JPH0213325B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a position detection device for a moving object, and in particular, in a machine tool or the like, detects when the relative position between a workpiece and a tool has reached a predetermined position, and The present invention relates to a moving object position detection device suitable for accurately performing control switching. [Prior Art] Generally, in machine tools and industrial machines, 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, so the position of the tool, etc. must be accurately controlled. Detection is extremely important. An example of a conventional machine tool is shown in Fig. 1. Jig 1
0, a workpiece 12 is fixed. The machine tool for processing this includes a fixedly arranged slide base 14, a slide table 18 that supports a spindle 16 and moves back and forth on the slide base 14, and a feed nut fixed to the lower surface of the slide table 18. 20, a DC motor 24 that rotates the feed shaft 22 and moves the slide table 18 forward or backward, a DC motor drive circuit 26 that controls the rotational direction and speed of the DC motor 24, and a spindle. A speed switching setting circuit 28 that outputs an appropriate feed speed setting value according to the forward position of the motor 16 to the DC motor drive circuit 26, and a mechanical sequence circuit 30 that controls the DC motor drive circuit 26. At a predetermined location on the side of the slide table 18,
A dog 32 is provided, and a mechanical limit switch 34, which is turned on and off by the dog 32, is arranged at a predetermined location on the slide base 14. The limit switch 34 is turned on and off by the dog 32, and the slide table 18, that is, the spindle 1
6's forward position is detected. A signal from the limit switch 34 is sent to the DC motor drive circuit 20 via the mechanical sequence circuit 30, and is used to control the feeding state of the slide table 18. In addition, 35 is a bearing part, 36 is a stopper fixed to the front end surface of the slide table 18, and 37
is a dead stopper fixed to the inner wall surface of the slide base 14, and CR1 and CR2 are DC motors 2.
4 are forward/reverse switching contacts for switching the rotation direction, and l _s1 to l _s4 are speed switching contacts for switching the feed rate according to the machining situation. [Problems to be Solved by the Invention] This position detection device has a very simple structure, and includes mechanical limit switches 34 and dogs 32 in numbers approximately equal to the number of required signal outputs at positions required for control switching. The advantage is that all you need to do is set up the . However, mechanical 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. . Further, the relative positional relationship between the limit switch and the dog tends to deteriorate over time, making it difficult to adjust the dog. Furthermore, there are fewer problems with machine tools that process a single workpiece with a single spindle, but with modern machine tools that perform multiple processes on a single or multiple workpieces, The position of the dog and limit switch must be changed each time the workpiece or spindle is changed, resulting in a lack of versatility. These problems also apply when a proximity switch is used instead of a limit switch. In addition, modern numerically controlled machine tools use digital position detectors that digitally quantize variables and use them as increment values, but if a pulse counting error occurs for some reason,
There is a problem in that counting errors occur, and the repeated movement of the slide table 18 causes counting errors to accumulate, which tends to cause serious trouble. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a pulse generator that outputs a pulse signal that corresponds to a unit movement amount of a moving object and whose direction can be determined; a reference signal generator that outputs a reference signal when the area is reached; a reference point discriminator that sets a reference position at a specific position in the reference area; a counter that counts the number of pulses of the pulse signal; a data input device for setting a plurality of switch signal numbers corresponding to a plurality of positions within a position detectable range including a reference position and a forward end dead stopper position, and reference values corresponding to at least the reference position and a forward end dead stopper position; In a position detecting device for a moving body, which includes a memory that stores data set by an input device, and a processing device that calculates according to a predetermined control program and outputs a switch signal, the processing device converts a reference signal into one of the switch signals. and a reference signal output means that directly outputs the reference signal as a reference signal, and resets the counted value to the reference value when the difference between the counted value of the counter and the preset reference value is within a predetermined value at least at the reference position and the forward end dead stopper position. The present invention proposes a position detecting device for a moving object, which has a reset means for determining the position of a moving object, and a reference selection means for switching the operations of the reference signal output means and the reset means in accordance with a reference selection mode set by a data input device. [Operation] In the present invention, it is determined whether the count is within an allowable range based on the reference position and the position of the dead stopper at the forward end, and if it is, the count is reset to the reference value and the operation is continued, while If it is outside the allowable range, it is determined that there is an abnormality and the operation is stopped, so that no cumulative error occurs. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. As shown in FIG. 2, this embodiment includes a pulse generator 40, a counter 42, a reference signal generator 44, a reference point discriminator 46, and a data input device 4.
