A precise and reliable method for measuring aircraft wheel speed

Abstract

This invention belongs to the field of aircraft brake control technology, and particularly relates to a method for accurately and reliably measuring aircraft wheel speed. The method includes: acquiring voltage values ​​corresponding to the magnitude of the sinusoidal frequency signal output by a speed sensor, denoted as a first voltage signal, and a square wave signal corresponding to the magnitude of the sinusoidal frequency signal, denoted as a second frequency signal; performing median filtering on the first voltage signal and the second frequency signal respectively; and performing variable variance information fusion calculation on the median-filtered signals to obtain the aircraft wheel speed. This method solves the problems of poor accuracy, weak anti-interference ability, and low reliability in the speed acquisition process of traditional brake control systems.

Description

Technical Field

[0001] This invention belongs to the field of aircraft brake control technology, and in particular relates to a method for accurate and reliable measurement of aircraft wheel speed. Background Technology

[0002] As a core subsystem of aircraft avionics, the aircraft braking control system plays a crucial role in ensuring safe takeoff and landing. Its main function is to control braking and anti-skid maneuvers during the braking process. During braking and anti-skid maneuvers, the controller needs to collect the speed signals of all wheels in real time for feedback closed-loop control of the braking system. Therefore, the aircraft braking control system must acquire accurate and reliable wheel speed signals.

[0003] Existing methods for measuring turbine speed typically involve direct measurement using FPGA-based frequency counting or indirect measurement using voltage values ​​obtained from frequency-to-voltage conversion circuits. FPGA-based frequency counting uses a periodic method to acquire speed signals, but it consists of an FPGA, a DSP, and acquisition circuitry, resulting in a long acquisition chain. The frequency-to-voltage conversion circuit method first converts the acquired speed frequency signal into a voltage signal, then uses the DSP's acquisition module to re-acquire the voltage signal. However, due to component performance and analog circuit structure limitations, this speed acquisition method often results in poor signal accuracy, requiring software correction.

[0004] A search revealed that the invention with publication number CN106802355A proposed a design based on a field-programmable logic array (FPGA) + digital signal processor + speed acquisition circuit to avoid acquisition errors caused by environmental changes, thereby improving the accuracy of speed acquisition in aircraft braking systems. However, its acquisition link is long, increasing the possibility of failure, and it lacks redundancy design, resulting in low reliability.

[0005] A search revealed that the invention with publication number CN106645776B proposed repeatedly reading the dual-redundant wheel speed signal multiple times within a single acquisition cycle to avoid mis-acquisition of the wheel speed signal due to interference and delay, thereby ensuring the accuracy of the wheel speed signal acquisition for the aircraft braking system. However, due to the excessive number of acquisition repetitions, the real-time performance is weak. Although a dual-redundant wheel speed acquisition design is adopted, it is based on the acquired square wave signal. If the square wave acquisition module fails, both signals will be lost. Summary of the Invention

[0006] The purpose of this invention is to address the problems of poor accuracy, weak anti-interference ability, and low reliability in the speed acquisition process of traditional braking control systems. This invention proposes a precise and reliable method for measuring aircraft wheel speed.

[0007] The technical solution of this invention is:

[0008] A method for accurately and reliably measuring aircraft wheel speed, comprising a sinusoidal frequency signal output by an aircraft wheel speed sensor, the method including:

[0009] S1. Based on the sinusoidal frequency signal output by the speed sensor, the voltage value corresponding to the magnitude of the sinusoidal frequency signal is collected and recorded as the first voltage signal, and the frequency square wave signal corresponding to the magnitude of the sinusoidal frequency signal is recorded as the second frequency signal.

[0010] S2, perform median filtering on the first voltage signal and the second frequency signal respectively;

[0011] S3 performs variable variance information fusion calculation on the median-filtered signal to obtain the aircraft wheel speed.

[0012] The features and further improvements of the technical solution of this invention are as follows:

[0013] (1) After S3, the method further includes: S4, when the first voltage signal or the second frequency signal fails, the aircraft wheel speed is calculated using a preset rule.

