CN114740217B - Method and device for measuring rotating speed of starting and launching integrated aircraft engine - Google Patents
Method and device for measuring rotating speed of starting and launching integrated aircraft engine Download PDFInfo
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- CN114740217B CN114740217B CN202210378214.7A CN202210378214A CN114740217B CN 114740217 B CN114740217 B CN 114740217B CN 202210378214 A CN202210378214 A CN 202210378214A CN 114740217 B CN114740217 B CN 114740217B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
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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
- F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
- F02C7/26—Starting; Ignition
- F02C7/268—Starting drives for the rotor, acting directly on the rotor of the gas turbine to be started
- F02C7/275—Mechanical drives
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/17—Circuit arrangements for detecting position and for generating speed information
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
- H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Abstract
The invention discloses a method for measuring the rotating speed of an initiating and launching integrated aero-engine, wherein the initiating and launching integrated aero-engine comprises a brushless direct current motor which is coaxially and fixedly connected with the aero-engine and a motor control circuit which controls the brushless direct current motor based on a six-step commutation method, and the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switching tubes and a driving circuit thereof; sampling a direct current bus current in a motor control circuit and simultaneously measuring a first motor rotating speed and a second motor rotating speed of the brushless direct current motor; and comparing the direct current bus current sampling value with a preset threshold, and outputting the rotating speed of the first motor as the rotating speed of the aircraft engine when the direct current bus current sampling value is smaller than the threshold, or outputting the rotating speed of the second motor as the rotating speed of the aircraft engine. The invention also discloses a device for measuring the rotating speed of the starting integrated aircraft engine. Compared with the prior art, the invention does not need a sensor and can simultaneously meet the speed measurement accuracy of the motor state and the generator state.
Description
Technical Field
The invention relates to the technical field of aero-engine control, in particular to a method and a device for measuring the rotating speed of an initiating integrated aero-engine.
Background
In the control of an aircraft engine, the engine speed is a very important controlled quantity, the control of the engine is essentially the control of the engine speed, and the engine speed is also an important parameter for evaluating the performance of the engine. Therefore, the accuracy and stability of the rotation speed measurement directly affect the control effect of the engine.
In the design of the starting integrated aero-engine, a brushless direct current motor (BLDC) is usually adopted as a starting generator, the aero-engine is fixedly connected with a rotating shaft of the BLDC, the BLDC drags blades of the aero-engine to rotate to accelerate airflow to enter a gas path so as to supply oxygen to a combustion chamber when the BLDC is started, and the BLDC drags the BLDC to output electric energy outwards when the aero-engine runs. Because the starting generator for starting the integrated aircraft engine is fixedly connected with the engine, the rotating speed of the aircraft engine can be indirectly obtained by measuring the rotating speed of the brushless direct current motor.
At present, the speed measuring methods for the brushless direct current motor under two running states are as follows: 1) The photoelectric mechanical sensor comprises: for example, CN205539027U, CN214703899U, CN108683368A, etc., rely on sensors for measuring the rotation speed, which is complicated in structure and increases the volume of the motor. 2) Back electromotive force test method: for example, in patents CN105634341A, CN101877566A, etc., it relies on collecting three-phase voltage to convert into PWM signal, and this method is relatively stable in the generator state, but the problems of high frequency noise, flyback voltage, electromagnetic interference around a high current conducting wire, etc. are serious in the motor state, and it is very unstable in practical tests, especially difficult to capture PWM signal in low rotation speed, and the distortion of output signal is serious. 3) The speed measurement chip is changed into the algorithm: for example, CN102916630A, the method mainly converts three-phase voltage into rotor position signal to obtain the motor rotation speed, and the method is more suitable for measuring the rotor position of a brushless dc motor and needs to rely on a motor position sensor. 4) Hall sensor logic operation: for example, CN110417310B, CN111654210A, etc., the method uses hall sensor and MOSFET driving logic to calculate the rotation speed in two states of motor and generator, the method has complex logic operation and weak anti-interference capability, when the sensor fails or receives serious interference, the complex logic operation will output wrong signal to seriously affect the control effect, and the sensorless has large volume, and is not suitable for being used as the starter of the starting integrated aeroengine.
