JP5816830B2 - Encoder - Google Patents

Description

  The present invention relates to a method for accurately detecting speed even at low speed rotation in an encoder for detecting rotation information of a motor.

  2. Description of the Related Art Conventionally, servo motors have been widely used in FA (Factory Automation) system devices such as semiconductor manufacturing devices, robots, and various machine tools to perform highly accurate positioning control. An encoder is used to detect the rotational position of the servo motor. A two-phase pulse having a phase difference of 90 degrees is generated in accordance with the rotation of the motor shaft, and the generated position is counted to detect the rotational position. Further, in recent years, the number of two-phase pulses having a phase difference of 90 degrees and the sine wave and cosine wave signals synchronized with these pulses have been interpolated to achieve high resolution. As means for transmitting the rotational position information detected by the encoder to the host device, the detected two-phase pulses with a phase difference of 90 degrees are converted into differential signals, respectively, and differential pulse signals of A phase signal and B phase signal, Conventionally, a parallel output system that outputs a Z-phase differential pulse signal that outputs one pulse signal by rotation has been generally employed. However, in the parallel output method, the pulse frequency increases as the resolution of the encoder increases, and it is difficult to accurately transmit the pulse signal without being affected by noise or the like. Therefore, in recent years, a technique has been adopted in which position information generated by an encoder is transmitted to a host device by a serial communication method.

  On the other hand, in the FA field, high-speed servo motors and stability at low speeds are required. In the case of a parallel output type encoder, since the number of pulses serving as speed information is small in the low speed range, it becomes difficult to detect the speed. Therefore, various speed detection methods at a low speed have been proposed so far.

  FIG. 8 is a configuration diagram of a speed detection method by a parallel output type encoder, and FIG. 9 shows operations of respective units showing a speed detection method at a low speed. At the time of rotation from the medium speed to the high speed range, the number of pulses of the A phase and the B phase is counted by an up / down counter, and the speed is detected from the difference value counted every predetermined time. Since the number of pulses decreases and the detection error increases in the low speed region, the speed is detected by counting the time between the edges of the A phase and B phase with a counter. FIG. 9 shows an example of a speed detection method in the low speed range. The counter 44 is activated by detecting the falling edge of the A phase signal 50, the rising edge of the B phase pulse signal is detected, and the count value 59 counted by the counter 44 is shown. Is output to the position detection signal generation means 41, and the position detection signal generation means is configured to obtain highly accurate speed data 56 even at low speed from the count value 59 (for example, Patent Document 1 and Patent Document 2). ).

JP 2003-262649 A JP 2009-85716 A

  However, the methods of Patent Document 1 and Patent Document 2 are effective for a parallel output type encoder that outputs A-phase and B-phase pulses, but in the case of an encoder that achieves high resolution by interpolation division. , A phase and B phase pulses cannot be generated. For this reason, speed detection in the low speed range is obtained from the amount of change in the rotational position for a certain period of time as in the case of medium speed to high speed range.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and an object of the present invention is to provide an encoder capable of accurately detecting speed even at low speed rotation in an encoder that detects rotation information of a motor.

  In order to solve the above-mentioned problem, the encoder according to claim 1 rotates in synchronization with the motor shaft, detects a rotational position, and outputs position detection data, and a position detected by the position detector. In an encoder that transmits detection data to a host device, when the position detection data detected by the position detector changes, a data storage that stores the position detection data, the position detection data stored in the data storage, and The latest position detection data detected by the position detector is compared, and when the position detection data changes, the data determination unit that calculates the change amount of the position detection data, and the position detection data detected by the position detector has changed. It consists of a counter that starts counting at the timing and then counts the time until the position detection data changes. The counter values are transmitted to the host system.

  The encoder according to claim 2, when there is no change in the position detection data detected by the position detector during a certain period transmitted from the encoder to the host device, the change amount of the position detection data is set to zero, The current counter count value which is continuously counted by the counter is transmitted to the host device.

  According to a third aspect of the present invention, there is provided the encoder according to the present invention, wherein the time from the change point of the position detection data detected by the position detector to the transmission to the host device is transmitted by the counter during a certain period of time from the encoder to the host device. The counter count value is transmitted to the host device.