[0014] (2) S1 is specifically: The first speed signal acquisition method is to obtain a voltage value corresponding to the magnitude of the sinusoidal frequency signal by passing the sinusoidal frequency signal output by the speed sensor through a hysteresis comparator circuit and a frequency-to-voltage conversion circuit, and then acquire the voltage value through the ADC port of the DSP; The second speed signal acquisition method is to output a frequency square wave signal corresponding to the magnitude of the sinusoidal frequency signal by passing the sinusoidal frequency signal output by the speed sensor through a hysteresis comparator circuit and a high-speed optocoupler, and then acquire it through the eCAP port of the DSP.

[0015] (3) In S2, the median filtering of the first voltage signal is specifically performed as follows:

[0016] For the first voltage signal U, it is first limited. If the first voltage signal U is greater than 3V, then the current value is equal to 3V, and then median filtering is performed.

[0017] (4) In S2, the median filtering of the second frequency signal is specifically performed as follows:

[0018] For the second frequency signal F, if the second frequency signal F is less than 4550Hz, the current value is set to 4550Hz, and then median filtering is performed.

[0019] (5) S3, perform fusion calculation on the median-filtered signal to obtain the aircraft wheel speed, specifically:

[0020]

[0021] Among them, V w，kV represents the velocity after fusion at time k. 1，k V represents the speed corresponding to the first voltage value at time k. 2，k Let K be the velocity corresponding to the second frequency value at time k. k P is the fusion coefficient of the two speed signals. K-1 Let Q be the measurement variance of the first speed signal at time k-1, Q be the measurement variance of the second speed signal, and b be the variance variation coefficient.

[0022] (6) In S4, the specific fault of the first voltage signal or the second frequency signal is as follows:

[0023] Regardless of whether a short circuit or open circuit fault occurs in the circuit, the DSP's ADC port can only acquire a constant low voltage value or a high voltage value. Without a transition between high and low voltage, the frequency value acquired by the eCAP port will be 0.

[0024] The first speed signal has two fault modes: high voltage and low voltage, while the second speed signal only has one fault mode: low voltage.

[0025] (7) S4 is specifically:

[0026] S41, Set a sampling period T, and let the difference between the two speed signals at time k be ΔV. k =|V 1，k -V 2，k | Set the speed threshold V T1 and speed error threshold V T2 Set V T1 The purpose is to indirectly determine the aircraft's status by using wheel speed, and to set up V T2 The purpose is to determine whether the difference between the two wheel speed signals is too large;

[0027] S42, if at time k ΔV k ≤V T2 If both wheel speed signals are considered fault-free, the fused speed obtained at time k in S3 is taken as the final speed calculation result, V k =V w，k ;

[0028] S43, if at time k ΔV k >V T2 And within the T periods prior to time k, [V k-T , ..., V k-1 All are less than V T1 If the current aircraft speed is low, it is assumed that the second speed signal only has one fault mode: low voltage. Therefore, if V... 1，k >V T1 Then it is assumed that the first speed signal is faulty, and V k=V 2，k If V 1，k ≤V T1 It is impossible to determine which specific speed signal is faulty, but since the aircraft speed is low and does not need to be included in the anti-skid calculation, V is set to... k =V w，k Wait for the next power-on to detect which speed signal is faulty;

[0029] S44, if at time k ΔV k >V T2 And within the T periods prior to time k, [V k-T , ..., V k-1 Not all are less than V T1 If the current aircraft speed is high, it is assumed that the second speed signal only has one fault mode: low voltage. Therefore, if V... 2，k >V T1 Then it is assumed that the first speed signal is faulty, and V k =V 2，k If V 2，k ≤V T1 Then it is assumed that the second speed signal is faulty, and V k =V 1，k .