For starting an integrated aircraft engine, the starting motor is always expected to be smaller and better, and the engine assembly difficulty and the air inlet passage air circulation rate are seriously increased due to the overlarge volume; secondly, a Hall sensor, an encoder, a position sensor and the like are selected in a general speed measurement method, but the uncertainty of the working condition of an aeroengine during air flight is large, the sensor can possibly malfunction under the conditions of vibration, high temperature and the like, the problem of electromagnetic interference needs to be considered in military application, and the requirement on the stability of the sensor and the fixity during assembly is high; therefore, a sensorless tachometric scheme is preferred. The existing brushless direct current motor speed measurement scheme can not meet the speed measurement requirement of the starting integrated aero-engine because a sensor is required or the speed measurement accuracy of the state of a motor and the state of a generator can not be considered at the same time.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for measuring the rotating speed of an initiating integrated aircraft engine.
The invention specifically adopts the following technical scheme to solve the technical problems:
a method for measuring the rotating speed of an initiating integrated aero-engine comprises the steps that the initiating integrated aero-engine comprises a brushless direct current motor which is coaxially and fixedly connected with the aero-engine and a motor control circuit which controls the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switching tubes and a driving circuit of the three-phase inverter bridge; sampling direct current bus current in a motor control circuit and simultaneously measuring a first motor rotating speed and a second motor rotating speed of the brushless direct current motor; comparing a direct current bus current sampling value with a preset threshold value, and outputting the rotating speed of the first motor as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the threshold value, or outputting the rotating speed of the second motor as the rotating speed of the aero-engine; the rotating speed of the second motor is measured according to the back electromotive force of the brushless direct current motor; the rotating speed of the first motor is obtained by the following method: driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (a _ H ≠ B _ L) — (B _ H ≠ C _ L) — (C _ H ≧ a _ L), then the three-frequency division processing is performed on the generated output signal T and the rising edge of the high level of the generated three-frequency division signal is made to be in phase with the rising edge of the driving signal a _ L, and finally the first motor rotation speed of the brushless dc motor is calculated with the period of the three-frequency division signal as the electrical period of the brushless dc motor.
Based on the same inventive concept, the following technical scheme can be obtained:
a starting integrated aero-engine rotating speed measuring device comprises a brushless direct current motor coaxially and fixedly connected with an aero-engine and a motor control circuit for controlling the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge composed of 6 power switching tubes and a driving circuit thereof; the rotation speed measuring device includes:
a first motor speed measuring unit for measuring a first motor speed of the brushless dc motor by using: for the driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (a _ H ≠ B _ L) ueu (B _ H ≠ C _ L) ueu (C _ H ═ a _ L), then the generated output signal T is subjected to three-frequency division processing, the rising edge of the high level of the generated three-frequency division signal is made to be in phase with the rising edge of the driving signal a _ L, and finally the period of the three-frequency division signal is taken as the electrical period of the brushless dc motor to calculate the first motor rotating speed of the brushless dc motor;
the second motor rotating speed measuring unit is used for measuring the second motor rotating speed of the brushless direct current motor according to the back electromotive force of the brushless direct current motor;
and the motor state judging and automatic switching module is used for sampling the direct current bus current in the motor control circuit, comparing the direct current bus current sampling value with a preset threshold value, and outputting the rotating speed of the first motor as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the threshold value, or outputting the rotating speed of the second motor as the rotating speed of the aero-engine.
Preferably, the first motor rotating speed measuring unit comprises a logic circuit, a ternary counter and a voltage comparator; the output end of the logic circuit is connected with the clock signal input end of the ternary counter and the positive input end of the voltage comparator, the output end of the ternary counter is connected with the negative input end of the voltage comparator, and the output end of the voltage comparator is used as the output end of the first motor rotating speed measuring unit.
