Constant-amplitude digital-axial angle converter and working method thereof

Abstract

The invention relates to a fixed-amplitude digital-axial angle converter and a working method thereof. The digital-axial angle converter comprises a zero-crossing comparator, a sine function generator, an angle value register, an angle operation unit, a first multiplier unit, a second multiplier unit, a first digital-to-analog converter and a second digital-to-analog converter. According to the fixed-amplitude digital-axial angle converter disclosed by the invention, the input reference signal and the output coupling signal are not related in amplitude, so that isolation of signal acquisition and signal transmission is realized, and a guarantee effect on signal transmission is achieved; a digital-axial angle converter is realized in a digital mode, and the change rate of an analog angle is improved. According to the method, the requirement for an analog multiplier is reduced, more universal digital components are used instead, the cost is reduced, meanwhile, easy-to-actual-effect links are reduced, sine and cosine numerical values are calculated by using a table look-up method, and the digital operation rate is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of digital-axis-angle converters, and in particular to a constant-amplitude digital-axis-angle converter and a working method thereof. Background Art

[0002] A digital-to-synthetic axis converter (DSAC) is a device that converts digital signals into analog angle signals and belongs to the digital / analog conversion circuit. The purpose of a digital-to-synthetic axis converter is to convert the angle value input represented by binary digital quantity into an analog signal output in the form of a rotary transformer by coupling the excitation signal. It has a wide range of applications in aerospace, aviation, ships, weapons and other fields, providing a highly reliable angle signal transmission method.

[0003] Existing digital-axis-angle converters mainly use quadrant division plus arc fitting mathematical methods to calculate the sine and cosine angle values, and then use multiplication DAC devices to realize the coupling of the sine and cosine angle values ​​with the excitation signal. The signal output accuracy depends on the fineness of the quadrant division and the number of bits of the multiplication DAC. However, the accuracy of the quadrant division directly affects the quality of the final output signal. In order to obtain higher accuracy, it is often necessary to divide the quadrants more finely, but this will increase the hardware complexity and cost. In particular, the quadrant division circuit structure is complex, and the higher the division fineness, the larger the circuit scale, which brings many difficulties to the miniaturization of the circuit. As the division fineness increases, the electronic circuits used to implement these functions will also become larger and more complex, which is a challenge for the pursuit of miniaturized design. The resolution of the multiplication DAC itself also limits the accuracy of the output signal. Although high-resolution DACs can provide better performance, they also face problems of cost and complexity.

[0004] Therefore, in order to solve the deficiencies in the prior art, it is urgent to realize a constant amplitude digital-to-axis angle converter. Summary of the invention

[0005] The object of the present invention is to provide a constant-amplitude digital-to-axis angle converter and a working method thereof, which can solve the deficiencies in the prior art, realize the digital-to-axis angle converter in a digital manner, improve the analog angle change rate and the accuracy of the analog axis angle signal, and reduce the cost and complexity.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A constant amplitude digital-axis angle converter comprises a zero-crossing comparator, a sine function generator, an angle value register, an angle operation unit, a first multiplier unit, a second multiplier unit, a first digital-analog converter and a second digital-analog converter.

[0008] The zero-crossing comparator has a positive input terminal connected to a reference signal, a negative input terminal connected to ground, and an output terminal connected to an input terminal of a sine function generator.

[0009] The output end of the sine function generator is connected to the first input end of the first multiplier unit and the first input end of the second multiplier unit respectively.

[0010] The input end of the angle value register is connected to the binary digital angle value, and the output end is connected to the angle calculation unit.

[0011] The output end of the angle calculation unit is connected to the second input end of the first multiplier unit and the second multiplier unit respectively.

[0012] The output end of the first multiplier unit is connected to the input end of the first digital-to-analog converter; the output end of the second multiplier unit is connected to the input end of the first digital-to-analog converter.

[0013] Furthermore, the digital-axis-angle converter uses a general FPGA as a digital processing core unit; the sine function generator, the angle value register, the angle calculation unit, the first multiplier unit and the second multiplier unit constitute the FPGA.

[0014] Furthermore, the zero-crossing comparator is used to detect the zero-crossing condition of the reference signal to calculate the period.

[0015] Furthermore, the sine function generator is used to generate a discrete sine signal, and the discrete sine signal is used to couple with the angle value operation.

[0016] Furthermore, the angle value register is used to temporarily store the input binary digital angle value.

[0017] Furthermore, the angle calculation unit is used to calculate the sine and cosine values ​​corresponding to the angle by using a table lookup operation.

