Simulation test method for aircraft brake controller

Abstract

The invention provides a simulation test method for an aircraft brake controller. The method comprises the following steps: acquiring a standard speed curve of an aircraft wheel under each runway condition, and a target runway condition, a target load state and a target climate condition corresponding to a to-be-tested aircraft brake controller in a simulation test; determining a target standard speed curve required by the to-be-tested aircraft brake controller during the simulation test from each standard speed curve according to the target runway condition; according to the target load state and the target climate condition, determining a corresponding speed correction coefficient of the to-be-tested aircraft brake controller during the simulation test; and correcting the target standard speed curve according to the speed correction coefficient to obtain a corrected speed curve, and performing a simulation test on the to-be-tested aircraft brake controller based on the corrected speed curve. According to the invention, accurate simulation of the wheel speed of the aircraft wheel can be realized, so that the test accuracy of the aircraft brake controller is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft brakes, and in particular to a simulation test method for an aircraft brake controller. Background Art

[0002] The aircraft brake controller is mainly used to ensure the safety and heading consistency of the aircraft during landing, braking and taxiing under various runway conditions, and automatically adjust the brake pressure according to the runway surface state, so that the braking torque is adapted to the runway surface state, and the combination coefficient between the wheel and the ground is fully utilized to prevent the wheel from locking and improve the braking efficiency. Therefore, after the aircraft brake controller is developed, it needs to be tested to verify the performance of the controller under various conditions, including normal braking and emergency braking, to ensure that the aircraft can brake safely and stably during takeoff, landing and taxiing.

[0003] In order to verify the performance of the aircraft brake controller, a ground simulation test of the aircraft brake system is usually carried out in a ground integrated iron bird to simulate the real environment of the aircraft during the braking process as much as possible. Among them, since the aircraft wheels in the ground integrated iron bird are stationary, and the verification of the aircraft brake controller requires the speed of each aircraft wheel during the entire landing process, a wheel speed simulation device is usually used to drive the speed sensor in the wheel according to the set speed curve through a servo motor to achieve the simulation of the wheel speed of each aircraft wheel.

[0004] However, the inventors found that when the speed sensor in the wheel is driven according to a set speed curve, a universal speed curve is usually used to drive the speed sensor in the wheel, resulting in inaccurate simulation of the aircraft wheel speed, thereby affecting the test accuracy of the aircraft brake controller. Summary of the invention

[0005] The embodiment of the present invention provides a simulation test method for an aircraft brake controller to solve the problem that the current simulation of the wheel speed of an aircraft is not accurate enough, thereby affecting the test accuracy of the aircraft brake controller.

[0006] In a first aspect, an embodiment of the present invention provides an aircraft brake controller simulation test method, comprising:

[0007] Obtain the standard speed curve of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test;

[0008] Determine the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test from each of the standard speed curves according to the target runway condition;

[0009] Determining a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition;

[0010] The target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

[0011] In a possible implementation, the runway conditions include a dry runway, a wet runway, a thin ice runway, and a snowy runway;

[0012] The step of obtaining the standard speed curve of the aircraft wheels under various runway conditions includes:

[0013] Acquire a plurality of speed curves corresponding to the wheels of the aircraft on the dry runway, the wet runway, the thin ice runway and the snow-covered runway, respectively, wherein each speed curve includes a load state and a climate condition corresponding to the current speed curve;

[0014] Determining a standard speed curve of the aircraft wheels under the dry runway condition according to the plurality of speed curves corresponding to the dry runway, and recording it as a first standard speed curve;

[0015] Determining a standard speed curve of the aircraft wheels under the wet runway condition according to the plurality of speed curves corresponding to the wet runway, and recording the standard speed curve as a second standard speed curve;

[0016] From the speed curves corresponding to the dry runway, a speed curve whose similarity to the first standard speed curve reaches a first threshold is selected and recorded as a first speed curve;

[0017] From the speed curves corresponding to the wet runway, a speed curve whose similarity to the second standard speed curve reaches a second threshold is selected and recorded as a second speed curve;

[0018] screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, and determining a standard speed curve of the aircraft wheels under the thin ice runway condition according to the screening result, recorded as a third standard speed curve;

[0019] According to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, multiple speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway conditions is determined according to the screening results, which is recorded as a fourth standard speed curve.

[0020] In a possible implementation, according to the load state and climate condition corresponding to the first speed curve and the load state and climate condition corresponding to the second speed curve, a plurality of speed curves corresponding to the thin ice runway are screened, and according to the screening result, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined, recorded as a third standard speed curve, including:

[0021] Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve to determine a first candidate speed curve corresponding to the thin ice runway;

[0022] Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the second speed curve to determine a second candidate speed curve corresponding to the thin ice runway;

[0023] According to the correlation between the thin ice runway and the dry runway and the first alternative speed curve, as well as the correlation between the thin ice runway and the wet runway and the second alternative speed curve, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined and recorded as a third standard speed curve.