Further preferably, the logic circuit includes first to ninth diodes and first to fourth resistors; the cathodes of the first to sixth diodes are correspondingly connected with A _ H, B _ L, B _ H, C _ L, C _ H and A _ L one by one, the anode of the first diode and the anode of the second diode are simultaneously connected with one end of the first resistor and the anode of the seventh diode, the anode of the third diode and the anode of the fourth diode are simultaneously connected with one end of the second resistor and the anode of the eighth diode, the anode of the fifth diode and the anode of the sixth diode are simultaneously connected with one end of the third resistor and the anode of the ninth diode, the other end of the first resistor, the other end of the second resistor and the other end of the third resistor are respectively connected with a working power supply, one end of the fourth resistor is simultaneously connected with the cathode of the seventh diode, the cathode of the eighth diode and the cathode of the ninth diode and is used as the output end of the logic circuit, and the other end of the fourth resistor is grounded.
Preferably, the second motor rotation speed measuring unit includes: the system comprises an N-type MOSFET, a P-type MOSFET, an operational amplifier, two voltage reduction circuits with the same reduction proportion and a virtual zero point with the electric potential approximately equal to 1/2 times of the bus voltage; the input end of one of the voltage reducing circuits is connected with the virtual zero, and the output end of the voltage reducing circuit is connected with the inverting input end of the operational amplifier; the input end of the other voltage reducing circuit is connected with one phase of the brushless direct current motor, and the output end of the other voltage reducing circuit is simultaneously connected with the grid electrode of the N-type MOSFET and the grid electrode of the P-type MOSFET; the source electrode of the N-type MOSFET and the source electrode of the P-type MOSFET are simultaneously connected with the non-inverting input end of the operational amplifier, the drain electrode of the N-type MOSFET is connected with the working power supply, and the drain electrode of the P-type MOSFET is grounded.
Compared with the prior art, the invention has the following beneficial effects:
the invention aims at the problem of measuring the rotating speed of the starting integrated aircraft engine, and indirectly obtains the rotating speed of the aircraft engine by measuring the rotating speed of the brushless direct current motor.
Drawings
FIG. 1 is a schematic block diagram of one embodiment of an apparatus for measuring the rotational speed of an aircraft engine according to the present invention;
FIG. 2 is a diagram of a motor control circuit in an exemplary embodiment;
FIG. 3 is a circuit diagram of a motor state determination module in an exemplary embodiment;
FIG. 4 is a circuit diagram of a first motor speed measurement unit (motor mode) in an exemplary embodiment;
FIG. 5 is a circuit diagram of a second motor speed measurement unit (generator mode) in an exemplary embodiment;
fig. 6 is a circuit diagram of an auto-switching module in an embodiment.
Detailed Description
Aiming at the problem of measuring the rotating speed of the starting integrated aircraft engine, the solution of the invention is to indirectly obtain the rotating speed of the aircraft engine by measuring the rotating speed of the brushless direct current motor based on the structural characteristic that the aircraft engine is fixedly connected with the rotating shaft of the brushless direct current motor, so that the problem is converted into the problem of measuring the rotating speed of the sensorless brushless direct current motor.
The brushless direct current motor on the starting integrated aircraft engine has the following characteristics: the method has the advantages that the method does not need very accurate rotating speed control, has short duration, large moment and strong current in the state of the motor, and needs to drive the blades to reach higher rotating speed in a short time; after the engine is ignited successfully, the output of the motor is reduced rapidly due to the work of the fuel oil, so that the state of the motor is changed into the state of the generator rapidly, and the range of the back electromotive force amplitude of the motor in the state of the generator is large. Three difficulties are presented here: (1) How to distinguish the state of the motor from the state of the generator and carry out synchronous speed measurement; (2) Under the condition of not increasing software algorithm and motor cost, how to seek to realize sensorless speed measurement in an optimal speed measurement method under different running states, especially in a brushless direct current motor driving circuit, the motor input is a PWM wave, and the software control logic is unknown; (3) How to measure the speed in the whole process is that the speed is continuously measured without software or manual switching of a motor speed measuring method and a generator speed measuring method, the range of the counter electromotive force amplitude is large in the state of the generator, the limitation cannot be realized by adopting fixed resistor voltage division, and how to limit the counter electromotive force amplitude of the motor is required.
