CN111025190B - Rotary transformer signal conditioning circuit and method - Google Patents

Rotary transformer signal conditioning circuit and method Download PDF

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Publication number
CN111025190B
CN111025190B CN201911180474.8A CN201911180474A CN111025190B CN 111025190 B CN111025190 B CN 111025190B CN 201911180474 A CN201911180474 A CN 201911180474A CN 111025190 B CN111025190 B CN 111025190B
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circuit
tan
resistor
equal
theta
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CN111025190A (en
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王浩
毛宁
张弛
张琬珍
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Xian Aeronautics Computing Technique Research Institute of AVIC
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Xian Aeronautics Computing Technique Research Institute of AVIC
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C9/00—Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
    • G05B19/0423—Input/output
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/20—Pc systems
    • G05B2219/21—Pc I-O input output
    • G05B2219/21137—Analog to digital conversion, ADC, DAC

Abstract

The invention belongs to the signal conditioning technology of a rotary transformer, and particularly relates to a signal conditioning circuit and a signal conditioning method of the rotary transformer, which solve the problems of high price and poor universality of the conventional signal conditioning circuit of the rotary transformer. The rotary transformer conditioning circuit comprises an excitation circuit, a primary open circuit detection circuit, a lossless full-wave rectification circuit, a filter circuit, an AD acquisition circuit and a CPU. The excitation circuit provides standard sinusoidal excitation drive for the rotary transformer; the primary open circuit detection circuit is connected with the excitation circuit and used for detecting the primary open circuit fault of the rotary transformer; the feedback signal of the rotary transformer is respectively regulated by a lossless full-wave rectifying circuit and a filter circuit in sequence and then outputs a direct-current voltage signal, and the direct-current voltage signal can obtain a digital signal after passing through an AD acquisition circuit; the angle value of the resolver can be obtained by an arctangent method. The signal conditioning of the rotary transformer is realized only through common components, the structure is simple, and the cost is low; and circuit parameters are adjustable, and the device is suitable for signal conditioning of multiple rotary transformers.

Description

Rotary transformer signal conditioning circuit and method
Technical Field
The invention belongs to the signal conditioning technology of a rotary transformer of an aircraft engine, and particularly relates to a signal conditioning circuit and a signal conditioning method of the rotary transformer.
Background
In an aircraft engine control system, position information such as an accelerator rod and a fuel metering valve needs to be acquired constantly, and the rotary transformer has the characteristics of high precision, good stability, strong impact resistance and anti-interference capability and the like, and is widely applied to the aircraft engine control system. The precision and stability of the position information acquisition of the throttle lever and the like directly influence the performance, function and stable operation of the engine.
At present, resolver conditioning circuit mainly uses dedicated RDC to condition integrated chip, possesses fast, the precision is high, but is expensive, still needs to design resolver and RDC chip's interface circuit, and RDC chip kind is limited moreover, consequently still needs the decoding system of being built by the separator to satisfy special requirement. The invention researches the characteristics of the output signal of the rotary transformer and designs the rotary transformer conditioning circuit constructed by the separating device on the basis.
Disclosure of Invention
The invention aims to provide a rotary transformer signal conditioning circuit and a rotary transformer signal conditioning method, which solve the problems of high price and poor universality of the conventional rotary transformer conditioning circuit.
