JP2002062937A - Abnormality detecting method and abnormality detecting device for position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the abnormality detecting precision of a position detector, in a serve control device for detecting a control shaft by a servomotor and detecting the position by an absolute position detector or the like, to quickly stop the control shaft. SOLUTION: In this abnormality detecting method for position detector, the present position data in stopping is stored in the rotation start of the servo motor, the present position is read when the rotation reaches an intended speed instruction value, and it is decided to be an abnormality when the difference between the two present position data is smaller than an allowable position change lower limit value. The present value data is read and compared with the previous position data in the stopping of the servomotor, and it is decided to be an abnormality when the position change is out of the allowable position change. The speed change and acceleration change are continuously calculated during the rotation of the servomotor, and it is decided to be an abnormality when they are out of the upper and lower limits of the respective allowable change. When the position detector is abnormal, the control shaft is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a servomotor whose rotation is controlled to a given target position.
The present invention relates to an abnormality detection device for a position detector including a mechanism for stopping a servomotor for driving a control axis when a value of a position detector for detecting a movement position of a servomotor becomes abnormal.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. Fig. 8
A solid line 800 indicates a temporal change in the target speed of the movable body whose position is controlled, and a solid line 850 indicates a temporal change of the target position of the movable body whose position is controlled. This is the most typical example when the control axis is driven by a servo motor, and it accelerates at a constant rate from a stopped state, moves at a constant rate for a certain time when it reaches a certain speed, and then at a certain rate. An example in which the vehicle decelerates and stops is shown. When the servomotor is feedback-controlled based on the speed deviation and the position deviation when the target speed and the target position are given, the actual rotation speed and the rotation angle position of the servomotor follow the target speed and the target position. Is controlled as follows. But,
The actual rotation speed of the servo motor indicated by the broken line 802 in FIG. 8 and the actual rotation angle position indicated by the broken line 852 do not match the target speed and the target position, and there are speed deviations and position deviations.
Therefore, even if the target speed command and the target position command become zero, the speed deviation and the position deviation remain. For example, as is clear at time t2, the actual rotational speed is slightly delayed from the target speed command and the target position command. And the rotation angle position becomes zero. The time at which the actual rotation speed or rotation angle position becomes zero is t
3.

[0003] In such a servo motor control device, if the actual rotation angle position of the servo motor is greatly deviated from the target position for some reason, the servo motor is stopped. Are added. In this prior art, an upper limit position deviation allowable value (for example, Δθ (804) in FIG. 8) is provided, and a means for comparing the current position deviation with the upper limit position deviation allowable value is provided. Means for outputting a warning that the position deviation is excessive when it is determined that the value exceeds the upper limit position deviation allowable value, and means for stopping the servomotor.

[0004]

When such a servo system is used for feeding a tool table of a machine tool, the movable part must be positioned at an upper limit as much as possible in order to detect interference with other tools at an early stage. It is better to set a small deviation tolerance. However, since the position deviation greatly changes due to the fluctuation of the machining conditions of the machine or the state of the machine, the upper limit position deviation allowable value has to be set to a value considerably larger than the position deviation obtained from the calculation.

[0005]

Means for Solving the Problems In order to solve the above problems, a first invention of the present application is to drive a control axis by a servomotor and to store position information for controlling the control axis by a movement position of the servomotor. In the abnormality detection method of the position detector which is obtained from the absolute position detector for detecting the absolute position detector based on the position information and detects the abnormality of the absolute position detector, when the target speed command value and the actual speed value are both zero, First storage means for storing the current position data obtained from the absolute position detector; and operating the control axis from the current position stored by the first storage means to set the target speed of the servo motor to the position check speed command value. A second storage means for storing the current position data obtained from the absolute position detector when the first and second storage means Calculating means for obtaining a difference between the two stored current position data, comparing means for comparing the difference obtained by the calculating means with a predetermined allowable position change amount, and a difference obtained by the comparing means. Means for determining that the absolute position detector is abnormal when it is determined that the absolute position change amount is smaller than the allowable position change amount, and stopping the servomotor for controlling the control axis. It is.

According to a second aspect of the present invention, a control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor. In the abnormality detection method of the position detector, wherein the abnormality of the absolute position detector is detected based on the leverage position information, means for reading current position data obtained from the absolute position detector when the target speed command value is zero. Means for reading out the previous current position data obtained from the absolute position detector one control cycle before from the storage device, and calculating means for obtaining a position change amount from a difference between the current position data and the previous current position data. Comparing means for comparing the difference obtained by the calculating means with a preset allowable position change amount; When it is determined that the obtained difference is within the range of the allowable position change amount, first storage means for storing the current position data as the previous current position data, and the difference obtained by the comparison means is the allowable position change amount. When it is determined to be out of the range, it is determined that the absolute position detector is abnormal,
Means for stopping the servomotor for driving the control axis, the abnormality detection device for an absolute position detector.

