RU2355107C2 - Converter of shaft rotation angle into code - Google Patents

Abstract

FIELD: physics, controls.

SUBSTANCE: invention concerns automation and computation. Effect of invention is achieved by converter including first alternate voltage source connected to one of input coils of angle sensor and to first inputs of first and second simultaneous detectors, second inputs of which are connected to first and second outputs of angle sensor respectively, while outputs are connected over first and second keys to data input of analog-to-digital converter with output connected to data inputs of first, second and third registers; output of first register is connected to computation unit, while outputs of second and third registers are connected to computation unit over averaging adder; control signal generator with outputs connected to control inputs of first and second keys, first, second and third registers, adder, analog-to-digital converter, computation unit and second control input of first register. Additionally converter features second alternate voltage source, third and fourth simultaneous detectors, third and fourth keys, so that second source is connected to second input coil of angle sensor and to third and fourth simultaneous detectors, second inputs of which are connected to first and second outputs of angle sensor and outputs are connected over third and fourth keys to analog-to-digital converter; and additional outputs of control signal generator are connected to control inputs of third and fourth keys.

EFFECT: enhanced accuracy of angle-to-code conversion.

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Description

The invention relates to the field of automation and computer technology and can be used to connect angle sensors such as rotating transformers with a digital computing device.

A known converter of the angle of rotation of the shaft into code [1] (prototype), in which the output signals of an angle sensor such as a sine-cosine rotary transformer, one of the input windings of which is powered from an AC voltage source, are fed to the first and second synchronous detectors, and those generated on them DC voltages proportional to the sine and cosine of the angle of rotation of the sensor are sequentially polled and converted into a code using an analog-to-digital converter, keys and their control circuit with an intermediate average iem codes of audio values, thereby bringing samples the sine and cosine of an angle to one point in time and subsequent calculation code angle calculator as an arctangent relationship codes sine and cosine.

A disadvantage of the known device is the reduced accuracy of the Converter due to errors of the angle sensor.

As is known [2], the main component of the error of the angle sensor such as a rotating transformer has the character of the second harmonic from the angle of rotation. Such an error is caused, for example, by the inequality of the transformation coefficients between the primary and each of the secondary windings of the sensor, the mutual non-orthogonality of the magnetic axes of the secondary windings, etc.

The aim of the invention is to significantly reduce the effect of sensor error on the error of the angle-code converter.

This goal is achieved due to the fact that in a known device containing a first AC voltage source connected to one of the input windings of the sine-cosine angle sensor and to the first inputs of the first and second synchronous detectors, the second inputs of which are connected respectively to the first and second outputs of the sensor angle, and the outputs through the first and second keys are connected to the information input of an analog-to-digital converter, the output of which is connected to the information inputs of the first, second and third registers, the output of the first the register is connected directly to the calculator, and the outputs of the second and third registers are connected to the calculator through an averager-adder, a driver of control signals providing control of the converter blocks and supply to the inputs of the calculator of time-averaged voltage codes proportional to the output signals of the angle sensor generated from the first and second variable voltage source, while the calculator determines the output codes corresponding to the angle of rotation of the sensor shaft, with mutually independent power sensor from the first and second source, and finds the average value of the angle code, nine outputs of the driver of the control signals are connected to the control inputs of the first and second keys, the first, second and third registers, the adder, the analog-to-digital converter, the computer, the second control input of the first register , a second AC voltage source is added with a frequency different from the frequency of the first source, connected to the second input of the previously unused sensor winding, the third and fourth synchronous with By the frequency of the second source, detectors, the third and fourth keys, the second source is connected to the second input winding of the angle sensor and to the third and fourth synchronous detectors, the second inputs of which are connected respectively to the second and first outputs of the angle sensor, and the outputs through the third and fourth keys are connected to analog -digital converter, two additional outputs of the driver of the control signals are connected to the control inputs of the third and fourth key.