The technical scheme of the invention is to provide a rotary transformer conditioning circuit, which is characterized in that: the circuit comprises an excitation circuit, a primary open circuit detection circuit, 2 paths of lossless full-wave rectification circuits, 2 paths of filter circuits, 2 paths of AD acquisition circuits and 1 CPU;
the excitation circuit provides standard sinusoidal excitation drive for the rotary transformer; the primary open circuit detection circuit is connected with the excitation circuit and is used for detecting the primary open circuit fault of the rotary transformer; the feedback signal SIN end and the COS end of the rotary transformer are respectively regulated by a lossless full-wave rectifying circuit and a filter circuit in sequence and then output direct-current voltage signals SIN _ DC and COS _ DC, and the direct-current voltage signals SIN _ DC and COS _ DC can obtain digital signals after passing through an AD acquisition circuit;
the CPU stores a decoding program that, when executed, implements the following processes:
step 1: setting the flag positions r0, r1 and r2 to zero, receiving the AD acquisition results SIN _ DC and COS _ DC, and obtaining a tangent value tan (theta) of a rotating angle theta of the rotary transformer according to the SIN _ DC and the COS _ DC;
step 2: if tan (θ) <0, let tan (θ) equal to-tan (θ), and put r0 equal to 1;
and step 3: if tan (θ) > tan (45 °), let tan (θ) equal to tan (90 ° - θ), and put r1 equal to 1;
and 4, step 4: if tan (θ) > tan (15 °), let tan (θ) equal to tan (θ -30 °), and put r2 equal to 1;
and 5: obtaining the value of the rotating transformer rotating angle theta by using a fitting formula theta ═ tan (theta) × [ a × (theta) × tan (theta) + b ]/[ tan (theta) × tan (theta) + c ], wherein a, b and c are obtained through simulation tests and are all constant values;
step 6: if r2 is equal to 1, θ is equal to θ +30 °;
and 7: if r1 is equal to 1, then θ is equal to 90 ° - θ;
and 8: if r0 is 1, then θ is- θ;
and step 9: and theta is the rotation angle position information of the rotary transformer.
Furthermore, the constant value a is between 0.4 and 0.5, the constant value b is between 1.6 and 1.7, the constant value c is between 1.6 and 1.7, and all the a, b and c need to reserve 10 significant digits.
Furthermore, the excitation circuit comprises an FPGA or an MCU, a current type DA chip, an I/V conversion circuit and a drive circuit; the FPGA or the MCU controls a current type DA chip, the output of the current type DA chip is connected to the input end of the I/V conversion circuit, and the output end of the I/V conversion circuit is connected with the driving circuit;
the driving circuit comprises an integrating circuit consisting of an operational amplifier D1 and a capacitor C1, a push-pull amplifying circuit consisting of a resistor R1, a triode V1 and a transistor V2, a sampling resistor R0 and a feedback resistor R2; the output end of the I/V conversion circuit is connected with the positive input end of an operational amplifier D1, two ends of a capacitor C1 are respectively connected with the negative input end and the output end of the operational amplifier D1, the output end of the operational amplifier D1 is simultaneously connected with a triode V1, the base of a transistor V2 and one end of a resistor R1, the other end of the resistor R1 is simultaneously connected with an emitter of a triode V1 and a transistor V2 and one end of a resistor R0, collectors of the triode V1 and the transistor V2 are respectively connected with a positive power supply and a negative power supply, and two ends of a resistor R2 are respectively connected with the negative input end of the operational amplifier D1 and the other end of the resistor R0; two input ends of the primary open circuit detection circuit are respectively connected with two ends of the R0;
the FPGA or the MCU controls a current type D/A chip by reading standard sine data in the SIN _ ROM, outputs a standard sine waveform through an I/V conversion circuit, and generates sine wave excitation with driving capability after passing through a negative feedback driving circuit consisting of an integrating circuit and a push-pull amplifying circuit.
Further, the primary open circuit detection circuit comprises an operational amplifier D2, a resistor R3-resistor R11, a diode V3, a capacitor C2 and a voltage comparator; one end of the resistor R3 and one end of the resistor R4 are respectively connected to two ends of the sampling resistor R0, and the other ends of the resistors are respectively connected with the negative input end and the positive input end of the operational amplifier D2; two ends of the resistor R5 are respectively connected with the negative input end and the output end of the operational amplifier D2; the two ends of the resistor R6 are connected with the ground and the positive input end of the operational amplifier D2; the positive end of a diode V3 is connected with the output end of an operational amplifier D2, the negative end of a diode V3 is connected with the negative input end of a voltage comparator through a resistor R7, the two ends of the resistor R9 and a capacitor C2 are connected with the negative input ends of the ground and the voltage comparator, the two ends of a resistor R8 are connected with a voltage reference V _ REF and the positive input end of the voltage comparator, and the two ends of a resistor R10 are respectively connected with the ground and the positive input end of the voltage comparator; the resistor R11 is a pull-up resistor at the output end of the voltage comparator, and two ends of the resistor R11 are respectively connected with the power supply VCC and the output end of the voltage comparator. Whether open circuit fault occurs is judged by detecting whether voltage drops exist at two ends of a sampling resistor in the exciting circuit.