[0030] Compared with existing traditional methods, the present invention has the following advantages:

[0031] This invention employs two different acquisition methods—hardware circuitry and DSP—for speed signal acquisition, utilizing a dual-redundancy design of hardware analog circuitry and software program logic to obtain wheel speed signals. Simultaneously, a limiting median filtering algorithm is used to reduce noise in the acquired speed signals, and a proposed variable variance information fusion algorithm is used to fuse the two acquired signals, ensuring more accurate speed data. Furthermore, it enables real-time fault detection of wheel speed signals throughout the aircraft's braking process, ensuring that wheel speed signals can still be acquired even in the event of a single fault, thus improving the reliability of speed signal acquisition. This invention solves the problems of poor accuracy, weak anti-interference capability, and low reliability in the speed acquisition process of traditional braking control systems. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the two-channel speed signal acquisition method proposed in the invention.

[0033] Figure 2 This is a schematic diagram of the filtering of two speed signals and the wheel speed calculation method under fault conditions proposed in the invention;

[0034] Figure 3 This is a schematic diagram illustrating the effectiveness of the proposed method for accurately and reliably measuring aircraft wheel speed. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0036] The present invention aims to obtain accurate and reliable speed signals by using a dual-redundancy method of analog circuits and software program logic, and by using the proposed variable variance information fusion method and wheel speed calculation method under fault conditions.

[0037] like Figure 2 As shown, the present invention provides a method for accurate and reliable measurement of aircraft wheel speed, comprising the following steps:

[0038] Step 1: Acquisition of two speed signals

[0039] Design a two-channel speed signal acquisition circuit. The first channel speed signal acquisition method is to obtain a voltage value corresponding to the magnitude of the sinusoidal frequency signal from the speed sensor through a hysteresis comparator circuit and a frequency-to-voltage conversion circuit, and then acquire the voltage value through the ADC port of the DSP. The second channel speed signal acquisition method is to output a square wave signal corresponding to the magnitude of the sinusoidal frequency signal from the speed sensor through a hysteresis comparator circuit and a high-speed optocoupler, and then acquire it through the eCAP port of the DSP.

[0040] Step 2: Filtering and Fusion Calculation of Two Speed ​​Signals

[0041] For the voltage value U acquired from the first channel, amplitude limiting is first applied. All acquired data should be less than or equal to 3V. If it is greater than 3V, the current value is set to 3V, and then median filtering is performed. For the frequency square wave signal F acquired from the second channel, all acquired data should be greater than or equal to 4550Hz. If it is less than 4550Hz, the current value is set to 4550Hz, and then median filtering is performed.

[0042] Based on engineering experience, it has been found that the speed signal V1 corresponding to the voltage acquired from the first channel has a small initial error, but the error increases later. However, the speed signal V2 corresponding to the frequency square wave signal acquired from the second channel has a relatively stable error throughout the entire cycle. Therefore, this invention proposes a variable variance information fusion method for speed signal fusion. The specific fusion strategy is as follows:

[0043]

[0044] Among them, V w，k V represents the velocity after fusion at time k. 1，k V represents the speed corresponding to the voltage collected by the first channel at time k. 2，k Let K be the velocity corresponding to the square wave signal of the second channel acquired at time k. kP is the fusion coefficient of the two speed signals. k-1 Let Q be the measurement variance of the first speed signal at time k-1, Q be the measurement variance of the second speed signal, and b be the variance variation coefficient.

[0045] Step 3: Calculation of wheel speed under fault conditions

[0046] Typically, wheel speed fault detection involves inputting a speed signal and checking if the acquired output matches the input. However, this detection only occurs when the brake control box is powered on, not during the aircraft's braking process. The method proposed in this invention can determine in real time which of the two speed signals is faulty, and can acquire the wheel speed signal even in the case of a single-channel fault. Due to the different acquisition methods of the two signals, the first speed signal exhibits both high-voltage and low-voltage fault modes, while the second speed signal only exhibits a low-voltage fault mode. This is because regardless of whether the circuit experiences a short circuit or an open circuit fault, the DSP's eCAP port can only acquire a constant low-voltage or high-voltage value; without a high-low voltage transition, the frequency value acquired by the eCAP port is 0. Based on the above reasons, this patent designs the following wheel speed calculation method.