In order to solve the problems, the invention provides a method for measuring the rotating speed of an initiating integrated aero-engine, which comprises the following steps: the starting integrated aero-engine comprises a brushless direct current motor coaxially and fixedly connected with the aero-engine and a motor control circuit for controlling the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switching tubes and a driving circuit thereof; sampling a direct current bus current in a motor control circuit and simultaneously measuring a first motor rotating speed and a second motor rotating speed of the brushless direct current motor; comparing a direct current bus current sampling value with a preset threshold value, and outputting the rotating speed of the first motor as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the threshold value, or outputting the rotating speed of the second motor as the rotating speed of the aero-engine; the rotating speed of the second motor is measured according to the back electromotive force of the brushless direct current motor; the first motor rotating speed is obtained by the following method: driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (a _ H ≠ B _ L) — (B _ H ≠ C _ L) — (C _ H ≧ a _ L), then the three-frequency division processing is performed on the generated output signal T and the rising edge of the high level of the generated three-frequency division signal is made to be in phase with the rising edge of the driving signal a _ L, and finally the first motor rotation speed of the brushless dc motor is calculated with the period of the three-frequency division signal as the electrical period of the brushless dc motor.
The starting integrated aero-engine rotating speed measuring device comprises a brushless direct current motor coaxially and fixedly connected with an aero-engine and a motor control circuit for controlling the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switching tubes and a driving circuit thereof; the rotation speed measuring device includes:
a first motor speed measuring unit for measuring a first motor speed of the brushless DC motor by using the following method: for the driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (A _ H ≠ B _ L) — (B _ H ≠ C _ L) — (C _ H: _ A _ L), then the generated output signal T is subjected to three-frequency division processing, the rising edge of the high level of the generated three-frequency division signal is in phase with the rising edge of the driving signal A _ L, and finally the period of the three-frequency division signal is taken as the electric period of the brushless direct current motor to calculate the first motor rotating speed of the brushless direct current motor;
the second motor rotating speed measuring unit is used for measuring the second motor rotating speed of the brushless direct current motor according to the back electromotive force of the brushless direct current motor;
and the motor state judging and automatic switching module is used for sampling the direct current bus current in the motor control circuit, comparing the direct current bus current sampling value with a preset threshold value, and outputting the rotating speed of the first motor as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the threshold value, or outputting the rotating speed of the second motor as the rotating speed of the aero-engine.
For the public understanding, the technical scheme of the invention is explained in detail by a specific embodiment and the accompanying drawings:
in the embodiment, the starter generator in the starting integrated aircraft engine is a brushless direct current motor, the control framework of the motor control circuit is shown as a dotted line frame at the upper middle part of fig. 1, the electronic controller controls the PWM controller to generate a PWM signal through a PID algorithm according to a given rotating speed and an actual rotating speed, and controls the commutation of the three-phase inverter bridge through collecting three opposite electromotive forces and a zero-crossing comparison method based on a six-step commutation method. The basic structure of the rotation speed measuring device in this embodiment is shown as a dashed line frame in the middle lower part of fig. 1, and the basic structure is used for respectively collecting bus current of a three-phase inverter bridge, six MOSFET driving signals and motor three-phase voltage, and then respectively inputting the bus current, the six MOSFET driving signals and the motor three-phase voltage into a motor state judging and automatic switching module, a motor state speed measuring unit and a generator state speed measuring unit.