  The encoder according to claim 4, wherein the data determination unit for determining a change in position detection data calculates a change amount of the position detection data at a change of n times (n is an integer of 2 or more), and the counter Counts the time to change n times.

  Further, in the encoder according to claim 5, the data determination unit that determines a change in position detection data is a high-order Mbit (M is an integer of 1 or more) of effective Lbits of position detection data (L is an integer of 2 or more). , L> M).

Further , the change amount of the position detection data and the counter count value counted by the counter are transmitted to the host device at regular intervals.

Further, it means for transmitting the position detection data to the host device is a serial communication.

  According to the encoder of the first aspect, even when the motor rotates at a low speed and the number of pulses is small, that is, when the change amount of the position detection data is small, the change amount of the position detection data and the time until the change occur within the encoder. Since it is possible to accurately count with the counter, it is possible to improve the accuracy of speed detection during low-speed rotation.

  Further, according to the encoder of the second aspect, even when there is no change in the position detection data during the period for transmitting the position detection data to the host device, the information indicating that the motor shaft is stopped and the motor shaft is stopped. Since the elapsed time is output, it can be easily determined that the motor shaft has stopped.

  According to the encoder of the third aspect, since it is possible to detect the time from when the position detection data last changed until the position detection data is transmitted to the host device, the detection delay is accurately corrected. Therefore, responsiveness can be improved.

  Further, according to the encoder of the fourth aspect, stable data can be generated with high responsiveness by processing the change of the position detection data not a single data but a plurality of times. it can.

  Further, according to the encoder of the fifth aspect, since the speed detection is performed using the high-order bit with high accuracy of the position detection data, it is possible to detect the speed at the time of low-speed rotation with higher accuracy.

Further , since the host device can obtain information on the amount of change in the position detection data and the time until the change occurs every fixed period, the conversion from the position detection data to the speed data can be easily performed.

Further , by transmitting the differential signal through serial communication, it is possible to detect the speed during low-speed rotation with the aim of improving the noise resistance and reducing the cost by saving the signal line. Therefore, in a high-resolution encoder based on interpolation division, an encoder that can accurately detect speed without sacrificing responsiveness even during low-speed rotation is provided to accurately detect the amount and time of change in position detection data. can do.

1 is a block diagram of an encoder speed detection circuit according to a first embodiment of the present invention. 1 is a block diagram of a data determiner according to the first embodiment. The figure which shows the various operation waveforms of the speed detection circuit of the encoder of Example 1. The figure which shows the various operation waveforms of the speed detection circuit of the encoder of Example 2. Block diagram of encoder speed detection circuit in embodiment 3 The figure which shows the various operation waveforms of the speed detection circuit of the encoder of Example 3. The figure which shows the various operation waveforms of the speed detection circuit of the encoder of Example 4. Block diagram of encoder speed detection circuit in conventional example The figure which shows the various operation waveforms of the speed detection circuit of the encoder of a prior art example

A first aspect of the present invention is rotated in synchronism with the motor shaft, has a position detector outputs the position detection data by detecting the rotational position and transmits the position detection data detected by the position detector to the higher-level device In the encoder, the position detector is obtained by generating two sine wave signals having a phase difference of 90 degrees into two pulse signals having a phase difference of 90 degrees by a comparator and counting up / down from the two pulse signals. Combining the upper Nbit (N is an integer) of the incremental data and the lower Kbit (K is an integer) obtained by interpolating the two sine wave signals having the phase difference of 90 degrees, Lbit (L = N + K) A position detection timing signal serving as an operation start signal of the position detector and a timing generation circuit for generating a counter clock; Check whether there is a change in the position detection data for each position detection timing signal, and when the position detection data changes, a data storage that stores the changed position detection data, and a position stored in the data storage The detection data is compared with the latest position detection data detected by the position detector, and when the position detection data changes, a data determination unit that calculates the amount of change in the position detection data, and the position detected by the position detector The counter starts counting at the timing when the detection data changes and then counts the time until the position detection data changes using the counter clock. The amount of change in the rotational position and the counter count value counted by the counter are By transmitting serial communication to the host device at regular intervals, the motor rotates at a low speed and the number of pulses is small. Even when the amount of data change is small, the amount of change in position detection data and the time until the change can be accurately counted by the counter inside the encoder, so the accuracy of speed detection during low-speed rotation can be improved. .

