JPH0145847B2 - - Google Patents

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention is a method of detecting the position of an object using a periodic constant signal generated by a detector in response to the motion of the object moving or rotating in two directions. In particular, the present invention relates to a position detection method for obtaining a position signal of a motor or an object driven by the motor using a signal with less ripple.

(b) Prior Art and Problems As a method for detecting the position of a motor or an object driven by a motor, methods using rotary encoders, linear encoders, etc. are known.
For example, a rotary encoder is attached to the rotating shaft of a motor, and generates two-phase pseudo sine wave signals A and B having a phase difference of 1/4 according to the rotation of the rotating shaft. The frequency of the wave signal is proportional to the rotational speed of the motor. An object position signal is usually detected from the pseudo sine wave signals of the two-phase signals A and B as described below.

FIG. 1 is a circuit diagram for generating a position signal from the pseudo sine wave signal. FIG. 2 is a waveform diagram of each part in FIG. 1. As the motor 1 rotates, the rotary encoder 2 generates two phases, a signal A and a signal B having a phase difference of 1/4, and the signal A enters the comparator 3 and the signal B enters the comparator 4. The comparator 3 generates a signal of "1" if the signal A is greater than 0 volts, and '0' if it is smaller, the monostable 5 generates a pulse at the rising edge of the output of the comparator 3, and the monostable 6 Comparator 3
A pulse is generated at the falling edge of the output. The comparator 4 generates a signal of “1” if the signal B is greater than 0 volts, and “0” if it is smaller, the monostable 7 generates a pulse at the rising edge of the output of the comparator 4, and the monostable 8 generates a pulse. A pulse is generated at the falling edge of the output of comparator 4. The outputs of the monostables 5 and 6 are logically summed in an OR circuit 10, the outputs of monostables 7 and 8 are logically summed in an OR circuit 11, and further logically summed in an OR circuit 12.
is logically summed and entered into the counter 14, and the counter 14 counts at the falling edge of the pulse. Addition or subtraction is performed by detecting the rotational direction of the motor 1 using the outputs of the exclusive OR circuits 9 and 13. When the reset pulse generator 16 is operated, the counter 1
4 is reset. After that, if the motor 1 starts rotating clockwise, the outputs of the comparators 3 and 4 change every time the signals A and B cross 0 volts, and the monostables 5, 6, 7, and 8 generate pulses. The pulse is added to the counter 14 as described above, and since the output of the exclusive OR circuit 13 becomes "1", the counter 14 continues to be incremented. The output of the counter 14 is output by a digital-to-analog converter 15 as a stepped voltage waveform. Also, when the rotation direction of the motor 1 is reversed and rotates to the left, the exclusive OR circuit 13
The output becomes "0" and the counter 14 is decremented. As explained above, the output of the digital/analog converter 15 is a position signal indicating the amount of rotation of the motor 1 after the reset pulse generator 16 is operated.

According to such conventional technology, only a stepped voltage waveform having a unit of 1/4 period of the signals A and B can be obtained as a position signal. Therefore, in order to accurately measure the motor circuit position, it is conceivable to increase the number of pseudo sine waves generated per one revolution of the motor, that is, to reduce the number of slits in the rotary encoder. However, this has drawbacks such as increasing the cost of the rotary encoder and mechanically limiting the ability to increase the number of slits.

(c) Purpose of the Invention The purpose of the present invention is to subdivide one period of a pseudo sine wave from a rotary encoder at equal intervals and store the corresponding amplitude values in a storage circuit, without using mechanical means, in order to eliminate the above-mentioned drawbacks. By storing it and using it to follow the changing pseudo sine wave, the digital circuit counts the subdivided equal intervals as the minimum unit, and the output of the comparison circuit of the tracking circuit is counted over two clock cycles. The object of the present invention is to provide a position detection method that reduces ripples in a position signal by increasing or decreasing the count value of the digital circuit only when the digital circuit continuously takes the same logical value.

(d) Structure of the invention A two-phase signal A or B generated by a detector according to the motion of an object moving or rotating in two directions and having a phase difference of 1/4 period from each other means for storing an amplitude value; amplitude comparison means for digital-to-analog converting the output of the storage means and comparing it with the amplitude of the signal A or B; Follow-up circuits A and B each include counting means for subtracting and accessing the storage means, and the output of the counting means and the output of the amplitude comparison means are input, and the one closer to the amplitude center level of the signal A or B A selection circuit that selects each signal A and B compares each amplitude and zero potential of each signal A and B.
Comparing means A and B outputting whether each amplitude is positive or negative, the output of the amplitude comparing means of the vibration tracking circuits A and B, the selection signal from the selection circuit, and the comparison means for determining the direction of motion of the object from the outputs of means A and B; a logic circuit for determining whether the output of the amplitude comparison means is a logic 1 or a logic 0 continuously over two periods of the clock pulse; Addition or subtraction is instructed by the means for determining the motion of the object, and the output of the logic circuit allows counting;
The apparatus comprises a counting means for counting the clocks and outputting the counting result as a signal indicating the position of the object.