[0024] In a possible implementation, according to the correlation between the thin ice runway and the dry runway and the first candidate speed curve, and the correlation between the thin ice runway and the wet runway and the second candidate speed curve, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined, which is recorded as a third standard speed curve, including:

[0025] according to Determine a standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve;

[0026] Wherein, V3 is the standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve, r1 is the correlation between the thin ice runway and the dry runway, is the i-th first candidate speed curve, r2 is the correlation between the thin ice runway and the wet runway, The i-th second candidate speed curve.

[0027] In a possible implementation, according to the load state and climate condition corresponding to the first speed curve and the load state and climate condition corresponding to the second speed curve, a plurality of speed curves corresponding to the snow-covered runway are screened, and according to the screening result, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined, recorded as a fourth standard speed curve, including:

[0028] Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the first speed curve to determine a third candidate speed curve corresponding to the snow-covered runway;

[0029] Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the second speed curve to determine a fourth candidate speed curve corresponding to the snow-covered runway;

[0030] According to the correlation between the snow-covered runway and the dry runway and the third alternative speed curve, as well as the correlation between the snow-covered runway and the wet runway and the fourth alternative speed curve, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined and recorded as the fourth standard speed curve.

[0031] In a possible implementation, according to the correlation between the snow-covered runway and the dry runway and the third candidate speed curve, and the correlation between the snow-covered runway and the wet runway and the fourth candidate speed curve, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined, which is recorded as the fourth standard speed curve, including:

[0032] according to Determine a standard speed curve of the aircraft wheels under the snow-covered runway condition, recorded as a fourth standard speed curve;

[0033] Wherein, V4 is the standard speed curve of the aircraft wheels under the condition of the snow-covered runway, recorded as the fourth standard speed curve, r3 is the correlation between the snow-covered runway and the dry runway, is the kth third candidate speed curve, r4 is the correlation between the snow runway and the wet runway, It is the fourth candidate speed curve described in the kth item.

[0034] In a possible implementation, determining a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition includes:

[0035] Determining a first speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target load state and the load state corresponding to the target standard speed curve;

[0036] Determining a second speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target climate condition and the climate condition corresponding to the target standard speed curve;

[0037] According to the first speed correction coefficient and the second speed correction coefficient, a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

[0038] In a second aspect, an embodiment of the present invention provides an aircraft brake controller simulation test device, comprising:

[0039] An acquisition module is used to acquire the standard speed curve of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test;

[0040] A first processing module is used to determine a target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test from each of the standard speed curves according to the target runway condition;

[0041] The second processing module is used to determine the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition;

[0042] The simulation test module is used to correct the target standard speed curve according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

[0043] In a third aspect, an embodiment of the present invention provides a terminal, comprising a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to perform the steps of the method described in the first aspect or any possible implementation of the first aspect.

[0044] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in the first aspect or any possible implementation method of the first aspect are implemented.

[0045] The embodiment of the present invention provides a simulation test method for an aircraft brake controller, which obtains the standard speed curve of the aircraft wheel under various runway conditions, as well as the target runway conditions, target load state and target climate conditions corresponding to the aircraft brake controller to be tested during the simulation test; first, the target standard speed curve required by the aircraft brake controller to be tested during the simulation test can be determined from the various standard speed curves according to the target runway conditions; then, the speed correction coefficient corresponding to the aircraft brake controller to be tested during the simulation test can be determined according to the target load state and target climate conditions; and then, the target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test of the aircraft brake controller to be tested based on the corrected speed curve. Then, the accurate wheel speed simulation of the aircraft brake controller to be tested under the target runway conditions, target load state and target climate conditions can be realized according to the corrected speed curve, thereby improving the test accuracy of the aircraft brake controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0047] Figure 1 It is a flow chart of the implementation of the aircraft brake controller simulation test method provided by the embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of a simulation test when the aircraft brake controller to be tested provided by an embodiment of the present invention is a physical aircraft brake controller;

[0049] Figure 3 is a schematic diagram of a simulation test when the aircraft brake controller to be tested provided by an embodiment of the present invention is a simulation model;

[0050] Figure 4 It is a structural schematic diagram of an aircraft brake controller simulation test device provided by an embodiment of the present invention;

[0051] Figure 5 is a schematic diagram of a terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0054] See also Figure 1 , which shows a flow chart of the implementation of the aircraft brake controller simulation test method provided by an embodiment of the present invention, which is described in detail as follows:

[0055] In step 101, the standard speed curves of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test are obtained.

[0056] Optionally, the runway conditions may include a dry runway, a wet runway, a thin ice runway, and a snowy runway.