  According to a second aspect of the present invention, when there is no change in the position detection data detected by the position detector during a certain period transmitted from the encoder to the host device, the change amount of the position detection data is set to zero, and the counting is continued by the counter. By transmitting the current counter count value to the host device, even if there is no change in the position detection data during the cycle of transmitting the position detection data to the host device, the information indicating that the motor shaft is stopped, and the motor Since the elapsed time since the shaft stopped is output, it can be easily determined that the motor shaft has stopped.

  According to a third aspect of the invention, the counter counts the time from the change point of the position detection data detected by the position detector to the transmission to the host device during a certain period of time transmitted from the encoder to the host device. By transmitting the numerical value to the host device, it is possible to detect the time from when the position detection data last changed until the position detection data is transmitted to the host device, so that the detection delay can be accurately corrected. Therefore, responsiveness can be improved.

  According to a fourth aspect of the present invention, the data determination unit for determining a change in the position detection data calculates a change amount of the position detection data at the time of changing n times (n is an integer of 2 or more), and the counter changes n times. By counting the time, it is possible to generate stable data with high responsiveness by processing the change of the position detection data not a single data but a plurality of times.

  According to a fifth aspect of the present invention, the data determiner for determining a change in the position detection data is an upper Mbit (M is an integer equal to or greater than 1 and L> M) of valid Lbits (L is an integer equal to or greater than 2) of the position detection data. By determining the change in the speed, the speed detection is performed using the high-order bit with high accuracy of the position detection data, so that the speed detection at the low speed rotation can be performed with higher accuracy.

In addition , by transmitting the change amount of the position detection data and the counter count value counted by the counter to the host device at regular intervals, the host device can change the change amount of the position detection data at every constant cycle. Since time information can be obtained, conversion from position detection data to velocity data can be easily performed.

In addition , since the means for transmitting the position detection data to the host device is serial communication, the differential signal is transmitted by serial communication, thereby improving noise resistance and reducing costs by reducing signal lines. It is possible to detect the speed during low-speed rotation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

Example 1
An encoder according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of an encoder speed detection circuit according to the first embodiment, FIG. 2 is a block diagram of a data determination unit, and FIG. 3 shows various operation waveforms of the speed detection circuit. Each operation will be described below.

  Reference numeral 1 denotes a position detector, which is synchronized with the upper Mbit (M is an integer) of the incremental data obtained by up / down counting two pulse signals of phase A and phase B having a phase difference of 90 degrees, and these pulse signals. The position detection data 21 of Lbit (L = M + K) is generated by synthesizing the lower Kbit (K is an integer) obtained by interpolating the two sine wave signals having a phase difference of 90 degrees. When the signal forming the upper bit is the incremental data as described above, a reference position (Z phase) output once per rotation is required, and the position of the rotor is determined after detecting the Z phase. Recently, the number of absolute-type encoders that determine the position within one point immediately after startup has increased, forming the same number of M tracks as the upper Mbit, and dividing the gray code pattern into 2 n powers in one rotation It is formed to become. Further, for the purpose of miniaturization, a device in which an M code pattern is formed by arranging M detectors on the periphery of one track is often used.

  Reference numeral 2 denotes a data determination unit, which includes a position detection data subtractor 11, a data holder 12, and a data update timing detector 13 as shown in FIG. The data update timing detector 13 generates timing for updating data used for speed detection. The storage position detection data 27 stored in the data storage 3 described later and the position detection data detected by the position detector 1 are used. 21 are compared, and if a difference occurs, a data update timing signal 23 is output. The position detection data differentiator 11 detects the amount of movement of the position detection data. Upon receiving the data update timing signal 23 from the data update timing detector 13, the position detection data difference unit 11 stores the stored position detection stored in the data storage 3 described later. The difference between the data 27 and the position detection data 21 detected by the position detector 1 (position detection data 21−stored position detection data 27) is taken, and position detection difference data 24 is output. The data holder 12 is for holding the latest position detection data 21, and holds the position detection data 21 by the data update timing signal 23 output from the data update timing detector 13, and then updates the data. Until the timing signal 23 is input, the held data is output as the update position detection data 26.