[0018] Furthermore, the first multiplier unit is used to implement the multiplication operation of the sine value and the discrete sine signal; the second multiplier unit is used to implement the multiplication operation of the cosine value and the discrete sine signal.

[0019] Furthermore, the first digital-to-analog converter and the second digital-to-analog converter are both used to convert the digital multiplication result into an analog shaft angle signal.

[0020] The present invention also includes a working method of the above-mentioned constant amplitude digital-axis angle converter, which comprises the following steps:

[0021] S1. Reference signal processing

[0022] The reference signal is input to the zero-crossing comparator, which detects the zero-crossing point of the reference signal. Based on the output result of the zero-crossing comparator, the period t of the reference signal is determined.

[0023] S2, discrete sine signal generation

[0024] The sine function generator outputs a discrete sine signal sin(ωt+φ) with the same period as the reference signal.

[0025] S3, Angle value storage

[0026] The binary digital angle value θ is input into the angle value register, and the angle value is temporarily stored in the angle value register.

[0027] S4. Angle calculation

[0028] The angle value register inputs the stored angle value into the angle operation unit according to the set refresh time, and the angle operation unit uses a table lookup operation method to query the sine value sinθ and cosine value cosθ corresponding to the angle value.

[0029] S5. Digital domain perspective and signal coupling

[0030] The sine value sinθ and cosine value cosθ calculated by the angle calculation unit are sent to the first multiplier unit and the second multiplier unit respectively. The first multiplier unit is used to multiply the sine value sinθ with the discrete sine signal sin(ωt+φ), and the second multiplier unit is used to multiply the cosine value cosθ with the discrete sine signal sin(ωt+φ), thereby obtaining two coupled sine value multiplication results.

[0031] S6, analog shaft angle signal generation

[0032] The multiplication results of the two coupled sinusoidal values ​​are sent to the first digital-to-analog converter and the second digital-to-analog converter respectively. After the two digital-to-analog converters perform digital-to-analog conversion, an analog shaft angle signal synthesized by the digital angle θ and the reference signal is obtained.

[0033] Furthermore, the signal output frequency of the sine function generator is 20 MHz.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] (1) The constant amplitude digital-axis angle converter described in the present invention has an input reference signal and an output coupling signal that are not correlated in amplitude, thereby isolating signal acquisition from signal transmission and protecting signal transmission. The present invention uses a digital method to implement a digital-axis angle converter, thereby improving the analog angle change rate and the accuracy of the analog axis angle signal. The present invention reduces the demand for analog multipliers and uses more general digital components instead, thereby reducing costs and reducing the number of practical links. In addition, by using a table lookup method to calculate the sine and cosine values, the digital operation rate is greatly improved.

[0036] (2) The analog signal output by the existing DRC products is a coupled signal of the excitation signal and the angle signal. If the amplitude of the excitation signal is very low, the accuracy of the output analog signal is limited. The present invention uses the external excitation signal as a reference timing, retains only the phase information and ignores the amplitude information, and then generates a sinusoidal signal with a predetermined amplitude in the product, couples it with the angle signal and outputs it. This way, the product structure is simple and the output accuracy is stable. The problem solved by the present invention is mainly the accuracy problem, ensuring that high-precision output can be achieved even when the excitation signal is not ideal; and because the excitation signal itself is no longer coupled, the overall design becomes simpler.

[0037] (3) The fixed-amplitude digital-axis angle converter described in the present invention realizes the function of fixed amplitude. Currently, such fixed-amplitude products are not available on the market. In most occasions (especially in ships and aviation equipment command systems), the fixed-amplitude digital-axis angle converter described in the present invention is more applicable than traditional products, because the amplitude is determined, so the subsequent circuit can be better adapted. The present invention adopts a sufficiently simplified design scheme to reduce the complexity of the entire product, thereby improving the reliability of the product. Previous products all processed and approximated analog signals, while the present invention uses digital signals for direct processing. With the continuous development of DAC technology, the fixed-amplitude digital-axis angle converter described in the present invention can directly achieve improved accuracy, which is equivalent to providing a set of universal design schemes to meet the ever-increasing application needs in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a principle block diagram of the fixed amplitude digital-axis angle converter in the present invention;

[0039] Figure 2 It is a method flow chart of the working method of the fixed amplitude digital-axis angle converter in the present invention.

