JPH04111752A - Spindle control device - Google Patents

Abstract

PURPOSE:To obtain a spindle control device without generating a position deviation at position control time by measuring speed change ratio of a motor shaft to a spindle based on detection values from the first detecting means for detecting a rotational position of the motor shaft and the second detecting means for detecting a rotational position of the spindle. CONSTITUTION:In a sequence control part 22, a motor position thetaMO and a spindle position thetaSO in that point of time are read from a motor shaft encoder 11 and a spindle encoder 12 in sample/hold parts 17, 18 to read and supervise a difference thetaS between the present spindle position thetaS and the spindle position thetaSO calculated by a subtracter 19, and in the point of time an absolute value ¦ thetaS¦ of this difference is increased larger than a reference value thetaCMP, a value thetaM/ S, in which a difference thetaM between the present motor position thetaM and the motor position thetaMO, calculated by a divider 21, is divided by the difference thetaS, is read. Speed change ratio KGn' is obtained and output through a switching means 23. Since action is performed by actually measuring the speed change ratio in a spindle driving system, control can be realized without generating a rotational speed error in speed control and a position error in position control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a spindle control device that controls the position or speed of a spindle having a speed change mechanism.

(Prior Art) In recent years, spindle control devices for machine tools have come to perform precise positional control of the spindle as the machine supports complex machining. In particular, lathes for complex machining with opposing main spindles have added functions that allow workpieces to be transferred between the two shafts while the two shafts are rotating, and to cut by chucking both ends of the workpiece.

One way to achieve this function is to use a master-slave method, which detects the position of one spindle and adjusts the position of the other spindle to the detected value. A system that performs position control and synchronizes the commanded positions of the amphibious axes has come to be used.

FIG. 8 is a block diagram showing an example of a spindle control device that controls the position or speed of a spindle having a conventional transmission mechanism based on the latter method described above. The subtracter 15 calculates the deviation Diff between the main shaft lO and the position θ5 detected by the encoder 12, and sends it to the position error coefficient multiplier 3, where the position error coefficient is multiplied by.

On the other hand, the amount of change in the spindle position command θ,'' is detected by a differentiator 1, and sent to a feedforward coefficient multiplier 2, where the feedforward coefficient is multiplied by 6.

Position error component speed command ω, 1 from position error coefficient multiplier 3
．． f'' and the feedforward component speed command ω6 from the feedforward coefficient multiplier 2.
The speed commands ω and ′ are calculated by the adder 16, and sent to the gear ratio data multiplier 4, where the gear ratio (=motor rotation speed/spindle rotation speed) read from the gear ratio data storage unit 14 is multiplied by 6o. Ru. The motor shaft position θ9 detected by the encoder 11 attached to the motor shaft is determined by the differentiator 13 as the motor shaft speed ω2, and this motor shaft speed ω8 is combined with the motor shaft speed command ω from the gear ratio data multiplier 4. The speed deviation from the motor shaft is amplified by the speed amplifier 5 and made into the torque command T' of the motor shaft. The current flowing through the motor 7 is controlled, and the motor shaft speed ω
8 or motor shaft speed command. ′ can be followed. The motor shaft is a belt mechanism 8 and a gear mechanism 9.
is mechanically connected to the main shaft 10 by the main shaft position θ.
5 or the spindle position command θ,”.

In general, the feedforward coefficient grr is determined by the feedforward minute speed command ω2. The gear ratio 6n is read out from the gear ratio data storage section L4 in accordance with the gear command n indicating the current state of the gear mechanism 9.

(Problem to be Solved by the Invention) In the conventional spindle control device described above, the gear ratio in the actual mechanical system is 6n (1+ε), where the error rate is ε.
, and assuming that the speed control system operates ideally and motor shaft speed command ω2 = motor shaft speed ω2, the Laplace transform Diff(S) of the position deviation Diff is calculated by the following equation (1
), (2) is expressed by the following equation (3).

Here, if S・θ5=ωso/S (ω, is constant command speed of the spindle), the steady value of Diff can be obtained as shown in equation (4) by using equation (3) and setting S−0. Ranel.

Diff=lim 5-Diff(S)=ω5o(
(1+ε) −+rr)/to 8 (4) The feedforward coefficient KFF of the velocity component is usually °“1
Since it is taken as °°, Diff=ωSo・6/2 (5), and the positional deviation Diff caused by the error in the gear ratio
is proportional to the spindle command speed ωso and the error rate ε of the gear ratio, and is inversely proportional to the position error coefficient.