  Reference numeral 3 denotes a data storage unit that stores the updated position detection data output from the data determination unit 2 and outputs it as storage position detection data 27, which is compared with the latest position detection data 21 detected by the position detector 1. Thus, the rotation of the motor shaft is detected.

  Reference numeral 4 denotes a counter. When a signal of the data update timing signal 23 output from the data determination unit 2 is received, a value counted by the counter is held, counter count latch data 32 is output, and a counter count value 25 Is cleared to zero.

  A timing generation circuit 6 generates a position detection timing signal 20 that is an operation start signal of the position detector 1 and a counter clock 22 that causes the counter 4 to operate the counter.

  Reference numeral 5 denotes a transmission data generation circuit that holds each data so that each detected data can be transmitted, and outputs the held data in response to a request command of an information transmission request signal 31 from the transmission / reception circuit 7 described later. To do.

Reference numeral 7 denotes a transmission / reception circuit. When a data request is received by received data 30 from a host device (not shown), the corresponding data is returned as transmission data 29 to the host device. The request for the received data 30 includes position information, temperature information, error information, speed information, and the like.

  The above is an explanation of the role of each block. Next, the operation during low-speed rotation will be described with reference to FIG.

  Tcom1, Tcom2,... Are timings for receiving data requests from a host device (not shown), and Tcom represents a data request cycle. The position detector 1 generates position detection data 21 for each position detection timing signal 20 periodically generated from the timing generation circuit 6, but in the case of low speed rotation, the position detection data 21 is shown in FIG. The case where does not change continues. In this example, the position detection data 21 changes once between Tcom1 and Tcom2. When the position detection data 21 changes from (n + 1) to (n + 2), this difference (n + 2) − (n + 1) is calculated to generate position detection difference data 24 (dif2). Further, the data update timing signal 13 is output at the same timing, and the counter count value 25 (cc1) counted by the counter 4 at that time is held as the counter count latch data 32. Further, the counter count value 25 calculated by the counter 4 is simultaneously cleared to zero and starts counting again. When the transmission data generation circuit 5 receives the information transmission request signal 31 which is a data request from the host device, the transmission data generation circuit 5 generates counter data from the data (cc1) held in the counter count latch data 32 and the counter count latch information 28b. The position detection difference data latch information 28a is output from the data (dif2) held in the position detection difference data 24. The data generated here is transmitted to the host device as transmission data 29 by the transmission / reception circuit 7.

  Further, between Tcom2 and Tcom3, the position detection data 21 is an example in the case of changing twice. Since the operation is the same as in the case of the above-mentioned change of 1 degree, the counter count is counted every time the position detection data 21 changes. The latch data 32 and the position detection difference data 24 are generated, and the data at the time of receiving the information transmission request signal 31 which is a data request from the host device is fetched as counter count latch information 28b and position detection difference data latch information 28a, respectively. Is output.

  With the above-described configuration, even when the motor rotates at a low speed and the number of pulses is small, that is, the amount of change in the position detection data 21 is small, the amount of change in the position detection data and the time until the change occur inside the encoder. Since it is possible to accurately count with the counter, it is possible to improve the accuracy of speed detection during low-speed rotation.

(Example 2)
A second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment is the operation of the transmission data generation circuit 5 when the position detection data 21 does not change during the data request period Tcom from the host device. This will be described below.

  FIG. 4 shows various operation waveforms of the speed detection circuit of the encoder according to the second embodiment. Since there is no change in the position detection data 21 between Tcom1 and Tcom2, and between Tcom3 and Tcom4, the signal of the data update timing signal 23 is not generated, the position detection difference data 24 is not updated, and the counter count value 25 is not cleared. Continue counting. In such a case, when the transmission data generation circuit 5 receives the information transmission request signal 31 from the host device at the timing of Tcom2 and Tcom4, it sets the position detection difference data latch information 28a to zero, and the counter count latch information 28b The counter count value 25 being counted by the counter 4 is set. If the host device obtains such information, the position detection data 21 does not change during the data request period Tcom, and the motor shaft is stopped, and the stop time can be detected.