(e) Embodiment of the Invention FIG. 3 is a circuit diagram showing an embodiment of the invention, and FIG. 4 is an explanatory diagram of the operation of FIG. 3. The motor 1 rotates, and the rotary encoder 2 generates two phases, a signal A and a signal B having a phase difference of 1/4. Clock oscillator 17 generates clock pulses of sufficiently high frequency for changes in signals A and B. In the memories 19 and 25, for example, a ROM is used to store amplitude values M0 to M15 corresponding to positions 100 to 115, which are obtained by dividing one period of the signal A or B into 16 equal parts, as binary digital values, as shown in FIG. When the output of the memory 19 is digital-to-analog converted by the D/A converter 20, one of the amplitude values M0 to M15 of the signal A corresponding to the count value of the counter 18 is obtained as DACA. The comparator 21 compares the amplitude value of the signal A sent from the rotary encoder 2 with the amplitude value DACA read out from the memory 19. The output of comparator 21 is “1” if signal A is greater than DACA.
Then, the count value of the counter 18 is added. That is, the addition is performed using the clock from the clock oscillator 17. If signal A is less than DACA, the output of comparator 21 will be "0" and counter 18 will be decremented by the next clock pulse. Since the amplitude values of M0 to M15 in the memory 19 are read based on the count value of the counter 18, DACA follows the waveform of the signal A while taking one of the values of M0 to M15. That is, counter 18, memory 19, D/A converter 20, comparator 2
1 constitutes a follow-up circuit A47. Similar counter 2
4, memory 25, D/A converter 26, comparator 27
constitutes a follow-up circuit B48. The operation of the follow-up circuit B48 is the same as that of the follow-up circuit A47 except that the signal waveform to be compared is the signal B. That is, the output DACB of the D/A converter 26 follows the waveform of the signal B.
Therefore, the relationship between signal A and DACA and between signal B and DACB becomes as shown in FIG. 4, and the outputs of comparators 21 and 27 also change as shown in FIG. The output of the comparator 22 is "1" if the waveform of the signal A is greater than 0 volts, and "0" if it is smaller. Similarly, comparator 28
The output of the signal B becomes "1" if the waveform of the signal B is larger than 0 volts, and "0" if it is smaller.

FIG. 6 is a detailed circuit diagram of the A, B selection circuit 23. Select when the output of the counter 18 is M4 (Fig. 5) and the output of the comparator 21 is "1", or when the output of the counter 18 is M11 and the output of the comparator 21 is "0". Signal USEA is set. The output of the counter 18 is M3 and the output of the comparator 21 is "0", or the output of the counter 18 is
When the output of comparator 21 is “1” in M12, the selection signal
USEA will be reset. That is, when the output of the counter 18 is M4, the decoder 50 sets the terminal 104 to "1".
shall be. AND because the output of comparator 21 is “1”
The circuit 52 becomes “1” and goes through the OR circuit 56 to JK.
Set flip-flop 58. counter 1
When the output of 8 is M11, the terminal 111 of the decoder 50
becomes "1", and the output of the comparator 21 is "0", so the NOT circuit 53 becomes "1", and the AND circuit 53
becomes “1” and the flip-flop 5 becomes “1” as before.
Set 8. When the output of counter 18 is M3,
Since the terminal 103 of the decoder 50 becomes "1" and the output of the comparator 21 is "0", the NOT circuit 51
The output of is "1" and the AND circuit 54 is "1",
The flip-flop 58 is reset via the OR circuit 57. When the output of the counter 18 is M12, the terminal 112 of the decoder 50 becomes "1", and the comparator 2
Since the output of 1 is “1”, the AND circuit 55 is “1”
Then, the flip-flop 58 is reset as described above. This is used to use the range shown by the arrow in Figure 5 to adopt information in a range close to the center level where the voltage level difference between adjacent positions of signal A or signal B is relatively large and the amplitude difference can be detected with high accuracy. It is something.

The output of the comparator 21, that is, the output of the follow-up circuit 47, enters the D flip-flop 29 and is output at 2 clock cycles.
When the output of the comparator 21 is "1" continuously over a period, the AND circuit 35 becomes "1", and conversely, when the output of the comparator 21 is "0" continuously, the output of the comparator 21 becomes "1". The output of the D flip-flop 29 becomes “0” and is ANDed by the NOT circuits 31 and 32.
The circuit 36 is set to "1". Therefore, the output of the OR circuit 39 is "1" if the output of the comparator 21 is "1" or "0" for two periods of the clock cycle.
If the output of the comparator 21 repeats "1" and "0" every clock cycle, it becomes "0" and enters the multiplexer 43. The output of the comparator 27, that is, the output of the tracking circuit 48, is sent to the D flip-flop 30.
enters AND circuits 37, 38, NOT circuit 33,
34 and OR circuit 40, if the output is "1" or "0" continuously for two periods of the clock cycle, similarly to the output of the comparator 21, a logic "1" is input to the multiplexer 43, and the clock cycle is changed. Input the case where "1" and "0" are repeated for each time. A,
The output USEA of the B selection circuit 23 is sent to the multiplexer 4.
3 to send out either of the outputs of OR circuits 39 and 40. As mentioned above, for this output, information in a range close to the center level of signal A or B is selected,
It is sent to the counter 45 as a count enable signal. The counter 45 adds or subtracts clock pulses only when the count enable signal is "1". That is, when the change in the signal A or B selected by the selection signal USEA is small and the counter 18 or 24 of the tracking circuit 47 or 48 repeats addition and subtraction, the count value of the counter 45 does not change.

