JPH02239303A - Backlash correction circuit - Google Patents

Abstract

PURPOSE:To reduce the vibration of a mechanical system and abnormal sound by distributing a unit correction quantity which is obtained by means of subdividing a backlash correction quantity at a prescribed period. CONSTITUTION:The target backlash correction quantity is previously stored in a memory 11. When a position shift command 1 discriminates a shift direction and the direction is inverted, a direction discrimination part 10 generates and outputs a direction discrimination signal 3 showing the inverted direction. A multiplier 12 multiplies the signal 3 and the output 4 of the memory, and outputs it to an adder/subtracter 13. It outputs an result adding the output correction quantity 5 of the multiplier 12 with a net correction quantity 9 and a result subtracting a unit correction quantity which a backlash correction signal 8 shows from the quantity 9 to an accumulator 14. The output of the adder/ subtracter 13 is stored in the accumulator 14 as the net correction quantity. A control part 15 repeatedly outputs storage data of the accumulator 14 as the signal 8 at every prescribed period. The signal 8 is added to the command 1 in an adder 16 and is outputted to outside as a position shift command 2 obtained by adding the backlash correction of the mechanical system to the original locus command of a tool and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a backlash correction circuit that corrects backlash in a mechanical system in a numerical control device. <Prior Art> As is well known, numerical control devices that control machine tools are used in various technical fields for the purpose of automating production and saving labor, but basically they are numerical control devices that control machine tools.
A position movement command for moving the position of a tool, etc. is generated based on a command regarding the movement trajectory of a tool or workpiece by a control program, thereby making it possible to obtain a desired product. And in many cases
The direction of movement of tools, etc. is usually reversed after reaching the end without reversing midway, but there are also control systems, such as electric discharge machining, in which the electrode moves forward and backward repeatedly. By the way, backlash is inevitable in mechanical systems, so if the direction of movement of a tool, etc. is reversed, the amount of movement will be affected by backlash. Therefore, this backlash is corrected, but since the amount of backlash is known in the target mechanical system, conventionally, a predetermined backlash correction amount is applied to the target mechanical system at once every time the position movement command is reversed. I'm trying to distribute it. (Problems to be Solved by the Invention) However, with the conventional correction method in which backlash is corrected by a predetermined amount at once, there is a problem in that vibrations, abnormal gear noise, etc. are generated in the mechanical system. This problem can be considered to be less of a problem if the direction of movement of the tool, etc. is not reversed midway, but it can be ignored if the direction of movement of the tool, etc. is frequently reversed midway, such as in the electric discharge machining control described above. This is a problem that cannot be done. In this case, by reducing the amount of backlash correction, it is possible to keep the occurrence of vibrations within an acceptable range, but this will significantly reduce machining accuracy, so improvements are desired. The present invention was made in view of such conventional problems, and its purpose is to compensate for backlash without generating vibration or abnormal gear noise in the mechanical system when the moving direction of a tool or workpiece is reversed. The purpose is to provide a backlash correction circuit. (Means for Solving the Problems) In order to achieve the above object, the backlash correction circuit of the present invention has the following configuration. That is, the backlash correction circuit of the present invention is a backlash correction circuit that corrects backlash of a mechanical system in a numerical control device; Storage means; Receiving a position movement command to move the position of the tool arm or workpiece, determines the movement direction indicated by the command, and when the direction is reversed, outputs a direction determination signal indicating the reversed direction. a determining means; and a directionality imparting means for imparting the directionality to the desired backlash correction amount when the direction discrimination signal is input and outputting the resultant; Addition/subtraction means for outputting the added value and outputting the result obtained by subtracting the unit correction amount indicated by the backlash correction signal from the net correction amount;
a second storage means for storing the output of the addition/subtraction means;
The second storage means outputs the entire stored data as the net correction amount from the second storage means, and extracts a unit correction amount from the net correction amount and forms and outputs the backlash correction signal based on the unit correction amount. control means that repeatedly performs the operation at predetermined intervals until the stored data becomes zero; taking the position movement command as one input, the backlash correction signal as the other input, and outputting a new position movement command with backlash correction taken into account; With the output means:
It is characterized by having the following. (Function) Next, the function of the backlash correction circuit of the present invention configured as described above will be explained. If the moving direction is reversed when the data stored in the second storage means is zero, a desired backlash correction amount with directionality is stored in the second storage means. Then, the control means outputs the entire stored data (net correction amount) from the second storage means to the addition/subtraction means, and extracts a unit correction amount from the net correction amount and forms and outputs a backlash correction signal based on it. ．． On the other hand, the addition/subtraction means subtracts the unit correction amount indicated by the backlash correction signal from the net correction amount, and the subtraction result value becomes the stored content (net correction amount) of the second storage means. Then, the control means performs the above-described operation after a predetermined period has elapsed. Thereafter, in the same manner, backlash correction signals are sequentially formed and output while subtracting the stored contents (net correction amount) of the second storage means by the unit correction amount at every predetermined period. If there is no reversal of the moving direction during this time, the above operation is repeated until the memory content of the second storage means becomes zero. Furthermore, if the moving direction is reversed before the stored content of the second storage means becomes zero, the "direction" of the desired backlash correction amount input to the addition/subtraction means will be the same as the stored content of the second storage means (net Since the "direction J" of the amount of correction is opposite to each other, the result value obtained by adding the two by the addition/subtraction means, that is, the difference value, is stored in the second storage means, and based on this, the backlash correction signal is calculated in the same manner as described above. is formed.