Furthermore, the lossless full-wave rectification circuit consists of an inverting circuit and a simulation single-pole double-throw switch; the input AC signal is simultaneously connected to the input end of the inverter circuit and the B end of the analog single-pole double-throw switch, the A end of the analog single-pole double-throw switch is connected with the output end of the inverter circuit, and the control signal ucAnd is connected with the control end of the analog single-pole double-throw switch. When control signal u of single-pole double-throw switchcAt low level, uinThe inverted signal is output to a pin D through a pin A; when the control signal ucWhen it is at high level, u isinAnd output to the D pin through the B pin. If the control signal ucIs in direct contact with an input AC signal uinFully synchronous square waves, i.e. at uinWhen the voltage is in the positive half cycle, the control signal is high level, and the pin D outputs a signal uoIs uinA positive half cycle signal; at uinAt negative half cycle, the control signal ucAt low level, pin D outputs signal uoIs uinNegative half cycle of inverted signal. In summary, the output signal uoFor an input signal uinIs output by full-wave rectification.
Further, the filter circuit comprises an RC low-pass filter and a second-order infinite gain multi-path feedback low-pass filter which are connected in sequence.
The invention also provides a conditioning method of the rotary transformer conditioning circuit, which comprises the following steps:
the method comprises the following steps that firstly, an FPGA or an MCU controls a current type D/A chip and outputs a standard sine waveform through an I/V conversion circuit by reading standard sine data in an SIN _ ROM, and the standard sine waveform generates sine wave excitation with driving capability after passing through a negative feedback driving circuit formed by an integrating circuit and a push-pull amplifying circuit;
step two, sine wave excitation is applied to a rotary transformer, sine signals and cosine signals output by a secondary side of the rotary transformer are alternating current signals, and sine and cosine direct current voltage signals SIN _ DC and COS _ DC are obtained after the alternating current signals are respectively subjected to lossless full-wave rectification and a filter circuit;
step three, when the lossless full-wave rectification and filtering circuit works, the primary open-circuit detection circuit constantly monitors the voltage drop at two ends of a sampling resistor R0 in the excitation circuit, and whether a primary open-circuit fault occurs is judged; when voltage drop exists at the two ends of the sampling resistor, the fact that open-circuit fault does not occur is indicated; when no voltage drop exists at the two ends of the sampling resistor, an open-circuit fault is prompted to occur;
step four, obtaining a digital signal by the direct-current voltage signal SIN _ DC and the direct-current voltage signal COS _ DC through an AD acquisition circuit; the CPU stores a decoding program that, when executed, implements the following processes:
step 4-1: setting the flag positions r0, r1 and r2 to zero, receiving the AD acquisition results SIN _ DC and COS _ DC, and obtaining a tangent value tan (theta) of a rotating angle theta of the rotary transformer according to the SIN _ DC and the COS _ DC;
step 4-2: if tan (θ) <0, let tan (θ) equal to-tan (θ), and put r0 equal to 1;
step 4-3: if tan (θ) > tan (45 °), let tan (θ) equal to tan (90 ° - θ), and put r1 equal to 1;
step 4-4: if tan (θ) > tan (15 °), let tan (θ) equal to tan (θ -30 °), and put r2 equal to 1;
and 4-5: obtaining the value of the rotating transformer rotating angle theta by using a fitting formula theta ═ tan (theta) × [ a × (theta) × tan (theta) + b ]/[ tan (theta) × tan (theta) + c ], wherein a, b and c are obtained through simulation tests and are all constant values;
and 4-6: if r2 is equal to 1, θ is equal to θ +30 °;
and 4-7: if r1 is equal to 1, then θ is equal to 90 ° - θ;
and 4-8: if r0 is 1, then θ is- θ;
and 4-9: and theta is the rotation angle position information of the rotary transformer.
The invention has the beneficial effects that:
1. the invention realizes the signal conditioning of the rotary transformer only by common components such as an operational amplifier, a simulation single-pole double-throw switch, a resistance-capacitance switch and the like, and has simple structure and low cost; and the circuit parameters are adjustable, and the circuit is suitable for signal conditioning of multiple rotary transformers.
