Free gyro motor drive circuit

Claim 1

A free gyro motor drive circuit comprising: a gyro motor having a cylindrical housing; a shaft rotatable in said cylindrical housing; a permanent magnet mounted on said shaft; a first up-down motor coil, having an input terminal, connected in series to a second up-down motor coil, having an input terminal, each of said up-down motor coils being mounted on an internal wall of said cylindrical housing and being positioned 180° apart; and a first right-left motor coil, having an input terminal, connected in series to a second right-left motor coil, having an input terminal, each of said right-left motor coils being mounted on said internal wall of said cylindrical housing, being positioned 180° apart, and 90° from said first up-down motor coil; first sensing means mounted on said internal wall of said cylindrical housing, mounted in line with said first up-down motor coil, and having an output, for generating an up-down sinusoidal position signal having a frequency corresponding to the rotational speed of said gyro motor; second sensing means; mounted on said internal wall of said cylindrical housing, mounted in line with said first right-left motor coil, located 90° from said first sensing means, and having an output; for generating a right-left sinusoidal position signal having a frequency corresponding to the rotational speed of said gyro motor; comparing means, having an input connected to said output of said first sensing means and an output, for converting said up-down sinusoidal position signal to a constant amplitude position signal having a frequency identical to the frequency of said up-down sinusoidal position signal; first filtering means having an input effectively connected to said output of said comparing means and an output for passing said constant amplitude position signals below a predetermined cut off frequency to obtain a fixed amplitude position signal; absolute value circuit means, having an input operatively connected to said output of said first filtering means and an output, for converting said fixed amplitude sinusoidal position signal to a full wave rectified position signal; second filtering means, having an input connected to said output of said absolute value circuit means and output, for changing said full wave rectified position signal to a direct current error signal; polarity and temperature control circuit means, having an output, for determining a frequency at which said direct current error signal will change polarity and to compensate for temperature variations affecting the performance of the free gyro motor drive circuit; a summer having an input effectively connected to said output of said second filtering means and said output of said polarity and temperature control circuit means; first speed control circuit means, having a first input connected to said output of said first sensing means, and a second input connected to said output of said summer, for producing an up-down motor control signal having an output voltage proportional to the product of said up-down sinusoidal position signal and said direct current error signal; second speed control circuit means, having a first input connected to said output of said second sensing means, and a second input connected to said output of said summer for producing a right-left motor control signal having an output voltage proportional to the product of said right-left sinusoidal position signal and said direct current reference signal; first motor drive circuit means, having an input connected to said output of said first speed control circuit means, a first output effectively connected to said input terminal of said first up-down motor coil, and a second output effectively connected to said input terminal of said second up-down motor coil, for amplifying said up-down motor control signal; and second motor drive circuit means, having an input connected to said output of said second speed control circuit means, a first output effectively connected to said input terminal of said first right-left motor coil and a second output effectively connected to said input terminal of said second right-left motor, for amplifying said right-left motor control signal.