As shown in fig. 1, the motor state speed measuring unit includes a logic circuit, a ternary counter, and a voltage comparator; the logic circuit is used for driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (a _ H ≠ B _ L) ueu (B _ H ≠ C _ L) ueu (C _ H ═ a _ L), whose output is simultaneously connected to the clock signal input terminal of the ternary counter and the positive input terminal of the voltage comparator, the output terminal of the ternary counter is connected to the negative input terminal of the voltage comparator, the output terminal of the voltage comparator is used as the output terminal of the first motor speed measuring unit, and the ternary counter and the voltage comparator function to divide the generated output signal T three times and make the high level rising edge of the generated three-times divided signal in phase with the rising edge of the driving signal a _ L, so that the period of the square wave signal output by the voltage comparator is the electric period of the brushless dc motor in the motor state, thereby calculating the motor speed of the brushless dc motor in the motor state.
The generator state speed measurement unit consists of a clamping circuit and a hysteresis comparator, the three-phase voltage of the motor is connected in a star connection mode, and a virtual zero point formed by star connection is used as a reference potential of the hysteresis comparator; the method comprises the steps that C-phase voltage is collected and connected to the positive end of a hysteresis comparator after passing through a clamping circuit, when the phase voltage generates a complete trapezoidal wave (the waveform is transited from negative voltage to positive voltage), a square wave signal is output by the output end of the hysteresis comparator, the period of the square wave signal is equal to the phase voltage period, namely the electric period, and accordingly the motor rotating speed of the brushless direct current motor in the state of a generator can be calculated.
The motor state judging and automatic switching module consists of a current collecting chip, a peripheral circuit of the current collecting chip, a voltage comparator and an electronic switch synchronizer, and is used for comparing a direct current bus current sampling value with a preset threshold value, and outputting a speed measuring result of the motor state speed measuring unit as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the preset threshold value, or outputting the speed measuring result of the generator state speed measuring unit as the rotating speed of the aero-engine.
In this embodiment, as shown in fig. 2, the motor control circuit is composed of two modules, one is a switching circuit, which is used to adjust the effective value of the input voltage of the three-phase inverter bridge so as to control the rotation speed of the motor; and the second is a three-phase inverter bridge, which adopts a six-step commutation method to drive a brushless direct current motor. The P-type triode Q7 and the P-type MOS transistor Q8 form a PWM output circuit, and the effective value of the input voltage of the three inverter bridges can be controlled by controlling the on-off of the Q7, so that the rotating speed of the motor is controlled; the back-stage circuit is a three-phase full-control inverter bridge, the bus is connected with a diode and a sampling resistor in series, the diode is used for preventing the power supply from being burnt out due to the overlarge induced electromotive force of the motor, namely preventing reverse current from being injected into the power supply, and the sampling resistor is used for collecting the current of the bus so as to judge the running state of the motor.
The speed measuring scheme of the motor state speed measuring unit in the embodiment is different from that of CN102916630A, CN110417310B, CN111654210A and the like, and the speed measuring method in the state is that driving signals of six MOSFETs are collected to be input into a binary frequency division logic circuit, the six MOSFETs are numbered as A _ H, A _ L, B _ H, B _ L, C _ H and C _ L and are divided into three groups of A _ H and B _ L, B _ H and C _ L, C _ H and A _ H respectively. The logic of the three groups is:
T＝(A_H∩B_L)∪(B_H∩C_L)∪(C_H∩A_L)
the output of the logic circuit module is a square wave signal with a period of T, and the square wave signal is used as an input signal of the following three-frequency division logic circuit module. After passing through the three-frequency division module, a square wave signal with a period of T/3 is output, the period of the signal is equal to the electric period, namely p times of the rotating speed of the motor, p is the number of pole pairs of the motor, and the high-level rising edge of the square wave is in phase with the rising edge of the driving signal. The specific circuit is shown in fig. 3, and the reason why the six-frequency-division module is not directly adopted in the design of the circuit is to reserve a driving signal when a forward voltage is input, so as to be in phase with the output of the generator state speed measurement unit. The purpose of the division into three groups is to be used as the input of a ternary counter, the logic of which is shown in table 1, whereinThe first row represents one cycle of the six-step commutation, the first list represents the output levels for the corresponding index positions in fig. 3, with a digital 1 representing a logic level "high" and a digital 0 representing a logic level "low". The QA and QB are in NAND logic, namely when both QA and QB are output in high level, a low level is output to CLR, and the low level clears QA and QB immediately. QA, QB are followed by an OR gate, the output of which is connected to the negative terminal of a voltage comparator, the other terminal of which is connected to the counter clock input. At t in Table 1 4 The Speed _ M end outputs high level at the moment, and the duration of the high level is t 5 -t 4 And the square wave period is equal to the electrical period of the motor. In addition to the ternary counter being able to be the ternary division module in the present design, the D flip-flop or JK flip-flop can also implement ternary division, but considering that the more devices the greater the delay, the simplest ternary counter is used here as the ternary division module.
