DD239678A1 - METHOD AND ARRANGEMENT FOR MEASUREMENT SIGNAL EVALUATION IN PHASE CONTROLLED DRIVES - Google Patents

Abstract

The invention relates to a method and an arrangement for measuring signal evaluation in phase-locked drives which operate with phase-modulating measuring systems. The aim of the invention is to provide a method and an arrangement for its realization, which allows to set any number of rotor or Laeuferpositionen without a quantization error within a period of Massverkoerperung the measuring system, but also a movement with low constant speed and good Synchronous operation. Furthermore, the measurement signal processing should not result in any additional dead time in the position control loop. The object is achieved in that a reference signal and a measurement signal whose phase shift relative to the reference signal describes the course of motion, are fed to a phase detector whose output signal in the phase locked loop for position control serves as a control deviation for fine positioning. The phase of one of the two measuring signals is additionally shifted by an amount corresponding to a required fine position. With a controllable phase shifter, any desired position can thus also be set within a period of the graduated mass of the measuring system. To avoid period errors, phase jumps from 360 to 0 or 0 to 360 are numerically recorded and used for coarse control. If the control frequency for the controllable phase shifter is constant, a movement with constant speed and good synchronization occurs even at low speeds.

Description

For this 5 pages drawings,

Field of application of the invention

The invention relates to a method and an arrangement for the evaluation of phaserimodulierten measuring signals, which have arisen for example in an incremental measuring system, in controlled drives.

The invention can find application in controlled drives for positioning with high resolution and accuracy, as well as for the generation of constant speed, good tracking motions, especially at low speeds. '.

Characteristic of the known technical solutions

For incremental digital attitude control, various methods are known. Open-loop method, e.g. B. stepper drives, require only a small effort for digital signal processing. The disadvantage of these drives is the positional error occurring in counterforces or countermeasures. For stepper motors, there is also the risk of step losses if certain limit values are exceeded during acceleration or braking of the drive. Compared with low-inertia DC motors of comparable performance, stepmotors have larger mass moments of inertia and low efficiency.

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Regulated incremental drives do not have these disadvantages. For position detection, however, a measuring system is required, which significantly co-determines the achievable accuracy and resolution of the drive. , *

Known phase-modulating measuring systems work with a digital cyclic absolute evaluation. In Signer, A .: Removal with Inductosyn. Workshop and Operation 108 (1975) 8, pp. 507-513, DD-PS 142 p. 16, DE-PS 2837108 and Barth, W .; Gerstenberger, H .; Hercht, J .; Reichel, F .: Robot control IRS600. radio television elektronik 31 (1982) H.9, p.563-591 are various possibilities for phase-cyclic evaluation for the most well-known representatives of pbasenmodulierender measuring systems. Resolver and Inductosyn, shown. The evaluation of the phase-modulated measuring signals in photoelectric measuring systems is shown in DD-PS 128338, DE-AS 1303733 and DD-PS 206424.

It is common to all these methods that the phase shift describing the course of motion is counted with the pulses of a clock frequency fr for measured value interpolation. The achievable Irtterpolationsfaktorq is determined by the ratio of the clock frequency to the drive frequency fui for the phase-modulating measuring system. Because of the periodic counting of the phase shift, a certain counting time is necessary until the current measured value is available. This count time depends on the phase shift and the drive frequency f | For a phase shift of close to 3βΟ °, the count time reaches a value of almost Tm = J_ "

'. , ^f M '. '

Infoige of gate delays is until the start of the next counting cycle a recovery time of a period of the drive frequency necessary. The ailein caused by the Meßsignalauswertung dead time in the control loop of the drive can therefore reach 2T _M.

Limits are set to any reduction of T _M since the clock frequency f _T can not be selected arbitrarily large. With the standard TTL technique, f _T can be about 20MHz. With a required interpolation factor of q = 1000, the dead time can reach 0.1 ms. Γ

In the case of highly dynamic drives, the parameters given by the other elements of the drive can not be achieved due to the dead time caused by the measurement signal processing.

Another disadvantage is the quantization error resulting from the digital representation of the interpolated measured value. If, for example, a 10 000-fold step spacing of the scale period is to be achieved with an accuracy of 1%, an interpolation factor of q = 100000 must be achieved.

Compared to a 10OOfache step spacing without quantization error arises in the known Meßsignalauswertung a much greater effort. _x

The dead time resulting from the use of standard TTL technology for the interpolation factor q = 100000 is 10 ms and is therefore not acceptable for fast drives.

A further problem with drives is the production of very slow movements (eg 0.05 mm.s ^-1 ) with constant speed and good synchronization, whereby in regulated drives the provision of a speed-proportional actual signal of low ripple is of great importance For example, tachogenerators provide too low an output signal at low speeds, and high effort is required to achieve a sufficiently small ripple in the speed signal.

