JPH0367824B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a precision positioning device for precision machining or calibration of a length measuring device.

(Prior art) Conventional positioning devices of this type include those that measure the current position using a laser interferometer or the like and send the results as feedback to a DC servo motor; As seen in NC devices, a pulse motor generates minute steps, which are converted into linear motion via a ball screw, etc., and are sent up to about 1 meter.

(Problems to be Solved by the Invention) In the conventional technology described above, which measures the current position and feeds it back to the servo motor, high-grade measuring instruments such as laser interferometers must be used to improve accuracy. No. Further, in the conventional technology using a pulse motor, it is difficult to reduce the step width, and if it is made smaller, mechanical errors increase, so the step width is limited to about 5 to 10 .mu.m.

The purpose of the present invention is to solve these problems, that is, to enable feeding of minute steps (about 1 μm) over long distances without using high-grade measuring equipment. It is something to do.

(Means for Solving the Problems) For the above purpose, the present invention provides a first slider step-driven by a pulse motor;
a second slider that can move in parallel with the slider; a displacement detector that detects the relative displacement of both sliders; and a temporary storage means that holds the output of the displacement detector at a predetermined timing for each step. an adder that adds a constant value determined by the step width to the memory content of the storage means; and a comparator that uses the output of the adder as a comparison value and outputs the difference between it and the output of the displacement detector. , and a servo mechanism that is energized by the output of the comparator and drives the second slider for each step.

(Function) At the start point, the voltage output from the detector is set as e ₀ . When the first slider driven by the pulse motor moves forward by δ _a1 from the second slider in the first step, the detection voltage at which the relative displacement is detected by the displacement detector is set as e _a1 . As a result, the output from the detector becomes E _a1 = e ₀ + e _a1 . The output E _a1 plus the voltage (-e) for one standard step δ (E _a1 -e) is input to the comparator as a comparison value (this does not change until one step is completed).

This comparator is the subsequent output of said displacement detector.
The difference between E _a and the comparison value (E _a1 -e) is output, and this is integrated by an integrator, thereby energizing the servo mechanism. The role of the integrator is to eliminate the dead zone of the servo motor and eliminate residual deviation. The output from the comparator is E _a − (E _a1 − e),
At the beginning, E _a = E _a1 , so E _a1 −
(E _a1 −e)=e, and the servo mechanism is thereby started. When the second slider advances by a distance δ _b1 by the servo mechanism, the relative displacement between both sliders decreases by that amount and becomes δ _a1 - δ _b1 , so the output E _a of the displacement detector is E _a = E _a1 - e _b1 , and the difference between this and the comparison value is (E _a1 - e _b1 ) - (E _a1 - e) = e - e _b1 . Therefore, the amount of advance δ _b1 of the second slider is δ
When e _b1 =e, the output from the comparator becomes zero and the first step ends. Thereafter, this step is repeated n times, and n.delta. is fed.

(Embodiment) 3 and 4 are separate sliders, each supported on an air floating table 12, and can slide with extremely low frictional resistance. The slider 3 is linearly driven by a steel belt 1 placed around pulleys 5 and 6. The steel belt 1 is driven in steps by a pulse motor 14. The slider 4 is linearly driven by a steel belt 2 that is placed around pulleys 7 and 11, and its direction is parallel to the driving direction of the slider 3. The steel belt 2 is continuously driven by a DC servo motor 15. A workpiece, a tool, a pointer, etc. to be positioned is connected to this slider 4. A highly sensitive displacement detector 8 is fixed on the slider 4, and its probe 9 detects the block 1 fixed on the slider 3.
0 reference surface 10a. A displacement detector 8 detects the relative displacement between the sliders 3 and 4 and outputs a voltage E _a . This output voltage E _a is applied to one input terminal of the comparator 16 . The output voltage E _a is branched and held in a hold circuit 18 via a gate 17 . The read output of the hold circuit 18 is added to the voltage (-e) by an adder 19 and then applied to the other input terminal of the comparator 16. Comparator 16
outputs the difference E between the voltages applied to both input terminals,
It is integrated and input to the driver 20. The driver 20 drives the servo motor 1 according to the input voltage E.
Drive 5.

Next, the operation of the device will be explained.

The output of the pulse oscillator 21 energizes the pulse motor 14 via the driver 22, causing it to step forward. As a result, the slider 3 moves forward by one step. This one step is, for example, 1 μm.

As mentioned above, when the step width is made finer, the step by the pulse motor becomes inaccurate, so the actual advancing width will not be 1 .mu.m. Therefore,
Assuming that the first step width is δ _a1 , the block 10 on the slider 3 moves forward from _FIG .
Generate E _a1 . This output voltage E _a1 is the sum of the zero point e ₀ and the displacement proportion e _a1 , that is, E _a1 = e ₀ + e _a1 .
The output voltage E _a1 is applied to the positive input terminal of the comparator 16 and is also applied to the hold circuit 18 via the gate circuit 17 . The hold circuit 18 is cleared in advance, and the gate circuit 17 is turned off immediately after applying the output voltage E _a1 to the hold circuit 18. These operations are performed by a timing circuit 23 that is synchronously controlled by the output of the pulse oscillator 21.