TABLE 1
| t 1 | t 2 | t 3 | t 4 | t 5 | t 6 | |
| Group A | 1 | 0 | 0 | 0 | 0 | 0 |
| Group B | 0 | 0 | 1 | 0 | 0 | 0 |
| Group C | 0 | 0 | 0 | 0 | 1 | 0 |
| |
1 | 1 | 0 | 0 | 0 | 0 |
| QB | 0 | 0 | 1 | 1 | 0 | 0 |
| |
1 | 1 | 1 | 1 | 0 | 0 |
| Is just | 1 | 0 | 1 | 0 | 1 | 0 |
The design idea of the generator state speed measurement unit in this embodiment is to collect three-phase electromotive force and compare with the zero crossing point to judge the rotation speed of the motor, when the rotation speed of the motor is higher and no longer absorbs power, the waveform of the counter electromotive force generated by the motor is relatively stable, trapezoidal waves with phases different by 120 degrees are generated by the three-phase counter electromotive force a, B and C, and the period of the trapezoidal waves can reflect the rotation speed of the motor. Different from the schemes of patents CN105634341A and CN101877566A, the design is not assisted by a position sensor and a tachogenerator. Firstly, a virtual zero point is designed as a reference point, then a certain phase of electromotive force is collected as comparison voltage, a square wave signal is output through a zero-crossing comparator module, and the period of the square wave signal is the electric period. The problem to be solved here is the problem of voltage fluctuation, and the potential of the virtual zero point fluctuates and the back electromotive voltage also fluctuates. In this embodiment, the circuit structure shown in fig. 4 is adopted, so that the problem of voltage jitter can be effectively solved. As shown in FIG. 4, a virtual zero point is first designed by the resistors R25, R26, R27, and the virtual zero point (the potential of the virtual zero point is approximately equal to 1/2 times of the bus voltage) is reduced by five times and then is inputted as the negative terminal of the voltage comparator. Similarly, a certain phase of the motor is reduced by the same times and input to Q14 and Q15, and the S pole of Q14 and the S pole of Q15The point potential keeps the virtual zero point potential when Q14 and Q15 are switched off based on the 'virtual short and virtual break' characteristic of the operational amplifier. Because the grid electrode and the source electrode have a certain potential difference when the MOSFET is conducted, the module can filter the jitter of the phase voltage around the virtual zero point, and the conducting voltage of the MOSFET is set to be U GS . When the C phase voltage is greater than the virtual zero potential U GS When the voltage is high, Q15 is conducted, the input of the positive end of the voltage comparator is 5V, and the output end of speed _Gis high level; when the C phase voltage is less than the virtual zero potential U GS When Q14 is turned on, the positive input of the voltage comparator is 0V, and the output of speed G is low. R29 serves to prevent shorting when Q14 is on. At this time, the Speed _ G terminal of the voltage comparator outputs a square wave signal with a period equal to the electrical period.
The circuit of the motor state judging module in this embodiment is shown in fig. 5, where the current collecting module uses a voltage collecting chip MAX4173 to collect bus current, and the current judges the operation state of the motor, so as to switch between different speed measuring methods. The calculation formula of the VCC _ out point potential is as follows:
VCC_out＝gain·((RS+)-(RS-))
wherein, gain is the chip fixed gain value.
