GB2042769A - Controlling interdependence of leading and following drives - Google Patents

Abstract

The drive of a following spindle (e.g. in a gear hobbing machine) is controlled in dependence upon the path of a leading spindle by cyclically determining an increment of the following path from an increment of the leading path and the transmission factor. The leading and following paths are divided into associated intervals of integral numbers of increments. These intervals are stored with the rounded-off transmission factor for each pair of intervals. Path incrementing signals from a measuring device coupled to the leading spindle are totalised, reduced by the stored interval and multiplied by the transmission factor to provide a required following path value. This is reduced by the stored following interval and compared with the following path value of the preceding cycle to produce the following path increment. <IMAGE>

Description

SPECIFICATION Controlling interdependence of leading and following drives The invention relates to a method and circuit arrangement for controlling a following path of a following drive in dependence on a leading path of a leading drive, with a given transmission factor between the leading and following drive, using an increment of the following path set point determined cyclically from the increment of the leading path value and the transmission factor. The invention is more particularly intended for application in obtaining independent tool-workpiece movements, produced by separate drives, in machine tools, such as hobbing machines.

Control methods and systems are known for producing a required following path value in dependence on a leading path value, with a given following path incremental ratio. These systems are all aimed at enabling separate drive motors to be used for the leading and following drives, the required transmission ratio between the leading and following drives being so obtained via an electronic circuit as to ensure that both drives are positive even when loaded.

By purely incremental operation, these methods and systems produce a corresponding increment of the required following path value from the leading path covered, the path increments of the leading path being taken up by an incremental transmitter and fed into the electronic circuit.

One variant of the electronic circuit uses dividers to produce the required following path value, but has the disadvantage that not all the following path incremental ratios can be obtained. All the following path incremental ratios can be obtained with an adequate degree of accuracy and at a correspondingly high cost, if dividers and multipliers are used in the electronic circuit (Federal German Patent Specification No. 1 438 932). With high measuring resolutions of the spindle of the leading drive, high working speeds (high adjusting speeds of the leading drive spindle) and following path incremental ratios which can be represented only by relatively large integers, the working speeds become impracticably high for the dividers and multipliers.

For this reason, either the high measuring resolutions or high adjusting speeds must be abandoned, if electronic circuits of this kind are used. If the leading and following drives are also required to operate in the given dependency ratio even when the direction is reversed, twice the amount of electronic circuitry is required.

In another manner of forming the following path increment electronically, disclosed in German Democratic Republic Patent Specification 90 919, the associated following path increment, which is numerically equal to the following path incremental ratio, is totalised per leading path increment arriving, and the full increments are passed on as a path increment to the following spindle drive, while the fractional residue is added to the next following path increment when the next leading path increment arrives.

With each addition a following path error is produced which becomes smaller in proportion as the number of places of the following path incremental ratio following the decimal point increases, that is to say the smaller the rounding-off error is. The rounding-off error is additive with each leading path impulse arriving, so that when the constrained association between following drive and leading drive is maintained for relatively long periods, as is the case, for instance, in the hobbing of gear wheels, impermissible path errors are quickly produced. For this reason, in spite of a high internal number of places, zero re-setting between the leading spindle (tool spindle) and the following spindle (workpiece spindle) becomes necessary at pre-determined intervals with this method of controlling following drives.

The zero re-setting returns the leading and following spindles to a clearly defined starting position.

The disadvantages of this method are that the rounding-off of the numbers produces a systematic following path error which, more particularly when the method is used for the hobbing of gear wheels, results in flank direction errors and to a lesser extent in pitch errors of the toothing. Due to the roundingoff of numbers objectively necessary for calculation operations, the following path incremental ratio is also interrupted and therefore rounded-off after a pre-determined number of places following the decimal point.However, the finer the measuring resolution of the leading spindle is made, in order to obtain a required accuracy of angular path and steadiness in the following movement, the more the following path error increases, since a large number of calculation operations must be performed for the same following path distance to be covered, and the rounding-off error enters again into every calculation operation.