Due to these changes, taking into account the linearity of the conversion circuit, two values of the angle code are independently generated in the device calculator: one - when the first input winding (excitation winding) of the sensor is energized from the first source and the second - when the second input winding (quadrature winding) of the sensor is fed from the second source .

Express the first code equivalent of the sensor angle (α) in the form:

α _K1 ≈α + Δα _m sin (2α + α _Δ0 ),

where α is the angle of rotation of the sensor shaft,

Δα _m is the amplitude of the total component of the second harmonic of the sensor error,

α _Δ0 is the initial offset of the total second harmonic of the error relative to the magnetic axis of the first input winding (excitation) of the sensor.

For the second code equivalent, taking into account the displacement of the magnetic axis of the second input winding of the (quadrature) sensor relative to the first by 90 °, we will have

α _K2 ≈α + Δα _m sin (2 (α + 90 °) + α _Δ0 ) = α + Δα _m sin (2α + α _Δ0 + 180 °) = α-Δα _m sin (2α + α _Δ0 )

Developing a half-sum of equivalents in the calculator, we obtain for the average value of the code:

Thus, the output angle code is free from the main component of the sensor error.

For the effective operation of the device, the following conditions must be met:

- the form of voltage of the sources should be close to sinusoidal, and their frequencies should whenever possible relate to each other as mutually prime numbers in order to minimize the mutual influence of voltages in synchronous demodulation blocks;

- the frequencies of the first and second sources should be chosen close enough so that the nature of the sensor error basically coincides in both cases of a separate sensor supply from one source.

The drawing shows a structural diagram of a device.

The converter of the angle of rotation of the shaft into a code contains a sine-cosine rotating angle sensor (SKDU) 1, synchronous detectors 2, 3, 15 and 16, keys 4, 5, 17 and 18, an analog-to-digital converter (ADC) 6, registers 7, 8 and 9, an adder 10, a calculator 11, a driver of control signals 12, sources of alternating voltage of different frequencies 13 and 14.

The converter operates as follows.

The first with a frequency of f ₁ 13 and the second with a frequency of f ₂ 14 sources of alternating voltage supply respectively the first (excitation) and second (quadrature) input windings of the SKDU 1. At the first output of the SKDU, signals with a frequency of f ₁ are generated, modulated in amplitude as a function of the sine, and with a frequency f ₂ - in the function of the cosine of the angle α of rotation of the shaft of the control system. At the second output, signals with a frequency f ₁ vary in amplitude as a function of the cosine, and with a frequency f ₂ as a function of the sine of the angle α. At the outputs of synchronous detectors 2, 15, 16 and 3, DC signals are generated that are proportional to sin ₁ α, cos ₂ α, sin ₂ α, cos ₁ α. Here, indices 1 and 2 for sin and cos denote the number of the voltage source from which the function was formed.

Further operation of the Converter is carried out by control signals from the shaper of control signals 12 in the following sequence. According to the first signal from the driver of the control signals 12, the output voltage U ₁ sin ₁ α ₁ from the synchronous detector 2 through the key 4 is fed to the input of the ADC 6, where it is converted to code N ₁ . According to the second signal of the driver of control signals 12, the code N _{1 is} entered in register 8. According to the third signal of the driver of control signals 12, the output voltage

U ₁ cos ₁ α ₂ from the synchronous detector 3 through the key 5 is fed to the input of the ADC 6, where it is converted to code N ₂ , which, according to the fourth signal of the driver of control signals 12, is entered into register 7. The output voltage U _{1 is given by the} fifth signal of the driver of control signals 12 sin ₁ α _{3 of the} synchronous detector 2 through the key 4 is fed to the input of the ADC 6, where it is converted to code N ₃ , which, according to the sixth signal of the driver of the control signals, is entered in register 9. In the adder 10 is formed

,

,

corresponding to the time of formation of the code N ₂ . According to the seventh and eighth signals of the driver of the control signals 12, respectively, received at the control input of the adder 10 and the second control input of the register 7, the output codes of the adder 10 and the register 7 go to the inputs of the calculator 11, where the output code is generated

,

,

proportional to the angle α ₂ at the time of formation of the code N ₂ .

