JPS6317575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of a moving object, and particularly relates to a method for detecting the position of a moving object, and in particular, a method for detecting the position of a moving object, which detects whether a reciprocating moving object such as a tool of a machine tool or industrial machine is located within a predetermined area. Related to a method for detecting the position of an object.

Generally, in machine tools and industrial machinery, it is extremely important to accurately detect the position of the tool, etc., because the feed rate of the tool, etc. is controlled according to the relative position of the workpiece and the tool, that is, the progress of machining. be. Therefore, conventionally, for example, as shown in FIG.
for processing the workpiece 12 fixed thereon,
A slide base 14 that is fixedly arranged, a slide table 18 that moves back and forth on the slide base 14 and supports a spindle 16, and a feed nut 20 fixed to the lower surface of the slide table 18 is screwed together. a DC motor 24 that moves the slide table 18 forward or backward by rotating a feed shaft 22;
a DC motor drive circuit 26 that controls the rotational direction and rotational speed of the spindle 16; a speed switching setting circuit 28 that outputs an appropriate feed speed setting value according to the forward position of the spindle 16 to the DC motor drive circuit 26; In a machine tool equipped with a machine sequence circuit 30 that controls a DC motor drive circuit 26, a dog 32 is disposed at a predetermined position on the side surface of the slide table 18, and a dog 32 is provided at a predetermined location on the side surface of the slide table 18.
A mechanical limit switch 34 that is turned on and off by the dog 32 is disposed at a predetermined position of 4, and when the limit switch 34 is turned on and off by the dog 32, the slide table 18, that is, the spindle 16 reaches a predetermined position. The DC motor drive circuit 2 is detected via the mechanical sequence circuit 30.
6 to control the feeding state of the slide table 18. In the figure, 35 is a bearing, 36 is a stopper fixed to the front end surface of the slide table 18, 37 is a dead stopper fixed to the inner wall surface of the slide base 14,
CR1 and CR2 are forward feed switching contacts for switching the rotation direction of the DC motor 24, and LS1 to LS4 are
This is a speed switching contact for switching the feed speed according to the machining situation.

In addition, when controlling the feed rate by setting multiple predetermined positions and changing the speed between each predetermined position in a machine tool such as the one described above, it is necessary to control the feed rate when the slide table as a moving object reaches the predetermined position. It is necessary to not only detect, but also to detect which predetermined positions the slide table is located between.
For this reason, in the past, a point dog and a self-holding circuit were used to turn on the limit switch 34 for a very short period of time, and the position detection signal output from the limit switch was held while the slide table moved between predetermined positions. However, since this method requires a self-holding circuit to hold the signal, there are problems in that the relay sequence becomes complicated and the cost increases. Also, two point dogs are arranged so as to correspond to both ends of a predetermined position, and one point dog turns on the limit switch and the other point dog turns off the limit switch. Similar to the above, there were problems in that the relay sequence became complicated and the cost increased. Furthermore, long dogs with corresponding lengths between predetermined positions are used to turn on the limit switch while the contact of the limit switch is in contact with the long dogs, but if used for a long period of time, the long dogs There was a problem that the rigidity decreased.

Furthermore, since each of the above methods uses a limit switch and a dog in combination, the relative positional relationship between the limit switch and the dog tends to deteriorate over time, and when the positional relationship breaks down, the positional relationship between the dog and the limit switch is adjusted. The problem is that it is difficult. Furthermore, when changing the distance between predetermined positions, there is a problem in that the positional relationship of the dog and limit switch must be changed.

Furthermore, limit switches have weak mechanical strength, and are not sufficiently protected against factory atmospheres such as oil, water, and dust, so they tend to malfunction due to chips, dust, cooling water, etc., and lack reliability. There's a problem. Furthermore, there are few problems with single-function machines that process a single workpiece using a single spindle, but in recent years, there has been a demand for multiple processes on a single or multiple workpieces. In the case of a general-purpose machine for this purpose, the positions of the dog and limit switch must be changed every time the workpiece or spindle is replaced, resulting in a lack of versatility.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting the position of a moving object that eliminates the above-mentioned problems by not using a limit switch or a dog.

In order to achieve the above object, the present invention has a configuration in which a reference pulse number is determined in correspondence with the origin position of a moving object that makes reciprocating motion, and a plurality of predetermined positions are determined within the movement range of the moving object to determine the origin position. A set number of pulses based on the reference pulse number is stored in a rewritable memory in correspondence with the distance from the reference pulse number to each predetermined position, and the moving direction of the moving object can be determined and one pulse corresponds to the movement. A pulse signal indicating a unit movement amount of the object is output, and the number of pulses of the pulse signal is added or subtracted from the reference pulse number according to the moving direction of the moving object to obtain the count number of the pulse signal, and the set number of pulses is determined. outputs a position detection signal when each of the count values match the count value, and continues outputting the position detection signal when the count value is between the reference pulse number and the set pulse number. A combination of these position detection signals is used to detect between which of the plurality of predetermined positions the moving object is located.

