JPH04346025A - Detecting apparatus for open phase of output pulse of encoder - Google Patents

Abstract

PURPOSE:To obtain an apparatus which can detect the open phase of the output pulse of an encoder accurately and quickly. CONSTITUTION:The pulses of a rotary encoder 12 which outputs the pulse signal in accordance with the rotation of a motor are counted with a counter 341 between the angles which are obtained by dividing one rotation of the motor at the specified angles. The counted value is compared with a specified value in a comparator 344. When the value is less than the specified value, it is judged that the phase of the output pulse of the encoder is open. The output pulse trains from the encoder are counted between the angles which are obtained by dividing rotation of the motor into the angles of the small sections, and the value 18 compared with the specified value. Therefore, the open phase of the pulse can be detected accurately and readily.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an encoder output pulse open phase detecting device, and more specifically, detects the rotational position of a motor output shaft at every predetermined angle, and uses the angle signal to detect phase open detecting of a rotary encoder. This relates to a device that detects phases.

0002

[Prior Art] Conventionally, when controlling the drive of, for example, a sewing machine using an electric motor, the rotation amount of the motor output shaft is generally detected and controlled via a rotary encoder. When rotated, uneven rotation or thermal deformation may occur, resulting in locally missing output pulses, so-called pulse phase loss. In such a case, erroneous detection may occur and abnormal operation may occur, so it is necessary to quickly detect the open phase. For this reason, conventionally, the upper and lower signals of the sewing machine have been used to determine whether the output pulse is out of phase.

0003

[Problem to be solved by the invention] In the case of this prior art,
If there is one or more pulse output between the upper and lower signals of the sewing machine, it is determined that there is no phase loss, so even if there is a loss in the middle of the output pulse, it cannot be detected and it will be considered as abnormal operation during stop control. Something happened.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an apparatus which eliminates the above-mentioned drawbacks of the prior art and is capable of accurately and quickly detecting phase loss in encoder output pulses.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned objects, the present invention provides a phase loss detection device for output pulses of an encoder that outputs pulse signals in accordance with the rotation of a motor.
rotational position detection means for detecting angular positions obtained by dividing one revolution of the motor into predetermined angles; a counting means for counting the number of encoder output pulses generated between the divided angles; and comparing the counted value with a predetermined value; The present invention is configured to include a determining means that determines that the encoder output pulse has an open phase when the count value is less than a predetermined value.

[0006]

[Operation] In this configuration, the amount of rotation of the motor is divided into predetermined angles, and the encoder pulses are counted in small sections between the divided angles, so simply comparing the count value with the predetermined value is enough. Phase loss of a pulse can be easily determined, and pulse loss of phase can be detected accurately and quickly.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory diagram conceptually showing the overall configuration of the present invention, taking as an example the position or speed control of an electric motor to which the present invention is applied.

[0008] Referring to the figure, reference numeral 10 indicates an electric motor, and a rotary encoder 12 and a rotor position detector 14 are arranged in the electric motor. That is, as shown in FIG. 2, a known rotary encoder 12 is coaxially attached to the output shaft 10a of the electric motor, and outputs a pulse train as the motor output shaft 10a rotates. In addition, the surface of the motor output shaft 10a is 90 mm as shown in the figure.
Two sets of magnetic poles, N and S, whose magnetic poles change in degrees are formed at 180 degree intervals, and three sets of rotor position detectors 14a made of magnetoelectric transducer elements are arranged at 120 degree intervals during each rotation. , 14b, 14c are arranged facing each other.

FIG. 3 shows these output signals after pulse shaping, which will be described later. Here, if the output of the rotor position detector 14a is Hu, the output of 14b is Hv, and the output of 14c is Hw, the H and L levels change every 90 degrees as shown in the figure.
Three sets of pulse trains with mutual phase shifts of 120 degrees are obtained,
An angular range obtained by dividing one revolution of the motor output shaft into 12 can be obtained from the rising edge and falling edge of each pulse train. Note that two sets of pulse trains consisting of A and B phases are obtained from the rotary encoder 12 as shown in the lower part of the figure. Figure 4 is an enlarged view of part A in Figure 3.
As is well known, the phases differ by 90 degrees in order to determine the direction of rotation. Here, the CW condition and CCW condition are defined as shown in FIG. In addition, the CCW condition is forward rotation (up count).
direction.

Returning to FIG. 1 again, rotary encoder 1
The output of 2 is input to the position or speed detection section 16 to detect the motor rotational position or speed, and the CPU 18 determines the control value by determining the deviation from the command value based on it.
supplied to the electric motor 10 via the power drive 22;
Adjust the position or speed of the electric motor to a predetermined command value. Further, the output of the rotary encoder 12 and the output of the rotor position detector 14 are sent to an open phase detection section 24 . Since the gist of the present invention is to detect phase loss in the encoder output, the following description will focus on the phase loss detection section 24.