[0047] Let a sampling period T be defined, and let the difference between the two velocity signals at time k be ΔV. k =|V 1，k -V 2，k | Set the speed threshold V T1 and speed error threshold V T2 Set V T1 The purpose is to indirectly determine the aircraft's status by using wheel speed, and to set up V T2 The purpose is to determine whether the two wheel speed signals differ too much.

[0048] If at time k ΔV k ≤V T2 If both wheel speed signals are considered to be fault-free, the fused speed at time k in step two is taken as the final speed calculation result, V. k =V W，k .

[0049] If at time k ΔV k >V T2 And within the T periods prior to time k, [V k-T , ..., V k-1 All are less than V T1 If the current aircraft speed is low, it is assumed that the second speed signal only has one fault mode: low voltage. Therefore, if V... 1，k >V T1 Then it is assumed that the first speed signal is faulty, and V k =V2，k If V 1，k ≤V T1 It is impossible to determine which specific speed signal is faulty, but since the aircraft speed is low and does not need to participate in the anti-skid calculation, V can be left as is. k =V w，k The system will wait for the next power-on to detect which speed signal is faulty.

[0050] If at time k ΔV k >V TZ And within the T periods prior to time k, [V k-T , ..., V k-1 Not all are less than V T1 If the current aircraft speed is high, it is assumed that the second speed signal only has one fault mode: low voltage. Therefore, if V... 2，k >V T1 Then it is assumed that the first speed signal is faulty, and V k =V 2，k If V 2，k ≤V T1 Then it is assumed that the second speed signal is faulty, and V k =V 1，k .

[0051] To demonstrate the effectiveness of the present invention, taking a certain type of aircraft braking system as an example, and in conjunction with the accompanying drawings and specific embodiments, the following steps are performed:

[0052] Step 1: Acquisition of two speed signals

[0053] Design a two-channel speed signal acquisition circuit as follows: Figure 1 As shown, the speed signal is biased by 4V. The high-speed operational amplifier and R6 form a positive feedback circuit. Combined with the voltage divider circuit of R6 and R4, a Schmitt trigger characteristic circuit is formed, which outputs a rectangular square wave signal to the two-channel speed signal acquisition circuit at the back end.

[0054] The first speed signal acquisition method: The rectangular square wave signal is converted into a voltage value corresponding to the magnitude of the sinusoidal frequency signal through a frequency-to-voltage conversion circuit, and then the voltage value is acquired through the ADC port of the DSP.

[0055] The second speed signal acquisition method: The rectangular square wave signal is shaped by a high-speed optocoupler with a rise time of less than 30ns, and the rectangular wave speed signal from 0 to 3.3V is output to the eCAP port of the DSP for acquisition.

[0056] Step 2: Filtering and Fusion Calculation of Two Speed ​​Signals

[0057] 1) Collect two signals.

[0058] 2) Limit the amplitude of the acquired signals. The voltage value of the first acquired signal should be less than or equal to 3V. If it is greater than 3V, the current value is set to 3V. The frequency square wave signal acquired by the second acquired signal should have a period of less than or equal to 4550Hz. If it is greater than 4550Hz, the current value is set to 4550Hz.

[0059] At time k, the upper and lower limits of the two acquired velocity signals are constrained, and the calculations are performed according to the following formulas.

[0060]

[0061] Among them, U k This represents the voltage value collected from the first channel at time k, in V. 1，k For voltage U k The converted speed value is in km / h.

[0062]

[0063] Among them, F k V represents the frequency value of the second acquisition at time k, in Hz. 2，k The velocity value is obtained after converting the frequency F, and the unit is km / h.