With the above configuration, even when there is no change in the position detection data during the period for transmitting the position detection data to the host device, the information indicating that the motor shaft is stopped and Since the elapsed time is output, it can be easily determined that the motor shaft has stopped.

(Example 3)
A third embodiment of the present invention will be described with reference to FIGS. The difference from the first embodiment and the second embodiment is that a counter value holder 8 is provided that receives the information transmission request signal 31 from the host device and holds the counter count value 25 counted by the counter 4. This will be described below.

  FIG. 5 is a block diagram of an encoder speed detection circuit according to the third embodiment, and FIG. 6 shows various operation waveforms of the encoder speed detection circuit according to the third embodiment. A counter value holder 8 receives a counter count value 25 which is an output value from the counter 4. When the information transmission port request signal 31 is received from the host device, the counter value holder 8 fetches the counter value counted by the counter count value 25 and the count value fetched into the transmission data generation circuit 5 as shown in FIG. Counter count latch information 28c is output. The transmission data generation circuit 5 generates data for transmitting the position detection difference data latch information 28a and the counter count latch information 28b and 28c to the host device, and transmits the data to the host device via the transmitter circuit 7. . The counter count latch information 28c includes a time from when the previous position detection data 21 is changed to when data is transmitted to the host device (for example, a count count value 25 when the position detection data 21 changes between Tcom1 and Tcom2). Is cc1, and the time until data is transmitted to the host device thereafter includes tc2), so that the host device can confirm the delay time of the detected speed data.

  With the configuration as described above, it is possible to detect the time from when the position detection data last changed until the position detection data is transmitted to the host device, so that the detection delay can be accurately corrected. Therefore, responsiveness can be improved.

Example 4
Embodiment 4 of the present invention will be described with reference to FIG. The difference from the first to third embodiments is that the data update timing signal 23 is generated when the position detection data 21 changes n times (n is an integer of 2 or more). This will be described below.

  The data determination device 2 configured in the fourth embodiment compares the storage position detection data 27 stored in the data storage device 3 with the position detection data 21 detected by the position detector 1, and counts the number of times the difference has occurred. When the set count number is reached, the data update timing signal 23 is output, and the counter is cleared. FIG. 7 shows an example in which the counter set value is 2, and when the position detection data 21 changes twice, the data update timing signal 23 is generated. The position detection data 21 changes from n + 1 to n + 2 once between Tcom1 and Tcom2, and when a data request is received from the host device at Tcom2, the position detection difference data latch information 28a is zero, and the counter count latch information 28b is current. The count value cc1 is transmitted. Next, between Tcom2 and Tcom3, the position detection data 21 has changed from n + 2 to n + 3, and the position detection data 21 has changed for the second time. Therefore, when Tcom3 receives a data request from the host device, the position detection data 21 The difference data latch information 28a transmits dif3 which is a difference value between n + 3 and n + 1, and the counter count latch information 28b transmits a count value cc2 as if the position detection data 21 changes twice. When n times of data is processed together by the host device, the sampling time (Tcom) is too long and the responsiveness deteriorates. However, the position detection data generated by the encoder is sufficiently sampled compared to Tcom. Since it is short, responsiveness is not deteriorated.

  With the configuration described above, stable data can be generated with high responsiveness by processing the change of the position detection data 21 not a single data but a plurality of times.

(Example 5)
A fifth embodiment of the present invention will be described. The difference from the first embodiment to the fourth embodiment is that the data determination unit 2 that determines the change of the position detection data 21 is limited in the effective bit to be determined. This will be described below.

  The data determiner 2 detects that the position detection data 21 detected by the position detector 1 and the storage position detection data 27 stored in the data storage 3 are different as described above. Since all the bits of the position detection data 21 are targeted, the lower bits of the position detection data 21 may fluctuate due to noise or the like. Therefore, the change of the upper Mbit (M is an integer equal to or greater than 1 and L> M) is determined with respect to the effective Lbit (L is an integer equal to or greater than 2) of the position detection data 21 determined by the data determination unit 2. Configure.

  With the configuration as described above, speed detection is performed using higher-order bits with high accuracy of the position detection data, so that it is possible to more accurately detect the speed during low-speed rotation.

(Example 6)
A sixth embodiment of the present invention will be described. The difference from the first to fifth embodiments is that the change amount of the position detection data and the counter count value counted by the counter are transmitted to the host device at regular intervals. This will be described below.

