DE10040385A1 - Rotation speed detector for servo drive control of synchronous motor, includes speed sensor and position sensing resolver integrated into non-magnetic rotor arranged in stator without magnetic yoke - Google Patents

Abstract

A speed sensor (2) and a position sensing resolver (15) are integrated into a non-magnetic rotor (4) that is supported within a stator without a magnetic yoke. The resolver detects the eddy current flow in measurement coils (24-27), due to the excitation of the stator coils (6-9). The detection result is digitized to determine the position and differentiated to determine rotational speed.

Description

The invention relates to a rotary motion detection device with one turn number sensor from at least one immovable stator and one relative to this rotatable, non-magnetic rotor, excitation windings and measuring on the stator Windings are arranged, which excitation windings to generate a magne table flow in a gap formed between the stator and rotor with a chip Power supply are connected, and which measuring windings with an evaluation circuit for determining a rotational speed based on one of im Rotor-induced eddy currents in the measuring windings induced voltage ver are bound.

It is known from practice, in particular, for highly dynamic servo drives Use high-resolution angle encoders to record position and speed. The The position is determined directly by the angle encoder and the speed by differentiating the Position values determined.

Such angle encoders often have linearity errors when determining the speed lead to corresponding errors. As a rule, the higher the error, the greater the error is the speed of the corresponding drive. In this context, determined speed used for speed control of the drive result on due to the incorrect determination of the speed fluctuations in the motor current and corresponding to fluctuations in the synchronism of the drive, the fluctuations of the motor current can lead to increased heating of the motor.

Various such angle encoders are known in practice, such as Resolver, incremental encoder or the like. Such a resolver is usually a robust and inexpensive component, but shows only limited accuracy the position and according to the speed determination.

For higher demands on the accuracy of position and speed detection optical incremental encoders with high-resolution analog outputs are used puts. Although these show a relatively high accuracy, they are only for lower ones  Speeds and can be used for a limited temperature range and also relative expensive.

From the German patent DE-PS 1 064 739 is a tachometer generator as Rotary motion detection device known, the closest state of the Technology forms. In this tachometer generator, the corresponding speed sensor at least one stator and a rotor. The stator carries at least that Excitation windings and, if necessary, measuring windings. Flows through the pathogens windings by applying a corresponding voltage by means of a voltage supplying a current, there is a magnetic flux in a gap between the stator and rotor generated. At least when the rotor rotates relative to the stator by corresponding changes in the magnetic flux in the rotor over time Tensions are induced and corresponding eddy currents are generated. The eddy currents themselves generate corresponding magnetic fields and an associated magnetic Flow that passes through the measuring windings when the rotor rotates and in them induced a voltage. Due to the induced voltage is by means of an off the switching speed of the rotor can be determined.

In one embodiment of the tachometer generator according to DE-PS 1 064 739 the excitation and measuring windings are both arranged on a stator, which in a be cher-shaped rotor is inserted.

The disadvantage of the prior art is that a separate layer tion for the cup-shaped rotor is necessary and this right in its manufacture is relatively complex. A simple bearing of the rotor directly on a shaft, the Speed should not be determined. Another disadvantage is that always Magnetic inference is necessary, which causes the build-up of the rotary motion supply detection device and in particular the speed sensor complex and becomes expensive. In addition, the magnetic yoke leads to a large electrical time constant of the system, so that the measurement is fastest changes with a high bandwidth, such as in the field of servo drive technology is required is not possible. In this context, it should also be noted that the cup-shaped rotor in a gap between the inner stator and the outer  magnetic inference is rotated, so high demands on the precision must be placed on the gap and the rotor.

The object of the application is therefore based on the object of improving an object 7 of the type mentioned at the outset in such a way that an easily constructed, inexpensive to produce and robust speed sensor that can be used for high speeds is made possible, which due to its high bandwidth also for highly dynamic applications in servo drive technology is suitable, the concentricity, for example, of a servo drive compared to those with conventional encoders, such as resolvers or incremental encoders, is significantly improved.

This task is carried out in connection with the features of the preamble of Pa Tent claim 1 solved in that the rotor magnetically without inference within arranged of the stator and is cylindrical or annular.

The rotor can be part of a shaft, the speed of which is to be determined, or can be attached to the shaft as a ring. The positioning of the rotor relative to the Wave is therefore variable and possible depending on requirements. Since with the fiction according to the arrangement and design of the rotor ent a magnetic return falls, there is only a gap between the stator and rotor, and an arrangement of the Total rotor in a gap between the stator and magnetic yoke with The manufacturing difficulties that arise in this context are no longer necessary.

