the finite-element method. Although useful, its computational complexity limits its use as a design tool. In this paper, a field reconstruction (FR) method for induction machine simulation is introduced. The FR method utilizes a small number of finite-element evaluations to establish basis functions of normal and tangential flux densities. The basis functions are then used to estimate the magnetic field under arbitrary stator excitation. Using such a tool, evaluation of fields and forces produced by a machine under alternative excitation strategies can be explored efficiently. Moreover, alternative field-based derivation of stator/rotor excitation control can be explored. Index Terms--Field reconstruction (FR), finite element (FE), induction machine, Maxwell stress tensor, torque and radial force.

In order to improve the driving performance and the stability of electric vehicles (EVs), a new multimachine robust control, which realizes the acceleration slip regulation (ASR) and antilock braking system (ABS) functions, based on nonlinear model predictive (NMP) direct torque control (DTC), is proposed for four permanent magnet synchronous in-wheel motors. The in-wheel motor provides more possibilities of wheel control. One of its advantages is that it has low response time and almost instantaneous torque generation. Moreover, it can be independently controlled, enhancing the limits of vehicular control. For an EV equipped with four in-wheel electric motors, an advanced control may be envisaged. Taking advantage of the fast and accurate torque of in-wheel electric motors which is directly transmitted to the wheels, a new approach for longitudinal control realized by ASR and ABS is presented in this paper. In order to achieve a high-performance torque control for EVs, the NMP-DTC strategy is proposed. It uses the fuzzy logic control technique that determines online the accurate values of the weighting factors and generates the optimal switching states that optimize the EV drives' decision. The simulation results built in Matlab/Simulink indicate that the EV can achieve high-performance vehicle longitudinal stability control., 1. Inroduction One of the most fundamental differences between electric vehicles (EVs) and the conventional internal combustion engine vehicles (ICEVs) is that EVs are fully or partially driven by electric [...]

Due to its special structure, the shaft radial force and torque of a switched reluctance motor can be separately controlled when all of the pole currents are independently controlled. In this paper, a control scheme for self-bearing operation of a 12/8 pole SRM drive is proposed. The rotor needs only one bearing for rotation and constraining the axial movement. The other end can move freely in the radial direction but is balanced with the radial force produced by the motor. A model for torque and radial force is derived and used to design the controller. Mutual inductance between the stator poles is included in the analysis to improve the model accuracy. The conduction phase pole currents are energized with phase-shifted sinusoidal currents. Depending on the requested radial force and torque, a descending-inductance phase may also be energized to increase radial force production. The requested force and torque are synthesized from the force and torque produced by these phases. The experimental results demonstrate successful SRM serf-bearing operations. The rotor can be effectively balanced to the center of the air gap. The maximum radial position error was about 0.07 mm when the motor was rotating at 1500 r/min under full load torque. Index Terms--Radial force control, self-bearing control, SRM.

To determine the control structures and possible power quality issues, the dynamic torque generated by the blades of a wind turbine must be represented. This paper presents an analytical formulation of the generated aerodynamic torque of a three-bladed wind turbine including the effects of wind shear and tower shadow. The comprehensive model includes turbine-specific parameters such as radius, height, and tower dimensions, as well as the site-specific parameter, the wind shear exponent. The model proves the existence of a 3p pulsation due to wind shear and explains why it cannot be easily identified in field measurements. The proportionality constant between the torque and the wind speed is determined allowing direct aerodynamic torque calculation from an equivalent wind speed. It is shown that the tower shadow effect is more dominant than the wind shear effect in determining the dynamic torque, although there is a small dc reduction in the torque oscillation due to wind shear. The model is suitable for real-time wind turbine simulation or other time domain simulation of wind turbines in power systems. Index Terms--Real-time digital simulation, simulation model, torque oscillations, tower shadow, wind shear, wind turbine.

In this part of the paper the analytical models for the prediction of the force system, established in Part 1, in conjunction with a complete geometric model of the spade bit, will be used in a systematic simulation analysis of the spade drill's performance. The aim of this analysis is to identify the most desirable geometric characteristics of the different topological features of the spade bit that would result in desirable performance measures expressed in terms of reduced torque and thrust force. The obtained results are intended to guide the development of more efficient tools of this type. [DOI: 10.1115/1.1559157]

The purpose of this work is to present an investigation of the force system generated during spade drill-bit drilling processes that is a prerequisite for the design of spade-drills with improved performance. The technical literature offers no references to this type of bit and process; hence an approach based on the well-established mechanistic force prediction methods will be used. The force and torque prediction models are based on a complete analytical model of a generalized spade bit that takes into account the cutting action of all the characteristic cutting edges of the spade bit, namely of its chisel edge, tip and major cutting edges. In conjunction with the model an efficient model calibration method is also introduced and experimentally verified. [DOI: 10.1115/1.1559156]

The aim of this paper is to develop a new method for minimizing joint torques of redundant manipulators in the Chebyshev sense and to present a fully neural-network-based computational scheme for its implementation. Minimax techniques are used to determine the null space acceleration vector which can guarantee to minimize the maximum joint torque. For real-time implementation, we transform the proposed method into a computation of a recurrent neural network. At each time step, the neural network is adopted for both the solution of the least-norm joint acceleration and the determination of the optimum null space acceleration vector. Compared with previous torque minimization schemes, the proposed method enables more direct monitoring and control of the magnitudes of the individual joint torques than does the minimization of the sum of squares of the components. Simulation results demonstrate that the proposed method is effective for the torque minimization control of redundant manipulators. Index Terms - Neural networks, redundancy resolution, redundant manipulator, torque minimization.

