DE2104162A1 - Circuit arrangement for the provision of setpoints and correction for the advance of machine tools - Google Patents

Description

Circuit arrangement for the provision and correction of setpoints for Feed drives of machine tools The invention relates to a circuit arrangement for the provision and correction of setpoints for feed drives of machine tools in connection with an input device of a subsequent digital sorting attitude and a digital-to-analog converter to control the feed drive.

There are known very precisely working drives that are used in automatic Machines are mostly designed as variable speed drives. These control drives are au9 built on an analog, digital or analog-digital basis.

Analog control drives are relatively simple in their basic structure and work very quickly. However, there are disadvantages with regard to their temporal constancy, the achievable accuracy and the great adjustment effort.

Control drives that work purely digitally are analogue controllers with regard to superior to their long-term constancy and the achievable accuracy, they require however, have a larger basic structure and are dynamically worse.

Due to the described advantages and disadvantages of purely digital or In purely analog devices, a combination of both methods is often used.

It is known to use the angular speed of the drive to convert a suitable measuring disk into a proportional pulse frequency and with a target pulse frequency; to sergloichen. The impulse difference thus obtained is connected to the analog part via a differential counter and a digital-to-analog converter of the drive superimposed. A common adjustment of the analog and digital setpoints, the counter capacity can be kept small, but this is difficult is to be realized. To avoid this, it is also common to use the analog setpoint and actual value can be taken from the setpoint and actual value transmitter via digital-to-analog converter.

In any case, an expensive digital one is required for precise regulation Use actual value transmitter with high pulse frequency.

The following counter must also be designed for a high counting frequency be. Furthermore, additional measures are necessary so that the difference is counted no impulses are lost.

The purpose of the invention is to overcome the disadvantages of the known designs and the advantages of digital control in terms of long-term constancy and use accuracy with minimal effort.

The creation is based on the task that with a digital Measurement and evaluation of the feed rate of the programmed feed rate setpoint can be corrected with the aim of reducing the difference between the set and actual feed rates to keep the feed drive extremely small with simple means.

According to the invention, this object is achieved in that a digital predetermined arithmetic feed rate setpoint by means of a logic circuit and a Pulse generator as well as a gate circuit and another logic circuit in one Counter is stored. This counter is via a digital Analog converter connected to a feed drive, of which the feed actual value is a comparator is fed. The comparator is based on the comparison measurement of the actual feed rate with the feed setpoint value supplied, if the feed values coincide with the named gate circuit and in the event of non-coincidence via the second logic circuit connected to the counter for correcting the feed setpoint for the feed drive.

In a further pursuit of the invention, the counting frequency of the counter by changing the pulse frequency of the pulse generator depending on the feed rate deviation can be varied.

Furthermore, the Vs setpoint values supplied to the comparator can be used derived from another movement, e.g. the spindle speed.

For the device according to the invention, while maintaining the Advantages of a digital control, a minimal effort required. This arises from the simple design of the comparator with the three output signals for Feed increase, feed decrease and coincidence of the feed speeds and due to the low counting capacity and limit frequencies required, the pulse generator and counters.

The invention is to be described in more detail below using an exemplary embodiment explained. The accompanying drawing shows the block diagram of a feed control drive.

From an input device E, for example a punched tape reader, the control information influencing the feed rate is how programmed Feed rate, helix angle, thread pitch, work spindle speed, etc., to one Evaluation circuit A passed on. The evaluation circuit A forms these programmed Control commands a computational feed set value VR i digital form.

This nominal feed rate vR is initially set via a logic circuit 111, a circuit T and a logic circuit L2 are stored in a counter Z. For this purpose, the Counter Z, from one connected to the gate circuit T. Pulse generator JG, pulses supplied. The gate circuit T is opened by an auxiliary command transmitter E1, which simultaneously counts up in the logic circuit L2 initiates. As soon as there is coincidence between the numerical value in the logic circuit L1 of the counter Z and the output numerical value of the evaluation circuit A is reached, the control commands to "switch off the min memory from the evaluation circuit" take place A11 and "Start of the feed drive VAtt. The computational or corrected feed set value vK is thereby made by means of a digital-to-analog converter DA converted into an analog feed rate setpoint VA and this is used for control of the feed drive VA.

With the triggering of the feed drive VA starts at the same time Comparator V with control measurements of the actual feed rate, the Actual feed value v, For reasons of accuracy, this measuring device is expedient work on a digital basis. In the comparator V, the actual feed value is vJ compared with the nominal feed rate vS. From the comparator V the three possible Measurement results for feed reduction or

to increase the feed rate to the logic circuit L2 or in the event of coincidence the feed setpoint and actual value are output to gate circuit g.

The reference variable feed setpoint vS can be in different ways can be formed, e.g. by means of a self-frequency, from the actual values of the spindle speed or the feed rate of other axes.

If the comparator V gives the result of the measurement of the coincidence of the feed values off, the gate circuit T is closed and none of the pulse generator JG arrives Ilapulse more on the counter Z. The digital corrected stored in the counter Z. The nominal feed rate vK is therefore retained. With the measurement results in the Comparator V for increasing the feed rate or

-reduction, the gate circuit T remains open and via the logic circuit L2 the counter Z au9 is switched up or down counting. This will the numerical value of the counter Z and thus the nominal feed rate vK are corrected.

The changes to the feed setpoints VK are carried out as long as until coincidence between the nominal feed rate vS and the actual value v is achieved.

The counting speed of the counter Z and thus the rate of change of the feed set value VK is determined by the pulse frequency J of the pulse generator JG.

A coarse and fine adjustment is possible by changing this pulse frequency J of the feed set value vK possible.

Claims (3)

Patent claims: 1. Circuit arrangement for the provision and correction of setpoints for feed gears of machine tools in connection with an input device, a subsequent digital evaluation circuit and a digital-to-analog converter for controlling the feed drive, characterized in that a digitally predetermined Arithmetic nominal feed rate VK by means of a logic circuit (L1) and a pulse generator (JG) as well as a gate circuit (T) and a logic circuit (L2) in a counter (Z) is stored, which is via a digital-to-analog converter (DA) with a feed drive (VA) is connected, of which the actual feed value vJ is fed to a comparator (V) corresponding to the comparison measurement with the feed setpoint supplied v5 with coincidence of the feed values with the gate circuit (T) and with non-coincidence Via the logic circuit (L2) with the counter (Z) to correct the pre-set target value VK for the feed drive (VA) is connected. 2. Circuit arrangement according to claim 1, characterized in that the counting frequency of the counter (Z) by changing the pulse frequency (J) of the pulse generator (JG) is varied depending on the feed deviation. 3. Circuit arrangement according to claim 1, characterized in that the advance setpoint o vS fed to the comparator (V) from another movement, e.g. the spindle speed.