According to a third aspect of the present invention, a control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor. In the abnormality detection method of the position detector configured to detect abnormality of the absolute position detector based on leverage position information, a means for reading current position data obtained from the absolute position detector when the servo motor is rotating, Means for reading out the previous current position data obtained from the absolute position detector one control cycle before from the storage device, and calculating means for obtaining current speed data from the difference between these current position data and the previous current position data; Means for reading out the previous speed data obtained one control cycle before from the storage device; Calculating means for calculating the speed change amount from the difference between the previous speed data, and comparing means for comparing the speed change obtained by the calculating means with a predetermined allowable speed change amount upper limit value and an allowable speed change amount lower limit value; Means for determining that the absolute position detector is abnormal when the speed change amount is out of the range of the allowable speed change amount by this comparing means, and stopping the control axis driving servomotor. Abnormality detector of the absolute position detector.

According to a fourth aspect of the present invention, a control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor. In the abnormality detection method for the position detector, wherein the abnormality of the absolute position detector is detected based on the lever position information, a means for reading the current speed data when the servo motor is rotating is provided. Means for reading out the previously obtained current speed data from the storage device; calculating means for obtaining current acceleration data from a difference between the current speed data and the previous current speed data; Means for reading out the acceleration data from the storage device, and calculating the amount of change in acceleration from the difference between the current acceleration data and the previous acceleration data. A stage, and comparing means for comparing the preset allowable acceleration change amount upper limit value and the permissible acceleration change amount lower limit value of the acceleration change amount obtained by the calculating means,
Means for determining that the absolute position detector is abnormal when the amount of change in acceleration is outside the range of the amount of change in allowable acceleration, and stopping the servomotor for driving the control shaft. Abnormality detector of the absolute position detector.

[0009]

According to the present invention, the current position data is stored when the target speed command value and the actual speed value are zero when the rotation of the servo motor is stopped and the rotation starts, and when the target speed command value is reached next, the current position data is stored. Also memorize the position, part 2
When the difference between the two current position data is smaller than the set permissible position change lower limit value, it is determined that the position detector is abnormal. Therefore, the difference between the two current position data is smaller than the permissible position change lower limit value. Sometimes it can be immediately judged that the position detector is abnormal.

According to the present invention, when the target speed command value of the servomotor is zero, the current value data of the position fed back from the position detector is read and compared with the stored previous position data, and the position change is performed. If the amount is not within the set allowable position change amount, it is determined that there is an abnormality in the position detector.If the position change amount is not within the allowable position change amount, it is immediately judged that the position detector is abnormal. it can.

According to the present invention, the speed change and the acceleration change are constantly calculated during the rotation of the servo motor, and the upper and lower limits of the allowable speed change and the upper and lower limits of the allowable acceleration change are not set. In this case, it is determined that the position detector is abnormal.If the speed change and acceleration change do not fall within the upper and lower limits of the allowable speed change and the upper and lower limits of the allowable acceleration change, the position It can be judged as abnormal.

[0012]

FIG. 1 is a schematic block diagram showing a configuration of a digital servo control device provided with an abnormality detection device for an absolute position detector used in a CNC according to the present invention. Reference numeral 100 denotes a numerical controller, which is a digital servo controller via a shared RAM 120.
Connected to 130. Multi-axis servo amplifiers 140 and 150 are connected to the digital servo controller 130, and servo motors 142 and 152 are connected from the servo amplifiers 140 and 150. In addition, the servo motors 142 and 152 have transmission mechanisms 146 and 1
For example, it is connected to a grindstone feed mechanism 148 and a table feed mechanism 158 of the grinding machine via 56.

The numerical control device denoted by reference numeral 100 has a main CPU.
And performs pulse distribution and system monitoring.
The digital servo control unit denoted by reference numeral 130 includes a CPU that performs servo control, and performs program processing, multi-axis position control, speed control, and current control of the present invention. The digital servo control unit 130 also includes a ROM for storing a program for executing the present invention and a RAM for temporarily storing operation data. Next, the servo amplifiers 140 and 150 output a three-phase AC current for controlling the inverters by the PWM signal output from the upper digital servo controller 130 to rotate the servo motors 142 and 152. Absolute position detectors 144 and 154 for detecting the movement positions of the servo motors 142 and 152 are attached to the rear of the servo motors. This is fed back to the control unit 130.