Another disadvantage is that in order to maintain the permissible flank direction errors, the following path incremental ratio must be given with a correspondingly large number of places, that is to say with a correspondingly high degree of accuracy, and therefore an elaborate addition must be carried out during real time operation. The frequency of performing this addition changes with the operating speed (the speed of the leading and following drives), so that high operating speeds demand high addition frequencies. In this case also, to avoid the disadvantageous changes of the addition frequencies and enable a constant addition frequency, the measuring resolution of the leading spindle must be elaborately adapted to the tool speed (the speed of the hobbing machine in the hobbing of gear wheels).

It is an object of the invention to provide a method enabling control of the following path in dependence on the leading path with a high degree of accuracy, even with high speeds of the leading and following drives, while at the same time further reducing the amount of circuitry required.

The invention is directed to the problem of providing a method for controlling a following path of a following drive in dependence on a leading path of a leading drive, with a given transmission factor between the leading and following drives, using an increment of the required following path value, determined cyclically from the increment of the leading path value and the transmission factor, and alsoto the provision of a circuit arrangement for the performance of the method.

Irrespective of the length of the leading paths, even if their direction of movement changes as frequently as may be required, the method prevents any following path errors being additive in dependence on the leading path covered during the formation of the following path, and enables a desired degree of measuring resolution to be obtained independently of the speed of the leading drive.

The invention allows a constant scanning time, such as is most convenient for control systems using a computer and inductive path-measuring devices, such as Inductosyn devices. The number of numerical places involved in calculations is also kept low, thus reducing the complexity of the circuitry and the computer.

The invention consists in a method for controlling a following path of a following drive in dependence on a leading path of a leading drive, with a given transmission factor between the leading and following drives, using an increment of a set point of the following path determined cyclically from the increment of the leading path value and the transmission factor, wherein the leading and following paths are subdivided into associated interval distances; the interval distances are continuously stored by value and the associated transmission factor is determined rounded-off for the leading and following path interval distances and these are stored in association; the leading path covered is totalised and, if the interval of the leading path is exceeded, the leading path is brought to a new relative leading path value by means of the value stored for the exceeded leading path interval distance, and the following path set point is determined as an increment per cycle, on the one hand from the new following path value formed by means of the relative leading path value and the rounded-off transmission factor and the stored old following path value, and on the other hand from the associated stored values of the following path interval distances when their interval limits are exceeded, such increment being imposed on the following drive, so that the leading and following paths are dealt with as associated interval distances.

Preferably, when the leading path interval is exceeded and the leading path increases, the relative leading path value is produced by reducing the totalised required leading path value by the associated stored value of the leading path interval distance, while when the leading path interval is exceeded and the leading path decreases, the relative leading path value is produced by increasing the totalised required leading path value by the associated stored value of the leading path interval distance, and the rounded-off following path value per cycle is placed in intermediate storage and the deviation from the following path value placed in intermediate storage in the preceding cycle is imposed as a following path incremental value on the following drive, and when the limit of a leading path interval distance is reached, the associated stored value of the following path interval distance is called in and is added, with increasing leading path, to the determined rounded-off following path value, and when the leading path decreases is added to the rounded-off following path value placed in intermediate storage in the preceding cycle before formation of the deviation.

Advantageously, a fresh cycle is started every time a given number of leading path increments has been covered.

Alternatively a fresh cycle is started every time a given scanning time has expired.

Preferably, when a number of leading and following path interval distances have been covered in a cycle, the leading path covered since the preceding cycle is changed by the total value of the leading path interval distances passed through during this, and the associated total value of the following path interval distances passed through during this is used to form the rounded-off required following path value.

According to another preferred feature of the method according to the invention, in each case only the integral increments of the required following path value are superimposed on the following drive, and the fractional increment of the required following path value is added to the required following path value during the next cycle before the integral increments are split off.