VCC _ out reflects the capability of the motor to absorb power of a power supply, the output of the current acquisition module is connected with a voltage comparator, the reference potential can be changed by adjusting R10, when VCC _ out is smaller than the reference potential, namely when the bus current is smaller than a certain value, the motor can be considered not to absorb electric energy from a battery at the moment, and the running state of the motor can be considered to be switched from the motor to a generator state. The Choose point potential is high, which indicates that the motor is in a motor running state; the Choose point potential is low, and the motor is in a generator running state.
The circuit structure of the automatic switching module in this embodiment is shown in fig. 6, and the design idea is to control an electronic switching device according to a Choose point potential (high level or low level) of an output signal of the motor state judgment module, so as to switch a signal output channel.
As shown in fig. 6, the automatic switching module is composed of a transistor Q11, a P-type MOSFET Q12, and an N-type MOSFET Q13. The module can control a rotation speed signal given by a person, when the output potential of a Choose point of the motor running state judging module is high, Q11 is switched off, the grid electrodes of Q12 and Q13 are pulled down, Q12 is switched on and Q13 is switched off, and the rotation speed signal is given by the motor state speed measuring module; when the output potential of the Choose point of the motor running state judging module is low, Q11 is conducted, the grid electrodes of Q12 and Q13 are pulled high, then Q12 is turned off, Q13 is conducted, and a rotating speed signal is given by the motor state speed measuring module. The switching device uses an electronic switch to control the setting of an output signal, high-frequency low-voltage MOS tubes are required to be used for Q12 and Q13 which have higher requirements on the switching frequency, no matter a motor state speed measuring module or a generator speed measuring module outputs a square wave period, the square wave period is the electric period of a motor, the square wave frequency output by the switching device is assumed to be f, the rotating speed of an engine is assumed to be n, the number of pole pairs of a used brushless direct current motor is p, and then the rotating speed of the engine can be obtained through the following formula:
secondly, the motor state speed measuring unit of the embodiment gives a high level when the waveform of the phase C voltage of the motor is in a positive half cycle, and gives a low level when the waveform of the phase C voltage of the motor is in a negative half cycle, and the generator state speed measuring unit also gives a high level when the waveform of the phase C voltage of the motor is in a positive half shaft, and gives a low level when the waveform of the phase C voltage of the motor is in a negative half shaft. Therefore, smooth transition of the output of the rotating speed signal under two running states of the motor can be realized through the automatic switching module.
Claims (5)
1. A method for measuring the rotating speed of an initiating integrated aero-engine comprises the steps that the initiating integrated aero-engine comprises a brushless direct current motor which is coaxially and fixedly connected with the aero-engine and a motor control circuit which controls the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switching tubes and a driving circuit of the three-phase inverter bridge; the method is characterized in that the direct current bus current in a motor control circuit is sampled and the first motor rotating speed and the second motor rotating speed of the brushless direct current motor are measured simultaneously; comparing the current sampling value of the direct current bus with a preset threshold, and outputting the rotating speed of the first motor as the rotating speed of the aircraft engine when the current sampling value of the direct current bus is smaller than the threshold, or outputting the rotating speed of the second motor as the rotating speed of the aircraft engine; the rotating speed of the second motor is measured according to the back electromotive force of the brushless direct current motor; the first motor rotating speed is obtained by the following method: driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (a _ H ≠ B _ L) ueu (B _ H ≠ C _ L) ueu (C _ H ═ a _ L), then the generated output signal T is subjected to three-frequency division processing, the rising edge of the high level of the generated three-frequency division signal is made to be in phase with the rising edge of the driving signal a _ L, and finally the period of the three-frequency division signal is taken as the electric period of the brushless dc motor to calculate the first motor rotating speed of the brushless dc motor.