Next, as a first embodiment of the present invention,
A method of detecting an abnormality of the absolute position detector 144 in the servo system for controlling the wheel head feed will be described in detail with reference to conceptual diagrams and flowcharts of FIGS. First, a method of detecting an abnormality of the position detector when the servomotor 142 starts rotating from a stop will be described with reference to FIG.
Will be described with reference to a conceptual diagram of FIG. First, in step S300, the servo control CPU in the digital servo control unit 130 determines whether the target speed command value and the actual speed value of the servo motor 142 are zero or not. When it is determined that the target speed command value and the actual speed value are zero, the process proceeds to step S302, and at this time, that is, the current position data when the target speed command value and the actual speed value are zero, as shown in FIG. The position data FB0 is stored in the RAM. Next, in step S304, it is determined whether the servo motor 142 has reached the preset target speed command value. Step when the target speed command value is reached
Proceeding to S306, the current position data output from the position detector 144 at this time is stored in the RAM. The target speed command value is shown in Fig. 2-
Speed command value for position check along the speed command curve 200 of (1)
The current position data at the time of reaching the target speed command value is set as the position data FB1 in FIG.
It is. Next, in step S308, in step S302
The current position data FB0 when the target speed command value and the actual speed value stored in the RAM are zero, and RA
The difference from the current position data FB1 when the target speed command value V1 stored in M is reached is calculated. Next, in step S310, the difference between the current value data (FB0-FB1) is compared with a preset allowable position change amount. If the difference is large, the position detector is determined to be normal, and the rotation operation of the servomotor 142 is performed. To continue.
If the difference is small, the process proceeds to step S312, where an error in the position detector is displayed, and the machine is stopped in step S314.

Next, as a second embodiment of the present invention,
The method of detecting the position detector as abnormal when the position change amount is not within the set allowable position change amount when the target speed command value of the servo motor 142 is zero is described with reference to the state diagram of FIG. This will be described with reference to the flowchart of FIG. Fig. 4-
In (1), reference numeral P400 indicates an abnormal state in which the output of the position detector suddenly increases when the target speed command value of the servo motor 142 is maintained at zero, and P402 indicates the target speed of the servo motor 142. This shows an abnormal state in which the output of the position detector gradually changes when the speed command value is maintained at zero. First, in step S500 of FIG.
It is determined whether the target speed command value is zero or not zero. If it is not zero, it is determined that the servo motor 142 is rotating, and the rotating operation is continued. If the target speed command value is zero, the process proceeds to step S502, where the current position data is read. Next, in step S504, the position data detected in the previous sampling stored in the RAM is read. The routine shown in FIG. 5 is executed by the digital servo controller 1 at a control cycle of, for example, 1 ms.
Repeatedly executed by the servo control CPU in 30 and step S
In 506, the position change amount Δθn (or Δθm) between the current position data and the previous position data is calculated. In step S508, the upper limit value PU of the allowable position change amount set in advance and stored in the RAM is read. In step S510, the lower limit value PL of the allowable position change amount that is also set in advance and stored in the RAM is read. In step S512, it is determined whether the position change amount Δθn (or Δθm) is within the allowable position change amount (that is, PL <Δθn (or Δθm) <PU). Step if the position change amount is within the allowable position change amount
Proceeding to S514, the current position data is set in the previous position data storage RAM for use in the next calculation. If the position change amount is not within the allowable position change amount, the process proceeds to step S516, where a position detector abnormality is displayed, and the machine is stopped in the next step S518.

Next, as a third embodiment of the present invention,
A method of detecting the abnormality of the position detector during the rotation of the servomotor 142 based on the speed change amount will be described with reference to the state diagram of FIG. 4- (2) and the flowchart of FIG. The abnormalities in the change of the actual speed are indicated by reference numerals P410 and P412 in FIG. 4- (2). 4 (2) and (3) in FIG. 4 show actual velocity values and actual acceleration values corresponding to the sampling points tn-1, tn and tn + 1 at the current position in FIG. 1 (1). Next, a method of detecting an abnormality of the position detector based on a speed change amount will be described with reference to a flowchart of FIG. First, in step S600, the current position data is read. Next, in step S602, the position data detected in the previous sampling stored in the RAM is read. In step S604, the difference between the current position data and the previous position data is calculated to obtain the current speed data. Next, step S6
In step 06, the speed data calculated in the previous control cycle stored in the RAM is read. In step S608, the speed change amount ΔV, that is, the acceleration is calculated from the difference between the current speed data calculated in step 604 and the previous speed data.
Next, in step S610, the upper limit value VU of the allowable speed change amount set in advance and stored in the RAM is read. In step S612, the lower limit value VL of the allowable speed change amount, which is also set in advance and stored in the RAM, is read. In step S614, it is determined whether the current speed change amount ΔV obtained in step S608 is within the allowable speed change amount (that is, VL <ΔV <VU). If the current speed change is within the allowable speed change, the rotation operation of the servomotor 142 is continued. If the current speed change amount is not within the allowable speed change amount, the process proceeds to step S616, where a position detector abnormality is displayed, and the machine is stopped in the next step S618.