Advantageously, only the leading path corresponding to one complete rotation of the leading spindle is subdivided into leading path interval distances, and with each further rotation of the leading spindle the identical leading path interval distance and the identical following path interval distances associated therewith are used repeatedly.

Conveniently, the leading path interval distances formed and stored are of identical value with one another.

Alternatively, with dual digital display, wherein the leading path interval distances are formed and stored by n-times halving the leading path of one complete rotation of the leading spindle.

Just as in the case of the leading path interval distances, advantageously the following path interval distances are formed and stored and are of identical value with one another.

Alternatively, with dual digital display, the following path interval distances may be formed and stored by n-times halving of the following path associated with one complete rotation of the leading spindle.

According to a further feature of the method which brings a number of advantages, the leading path interval distances of one complete rotation of the leading spindle may be of different value, but each is brought to an integer of increments and stored.

Similarly, the following path interval distances of the following path associated with one complete rotation of the leading spindle may be of different value, but each is brought to an integer of increments and stored.

The invention also consists in a circuit arrangement for controlling a following path of a following spindle drive in dependence on a leading path of a leading spindle drive, the arrangement having a measuring device coupled to the leading spindle drive, using a multiplication circuit for the formation of required following path values from the output values of the measuring device and a given transmission factor, an addressable store being provided for interval distances of the leading path, an addressable store for associated interval distances of the following path, and an addressable store for the roundedoff transmission factor associated with the associated pairs of leading and following path interval distances, in each case the associated storage places of all the stores being addressable by an interval counter, whose forward counting input is connected via a first threshold value switch to the output of a first adder whose first input is connected to the first input of a second adder and via a scanning and holding member to a first addition circuit connected to the measuring device, the backward counting input of the interval counter being connected via a second threshold value switch and the scanning and holding member to the output of the first addition circuit, the output of the first and second adders and the output of the first addition circuit being connected via a multiplexer, controlled by the first and second threshold value switches, to the multiplication circuit and a store whose output is connected as a second input to the first addition circuit, the output of the multiplication circuit extending to a second addition circuit and an intermediate store, the storage place of the store for the following path interval distances being connected via a gate, controlled by the threshold value switches, as the second input to the second addition circuit, the output of the intermediate store being connected, via a sign-changing member, as a third input to the second addition circuit, and the output of the second addition circuit being connected via a holding member to the required value input of the following spindle drive, The invention will be described with reference to an embodiment of a machine used for hobbing gear wheels. The tool drive takes the form of a leading drive having an incremental path transmitter which subdivides the leading path covered into small path increments.The workpiece carrier is connected to a drive which is operated by a position-controlling circuit, which totalises the path distances supplied to it in the form of incremental path values. When the movement is performed, these totalised path increments are reduced by the path increments performed, the number of the path increments still to be dealt with being used to form the required speed value of the workpiece drive.

The subdivision of the leading and following paths into associated interval distances is performed by dividing one complete revolution of the leading spindle into interval distances each having an integer of increments, that is to say a whole number of increments. To meet the aforementioned conditions, the integral distances can be of very different values. In the same way, the interval distances of the following path are determined, which are also brought to an integer of increments for one complete rotation of the leading spindle, having regard to the transmission factor, so that these interval distances also can be of different values.

Accordingly, associated with each interval distance of the leading path is an interval distance of the following path, which is stored in association, the transmission factor being also determined as a rounded-off value for each resulting pair of leading and following path interval distances, and being stored in association.

For the particular interval N we obtain the following associations: Interval N -3 -2 -1 1 2 3 4 Value of the leading path interval distance 20 21 21 20 21 21 20 Value of the following path interval distance 62 62 62 61 62 62 62 Transmission factor, rounded-off 3.02 3.02 3.02 3.02 3.02 3.02 3.02 For the general constrained association between the following and leading drives if, for instance, different following paths are to be obtained for the same leading paths covered (for example in the milling of extruder screws with progressive pitch), the following associations may result:: Interval N -4 -3 -2 -1 1 2 3 4 5 6 Value of the leading path interval distance 21 20 21 29 29 29 29 39 39 39 Value of the following path interval distance 62 62 62 80 80 80 80 101 100 101 Transmission factor, rounded-off 3.02 3.02 3.02 2.76 2.76 2.76 2.76 2.578 2.578 2.578 If on the other hand one or more of the values of the leading and following paths and of the transmission factor to be stored produce constant values, independent of the interval N, something which occurs in the majority of practical applications, the corresponding store block is simplified, since in each case only one value must be stored, which applies to all intervals.