2. The invention can provide a solution for a sensor conditioning and arc tangent method of a rotary transformer and the like, the precision can reach 0.2% through the verification of practical products, and the invention has the functions of primary open circuit detection and the like.
3. The signal conditioning circuit and the signal conditioning method for the rotary transformer are mainly applied to multi-type aircraft engine full-authority digital electronic controller products, various engine system test verifications and airplane installation verifications are carried out, the system is stable and reliable in operation, accurate acquisition of position information of the rotary transformer can be achieved, and the decoding method provided by the invention ensures the real-time performance of the system.
Drawings
FIG. 1 is a functional block diagram of a resolver conditioning circuit of the present invention;
FIG. 2 is a schematic block diagram of the excitation circuit of the present invention;
FIG. 3 is a circuit diagram of the excitation circuit of the present invention;
FIG. 4 is a schematic diagram of the primary open circuit detection circuit of the present invention;
FIG. 5 is a schematic diagram of a lossless full-wave rectifier circuit of the present invention;
FIG. 6 is a hardware schematic of a lossless full-wave rectifier circuit according to the present invention;
FIG. 7 is a hardware schematic of the filter circuit of the present invention;
FIG. 8 is a flow chart of a decoding method of the present invention;
Detailed Description
The present invention will be further explained with reference to the accompanying drawings and embodiments, in which the excitation frequency of a rotary transformer of a certain type is required to be 3000Hz + -50 Hz, the amplitude is required to be 7.07Vrms + -0.14 Vrms, the DC impedance of the primary coil is 56 Ω + -5.6 Ω, and the transformation coefficient T isR0.492 ± 0.025, and the rotation angle theta is in the range of (-33.2 to 85.5 °).
The invention relates to a signal conditioning circuit of a rotary transformer, which has a functional schematic diagram shown in figure 1 and mainly comprises an excitation circuit, a primary open circuit detection circuit, a lossless full-wave rectification circuit, a filter circuit and a secondary open circuit detection circuit. The excitation circuit provides standard sinusoidal excitation drive for the rotary transformer; the primary open circuit detection circuit is connected with the excitation circuit and used for detecting the primary open circuit fault of the rotary transformer; a feedback signal SIN end and a COS end of the rotary transformer are respectively regulated by a lossless full-wave rectifying circuit and a filter circuit in sequence and then output direct-current voltage signals SIN _ DC and COS _ DC, and the direct-current voltage signals SIN _ DC and COS _ DC can obtain digital signals after passing through an AD acquisition circuit.
As shown in the schematic diagram of FIG. 2, the FPGA or MCU is used to read the standard sinusoidal data in the SIN _ ROM, and at regular time intervals, the current type D/A chip is controlled and a standard sinusoidal signal SIN _ AC (with frequency of 3KHz and effective value of 7.06V) is output via the I/V conversion circuit. The operational amplifiers D1 and C1 form an integrating circuit, the power triodes V1 and V2 form a push-pull amplifying circuit, R0 is a sampling resistor, the resistance value is 10 omega (precision: +/-1%), the resistance value of R1 is 100 omega (precision: +/-1%), the resistance value of R2 is 10k omega (precision: +/-1%), the capacitance value of the capacitor C1 is 120pF (precision: +/-5%), and an SIN _ EXC signal is an excitation signal for driving the rotary transformer. The specific circuit is shown in fig. 3 and comprises an FPGA or an MCU, a current type DA chip, an I/V conversion circuit and a drive circuit; the FPGA or the MCU controls a current type DA chip, the output of the current type DA chip is connected to the input end of the I/V conversion circuit, and the output end of the I/V conversion circuit is connected with the driving circuit; the driving circuit comprises an integrating circuit consisting of an operational amplifier D1 and a capacitor C1, a push-pull amplifying circuit consisting of a resistor R1, a triode V1 and a triode V2, a sampling resistor R0 and a feedback resistor R2; the output end of the I/V conversion circuit is connected with the positive input end of an operational amplifier D1, two ends of a capacitor C1 are respectively connected with the negative input end and the output end of the operational amplifier D1, the output end of the operational amplifier D1 is simultaneously connected with a triode V1, the base of a transistor V2 and one end of a resistor R1, the other end of the resistor R1 is simultaneously connected with an emitter of a triode V1 and a transistor V2 and one end of a resistor R0, collectors of the triode V1 and the transistor V2 are respectively connected with a positive power supply and a negative power supply, and two ends of a resistor R2 are respectively connected with the negative input end of the operational amplifier D1 and the other end of the resistor R0; two input ends of the primary open circuit detection circuit are respectively connected with two ends of the R0.
