RU2659468C1 - Following sine and cosine angle-to-code converter - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to the field of measurement technology, in particular to sine-cosine angle converters to code. Tracking sine-cosine angle converter into the code containing the first multiplier for multiplying the input voltage of the sine signal by the digital cosine value of the output code, the second multiplier for multiplying the input voltage of the cosine signal by the digital value of the sine of the output code, the subtractor whose inputs are connected to the outputs of the multipliers, and the output is with a voltage controlled oscillator, a VCO that generates signals for incrementing and decrementing the reverse counter, depending on the sign and the magnitude of the error, the outputs of the forward and reverse counting of the VCO are connected to the reverse counter of the output code of the angle, the output of the counter is connected to a read-only memory, ROM, sine and cosine values, is characterized in that the reverse counter is divided into two parts – the high and low, the high-end part is connected to the ROM of the sine and cosine values, and the younger one is connected to the inputs of the linear interpolation blocks of the table sine and cosine values for the least significant bits of the reverse counter that are also connected to the outputs of the ROM, the outputs of the linear interpolation units are connected to the multipliers.

EFFECT: increase the digitizer capacity with a smaller ROM volume without losing the performance of the conversion.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to measuring equipment, in particular to tracking sine-cosine angle to code converters, and can be used in automotive engineering, machine tool, aviation and rocket technology and other areas where it is necessary to measure the position using a sensor that generates a sine-cosine signal, whose phase is proportional to the measured angle.

The known solid-state angle converter [1], which contains an input multiplexer of the angle sensor signals, an analog-to-digital converter (ADC), a digital block for calculating the angle, and a digital-to-analog converter (DAC), which converts the calculated angle code to the output voltage of the converter. A feature of the converter is the use of the CORDIC algorithm in the digital block for calculating the angle. The disadvantage of the analogue is the low speed of the converter, in which the conversion time is the sum of the conversion time of the input signals of the angle sensors to a digital code and the number of iterations of angle calculation using the CORDIC algorithm.

Known digital resolver signal converter [2]. The converter converts the sine-cosine signals of the resolver, which is a rotating transformer with two orthogonal windings and a stationary field winding, into a digital code. The converter contains two ADCs of the sine-cosine signal of the resolver, bandpass filters, two multipliers of the codes of the sine and cosine signals for the codes of the sine and cosine values of the output code, an adder of the difference of the outputs of the multipliers and a feedback circuit containing a reversible counter of the output code connected to a read-only memory ( ROM) sine and cosine values for each output code value. A feature of the converter is the use of a tracking algorithm for converting the sine-cosine output signal into an angle code. The disadvantage of the converter is a complex electrical circuit, which contains two ADCs and a processor, the presence of a large-capacity ROM, as well as the limited speed, which is determined by the time the analog signals of the resolver are converted to a digital code.

A known Converter of the sine-cosine signal to a position code [3]. The converter is constructed according to a typical servo circuit and contains two input signal multipliers, a subtractor, a comparator, and a VCO, which generates increment and decrement signals of the reverse counter by the difference subtractor signal. The reverse counter code is the output code of the converter. The converter feature is that the sine and cosine values are not selected from the sine and cosine tables by the counter code, but are calculated by the CORDIC calculator unit, which generates the sine and cosine codes supplied to the input of the cosine and sine signal multipliers, respectively, which reduces ROM volume, but at the same time reduces the speed of the converter.

A device for a digital resolver signal converter [4], selected as a prototype. The converter contains two analog sine and cosine input multipliers, a subtractor, a voltage controlled oscillator (VCO), which generates increment and decrement signals of the reversible counter depending on the sign and magnitude of the mismatch. The reverse counter code is the output code of the converter, the ROM code addresses ROM containing the sine and cosine values for each counter code, by which, respectively, the input signals of the cosine and sine of the resolver are multiplied, due to feedback the counter, ROM, multipliers, subtractor, and VCO the counter takes on a value at which the mismatch between the measured angle and the output code of the counter becomes minimal. The disadvantage of the prototype is the large amount of ROM required, which must store the sine and cosine values for each value of the output code, which requires a large area on the chip chip and, accordingly, the high cost of manufacturing.

The objective of the invention is to increase the bit depth of the converter with a smaller ROM without loss of conversion speed.

The problem is solved due to the fact that in the servo-sine-cosine angle converter to a code containing the first multiplier for multiplying the input voltage of the sine signal by the digital cosine value of the output code, the second multiplier for multiplying the input voltage of the cosine signal by the digital sine value of the output code, the subtracter, whose inputs are connected to the outputs of the multipliers, and the output is connected to a voltage controlled oscillator (VCO), which generates increment signals and is decremented depending on the sign and magnitude of the mismatch, the outputs of the forward and backward counters of the VCO are connected to the reverse counter of the output code of the angle, the output of the counter is connected to the ROM of the sine and cosine values, the following differences are provided, namely, the reverse counter is divided into two parts - the oldest and the youngest, oldest part is connected to the ROM of the sine and cosine values, in addition, two blocks of linear interpolation of the table values of the sine and cosine according to the least significant bits of the reverse counter are introduced, which e are connected to the outputs of the ROM and the lower bits of the reversible counter, the outputs of the linear interpolation units are connected to the multipliers.