A superordinate operational control system delivers cadenced calling-up signals successively per scanning cycle for the individual subsidiary functions. The leading drive moves at the speed given by the operational control system. The signals delivered by the incremental path transmitter per scanning period are totalised to form a current leading path value, and compared with the associated stored value of the leading path interval distance. When the leading path interval distance value is exceeded, in the case of forward movement of the leading spindle (that is to say increasing the leading path), the totalised leading path value is reduced by the stored value of the leading path interval distance to a new relative leading path value.Moreover, the intervals N are counted at the same time - i.e., when the travelling path interval distance value is exceeded, switching forward to the next interval is performed, and therefore the values of the travelling path interval distance, the following path interval distance and the transmission factor stored in association for that interval are operated, ready to be called in. In the case of backward direction of movement of the leading spindle (decreasing leading path), the totalised leading path value is increased by the associated stored value of the leading path interval distance to a new relative leading path value.The totalisation of the determined leading path increments to form a current relative leading path value is continued in the fresh interval, and is performed in the same manner every time the interval limit is exceeded, to form a new relative leading path value.

A rounded-off required following path value is then formed from the relative leading path value, by multiplication by the associated stored transmission factor, which is rounded-off in the upward or downward direction to accelerate and simplify multiplication. However, this rounded-off required following path value, which is therefore liable to error, is present at the following drive, as a value liable to error, only within one scanning period.

In each case the rounded-off required following path value is placed in intermediate storage until the next scanning period, and if the leading path interval distances are exceeded during the actual scanning period, the rounded-off required following path value is changed by the value of the following path interval distance determined and stored in association for that leading path interval distance -- i.e., in the case of forward direction of movement of the leading spindle, the stored value of the following path interval distance is added to the rounded-off following path value just determined, and in the case of backward direction of movement of the leading spindle, the stored value of the following path interval distance is added to the rounded-off following path value which was placed in intermediate storage in the preceding scanning period.Of the required following path value thus formed for the actual scanning period, the deviation from the rounded-off required following path value reached and placed in intermediate storage during the preceding scanning period is determined per scanning cycle and superimposed as a following path increment on the following drive.

As a result of this procedure, only very simple computing operations with a small number of places, which can therefore be carried out in a very short time, are required within a scanning period for the formation of the required following path value from the leading path value. The rounded off required following path value formed cannot lead within one interval to any additive positional errors of the following drive, since the differentiation in each case eliminates the preceding positional error and only the rounding-off error of the actual relative required following path value is left, and this is again eliminated by the differentiation, in conjunction with the associated externally determined and stored value of the following path interval distance. The absolutely accurate required following path value would always be present if the time of scanning coincided in time with the reaching of the interval distance limit, since in that case the required following path value error resulting up to that point from the rounded-off required following path value formed would be completely eliminated at each interval distance limit. This procedure for dealing in association with interval distance values of the leading path and following path has the hitherto unattained advantage that, independently of the total path covered, only small numerical values (represented by a small number of bits) must be processed, and positive operation is maintained free from additive error over a period as long as required.

The numerical values, which are moreover rounded-off, produce further simplifications of the storage and computer units for processing, and therefore also enable extremely short processing times.

In addition, operations can be performed both with a constant scanning time and also with a scanning time dependent on speed.