Next, as a fourth embodiment of the present invention,
A method for detecting an abnormality of the position detector during rotation of the servomotor 142 based on the amount of change in acceleration will be described with reference to the state diagram of FIG. 4- (3) and the flowchart of FIG. Abnormal changes in the actual acceleration are indicated by reference symbols P420, P422, and P in Fig. 4- (3).
424. Next, a method of detecting an abnormality of the position detector based on the amount of change in acceleration will be described with reference to the flowchart of FIG. First, in step S700, the current speed data is read. Next, in step S702, the speed data calculated in the previous control cycle stored in the RAM is read. In step S704, the difference between the current speed data and the previous speed data is calculated to obtain the current acceleration data. Next step
In S706, the acceleration data calculated in the previous control cycle stored in the RAM is read. In step S708,
The acceleration change amount Δα1 (or Δα2) is obtained from the difference between the current acceleration data calculated in step S704 and the previous acceleration data,
That is, the jerk is calculated. Next, in steps S710 to S714, the current position, speed, and acceleration data are set in the storage RAM as previous position, speed, and acceleration data for use in the next calculation. Next, in step S716, the upper limit value αU of the allowable acceleration change amount set in advance and stored in the RAM is read. In step S718, the lower limit value αL of the allowable acceleration change amount, which is also set in advance and stored in the RAM, is read. In step S720, step S70
The current acceleration change amount Δα1 (or Δα2) obtained in step 8 is within the allowable acceleration change amount (that is, αL <Δα1 (or Δα
2) It is determined whether <αU). If the current acceleration change amount is within the allowable acceleration change amount, the rotation operation of the servo motor 142 is continued. If the current acceleration change amount is not within the allowable acceleration change amount, the process proceeds to step S722,
The position detector abnormality is displayed, and the machine is stopped in the next step S724.

[0018]

Other Embodiments The present invention may be implemented by an absolute method or an incremental method as a detecting method, and may be implemented by an optical or magnetic detecting element. Further, the position detector is not limited to the servo motor direct connection type, but can be implemented with a linear scale attached to a movable body of a machine.

[0019]

According to the first invention of the present application, a case where no change is observed in the position output from the position detector within a short time when the rotation of the servomotor is started is detected as a position detector abnormality. Therefore, the machine can be stopped quickly. According to the second aspect of the present invention, since the position change is checked only when the servomotor is stopped, the upper limit position deviation allowable value can be set small. Can be stopped. According to the third and fourth inventions of the present application, since the change in speed and the change in acceleration are checked at the time of rotation of the servomotor, a slight change in position can be regarded as a large change. Since the speed change allowable value and the upper limit acceleration change allowable value can be set small, the position detector can quickly stop the machine when an abnormality occurs.

[0020]

[Brief description of the drawings]

FIG. 1 is a system block diagram according to a specific embodiment of the present invention.

FIG. 2 is a conceptual diagram of the present invention.

FIG. 3 is a flowchart according to a specific embodiment of the present invention.

FIG. 4 is a state diagram illustrating the concept of the present invention.

FIG. 5 is a flowchart according to a specific example of the present invention.

FIG. 6 is a flowchart according to a specific example of the present invention.

FIG. 7 is a flowchart according to a specific example of the present invention.

FIG. 8 is a conceptual diagram showing the concept of the prior art.

[Explanation of symbols]

 200 speed command value 202 actual speed 250 position command value 252 actual position 800 speed command value 802 actual speed 804 position deviation amount 850 position command value 852 actual position

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H269 AB01 BB12 BB14 EE01 JJ01 NN02 NN04 PP02 PP03 5H303 AA01 AA30 BB01 BB06 BB14 CC10 DD01 FF07 FF08 JJ02 JJ04 KK04

Claims (6)