[0064] For the collected voltage value U k and frequency value F k First, median filtering is performed on the two signals, and then conversion is performed according to formulas (1) and (2) to obtain a speed signal V related to the voltage value. 1，k and the velocity signal V related to the frequency value 2，k .

[0065] 3) The velocity signal is fused using the variable variance information fusion method proposed in this invention. The specific fusion strategy is as follows:

[0066]

[0067] Among them, V w，k V represents the velocity after fusion at time k. 1，k V represents the speed corresponding to the voltage collected by the first channel at time k. 2，k Let K be the velocity corresponding to the square wave signal of the second channel acquired at time k. k P is the fusion coefficient of the two speed signals. k-1 Let P0 be the measurement variance of the first speed signal at time k-1, Q be the measurement variance of the second speed signal, and b be the variance variation coefficient. Based on the analysis of the collected speed data, in this embodiment, the initial value of the measurement variance of the first speed signal is P0 = 8 km / h, b = 0.022, and the measurement variance of the second speed signal is Q = 2 km / h.

[0068] Step 3: Calculation of wheel speed under fault conditions

[0069] Set a sampling period T = 5, and let ΔV k =|V 1，k -V 2，k | Set the speed threshold V T1 =26 km / h and wheel speed error threshold V T2 =6KM / h, set V T1 The purpose is to indirectly determine the aircraft's status by using wheel speed, and to set up V T2 The purpose is to determine whether the two wheel speed signals differ too much.

[0070] If ΔV ≤ 6 km / h at time k, then both wheel speed signals are considered to be fault-free. The fused speed from step two at time k is taken as the final speed calculation result, V = V w，k .

[0071] If at time k ΔV > 6 km / h, and within the 5 periods prior to time k [V k-T , ..., V k-1 If all values ​​are less than 26 km / h, the current aircraft speed is considered low. Since the second speed signal only has one fault mode (low voltage), therefore, if V... 1，k If the speed is greater than 26 km / h, the first speed signal is considered faulty, and V... k =V 2，k If V 1，k For speeds ≤26 km / h, it's impossible to determine which speed signal is faulty. However, since the aircraft speed is low and doesn't need to be included in anti-skid calculations, V can be left as is. k =V w，k The system will wait for the next power-on to detect which speed signal is faulty.

[0072] If at time k ΔV > 6 km / h, and within the 5 periods prior to time k [V k-T , ..., V k-1 If not all speeds are less than 26 km / h, then the current aircraft speed is considered high. Since the second speed signal only has a low voltage fault mode, therefore, if V... 2，k If the speed is greater than 26 km / h, the first speed signal is considered faulty, and V... k =V 2，k If V 2，k If the speed is ≤26 km / h, the second speed signal is considered faulty, then V k =V 1，k .

[0073] from Figure 3Simulation results show that before 6 seconds, the combined speed signal is equal to the fused value of the first and second speed signals. After the first speed signal fails at 6 seconds, the combined speed signal becomes equal to the magnitude of the second speed signal. In summary, the variable variance information fusion method and the wheel speed calculation method under fault conditions proposed in this invention can obtain accurate and reliable speed signals.

[0074] Compared with existing traditional methods, the present invention has the following advantages:

[0075] This invention employs two different acquisition methods—hardware circuitry and DSP—for speed signal acquisition, utilizing a dual-redundancy design of hardware analog circuitry and software program logic to obtain wheel speed signals. Simultaneously, a limiting median filtering algorithm is used to reduce noise in the acquired speed signals, and a proposed variable variance information fusion algorithm is used to fuse the two acquired signals, ensuring more accurate speed data. Furthermore, it enables real-time fault detection of wheel speed signals throughout the aircraft's braking process, ensuring that wheel speed signals can still be acquired even in the event of a single fault, thus improving the reliability of speed signal acquisition. This invention solves the problems of poor accuracy, weak anti-interference capability, and low reliability in the speed acquisition process of traditional braking control systems.