The constant scanning time enables high working speeds to be obtained with high measuring resolution. As a result of the subdivision of the leading and following paths, starting from one complete rotation of the leading spindle, only the values of the interval distances for the portion of the distance corresponding to an angular path of 360 degrees need to be formed and stored. An attempt should therefore be made to subdivide this portion of the distance into identical interval distances, so as to be obliged to store only one value for all the leading path interval distances, one associated value for all the following path interval distances, and one associated value for the transmission factor.

If the control device operates with a dual digital display, advantageously the leading and following interval distance values are formed by n-times halving of the integral leading spindle and following spindle incremental number corresponding to one complete rotation of the leading spindle. The leading and following spindle interval distance values can then always be represented free from error by a number with a small number of places following the decimal point.

The control method also enables the integral leading and following spindle incremental number corresponding to one complete rotation of the leading spindle to be subdivided into associated interval distances of different values, which are all integral and whose sums again produce the starting values.

As a result, the internal number of numerical places needed by the control device is reduced.

However, the associated storage and interrogation becomes more elaborate.

The method according to the invention also enables indexing and restoration of true machining position to be carried out, which are operational modes required of hobbing machines.

Corrections of errors can also be added in a very simple manner to the control operation. To produce inclined toothings by the hobbing method, the necessary additional movement is derived by a similar method from the feed spindle and also superimposed as a further following path increment on the following drive.

With synchronisation of the leading and following spindles, they must be brought into a welldefined starting position in relation to one another. For this purpose the operational control system moves the following spindle (workpiece table) into a well-defined position corresponding to a reference point given by the measuring system, the control device being zero re-set and not scanned. Then the leading spindle drive is set in motion. When the said well-defined position of the leading spindle is exceeded for the first time, the measuring system signals this to the operational control system, which then starts to time the control device.The change in leading path given off by the measuring device during the first scanning period (first scanning after the start of timing of the control device) and totalised corresponds to the path covered up to then, starting from the reference point of the leading spindle.

In the method the following drive is then operated and starts to move. As long as the control device is timed by the operational control system, no re-synchronisation is needed, not even if the leading drive has in the meantime stopped.

After one synchronisation, as many workpieces as required can be produced without resynchronisation.

When restoring the true machining position, the following and leading spindles are also brought into a well-defined position in relation to one another. The well-defined position is reached when the tool (cutter) stands centrally in the tooth gap of the roughed-out gear wheel. Restoration of the true machining position becomes necessary with separate roughing out and finishing, or after a change of tool, for example after tool re-grinding.

The procedure for restoration of true machining position can vary, the essential feature being merely that further required path portions to be covered can be provided via the read-in to the following spindle.

For instance, restoration of true position can be carried out as follows: The control device is prepared in setting-up operation for the corresponding control task. Then the leading spindle is stopped, the tool is positioned at the new place of engagement and fed radially. The operator must then correct the following spindle via the read-in and operational control system, in accordance with the deviation from the centre. Correction and radial feed then alternate until the tool is fed centrally to the full depth. The leading spindle can then be switched on and operations continued.

In order to make the invention clearly understood, reference will now be made to the accompanying drawings which are given by way of example and in which: Fig. 1 is a block circuit diagram of a following path control system, and Fig. 2 shows an internal circuit design of a multiplication circuit used in the system shown in Fig.

1.