According to the above configuration of the present invention, a pulse signal is output in accordance with the movement of the moving object, and a position detection signal is output when the count number of pulses of the pulse signal matches the set number of pulses. The detection signal allows it to be detected that the moving object has reached a predetermined position. In addition, since each position detection signal continues to be output when the count number is between the reference pulse number and each set pulse number, the combination of these position signals determines where the moving object is at the predetermined position. It is possible to detect the location.

Embodiments of the present invention will be described in detail below with reference to the drawings. In this embodiment, the present invention is applied to the conventional machine tool shown in FIG. 1 to control the feed rate of a slide table.

As shown in FIG. 2, this embodiment detects the amount of rotation of the feed shaft 22 corresponding to the amount of movement of the slide table 18 from a gear coupling 49 instead of the conventional dog, limit switch, and forward feed switching contact. The rotary encoder 50 outputs a pulse signal, and a limit detection circuit 52 detects the feed position of the slide table 18 according to the output of the rotary encoder 50 and outputs the detected position to the mechanical sequence circuit 30. The rotary encoder 50 outputs one pulse for each unit movement of the slide table and is connected to a limit detection circuit 52, which in turn is connected to the mechanical sequence circuit 30. The machine sequence circuit 30 is connected to the speed switching setting circuit 28 and outputs a speed switching command to the speed switching setting circuit 28 according to the combination of limit signals as position detection signals, and also outputs a speed switching command to the DC motor drive circuit 26 as in the conventional case. It is connected to output forward/backward commands to the DC motor drive circuit 26. This limit signal corresponds to the on/off state of a conventional speed switching contact. The other points are the same as those of the conventional example shown in FIG. 1, so the explanation will be omitted.

The rotary encoder 50 is composed of a pair of photoelectric elements disposed around the gear of the gear coupling 49 of the DC motor 24 with a phase difference of 90°, for example, and rotates in the direction of rotation of the feed shaft 22, i.e. , two pulse signals as shown in FIG. 3 are outputted to the limit detection circuit 52, and have different phase differences depending on the direction in which the slide table 18 is fed. Therefore, the moving direction of the slide table can be determined from this pulse signal.

The limit detection circuit 52 includes an encoder input circuit 54 to which the output of the rotary encoder 50 is input, an input circuit 56 to which the operating command of the output of the mechanical sequence circuit 30 is input, an output circuit 58, and a display circuit 60. and a programmable peripheral interface (hereinafter referred to as PPI) 62
and a central processing unit (hereinafter referred to as CPU) 64
, read-only memory (hereinafter referred to as ROM) 66, and random access memory (hereinafter referred to as ROM) 66
(referred to as RAM) 68, and a bus 70 connecting these. This limit detection circuit 52
The reference pulse number corresponding to the origin position of the slide table 18 is stored in advance in the ROM 66 inside. The RAM 68 also stores a plurality of predetermined positions P defined within the movement range of the slide table 18.
Setting pulse number PUL1 corresponding to 1 to P4
PUL4 is stored in advance. These set pulse numbers PUL1 to PUL4 are obtained by converting the distance from the origin position to each predetermined position P1 to P4 into the number of pulses of the pulse signal output from the rotary encoder, respectively.
It is determined by adding or subtracting the converted number of pulses to the reference number of pulses. For example, if the reference pulse number is 0, the set pulse number PUL1
~PUL4 matches the number of pulses of the pulse signal output from the rotary encoder while the slide table moves from the origin position to each of the predetermined positions P1 to P4. These set pulse numbers PUL1~
PUL4 is written and stored by a separately prepared program module.

Next, the operation of this embodiment will be explained with reference to FIGS. 4 to 6. First, the slide table 18 is
As shown in FIG. 4, fast forwarding is performed from predetermined positions P1 to P2, first slow transport is performed to predetermined positions P2 to P3, second slow transport is performed from predetermined position P3 to origin position 0, and then from origin position 0 to a predetermined position. It is assumed that feed speed control is performed to quickly return to P1. In this embodiment, the second pulse number t ₁ corresponding to the minute stroke T ₁ with respect to the predetermined position P 1 is stored in advance in the ROM. This number of pulses t ₁ is used to detect the starting point of feed rate control.