[0040] in:

[0041] 1. Zero-crossing comparator, 2. Sine function generator, 3. Angle value register, 4. Angle calculation unit, 5. First multiplier unit, 6. Second multiplier unit, 7. First digital-to-analog converter, 8. Second digital-to-analog converter. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings:

[0043] like Figure 1 A fixed amplitude digital-axis angle converter is shown, which uses a general FPGA as a digital processing core unit. The digital-axis angle converter includes a zero-crossing comparator 1, a sine function generator 2, an angle value register 3, an angle calculation unit 4, a first multiplier unit 5, a second multiplier unit 6, a first digital-to-analog converter 7, and a second digital-to-analog converter 8. The sine function generator 2, the angle value register 3, the angle calculation unit 4, the first multiplier unit 5, and the second multiplier unit 6 constitute an FPGA.

[0044] The constant amplitude digital-axis angle converter of the present invention constructs the entire signal processing flow of digital-axis angle conversion based on the programmability of FPGA, and each component works together from reference signal processing to angle value input, calculation and final analog signal output. The system core is constructed with a general FPGA, which is more flexible and scalable than the traditional dedicated circuit architecture.

[0045] FPGA as the core can be flexibly programmed to implement various functional logics. Zero-crossing comparator 1, used to detect the zero-crossing condition of the reference signal for subsequent calculation cycles. Sine function generator 2, used to generate a discrete sine signal, which is used to couple with the angle value operation. Angle value register 3, used to temporarily store the input binary digital angle quantity. Angle operation unit 4, used to calculate the sine and cosine values ​​corresponding to the angle. The first multiplier unit 5, used to realize the multiplication operation of the sine value and the discrete sine signal. The second multiplier unit 6, used to realize the multiplication operation of the cosine value and the discrete sine signal. The first digital-to-analog converter 7 and the second digital-to-analog converter 8, are both used to convert the digital multiplication result into an analog shaft angle signal.

[0046] like Figure 2 As shown, the present invention also includes a working method of the above-mentioned constant amplitude digital-axis angle converter, which includes the following steps:

[0047] S1. Reference signal processing

[0048] The reference signal is input to the zero-crossing comparator 1 , which detects the zero-crossing point of the reference signal. Based on the output result of the zero-crossing comparator 1 , the period t of the reference signal is determined.

[0049] In this embodiment, the output signal of the zero-crossing comparator 1 is input into the IO pin of the FPGA chip, and the FPGA collects the falling edge of the output signal of the zero-crossing comparator 1, and calculates the time interval between adjacent falling edges, and uses the time interval as the period t. When the sine wave signal passes through the zero-crossing point, the output state of the zero-crossing comparator 1 flips. This flip can be captured by the FPGA to determine the signal period. By capturing the zero-crossing point instead of directly measuring the signal amplitude, the dependence on signal strength is avoided, the signal processing is simplified, the robustness of the system is improved, and the error caused by the change of the signal amplitude is reduced. The above design gets rid of the error of the reference signal caused by the transmission process from the method level, and eliminates the influence of the low amplitude of the reference signal on the accuracy of the output signal.

[0050] S2, discrete sine signal generation

[0051] The sine function generator 2 outputs a discrete sine signal sin(ωt+φ) having the same period as the reference signal.

[0052] The sine function generator 2 is used to generate a discrete sine wave synchronized with the reference signal. Based on the high-speed clock inside the FPGA, a sine waveform is generated at a preset frequency (eg, 20 MHz), and the waveform data can be pre-stored in a lookup table.

[0053] Since the reference signals used in the project are mostly sinusoidal signals with frequencies ranging from 400Hz to 20kHz, a periodic unit sinusoidal signal is divided into 1000 points and written into the FPGA chip to sufficiently ensure the accuracy of the signal, so the signal output frequency of the sine function generator 2 is set to 20MHz. In this way, the sine function generator 2 outputs a discrete sine signal sin(ωt+φ) with the same period as the reference signal. The discrete sine signal sin(ωt+φ) fluctuates with the period fluctuation of the reference signal and does not change with the amplitude change of the reference signal. Using a digital sine wave generator can ensure that the period of the output signal of the sine function generator 2 is consistent with the reference signal, but is not affected by its amplitude, so that it can be unaffected by the amplitude fluctuation of the input signal, ensuring that the stability of the output signal is improved.

[0054] In step S1 and step S2, the zero-crossing comparator 1 can accurately capture the key nodes of the signal period change, and the comparison function of the zero-crossing comparator 1 is used to detect the signal level change. The FPGA obtains the period by measuring the time interval of the falling edge, and then sets the parameters of the sine function generator according to the period to generate a discrete sine signal with the same period. Through the above design, the reference signal period can be accurately determined so as to generate a discrete sine signal matching it for subsequent angle coupling calculation.

[0055] Different from the traditional analog circuit processing reference signal method, the present invention accurately obtains the reference signal period and generates the corresponding discrete sine signal in a digital way. The digital processing reference signal period is more accurate, and the generation of discrete sine signals facilitates subsequent digital operations and is not affected by the drift of analog circuit component characteristics.