An operational control system 1 is provided to operate the individual circuit parts of the following path control system in the correct time sequence. A leading spindle drive 2 is mechanically coupled to a measuring device 3. The electrical output of the measuring device 3 is connected to the input of a first circuit 4 to which a scanning and holding member 5 is connected. The first addition circuit 4 has two further inputs, of which one is connected to the operational control system 1, for the purposes of manual indexing and restoration of true machining position, the other input being connected to a store 6 of the particular relative leading path value reached in each case. The output of the scanning and holding member 5 is fed to a first adder 7 and a second adder 8.The first adder 7 is connected via a sign-changing member 9, and the second adder 8 is connected directly to an addressable store 10 for the interval distances of the leading path. The output of the first adder 7 is connected to a first threshold value switch 11, and the output of the scanning and holding member 5 is connected to a second threshold value switch 12. The two threshold value switches 11 and 12 are connected to a NOR member 13 whose output, like the direct outputs of the two threshold value switches 11 and 12, extends to a multiplexer 14.An interval counter 15, which in each case switches those storage places in the stores which are associated with the interval number to read-out of the stored value, is connected via its forward counting input to the output of the first threshold value switch 11, and via its backward counting input to the output of the second threshold value switch 12. The multiplexer 14 has three inputs which can be switched through at choice to a multiplication circuit 1 6. At the same time, the output of the first adder can be switched through via the multiplexer 14 to the input of the multiplication circuit 1 6. For this switched connection, the multiplexer 14 can be operated from the output of the first threshold value switch 11. However, the output of the second adder 8 can also be switched through via the multiplexer 14 to the input of the multiplication circuit 16.In this case the multiplexer 14 can be operated from the output of the second threshold value switch 1 2. Also, the input of the multiplication circuit 16 can also be connected via the multiplexer 14 to the output of the scanning and holding member 5. In this case the multiplexer 14 can be operated from the output of the NOR member 13. The output of the multiplication circuit 1 6 is connected to the input of a second addition circuit 1 7 and to an intermediate store 18, whose output is connected via a sign-changing member 1 9 to a further input of the second addition circuit 1 7. The third input of the second addition circuit 1 7 is connected via a gate 20 to an addressable store 21 for the interval distances of the following path.The gate 20 has two mutually exclusive through-switching paths, one of which can make the direct connection from the store 21 to the second addition circuit 1 7 and can be operated from the output of the first threshold value switch 11. The second through-switching path, from the store 21 to the second addition circuit 1 7, a sign-changing member 22 being incorporated in such path, can be operated from the output of the second threshold value switch 1 2.

The output of the second addition circuit 1 7 is connected via a holding member 23 to the required value increment input of a following spindle drive 24.

The multiplication circuit 1 6 (Fig. 2) comprises of a store block 25, which can be addressed via the interval counter 15, and in which the transmission factors associated with the intervals are stored.

The output of the store block 25 is connected in the form of a multiplier input to the actual multiplier 26, while the output of the multiplexer 14 is connected in the form of a multiplicand input to the multiplier 26. The product output of the multiplier 26 extends via a rounding-off member 27 which is also included in the multiplication circuit 1 6.

The addressable stores 10 and 1 9 for the interval distances of the leading and following paths, and also the store block 25 for storing the transmission factors, are connected to the operational control system 1 for the writing-in of the associated values. The measuring device 3, the scanning and holding member 5, the store 6, the multiplication circuit 16, the intermediate store 18, the holding member 23 and the following spindle drive 24 are each connected to the operational control system 1 for calling in their activation. The circuit arrangement operates as follows: In the cadence of the scanning time, the operational control system 1 successively delivers timed calling-in signals for operating the aforementioned switch elements.The leading spindle drive 2, which moves at any given speed, actuates the measuring device 3, which delivers a signal representing the path covered since the last scanning, to the addition circuit 4 for totalisation. Each totalised value obtained is held by the scanning and holding member 5 and compared in the first adder 7 with the negative value of the leading path interval distance present in the store 1 0. If the leading path interval distance limit is exceeded in the case of forward movement of the leading spindle drive 2, the totalised leading path value is reduced by the value of the leading path interval distance stored in the store 10 to a new relative leading path value, which then appears at the adder 7.The change of sign at the output of the adder 7, if the interval limit is exceeded in the forward direction, trips the threshold value switch 11, which then applies the output of the adder 7 to the multiplication circuit 1 6 and the store 6. As a result, the value of the stored leading path interval distance is deducted from the relative leading path value which was up to then applied to the multiplication circuit 1 6 by the scanning and holding member 5, via the multiplexer branch actuated by the NOR member 13, and which is related to the preceding start of an interval, so that the new relative leading path value is related to the new start of the interval.