[Claims] 1. A control axis is driven by a servo motor, and position information for controlling the control axis is obtained from an absolute position detector for detecting a movement position of the servo motor, and the absolute position detection is performed based on the position information. An abnormality detection method of a position detector configured to detect abnormality of a servomotor, wherein a current position data obtained from the absolute position detector is stored when a target speed command value and an actual speed value of the servomotor are both zero. 1 storage step; and operating the control axis from the current position stored in the first storage step, and when the target speed of the servomotor reaches a preset position check speed command value, the absolute position detector A second storage step of storing the obtained current position data; and a first and a second storage step. Calculating a difference between the two stored current position data, a comparing step of comparing the difference obtained in the calculating step with a preset allowable position change amount, and a difference obtained in the comparing step Determining that the absolute position detector is abnormal when it is determined that the absolute position change amount is smaller than the allowable position change amount, and stopping the servomotor for driving the control axis, and a method for detecting an abnormality of the absolute position detector. . 2. A control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor, and based on the position information, In the abnormality detection method of the position detector which detects the abnormality of the absolute position detector, a change is made from a difference between at least one of the position, speed, and acceleration stored one control cycle before and the corresponding data acquired this time. Calculating the amount; comparing the calculated amount of change with a corresponding preset tolerance; and an absolute position detector when the calculated amount of change exceeds the corresponding allowable value. Determining that there is an abnormality in the absolute position detector, and stopping the servomotor for driving the control axis. Normal detection method. 3. A control axis is driven by a servo motor, and position information for controlling the control axis is obtained from an absolute position detector for detecting a movement position of the servo motor, and the absolute position detector is based on the position information. A first storage means for storing current position data obtained from the absolute position detector when both the target speed command value and the actual speed value are zero; and The second storage for storing the current position data obtained from the absolute position detector when the control axis is operated from the current position stored by the first storage means and the target speed of the servomotor becomes the position check speed command value. Means for calculating a difference between the two current position data stored by the first and second storage means; A comparing means for comparing the difference obtained by the calculating means with a preset allowable position change amount; and when the difference obtained by the comparing means is determined to be smaller than the allowable position change amount, the absolute position detector Means for judging an abnormality and stopping the servomotor for driving the control axis, comprising: an abnormality detection device for an absolute position detector. 4. A control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor, and the absolute information is obtained based on the position information. In the position detector abnormality detection method for detecting an abnormality of the position detector, a means for reading the current position data obtained from the absolute position detector when the target speed command value is zero, and an absolute position before one control cycle Means for reading the previous current position data obtained from the detector from the storage device; calculating means for obtaining a position change amount from a difference between the current position data and the previous current position data; Comparing means for comparing the difference with a predetermined allowable position change amount; When it is determined that the current position data is within the range of the position change amount, it is determined that the difference obtained by the first storage unit that stores the current position data as the previous current position data is outside the range of the allowable position change amount. Means for judging that the absolute position detector is abnormal at the time, and stopping the servomotor for controlling the control axis, comprising: an abnormality detecting device for the absolute position detector. 5. A control axis is driven by a servo motor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servo motor, and the absolute information is obtained based on the position information. In the position detector abnormality detection method for detecting an abnormality of the position detector, means for reading the current position data obtained from the absolute position detector while the servo motor is rotating, and detecting the absolute position one control cycle before Means for reading the previous current position data obtained from the storage device from the storage device; calculating means for obtaining current speed data from a difference between the current position data and the previous current position data; Means for reading the previous speed data from the storage device, and a difference between the current speed data and the previous speed data. Calculating means for further calculating the speed change amount; comparing means for comparing the speed change amount obtained by the calculating means with a preset allowable speed change amount upper limit value and allowable speed change amount lower limit value; Means for determining that the absolute position detector is abnormal when the speed change amount is out of the range of the permissible speed change amount, and stopping the servomotor for controlling the control axis, comprising: Device abnormality detector. 6. A control axis is driven by a servomotor, and position information for controlling the control axis is periodically obtained from an absolute position detector for detecting a movement position of the servomotor, and the absolute information is obtained based on the position information. In the abnormality detection method of the position detector which detects the abnormality of the position detector, a means for reading the current speed data when the servo motor is rotating, and a method for reading the previous current speed data obtained one control cycle ago. Means for reading from the storage device; calculating means for obtaining current acceleration data from the difference between the current speed data and the previous current speed data; reading from the storage device the previous acceleration data obtained one control cycle earlier Means for calculating an acceleration change amount from a difference between the current acceleration data and the previous acceleration data; Comparing means for comparing the calculated acceleration change amount with a preset allowable acceleration change amount upper limit value and an allowable acceleration change amount lower limit value, and the comparison means determines that the acceleration change amount is outside the range of the allowable acceleration change amount. Means for determining that the absolute position detector is abnormal when determined, and for stopping the servomotor for controlling the control axis, comprising: an abnormality detecting device for an absolute position detector.