As a result, the output means outputs a new position movement command that takes backlash correction into consideration. In addition,"
The "unit correction amount" is determined, for example, corresponding to the control unit of the mechanical system, and the "predetermined period" is appropriately determined based on the control mode such as the input interval of position movement commands and the frequency of direction reversal. As explained above, according to the backlash correction circuit of the present invention, instead of distributing a desired amount of backlash correction all at once, it is possible to divide the desired backlash correction amount into smaller units and distribute them at predetermined intervals. Since the amount distributed per time is reduced, vibrations and abnormal gear noises occurring in the mechanical system can be significantly reduced. Therefore, even in a numerical control device that uses a control method that frequently reverses the moving direction of a workpiece, etc., it is possible to control the position of the workpiece, etc. while maintaining quietness. (Example) Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a backlash correction circuit according to an embodiment of the present invention. In FIG. 1, a position movement command 1 is generated based on a command regarding the movement trajectory of a tool, etc. by an NC program, and for example, as shown in FIG. 2 (1),
Consisting of a positive pulse (“1”) indicating movement in the forward direction and a negative pulse (“-1”) indicating movement in the reverse direction, at times T1 and T2
, the same TS, and the same T4 show that the direction of movement is reversed. This position movement command 1 is sent to a direction determination unit 10 and an adder 1.
It is supplied to one addition input of 6. The direction determination unit 10 determines the movement direction indicated by the position movement command 1, forms a direction determination signal 3 indicating the reversed direction when the direction is reversed, and outputs it to one multiplication input of the multiplier 12. ．． For example, as shown in FIG. 2 (2), the content of position movement command 1 changes from the forward direction (“1”) to the reverse direction (“-1”) at time Tl.
”), at this point the direction determining unit 10 outputs the negative pulse direction determining signal 3 whose content is the opposite direction (“-1”).
Form and output. A direction discrimination signal 3 indicating a predetermined direction is similarly generated from time T2 to time T4. A desired amount of backlash correction is stored in the memory 11 in advance. This desired amount of backlash correction is a predetermined value that becomes fixed once the target mechanical system is determined, and in this embodiment, the value "
4". The output 4 of this memory 11 is the value "4"
This becomes the other multiplication input of the multiplier 12. The multiplier 12 multiplies the direction determination signal 3 and the memory output 4 and outputs the result to the adder/subtractor 13. That is, time T! Then, since the direction discrimination signal 3 is a negative pulse (-1"), the multiplication output 5 becomes "-4". In other words, the multiplier 12 gives directionality to the desired backlash correction amount ('4J). The adder/subtractor 13 adds the output correction amount 5 of the multiplier 12 and the net correction amount 9, outputs the resulting value 6 to the accumulator 14, and calculates the unit correction amount indicated by the backlash correction signal 8 from the net correction i9. It performs subtraction and outputs the result value 6 to the accumulator 14. The output of the adder/subtractor 13 is stored in the accumulator 14 as a net correction amount ((3) in FIG. 2). Control part 1
5 monitors the presence or absence of stored data (the above-mentioned net correction amount) in the accumulator 14, and if there is stored data, the data is stored in the accumulator 14 every predetermined period ΔT (FIG. 2 (4)) until the stored data reaches zero. Net correction amount 9 which is the stored data from
is output to the adder/subtractor 13, and the data 7 of the unit correction amount is extracted from the net correction amount, and a backlash correction signal 8 of a polarity that takes into account the polarity of the data 7 is repeatedly formed and output (Fig. 2). (4)). This backlash correction signal 8 is output to the other input of the adder 16 and the adder/subtracter 13. Hereinafter, the process of forming the backlash correction signal 8 will be explained in detail with reference to FIG. Note that the "r unit correction amount" is determined corresponding to the control unit of the target mechanical system, but in this example, the accumulator 1
It is set to be the same as the value "1" which is the minimum unit of the net correction amount stored in 4. Further, the predetermined period ΔT is appropriately determined based on the control mode such as the input interval of the position movement command 1 and the frequency of direction reversal. As described above, at time T1, the output correction amount of the multiplier 12 is the value "-4". The control unit 15 causes the accumulator 14 to output the net correction amount 9, which is the stored data, to the adder/subtractor 13 in response to the generation of the direction discrimination signal 3 at time T1. Then, the addition result value output of the adder/subtractor 13 is the value "