[0057] Obtaining the standard speed curve of the aircraft wheels under various runway conditions, which may include:

[0058] A plurality of speed curves corresponding to the wheels of the aircraft on a dry runway, a wet runway, a thin ice runway and a snowy runway are obtained, wherein each speed curve includes a load state and a climate condition corresponding to the current speed curve.

[0059] According to the multiple speed curves corresponding to the dry runway, a standard speed curve of the aircraft wheels under the dry runway condition is determined and recorded as a first standard speed curve.

[0060] According to the multiple speed curves corresponding to the wet runway, a standard speed curve of the aircraft wheels under the wet runway condition is determined and recorded as the second standard speed curve.

[0061] From the speed curves corresponding to the dry runway, a speed curve whose similarity to the first standard speed curve reaches a first threshold is screened out and recorded as the first speed curve.

[0062] From the speed curves corresponding to the wet runway, a speed curve whose similarity to the second standard speed curve reaches a second threshold is selected and recorded as the second speed curve.

[0063] According to the load state and climatic conditions corresponding to the first speed curve and the load state and climatic conditions corresponding to the second speed curve, multiple speed curves corresponding to the thin ice runway are screened, and the standard speed curve of the aircraft wheels under the thin ice runway conditions is determined according to the screening results, which is recorded as the third standard speed curve.

[0064] According to the load state and climatic conditions corresponding to the first speed curve and the load state and climatic conditions corresponding to the second speed curve, multiple speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined according to the screening results, which is recorded as the fourth standard speed curve.

[0065] Exemplarily, a standard speed curve of the aircraft wheels under dry runway conditions may be determined based on the mean, median, or most frequently appearing speed curve of multiple speed curves corresponding to the dry runway, and recorded as the first standard speed curve.

[0066] Similarly, the standard speed curve of the aircraft wheels under wet runway conditions may be determined based on the mean, median or the speed curve that appears most frequently among the multiple speed curves corresponding to the wet runway, and recorded as the second standard speed curve.

[0067] The purpose of this embodiment is to determine the most representative speed curve among multiple speed curves corresponding to a dry runway or a wet runway as the first standard speed curve or the second standard speed curve, and the method for determining the first standard speed curve or the second standard speed curve is not limited.

[0068] In this embodiment, considering that there are more samples of speed curves of aircraft wheels under dry runway and wet runway conditions, and fewer samples of speed curves of aircraft wheels under thin ice runway and snowy runway conditions, in order to more accurately obtain the standard speed curves of aircraft wheels under various runway conditions, the first standard speed curve under dry runway conditions and the second standard speed curve under wet runway conditions are first obtained, and then based on the first standard speed curve and the second standard speed curve, representative speed curves are respectively screened from multiple speed curves corresponding to thin ice runway and snowy runway according to load state and climatic conditions to obtain the third standard speed curve under thin ice runway conditions and the fourth standard speed curve under snowy runway conditions.

[0069] Optionally, according to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, a plurality of speed curves corresponding to the thin ice runway are screened, and a standard speed curve of the aircraft wheels under the thin ice runway condition is determined according to the screening result, which is recorded as a third standard speed curve, and may include:

[0070] Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climatic conditions corresponding to the first speed curve to determine a first candidate speed curve corresponding to the thin ice runway;

[0071] Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climatic conditions corresponding to the second speed curve to determine a second candidate speed curve corresponding to the thin ice runway;

[0072] According to the correlation between the thin ice runway and the dry runway and the first alternative speed curve, as well as the correlation between the thin ice runway and the wet runway and the second alternative speed curve, a standard speed curve of the aircraft wheels under thin ice runway conditions is determined and recorded as the third standard speed curve.

[0073] For example, according to Determine the standard speed curve of the aircraft wheels under thin ice runway conditions, recorded as the third standard speed curve;

[0074] Among them, V3 is the standard speed curve of the aircraft wheels under thin ice runway conditions, recorded as the third standard speed curve, r1 is the correlation between the thin ice runway and the dry runway, is the i-th first candidate speed curve, r2 is the correlation between the thin ice runway and the wet runway, The i-th second alternative speed curve.

[0075] Exemplarily, multiple speed curves corresponding to the thin ice runway are screened according to the load state and climatic conditions corresponding to the first speed curve to determine a first alternative speed curve corresponding to the thin ice runway. That is, a speed curve having the same or higher similarity to the load state and climatic conditions corresponding to the first speed curve is screened from the multiple speed curves corresponding to the thin ice runway as the first alternative speed curve corresponding to the thin ice runway.

[0076] According to the load state and climatic conditions corresponding to the second speed curve, multiple speed curves corresponding to the thin ice runway are screened to determine a second alternative speed curve corresponding to the thin ice runway. That is, a speed curve with the same or higher similarity to the load state and climatic conditions corresponding to the second speed curve is screened from the multiple speed curves corresponding to the thin ice runway as the second alternative speed curve corresponding to the thin ice runway.