FIG. 4 is a schematic diagram of the primary open circuit detection circuit, which includes an operational amplifier D2, resistors R3-R11, a diode V3, a capacitor C2 and a voltage comparator; one end of the resistor R3 and one end of the resistor R4 are respectively connected to two ends of the sampling resistor R0, and the other ends of the resistors are respectively connected with the negative input end and the positive input end of the operational amplifier D2; two ends of the resistor R5 are respectively connected with the negative input end and the output end of the operational amplifier D2; the two ends of the resistor R6 are connected with the ground and the positive input end of the operational amplifier D2; the positive end of a diode V3 is connected with the output end of an operational amplifier D2, the negative end of a diode V3 is connected with the negative input end of a voltage comparator through a resistor R7, the two ends of the resistor R9 and a capacitor C2 are connected with the negative input ends of the ground and the voltage comparator, the two ends of a resistor R8 are connected with a voltage reference V _ REF and the positive input end of the voltage comparator, and the two ends of a resistor R10 are respectively connected with the ground and the positive input end of the voltage comparator; the resistor R11 is a pull-up resistor at the output end of the voltage comparator, and two ends of the resistor R11 are respectively connected with the power supply VCC and the output end of the voltage comparator. The voltage drop across the sampling resistor R0 is amplified by a differential proportional amplifier circuit composed of resistors R3, R4, R5, R6 and an operational amplifier D2, rectified by a diode V3, and finally divided by R7, R9 and a capacitor C2 and filtered to obtain a dc signal, which is connected to the negative input terminal of the voltage comparator, +5VDC is connected to the positive input terminal of the voltage comparator via voltage dividing resistors R8 and R10, where R3 equals to R4 equals to 4K Ω (accuracy: ± 0.1%), R5 equals to 200K Ω (accuracy: ± 0.1%), the differential proportional amplifier circuit amplifies K equals to 50, R7 equals to 20K Ω (accuracy: ± 1%), R9 equals to 100K Ω (accuracy:1%), R8 equals to 5K: + 5K% (accuracy: + 1), the differential proportional amplifier circuit amplifies K equals to 50, R7 equals to 20K Ω (accuracy: ± 1%), the voltage drop across the sampling resistor R2: + 1), and the voltage drop across the primary resistor R2: + 24: +5 nF 5, at the moment, the negative input end of the voltage comparator is larger than the positive input end, and the comparator outputs low level; when the primary of the rotary transformer has an open-circuit fault, no voltage drop exists at two ends of the sampling resistor R0, at the moment, the negative input end of the voltage comparator is smaller than the positive input end, and the comparator outputs a high level; the system may indicate that an open circuit fault has occurred.
FIG. 5 is a schematic diagram of a lossless full-wave rectifier circuit for inputting an AC signal uinSimultaneously connected to the input end of the phase-inverting circuit and the B end of the analog single-pole double-throw switch, the A end of the analog single-pole double-throw switch is connected with the output end of the phase-inverting circuit, and when the control signal u of the single-pole double-throw switch is usedcAt low level, uinThe inverted signal is output to a pin D through a pin A; when the control signal ucWhen it is at high level, u isinAnd output to the D pin through the B pin. If the control signal ucIs in direct contact with an input AC signal uinFully synchronous square waves, i.e. at uinWhen the voltage is in the positive half cycle, the control signal is high level, and the pin D outputs a signal uoIs uinA positive half cycle signal; at uinAt negative half cycle, the control signal ucAt low level, pin D outputs signal uoIs uinNegative half cycle of inverted signal. In summary, the output signal uoFor an input signal uinIs output by full-wave rectification. FIG. 6 is a schematic diagram of the hardware of a lossless full-wave rectifier circuit, in which the resistors R12, R13, R14 and the operational amplifier D3 form an inverter circuit, and the specification of the single-pole double-throw switch element is ADG436, where R12 ═ R13 ═ 10K Ω (precision: ± 0.1%), and R14 ═ 5K Ω (precision: ±. 1%).