Moreover, the threshold value switch 11 closes the gate 20 in the branch, which delivers the value of the following path interval distance which is present in the store 21 and which is associated with the interval limit exceeded, to the second addition circuit 17, thereby increasing the following path. The threshold value switch 11 also increases the contents of the interval counter 1 5 by one.

On each scanning, the actual relative leading path value is held in the store 6 and also taken into account for the further covering of the leading path, that is to say it is totalised together with the output of the measuring device 3 in the first addition circuit 4.

From the actual relative leading path value present, with the particular associated transmission factor called-in by the interval counter 5, the multiplication circuit 1 6 determines a rounded-off relative following path value which increases from scanning to scanning with forward movement of the leading spindle drive 2. From the actual relative following path value and the rounded-off relative following path value placed in intermediate storage from the preceding scanning, and the value of the following path interval distance called-in from the store when the interval limit is exceeded, the following path incremental value is formed and superimposed on the following spindle drive 24.On each scanning the actual rounded-off following path value determined by the multiplication circuit 1 6 is held in the intermediate store 1 8.

In the case of backward movement of the leading spindle drive 2, the leading path value covered in the opposite direction, that is to say the reduced leading path, is added to the stored value of the leading path interval distance in the second adder 8. If the reduced leading path value becomes zero or smaller than zero, the threshold value switch 12 is actuated and reduces the contents of the interval counter 1 5 by one. At the same time, the output of the second adder 8 is delivered via the multiplexer branch actuated by the threshold value switch 12 to the multiplication circuit 1 6, where it is processed in the manner already described for the case of forward movement.

The threshold value switch 12 also closes the gate 20 in the multiplexer branch, which delivers the value of the following path interval distance present in the store 21 via the sign-changing member 22 to the second addition circuit 17, and thereby substantially reduces the relative following path by the stored following path distance value associated with the interval limit exceeded. The following path incremental value is determined per scanning cycle in the addition circuit 1 7 and superimposed via the holding member 23 on the following spindle drive 24. Within an interval, the following path increment is obtained as a difference, the following path value of the preceding scanning cycle, placed in the intermediate storage, being added with a negative sign, due to the action of the sign-changing member 19, to the actual relative following path value. If the interval limit is exceeded, the associated stored value of the following path interval distance is taken into account in the addition circuit 1 7 when determining the following path increment, such value being added, controlled by the gate 20, with a positive sign in the case of forward movement and with a negative sign in the case of backward movement.

Claims (17)

1. A method for controlling a following path of a following drive in dependence on a leading path of a leading drive, with a given transmission factor between the leading and following drives, using an increment of a set point of the following path determined cyclically from the increment of the leading path value and the transmission factor, wherein the leading and following paths are subdivided into associated interval distances; the interval distances are continuously stored by value and the associated transmission factor is determined rounded-off for the leading and following path interval distances and these are stored in association; the leading path covered is totalised and, if the interval of the leading path is exceeded, the leading path is brought to a new relative leading path value by means of the value stored for the exceeded leading path interval distance, and the following path set point is determined as an increment per cycle, on the one hand from the new following-path value formed by means of the relative leading path value and the rounded-off transmission factor and the stored old following path value, and on the other hand from the associated stored values of the following path interval distances when their interval limits are exceeded, such increment being imposed on the following drive, so that the leading and following paths are dealt with as associated interval distances.

2. A method as claimed in claim 1, wherein when the leading path interval is exceeded and the leading path increases, the relative leading path value is produced by reducing the totalised required leading path value by the associated stored value of the leading path interval distance, while when the leading path interval is exceeded and the leading path decreases, the relative leading path value is produced by increasing the totalised required leading path value by the associated stored value of the leading path interval distance, and the rounded-off following path value per cycle is placed in intermediate storage and the deviation from the following path value placed in intermediate storage in the preceding cycle is imposed as a following path incremental value on the following drive, and when the limit of a leading path interval distance is reached, the associated stored value of the following path interval distance is called in and is added, with increasing leading path, to the determined rounded-off following path value, and when the leading path decreases is added to the rounded-off following path value placed in intermediate storage in the preceding cycle before formation of the deviation.