Claims

1. A method for accurately and reliably measuring aircraft wheel speed, characterized in that, The method includes: (The method utilizes) a sinusoidal frequency signal output from an aircraft wheel speed sensor. S1. Based on the sinusoidal frequency signal output by the speed sensor, the voltage value corresponding to the magnitude of the sinusoidal frequency signal is collected and recorded as the first voltage signal, and the frequency square wave signal corresponding to the magnitude of the sinusoidal frequency signal is recorded as the second frequency signal. S1 specifically involves: the first speed signal acquisition method involves passing the sinusoidal frequency signal output by the speed sensor through a hysteresis comparator circuit and a frequency-to-voltage conversion circuit to obtain a voltage value corresponding to the magnitude of the sinusoidal frequency signal, and then acquiring the voltage value through the ADC port of the DSP; the second speed signal acquisition method involves passing the sinusoidal frequency signal output by the speed sensor through a hysteresis comparator circuit and a high-speed optocoupler to output a frequency square wave signal corresponding to the magnitude of the sinusoidal frequency signal, and then acquiring it through the eCAP port of the DSP. S2, perform median filtering on the first voltage signal and the second frequency signal respectively; S3, perform variable variance information fusion calculation on the median filtered signal to obtain the aircraft wheel speed; S4, when the first voltage signal or the second frequency signal fails, the aircraft wheel speed is calculated using preset rules; In S4, the specific fault in the first voltage signal or the second frequency signal is as follows: Regardless of whether a short circuit or open circuit fault occurs in the circuit, the DSP's ADC port can only acquire a constant low voltage value or a high voltage value. Without a high-low voltage transition, the frequency value acquired by the eCAP port will be 0. The first speed signal has two fault modes: high voltage and low voltage, while the second speed signal only has one fault mode: low voltage. S4 specifically refers to: S41, Set a sampling period T, and let the difference between the two speed signals at time k be _____. Set speed threshold and speed error threshold ,set up The purpose is to indirectly determine the aircraft's status by using wheel speed, and to set up... The purpose is to determine whether the difference between the two wheel speed signals is too large; S42, if at time k If both wheel speed signals are deemed to be fault-free, the fused speed obtained at time k in S3 will be used as the final speed calculation result. ; S43, if at time k And within T periods before time k All less than If so, it is assumed that the current aircraft speed is low. Since the second speed signal only has one fault mode—low voltage—therefore, if Then it is assumed that the first speed signal is faulty. ;if It is impossible to determine which specific speed signal is faulty, but since the aircraft speed is low and does not need to be included in the anti-skid calculation, then... Wait for the next power-on to detect which speed signal is faulty; S44, if at time k Within T periods before time k Not all are smaller than If so, it is assumed that the current aircraft speed is high. Since the second speed signal only has one fault mode—low voltage—therefore, if Then it is assumed that the first speed signal is faulty. ;if Then it is assumed that the second speed signal is faulty. .

2. The method for accurately and reliably measuring aircraft wheel speed according to claim 1, characterized in that, In S2, the median filtering of the first voltage signal is specifically performed as follows: For the first voltage signal U, it is first limited. If the first voltage signal U is greater than 3V, then the current value is equal to 3V, and then median filtering is performed.

3. The method for accurately and reliably measuring aircraft wheel speed according to claim 1, characterized in that, In S2, the median filtering of the second frequency signal is specifically performed as follows: For the second frequency signal F, if the second frequency signal F is less than 4550Hz, the current value is set to 4550Hz, and then median filtering is performed.

4. The method for accurately and reliably measuring aircraft wheel speed according to claim 1, characterized in that, S3, performs fusion calculations on the median-filtered signal to obtain the aircraft wheel speed, specifically: in, Let k be the velocity after fusion. Let k be the speed corresponding to the voltage value of the first path at time k. Let k be the velocity corresponding to the second frequency value at time k. The fusion coefficient of the two speed signals is denoted as . The measurement variance of the first velocity signal at time k-1. Let be the measurement variance of the second speed signal, and b be the variance variation coefficient.

Images