Fig. 7 is a hardware schematic diagram of a filter circuit, and a full-wave rectifier circuit is implemented based on an analog on-off effect of a switch, so that an output signal includes higher harmonics and switching noise. The common RC low-pass filter can filter out higher harmonics but can not thoroughly filter out switching noise, so the mode of cascading the RC low-pass filter and a second-order infinite gain multi-path feedback low-pass filter is adopted to filter out the higher harmonics and the switching noise. Where R15 ═ R16 ═ 20K Ω (accuracy: ± 1%), R17 ═ R18 ═ 40K Ω (accuracy: ± 1%), capacitance C3 ═ 100nF (accuracy: ± 5%), C4 ═ 33nF (accuracy: ± 5%), then the low-pass filter cut-off frequency is:
Figure GDA0003200575390000071
the cut-off frequency of the second-order infinite gain multi-path feedback low-pass filter is as follows:
Figure GDA0003200575390000072
the invention can also realize secondary open circuit detection, the function of the secondary open circuit detection is realized without a separate hardware circuit, and the detection can be realized by judging the direct current voltage values of the SIN end and the COS end of the conditioned feedback signal of the rotary transformer, and because of the working principle of the rotary transformer, the sum of the square of the direct current voltage of the SIN end and the square of the direct current voltage of the COS end is a constant value, namely SIN _ DC2+COS_DC2≈TR*7.072Approximately equal to 24.5, when the DC voltage value of the SIN end or the COS end is close to 0, and the SIN _ DC is equal to zero2+COS_DC2<20, it can prompt open circuit fault of SIN end or COS end.
The SIN _ DC and the COS _ DC obtained by the resolver conditioning circuit provided by the invention can obtain the size of the rotation angle theta of the resolver through arc tangent operation. The flow chart of the arc tangent method proposed by the invention is shown in fig. 8, the theta in the range of-90 degrees to +90 degrees is reduced to-15 degrees to +15 degrees through a tangent sum difference formula, the fitting formula theta is fitted in the range of-15 degrees to +15 degrees by using an arc tangent function, namely, tan (theta) (a tan (theta) + b ]/[ tan (theta) + c ], and finally the range of [ -15 degrees and +15 degrees ] is restored to [ -90 degrees and +90 degrees ]. The specific process is as follows:
step 1: calculating a tangent value tan (theta) of a rotating angle theta of the rotary transformer according to direct-current voltages of an SIN end and a COS end output by the rotary transformer conditioning circuit, wherein the tangent value tan (theta) is SIN _ DC/COS _ DC, and setting the flag positions r0, r1 and r2 to be zero;
step 2: if tan (θ) <0, let tan (θ) equal to-tan (θ), and put r0 equal to 1;
and step 3: if tan (θ) > tan (45 °), let tan (θ) equal to tan (90 ° - θ), and put r1 equal to 1;
and 4, step 4: if tan (θ) > tan (15 °), let tan (θ) equal to tan (θ -30 °), and put r2 equal to 1;
and 5: the value of the resolver rotation angle θ is obtained using a fitting formula θ ═ tan (θ) × [ a × (θ) × tan (θ) + b ]/[ tan (θ) × tan (θ) + c ], where a ═ 0.4378, b ═ 1.6867, and c ═ 1.6867. At this time, θ is an arc value, and needs to be changed into an angle value.
In order to verify the correctness of the fitting formula, when a, b and c retain 10-bit effective numbers, 7 points are selected within the range of [ -15, +15 DEG ] for verification, and when the angle is +/-15 DEG, the maximum error is 0.000004 DEG, so that the error brought by the fitting formula of the arctangent function to the signal conditioning of the rotary transformer is negligible.
Step 6: if r2 is equal to 1, θ is equal to θ +30 °;
and 7: if r1 is equal to 1, then θ is equal to 90 ° - θ;
and 8: if r0 is 1, then θ is- θ;
and step 9: and theta is the rotation angle position information of the rotary transformer.
