High resolution position sensor

A position sensor device for controlling the position of a motor, said device comprising:

• encoder means for providing a pulse with each transition of the motor shaft position over a rotation position interval;
• means for generating a train of system clock pulses at a first rate and a train of divided system clock pulses at a fraction of said first rate;
• first means for counting a first number of pulses of said divided system clock pulse train occurring between each occurrence of said transition pulse;
• means for storing said first counted number of pulses of said divided system clock pulse train;
• second means for counting a second number of pulses of said divided system clock pulse train, and resetting said second counted number upon each transition pulse;
• second means for storing said second counted number of pulses of said divided system clock pulse train, in a register at a shifted storage position representing a multiple of said second counted number of pulses;
• means for repeatedly comparing, at a relatively high rate, said shifted, stored second counted number and said stored first counted number and producing a difference count therebetween if the former exceeds the latter;
• means for generating a high resolution pulse upon replacing said shifted stored second counted number with said difference count in said register, thus providing several high resolution pulses between transition pulses;
• and
• means for calculating the motor shaft position by counting the number of high resolution pulses in the interval between occurrences of said transition pulses.

A method for measuring a changing variable of a system and providing output values representing the system variable with increased resolution, said method comprising the steps of:

• providing a pulse with each transition of the measured variable over a level of each of a set of regularly spaced apart predetermined levels,
• generating a train of system clock pulses;
• counting a first number of system clock pulses between the last two occurrences of said transition pulse;
• counting a second number of said system clock pulses at a multiple rate starting at each transition pulse;
• repeatedly comparing said second and first number of pulses, and generating a high resolution pulse if said second counted number exceeds said first counted number;
• and
• calculating the system variable by counting the number of high resolution pulses in the interval between occurrences of said transition pulses.

A method for measuring a motor shaft position, said method comprising the steps of:

• providing a pulse with each transition of the motor shaft position over a rotation position interval;
• generating a train of system clock pulses;
• counting a first number of system clock pulses between the last two occurrences of said transition pulse;
• counting a second number of said system clock pulses at a multiple rate starting at each transition pulse;
• repeatedly comparing, at a relatively high rate, said second and first number of pulses, and generating a high resolution pulse if said, second counted number exceeds said first counted number;
• and
• calculating the motor shaft position by counting the number of high resolution pulses in the interval between occurrences of said transition pulses.