SU1487144A1 - Method of determining position of moving element of stepping motor - Google Patents

Description

The invention relates to electrical engineering and can be used

in control systems with stepper motors (SRD), using information about the position of the moving element without the use of special sensors. The purpose of the invention is to improve the accuracy by increasing the resolution of determining the position of the moving element of the stepping

The invention relates to the control of electric machines and can be used in a precision discrete electric drive.

The purpose of the invention is to improve the accuracy by increasing the resolution of the position determination.

Figure 1 shows a two-phase stepper motor with a rotor containing a permanent magnet and a stator

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electric motor. The method is as follows. The emf signals of motion are extracted from 1! 1D orthogonal phase windings; they form a phase state signal of the resultant motion vector emf; they produce a reference electrical signal with a change frequency exceeding at least twice the maximum frequency of emf change of the result vector, they compare the signal the phase state of the resultant vector with the reference signal, at the moment of their equality, the position of the moving element is measured by the magnitude of the reference signal. At the same time signal O

the phase state of the resulting emf is obtained as the ratio of the amplitudes of its orthogonal components.

The method allows to increase the resolution of determining the position of a moving element, is applicable in a wide range of speeds of movement, is invariant to the engine design and type of movement. 5 il.

^: with control windings I, nd in FIG. 2 - EMF signals on orthogonal windings V ₁ and isolated from the total voltage acting on these windings; in fig. 3 - vector interpretation of the determination of the position of the resulting EMF of rotation; in fig. 4 - waveforms of signals; in fig. 5 is a block diagram of the device that implements the proposed method.

5C „„ 1487144 A1

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It is known that the signal EMF of rotation contains a fairly complete | information for recognizing the instantaneous values of the basic motion parameters of a stepper motor. The emf of rotation is a periodic function. Her., The period is equal to one tooth division. The shape of the signal is very close to sinusoidal. The amplitude of the signal is proportional to the speed of movement.

The task of extracting the EMF signal from the total voltage acting on the winding is solved in the device described in the patent prototype. For an engine (Fig. 1) with orthogonal windings H, and I ₂ and a permanent magnet on the rotor, the EMF of motion is equal (see Fig. 2)

£ ₁ = Ф ω з ίη Θ y

$

= f "c δπ (b +

where F is the flow in the magnetic core;

1l) - rotor speed.

On the phase plane instant

the values of these signals can be represented by the vectors £, and £ ₂ and their resulting vector ε (see Fig. 3).

If we additionally introduce a reference rotating vector E (</) with known current position parameters, the beginning of which coincides with the origin, and the end describes a circular hodograph of radius K, then the phase of the resulting EMF can be determined at the time of coincidence of the vectors £ and G in the direction related with the value of its parameter q fixed at the indicated moments of coincidence of the direction of the vectors.

If the speed, the rotation of the vector P is set n times higher than the speed of the Motion of the resulting EMF, then during the full rotation of the vector η matches will be fixed. The sampling values of the parameter ψ at the moments of coincidence will correspond to the n-discrete values of the position of the rotor on the pole division.

Introduction of the reference signal of known amplitude and phase allows determining the position of the moving element of the stepping motor, without resorting to non-linear transformation of the resulting emf signals to highlight the argument of the trigonometric function, i.e. angle Θ. It .

greatly simplifies the circuit design of the position signal conditioning unit. Since the frequency of the auxiliary vector can be unlimitedly higher than the frequency of the resulting EMF, the limitations on the number of information points of the position within the tine division are practically removed.

If the current position of the vector E is represented as a signal, the ratios of the components £ § θ = £ ^ / £ _g , and the current position of the vector P as Gd 1 / (see Fig.4), then at the moments of coincidence of the directions of the vectors £ and P we get (see .fig. 4 points. a, b ... e)

Eeb = (1)

those. Θ = I /.

The condition (1) allows determining the position of the resulting emf by means of a discrete sampling of the parameter q, at the indicated moments of coincidence.

The analysis shows that the ratio £ / £. <1 of the EMF components, reflecting the position of the vector £, does not depend on the speed of the rotor and the magnetic flux. This is the advantage of the method, which allows to maintain the stability of the recorded characteristics in the entire range of operating speeds of the electric drive.

The latter circumstance becomes especially important in linear stepper drives with aerostatic bearings, when the instability of the air gap between the armature and the inductor of a stepping motor leads to a change in the amplitude of the EMF signals.

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The stepping motor (11Щ) 1 is part of the open-ended structure of the electric drive 2, which also contains the power amplifiers 3 according to the number of phase windings of the motor and the distributor 4 pulses. The drive is controlled by external impulse commands of the frequency £ arriving at the input of the distributor. Through the synchronizer 5 from source 6.

The measuring part of the block diagram of the implementing device contains a block 7 of the formation of the reference signal with a known phase state, block 8 of forming the phase state signal of the resulting emf of motion, block 9 of comparing and generating a polling pulse of the memory register 10.

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Block 7 includes a clock-generator, a torus 11, a counter 12, a read-only memory (ROM) 13, a digital-to-analog converter (DAC) 14, ₅

. the controller 15 on the resistor level of the reference voltage and the _op converter 14.

Block 8 contains an analog divider 16 and a phase separation circuit 17 of the emf of motion.