-4J, which is stored in the accumulator 14 as the net correction amount. Then, when the fftl1 controller l5 confirms the existence of the stored data in the accumulator 14, it outputs the net correction amount (r-4J) 9, which is the stored data, to the adder/subtractor 13, and also outputs the net correction amount (r-4J) 9, which is the stored data. ), the data 7 of the unit correction amount ('-IJ) is taken out, and the first backlash correction signal (negative value) 8 is formed and output. In response to the generation of the backlash correction signal 8, the adder/subtractor 13 subtracts the unit correction amount "-1" from the net correction amount "-4". As a result, the net correction amount, which is the data stored in the accumulator 14, has a value of "-3". The control unit 15 forms and outputs the second backlash correction signal 8 by the same procedure as described above after a predetermined period ΔT has elapsed after the first backlash correction signal 8 was generated. In this way, the control unit 15 sequentially forms up to the fourth backlash correction signal 8 at every predetermined period ΔT, but since the data stored in the accumulator 14 becomes zero, the fifth backlash correction signal does not occur. Next, at time T2, the moving direction changes to the positive direction, so the value "4" is stored in the accumulator 14. Then, four backlash correction signals (positive values) 8 are generated using the same procedure as described above. The above is accumulator 1
This is a case where there is no change in the moving direction during the period until the stored data becomes zero in 4, but if there is a change in the moving direction before the stored data becomes zero, the following will occur. At time T3, the value "-4" is stored in the accumulator 14, the first and second backlash correction signals (negative values) 8 are sequentially formed in the same procedure as above, and the contents of the accumulator 14 are It becomes "12". Subsequent predetermined period Δ
Since a change occurred in the moving direction at time T4 before T elapsed, the adder/subtractor 13 adds the output correction amount "4" of the multiplier 12 and the net correction amount "-2". As a result, the content of the accumulator 14 becomes "2". Therefore, the control section 15
will respectively form two backlash correction signals (positive values) 8 at timings after time T4. Finally, the backlash correction signal 8 formed as described above is added to the position movement command 1 by the adder 16, and the backlash correction of the mechanical system is added to the original trajectory command of the tool etc. It is output to the outside as position movement command 2. (Effects of the Invention) As explained above, according to the backlash correction circuit of the present invention, the desired backlash correction amount is not distributed all at once, but is divided into unit correction amounts at predetermined intervals. By making it possible to distribute the product and reducing the amount of each distribution, it is possible to significantly reduce vibrations and abnormal gear noises that occur in the mechanical system. Therefore, even in a numerical control device that uses a control method that frequently reverses the moving direction of a workpiece, etc., it is possible to control the position of the workpiece, etc. while maintaining quietness.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a backlash correction circuit according to an embodiment of the present invention, and FIG. 2 is a time chart illustrating the operation of FIG. 1. 10... Direction determination unit,
11... Memory, 2... Multiplier, 3... Adder/subtractor, 4... Accumulator, 5... Control section.

Claims (1)

[Claims] A backlash correction circuit for correcting backlash in a mechanical system in a numerical control device; This backlash correction circuit includes: a first storage means for storing a desired amount of backlash correction; a direction determining means for receiving a position movement command to determine the direction of movement indicated by the command, and outputting a direction determination signal indicating the reversed direction when the direction is reversed; Directivity imparting means for imparting directionality to the desired backlash correction amount and outputting it; outputting a sum of the output correction amount of the directionality imparting means and a net correction amount; an adding/subtracting means for outputting a result obtained by subtracting the unit correction amount indicated by the backlash correction signal; a second storing means for storing the output of the adding/subtracting means; and a second storing means for storing the entire stored data from the second storing means. outputting the net correction amount, and extracting a unit correction amount from the net correction amount and forming and outputting the backlash correction signal based on the unit correction amount at predetermined intervals until the data stored in the second storage means becomes zero. and output means for outputting a new position movement command incorporating backlash correction, with the position movement command as one input and the backlash correction signal as the other input. backlash correction circuit.