Here, it is assumed that the opposing spindles chuck both ends of the same workpiece when stopped and accelerate the workpiece in synchronous rotation to the spindle command speed ωso. If there is an error rate of 6 in the gear ratio of only one main shaft, if there is no coupling, an angular difference between both shafts as shown in equation (5) above will occur, but the main shafts are mechanically coupled. Therefore, the spindle with an error rate of +6 generates torque in the direction of advancing the spindle across ωso・ε/ with respect to the command value, and the other spindles generate torque in the direction of pulling the spindle back to adjust the spindle position to the command value. This will generate torque.

As a result, torque in the torsional direction is applied to the workpiece, and when cutting with both ends chucked, the workpiece becomes threaded when the diameter of the cutting part becomes narrower. There were problems in that a torque current would flow, overheating the motor and causing overrotation, or regenerating energy in one of the main shafts that exceeded the regeneration function, causing an alarm.

The present invention was made in view of the above-mentioned circumstances,
An object of the present invention is to provide a spindle control device that does not generate position deviation during position control.

(Means for Solving the Problems) The present invention relates to a spindle control device that controls the position or speed of a spindle through a speed change function, and the above object of the present invention is to provide a spindle control device that controls the rotational position of a motor shaft. a first detection means, a second detection means for detecting the rotational position of the main shaft, and a measurement for measuring a gear ratio between the motor shaft and the main shaft based on detected values from the first and second detection means. This is achieved by providing means.

(Function) In the present invention, by constantly measuring and correcting the actual gear ratio of the main shaft, position deviation during position control is prevented from occurring, so overload etc. during pick-off are prevented from occurring. It can be prevented.

(Embodiment) FIG. 1 is a block diagram showing an example of a spindle control device of the present invention in correspondence with FIG. 8, and the same components are given the same reference numerals and the description thereof will be omitted.

This main shaft control device has an additional gear ratio measuring section 100 that measures the actual gear ratio, and a differentiator 101 that calculates the main shaft speed ω5 from the main shaft position θS.
is the gear ratio K as an initial value from the gear ratio data storage unit 14 in the initial state. . After reading and setting in the gear ratio multiplier 4, the gear ratio C is determined by a measurement method described later. No. is measured and stored in the gear ratio data storage unit 14, and is set in the gear ratio multiplier 4 to be reflected in the main shaft control.

FIG. 2 shows a gear ratio measuring section 100 using a measurement method based on angle quantities.
FIG. 3 is a block diagram showing a detailed example of the operation, and FIG. 3 is a flowchart showing an example of its operation.
Step 51. S2), motor position θ at that point
Sample/hold section 17.1 samples MO and main shaft position θ8° from motor shaft encoder 11 and main shaft encoder 12.
Have 8 read it. Then, the difference between the current spindle position θS calculated by the subtractor 19 and the above spindle position θso is Δθs=lθ
S-θsol is read and monitored (Step S3), and when the absolute value 1Δθs1 of this difference becomes larger than the reference value θCMP (Step S4), the current motor position θ2 calculated by the divider 21 and the above-mentioned motor position θMO difference Δ
θ2=1θ, -θvol divided by the above difference Δθ5 Δθ
M/Δθ8 is read (step S5). Then, the following formula (
6), the gear ratio KGn° is determined by the following equation (7) (steps S6, 57), output via the switching means 23, and the process returns to step Sl to repeat the above-described operation.

Here, the reference value θCMP is set such that the accuracy of the calculation result of the above equation (7) is sufficiently ensured, and the motor position θ8. The number of digits of the multi-rotation position of the spindle position θ5 and the number of digits of calculation in the above equation (7) are selected within a range in which overflow does not occur.

On the other hand, if the gear command n changes in step S2, the sequence control section 22 reads 6o from the speed ratio data storage section 14 into the speed ratio corresponding to the gear command n (step S8), and also reads the motor position θ2 at that point. and the main shaft position θ3 are read by the sample/halt sections 17 and 18 from the motor shaft encoder 11 and the main shaft encoder 12 (step S9). Then, the read gear ratio is set to 6o and the gear ratio is set to Gn (step 510), and the switching means 2
3 and returns to step Sl to repeat the above-described operation.

FIG. 4 is a block diagram showing a detailed example of the speed ratio measuring section 100 that uses a measurement method based on the detected speed of the main shaft and motor shaft, and FIG. 5 is a flowchart showing an example of its operation. If it is not neutral and has not changed (step 511.12), read the spindle speed ωS from the differentiator 101 and monitor it.Step 5
13), at the time when its absolute value ω,l becomes larger than the reference value ωref.