The output of the AND circuit 35 and the output of the comparator 28 enter an exclusive OR circuit 41, the output of the AND circuit 38 and the output of the comparator 22 enter an exclusive OR circuit 42,
When the selection signal USEA selects the information on the signal A side, the multiplexer 44 is controlled and the exclusive OR circuit 4
Exclusive OR if output of 1 is selected as signal B side
The output of circuit 42 is sent to counter 45. The exclusive OR circuits 41 and 42 and the multiplexer 44 constitute a direction detection circuit 49 that detects the direction of movement of the object. That is, the rotational direction of the motor 1 is detected from the outputs of the comparators 22 and 28, the outputs of the AND circuits 35 and 38, and the selection signal USEA, and the counter 45 is controlled to be incremented or subtracted.

The counter 45 outputs the count value after receiving the reset pulse from the reset pulse generator 16 to the D/A converter 4.
6 and motor 1 as shown in the position signal in Figure 4.
The position signal is sent at a voltage value with little ripple.

Note that the maximum amplitude values of the signals A and B normally increase or decrease slightly in the period of one rotation of the motor due to eccentricity of the rotary encoder 2 with respect to the rotation axis. When this influence cannot be ignored, a circuit is added to detect and hold the local maximum value, and the outputs of the D/A converters 20 and 26 of the tracking circuits 47 and 48 are modulated by the magnitude of this local maximum value. . That is, the peak detection holding circuit 5 shown in FIG.
By adding 9 and multiplier 60 to the circuit of FIG. 3, a more precise position signal can be obtained.

In this embodiment, one period of the signal A or B shown in FIG. 5 is divided into 16 equal parts, and the larger the number of equal parts, the more precise the position signal becomes. Therefore, the number of divisions can be determined as necessary.

(f) Effect of the Invention As explained above, the present invention detects the change in the pseudo sine wave signal generated by the rotary encoder by subdividing the detection level with respect to the position, so it is possible to detect the motor accurately and without ripple. A position signal for detecting the rotational position can be obtained. Furthermore, it has the flexibility to handle rotary encoders with different waveforms of pseudo-sine wave signals by rewriting or replacing the contents of the memory circuit (memory), and is suitable for capstan motors for tape feeding in high-density magnetic recording devices. An excellent effect can be obtained when precisely detecting the rotational position of a motor.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram for generating a position signal from a conventional pseudo sine wave signal, Fig. 2 is a waveform diagram of each part of Fig. 1, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a diagram explaining the operation in Figure 3, Figure 5 is a diagram explaining the recorded contents of the memory, Figure 6 is a detailed diagram of the A and B selection circuit, and Figure 7 is a circuit that removes the effects of eccentricity of the rotating shaft, etc. It is a diagram. 1 is a motor, 2 is a rotary encoder, 3, 4
are comparators, 5 to 8 are monostables, 14 is a counter, 15 is a D/A converter, 16 is a reset pulse generator, 17 is a clock generator, 18, 24,
45 is a counter, 19, 25 is a memory, 20, 2
6, 46 are D/A converters, 21, 22, 27, 2
8 is a comparator, 43 and 44 are multiplexers, 50
is a decoder, 59 is a peak detection and holding circuit, and 60 is a multiplier.

Claims (1)

[Claims] 1. Positions obtained by subdividing one cycle of two-phase signals A or B, which have a phase difference of 1/4 cycle and are generated by a detector according to the motion of an object moving or rotating in two directions. means for storing an amplitude value for the signal; amplitude comparing means for converting the output of the storing means from digital to analog and comparing it with the amplitude of the signal A or B; and adding a clock pulse of a constant period according to the output of the amplitude comparing means. tracking circuits A and B comprising counting means for accessing the storage means; the output of the counting means and the output of the amplitude comparison means are input, and the amplitude center level of the signal A or B is close to the amplitude center level of the signal A or B; a selection circuit that selects one of the signals A and B, and compares each amplitude and zero potential of the signals A and B;
Comparing means A and B outputting whether the amplitude of each of the signals A and B is positive or negative; the output of the amplitude comparing means of the following circuits A and B;
means for determining the direction of motion of said object from a selection signal from said selection circuit and the outputs of said comparison means A and B; logic 0
addition or subtraction is instructed by means for determining the direction of motion of the object, and the output of the logic circuit enables counting, counts the clock pulses, and transmits the counting result to the object. A position detection method consisting of a counting means that outputs a signal indicating the position of the