3. A method as claimed in claim 1 or 2, wherein a fresh cycle is started every time a given number of leading path increments has been covered.

4. A method as claimed in claim 1 or 2, wherein a fresh cycle is started every time a given scanning time has expired.

5. A method as claimed in any one of claims 1 to 4, wherein, when a number of leading and following path interval distances have been covered in a cycle, the leading path covered since the preceding cycle is changed by the total value of the leading path interval distances passed through during this, and the associated total value of the following path interval distances passed through during this is used to form the rounded-off required following path value.

6. A method as claimed in any one of claims 1 to 5, wherein in each case only the integral increments of the required following path value are superimposed on the following drive, and the fractional increment of the required following path value is added to the required following path value during the next cycle before the integral increments are split off.

7. A method as claimed in any one of claims 1 to 6, wherein, only the leading path corresponding to one complete rotation of the leading spindle is subdivided into leading path interval distances, and with each further rotation of the leading spindle the identical leading path interval distance and the identical following path interval distances associated therewith are used repeatedly.

8. A method as claimed in any one of claims 1 to 7 wherein, the leading path interval distances formed and stored are of identical value with one another.

9. A method as claimed in any one of claims 1 to 8, with dual digital display, wherein the leading path interval distances are formed and stored by n-times halving the leading path of one complete rotation of the leading spindle.

10. A method as claimed in any one of claims 1 to 9, wherein the following path interval distances are formed and stored and are of identical value with one another.

11. A method as claimed in any one of claims 1 to 9, with dual digital display, wherein the following path interval distances are formed and stored by n-times halving of the following path associated with one complete rotation of the leading spindle.

12. A method as claimed in claim 10 or 11, wherein the leading path interval distances of one complete rotation of the leading spindle are of different value, but each is brought to an integer of increments and stored.

13. A method as claimed in claim 11 or 1 2, wherein the following path interval distances of the following path associated with one complete rotation of the leading spindle are of different value, but each is brought to an integer of increments and stored.

1 4. A circuit arrangement for controlling a following path of a following spindle drive in dependence on a leading path of a leading spindle drive,the arrangement having a measuring device coupled to the leading spindle drive, using a multiplication circuit for the formation of required following path values from the output values of the measuring device and a given transmission factor, an addressable store being provided for interval distances of the leading path, an addressable store for associated interval distances of the following path, and an addressable store for the rounded-off transmission factor associated with the associated pairs of leading and following path interval distances, in each case the associated storage places of all the stores being addressable by an interval counter, whose forward counting input is connected via a first threshold value switch to the output of a first adder whose first input is connected to the first input of a second adder and via a scanning and holding member to a first addition circuit connected to the measuring device, the backward counting input of the interval counter being connected via a second threshold value switch and the scanning and holding member to the output of the first addition circuit, the output of the first and second adders and the output of the first addition circuit being connected via a multiplexer, controlled by the first and second threshold value switches, to the multiplication circuit and a store whose output is connected as a second input to the first addition circuit, the output of the multiplication circuit extending to a second addition circuit and an intermediate store, the storage place of the store for the following path interval distances being connected via a gate, controlled by the threshold value switches, as the second input to the second addition circuit, the output of the intermediate store being connected, via a sign-changing member, as a third input to the second addition circuit, and the output of the second addition circuit being connected via a holding member to the required value input of the following spindle drive.

1 5. A circuit arrangement as claimed in claim 14 arranged in a hobbing machine, the said spindle drives being a tool drive and a workpiece drive in the machine.

1 6. A method for controlling the relationship between a leading drive and a following drive substantially as hereinbefore described with reference to the accompanying drawings.

17. A circuit arrangement for use in performing the method of claim 16,-substantially as hereinbefore described with reference to the accompanying drawings.