Method and apparatus for detecting positions and/or speed of a moving body using two phase signals

• US 5,019,773 A
• Filed: 08/22/1989
• Issued: 05/28/1991
• Est. Priority Date: 08/24/1988
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nagase, Hiroshi, Miyashita, Kunio, Mutoh, Nobuyoshi, Sugai, Hiroshi, Sugiura, Yasuyuki, Kobayashi, Sumio, Oue, Rika
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US07/397,130
• Time in Patent Office: 644 Days
• Field of Search: 324/160, 324/161, 324/163-166, 324/208, 324/207.25, 364/565, 361/236, 361/239, 361/240, 318/721, 318/799
• US Class Current: 324/166
• CPC Class Codes: G01D 5/24409 Interpolation using memories
• CPC Class Codes: G01D 5/246 by varying the duration of individual pulses
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

Sine wave signals generated from a position detector are used as analog values to detect a fine position of a rotating or moving body, a rise or fall edge of the sine wave signal is used to detect a coarse position of the rotating or moving body, and the position or speed of the rotating or moving body is detected based on a signal indicative of the detected coarse position when the rotating or moving body is at high speed and based on a signal indicative of the detected fine position when the rotating or moving body is at low speed to thereby provide optimal control from high speed to low speed. Especially at extremely low driving, speed detection with superhigh resolution is effected using the analog value to decrease an uneven rotation of the rotating body.

Claims

1. A position detecting apparatus comprising:

a position detector for generating two analog detection signals, said two analog detection signals being out of phase depending on movement of a rotating or moving body;

a pair of PWM pulse forming circuits each responsive to an associated one of said analog detection signals for producing a PWM pulse signal having a pulse width representative of positions of said body;

a pair of D/A converters for converting said PWM pulse signals to reproduced analog signals;

a pair of original pulse circuits for converting said analog detection signals from said position detector to rectangular wave pulse signals;

a pair of first switches each connected to receive the PWM pulse signal from an associated one of said PWM pulse forming circuits and the rectangular wave signal from an associated one of said original pulse circuits for selecting one of the PWM pulse signal and the rectangular wave signal to supply the selected signal to an associated one of said D/A converters, the signal selection being such that at least one of the PWM signal and the rectangular wave signal is selected when the moving speed is relatively low and relatively high, respectively;

a pair of pulse shaping circuits for shaping said reproduced analog signals from said D/A converters to form pulse signals;

a coarse position detector connected to said pulse shaping circuits for detecting a coarse of said body from edges of the pulse signals from said pulse shaping circuits;

a fine position detector connected to said pair of D/A converters for detecting a fine position of said body from said reproduced analog signals from said D/A converters; and

a third switch for selecting one of the outputs from the coarse and fine position detectors depending on the speed of said body.

2. A speed detecting apparatus according to claim 1, wherein said two analog detection signals are 90°

out of phase with each other and have a triangular or sinusoidal waveform.

3. A position detecting apparatus comprising:

a position detector for generating at least one of sine wave and triangular analog detection signals 90°

out of phase depending on the speed of a rotating or moving body;

a pair of PWM pulse forming circuits each responsive to an associated one of said analog detection signals for producing a PWM pulse signal having a pulse width representative of positions of said body;

a pair of original pulse circuits for generating rectangular wave signals based on said analog detection signals;

a frequency detector for detecting a frequency of said analog detection signals from said position detector;

a pair of first switches each connected to receive the PWM pulse signal from an associated one of said PWM pulse forming circuits and the rectangular wave signal from an associated one of said original pulse circuits for selecting one of the received PWM pulse signal and the received rectangular wave signal in response to an output of said frequency detector, the signal selection being such that the PWM pulse signal or the rectangular wave signal is selected when the moving speed of said body is relatively low or relatively high, respectively;

a pair of D/A converters for converting said selected signals from said first switches to reproduced analog signals;

a pair of pulse shaping circuits for shaping said reproduced analog signals from said D/A converters to form pulse signals;

a pair of second switches each connected to receive the reproduced analog signal from an associated one of said D/A converters and the selected signal from an associated one of said first switches for selecting one of the received reproduced analog signal and the received selected signal;

a coarse position detector connected to receive selected outputs from said second switches and for counting pulses contained in said received outputs from said second switches;

a fine position detector connected to receive said reproduced analog signal and for producing therefrom fine position information and outputting a signal indicative of said fine position information;

a position and speed detector of a sine wave system for detecting the position and speed of said body from said output indicative of said fine position information from said fine position detector;

a position and speed detector of a pulse system for detecting the position and speed of said body from the number of pulses contained in said pulse signals or in said rectangular wave signals and an interval of the pulses;

a third switch connected to receive outputs of said position and speed detector of a sine wave system and said position and speed detector of a pulse system; and

a speed controller for providing speed control in accordance with the position and speed of said body, a switching operation of said pair of second switches being controlled by an output of said speed controller, and a switching operation of said third switch being controlled by another output of said speed controller.

4. A speed detecting apparatus according to claim 3, wherein the output of said frequency detector has hysteresis to switch said pair of first switches;

and wherein said third switch is controlled to perform a switching operation in a low speed region compared to said pair of first switches, and wherein said pair of second switches is controlled to perform a switching operation in a high speed region compared to said pair of first switches.

5. A speed detecting apparatus according to claim 3, wherein said fine position detector includes a sample-hold circuit for sampling and holding said reproduced analog signals and an A/D converter for converting outputs of said sample-hold circuit to analog signals, and wherein said position and speed detector of a sine wave system includes means for calculating a ratio between said analog signals from said A/D converter and a means for determining a fine position of said body by referencing a position ratio table with said calculated ratio being used as a key to the referencing of said table.

6. A speed detecting apparatus according to claim 3, wherein a signal for selecting one of the original pulse region and the pulse shaping region is switched by edges of said shaped pulse signals.

7. A speed detecting apparatus comprising:

a position detector for generating analog detection signals out of phase depending on movement of a rotating or moving body;

a pair of PWM pulse forming circuits each responsive to an associated one of said analog detection signals for producing a PWM pulse signal having a pulse width representative of positions of said body;

a frequency-to-voltage converter for converting a frequency of at least one of said analog detection signals to a corresponding voltage signal;

a carrier generator for generating a carrier signal;

a first switch connected to receive said carrier signal and a reference potential;

a hysteresis comparator for comparing said voltage signal from said frequency-to-voltage converter with a predetermined voltage to generate a frequency-related hysteresis switch control signal, said control signal being fed to said first switch so that said carrier signal or said reference potential is selected when said voltage signal from said frequency-to-voltage converter is determined to be smaller or larger than said predetermined voltage, respectively, and is supplied to said pair of PWM pulse forming circuits for pulse width modulation with said analog detection signals for producing said PWM pulse signals;

a pair of D/A converters for converting said PWM pulse signals to reproduced analog signals;

a pair of pulse shaping circuits for shaping said reproduced analog signals to form rectangular wave signals;

a coarse position detector connected to said pulse shaping circuits for detecting a coarse position of said body from edges of said rectangular wave signal from said pulse shaping circuits; and

a fine position detector connected to said D/A converters for detecting a fine position of said body from said reproduced analog signals from said D/A converters.

a fine position detector connected to said D/A converters for detecting a fine position of said body from said reproduced analog signals from said D/A converters.