The hold circuit 18 is immediately read out, and the adder 19 adds a voltage (-e) to its output E _a1 to output an output E _b1 , which is applied to the negative input terminal of the comparator 16. As a result, the comparator 16 calculates E ₁ =E _a1
-E _b1 is output and further integrated by an integrator, thereby energizing the DC servo motor 15.

By the way, at the start of the operation, the output E _a is the sum of the output e _a1 of the displacement detector 8 and the zero point e ₀ ,
That is, E _a1 = e ₀ + e _a1 , and E _b1 = E _a1 −
Since e, E ₁ =E _a1 −E _b1 =E _a1 −(E _a1 −e)=e
The servo motor 15 is driven by the voltage e. When the slider 4 moves forward due to the drive of the servo motor 15, the relative displacement between both sliders 3 and 4 decreases, so the output E _a of the displacement detector 8 decreases accordingly, and the amount of advance of the slider 4 is shown in FIG. 3. When it becomes δ _b1 , it changes to E _a = e ₀ + e _a1 − e _b1 . Input voltage E to the integrator in this state
is E=E _a −E _b1 = (e ₀ + e _a1 − e _b1 ) − (e ₀ + e _a1 − e)
= ee _b1 . Therefore, when e _b1 becomes e (that is, δ _b1 becomes δ), the servo motor 15
stops. This means that the slider 4 has stepped by an amount δ corresponding to the voltage e, and shows that it has nothing to do with the step width δ _a1 of the slider 3 that caused this.

When the slider 3 again advances by δ _a2 in the next step, the displacement detector 8 generates an output E _a2 =e ₁ +e _a2 , which is rewritten by the hold circuit 18 . However, e ₁ =e ₀ +e _a1 −e. Therefore, the output E ₂ of the comparator 16 is E ₂ =E _a2 −E _b2 =(e ₁ +
e _a2 )−(e ₁ +e _a2 −e)=e, and the servo motor 15 advances the slider 4 by an amount δ proportional to the voltage e.

After repeating the above cycle n times, slider 3 becomes
l _a = _o 〓 ^k=1 It moves forward by δak, and the slider 4 moves forward by l _b =nδ. Therefore, move the slider 4 at a distance determined by the voltage e, for example, in units of 1 μm.
It can be moved by an integral multiple of that distance.
That is, although the movement of the slider 4 is caused by the movement of the slider 3, it is not simply tracked, but is performed based on the voltage e, and is not affected by the length between each step caused by the pulse motor 14.

Note that if |l _a −l _b | exceeds a certain value, the distance between the sliders 3 and 4 will exceed the appropriate range, resulting in loss of synchronization. It is necessary to select the voltage e that determines the voltage e to avoid such a problem, but the step width can be changed within that range.

In the embodiment described above, steel belts 1 and 2 are used as the linear drive mechanism, but these may be a feed screw that eliminates backlash or other linear drive mechanisms. Furthermore, instead of the air floating table 12, a linear ball slider can also be used. Furthermore, a piezoelectric element can be used in place of the DC servo motor 15. This piezoelectric element is interposed between both sliders 3 and 4, and applies the displacement generated thereto to slider 4. The piezoelectric element produces a displacement proportional to the input voltage E, and since the maximum of the input voltage E is the step determining voltage e as described above, the slider 4 can be stepped by one step δ.

(Effect) The present invention uses a pulse motor as described above, but the accuracy is not determined by it, but the accuracy of the second slider is determined based on the first slider that is stepped by the pulse motor. Since relative displacement is performed by a servo mechanism and movement is performed by stacking them, the movement accuracy is determined by the servo mechanism and high accuracy can be obtained. Since the displacement detector only needs to detect minute displacements, a highly accurate one can be easily obtained, and a high-grade device such as a laser interference device is not required. Furthermore, the total length of movement can be extended as desired by increasing the number of steps.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a plan view for explaining the operation. 1, 2... Steel belt, 3, 4... 1st,
2nd slider, 8... Displacement detector, 14... Pulse motor, 15... DC servo motor, 16...
Comparator, 18...hold circuit, 19...adder, 23...timing circuit.

Claims (1)

[Claims] 1 The first step driven by a pulse motor
a second slider that can move in parallel with the first slider; a displacement detector that detects the relative displacement of both sliders; and a displacement detector that detects the output of the displacement detector at a predetermined timing for each step. a temporary storage means for holding, an adder for adding a constant value determined by the step width to the memory contents of the storage means, and an output of the adder as a comparison value, and a comparison value between it and the output of the displacement detector. A precision positioning device comprising: a comparator that outputs a difference; and a servo mechanism that is energized by the output of the comparator and drives the second slider for each step.