8. It is equipped with an input/output circuit 50. A random access memory (RAM) 54, a read only memory (ROM) 56, and a central processing unit (CPU) 58 are connected to the input/output circuit 50 via a common bus 52. CPU5
Reference numeral 8 denotes a reference signal output means for directly outputting the reference signal as one of the switch signals, a reset means for outputting a reset signal for replacing the count value of the counter 42 with a preset reference value α, and a data input device 48. The reference selection means switches the operations of the reference signal output means and the reset means in accordance with the reference selection mode set by the reference selection mode. The pulse generator 40 is composed of, for example, an encoder, and outputs a pulse signal that corresponds to a unit movement amount of the moving object and allows the direction to be determined. In other words, if the moving object moves in the forward direction, the forward pulse signal P _a
is output, and if the moving object moves in the backward direction, a backward pulse signal P _b is output. The pulse generator 40 is connected to a counter 42 that counts the number of pulses of the forward pulse signal P _a and the backward pulse signal P _b . The output terminal and set terminal of the counter 42 are connected to an input/output circuit 50,
A reset signal from the reset means is input to the second reset terminal. The reference signal generator 44 generates a reference signal P _c having a predetermined pulse width when a moving object reaches a predetermined reference area, and sets a reference position at a specific position in this reference area. It is connected to an input/output circuit 50 via a reference point discriminator 46. A data input device 48 is connected to the input/output circuit 50 for setting a reference value α corresponding to a plurality of switch signal numbers and reference positions. The number of the plurality of switch signals corresponds to a plurality of arbitrary positions within the range in which the position of the moving object can be detected, and is determined, for example, according to the reference selection modes A, B, and C shown in the following table.

【table】

[Table] The input/output circuit 50 also includes a reference signal generator 4.
The switch signal SW1 corresponding to the reference signal P _c output from the CPU 58 according to the control program
A control device 60 such as a mechanical sequence circuit is connected to which switch signals SW2 and SW8 corresponding to arbitrary positions of the moving object are input. Next, the operation of this embodiment will be explained with reference to FIGS. 3 and 4. First, in order to operate the reference selection means, the modes A, B, C and the decimal value reference value α in the table are set as follows.
The information is input by key operations on the data input device 48.
The reference value correction and switch signal control programs corresponding to modes A, B, and C are as follows:
B and C are stored in advance in the ROM 56. Modes A, B, input from the data input device 48,
C and the reference value α are stored in the RAM 54. Subsequently, when the moving object is moved in the forward direction or the backward direction, a forward pulse signal P _a or a backward pulse signal P _b shown in FIG. 4 is output corresponding to the unit movement amount in the moving direction. When the moving object moves into the reference area, the reference signal P _c output from the reference signal generator 44 falls to a low level, and the reference signal P c remains unchanged while the moving object moves within the reference area _.
is at a low level. Here, it is determined whether or not the moving object is moving within the reference area. If the moving object is moving outside the reference area, the switch signal SW1 is not output. Next, it is determined whether mode A, B, or C is stored in the RAM 54. If mode A is stored, a switch signal SW1 is output from the reference signal output means, and mode B or mode C is stored. switch signal SW when
1 is not output. The switch signal SW1 output in mode A is output to the control device 60,
Control moving objects. Finally, it is determined whether the reference pulse of the reference signal has risen, whether the moving object is moving in the forward direction, and whether it is in mode A or mode B. If all the conditions are YES, a reset signal is output from the reset means to the counter 42, and the counter 42
The count value of is reset to the reference value α. That is, when the reference pulse rises, the moving object is moving forward, and mode A or mode B is selected, the reference value set in the counter 42 is corrected. In addition, although the example in which mode A, B, or C is set has been explained above, the switch signal
A mode D may be set in which only SW1 is output and the reference value is not corrected. Next, a more specific embodiment in which the present invention is applied to detecting the position of a slide table of a machine tool will be described. As shown in FIG. 5, in place of the dog and limit switch in the conventional example shown in FIG. and a position detection device 53 that detects the feeding position of the slide table 18 in accordance with the output of the linear encoder 51 and outputs a switch signal to the mechanical sequence circuit 30. Since other points are similar to the conventional example shown in FIG. 1, corresponding parts are given the same reference numerals and their explanation will be omitted. The linear encoder 51 is, for example,
As shown in Publication No. 61421, the same scale 5
A reference signal magnetization section and a measurement signal magnetization section forming a magnetic grid are provided on the scale 51.