In actual work, the invention has been subjected to various system test verifications and installation verifications, the system is stable and reliable in operation, accurate signal acquisition of the rotary transformer can be realized, and a primary open circuit detection function can be realized.

Claims (7)

1. A resolver signal conditioning circuit, characterized in that: the circuit comprises an excitation circuit, a primary open circuit detection circuit, 2 paths of lossless full-wave rectification circuits, 2 paths of filter circuits, 2 paths of AD acquisition circuits and 1 CPU;
the excitation circuit provides standard sinusoidal excitation drive for the rotary transformer; the primary open circuit detection circuit is connected with the excitation circuit and used for detecting the primary open circuit fault of the rotary transformer; the feedback signal SIN end and the COS end of the rotary transformer are respectively regulated by a lossless full-wave rectifying circuit and a filter circuit in sequence and then output direct-current voltage signals SIN _ DC and COS _ DC, and the direct-current voltage signals SIN _ DC and COS _ DC can obtain digital signals after passing through an AD acquisition circuit;
the CPU stores a decoding program that, when executed, implements the following processes:
step 1: setting the flag positions r0, r1 and r2 to zero, receiving the AD acquisition results SIN _ DC and COS _ DC, and obtaining a tangent value tan (theta) of a rotating angle theta of the rotary transformer according to the SIN _ DC and the COS _ DC;
step 2: if tan (θ) <0, let tan (θ) equal to-tan (θ), and put r0 equal to 1;
and step 3: if tan (θ) > tan (45 °), let tan (θ) equal to tan (90 ° - θ), and put r1 equal to 1;
and 4, step 4: if tan (θ) > tan (15 °), let tan (θ) equal to tan (θ -30 °), and put r2 equal to 1;
and 5: obtaining the value of the rotating transformer rotating angle theta by using a fitting formula theta ═ tan (theta) × [ a × (theta) × tan (theta) + b ]/[ tan (theta) × tan (theta) + c ], wherein a, b and c are obtained through simulation tests and are all constant values;
step 6: if r2 is equal to 1, θ is equal to θ +30 °;
and 7: if r1 is equal to 1, then θ is equal to 90 ° - θ;
and 8: if r0 is 1, then θ is- θ;
and step 9: and theta is the rotation angle position information of the rotary transformer.
2. The resolver signal conditioning circuit according to claim 1, wherein: constant value a is in the range of 0.4-0.5, constant value b is in the range of 1.6-1.7, constant value c is in the range of 1.6-1.7, and all of a, b and c need to reserve 10 significant digits.
3. The resolver signal conditioning circuit according to claim 1, wherein: the excitation circuit comprises an FPGA or an MCU, a current type DA chip, an I/V conversion circuit and a drive circuit; the FPGA or the MCU controls a current type DA chip, the output of the current type DA chip is connected to the input end of the I/V conversion circuit, and the output end of the I/V conversion circuit is connected with the driving circuit;
the driving circuit comprises an integrating circuit consisting of an operational amplifier D1 and a capacitor C1, a push-pull amplifying circuit consisting of a resistor R1, a triode V1 and a transistor V2, a sampling resistor R0 and a feedback resistor R2; the output end of the I/V conversion circuit is connected with the positive input end of an operational amplifier D1, two ends of a capacitor C1 are respectively connected with the negative input end and the output end of the operational amplifier D1, the output end of the operational amplifier D1 is simultaneously connected with a triode V1, the base of a transistor V2 and one end of a resistor R1, the other end of the resistor R1 is simultaneously connected with an emitter of a triode V1 and a transistor V2 and one end of a resistor R0, collectors of the triode V1 and the transistor V2 are respectively connected with a positive power supply and a negative power supply, and two ends of a resistor R2 are respectively connected with the negative input end of the operational amplifier D1 and the other end of the resistor R0; two input ends of the primary open circuit detection circuit are respectively connected with two ends of the R0.