In order to avoid that in the measuring windings even without rotating the rotor Already an electrical voltage is induced, measuring windings and exciters windings may be arranged offset by 90 ° to one another on the stator.

So that the rotary motion detection device according to the invention also for high Speeds can be used and has a relatively high measuring accuracy the excitation winding through the voltage supply an alternating voltage high Frequency can be applied. The exciter and measuring windings can be connected in series to be switched to all excitation windings simultaneously and a same magnetic  Generate flux and accordingly simultaneously in all measuring windings to induce corresponding voltage values.

To prevent induction in the measuring windings through the stator the excitation windings take place, the stator can be laminated or in ferrite or iron powder be executed material.

The rotor is made of a non-magnetic material and should have good electrical conductivity his. Examples of suitable rotor materials are copper, aluminum, brass and also constantan / manganine.

To get information from the AC voltage induced in the field windings easy to obtain via the direction of rotation of the rotor relative to the stator, can the evaluation circuit a phase sensitive rectifier, in particular Synchronous rectifier. Through this rectifier, the AC voltage demodulated and you get a DC voltage, the sign of each egg correspond to the direction of rotation of the rotor.

Not only the speed by means of the rotary motion detection according to the invention Being able to measure and monitor the device can measure movement solution device have a position sensor. Such position sensors were already mentioned at the beginning, such as incremental encoders or six-step encoders, the latter is realized by appropriate Hall elements.

To be robust and usually sufficient for position determination To get a precise position sensor, a resolver can be used, for example the.

To the corresponding signals from position sensor and speed sensor computeri To be able to evaluate, the evaluation circuit A / D converter for digitization tion of the signals from the position and / or speed sensor. Usually there a resolver two analog and the speed sensor according to the invention an analog Signal off. That means, with three A / D converters, all signals from the sensors and each can also be digitized in high resolution if required.  

To ei in addition to the speed information of the speed sensor according to the invention To obtain a comparison value for the speed, the evaluation circuit can Have differentiating device and a speed comparison device. By means of the water two devices on the one hand, the position signal of the position sensor differentiated and then the speed signal obtained by the differentiation from the position sensor with the corresponding speed signal from the speed sensor compared.

This can serve, for example, offset, gain, linearity errors or the like to determine in one of the measurements and possible temperature drift compensate for a sensor.

Such compensation can advantageously take place in that the evaluators teschaltung for example connected to the speed comparison device Deviation correction device. This corrects the speed value and the corrected value as the actual speed value of a possible further processing fed.

Finds the speed determination according to the invention for example in a syn chronomotor or another electrical machine instead, the evaluation scarf device with a speed control circuit, in particular a servo drive controller for the electrical machine must be connected. In addition to the position value, the corrected actual speed value for speed / speed control and the posi Titons control can be used.

To detect faults in the sensor and in the signal path from the sensor to the evaluation circuit and the evaluation circuit can thus eliminate corresponding errors in the signal Have filters.

To a total of a mechanically and electronically simple structure of the Invention according to the rotary motion detection device, position sensor and speed sensor can be integrated in one component. For example, a resolver used as a position sensor is a common AC voltage for supply  of position sensor and speed sensor sufficient. The component is overall only little larger than the resolver itself and the evaluation of the speed signal from Speed sensor according to the invention can also from the already existing value electronics can be taken over directly or with minimal additional effort. The component can also be used as a retrofit kit, for example Measure position and speed on certain devices that have a rotating Have components such as welding robots, pumps, mills, screwdrivers or the like chen.

The two sensors also provide redundant monitoring at least the speed, as z. B. for monitoring a creep speed in In industrial robots is required.

It is of course also possible that the speed sensor according to the invention in Drives with conventional Hall sensors for commutation (six-step encoder) is combined. A simple evaluation electronics is already available on one Integrated circuit board for the Hall sensors. In conjunction with one accordingly Microprocessor-controlled control unit is an inexpensive, dynamically high-quality and possibly sinus commutated drive possible.

It is also possible to integrate a position information from the speed signal by integration mation to win. This is especially for short-term relative path measurements sufficient, for example, to record the angle in compressed air pulse screwdrivers perform. The angle detection can take place during the short pulses.

In order to obtain a ripple resulting from a pole frequency of the speed sensor To largely compensate for the signal, the stator can consist of at least two parts be formed, the corresponding stator halves in particular electrically other interconnected and staggered. The transfer to each other in this context, this can be a pole pitch in particular.

