back-EMF Constant Research Articles

Modeling and derivation of back EMF and torque constants of gearless flat-type brushless DC motor

This paper develops the mathematical modeling for the gearless flat-type brushless DC motor. The major two machine constant coefficients will be investigated to derive the compact form related to t...

Characteristics Regulation for Manufacture of Permanent-Magnet Motors Using Post-Assembly Magnetization

This paper proposes a technique for manufacturing permanent-magnet (PM) motors by means of post-assembly magnetization (PAM) rather than assembling with the rotor premagnetized. This can be used to vary the operating characteristics of the motor. PAM utilizes the stator windings of the PM motor to magnetize the magnets after complete assembly, where large current pulses are applied to magnetize the machine. However, in this paper, it is shown that PAM can be used in a manner where a degree of unsaturated magnetization is allowed, so that the motor back EMF constant can be regulated without modifying windings or geometry. Various magnetizing current pulses are applied which result in a range of back EMFs. These are measured for verification. From the experimental results, the feasibility of this magnetizing technique is demonstrated for a rare-earth magnet motor. It is also suggested that the magnetizing efficiency can be improved and the copper ratings reduced since it is found that large magnetizing currents may not contribute to magnetization beyond a certain current level

Electromagnetic analysis and control parameter estimation of moving-coil linear oscillatory actuator

This paper deals with an electromagnetic analysis and control parameter estimation of a moving-coil linear oscillatory actuator (MCLOA). Analytical solutions for electromagnetic characteristics of the MCLOA are obtained from transfer relations derived in terms of a magnetic vector potential and two-dimensional (2D) rectangular coordinate systems. And then, on the basis of 2D analytical solutions, control parameters such as the thrust constant, the back-emf constant, and winding inductances are estimated. Finally, analytical results for both electromagnetic characteristics and control parameters of the MCLOA are validated extensively by finite element analyses. In particular, test results such as static thrust, resistance, and inductance measurements are given to confirm the analyses.

Practical parameter estimation through space harmonic method and experiment of permanent magnet linear synchronous motor for high accuracy field orient control

This paper presents the practical parameter estimation for a slotless air-cored permanent magnet linear synchronous motor (PMLSM) using an analytical method and experiment. In the analytical method, the linkage flux is calculated through the generalized magnetic vector potential obtained by the space harmonics and transfer relation with each region of permanent magnet (PM) mover, air gap, and winding stator. This linkage flux is used to estimate the dynamic parameters such as magnetization inductance, backemf, and thrust constant. Also, the resistance and self-inductance with one phase are obtained by the experiment. Therefore, dynamic simulation of a linear synchronous motor composed of dynamic parameters is performed by the nonrotating (d-q) voltage equation. In good agreement with the estimated parameter values, the experimental results confirm the validity of the analysis method and simulation.

Sensorless control of a PM synchronous motor for direct drive washer without rotor position sensors

Sensorless control of a PM synchronous motor for direct drive washers with parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and the model of the position estimator. The stator resistance is measured near zero speed when the motor changes its rotating direction. The variation of the stator resistance and back EMF constant due to the temperature variation is compensated for in the model of the position estimator. The gains in the position estimator are also adapted according to motor speed. The increase in the DC link voltage caused by the regenerated power at braking is reduced by adding the extra γ-axis current in the DC link capacitor voltage controller.

Analysis and design of synchronous permanent-magnet planar motors

The force equation of a synchronous permanent-magnet planar motor (SPMPM) was investigated. The flux density distribution of a two-dimensional (2-D) magnet array for a SPMPM was obtained by solving the equations of the scalar magnetic potential. The expressions of the force and back-EMF constant were derived and examined. Using these expressions, the conditions for normal operation of the SPMPM were found and the optimal design was determined in order to maximize the force of the SPMPM.

PARAMETER IDENTIFICATION OF A SEPARATELY EXCITED OC MOTOR FOR SPEED CONTROL

ABSTRACT This paper presents the application of the least error squares (LES) parameter identification algorithm to. obtain parameters of a separately excited DC motor. The parameters of interest are; the resistance and inductance of the armature windings (Ra.Lt). the motor inertia (J), the damping constant (D), the torque and back emf constant (K) and the load torque constant (μ.). The data used are the motor input voltage, and the corresponding rotor speed. It is assumed that the trajectory of the motor speed as well as the corresponding input voltage are known and sampled at a preselected rate. Simulation results for a separately excited dc motor used in robotics are reported showing good agreement with actual parameter values.

Analysis, design and control of a novel spherical permanent-magnet actuator

The authors describe the analysis, design and control of a novel actuator with a spherical permanent-magnet rotor and a simple stator winding and position-sensing arrangement. It is capable of two degrees of freedom, and has a high specific torque. Expressions for the magnetic field distribution and the torque vector and back-EMF constants are derived analytically, and optimal design parameters, which result in maximum output torque or maximum acceleration for a given payload, are derived. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of a robust control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.

An improved design procedure for hybrid stepper motors

A design methodology for hybrid stepper motors is presented. It takes into account the saturation throughout the motor, allows for variations in magnet working point, and enables the designer to optimize the balance of coil and magnet MMFS (magnetomotive forces) to achieve a specified holding torque. The procedure is based on the use of the finite-element technique to generate permeance curves for the complex tooth/airgap region of the motor, accounting for localized saturation effects in the teeth. The curves are then used in a nonlinear lumped parameter network of the entire motor. The network models the motor's 3-D nature and may include other saturating elements as well as leakage permeances. By applying the virtual-work technique, the lumped parameter network is used to calculate torque/displacement characteristics as well as the winding inductance and back-EMF (electromotive force) constants. The technique has been used in the design and analysis of several industrial stepper motors utilizing high-energy rare-earth magnets. >