ENCODER HAVING FUNCTION OF ADJUSTING THRESHOLD VALUE OF COMPARATOR AND METHOD FOR CONTROLLING ENCODER

• US 20180356260A1
• Filed: 06/08/2018
• Published: 12/13/2018
• Est. Priority Date: 06/13/2017
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Kondou, Youhei, Imai, Keisuke
• Granted Patent: US 10,444,041 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence
• CPC Class Codes: G01D 5/34 the beams of light being detected by photocells
• CPC Class Codes: G01D 5/347 using displacement encoding scales
• CPC Class Codes: H03K 5/24 the characteristic being amplitude

Abstract

An encoder according to an embodiment of this disclosure includes a voltage generation circuit connected to a power supply through a diode and having a variable resistor, the voltage generation circuit outputting a voltage corresponding to a current flowing through the diode and a resistance value of the variable resistor, as a threshold value; a comparator for comparing an analog signal inputted from a detector for detecting rotation of a motor with the threshold value inputted from the voltage generation circuit, and outputting a comparison result as a comparator output; an A/D converter for converting the analog signal into a digital signal; a threshold value determination circuit for calculating a new threshold value using the digital signal; and a resistance value change circuit for changing a resistance value of the variable resistor, such that the calculated new threshold value is inputted from the voltage generation circuit to the comparator.

Claims

1. An encoder comprising:

a voltage generation circuit connected to a power supply through a diode and having a variable resistor, the voltage generation circuit configured to output a voltage corresponding to a current flowing through the diode and a resistance value of the variable resistor, as a threshold value;

a comparator configured to perform a comparison between an analog signal inputted from a detector for detecting rotation of a motor and the threshold value inputted from the voltage generation circuit, and output a comparison result as a comparator output;

an A/D converter configured to convert the analog signal into a digital signal;

a threshold value determination circuit configured to calculate a new threshold value using the digital signal; and

a resistance value change circuit configured to change a resistance value of the variable resistor, such that the calculated new threshold value is inputted from the voltage generation circuit to the comparator.

2. The encoder according to claim 1, wherein the new threshold value is an average value of a maximum value and a minimum value of the digital signal.

3. The encoder according to claim 1, further comprising an amplification circuit configured to amplify an amplitude of the analog signal and outputting the amplified analog signal to the A/D converter.

4. An encoder comprising:

a voltage generation circuit connected to a power supply through a diode and having a variable resistor, the voltage generation circuit configured to output a voltage corresponding to a current flowing through the diode and a resistance value of the variable resistor, as a threshold value;

a plurality of comparators configured to perform comparisons between each of analog signals inputted from detectors for detecting rotation of motors and the threshold value inputted from the voltage generation circuit, and output comparison results as comparator outputs;

a plurality of A/D converters configured to convert the analog signals into digital signals;

a threshold value determination circuit for calculating a new threshold value using the digital signals; and

a resistance value change circuit configured to change a resistance value of the variable resistor, such that the calculated new threshold value is inputted from the voltage generation circuit to the comparators.

5. The encoder according to claim 4, wherein the new threshold value is a minimum value of average values each of which is calculated from a maximum value and a minimum value of each of the digital signals.

6. The encoder according to claim 4, further comprising a plurality of amplification circuits configured to amplify amplitudes of the analog signals and output the amplified analog signals to the A/D converters.

7. A method for controlling an encoder comprising the steps of:

inputting an output voltage of a voltage generation circuit having a variable resistor to a comparator, as a threshold value;

inputting an analog signal from a detector of the encoder to the comparator and an A/D converter;

converting the analog signal into a digital signal by the A/D converter;

performing a comparison between the analog signal and the threshold value, and outputting a comparison result as a comparator output by the comparator;

calculating a new threshold value using the digital signal by a threshold value determination circuit, and changing a resistance value of the variable resistor of the voltage generation circuit by a resistance value change circuit, such that the calculated new threshold value is inputted from the voltage generation circuit to the comparator.

8. The method according to claim 7, wherein when the threshold value determination circuit calculates the threshold value using the digital signal, the threshold value determination circuit calculates an average value of a maximum value and a minimum value of the digital signal, and determines the calculated average value as the new threshold value.

9. The method according to claim 7, wherein the step of inputting the analog signal from the detector of the encoder to the A/D converter further includes the step of amplifying an amplitude of the analog signal by an amplification circuit.

10. A method for controlling an encoder comprising the steps of:

inputting an output voltage of a voltage generation circuit having a variable resistor to a plurality of comparators, as a threshold value;

inputting analog signals from a plurality of detectors of the encoder to a plurality of comparators and a plurality of A/D converters;

converting the analog signals into digital signals by the A/D converters;

performing comparisons between each of the analog signals and the threshold value, and outputting comparison results as comparator outputs by the comparators;

calculating a new threshold value using the digital signals by a threshold value determination circuit, and changing a resistance value of the variable resistor of the voltage generation circuit by a resistance value change circuit, such that the calculated new threshold value is inputted from the voltage generation circuit to the comparators.

11. The method according to claim 10, wherein when the threshold value determination circuit calculates the threshold value using the digital signals, the threshold value determination circuit calculates an average value of a maximum value and a minimum value of each of the digital signals, and determines a minimum value of the calculated average values, as the new threshold value.

12. The method according to claim 10, wherein the step of inputting the analog signals from the detectors of the encoder to the A/D converters further includes the step of amplifying amplitudes of the analog signals by a plurality of amplification circuits.