There is a causal relationship between the set of essential features of the claimed technical solution and the technical result achieved, namely, linear interpolation of the sine and cosine values can significantly reduce the required ROM volumes, since the tables store the sine and cosine values only for angle points specified by the higher bits of the reversible counter , and the intermediate values of the sine and cosine are calculated by linear interpolation according to the least significant bits of the reverse counter. So, for example, to ensure the accuracy of the 12-bit angle to code conversion, the prototype requires two tables with a volume of 4096 words each, and in the proposed technical solution it is enough to use tables of sine and cosine values of 32 words at the nodal points of interpolation, addressed by 5 high-order bits of the counter , and the intermediate values of the sine and cosine are interpolated by the least significant bits of the counter.

The technical nature of the proposed technical solution is illustrated by drawings, where FIG. 1 contains a block diagram of a converter of a sine-cosine signal to an angle code, FIG. 2 contains a block diagram of a voltage controlled generator.

The block diagram of the converter is shown in FIG. one.

The sine-cosine angle to code converter contains:

1, 2 - multipliers;

3 - subtractor;

4 - voltage controlled oscillator;

5 - reverse counter;

6, 7 - ROM values of the sine and cosine;

8, 9 - linear interpolation blocks of sine and cosine values.

The multipliers 1, 2 are connected to a subtractor 3, the differential voltage from which is supplied to the VCO 4, which generates the increment and decrement signals of the reversible counter, depending on the sign and magnitude of the mismatch. The VCO 4 is connected by signal lines of direct UP and reverse DN counts with a reverse counter 5, the value of which is the output code of the converter. The high-order bits m of the reverse counter 5 are connected to the address inputs of the ROM sine and cosine codes 6, 7, the outputs are connected to linear interpolation units 8, 9, which generate the sine and cosine values of the converter output code based on the table values of the sine and cosine from the ROM and their interpolation on the lower digits of the counter. The outputs of the linear interpolation units 8, 9 are connected to the multipliers 2 and 1, respectively.

To convert the mismatch signal into a counter code, a voltage controlled generator 4 is used, which generates the increment and decrement signals of the reverse counter depending on the sign and magnitude of the mismatch. A VCO diagram is shown in FIG. 2.

The VCO contains an integrator 10, comparators 11 and 12, to which a differential voltage ΔU from the subtractor 3 and a threshold voltage Uth are supplied. The outputs of the comparators 11, 12 are connected to multivibrators 13, 14 and 15, 16, respectively, which contain in the feedback of the elements 14, 16 the transport delay of the signal from the elements 17, 18.

When the difference voltage ΔU of the threshold voltage Uth is exceeded, the corresponding comparator is activated, the signal from which the multivibrator starts, at the output of which a counting pulse is formed with a duration determined by the delay elements. The counting pulse is fed to the reverse counter 5.

The differential signal of the products of the subtractor 3 is determined by the formula:

where Usin (θ), Ucos (θ) are the input voltages,

cos (ϕ), sin (ϕ) are the interpolated values of the sine and cosine calculated by the code of the reverse counter 5.

Formula 1 can be converted

Thus, the difference signal does not depend on the value of the angle, but only on the accuracy of approximation of the angle ϕ to the angle θ.

Linear interpolation is performed on the interpolation points of the sine and cosine values stored in the ROM, selected by the highest bits of the reverse counter. Their number depends on the capacity of the upper part m of the counter. The intermediate values of the sine and cosine are interpolated by the least significant bits of the counter according to the formula

where M, N are the values of the highest and youngest part of the reverse counter;

SIN [...], COS [...] - the sine and cosine values at the interpolation points M and M + 1;

n is the bit depth of the lower part of the reverse counter.

Using linear interpolation when converting an angle to a code allows us to obtain a conversion error when using only 5 and 6 bits of the older part of the reversing counter and, accordingly, interpolation tables with a total of 32 and 64 words, not exceeding the errors of 15 and 19 bits of the reversing counter.

By varying the bit depth of the upper part of the reverse counter m and the lower part - n, we can obtain the bit depth of the output code from 12 to 18 bits. At the same time, memory costs are orders of magnitude less than what is required in the prototype, which is clearly shown in the table below.

The technical and economic effect of the proposed technical solution is to reduce the cost of manufacturing microcircuit converters of the sine-cosine signal into an angle code by reducing the ROM area, as well as reducing the consumption and access time of the ROM by reducing the number of memory cells.

Information sources

1. US patent 3976869.

2. Patent WO 2011068196.

3. RF patent 167428.

4. US patent 4933674 - prototype.

Claims (1)

A servo-sine cosine angle to code converter containing the first multiplier for multiplying the input voltage of the sine signal by the digital cosine value of the output code, the second multiplier for multiplying the input voltage of the cosine signal by the digital sine value of the output code, a subtractor whose inputs are connected to the outputs of the multipliers, and output - with a voltage controlled oscillator, VCO, which generates increment and decrement signals of a reversible counter depending on the sign and in mismatch values, VCO forward and backward count outputs are connected to the reverse counter of the angle output code, the counter output is connected to a read-only memory, ROM, sine and cosine values, characterized in that the reverse counter is divided into two parts - the oldest and the youngest, the older part is connected from the ROM of the sine and cosine values, and the youngest one is connected to the inputs of the linear interpolation blocks of the table values of the sine and cosine by the least significant bits of the reverse counter, which are also connected to the ROM outputs, outputs linear interpolation blocks are connected to the multipliers.

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