In order to be able to do without synchronous rectification if necessary and despite which a signal evaluation with field orientation, determination of a slip speed or  To get the same, two excitation windings can be offset by 90 ° be arranged corresponding to two measuring windings.

In the following, advantageous exemplary embodiments of the invention are described with reference to FIG Drawings accompanying figures explained.

Show it:

Fig. 1 is a schematic representation of a first embodiment of a rotary motion detection device according to the invention;

FIG. 2 shows a section along the line II-II from FIG. 3 through a speed sensor with an 8-pole stator, for example;

Fig. 3 is a plan view of a stator of a speed sensor of Figure 2 from a inner side.

Fig. 4 course of the current density in the rotor and the flux density in the air gap over two pole pitches of the stator, at zero speed and rotor at rest;

FIG. 5 measurement signals analogous to FIG. 4 for a rotating rotor;

Fig. 6 shows an application example for the rotary movement detection device according to the invention in a servo motor;

Fig. 7 is a schematic diagram of an evaluation circuit for the speed sensor; and

Fig. 8 is a schematic diagram for signal evaluation of the position sensor and speed sensor.

In Fig. 1 a basic representation of a rotational movement detection device 1 according to the invention is shown. This has a speed sensor 2 and a resolver 15 as a position sensor 14 . Both sensors can be integrated in one component with associated evaluation electronics or circuitry.

Both sensors 4 , 5 are assigned to a rotating shaft 29 and have at least one component rotating with this shaft.

In the speed sensor 2 , a rotor 4 rotates together with the shaft 29 and in the resolver 15 at least one winding rotates together with the shaft 29 .

The rotor 4 is an outer stator 3 assigned, see Fig. 2, in which the rotor 4 rotates, wherein between the two a gap 10 is formed.

On an inside of the stator 3 , excitation windings, 6, 7, 8, 9 and Messwicklun gene 24 , 25 , 26 , 27 are arranged, which are summarized in Fig. 1 for simplification.

Both the resolver 15 and the excitation windings 6 , 7 , 8 , 9 receive a correspondingly high-frequency alternating voltage from a voltage supply 11 , through which a magnetic field or a magnetic flux is generated in the gap 10 in the speed sensor 2 .

Due to the magnetic flux changing according to the alternating voltage and additionally by rotating the rotor 4 in the direction of movement 5 , eddy currents are generated in the rotor 4 , the size of which is essentially determined by the excitation frequency, the geometric dimensions and the specific resistance of the rotor material.

The eddy currents generate a magnetic field opposite the magnetic field generated by the field windings and a corresponding magnetic flux in the air gap 10 . This in turn passes through the measuring windings 24 , 25 , 26 , 27 and induces a voltage in these windings. This voltage signal is evaluated, see for example FIGS. 6 and 7, and contains information about the direction of rotation and speed of the rotor 4 .

FIG. 2 shows a section along the line II-II from FIG. 3. The section runs perpendicular to the shaft 29 , on which, for example, an annular rotor 4 can be attached.

The rotor 4 is centered on the shaft in order to keep a ripple with pole frequency small and, like the stator 3, is designed such that the gap 10 has a constant gap width both in the circumferential direction and in the longitudinal direction of the rotor 4 .

The stator 3 is designed as a hollow cylinder and has on its inside in the longitudinal direction grooves, in which the windings 6 , 7 , 8 , 9 and 24 , 25 , 26 , 27 are arranged. In each case an excitation winding 6 , 7 , 8 , 9 is arranged overlapping with a measuring winding 24 , 25 , 26 , 27 , each of these pairs of windings being electrically offset from one another by 90 °.

In Fig. 3 is a view of the inside of the stator 3 is shown in a simplified manner. In particular two mutually overlapping windings are visible, of which one winding is an excitation winding 6 and the other winding is a measuring winding 24 . The other windings according to FIG. 2 are arranged in an analogous manner, with all excitation windings and all measuring windings being connected in series.

FIG. 4 shows a measurement diagram of the current density 31 in the rotor 4 and of the flux density 30 in the air gap 10 , the rotor not rotating relative to the stator.

This representation corresponds to a stationary motor or a non-rotating shaft, the resulting field being zero due to eddy currents in the rotor in the measuring windings, since the field generated by the eddy currents in one geometric half of the measuring winding 24 with the corresponding field in the complementary half compensated. Therefore, no voltage is induced in the corresponding measuring winding.