4. A resolver signal conditioning circuit according to claim 3, wherein: the primary open circuit detection circuit comprises an operational amplifier D2, resistors R3-R11, a diode V3, a capacitor C2 and a voltage comparator; one end of the resistor R3 and one end of the resistor R4 are respectively connected to two ends of the sampling resistor R0, and the other ends of the resistors are respectively connected with the negative input end and the positive input end of the operational amplifier D2; two ends of the resistor R5 are respectively connected with the negative input end and the output end of the operational amplifier D2; the two ends of the resistor R6 are connected with the ground and the positive input end of the operational amplifier D2; the positive end of a diode V3 is connected with the output end of an operational amplifier D2, the negative end of a diode V3 is connected with the negative input end of a voltage comparator through a resistor R7, the two ends of the resistor R9 and a capacitor C2 are connected with the negative input ends of the ground and the voltage comparator, the two ends of a resistor R8 are connected with a voltage reference V _ REF and the positive input end of the voltage comparator, and the two ends of a resistor R10 are respectively connected with the ground and the positive input end of the voltage comparator; the resistor R11 is a pull-up resistor at the output end of the voltage comparator, and two ends of the resistor R11 are respectively connected with the power supply VCC and the output end of the voltage comparator.
5. The resolver signal conditioning circuit according to claim 4, wherein: the lossless full-wave rectification circuit consists of an inverting circuit and a simulation single-pole double-throw switch; the input AC signal is simultaneously connected to the input end of the inverter circuit and the B end of the analog single-pole double-throw switch, the A end of the analog single-pole double-throw switch is connected with the output end of the inverter circuit, and the control signal ucAnd is connected with the control end of the analog single-pole double-throw switch.
6. The resolver signal conditioning circuit according to claim 5, wherein the filtering circuit comprises an RC low-pass filter and a second-order infinite-gain multi-feedback low-pass filter connected in series.
7. A method for conditioning a resolver signal conditioning circuit according to any of claims 1 to 6, comprising the steps of:
the method comprises the following steps that firstly, an FPGA or an MCU controls a current type D/A chip and outputs a standard sine waveform through an I/V conversion circuit by reading standard sine data in an SIN _ ROM, and the standard sine waveform generates sine wave excitation with driving capability after passing through a negative feedback driving circuit formed by an integrating circuit and a push-pull amplifying circuit;
step two, sine wave excitation is applied to a rotary transformer, sine signals and cosine signals output by a secondary side of the rotary transformer are alternating current signals, and sine and cosine direct current voltage signals SIN _ DC and COS _ DC are obtained after the alternating current signals are respectively subjected to lossless full-wave rectification and a filter circuit;
step three, when the lossless full-wave rectification and filtering circuit works, the primary open-circuit detection circuit constantly monitors the voltage drop at two ends of a sampling resistor R0 in the excitation circuit, and whether a primary open-circuit fault occurs is judged; when voltage drop exists at the two ends of the sampling resistor, the fact that open-circuit fault does not occur is indicated; when no voltage drop exists at the two ends of the sampling resistor, an open-circuit fault is prompted to occur;
step four, obtaining a digital signal by the direct-current voltage signal SIN _ DC and the direct-current voltage signal COS _ DC through an AD acquisition circuit; the CPU stores a decoding program that, when executed, implements the following processes:
step 4-1: setting the flag positions r0, r1 and r2 to zero, receiving the AD acquisition results SIN _ DC and COS _ DC, and obtaining a tangent value tan (theta) of a rotating angle theta of the rotary transformer according to the SIN _ DC and the COS _ DC;
step 4-2: if tan (θ) <0, let tan (θ) equal to-tan (θ), and put r0 equal to 1;
step 4-3: if tan (θ) > tan (45 °), let tan (θ) equal to tan (90 ° - θ), and put r1 equal to 1;
step 4-4: if tan (θ) > tan (15 °), let tan (θ) equal to tan (θ -30 °), and put r2 equal to 1;
and 4-5: obtaining the value of the rotating transformer rotating angle theta by using a fitting formula theta ═ tan (theta) × [ a × (theta) × tan (theta) + b ]/[ tan (theta) × tan (theta) + c ], wherein a, b and c are obtained through simulation tests and are all constant values;
and 4-6: if r2 is equal to 1, θ is equal to θ +30 °;
and 4-7: if r1 is equal to 1, then θ is equal to 90 ° - θ;
and 4-8: if r0 is 1, then θ is- θ;
and 4-9: and theta is the rotation angle position information of the rotary transformer.
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