Object of the invention

It is therefore an object of the invention to overcome the said disadvantages and to provide a simple method and an arrangement which allow to set any number of positions within a scale period of the phase-modulating measuring system without a quantization error, but also a movement with low constant speed and good Enable synchronous operation. - -

Explanation of the essence of the invention

The invention is based on the object by a controlled drive whose measuring system delivers at least one phase-modulated measuring signal to set as many object positions without a quantization error even within a basic period of the measuring signals.

It should also be possible to move at a low constant speed. The positioning accuracy and the synchronization should be independent of amplitude fluctuations of the measuring signals.

Another object is to realize these requirements with little effort in the transducer.

The solution to this problem is achieved according to the invention with a method and an arrangement for Meßsignalauswertung in phase-locked drives, in which at least one reference signal and a signal whose phase shift relative to the reference signal describes the course of motion, are present.

The two measuring signals are fed to a phase detector, whose output signal is used in a phase locked loop for position control as a deviation for fine positioning, wherein the phase of one of the two measuring signals is additionally shifted by an amount corresponding to a required Feinpositipn. Phase deviations of the phase detector of the position control loop supplied signals of greater than 360 ° or less than 0 ° are ^> numerically detected and used for coarse control of the solenoid diode of the measured signals. Within the reference period, only the analog output voltage of the phase detector for position control is effective as control deviation.

The function of the output voltage of the phase detector as a function of the actual value χ is strictly linear. For κ - w = + -E-

is. , '. . ' '. ',

the assignment of the output voltage of the phase detector to the control deviation e = χ - w absolute. Outside this range, the coarse regulation begins.

The fine position within the desired period is specified with a controllable phase shifter. The zero crossing of the output voltage of the phase detector and thus the desired position within the desired period is thus determined by the phase shift, which preferably experiences the reference signal through the phase shifter. This means that many positions can be set without quantization errors within the nominal period of time.

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If a delay element is used whose transit time is adjustable continuously or in steps, the generation of the additional phase shift can be attributed to a time measurement which can be carried out relatively easily and with high accuracy by known technical means. The digitization of the measurement signals is advantageous because the adjustment of the additional phase shift is possible in a simple manner, for example with a monostable multivibrator.

The fine position is determined by the ratio of the holding time of the monostable multivibrator to the period of the measured signals. In this principle, however, the constancy of Meßsignalfrequenz and the holding time has influence on the Feinppsition. It is therefore proposed an arrangement according to the invention, in which the additional phase shift is generated by a digital circuit which is phase-locked coupled to the Meßsignalfrequenz. By this measure, changes in frequency of the measured signals can not affect the fine position. .

Low constant velocity, good tracking motion is achieved as the additional phase shift for fine positioning is continuously changed.

That is, the control function for the phase shifter is linear and can therefore be generated by simple technical means. The increase of this control function determines the size of the driving speed / To achieve a movement over several grid periods, a synchronization between the control function and the motor movement is necessary. That is, when the phase shift of the measurement signal whose phase shift relative to a reference signal describes the course of motion, jumps from the reference signal of 360 ° to 0 °, the generator for the linear 'control function is triggered again. The synchronizing signal can be obtained, for example, by differentiating the output signal of an additional phase detector. This phase detector detects the phase shift between the reference signal of the measuring system and the measuring signal whose phase shift describes the course of the movement. The invention can be used in all controlled drives whose measuring systems at least a reference signal and a phase-modulated signal whose phase shift relative to the reference signal describes the course of motion deliver.

Such measuring signals can be generated with inductive, magnetic, capacitive, photoelectric or interference sensors. ' ^k ·, ^ <:.

embodiment

The Erfindungsoll be explained in more detail with reference to the following in the drawing schematically illustrated embodiments. Show it: ' , -

Fig. 1: A schematic representation of an inventive arrangement for obtaining the control deviation for

Fine positioning. '·' ... '. ..

Fig. 2: A schematic representation of an inventive arrangement for generating the additional

Phase shift with a phase-locked logic

 Fig. 3: A schematic representation of an arrangement according to the invention for generating the additional

Phase shift with another phase locked loop. .