FIG. 6 is a block diagram showing details of the open phase detection section 24. In the figure, rotor position detector 14a
, 14b, 14c (Hu, Hv, Hw signals) are input to differentiating circuits 30a, 30b, 30c, where the edges of the input signals are captured to form a pulse train as shown in FIG. Also, among the outputs of the rotary encoder 12, A
The phase is input to the fourth differentiating circuit 30d, where an output as shown in FIG. It is determined.

Three detection circuits 3 are provided at the next stage of the differentiation circuit 30.
4a, 34b, and 34c are connected. The three circuits have the same type of configuration, and only 34c is shown in detail, but the other circuits 34a and 34b have the same type of rotor position detector signal, and the rest of the configuration is the same (for easy understanding). For convenience, the input signals are shown with symbols A to C). The circuit 34c will be explained below as an example. In this circuit, an open phase is detected using the Hw signal among the rotor position detector output signals as a reference signal.

The detection circuit 34c includes an up/down counter 341, the output (Hw signal) of the differentiator circuit 30c is connected to its reset terminal, and the counter 341
It is reset at the rising edge or falling edge of the w pulse train. The detection circuit 34c also includes a D flip-flop 342, and the Hw signal described above is connected to its clock terminal. On the other hand, the output of the forward/reverse determination circuit 32 is connected to the D terminal. Here, the circuit 32 is at H level when the electric motor 10 rotates forward (CCW condition);
When reversing (CW condition), an L level signal is output. The next stage of the D flip-flop 342 is an OR gate 34.
3 is connected to its input terminal, the output of the forward/reverse determination circuit and the Q-bar output of the D flip-flop 342 are connected, and its output terminal is connected to the up/down switching terminal of the counter 341. The counter 341 performs up counting when the input level is H, and down counting when the input level is L.

A comparator 344 is connected to the next stage of the counter 341. More specifically, the comparator 344 is composed of a matching circuit, which compares the input value with a specified value and switches the output level from H to L when they match. A latch circuit 345 is connected to the next stage of the comparator 344 . Latch circuit 345
The remaining Hu and Hv signals of the rotor position detector output are connected to the comparator 344 via a second OR gate 346.
Latch the contents of. Therefore, the latch circuit 345 has
O from the rising (or falling) edge of the Hw signal
The comparison result between the count value of the counter 341 and the specified value up to the next rising (or falling) edge of the Hu, Hv signal input via the R gate 346 is latched.

A third OR gate 36 is provided at the next stage of the detection circuits 34a, 34b, and 34c, and receives the latch outputs of the three detection circuits 34a, 34b, and 34c. O
The CPU 18 described above is connected to the next stage of the R gate 36, and its output is inputted thereto.

Next, the operation of this device will be explained with reference to FIG. 7 and subsequent figures.

(a) Normal state FIG. 7 shows the output during normal state with no open phase. As shown in the figure, since the rotation direction is normal rotation, the output of the forward/reverse determining circuit 32 becomes H level, and an up-count instruction is given to the counter 341 via the first OR gate 343. In the case of the figure, the counter 341 is reset at the falling edge of the Hw signal, counts up every time the A-phase pulse changes level, and sends the count value to the comparator 344, as shown in the upper part of FIG. Here, if the specified value is "8", the comparator output becomes L level when the count value reaches 8. On the other hand, as shown in FIG. 3, since the Hu signal changes to H level 30 degrees after the Hw signal becomes L level, the latch circuit 345 is activated, latches the output of the comparator 344, and outputs the output from the OR gate 36. Send to. During normal operation, other circuits 34
Since the latch outputs of a and 34b are also at the L level, the output of the OR gate 36 is also at the L level, and the CPU 1
8 inputs the output and determines that there is no open phase.

(b) Phase A phase loss Figure 8 shows a case where the A phase pulse has a phase loss. In this case, when the A phase level change is counted up to "4", the next pulse is an imaginary line. As shown, the normal rotation condition disappears due to the phase loss, and when the B phase rises from the L level to the H level, it is determined that the A phase is at the L level, so that it is determined to be a reverse rotation, and the counter 341 is switched to count down. However, since the A-phase pulse is missing, the down count is not performed. Next, when the B phase falls to the L level, since the A phase is at the L level, it is determined to be normal rotation, and the count is switched to up counting, and the level change of the A phase pulse is read as "5, 6, . . ." Count up. Comparator 34
4 changes the output to L level when the count value reaches the specified value. However, before that, the temperature had passed 30 degrees and Hu
Since the signal level changes, the comparator output becomes H level at that position, and this value becomes the next Hu or Hv.
is latched and sent to the OR gate 36, and the OR gate output also becomes H level, which allows the CPU 18 to detect the phase loss of the pulse, and performs fail-safe control in the case of corresponding processing, such as stop control. You can switch to .