2. A starting integrated aircraft engine rotating speed measuring device comprises a brushless direct current motor coaxially and fixedly connected with an aircraft engine and a motor control circuit for controlling the brushless direct current motor based on a six-step commutation method, wherein the motor control circuit comprises a three-phase inverter bridge consisting of 6 power switch tubes and a driving circuit thereof; characterized in that the rotational speed measuring device comprises:
a first motor speed measuring unit for measuring a first motor speed of the brushless dc motor by using: driving signals of 6 power switching tubes of the three-phase inverter bridge: a _ H, A _ L, B _ H, B _ L, C _ H, C _ L perform the following logical operations: t = (A _ H ≠ B _ L) — (B _ H ≠ C _ L) — (C _ H: _ A _ L), then the generated output signal T is subjected to three-frequency division processing, the rising edge of the high level of the generated three-frequency division signal is in phase with the rising edge of the driving signal A _ L, and finally the period of the three-frequency division signal is taken as the electric period of the brushless direct current motor to calculate the first motor rotating speed of the brushless direct current motor;
the second motor rotating speed measuring unit is used for measuring the second motor rotating speed of the brushless direct current motor according to the back electromotive force of the brushless direct current motor;
and the motor state judging and automatic switching module is used for sampling the direct current bus current in the motor control circuit, comparing the direct current bus current sampling value with a preset threshold value, and outputting the rotating speed of the first motor as the rotating speed of the aero-engine when the direct current bus current sampling value is smaller than the threshold value, or outputting the rotating speed of the second motor as the rotating speed of the aero-engine.
3. The apparatus for measuring the rotational speed of an aircraft engine as a whole according to claim 2, wherein said first motor rotational speed measuring unit comprises a logic circuit, a ternary counter, a voltage comparator; the output end of the logic circuit is connected with the clock signal input end of the ternary counter and the positive input end of the voltage comparator, the output end of the ternary counter is connected with the negative input end of the voltage comparator, and the output end of the voltage comparator is used as the output end of the first motor rotating speed measuring unit.
4. The apparatus for measuring the rotational speed of an aircraft engine as defined in claim 3, wherein said logic circuit comprises first to ninth diodes and first to fourth resistors; the cathodes of the first to sixth diodes are correspondingly connected with A _ H, B _ L, B _ H, C _ L, C _ H and A _ L one by one, the anode of the first diode and the anode of the second diode are simultaneously connected with one end of the first resistor and the anode of the seventh diode, the anode of the third diode and the anode of the fourth diode are simultaneously connected with one end of the second resistor and the anode of the eighth diode, the anode of the fifth diode and the anode of the sixth diode are simultaneously connected with one end of the third resistor and the anode of the ninth diode, the other end of the first resistor, the other end of the second resistor and the other end of the third resistor are respectively connected with a working power supply, one end of the fourth resistor is simultaneously connected with the cathode of the seventh diode, the cathode of the eighth diode and the cathode of the ninth diode and is used as the output end of the logic circuit, and the other end of the fourth resistor is grounded.
5. The apparatus for measuring the rotational speed of an aircraft engine as set forth in claim 2, wherein the second motor rotational speed measuring unit comprises: the system comprises an N-type MOSFET, a P-type MOSFET, an operational amplifier, two voltage reduction circuits with the same reduction proportion and a virtual zero point with the electric potential approximately equal to 1/2 times of the bus voltage; the input end of one of the voltage reducing circuits is connected with a virtual zero point, and the output end of the voltage reducing circuit is connected with the inverting input end of the operational amplifier; the input end of the other voltage reducing circuit is connected with one phase of the brushless direct current motor, and the output end of the other voltage reducing circuit is simultaneously connected with the grid electrode of the N-type MOSFET and the grid electrode of the P-type MOSFET; the source electrode of the N-type MOSFET and the source electrode of the P-type MOSFET are simultaneously connected with the non-inverting input end of the operational amplifier, the drain electrode of the N-type MOSFET is connected with the working power supply, and the drain electrode of the P-type MOSFET is grounded.
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| US5422570A (en) * | 1993-12-30 | 1995-06-06 | Whirlpool Corporation | Speed sensing for the third harmonic stator voltage signal |
| EP3731406A1 (en) * | 2019-04-25 | 2020-10-28 | Black & Decker Inc. | Low-speed sensorless brushless motor control in a power tool |
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