Fig. 4: A schematic representation of an arrangement for fine positioning in a microcomputer controlled drive. Fig. 5: A schematic representation of an arrangement for generating a movement at a constant speed and

good synchronization. ,

In Fig. 1, an arrangement for obtaining the control deviation for the fine positioning in drives with phase-modulating measuring systems is shown. For this purpose, in a sine-cosine generator 1 the Ansteuersignaleu! and u _? generated for the phase modulating measuring system 2. The output voltage u _{3 of} the measuring system 2 has an actual quantity χ proportional phase shift α with respect to the reference voltage Ui. With the controllable phase shifter 4, the phase of the reference voltage Ui is shifted in dependence on the Führüngsgrößew by an additional phase angle β. The phase detector 3, whose output signal serves as a fine control voltage or control deviation for the position control loop, the measuring system voltage U ₃ and the phase-shifted by the phase angle β voltage u _{4 are} supplied. The zero crossing of the fine control voltage and thus the target fine position can now be placed with the help of the reference variable w at any point within the desired period ps. Depending on the phase detector used, the fine regulation voltage is unambiguous and linear in a range of at least + y about its zero crossing. If the control deviation exceeds this range, the coarse control starts and guides the rotor so that the unique range of the fine control voltage is reached again. As a switching criterion for the coarse control are the steep edges of the fine control voltage at the boundaries of the unique area. '.

An arrangement for generating the additional phase shift with a phase-locked logic is shown in FIG. A clock generator 5 drives the digital sine-cosine generator 6, which at the same time performs a frequency division of the clock frequency fx to the Meßsignalf frequency f _M. The output voltage U _{3 of} the measuring system is digitized with a comparator 8 and fed to the digital phase detector 9. The reference voltage Ui is digitized with the comparator 7 and is available as a digital reference signal Ui d for further processing. The programmable counter 16 operates as a divider, which generates from the clock frequency for the reference voltage U40 with the frequency ί &, and an additional phase shift. The phase angle β is determined by the reference value for the fine position Wfein. '

The phase of the programmable counter 16, which is phase-shifted by the phase angle relative to the reference signal U ₁ , is achieved by setting the programmable counter 16 at the start of the period of the reference signal u to the count value predetermined by the reference variable Wpoin. The phase angle is independent in this arrangement of frequency fluctuations of the clock frequency fr.

For the necessary toughening of the programmable counter poison at a required interpolation factor q:

In the phase detector 9, the phase position of the voltage u ₃ o is determined with respect to the reference voltage u _4D The analog output of this phase detector is used as Feinsrsspannungsspannungein. The phase detector 9 includes a periodic logic that generates at phase jumps from 0 ° to 360 ° and 360 ° to 0 ° forward and backward counts ZV and ZR for the period counter 10. With the digital subtracting 11, the control deviation for the coarse positioning is obtained from the numerical actual value for the coarse position Nx and the coarse setpoint w _GrO b, which acts on the analog position controller via the DA converter 12 and the adder 14. The comparator 15 switches over the electronic switch 13, the Feinregelspanung when the target period is reached. Thus, no quantization error occurs. To suppress the frequency of the output signal from the DA converter 12, the electronic switch 13 and the comparator 15 can be omitted, whereby a constant summation of the coarse and fine control voltage takes place. _t ,

3 shows the representation of an arrangement according to the invention for generating the additional phase shift β with a further phase-locked loop. The drive signals Ui and U2 for the measuring system 13 have the frequency f _M and are generated by a generator 18. The additional phase-locked loop, consisting of the divider 23, the phase detector 24, the Schleifönfilter 25 and the voltage-controlled oscillator 26 generates the phase-locked to the digitized reference voltage coupled clock signal Ut with the frequency fj. From the clock signal, the reference signal u ₄ o for the phase modulator 21 is obtained with the divider 27. The frequency of the reference signal u _4D corresponds to the generator frequency f _M. By the reference variable wpein, the additional phase shift of the reference signal u _4D relative to the reference voltage U ₁ , and thus the fine position, is determined. 1

For the division factor of the dividers 23 and 27, N or the interpolation factor, the following applies:

Due to the phaseristarren coupling of the reference signal u ₄ q with the reference voltage Ui frequency changes of the generator 18 have no effect on the positioning accuracy.

4 shows the schematic representation of an arrangement for fine positioning in a microcomputer-controlled drive.

A generator 33 generates the drive voltages U ₁ and U ₂ for the phase-modulating measuring system 32. The reference

used voltage U ₁ is digitized with the comparator 34. ,

With the monostable multivibrator 35 used as a delay element, an additional phase shift of the reference signal u _4D with respect to the reference voltage U _{1 is} achieved. The additional phase shift and thus the fine position is predetermined by the microcomputer 40 with the control word DF via the DA converter 36 as the control voltage u _st for the monostable multivibrator 35.

From the digitized phase-modulated measurement signal u _{3 [} j and the reference signal u _4D , the analog fine-control voltage Upein is obtained in the phase detector 38. With the periodic logic contained in the phase detector 38, the period counting pulses ZV and ZR are generated for the coarse regulation to the reference period in the case of phase jumps from 360 ° to 0 ° or from '0 ° to 360 °. The period counting pulses ZV and ZR are evaluated in the microcomputer 40, which operates as a digital controller. The manipulated variable for coarse regulation is output to the power amplifier 30 with the control word DG via the DA converter 28 and the summing point 29.

is reached the target period, the microcomputer 40 with the electronic switch 39 activates the fine control. The manipulated variable of the fine regulator 41 is also supplied via the summing point 29 to the power amplifier 30, which drives the motor 31.