  A system including an encoder is configured so that an information transmission request signal 31 that is a data request from a host device is sent at a constant cycle. The encoder generates counter count latch information 28 b and 28 c and position detection difference data latch information 28 a by the method of the first to fifth embodiments, and outputs these as transmission data 29.

  With the configuration as described above, the host device can obtain information on the amount of change of the position detection data 21 and the time until the change at every fixed period, so that conversion from position detection data to speed data is easy. Can be done.

  Furthermore, the transmission data 29 is converted into serial data and transmitted by serial communication using a differential signal, thereby detecting the speed during low-speed rotation with the aim of improving noise resistance and reducing the cost by reducing the number of signal lines. be able to.

  Further, in the first to sixth embodiments, the rotary encoder has been described as an example. However, the same effect can be obtained by adopting the same configuration for a linear encoder.

  The encoder according to the present invention can improve the speed detection accuracy at low speed, and is therefore used for driving a low-speed transport machine or an industrial robot arm that is driven directly at low speed without using a gear. This is particularly effective for position detection devices.

DESCRIPTION OF SYMBOLS 1 Position detector 2 Data determination device 3 Data storage device 4 Counter 5 Transmission data generation circuit 6 Timing generation circuit 7 Transmission / reception circuit 11 Position detection data differentiator 12 Data holder 13 Data update timing detector 20 Position detection timing signal 21, 54 Position detection data 22 Counter clock 23 Data update timing signal 24 Position detection difference data 25 Counter count value 26 Update position detection data 27 Stored position detection data 28a Position detection difference data latch information 28b, 28c Counter count latch information 29 Transmission data 30 Reception data 31 Information transmission request signal 32 Counter counting latch data 40 Up / down counter 41 Position detection signal generating means 43 Edge detection 44 Counter 50 A phase signal 51 B phase signal 52 AB phase counter value 3 edge detection pulse signal 55 counter values 56 velocity data 58 up / down switching signal 59 between edges counter count latched information

Claims (5)

In encoder rotated synchronously with the motor shaft, it has a position detector outputs the position detection data by detecting the rotational position and transmits the position detection data detected by the position detector to the higher-level device,
The position detector generates two sine wave signals having a phase difference of 90 degrees into two pulse signals having a phase difference of 90 degrees by a comparator, and increments / decrements the incremental data obtained from the two pulse signals. The position of Lbit (L = N + K) by combining upper Nbit (N is an integer) and lower Kbit (K is an integer) obtained by interpolating the two sine wave signals having a phase difference of 90 degrees. Generating detection data,
A position detection timing signal that serves as an operation start signal of the position detector and a timing generation circuit that generates a counter clock;
A data storage for checking the presence or absence of a change in the position detection data for each position detection timing signal, and storing the changed position detection data when the position detection data changes;
A data determination unit that compares the position detection data stored in the data storage unit with the latest position detection data detected by the position detector, and calculates a change amount of the position detection data when the position detection data changes;
The counter starts counting at the timing when the position detection data detected by the position detector changes, and then counts the time until the position detection data changes by the counter clock.
An encoder characterized in that a change amount of the rotational position and a counter count value counted by the counter are transmitted to the host device by serial communication at regular intervals. When there is no change in the position detection data detected by the position detector during a certain period transmitted from the encoder to the host device, the change amount of the position detection data is set to zero, and the current counter meter continues counting with the counter The encoder according to claim 1, wherein a numerical value is transmitted to the host device. The counter counts the time from the change point of the position detection data detected by the position detector to the transmission to the host device during a certain period of time transmitted from the encoder to the host device, and the counter count value to the host device. The encoder according to claim 1, wherein the encoder is transmitted. The data judgment unit for judging the change of the position detection data calculates the change amount of the position detection data at the time of changing n times (n is an integer of 2 or more), and the counter counts the time of changing n times. The encoder according to any one of claims 1 to 3, characterized in that: The data determination unit for determining a change in position detection data determines a change in the upper Mbit (M is an integer of 1 or more and L> M) of the Lbit (L is an integer of 2 or more) of the position detection data. The encoder according to any one of claims 1 to 4, wherein: