JPH02107919A - Encoder phase missing detector - Google Patents

Abstract

PURPOSE:To enable discrimination and detection of a phase missing by judging forward and backward ways of position and speed detection signals to compare and judge the signals with a sample signal with addition and subtraction thereof. CONSTITUTION:By a command of a center controller 2, a servo motor 3 turns a feed shaft 4 in a desired direction to move a tool head 1 to a specified position. Then, a position encoder 5 and a speed encoder 6 output a signal pulse and a position decoder 10 and a speed decoder 8 at the next stage judges whether the movement of the head 1 is forward F or backward A. Then, an output pulse of the decoder 8 is inputted to an addition/subtraction circuit 9 to be counted each in a forward way or backward way and a pulse signal of the position decoder 10 is inputted to an OR circuit 11, which outputs the signal to a resetting circuit 12 to reset a signal pulse being counted with the circuit 9. Here, a comparative judgement circuit 13 compares an integral value of the circuit 9 with a sample integral value to distinguish an output attributed to a phase missing from a signal output being interrupted for a fixed time as caused by a backlash, thereby allowing the device 2 to continue or stop the movement of the head 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an encoder used in a control system for a servo drive mechanism for positioning a tool head of an NC machine tool such as a machining center or a work table. .

(Prior art) According to the prior art, the encoder, which includes a signal detection section, a signal amplification section, a waveform shaping section, and an output section, is used for positioning tool holding means or workpiece holding means of an NC machine tool such as the machining center. outputs detection signals related to movement and movement speed. In order to detect the moving direction of the tool holding means or workpiece holding means, this detection signal generally consists of two types of signals: an A signal and a B signal having a predetermined phase difference from the A signal. The two types of A and B signals are formed by line drivers into binary signals consisting of A and A forward direction signal
Alternatively, it is output as a reverse direction signal to downstream control means. At this stage, when inputting the binary A signal to the moving direction determining means, each inverted signal is input to a set of EX-OR circuits provided in parallel (A and X are input to one EX-OR circuit). (B and 100 are input to the other EX-OR circuit), and the presence or absence of an open phase is detected based on the output. In other words, when outputs that are originally out of phase become in phase, it is determined that there is an open phase. Alternatively, in closed-loop positioning control, the difference between the movement command signal input to the position error register and the position movement signal input from the position encoder to the position error register via the decoder circuit is a predetermined value (for example, 10 to 20%), it was determined that an open phase had occurred. Alternatively, instead of providing the above-mentioned EX-OR circuit resistor for the output signal from the line driver, a method such as resistor division may be used to reduce the signal to 0 volts (always +5 or -5 A sensor was installed for each phase to detect 0 volts, and when 0 volts was detected, it was determined that an open phase due to wire breakage had occurred.

(Problem to be Solved by the Invention) In the former of the above conventional techniques, the line driver must be installed for each phase, and as a result, the number of cores of the signal conductor downstream of the output signal is doubled. Moreover, many signal processing circuits were required before outputting the signal whose direction was determined.

On the other hand, the output signal from the line driver generally contains a considerable amount of noise, and even if the detection means is normal, the noise causes the EX-OR circuit to detect the in-phase component, causing the EX-OR circuit to frequently detect the in-phase component. In some cases, the detection was activated as a disconnection condition.

In order to deal with this false disconnection, a filter circuit formed of capacitance, induction, and resistance is generally inserted and installed on the input side of the EX-OR circuit, but this filter circuit inevitably has a phase advance. , or to form a slow-phase circuit, it is difficult to achieve performance that can handle noise at all frequencies, and due to variations between elements, phase shifts are likely to occur, resulting in the in-phase being detected as a disconnection. was there. Therefore, a resistor and a capacitor are inserted to supplementally increase the time constant on the output side, but this is not satisfactory. In any case, I was only able to detect a specific pattern of disconnection.

In the latter case, if an open phase occurs during a movement command and the remaining movement amount can overflow the position error register, or if the position error register is 10 to 20% (the maximum of the mechanical system). (amount of position error register at the time of delay),
Open phase detection is possible only when the forward or reverse output signal from the detection means is completely 0, and in other cases (for example, when stopped), open phase detection is not performed. If the amount is small, the error will not be excessive and open phase detection will not be possible. On the other hand, it is extremely difficult to uniformly set the conditions for determining the percentage by which the position error register determines that a phase is missing.Moreover, when the output gain of the detection means is changed, it is determined that a phase is missing. The percentage value of the position error register must also be changed, and is subject to various restrictions depending on usage conditions.

Furthermore, even if a circuit is incorporated so that the output of the detection means becomes 0 volts in the event of a wire breakage, and a voltageless sensor is provided for each phase, essentially only phase loss due to wire breakage can be detected, which is expensive. Although it exists, it is not practical.

As mentioned above, the control system is redundant in order to ensure the safety of the operator and the machine from sudden accidents such as runaway without being able to accurately detect the position or speed of the tool or workpiece holding means. Since the positioning of the tool or workpiece holding means is controlled by means such as imparting properties, it has not been possible to make the machine tool function effectively to the upper limit of its performance.

Therefore, from one of the prior art techniques, the present invention detects a detection signal related to positional movement and drive speed for positioning of the tool holding means or workpiece holding means of the NC machine tool without converting it into a binary signal. , there is no need to provide a line driver, there is no increase in the number of signal conductor cores, and there is no need for signal processing by an EX-OR circuit.
The filter circuit and time constant circuit related to the X-OR circuit are not added, eliminating the adverse effects of noise and eliminating hardware circuits without impairing responsiveness. Also, compared to other conventional technologies, position error can be reduced. Without installing a register, it eliminates the ambiguity of the decision condition such as determining an open phase based on the magnitude of the error amount % value registered in the register, and the tool holding means or workpiece holding means It is now possible to detect phase loss even when the wire has been positioned and stopped.Furthermore, we have abolished the conventional technology circuit that was only capable of detecting wire breakage. We provide an encoder phase loss detection device that clearly distinguishes between signal output that is interrupted and phase loss, and accurately detects phase loss, including disconnection, so that the performance of the machine tool can be safely maximized. The problem to be solved is to

(Means for solving the problem) The technical means for solving the above problem is as shown in the basic configuration of the encoder open phase detection device (PDC).
), a moving body (H) positioned by a servo drive means (S)
) position detection means (P
), and a speed detecting means (V) which is provided separately from the position detecting means (P) and outputs a signal according to the driving speed of the servo driving means (S). in a closed loop position control servo system (CLS), comprising: direction determining means (DC) for determining each of the output signals from the two detecting means (P and V) into a forward direction output signal or a reverse direction output signal; The one detection means (P
, or V) via the direction determining means (DC), adding or subtracting the forward direction output signal or the backward direction output signal, respectively.
), and a logical sum operation for performing a logical sum operation on the forward direction output signal and the backward direction output signal outputted from the other one of the detection means (V or P) via the direction determining means (DC). means (OR); and reset means (R) for resetting the addition/subtraction operation means (AD) by the output signal from the logical sum operation means (OR).
and a comparison judgment means (D) for comparing and judging the output signal of the addition/subtraction calculation means (AD) with a preset model signal; and as a result of the comparison judgment by the comparison judgment means (D>, the other one is detected. The object of the present invention is to provide a configuration including phase loss detection means (DD) for detecting phase loss in the output signal from the means.

(Function) According to the encoder phase loss detection device (PDC) having the above configuration, the servo drive means (S> moves the movable body (H) to be positioned by the mechanical means (SH).

First, the operation when detecting an open phase of the position detection means (P) will be described.

The position detection means (P) detects the moving body (H) and the mechanical means (S).
HP), which receives the movement of the moving body (H) and outputs it as a multi-phase signal that corresponds to the moving distance and has a phase difference of a predetermined angle.
Input to C).

The speed detection means (V) detects the moving body (H) and the mechanical means (S
HV), driven by a moving body (I
(), outputs a multi-phase signal corresponding to the moving speed and having a phase difference of a predetermined angle, and inputs the signal to the direction determining means (DC).

The direction determining means (DC) detects the phase rotation direction of each input signal, determines whether the movement of the moving object (I) is in the forward direction or in the reverse direction, It is output as a forward direction output signal (FS) or a reverse direction output signal (AS) and inputted to addition/subtraction operation means (AD) and logical sum operation means (OR), respectively.

The addition/subtraction calculation means (AD) adds or subtracts the forward direction output signal (FS) or reverse direction output signal (AS) inputted from the speed detection means (V) via the direction determination means (DC), respectively. do.

The logical sum operation means (OR) performs an OR operation on the forward direction output signal (FS) and the reverse direction output signal (AS) which are inputted from the position detection means (P) via the direction determination means (DC). , the output thereof is input to the reset means (R) as a logical sum signal (OR3).

When the reset means (R) receives the logical sum signal (OR3), it outputs a reset signal (R3) and resets the addition/subtraction operation means (AD) from time to time.

While the reset operation is not performed, the addition/subtraction calculation means (A
The forward direction output signal (FS) or reverse direction output signal (AS) subjected to the addition or subtraction processing in step D) is integrated, and the integrated value (φ) is outputted to the comparison/judgment means (D).

The comparison/judgment means (D) uses the input integrated value (φ) by the model signal setting means (T) to determine whether φ is φ≧−p or φ with respect to a preset model integrated value (p>).
≦−p or φ≦+p or φ≧+p
Compare and judge whether it is or not.

If φ≧−p and φ≦+p, it is assumed that the state is normal and includes normal backlash, and the phase loss is not detected, and a program continuation signal (OK) is output to the servo drive means (S) to continue the program. If φ≦−(p+1) or φ≧+(p+1), an “abnormality” is detected, that is, an open phase is detected, and an open phase, disconnection, or other malfunction occurs (NO). )
A signal is output to the servo drive means (S).

The servo drive means (S) receives the (NO) signal and instructs the moving body (H) to decelerate, yield (gradually advance the program while checking the surrounding conditions), interrupt, and so on according to a preset program. Or have them take measures such as suspension.

As a result of the comparative judgment, the phase loss detection means (DD) detects that the output signal from the position detection means (P) is out of phase in the position detection means (P) and the speed detection means (V). detect that there is a

Next, the operation of the speed detecting means (V) in detecting phase loss will be described with reference to FIG.

The speed detection means (V) detects the moving body (H) and the mechanical means (S
HV) is coupled and driven by a moving body (H)
, and outputs a multi-phase signal corresponding to the moving speed and having a phase difference of a predetermined angle, and inputs the signal to the direction determining means (DC).

The position detection means (P) detects the moving body (H) and the mechanical means (S).
HP), which receives the movement of the moving body (H) and outputs it as a multi-phase signal that corresponds to the moving distance and has a phase difference of a predetermined angle.
Input to C).

The direction determining means (DC) detects the phase rotation direction of each input signal, determines whether the movement of the moving object (H) is in the forward direction or in the reverse direction, and determines whether the motion of the moving body (H) is in the forward direction or in the reverse direction. It is output as a direction output signal (FS) or a reverse direction output signal (AS), and is inputted to addition/subtraction calculation means (AD) and logical sum calculation means (OR), respectively.

The addition/subtraction calculation means (AD) adds or subtracts the forward direction output signal (FS) or reverse direction output signal (AS) inputted from the position detection means (P) via the direction determination means (DC), respectively. do.

The logical sum operation means (OR) performs an OR operation on the forward direction output signal (FS) and the reverse direction output signal (AS) inputted from the speed detection means (V) via the direction determination means (DC). , the output thereof is input to the reset means (R) as a logical sum signal (OR3).

When the reset means (R) receives the logical sum signal (OR3), it outputs a reset signal (R8) and resets the addition/subtraction operation means (AD) from time to time. A forward direction output signal (FS) subjected to addition or subtraction processing by an addition/subtraction calculation means (AD) while the reset operation is not performed;
Alternatively, the backward direction output signals (AS) are respectively integrated, output as an integrated value (φ), and inputted to the comparison/judgment means (D).

The comparison/judgment means (D) compares and judges the inputted integrated value (φ) with a model integrated value (p) set in advance by the model signal setting means (T), and determines the speed detection means (V).
In this case, for example, if the resolution ratio of the speed detection means (V) and the position detection means (P) is a:b, as in the case of detecting an open phase of the position detection means (P) by , φ is -b/ap≦φ≦+b/ap, it is considered to be “normal” or due to normal backlash, and the program continuation signal (OK) is sent to the servo drive means (S ) and continue the program, φ≦−(b/ap+1> or φ≧+(b/a
p+1), “'abnormality°”, that is, an open phase is detected,
It is determined that a disconnection or other malfunction has occurred (
No) Outputs the signal and performs deceleration, yield, interruption, etc. as described above.
Or have them take measures such as suspension.

As a result of the comparative judgment, the phase loss detection means (DD) detects that the output signal from the speed detection means (V) is out of phase in the position detection means (P) and the speed detection means (V). detects that

(Embodiment) Next, the structure and operation of an embodiment of the encoder open phase detection device according to the present invention will be explained with reference to block functional diagrams shown in FIGS. 3 and 4.

The tool head 1 corresponding to the moving body (H) is connected to the central control unit N.
X, Y, by servo drive means controlled by
It is possible to move on the Z-axis and position three-dimensionally,
Since the above three axes have exactly the same structural effect, hereafter X axis 1
The explanation will be limited to the axis only.

The tool head 1 is screwed onto a feed shaft 4.

A servo motor 3 is connected to one end of the feed shaft 4 via a reducer.
are connected. The feed shaft 4 and the servo motor 3 are the aforementioned mechanical means (SH) and servo drive means (S), respectively.
corresponds to Further, a speed encoder 6 is attached to the rear of the servo motor 3 so as to be directly connected to the shaft. The speed encoder 6 corresponds to the speed detection means (V) described above. A position encoder 5 corresponding to a position detection means (P) is directly connected to the other end of the feed shaft 4 so as to eliminate input errors due to torsion of the drive torque of the feed shaft 4.
It is designed to be driven by the rotation of the In addition to the position encoder 5 and speed encoder 6, the servo motor 3, central control unit 2, etc. constitute a well-known closed loop servo control system (dotted chain line in the figure).

Next, a first embodiment of an open phase detection device for detecting an open phase of the position encoder 5 will be described with reference to FIG.

The speed encoder 6 is connected to a speed decoder 8, which corresponds to direction determining means (DC), and the speed decoder 8 performs addition and subtraction, which corresponds to addition and subtraction calculation means (AD), by two signal lines FS and AS for forward and reverse directions. Connected to circuit 9.

The position encoder 5 is similarly connected to a position decoder 10 corresponding to a direction determining means (DC), and the position decoder 10 is connected to a logical sum operation means (OR) by two forward and reverse signal lines FS and ΔD. It is connected to the corresponding OR circuit 11.

The OR circuit 11 is connected to a reset circuit 12 corresponding to reset means (R), and the reset circuit 12 is connected to the addition/subtraction circuit 9.
connected to.

The addition/subtraction circuit 9 has a comparison judgment means (D) and an open phase detection means (D).
D) is connected to a comparison/judgment circuit 13 corresponding to and.

A backlash setting dial 14 corresponding to a model signal setting means (T) is connected to the central control device 2 from an attached comparison judgment circuit 13 to realize an emergency stop of the tool head 1.

Next, a second embodiment for detecting phase loss in the speed encoder 6 will be described with reference to FIG.

The position encoder 5 is connected to a position decoder 10, which has forward and reverse signal lines FS and A.
The 52 wires are connected to an addition/subtraction circuit 9 corresponding to addition/subtraction calculation means (AD).

The speed encoder 6 is similarly connected to a speed decoder 8, which has forward and reverse signal lines FS and A.
It is connected to the OR circuit 11 by 32 wires. The circuits downstream from this have exactly the same configuration as the first embodiment, so their explanation will be omitted.

Next, the operation of the configuration of the first embodiment will be described.

In response to a command from the central controller 2, the servo motor 3 rotates the feed shaft 4 in an arbitrary direction to move the tool head 1 to a specified position.

The position encoder 5 and the speed encoder 6 receive a rotation angle from the rotation of the servo motor 3 and the feed shaft 4, and output signal pulses proportional to the rotation angle. Here, the position encoder 5 does not generate an input error due to the rotational torque torsion input by the no-load portion of the feed shaft 4 on the downstream side that drives the tool head 1. Since both encoders 5 and 6 output two-phase pulse signals with a phase difference of 90 degrees, by detecting the phase rotation direction of the two phases, the rotation direction of the feed shaft 4, that is, the movement of the tool head 1. It can be determined whether the direction is forward direction F← or reverse direction→A.

This direction judgment is performed by the position decoder 10 and speed decoder 9 in the next stage, respectively, and when the direction is determined, they are output from separate output terminals to the respective next stage circuits as a forward direction output signal or a reverse direction output signal. be done.

The current position of the tool head 1 is detected by simply adding or subtracting the number of pulses of the position encoder 5 outputted via the position decoder 10 when moving from the starting point, and the speed of the tool head 1 during movement is , while the tool head 1 is moving, is detected by simply counting the number of pulses from the speed encoder 6 outputted via the speed decoder 8 within a unit time. However, in this embodiment, it is assumed that the number of pulses output from the speed encoder 6 has a ratio of 5:2 to that of the position encoder 5 for the sake of explanation. Now, to explain with reference to FIG. Considering that there are pulses, it is considered that the resolution corresponds to 2 pulses when converted by the position encoder 5.

Signal pulses output from the speed decoder 8 in response to the movement of the tool head 1 are input to an addition/subtraction circuit 9 and counted in real time in each forward direction or reverse direction.

On the other hand, at the same time, the position decoder 10 also outputs pulse signals in the forward direction or in the reverse direction, respectively, in accordance with the movement of the tool head 1, and input them to the OR circuit 11.

Regardless of the polarity of the forward or reverse signal pulse, the OR circuit 11 is in an on state as long as there is any input, so it directly converts the input signal into an output signal and outputs it. Input to reset circuit 12. Then, according to the movement of the tool head 1, the speed decoder 8 outputs the output and inputs it into the addition/subtraction circuit 9, respectively.
Alternatively, the N signal pulses counted in each reverse direction are reset in real time.

Here, if an open phase occurs in the output signal of the position encoder 5, a disconnection, poor contact, etc. occurs in the circuits of the position encoder 5 and position decoder 10, or a mechanical defect occurs, the reset operation may be instantaneous. If both are interrupted, the S signal pulses counted by the addition/subtraction circuit 9 are integrated without being reset. This integrated value φ is sent to the next comparison/judgment circuit 13.

The comparison judgment circuit 13 has a backlash setting dial 14.
In this embodiment, assuming that the number of signal pulses output from the speed encoder 6 is five in the range of "play" due to backlash existing in the mechanical system, the dial 14 is set as p=s. This set value p is obtained from (resolution of speed encoder/resolution of position encoder) + amount of backlash, and in this example, the ratio of resolutions is 5/2 = 2.5 amount of backlash = 5. The value is determined to be 8.

The integrated value φ input to the comparison/judgment circuit 13 is the dial 1
In step 4, p=8 is compared with the set p, and if -8≦φ≦+8, it is judged as ``normal state'', or -9
〉φ Mana is φ〉+9, it is determined to be an ``abnormal state''.

°If it is determined that the state is “normal”, the comparison judgment circuit 1
3 sends an 'OK' signal to the central controller 2, which causes the tool head 1 to continue moving according to the program.

On the other hand, if it is determined that there is an “abnormal state”, “NO”
A signal is output to yield, decelerate, or stop the movement of the rad 1 to the tool according to a preset program.

Next, the operation of the configuration of the second embodiment for detecting phase loss in the speed encoder 6 will be explained with reference to FIG. 4, but the basic operation of each device and circuit is exactly the same as in the first embodiment. Description is omitted.

As in the first embodiment, the servo motor 3 rotates the feed shaft 4 in an arbitrary direction in response to a command from the central controller 2, and moves the tool head 1 to a specified position.

Pulse signals output from the position encoder 5 via the position decoder 10 in response to the movement of the tool head 1 are input to the addition/subtraction circuit 9 and counted in real time in each forward direction or reverse direction.

On the other hand, at the same time, signal pulses in the forward direction or in the reverse direction are outputted from the speed encoder 6 via the speed decoder 8 in response to the movement of the tool head 1, respectively, and input into the OR circuit 11.

The OR circuit 11 converts the input signal into an output signal, outputs it, and inputs it to the reset circuit 12 as long as there is an input of either a forward direction or a reverse direction signal pulse. Then, according to the movement of the tool head 1, it is outputted from the position decoder 10 and inputted to the addition/subtraction circuit 9.
To reset signal pulses that are being counted in each forward direction or reverse direction in real time.

Here, if an open phase occurs in the output signal of the speed encoder 6, or a defect such as a disconnection or poor contact occurs in the circuits of the speed encoder 6 and speed decoder 8, the above reset operation will be interrupted even momentarily. If so, the signal pulses being counted by the addition/subtraction circuit 9 are integrated without being reset.

The integrated value φ is sent to the next comparison/judgment circuit 13.

Here, as mentioned above, the number of pulses output from the speed encoder 6 has a ratio of 5:2 to that of the position encoder 5 to increase the resolution, so the backlash setting dial 14 of the comparison judgment circuit 13 is In one embodiment, p=g.

In contrast to the previous setting, p=3. This set value p is (position encoder resolution/velocity encoder resolution)
In this example, since the resolution ratio is 0.4 and the backlash amount is 2, the value 3 is obtained.

Then, the integrated value φ is input to this comparison/determination circuit 13, and the p
A comparison operation is performed, and if -2≦φ≦+2, it is determined to be a "normal state".

On the other hand, if −3〉φ or φ〉+3,
'°Judging from abnormal abnormal conditions.

Thereafter, as in the first embodiment, if the state is "normal", the comparison circuit judgment 14 sends an "OK" signal to the central controller 2, or if the state is "abnormal" , °"NO" signal is output.

As explained in detail above, -i-wise, the signal pulses output from the encoder for position detection and the encoder for speed detection provided in such a servo mechanism are checked against each other. By simply adding a small amount of logic and arithmetic circuits, you can detect encoder phase loss and safely and accurately control the tool head without requiring any special equipment. It became possible to control the

(Effects of the Invention) As explained in the above embodiments, the encoder phase loss detection device according to the present invention uses conventionally employed technology to process signal pulses output from the encoder without complex shaping. Therefore, line drivers and associated signal lines, etc. are not required, and signal processing by an EX-OR circuit is also not required, and the accompanying filter circuit and time constant circuit are not required. First, it has the effect of eliminating the negative effects of noise and eliminating the need for hardware circuitry without compromising responsiveness.

Furthermore, in addition to detecting disconnections as before, this device constantly checks for defects in all feedback systems, from encoder defects, mechanical defects, and wiring cable defects to the decoder circuit, making it the most reliable device. Therefore, the conventional technology that only detects phase loss due to wire breakage is no longer necessary, and apparent phase loss due to backlash in the mechanical system can be clearly distinguished from phase loss due to abnormality. This has the effect of making it possible to detect all types of phase loss, including disconnection (for example, a deviation of about one tooth in a gear).9 The above effects are also caused by the tool head, It also prevents and eliminates unexpected movement or runaway of the worktable, further improving operator safety and at the same time preventing expensive machinery from being damaged or destroyed.
From the results, the tool head or work table can be moved up to the structurally and functionally allowable limits, i.e., up to the limit switch at both ends in position, and up to the maximum speed limit in terms of speed. Alternatively, it is possible to move and position the work table, improving production efficiency, and also making it clear whether the tool head or work table is inoperable due to an open phase, which improves the dimensional accuracy of workpiece processing. It has also become possible to improve the

In addition, in the first embodiment and the second embodiment, the servo motor 3
The amount of bala crash of the transmission system including the feed shaft 4 is known, and the set value p is determined from this amount of bala crash and the resolution ratio of both encoders 5.6. However, when the amount of balaclash is unknown, a configuration is added in which the value of the amount of balaclash can be determined in advance by subtracting the above-mentioned resolution ratio from the maximum value of the value accumulated in the adder/subtractor 9 without providing the set value p. You can leave it there.

[Brief explanation of the drawing]

1 and 2 are basic functional block diagrams of the encoder phase loss detection device, FIG. 3 is a functional block diagram of the first embodiment, and FIG. 4 is a functional block diagram of the second embodiment. 5.Position encoder 6.Speed encoder 8.Speed decoder 9.Addition/subtraction circuit 10.Position decoder 1
1. OR circuit 12. Reset circuit 13. Comparison judgment circuit 14. Backlash setting dial Applicant: Yamazaki Mazatuku Co., Ltd. Representative Teruyuki Yamazaki O. tncoo (t) Gu-H-

Claims (1)

[Scope of Claims] Position detecting means for outputting a signal corresponding to the moving distance of the moving body positioned by the servo driving means; A closed-loop position control servo system for a moving body, comprising: speed detection means for outputting a signal; direction determination means for determining each of the output signals from both of the detection means into a forward direction output signal or a reverse direction output signal, respectively; and addition/subtraction calculation means for adding or subtracting, respectively, a forward direction output signal or a reverse direction output signal outputted from said one detection means via said direction determination means, and addition/subtraction processing means for respectively adding or subtracting a forward direction output signal or a backward direction output signal output from said one detection means via said direction determination means. an OR operation means for performing an OR operation on the forward direction output signal and the reverse direction output signal outputted through the discrimination means; and a reset means for resetting the addition/subtraction operation means by the output signal from the OR operation means; , a comparison judgment means for comparing and judging the output signal of the addition/subtraction calculation means with a preset model signal; and as a result of the comparison judgment by the comparison judgment means, the output signal from the other one of the detection means is out of phase. An encoder open phase detection device comprising: an open phase detection means for detecting the presence of an open phase; and an encoder open phase detection device.