If the rotor rotates, see FIG. 5, the air gap field shifts spatially due to additional eddy currents in the rotor, the field strengthening in a geometric half of the corresponding measuring winding and weakening in the complementary half. As a result, the fields no longer cancel each other out and there is a voltage in the measuring winding 24 which, depending on the direction of rotation of the rotor, is in phase or in phase opposition to the corresponding excitation voltage in the excitation winding.

In connection with FIGS. 4 and 5, it is pointed out that the rotor and stator can also be constructed linearly, ie that the rotor is, for example, an aluminum rail and moves along a straight stator, see FIGS. 4 and 5. In such a way, the detection device according to the invention can be used, for example, in linear motors that require a very fine resolution of actual speed values.

In Fig. 6, another application example for a rotary motion detection device 1 according to the invention is shown. It is a measuring arrangement for checking the concentricity of servo drives. The speed sensor 2 is on one side of an electrical machine, such as a synchronous motor 28 , on a shaft 29 driven by this and the resolver 15 as a position sensor 14 on the other side of the synchronous motor 28 is also arranged on the shaft 29 . Corresponding parts of the two sensors rotate with the shaft and signals relating to the speed and position of the shaft are recorded.

The signals of the speed sensor 2 are evaluated in an evaluation circuit 12 , which outputs an actual speed 46 . Via a speed control circuit 22 for the synchronous motor 28 , the transmission of a corresponding supply voltage 45 to the evaluation circuit 12 and to the corresponding windings of the speed sensor 2 takes place at the same time.

The resolver 15 transmits corresponding position data to the speed control circuit 22 , which can output actual values 43 , 44 for speed and position to the outside. In addition, the speed control circuit 22 can receive a target value 42 for the speed from the outside.

At this point it should be noted that the actual speed value 43 which is output to the outside by the speed control circuit 22 is a speed value determined by differentiating the position values measured by the resolver 15 , the speed value 46 of the evaluation circuit 12 or a speed corrected from these two speeds. Actual value can be.

In Fig. 7, a simplified embodiment for an evaluation circuit 12 is shown.

A high-frequency voltage signal is transmitted from a voltage supply 11 to the excitation windings 6 , 7 , 8 , 9 , possibly via a power amplifier 39 . At the same time, the voltage signal is transmitted to phase-sensitive rectifiers, such as in synchronous rectifiers or synchronous demodulators 13 . The power amplifier signal is also transmitted from amplifier 39 to a synchronous demodulator 13 . The voltage signal of the measuring windings 24 , 25 , 26 , 27 is first amplified in a preamplifier 40 and then rectified in the synchronous demodulator 13 . The corresponding signals in the synchronous demodulators 13 can be filtered by appropriate filters 23 and then transmitted to an output amplifier 41 . There follows a signal scaling, possibly further filtering by filter 23 and finally an output of a voltage signal which corresponds to an actual speed 46 of the rotor 4 .

In the speed sensor according to the invention there is a linearity error of a speed Characteristic curve relatively low and a dynamic behavior of the speed sensor shows in A clear comparison to the resolver despite filtering in the synchronous rectifier Phase Gain. Furthermore, the resolution of the actual speed is much higher than at a resolver and a noise superimposed on the actual speed is extremely low and can be suppressed by digital signal acquisition.

In FIG. 8 is a simplified signal evaluation of wheel speed sensors 2 and positi onssensor is 14 illustrates by means of a speed control circuit 22 for a servomotor Darge. Input signals of the speed control circuit 22 are, for example, sin signals 33 and cos signals 34 from the resolver 15 , see FIG. 6, and the voltage signal of the measuring windings 24 , 25 , 26 , 27 of the speed sensor 2 or alternatively the already processed rotation signal 46 of the speed sensor 2 or the evaluation circuit 12 .

For further computerized processing of these values or signals, these are digitized in A / D converters 16 , 17 , 18 . Subsequently, the resolver signals 33 , 34 are used to determine a corresponding position, for example of the rotating shaft 29 , see FIG. 6, in an angle detection device 35 and a speed value is determined from the position value in a differentiating device 19 . A corresponding position value 36 can be output to the outside by the speed control circuit 22 for position control, commutation or the like. Furthermore, there is the possibility that the speed 37 determined from the position value 36 is also output to the outside for regulating the speed or is fed to a speed comparison device 20 and a deviation correction device 21 together with the position value 36 and the digitized speed 32 .

By means of the speed comparison device 20 , the two speeds determined in different ways are compared with one another and serve to compensate, for example, offset errors, temperature drifts, gain drifts or the like when measuring one of the speeds. A correspondingly corrected speed value is determined in the deviation correction device 21 and output to the outside as a corrected speed 37 . In particular, this corrected speed value 38 can be used for speed control of the synchronous motor 28 , see FIG. 6, who the.

