DE3804634A1 - Highly dynamic electrical servo drive with a plurality of asynchronous machines - Google Patents

Abstract

Special measures are required to proportion the torques from a plurality of asynchronous machines to an individual load. In the case of highly dynamic servo drives, these measures ensure constant proportioning and avoid oscillations (vibration) even during rapid torque changes. Exact torque proportioning can be achieved in all control ranges by driving the individual asynchronous machines via separate invertors having switching transistors to which the same drive signals are applied, especially pulse-width-modulated control pulses. In this case, superordinate control loops or special devices for matching the asynchronous machines to one another can be avoided. This servo drive is particularly suitable for fast-reaction drives for individual shafts of numerically controlled, relatively high power machine tools. It can be used whenever mechanical coupling of the drives to one another is provided or whenever an exactly identical position is not required.

Description

The invention relates to a servo drive according to the Oberbe handle of claim 1. A drive with several Asyn chron machines, their speed and torques in all re gel areas are largely the same in some applications cases required to have a cheaper split of moments to achieve the load, a more favorable distribution of the To enable asynchronous machine arrangement or z. B. by doubling the prime movers a greater load to be able to regulate. For example, during a shoot bank or a sander can be beneficial to that torsion occurring during machining of the workpiece a distribution of the driving torque on both sides level the workpiece. This can cause torsion accuracies are reduced and / or deformation of the Workpiece can be prevented.

In other cases, especially with large prime movers, it may be advantageous to weight the prime mover by dividing it into several individual machines with one Ge weight distribution at different points in the system allocate or compensate. Under certain circumstances it can also be more economical to increase the number of services driving machines to increase.

For this purpose, it is known to form asynchronous machines in parallel and these from a common or separate converter tern to dine. Are these frequency-controlled?  Drive groups without speed control, such as. B. in pumps in the chemical industry or for drives with a white Chen work characteristic is the torque distribution on the individual drives mostly unproblematic. At high Dynamic servo drives are special measures required to si the desired torque distribution (see e.g. DE-OS 25 18 267 or DE-OS 24 26 532). It is known to do this as one of the drives To use the master who sets the position setpoints for the other An drives (slaves) and a complex superordinate Nete position control for an angular synchronous synchronism to care. Here it is not only important to have one To achieve precise torque distribution, it must also Torque vibrations, especially with sudden rotation torque changes, are avoided.

According to the invention, the task can be done without a parent ten control loop with the characteristic features of the contractor Solve saying 1 if the individual drive motors mecha nisch are coupled together and / or an exact angle synchronous synchronization is not required.

The inverters can be connected to different DC intermediate circuits are common or from one same DC link are operated. At spatial separation of the partial inverters can be due to the possibly high converter frequency may be beneficial that common control signals in each partial inverter by own driver circuits to amplify disturbing Interferences to the common control lines to ver avoid.

The generation of the control has proven to be particularly suitable signals according to the algorithm of the field-oriented control proved how z. B. in the application essay in time font "Regelstechnik" 32 year 1984 issue 1 on the Pages 18 to 26 is described. The servo according to the invention The drive is based on an embodiment  explained in more detail.

It shows

Fig. 1 shows a machining principle with a machine tool and

Fig. 2 shows a circuit principle according to the invention.

In Fig. 1, a workpiece 1 is clamped 2 and 3 directions at both ends in Spannein, each drive device of an on 4 and 5 are driven via separate asynchronous machines. The workpiece 1 is processed with a tool 6 . Especially with very elongated workpieces, e.g. B. a crankshaft, errors can arise in the machining process due to torsion or torsional vibrations of the workpiece if the drive or actuating forces attack, as usual, only on one side of the workpiece. This is largely avoided here in a manner known per se by a two-sided drive of the workpiece if the two asynchronous machines have the same torques in all turning and adjusting ranges.

For this purpose, the two asynchronous machines 10 and 11 are fed from a common DC voltage intermediate circuit 12 located on the three-phase network, which supplies the inverters 13 and 14, which are provided separately for each asynchronous machine, with DC voltage. To control the inverters 13 and 14, each provided with six driver stages, it generates the control signals for these driver stages in electronics 15 with the help of one or more microcomputers. The way of generating these control signals is known per se and can, for. B. the specialist book "Mikrocompu tergeregelte Asynchronmaschinen" by D. Dietrich / W. Konhäuser are taken from the R. Oldenbourg Verlag Munich Vienna 1986.

For this purpose, the electronics 15 is supplied with the setpoint value from a numerical control via an input line 16 and the control signals corresponding to the signals of a rotary position transmitter 18 supplied via a further line 17 as well as the phase current values supplied via the line 20 . The signals supplied to the driver stages via the lines 19 can be high-frequency pulses for pulse width modulation, the sinusoidal phase currents for the individual phase windings of the asynchronous machines 10 and 11 make it possible.

The individual control signals for the corresponding driver stages of the two inverters are each taken from an output stage in the electronics 15 , so that they are completely identical. The driver stages and output stages of the inverters are transistor switching stages which are controlled by pulses in very short switching times in two switching positions. As tests have shown, despite the separate power supply to the asynchronous machines 10 and 11 via ge separated inverters 13 and 14, a surprisingly exact torque distribution takes place without the need for special adjustment means to adapt these inverters to one another or to provide a superimposed equalization control.

To ensure that the torque distribution does not lead to malfunctions or damage in the event of a fault, it can be useful to record the phase currents of both asynchronous machines and to monitor these measured values. For this purpose, the measured value supplied to the electronics 15 via an additional line 21 can be fed to the second asynchronous machine of a comparison device, which delivers an error signal when a given difference value is exceeded.

Claims (6)

1. Highly dynamic electric servo drive with several multi-phase asynchronous machines, the speed and torque are largely the same in all control ranges, characterized in that the individual Asynchronmaschi NEN ( 10, 11 ) each of a self-commutated voltage intermediate circuit inverter ( 13, 14 ) via switching trans are fed and the corresponding switching transistors of the individual inverters ( 13, 14 ) are controlled with the same control signals ( 19 ). 2. Servo drive according to claim 1, characterized in that there is a mechanical coupling, for example via a shaft, tool ( 1 ) or a gear between the individual asynchronous machines ( 4, 5 ). 3. Servo drive according to one of claims 1 or 2, characterized in that the self-commutated inverters ( 13, 14 ) from a common DC voltage intermediate circuit ( 12 ) are fed with constant or variable intermediate circuit voltage. 4. Servo drive according to one of claims 1 to 3, characterized in that the generation of the control signals ( 19 ) for the individual inverters ( 13, 14 ) in a common for all inverters electronics stage ( 15 ) in particular for drive control and the control signals ( 19 ) from the electronics stage ( 15 ) driver stages are supplied, which are provided in the power stages in the individual inverters ( 13, 14 ) and serve to control the inverter valves. 5. Servo drive according to one of claims 1 to 4, characterized in that the asynchronous machines ( 10, 11 ) have the same structure, the control signals ( 19 ) for the inverter according to the algorithm of field-oriented regulation are created by a superordinate microcomputer and the Driver circuits for the inverters ( 13, 14 ) are supplied with pulse-width-modulated control signals which generate phase currents of the same amplitude and phase position in the phase windings of the asynchronous machines ( 10, 11 ). 6. Servo drive according to one of claims 1 to 5, characterized in that the phase currents of the individual Asyn chron machines ( 10, 11 ) are measured and a comparator are supplied which supplies an error signal when the difference in the phase currents exceeds a predetermined value .