[0056] S3, Angle value storage

[0057] The binary digital angle value θ is input into the angle value register 3, and the angle value is temporarily stored in the angle value register 3.

[0058] Existing DRC products use analog devices to calculate angle values, and the data refresh time is mostly on the order of 20ms, which limits the output signal speed simulation range. In the present invention, the angle value register 3 can ensure the temporary storage and stable input of angle data. The angle register 3 inside the FPGA is used to temporarily store digital angle values. The refresh frequency and refresh time of the register can be configured by the FPGA chip as needed. Since the main frequency of the FPGA chip used in the present invention is 800MHz and the subsequent operation time is expected to be 100ns, the refresh time of the angle value register 3 can be designed to be any value greater than 100ns. By configuring the refresh time, the speed of angle update can be adjusted according to application requirements, thereby flexibly adjusting the system response speed.

[0059] S4. Angle calculation

[0060] The angle value register 3 inputs the stored angle value into the angle calculation unit 4 according to the set refresh time, and the angle calculation unit 4 uses a table lookup operation to query the sine value sinθ and cosine value cosθ corresponding to the angle value. That is, for each angle θ value sent to the angle calculation unit 4, the corresponding sinθ and cosθ values ​​can be queried by table lookup. The resolution of angle θ is the same as the resolution of sinθ and cosθ values. Preferably, 16-bit resolution is used. The table lookup operation uses the pre-stored correspondence between angles and sine and cosine values ​​to quickly obtain results. The sine and cosine values ​​can be quickly obtained through the table lookup operation, which significantly speeds up the calculation speed while maintaining a high degree of accuracy.

[0061] S5. Digital domain perspective and signal coupling

[0062] The sine value sinθ and cosine value cosθ calculated by the angle calculation unit 4 are respectively sent to the first multiplier unit 5 and the second multiplier unit 6. The first multiplier unit 5 is used to multiply the sine value sinθ with the discrete sine signal sin(ωt+φ), and the second multiplier unit 6 is used to multiply the cosine value cosθ with the discrete sine signal sin(ωt+φ), thereby obtaining two coupled sine value multiplication results. These two multiplication results carry the coupling information of the digital angle information and the reference signal. They complete the fusion of the angle value and the reference signal in the digital domain, and provide a basis for the subsequent conversion into an analog shaft angle signal.

[0063] The digital multiplication operation realizes the coupling of the angle information and the reference signal. The digital multiplication is used instead of the traditional analog multiplication, which improves the accuracy and stability, reduces the dependence on high-precision analog components, and reduces the cost and complexity.

[0064] S6, analog shaft angle signal generation

[0065] The multiplication results of the two coupled sinusoidal values ​​are respectively sent to the first digital-to-analog converter 7 and the second digital-to-analog converter 8. After the two digital-to-analog converters perform digital-to-analog conversion, an analog shaft angle signal synthesized by the digital angle θ and the reference signal is obtained. The resolution of the digital-to-analog converter DAC is consistent with the resolution of the angle θ.

[0066] The digital-to-analog converter realizes the conversion from digital signals to analog signals. Because in practical applications, many devices (such as motor control, sensor interface, etc.) require analog shaft angle signals to drive or receive, so this step is the key link between the digital processing part and the actual application scenario. Analog signals are easy to transmit in low-frequency and high-amplitude forms in ships and aviation equipment, ensuring the anti-interference of the core data of angular position action.

[0067] Since digital-axis-angle converters are mostly used for long-distance transmission of angular positions, different reference signal strengths have a significant impact on transmission distance and signal transmission quality. Traditional digital-axis-angle converters mostly use analog multipliers to perform angle coupling simulation, and the amplitude follows the change of the reference signal. The present invention eliminates this situation, digitally isolates the acquisition of the reference signal from the generation of the coupling signal, reduces the system's requirements for components, and realizes the normalization of the digital-axis-angle converter signal amplitude.

[0068] In the prior art, there is a case where an analog multiplier is used to perform angle coupling simulation. The present invention first completes the multiplication coupling operation in the digital domain, and then performs digital-to-analog conversion. This digital-to-digital-to-analog processing flow is more accurate, less affected by the characteristics of analog circuit components (such as temperature drift, nonlinearity, etc.), and the accuracy of the analog shaft angle signal is higher. By performing digital-to-analog conversion on the multiplication result after digital processing, the signal accuracy can be better controlled. Traditional analog multipliers may be limited by the performance of analog components in terms of accuracy improvement. The present invention is more flexible in adjusting the multiplication result in the digital domain. For example, the resolution of the digital angle, the frequency of the reference signal and other parameters can be easily modified without large-scale changes to the analog circuit.