(c) B-phase open phase FIG. 9 shows a case where the B-phase pulse has an open phase. In this case A
After the phase level change is counted up to "4", it is determined to be a reverse rotation, and the count is down to "3", and then it is determined to be a forward rotation, and the up count starts again as "4, 5,..." do. Therefore, in this case as well, an open phase can be detected because the comparator output becomes H level before reaching the specified value "8".

It goes without saying that even if both the A-phase and B-phase pulses are out of phase, this can be detected since the count value passes through 30 degrees before reaching the specified value.

Since this embodiment is configured as described above, 30
It is possible to detect an open phase of a pulse every time, and it is possible to detect an open phase more accurately and earlier than in the past, and to perform the necessary fail-safe control.

In the above-mentioned embodiment, the specified value is "8", but the distance from the rising (or falling) edge of the Hw signal to the next falling (or rising) edge of the Hu or Hv signal is 30 degrees. During this period, approximately 30 encoder pulses are obtained, so when setting the above specified value, the interval between the edges and the number of encoder pulses should be taken into consideration.

Although the present invention has been described by taking as an example the detection of rotational speed using a rotary encoder, it is not limited thereto, and the present invention is not limited to this, but can also be applied to detection of a rotational angle, and furthermore, to detection of a moving distance in a linear direction using a linear encoder. It can also be applied to detection.

[0024]

As explained above, in the present invention, in an encoder output pulse open phase detection device that outputs a pulse signal in accordance with the rotation of a motor, the angular position obtained by dividing one rotation of the motor into predetermined angles can be detected. A rotational position detecting means for detecting, a counting means for counting the number of encoder output pulses generated between the divided angles, and comparing the counted value with a predetermined value, and when the counted value is less than the predetermined value, the encoder output pulse is Since the configuration is equipped with a determination means for determining phase loss, the encoder output pulse train is inspected at the rotation angle divided into small sections, and pulse loss can be accurately detected, and this can be used for control. When performing this, a predetermined fail operation can be performed quickly as necessary.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the overall configuration of the present invention, taking a speed control device as an example.

FIG. 2 is an explanatory perspective view showing the attachment positions of a rotary encoder and a rotor position detector to the electric motor in FIG. 1;

FIG. 3 is a timing chart showing output signals of the rotary encoder and rotor position detector of FIG. 1;

FIG. 4 is an enlarged view of part A in FIG. 3;

FIG. 5 is an explanatory diagram showing the rotation direction of the rotary encoder of FIG. 3;

FIG. 6 is a block diagram showing details of the open phase detection section in FIG. 1;

FIG. 7 is a timing chart showing normal operation in phase loss detection in the circuit of FIG. 6;

FIG. 8 is a timing chart showing detection when the A phase is open in the circuit of FIG. 6;

9 is a timing chart showing detection when the B phase is open in the circuit of FIG. 6; FIG.

[Explanation of symbols]

10 Electric motor 10a Motor output shaft 12 Rotary encoder 14 (a, b, c) Rotor position detector 16 Detection section 18 CPU 22 Power drive 24 Open phase detection section 30 (a, b, c, d) Differential circuit 32 Positive Inverse judgment circuit 34 (a, b, c) Detection circuit 36 OR gate 341 Up/down counter 342 D flip-flop 343 OR gate 344 Comparator 345 Latch circuit 346 OR gate

Claims (3)

[Claims] 1. A phase loss detection device for output pulses of an encoder that outputs a pulse signal in accordance with the rotation of a motor, comprising rotational position detection means for detecting an angular position obtained by dividing one revolution of the motor into predetermined angles; a counting means for counting the number of encoder output pulses generated between angles; a determining means for comparing the counted value with a predetermined value and determining that the encoder output pulse is open-phase when the counted value is less than the predetermined value;
An encoder output pulse open-phase detection device characterized by comprising: 2. The encoder output pulse open-phase detection device according to claim 1, wherein one revolution of the motor is divided into equal parts. 3. The rotational position detection means are 120 mm apart from each other.
It consists of three detectors that detect rotational positions with a degree phase shift, and the number of encoder output pulses during the angle from the signal end from one of the detectors to the next signal end from the other detector. 3. The encoder output pulse open-phase detection device according to claim 1, wherein the encoder output pulses are counted.