High speed motor control
AssigneeBAE Systems Land & Armaments L.P.
InventorsLane L. Woodland, Stephen M. Stocker, David J. Badzinski, Jeffrey W. Shoemaker, Keith A. Walters
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Abstract
The present invention relates to an apparatus and method for generating digital electrical signals which are representative of the angular position and rotational velocity of a rotatable shaft or similar movable mechanical component in a servomechanism. In particular, the present invention utilizes oversampling techniques to create an accurate, flexible and responsive method for determining shaft position on a high speed motor. The present invention also includes methods for overcoming deadtime losses and velocity lag.
Claims5
A method for calculating a position of a motor by the analog output signals of a resolver with at least two stator windings arranged in a perpendicular alignment to each other on a stator and at least one rotor winding arranged on a rotor which can turn in relation to the stator, the method comprising the following steps:
- applying a sinusoidal excitation signal to the rotor winding;
- deriving a sinusoidal and a cosine resolver signal depending on the angular position of the stator in relation to the rotor form the stator windings;
- converting the sinusoidal and cosine resolver signals into a sine and cosine digital signal, wherein converting utilizes any two analog to digital conversion inputs capable of simultaneously sampling the sine and cosine resolver signals at least 8 times per cycle;
- filtering the sine and cosine digital signals through a FIR bandpass filter for bandwidth limiting;
- decimating the oversampled, filtered sine and cosine digital signal down to the baseband, said decimation by a factor K so as to create a decimated sine and cosine signal;
- rectifying the decimated sine and cosine signals;
- normalizing the decimated sine and cosine signals;
- correcting the quadrature of the decimating sine and cosine signals;
- computing an arctangent output signal to derive an angular value for the relative angular position between the rotor and the stator;
- converting the arctangent output signal to a position signal, said converting including adding a velocity feed-forward factor to remove lag due to the FIR filter and a velocity lag factor to remove residual velocity lag due to system components, the converting including the steps of:
- smoothing the arctangent output signal by inputting into a first integrator,
- adding the velocity feed forward factor,
- differentiating the arctangent output signal by a discrete IIR filter to produce an interpolated velocity signal;
- integrating the interpolated velocity signal by a second integrator to produce an interpolated positions signal;
- adding the velocity lag compensation factor to the interpolated position signal to produce a motor position;
- and
- inputting a theta position for incorporation into a torque command to the motor.
An apparatus for measuring the angular position of a shaft of a motor comprising:
- a resolver having a rotor, the resolver having a first output representative of the sine of the rotor angle and a second output representative of the cosine of the rotor angle;
- a software based resolver-to-digital converter having a first input operably connected to the first output representative of the sine of the rotor angle and a second input operably connected to the second output representative of the cosine of the rotor angle;
- said software-based resolver-to-digital converter including a processor for converting the sine of the resolver rotor angle and the cosine of the resolver rotor angle to produce a shaft velocity and a shaft angle, said processor including a routine for decimating a resolver signal by a factor K, correcting for velocity lag and incorporating a velocity feed-forward term.
Dependencies are inferred from the claim text.