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

• US 20180356257A1
• Filed: 06/07/2018
• 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 10,451,444 B2
• Time in Patent Office: Days
• CPC Class Codes: G01D 5/14 influencing the magnitude of a current or voltage
• CPC Class Codes: G01D 5/244 influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
• CPC Class Codes: G01D 5/24428 Error prevention
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence
• CPC Class Codes: G01D 5/245 using a variable number of pulses in a train
• CPC Class Codes: G01D 5/347 using displacement encoding scales
• CPC Class Codes: G01D 5/34707 Scales; Discs, e.g. fixation, fabrication, compensation
• CPC Class Codes: G01D 5/36 Forming the light into pulses
• CPC Class Codes: G01R 19/165 Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
• CPC Class Codes: H03K 5/086 generated by feedback
• 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 performing 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 outputting a comparison result as a comparator output; a resistance value variation circuit for varying the resistance value of the variable resistor; and a threshold value determination circuit for determining the threshold value based on a relationship between the resistance value and the comparator output.

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 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 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;

a resistance value variation circuit configured to vary the resistance value of the variable resistor; and

a threshold value determination circuit configured to determine the threshold value based on a relationship between the resistance value and the comparator output.

2. The encoder according to claim 1, wherein the threshold value is an average value of a maximum value and a minimum value of threshold values with which, when the resistance value is varied continuously, the comparator output becomes normal.

3. The encoder according to claim 1, wherein the threshold value is an average value of a maximum value, an intermediate value, and a minimum value of threshold values with which, when the resistance value is varied at regular intervals, the comparator output becomes normal.

7. The encoder according to claim 1, wherein the threshold value determination circuit determines the threshold value by operating the resistance value variation circuit at a predetermined constant timing.

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 outputting a voltage corresponding to a current flowing through the diode and a resistance value of the variable resistor, as a threshold value;

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

a resistance value variation circuit configured to vary the resistance value of the variable resistor; and

a threshold value determination circuit configured to determine the threshold value based on a relationship between the resistance value and the multiple comparator outputs.

5. The encoder according to claim 4, wherein the threshold value is a minimum value of multiple threshold values, corresponding to the multiple analog signals, each of which is calculated from a maximum value and a minimum value of threshold values with which, when the resistance value is varied continuously, the comparator output becomes normal.

6. The encoder according to claim 4, wherein the threshold value is a minimum value of multiple threshold values, corresponding to the multiple analog signals, each of which is calculated from a maximum value, an intermediate value, and a minimum value of threshold values with which, when the resistance value is varied at regular intervals, the comparator output becomes normal.

8. A method for controlling an encoder comprising:

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;

varying a resistance value of the variable resistor by a resistance value variation circuit;

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

determining the threshold value based on a relationship between the resistance value and the comparator output by the threshold value determination circuit; and

varying the resistance value of the variable resistor of the voltage generation circuit by the resistance value variation circuit, such that the determined threshold value is inputted from the voltage generation circuit to the comparator.

9. The method according to claim 8, wherein the threshold value is an average value of a maximum value and a minimum value of threshold values with which, when the resistance value is varied continuously, the comparator output becomes normal.

10. The method according to claim 8, wherein the threshold value is an average value of a maximum value, an intermediate value, and a minimum value of threshold values with which, when the resistance value is varied at regular intervals, the comparator output becomes normal.

14. The method according to claim 8, wherein the threshold value determination circuit determines the threshold value by operating the resistance value variation circuit at a predetermined constant timing.

11. A method for controlling an encoder comprising:

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

inputting multiple analog signals from multiple detectors of the encoder to the multiple comparators;

varying a resistance value of the variable resistor by a resistance value variation circuit;

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

determining the threshold value based on relationship between the resistance value and the multiple comparator outputs by the threshold value determination circuit; and

varying the resistance value of the variable resistor of the voltage generation circuit by the resistance value variation circuit, such that the determined threshold value is inputted from the voltage generation circuit to the multiple comparators.

12. The method according to claim 11, wherein the threshold value is a minimum value of multiple threshold values, corresponding to the multiple analog signals, each of which is calculated from a maximum value and a minimum value of threshold values with which, when the resistance value is varied continuously, the comparator output becomes normal.

13. The encoder according to claim 11, wherein the threshold value is a minimum value of multiple threshold values, corresponding to the multiple analog signals, each of which is calculated from a maximum value, an intermediate value, and a minimum value of threshold values with which, when the resistance value is varied at regular intervals, the comparator output becomes normal.