The operation of the ADC 6 is controlled by the signals coming from the output of the driver of control signals 12 to the control input of the ADC 6. In complete analogy with the above for the signals of the driver of control signals 12 from the first to the eighth, the converter runs for the signals of the driver of the control signals 12 from the ninth to sixteenth , with the difference that the output voltages U ₂ sin ₂ α ₄ , U ₂ cos ₂ α ₅ , U ₂ sin ₂ α ₆ from synchronous detectors 16 and 15, which are fed to the ADC 6 through the keys 18 and 17, are processed.

Accordingly, in this case, the control signals of the driver of the control signals 12 are received: the ninth signal to the key 18 (instead of the key 4), and the eleventh to the key 17 (instead of the key 5). As a result, a code is generated in the calculator

,

,

proportional to the angle α ₅ at the time of formation of the code N ₅ . (Here N ₄ , N ₅ , N ₆ are codes proportional to U ₂ sin ₂ α ₄ , U ₂ cos ₂ α ₅ , U ₂ sin ₂ α ₆ ).

, пропорциональный углу α с исключенной из него составляющей ошибки, имеющей характер второй гармоники от угла поворота СКДУ.Finally, a code is generated in the calculator

proportional to the angle α with the error component excluded from it, having the character of the second harmonic from the angle of rotation of the SKDU.

If the change in the angle α during the full cycle of the converter does not exceed the permissible error, the converter operates in the described normal mode. If, on the contrary, the rate of change of the angle α is large and gives changes in the angle comparable with the given error, the cycle automatically shortens the cycle to the number of clock cycles of the control signal generator from the first to the eighth, i.e. return of converter operation in prototype mode.

It should be noted that modern high-speed processor and ADC modules, such as CPU 686 and A111-5A from PROSOFT, on which the proposed device can be implemented, allow you to complete the entire conversion cycle in less than 70 μs. When the rate of change of the angle is less than 10 ° / s, this gives an error of not more than 3 angles. from. Thus, the limitation in the effectiveness of the application of the invention does not look severe.

The implementation of the proposed device allowed to increase the accuracy of the Converter on a rotating transformer by 1.5-2 times.

Information sources

1. USSR author's certificate No. 4317561, cl. H03M 1/58, 10.19.87.

2. A.A. Akhmetzhanov. High precision angle transmission systems of automatic devices. "Energy", M. 1975. Pages 89-116.

Claims (1)

The converter of the angle of rotation of the shaft into a code containing a first AC voltage source connected to one of the input windings of the sine-cosine angle sensor and to the first inputs of the first and second synchronous detectors, the second inputs of which are connected respectively to the first and second outputs of the angle sensor, and the outputs through the first and second keys are connected to the information input of an analog-to-digital converter, the output of which is connected to the information inputs of the first, second and third registers, the output of the first register is connected to the calculator directly, and the outputs of the second and third registers are connected to the calculator through the homogenizer-adder, a control signal generator that controls the converter blocks and supplies the voltage-averaged voltage codes proportional to the output signals of the angle sensor from the first and second source of variables to the inputs of the calculator voltage, while the calculator determines the output codes corresponding to the angle of rotation of the sensor shaft, with mutually independent supply of the sensor from the first o and the second source, and finds the average value of the angle code, nine outputs of the driver of the control signals are connected to the control inputs of the first and second keys, the first, second and third registers, the adder, the analog-to-digital converter, the computer, the second control input of the first register, characterized in that a second AC voltage source with a frequency different from the frequency of the first source, connected to the second input coil of the sensor not previously used, is introduced into it, the third and fourth are synchronous e with the frequency of the second source detectors, the third and fourth keys, the second source is connected to the second input winding of the angle sensor and to the third and fourth synchronous detectors, the second inputs of which are connected respectively to the second and first outputs of the angle sensor, and the outputs through the third and fourth keys are connected to the analog-to-digital converter, two additional outputs of the driver of the control signals are connected to the control inputs of the third and fourth key.