A new method to obtain the torque of a permanent magnet motor by the 3-D finite element method taking into account the rotation of the armature has been developed. The method has an advantage that the 3-D finite element mesh is changed automatically according to the rotation of the armature. The results calculated by our 3-D analysis are compared with the results by the 2-D analysis. The validity of the new method is confirmed by experiments.

The torque of magnetic coupling with different magnetic poles has been investigated by theoretical computations with both FEA and torque formula techniques. The torque of magnetic coupling is sensitive to the number of magnetic poles, and it decreases with increasing the distance between the magnetic rings. From our theoretical computations, we find that we can increase the torque by increasing the number of poles for magnetic coupling between magnetic rings with short distance; however, this is not true for magnetic rings with large separation. We also demonstrate that the theoretical computations of both MagNet software and torque formula established by Furlani are quite consistent and useful for computing the torque of various magnetic couplings. Finally, the theoretical calculation has been successfully tested by using an experimental data taken from a NdFeB magnetic coupling.

A novel position sensorless control algorithm for the newly developed doubly fed reluctance motor (DFPM) drives is presented. The control makes use of the 60-Hz terminal variables, which are easy to acquire and process, for estimation and control of the torque angle of the machine, while the speed of the system is given in an open-loop mode. The control is robust and suitable for variable-speed pump-type application. With this control, the required VA ratings of the PWM converter are only 50% of that of the DFRM motor, and the motor can be started with full load torque. This control scheme has been successfully implemented on a 2-hp DFRM drive.

An easily implemented technique for dynamic torque per ampere enhancement under high levels of motor saturation is described and validated via substantial experimental results presented in this paper. A saturation model assuming only d-axis saturation is utilized in field oriented control of the experimental system and the results are compared to theoretical predictions based on the same saturation model. In order to help users optimize this technique, the paper discusses motor selection issues for the production of this dynamic torque enhancement. An experimental illustration of the use of the torque enhancement principle to break away a load with high static friction is presented to demonstrate the practical application of the concept. Measurement methods used to evaluate the dynamic properties of the electromagnetic torque are presented in sufficient detail that users have appropriate tools for performing such work.

The present design interaction equations for steel beam-columns subjected to end moments and axial loads employ a simplified form of elastic moment amplification factor. This amplification factor is conservative for some values of axial load and unconservative for other values. To accurately represent the amplification factor over a wide range of axial loads, a refined expression for elastic amplification was proposed in the previous literature. This elastic amplification factor provides a good estimation of the amplified moment only for members with very high slenderness ratios that fail by elastic buckling. Members with intermediate slenderness ratios, particularly those with high shape factor, will fail by inelastic buckling, and this inelasticity will have a major influence on the strength of these members. To accurately include the effects of inelasticity in the design interaction equations, this paper develops expressions for an inelastic amplification factor (IAF). The IAF expressions are developed using numerical results obtained by carrying out inelastic analysis of beam-columns with various shape factors, slenderness ratios, and end moments. Design interaction equations with the load and resistance factor design (LRFD) [B.sub.1]-factor and the IAF are compared with numerical inelastic strength of beam-columns., Inelastic amplification factor (IAF) formulations are derived for the design of steel-beam columns. Formulations are based on the inelastic analysis of beam-columns with different slenderness ratios, shape factors and end moment ratios. The elastic amplification factor and load resistance factor design B(sub 1)-factor are also described. Applications of IAF to interaction equations are presented.

In this paper a new algorithm for torque calculation using Maxwell Stress Tensor Method is presented. To reduce the influence of the integration path selection on motor torque calculations an interpolation based on triangular Bezier surfaces has been used. Magnetic field has been calculated by the finite element method using the magnetic vector potential. The calculation results have been tested on a one-phase brushless motor used for all necessary measurements.

Torque-ripple control of the brushless dc motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results. Index Terms--Brushless dc motor, maximum efficiency, optimal current, torque ripple.

Magnet skewing is a straightforward technique to minimize detent torque. An existing fast design package for permanent magnet motors is modified to examine the influence of magnet skew on detent torque, axial force, and back EMF. Magnetic lumped parameter modeling takes care of this 3-D problem by using the sense of average in the axial direction. Performances representing the air gap and magnets are modified as well as the function describing the magnetic motive force distribution in the air gap. Index Terms -- Permanent magnet, motor, magnet skew, lumped parameter model, numerical analysis

A simple construction can help teachers demonstrate torque. A rack measuring 1 meter can be made of one-inch and one-half-inch dowels, an eye screw, and counterweights on a string-pulley system. Asking students to predict how this system will react when weight positions are changed demonstrates the concept of torque, including position and force vectors.