According to the invention, a rotational movement detection device thus results in particular a speed sensor that can also be used at very high speeds is that is robust and very simple in mechanical construction and in large numbers len is inexpensive to manufacture. The speed is determined by the rotation according to the invention number sensor directly recorded and a detection of the speed via the detour of the Diffe No need to differentiate position values. So the speed resolution is no longer dependent on a sampling frequency of the control, but only on the resolution downstream electronics for signal evaluation.

The higher the polarity of the stator, the lower the ripple of the measurement signals, d. H. the speed and the lower the demands on the rotor or the better the synchronization. According to the speed sensor can also a position sensor can be combined in a simple manner. Will the measurement signals  the position sensor also differentiated, so you get a redundant Ü Monitoring the speed.

Claims (16)

1. Rotary motion detection device ( 1 ) with a speed sensor ( 2 ) from at least one unmoving stator ( 3 ) and a rotatable relative to this tor tor ( 4 ), with the stator ( 3 ) excitation windings ( 6 , 7 , 8 , 9 ) and Measuring windings ( 24 , 25 , 26 , 27 ) are arranged, which excitation windings ( 6 , 7 , 8 , 9 ) for generating a magnetic flux in a gap ( 10 ) formed between stator ( 3 ) and rotor ( 4 ) with a voltage supply ( 11 ) and which measuring windings ( 24 , 25 , 26 , 27 ) are connected to an evaluation circuit ( 12 ) for determining the speed on the basis of eddy currents flowing in the rotor ( 4 ) in the measuring windings ( 24 , 25 , 26 , 27 ) Induced voltage are connected, characterized in that the non-magnetic rotor ( 4 ) is arranged magnetically without a back yoke within the stator ( 3 ) and is cylindrical or annular. 2. Rotary motion detection device according to claim 1, characterized in that excitation windings ( 6 , 7 , 8 , 9 ) and measuring windings ( 24 , 25 , 26 , 27 ) are each arranged electrically offset by 90 ° to one another on the stator ( 3 ). 3. Rotational motion detection device according to claim 1 or 2, characterized in that an AC voltage of high frequency can be applied to the excitation winding ( 6 , 7 , 8 , 9 ) by the voltage supply ( 11 ). 4. The rotational movement detection device according to at least one of the preceding claims, characterized in that the stator ( 3 ) is made of sheet metal or is made of ferrite or iron powder material. 5. Rotational motion detection device according to at least one of the preceding claims, characterized in that the rotor ( 4 ) made of copper, aluminum, brass, constantan / manganine or other electrically highly conductive materials. 6. Rotary motion detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) has a phase-sensitive rectifier ( 13 ), in particular a synchronous rectifier. 7. The rotational movement detection device according to at least one of the preceding claims, characterized in that the rotational movement detection device ( 1 ) has a position sensor ( 14 ). 8. The rotational movement detection device according to at least one of the preceding claims, characterized in that the position sensor ( 14 ) is a re solver ( 15 ). 9. Rotary motion detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) has A / D converter ( 16 , 17 , 18 ) for digitizing the signals from the position sensor ( 14 ) and / or speed sensor ( 2 ). 10. Rotational motion detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) has a differentiating device ( 19 ) and a speed comparison device ( 20 ). 11. The rotational movement detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) has a deviation correction device ( 21 ) connected to the speed comparison device ( 20 ). 12. Rotational motion detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) is connected to a speed control circuit ( 22 ), in particular a servo drive controller for an electrical machine, with position sensor ( 14 ) and speed sensor ( 2 ) corresponding to one Shaft of the machine are assigned. 13. Rotary motion detection device according to at least one of the preceding claims, characterized in that the evaluation circuit ( 12 ) has filters ( 23 ) for reducing ripples in the signals of the speed sensor ( 2 ). 14. Rotational motion detection device according to at least one of the preceding claims, characterized in that the speed sensor ( 2 ) and position sensor ( 14 ) are integrated in one component. 15. Rotational motion detection device according to at least one of the preceding claims, characterized in that the stator ( 3 ) is formed at least in two parts, the corresponding stator halves, in particular electrically connected to one another and offset from one another. 16. Rotary motion detection device according to at least one of the preceding claims, characterized in that two excitation windings ( 6 , 7 , 8 , 9 ) are each offset by 90 ° to two measuring windings ( 24 , 25 , 26 , 27 ).