A constant-speed movement occurs when the microcomputer 40 continuously changes the control word DF in small steps.

Fig. 5 shows the schematic representation of an arrangement for generating a movement with a constant driving speed and good synchronization.

The generator 41 generates the drive voltages Ui and U ₂ for the phase-modulating measuring system 42. The phase detector 43 whose output voltage serves as a fine control voltage Uran compares the phase of the phase-modulated output voltage U _{3 of} the measuring system with the reference signal U _4th With the phase shifter 44, the phase of the reference voltage U ₁ for obtaining the reference signal U _{4 can be moved} continuously. The control of the phase shifter is done with the control voltage ust, wherein the relationship between the control voltage u _S t and the size of the phase shift by the phase shifter 44 is linear.

The control voltage generator 44 generates a linear function whose rise is determined by the reference variable w, for the specification of the desired speed. After the movement around a period of the material measure, the control voltage generator 46 must be re-triggered or synchronized. The synchronization must always take place when the phase shift between the reference voltage Ui and the measuring signal U ₃ jumps from 360 ° to 0 ° or from 0 ° to 360 °. The synchronization signals Sync are obtained with the period logic of the phase detector 45. The synchronization always takes place at the right time because the measurement signal U _{3 is} used directly as a criterion for triggering a synchronizing pulse.

To monitor the synchronization and the absolute value of the speed, the analog output signal of the phase detector 45 is used. After the differentiator 47, a voltage proportional to the actual speed of movement is obtained.

This voltage is compared in the comparator 48 with the command variable w for the speed. According to the

Requested speed constancy or the required synchronism are the comparator when überüberunge.n

predetermined tolerances of an error signal FS. ,

Claims (12)

1. A method for Meßsignalauswertung in phase-locked drives, in which at least one reference signal and a signal whose phase shift relative to the reference signal describes the course of movement, are present, characterized in that both signals are fed to a phase detector, whose output signal in the phase locked loop for position control as a control deviation Fine positioning is used, wherein the phase of one of the two measuring signals is additionally shifted by an amount corresponding to a required fine position. ,. ' 2. Method according to item 1, characterized in that phase deviations of the phase detector of the Lageregelkreisss supplied signals of greater than 360 ° or less than 0 ° numerically detected and used for coarse control. 3. The method according to points 1 and 2, characterized in that for a movement at a constant traveling speed of the phase setpoint for the phase locked loop for position control according to the required speed 'is changed continuously. 4. Arrangement for Meßsignalauswertung in phase-controlled drives according to points 1 to 3, characterized in that for generating the additional phase shift, preferably the reference signal, at least one controllable phase shifter is present. · ..-. - 5. Arrangement according to item 4, characterized in that at least one delay element whose delay time is adjustable continuously or in steps, is present. , 6. Arrangement for Meßsignalauswertung in phase-controlled drives according to item 4, characterized in that a digital phase detector is provided to which a first measurement signal is supplied directly and a second measurement signal with an additional phase shift, wherein the digital phase detector provides an analog output signal. 7. Arrangement according to points 4 to 6, characterized in that for obtaining the reference signal for the phase detector of the position control loop, a frequency divider whose divider factor corresponds to the interpolation q , is provided which shares a basic clock with the q-times the frequency of the drive signals of the measuring system wherein the frequency divider rotates with respect to the drive frequency of the measurement system mrt an adjustable phase offset corresponding to a required fine position, 8. Arrangement according to the points 4 to 7, characterized in that for generating the drive signals for the phase-modulating measuring system, a digital sine-cosine generator is provided, which is driven by the basic clock. , 9. Arrangement according to points 4 to 7, characterized in that a frequency divider is provided with a divider factor q whose output pulses synchronize an analog sine-cosine generator for obtaining the necessary drive signals for the phase-modulating measuring system. ", 10. Arrangement according to the items 4 and 5, characterized in that is obtained with an additional phase locked loop, which is synchronized to a measuring signal, the reference signal, with a fine position corresponding phase shift, for the phase detector of the position control loop. ^; ', 11. Arrangement according to the points 4 to 10, characterized in that at least one additional phase detector is provided in a movement at constant speed for controlling the cyclic synchronization to which the reference signal of the measuring system without additional phase shift and the measurement signal whose phase shift describes the course of movement, is supplied. 12. Arrangement according to the points 4 to 11, characterized in that a programmable logic is provided for setting the desired phase position of the phase locked loop for position control.