A detection head 51b equipped with a reference detection magnetic head and a measurement detection magnetic head for detecting a reference signal relative to the a-plane is provided, and a pulse signal is obtained by relatively moving the scale 51a and the detection head 51b. . In this embodiment, a scale 51a is fixed to the side surface of the slide table 18, and a detection head 51b is fixed to the slide base 14. Therefore, when the slide table 18 moves, for example, a pulse signal of one pulse per unit movement amount is output, and the movement amount of the slide table 18 is converted into a pulse signal. In this case, in order to distinguish whether the slide table 18 has moved forward or backward, depending on the moving direction of the slide table 18, a positive pulse signal as shown in FIG. A pulse signal is output. Furthermore, when the slide table 18 moves and reaches the reference area, that is, when the detection head reaches the reference signal magnetization section,
A reference signal which is a rectangular pulse signal with a width of approximately 16 mm as shown in FIG. 7 is output. These pulse signals and reference signals are input to the position detection device 53. The position detection device 53 is
An encoder input circuit 55 to which the output of the linear encoder 51 is input, an input circuit 57 to which the output from the machine sequence circuit 30, that is, an operating command, is input, and an output circuit 59 to output a switch signal to the machine sequence circuit 30. Data input device 4
8, a programmable peripheral interface (PPI) 62, a CPU 58, a ROM 56,
RAM 54 and common bus 52 that connects them
It has The RAM 54 stores various control switching positions P ₀ and P ₁ to P _{5, that is, the number of settings p 0 and P 5 corresponding} to each specific position on the slide table.
p ₁ to _{p 5} are written and stored by a separately prepared program module. This number of settings is determined by setting any one point within the reference area of the slide table as a reference position, converting the distance from this reference position to another specific position into the number of pulses, and calculating the number of settings at the reference position (reference number). It is determined by adding or subtracting this number of pulses. Hereinafter, with reference to FIGS. 8 and 9, mode A
The operation when set is explained below. DC motor 2
4 is connected to the feed shaft 2 via a gear coupling spring 49.
2 to move forward or backward the slide table 18 to which the feed nut 20 is fixed. For example, as shown in FIG. 8, the slide table 18 is fast-forwarded from point _P1 to point P2 in response to switch signals SW1 to SW4 obtained by the position detection device 53, and from _{point P2 to point P3} . The first delay is forwarded until P ₃
The second delay is carried out from point to _P5 , and finally from point _P5 to _P1 .
Fast rewind to the point. These feed speeds are preset in the speed switching setting circuit 28. The mechanical sequence circuit 30 switches speed switching contacts l _s1 to ls4 by opening and closing relays, and selects one of these feed speeds. When the feed shaft 22 is rotated by the DC motor 24, the slide table 18 moves. A positive or negative pulse signal output is obtained from the linear encoder 51 depending on the direction of movement thereof. This pulse signal is input to the encoder input circuit 55 of the position detection device 53. As shown in FIG. 9, the position detection device 53 receives an in-operation command signal from the machine sequence circuit 30 at an input circuit 57, and determines that it is in a rest state when there is no in-operation command. Mechanical sequence circuit 3
If 0 output indicates operation, linear encoder 5
Based on the positive or negative pulse signal from 1, it is determined whether the direction is forward (positive pulse signal) or backward (negative pulse signal). When the slide table 18 is in the forward state, the abnormal output (described later) of the position detection device 53 is cleared, and the pulse signal of the linear encoder 51 output is added and counted using a counter. On the other hand, when the slide table 18 is in the backward state, the number of pulses of the linear encoder output that is output as the slide table 18 moves backward is subtracted from the number of pulses of the pulse signal counted up to that time. In this way, it is constantly determined whether the counted value matches the preset switch points _p0 and _p1 to _p5 , and if they match, a switch signal corresponding to the counted value is output. . Also, when the slide table reaches the reference area, for example, the original position _P1 point of the slide table, the seventh
The reference signal shown in the figure is input to the position detection device 53, a positive pulse signal indicating that the slide table is moving in the forward direction is output, and the action of the reference point discriminator for setting the reference position At the moment when the reference signal falls (P ₀ in Figure 8),
The difference between the current count value of the counter and a set number (reference number) corresponding to a preset reference position is taken. If the absolute value of this difference is within the allowable value, the count value of the counter is reset to the reference number. on the other hand,
If the difference is excessive, it is considered that the counter value has deviated from the actual position of the slide table 18 due to an abnormality in either the mechanical or electrical system.
The abnormal state is displayed on a display circuit (not shown), and an abnormal output signal is output to the machine sequence circuit 30 to stop the machining. In this way, the amount of movement of the slide table 18 is
The reference signal is output in accordance with the forward or backward movement of the slide table 18, with the position corresponding to the falling point P ₀ of the reference signal output in the forward state as the reference position. The positive or negative pulse signals of the linear encoder 51 are added or subtracted by a counter, and the slide table 1
It is determined by making a one-to-one correspondence between the position of 8 and the count value of the counter. The CPU 58 calculates the count value of the counter and
Compare and match the set numbers p ₁ to _{p 5} corresponding to the predetermined positions P ₁ to P ₅ input to the RAM 54, and if they match, change the on/off state of the switch signals SW1 to SW4 and output via the PPI 62. Output to circuit 59. Thereby, the mechanical sequence circuit 30 is controlled according to the position of the slide table 18. As the machining of the workpiece 12 progresses and the stopper 36 on the slide table 18 side reaches the forward end predicted position P ₄ set near the dead stopper 37 fixed to the end surface of the slide base 14, the speed switching The contact l _s4 is activated, and a forward end confirmation timer (not shown), which is set for a time sufficient for the slide table 18 to hit and press the forward end stopper 37, is activated, and the current control circuit controls the current according to the output from the mechanical sequence circuit 30. Restrict. The slide table 18 moves forward and reaches the forward end setting position.