The DC motor 24 rotates the feed shaft 22 via a gear coupling 49 to advance and retreat the slide table 18 to which the feed nut 20 is fixed. When the feed shaft 22 is rotated by the DC motor 24, since the rotary encoder 50 is coupled to the gear coupling 49, the rotary encoder 50 outputs two signals having different phase differences depending on the direction of rotation. , a pulse signal as shown in FIG. 3 is output, and this is input to the encoder input circuit 54 of the limit detection circuit 52.

The limit detection circuit 52 receives an in-operation command signal from the machine sequence circuit 30 through an input circuit 56, and when it is not in operation, it is in a rest state as shown in FIG. When the mechanical sequence circuit 30 output is in operation, the moving direction of the slide table is determined by two pulse signals with a 90° phase difference from the rotary encoder 50, and the forward direction (encoder forward rotation), Distinguish whether the direction is backward (encoder reversal).
When the encoder is in the normal rotation state and the slide table 18 is in the forward state, the abnormal output (described later) of the limit detection circuit 52 is cleared, and the number of pulses of the pulse signal output from the rotary encoder 50 is The pulse signal is added to the reference pulse number and counted to obtain the pulse signal count number. On the other hand, if the encoder is outputting a reverse rotation signal and the slide table 18 is in the backward state, the encoder output as the slide table 18 moves backward is calculated based on the number of pulse signals counted up to that time. Subtract and count the number of output pulses. Then, the count number of the pulse signal and the
Predetermined positions P1 to P4 stored in RAM 68
The CPU 64 compares and matches the set pulse numbers PUL1 to PUL4 corresponding to , and if they match, sends limit signals LS ₁ to _{LS 4} as position detection signals.
It changes the on/off state of and outputs it to the output circuit 58 via the PPI 62.

Specifically, the limit signal output from the limit detection circuit 52 is output according to the flowchart shown in FIG. That is, from the rotary encoder 50 output to the encoder input circuit 54, PPI
The count number Pi of the pulse signal inputted to the CPU 64 via 62 is at a predetermined position P1
When the set pulse number PUL1 corresponding to is reached, the limit signal LS1 is turned on and the number of pulses of the pulse signal is counted by the second pulse number t ₁ corresponding to the predetermined stroke T ₁ preset in the RAM 68. The limit signal LS1 is kept on until the limit signal LS1 is turned on. This predetermined stroke _T1 has a minute length, and since the limit signal LS1 is in the ON state, it can be confirmed that the slide table is located at the start position of feed rate control.

When the slide table is moved and the count number Pi of the pulse signal matches the set number of pulses PUL2, the limit signal LS2 is turned on and the number of pulses of the pulse signal output as the table moves becomes the set number of pulses. The ON state of the limit signal LS2 is maintained until the same number as PUL2 is counted. That is, if there is no error between the table position and the pulse signal, the limit signal LS2 is turned on during the stroke _T2 shown in FIG. Similarly, when the count number Pi matches the set pulse number PUL3, the limit signal LS3 is turned on, and the on state of the limit signal LS3 remains until the number of pulses of the pulse signal is counted as the set pulse number PUL3. Retained.
That is, if no error has occurred, the limit signal LS3 is kept on during the stroke _T3 shown in FIG. Also, if the count number Pi matches the set pulse number PUL4, the limit signal
LS4 is turned on and the on state of the limit signal is maintained until the number of pulses of the pulse signal is counted to be the same as the set number of pulses PUL4. That is, if no error has occurred, the limit signal LS4 remains on during the stroke _T4 shown in FIG.

Therefore, depending on the combination of the on/off states of the limit signals LS1 to LS4, it is possible to detect which of the predetermined positions the slide table is located.
Based on this detection result, the feed speed of the slide table can be controlled. For example, limit signal LS1 is off, limit signal LS2 is on,
When limit signal LS3 and limit signal LS4 are off, it is detected that the slide table is located between predetermined position P2 and predetermined position P3, and at this time, the slide table is controlled at the first slow feed speed. .