(Step 514), the motor shaft speed ω2 calculated by the divider 24 is divided by the main shaft speed ω5, which is the value ω2/
ωS is read (step 515). Then, the following formula (8
), the gear ratio Gno is determined by the following equation (9) (steps 516, 517), output via the switching means 26, and the process returns to step 511 to repeat the above-mentioned operation.

On the other hand, if the gear command n has changed in step 512, the sequence control section 25 reads the speed ratio KGn corresponding to the gear command n from the speed ratio data storage section 14 (step 518), and adds 6n to this speed ratio as the speed ratio KGn. 519) via the switching means 26 as
, returns to step Sll and repeats the above-described operation.

FIG. 6 is a block diagram showing a detailed example of the speed ratio measuring section 100 that measures positional deviation by changing the speed ratio, and FIG. 7 is a flowchart showing an example of its operation. If n has not changed and there is no mechanical connection with other spindles (steps 521, 5
22), positional deviation Diff calculated by the average processing unit 27
Average value (or low-pass filter calculation result) of Diff
is read (step 523).

Then, it is determined whether or not the average value Diff and the spindle speed command ω5' have the same polarity (step 524). If the average value Diff and the spindle speed command ωS'' have the same polarity, ΔK
Increase Gn to Δ to ΔKGn° Step 525
), if the average value Diff and the spindle speed command ω5'' have opposite polarities, ΔKGn is decreased to Δ and set to ΔKGn° (step 526). Then, when the following formula (10) is satisfied, the gear ratio KGn° is added. Step S27.528), Step 521
Return to and repeat the operations described above.

On the other hand, if the gear command n changes in step S21, the sequence control section 28 reads the speed ratio KGn corresponding to the gear command n from the speed ratio data storage section 14 and (
Step 529), initialize the average processing unit 27, step 530), set Gno to O for ΔKGn and Δ (step 531), and return to step 521 to repeat the above-described operation.

(Effects of the Invention) As described above, according to the spindle control device of the present invention, the spindle drive!
! Since the system operates by actually measuring the gear ratio of the 7 system, it is possible to perform speed control on controlled objects such as belts where the gear ratio fluctuates due to initial errors in the gear ratio relative to the design value, changes over time, tension adjustment, etc. Control that does not generate rotation speed errors or position errors in position control can be realized. In particular, it is very effective in synchronous rotation by chucking the same workpiece with opposing spindles, and prevents overheating of the motor and unit.

KGN""KGN+ΔKGN'...
...(11)

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the spindle control device of the present invention, FIGS. 2, 4, and 6 are block diagrams showing detailed examples of the main parts of the device of the present invention, and FIGS. 7 and 7 are flowcharts showing examples of operations of the main parts shown in FIGS. 2, 4, and 6, respectively, and FIG. 8 is a block diagram showing an example of a conventional spindle control device. 1.13,101... Differentiator, 2... Feedforward coefficient multiplier, 3... Position error coefficient multiplier, 4...
... Speed ratio data multiplier, 5... Speed amplifier, 6...
- Power conversion unit, 7... Motor, 8... Belt mechanism, 9... Gear mechanism, lO... Main shaft, 11... Motor shaft encoder, 12... Main shaft encoder, 14...
- Gear ratio data storage unit, 15.1920... subtractor,
15.29...Adder, 17.18...Sample/
Hold section, 21.24...Divider, 22.25.2
8... Sequence control section, 23.26... Switching means, 27... Average processing section, 100... Speed ratio measurement section. A certain 3rd grade leather 5 drawings

Claims (1)

[Claims] 1. A main shaft control device that controls the position or speed of a main shaft via a transmission mechanism, comprising a first detection means for detecting a rotational position of a motor shaft, and a first detection means for detecting a rotational position of the main shaft. 1. A spindle control device comprising: two detection means; and a measurement means for measuring a gear ratio between the motor shaft and the main shaft based on the detected values from the first and second detection means. 2. The main shaft control according to claim 1, wherein the measuring means measures the amount of change in the rotational position of the motor shaft and the main shaft within the same time period, and determines the speed ratio based on the ratio of each measured amount. Device. 3. The main shaft control device according to claim 1, wherein the measuring means measures the rotational speeds of the motor shaft and the main shaft at the same time, and determines the speed ratio from a ratio of each measured value. 4. The measuring means rotates the main shaft at a constant speed while the main shaft is in a position control state, and changes the speed ratio used for the position control so that the time average of the position deviation that occurs becomes zero. The spindle control device according to claim 1, wherein the spindle control device calculates a ratio.