[0069] In summary, the fixed-amplitude digital-axis-angle converter described in the present invention has an input reference signal and an output coupled signal that are not correlated in amplitude, thereby isolating signal acquisition from signal transmission and protecting signal transmission. The digital-axis-angle converter is implemented in a digital manner, which improves the rate of change of the analog angle. The present invention reduces the demand for analog multipliers and uses more general digital components instead, which reduces costs and reduces the number of practical links. The direct use of the table lookup method to calculate the sine and cosine values ​​greatly improves the digital operation rate.

[0070] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. A constant amplitude digital-to-axis converter, characterized in that: The digital-axis-angle converter comprises a zero-crossing comparator (1), a sine function generator (2), an angle value register (3), an angle calculation unit (4), a first multiplier unit (5), a second multiplier unit (6), a first digital-to-analog converter (7) and a second digital-to-analog converter (8); The zero-crossing comparator (1) has a positive input terminal connected to a reference signal, a negative input terminal connected to ground, and an output terminal connected to an input terminal of a sine function generator (2); The output end of the sine function generator (2) is connected to the first input end of the first multiplier unit (5) and the second multiplier unit (6) respectively; The input end of the angle value register (3) is connected to the binary digital angle value, and the output end is connected to the angle calculation unit (4); The output end of the angle calculation unit (4) is respectively connected to the second input end of the first multiplier unit (5) and the second multiplier unit (6); The output end of the first multiplier unit (5) is connected to the input end of the first digital-to-analog converter (7); the output end of the second multiplier unit (6) is connected to the input end of the first digital-to-analog converter (7).

2. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The digital-axis angle converter uses a general FPGA as a digital processing core unit; The sine function generator (2), the angle value register (3), the angle calculation unit (4), the first multiplier unit (5) and the second multiplier unit (6) form an FPGA.

3. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The zero-crossing comparator (1) is used to detect the zero-crossing condition of the reference signal to calculate the period.

4. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The sine function generator (2) is used to generate a discrete sine signal, and the discrete sine signal is used to couple with the angle value operation.

5. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The angle value register (3) is used to temporarily store the input binary digital angle value.

6. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The angle calculation unit (4) is used to calculate the sine and cosine values ​​corresponding to the angle by using a table lookup operation method.

7. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The first multiplier unit (5) is used to implement a multiplication operation between a sine value and a discrete sine signal; The second multiplier unit (6) is used to implement a multiplication operation of a cosine value and a discrete sine signal.

8. The constant amplitude digital-to-axis converter according to claim 1, characterized in that: The first digital-to-analog converter (7) and the second digital-to-analog converter (8) are both used to convert the digital multiplication result into an analog shaft angle signal.

9. The working method of the constant amplitude digital-to-axis angle converter according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1. Reference signal processing The reference signal is input into a zero-crossing comparator (1), the zero-crossing comparator (1) detects the zero-crossing point of the reference signal, and based on the output result of the zero-crossing comparator (1), the period t of the reference signal is determined; S2, discrete sine signal generation The sine function generator (2) outputs a discrete sine signal sin(ωt+φ) having the same period as the reference signal; S3, Angle value storage The binary digital angle value θ is input into the angle value register (3), and the angle value is temporarily stored in the angle value register (3); S4. Angle calculation The angle value register (3) inputs the stored angle value into the angle calculation unit (4) according to the set refresh time, and the angle calculation unit (4) uses a table lookup operation method to query the sine value sinθ and the cosine value cosθ corresponding to the angle value; S5. Digital domain perspective and signal coupling The sine value sinθ and the cosine value cosθ calculated by the angle calculation unit (4) are sent to a first multiplier unit (5) and a second multiplier unit (6) respectively. The first multiplier unit (5) is used to multiply the sine value sinθ with the discrete sine signal sin(ωt+φ), and the second multiplier unit (6) is used to multiply the cosine value cosθ with the discrete sine signal sin(ωt+φ), thereby obtaining two coupled sine value multiplication results. S6, analog shaft angle signal generation The multiplication results of the two coupled sine values ​​are respectively sent to a first digital-to-analog converter (7) and a second digital-to-analog converter (8), and after digital-to-analog conversion by the two digital-to-analog converters, an analog shaft angle signal synthesized from a digital angle θ and a reference signal is obtained.

10. The working method of the constant amplitude digital-to-axis angle converter according to claim 9, characterized in that: The signal output frequency of the sine function generator (2) is 20 MHz.

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