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The output of the clock generator 11 is connected to the counting input of the counter 12, the output of the last discharge of the counter 12 is connected to one of the 15 inputs of the synchronizer 5, and the bit outputs of the counter 12 are connected to the bit inputs of the register 10, the outputs of which are the output of the device and are intended for output 20

"KID of the rotor position, as well as with the bitwise inputs of ROM 13, included in

^ a serial circuit with a DAC 14, the input of the reference voltage through a regulator 15 is connected to a 25 stable source of DC voltage, and the output to one of the inputs of a block 9 for comparing and generating a polling pulse · register 10 to which the output 30 of block 9 is connected, the second its input is to the output of the circuit 16 of the analog divider, the inputs of the dividend 18 and divider 19 of which are connected to the outputs of the block 17 of the phase separation of the emf of rotation, whose inputs are connected to the windings I ₁ and I of the motor.

In the initial state before. receipt of external control commands on the input of source 6 operates 40 parts of the device, which includes blocks 7.9 and 10. Counter 12 operates in the summation mode of pulse commands generated by the generator 11.

During the period of counting on the counter-by-meter outputs of the counter, the parallel code received 0

The value from 2 to 2 is consistently measured. Each number of this series at the input of ROM 13 corresponds to the value ςθ

 argument of the trigonometric function defined on the interval

0 - 21Г.

At the output of the ROM block 13, the parallel code takes the values of the function y = a and enters the block of the CPU 14

converted to. analog form. The magnitude of the scale factor is adjusted by setting the position

a movable contact of the resistor 15, i.e., a change in the reference · voltage of the DAC. From the output of block 14, the signal ϋ, ₄ (ν) is fed to one of the two inputs of block 9 of the comparison, and as a result of the comparison, a pulse command is sent to the polling bus of register 10.

Since the initial state is simultaneously characterized by the rest state of the moving element ’(ω = 0), the signal at the second input of block 9, obtained as a result of processing the emf of motion in block 8, is also zero. In this case, the pulse signal at the output of block 9 will be formed. at 0. The specified pulse is fed to the input “Polling” of register 10, which rewrites the number stored. being in the counter 12, in the memory cells of the register 10. In particular, for the state of rest this number is N = 2 °.

In working condition, the input of the source 6 of the electric drive control unit receives pulse commands with a frequency. In block 5, their phase state is corrected and they arrive at the input of the distributor 4, switching the windings 1ID through reversible amplifiers 3. The rotor makes the movement specified by the program. The motor windings produce an emf of movement. By means of circuits designed to extract EMF from the sum signal acting on the windings I and 1 VD, two signals are received

and £ ₂ = φί4 5Ϊη (θ + ^).

One of them is fed to the input 18 "Divisible", the other - to the input 19 "Divider" of the node 16 analog division.

Division result

= GS6c output of the divider 16 is fed to the second input of block 9 comparison. At the moments of time when ι / = Γβθ, which corresponds to the actual equality Ts = Θ, the output of block 9 produces a pulse, according to which the number currently stored in the digits of counter 12 is rewritten into memory register 10. This number corresponds to the position code of the rotor inside the main (constructive) pitch of the electric motor. ₍

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By the time of the formation of the new pe | During the period of the function, the rotor will change its position, which will affect the instantaneous amplitude ε ¹ (Θ) and $

^(θ) and their relationship. This fact is recorded as a result of the comparison, while block 9 generates a pulse at a new value of the reference signal Ρςΐ /, i.e. when I / ¹ = Ρ & Θ ¹ , which corresponds to the output of register 10 corresponding to. new position code.

The resolution of the method depends on the number of fixed values of the angle Θ during the two-rotor rotor within the pole division, i.e. within the range of 0 = 0 - 2 / ?. The calculation of η can be carried out in accordance with the expression 20

. ^with de ' ^£ t

where £ _t is the frequency of the clock generator, torus 12. 25

Thus, when applying this method, restrictions are imposed on the number of information reference points of a position in the step interval, thereby increasing the accuracy of motion control. The accuracy of determining the position does not depend on the amplitude of the components of the resulting EMF of rotation, but on their ratio. This gives an advantage when applying the proposed method in electric drives designed for operation in a wide range of speeds, and in a planar linear drive eliminates the additional dependence of the amplitude of the EMF components on the instability of the air gap between the armature and inductor.

The method is invariant to the design of the engine and type of movement. This is explained by the fact that stepper motors with orthogonal spatial arrangement of phases are produced by the industry in rotational, linear and planar designs designed for rotational, linear and linear views in the plane. movement; the selection of the position signal is carried out without the functional conversion of the source signal of the EMF. This eliminates the additional measurement error and simplifies the hardware of the device.

The method eliminates the need for special position feedback sensors, regardless of the design of the stepper motor and the functional purpose of the drive. This is especially important in linear planar two-axis drives, where the lack of position measurement tools is experienced.

Claims (1)

Claim The method of determining the position of the moving element of a stepper motor with orthogonal windings, which measure the emf of motion on two orthogonal windings, process the indicated emf using a comparison of two quantities and determine the position of the rotor according to the result of the comparison, about tl and tea that, in order to increase accuracy by increasing the resolving ability of determining the position, the process of processing the indicated emf of motion is carried out by calculating the phase state function from the values of these emfs rotor and setting the reference signal in the form of a similarly known periodic function, whose frequency is at least twice the maximum frequency of the emf of motion, and the function of the phase state of the rotor and the reference signal are used as compared values, determining the position of the moving element at the moment of their equality. 1487144 fi & a 1487144 5