Further, in this embodiment, the error between the position of the slide table and the count number is corrected as follows. As the machining of the workpiece 12 progresses and the stopper 36 on the slide table 18 side reaches the origin position where it comes into contact with the dead stopper 37 fixed to the end surface of the slide base 14, the DC motor 24
Regardless of the rotational torque of slide table 1
8 becomes impossible to move forward, and rotary encoder 5
From 0, no pulse output can be obtained. Therefore,
The state in which the output of the rotary encoder 50 disappears for a certain period of time is determined to be the origin position (FIG. 5), and the counter is reset. At this time, before performing the reset, it is determined whether the count number of the pulse signal at the time of returning to the origin is around the reference pulse number (for example, 0). That is, when the count number is greater than or equal to the lower limit discrimination value and less than or equal to the upper limit discrimination value, it is determined that the operation has been performed normally, the count number is reset to the reference pulse number, and fast reversal is performed to proceed to the next processing. On the other hand, if the count number is less than the lower limit discrimination value or exceeds the upper limit discrimination value, it is considered that the count number of the counter has deviated from the actual position of the slide table 18 due to an abnormality in either the mechanical system or the electrical system. The abnormal state is displayed by the display circuit 60, and an abnormal output is output to the machine sequence circuit 30 to stop the machining.

The limit signal (control switching signal point) can be easily changed by modifying the data (corresponding to the distance from the origin position) in the RAM 68 in the limit detection circuit 52 using a separately prepared program module. It is done.

In this embodiment, instead of immediately determining the moment when the stopper 36 on the slide table 18 side contacts the dead stopper 37 as the origin position, the stopper 36 is held at a substantially constant position relative to the dead stopper 37 by the rotational torque of the DC motor 24. Since the point that is continuously pressed by force for a predetermined period of time is determined to be the origin position, there are few errors due to backlash, return, etc.

In this embodiment, the origin position is the machining end position at the most advanced position of the slide table, but the origin position is not limited to this, and may also be the return completion position at the rearmost position of the slide table. It is also possible to set it as an intermediate position or an intermediate processing position where a certain processing is completed.

In the above embodiment, the rotary encoder 50 outputs two pulse signals having a phase difference of 90 degrees, but the type of output signal of the rotary encoder is not limited to this.
When using a rotary encoder that outputs only a single pulse train as an output signal, forward and backward signals may also be input as command information from the machine sequence circuit 30 to determine direction, or The rotary encoder itself rotates forward,
In the case of reverse rotation, different pulse signals may be generated separately. In this case, the operation of the limit detection circuit is further simplified.

Further, in the above embodiment, the limit signal is incorporated into a mechanical sequence circuit consisting of a relay sequence circuit, but it is of course possible to incorporate it into a sequencer, which has become increasingly popular in recent years.

In the above embodiments, the present invention was applied to a machine tool in which the slide table was controlled to be fed by a DC motor, but the scope of application of the present invention is not limited to this. The feed is controlled by the cylinder,
It is also applicable to general machine tools in which the feed rate is changed by changing the flow rate of the oil or air.

As explained above, according to the present invention, since a limit switch and a dog are not used, malfunctions due to chips etc. do not occur, and since the set number of pulses is stored in RAM, that is, a rewritable memory, the dog without changing the position of
The effect is that the setting position can be easily changed by rewriting the memory contents of the RAM.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of a feed control device for a machine tool using a conventional mechanical limit switch, and FIG. 2 shows an embodiment of the method for detecting the position of a moving object according to the present invention. A block diagram showing the configuration of the adopted machine tool feed control device,
FIG. 3 is a diagram showing the output waveform of the rotary encoder in the embodiment, FIG. 4 is a diagram showing the feed speed control state of the slide table in the embodiment, and FIGS. 5 and 6 are It is a flow chart showing the operation of the limit detection circuit in the same embodiment. 12... Workpiece, 14... Slide base, 16
...Spindle, 18...Slide table, 20...
Feed nut, 22...Feed shaft, 24...DC motor,
26... DC motor drive circuit, 28... Speed switching setting circuit, 30... Mechanical sequence circuit, 36... Stopper, 37... Dead stopper, 50... Rotary encoder, 52... Limit detection circuit, 54... Encoder input circuit, 56... Input circuit, 58...Output circuit, 60...Display circuit, 62...PPI, 64...CPU,
66...ROM, 68...RAM, 70...bus.

Claims (1)

[Claims] 1. A reference pulse number is determined in correspondence with the origin position of a moving object that reciprocates, and a plurality of predetermined positions are determined within the movement range of the moving object and are made to correspond to the distances from the origin position to each predetermined position. A set number of pulses based on the reference number of pulses is stored in a rewritable memory, and a pulse signal is output in which the moving direction of the moving object can be determined and one pulse indicates a unit movement amount of the moving object. , the number of pulses of the pulse signal is added or subtracted from the reference number of pulses according to the moving direction of the moving object to obtain the count number of the pulse signal, and when each of the set pulse numbers and the count number match, the position is determined. outputting each of the detection signals and continuing to output each of the position detection signals when the count number is between the reference pulse number and each of the set pulse numbers, and by the combination of these position detection signals. A moving object position detection method for detecting which of the plurality of predetermined positions the moving object is located between.