When it reaches around the _P5 point, it hits the dead stopper 37 and presses it. In this case, due to the action of the current limiting circuit, a current exceeding a preset limit value does not flow through the DC motor 24, so the speed feedback circuit of the DC motor 24 maintains a stable constant current value. Therefore, the slide table 18 is pressed to the forward end position with a constant torque, and extremely high positioning accuracy can be ensured. At this time, the forward end setting number p ₅ and slide table 1
If the difference between the count value counted by the counter and the position where the slide table 8 hits and pressed the dead stopper 37 is larger than the allowable value, this is also considered to be a serious trouble, an abnormal signal is output, and the slide table 18
stop moving. When the forward end confirmation timer times up, a quick return command is given by the mechanical sequence circuit 30, and the slide table 18 is moved to the dead stopper 37.
Move away from and return to the original position _P1 . When the slide table 18 retreats to the original position _P1 , the switch signal SW1 is output and the machine sequence circuit 30
outputs a stop command to the DC motor 24 to stop the movement of the slide table 18. By the way, since the slide table 18 is returned at high speed, it cannot stop at the original position _P due to inertia force, and it will overrun further to the return side than the original position. However, when moving back, that is, in the backward state , even if the reference signal is output from the linear encoder 51, the counter is not reset to the reference value,
The subtraction continues, and at the position where the slide table 18 actually stops, the counter count value becomes smaller than the reference value. In the next machining cycle of the slide table 18, a forward command is given again and a positive pulse signal is output from the linear encoder 51, so that the counter increments. Then, when the slide table 18 moves forward again and reaches the original position P ₁ , the reference signal is output, and the table 18 moves forward further and the moment when the reference signal falls, that is, the position
At _P0 , the counter count value is reset to a preset reference value. Therefore, even if there is an overrun when returning, there will be no error in the next position detection, and there will be no accumulation of errors. Even near the forward end, that is, _P5 , it is determined whether the difference between the set number and the counted value is within the allowable value, so that accumulation of errors can be avoided in this area as well. [Effects of the Invention] According to the present invention, it is possible to obtain a position detecting device for a moving object that performs count tolerance determination and count correction between the reference position and the position of the dead stopper at the forward end, and does not generate cumulative errors. , the shape processing accuracy of the workpiece in the direction of the moving axis is increased.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional feed control device for a machine tool, FIG. 2 is a block diagram showing an embodiment of a position detection device according to the present invention, and FIG. 3 is a diagram showing the operation of the embodiment of FIG. 2. Flowchart, FIG. 4 is a diagram showing each signal waveform of the embodiment of FIG. 2, FIG. 5 is a diagram showing a more specific embodiment of the present invention, and FIGS. 6 to 8 are diagrams of the embodiment of FIG. FIG. 9 is a flowchart showing the operation of the embodiment shown in FIG. 5, which shows signal waveforms. 40... Pulse generator, 42... Counter, 44... Reference signal generator, 46... Reference point discriminator, 48... Data input device, 50... Input/output circuit, 52... Common bus, 53... Position detection device, 54... RAM , 55...
Encoder input circuit, 56... ROM, 57... Operating command input circuit, 58... CPU, 59... Switch signal output circuit, 60... Control device, 62... PPI.

Claims (1)

[Scope of Claims] 1. A pulse generator that outputs a pulse signal that corresponds to a unit movement amount of a moving object and can determine the direction; and a reference signal generator that outputs a reference signal when the moving object reaches a predetermined reference area. a reference point discriminator that sets a reference position at a specific position in the reference area, a counter that counts the number of pulses of the pulse signal, and the reference position and the forward end dead stop position of the moving object. a data input device for setting a plurality of switch signal numbers corresponding to a plurality of positions within a position detectable range and a reference value corresponding to at least the reference position and the forward end dead stopper position; A position detecting device for a moving body including a memory for storing and a processing device that calculates according to a predetermined control program and outputs a switch signal, wherein the processing device directly outputs the reference signal as one of the switch signals. a signal output means; and a reset means for resetting the count value to the reference value when the difference between the count value of the counter and a preset reference value is within a predetermined value at least at the reference position and the forward end dead stopper position. . A moving object position detecting device comprising: a reference selection means for switching operations of the reference signal output means and the reset means according to a reference selection mode set by the data input device.