[0077] For example, if the load state and climate condition corresponding to the first speed curve are load state 1 and climate condition 1, and the load state and climate condition corresponding to the second speed curve are load state 2 and climate condition 2, then a speed curve having a load state of load state 1 or a high similarity to load state 1 and a climate condition of climate condition 1 or a high similarity to climate condition 1 is selected from the multiple speed curves corresponding to the thin ice runway as the first candidate speed curve. A speed curve having a load state of load state 2 or a high similarity to load state 2 and a climate condition of climate condition 2 or a high similarity to climate condition 2 is selected from the multiple speed curves corresponding to the thin ice runway as the second candidate speed curve.

[0078] In this embodiment, the different reference characteristics of dry runways and wet runways to thin ice runways are taken into consideration. Therefore, after determining the first alternative speed curve corresponding to the thin ice runway according to the dry runway and determining the second alternative speed curve corresponding to the thin ice runway according to the wet runway, the correlation between the thin ice runway and the dry runway, and the correlation between the thin ice runway and the wet runway are measured, so as to more accurately determine the standard speed curve of the aircraft wheels under the thin ice runway condition, that is, the third standard speed curve.

[0079] Optionally, according to the load state and climate condition corresponding to the first speed curve and the load state and climate condition corresponding to the second speed curve, a plurality of speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined according to the screening result, which is recorded as a fourth standard speed curve, and may include:

[0080] Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the first speed curve to determine a third candidate speed curve corresponding to the snow-covered runway;

[0081] Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the second speed curve to determine a fourth candidate speed curve corresponding to the snow-covered runway;

[0082] According to the correlation between the snow-covered runway and the dry runway and the third alternative speed curve, as well as the correlation between the snow-covered runway and the wet runway and the fourth alternative speed curve, a standard speed curve of the aircraft wheels under snow-covered runway conditions is determined and recorded as the fourth standard speed curve.

[0083] For example, according to Determine the standard speed curve of the aircraft wheels under snow-covered runway conditions, recorded as the fourth standard speed curve;

[0084] Among them, V4 is the standard speed curve of the aircraft wheels under the condition of snow runway, recorded as the fourth standard speed curve, r3 is the correlation between the snow runway and the dry runway, is the kth third alternative speed curve, r4 is the correlation between the snow runway and the wet runway, It is the kth fourth alternative speed curve.

[0085] Similarly, multiple speed curves corresponding to the snow-covered runway are screened according to the load state and climatic conditions corresponding to the first speed curve to determine a third alternative speed curve corresponding to the snow-covered runway. That is, a speed curve with the same or higher similarity to the load state and climatic conditions corresponding to the first speed curve is screened from the multiple speed curves corresponding to the snow-covered runway as the third alternative speed curve corresponding to the snow-covered runway.

[0086] According to the load state and climatic conditions corresponding to the second speed curve, multiple speed curves corresponding to the snow-covered runway are screened to determine a fourth alternative speed curve corresponding to the snow-covered runway. That is, a speed curve with the same or higher similarity to the load state and climatic conditions corresponding to the second speed curve is screened from the multiple speed curves corresponding to the snow-covered runway as the fourth alternative speed curve corresponding to the snow-covered runway.

[0087] Similarly, in this embodiment, the different reference characteristics of dry runways and wet runways to snowy runways are taken into consideration. Therefore, after determining the third alternative speed curve corresponding to the snowy runway based on the dry runway and determining the fourth alternative speed curve corresponding to the snowy runway based on the wet runway, the correlation between the snowy runway and the dry runway, as well as the correlation between the snowy runway and the wet runway are measured, so as to more accurately determine the standard speed curve of the aircraft wheels under the snowy runway condition, that is, the fourth standard speed curve.

[0088] In step 102, a target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test is determined from various standard speed curves according to the target runway conditions.

[0089] Exemplarily, after obtaining the first standard speed curve, the second standard speed curve, the third standard speed curve and the fourth standard speed curve corresponding to the dry runway, the wet runway, the thin ice runway and the snow runway respectively, if the target runway condition belongs to the dry runway, the first standard speed curve can be determined as the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test. If the target runway condition belongs to the wet runway, the second standard speed curve can be determined as the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test. The same applies to other situations.

[0090] In step 103, according to the target load state and the target climate condition, the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

[0091] Optionally, determining a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition may include:

[0092] Determine a first speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target load state and the load state corresponding to the target standard speed curve;

[0093] Determine a second speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target climatic condition and the climatic condition corresponding to the target standard speed curve;

[0094] According to the first speed correction coefficient and the second speed correction coefficient, a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

[0095] In this embodiment, taking into account the effects of the load state and the climatic conditions on the speed respectively, a correction coefficient, i.e., the first speed correction coefficient, is determined according to the similarity between the target load state and the load state corresponding to the target standard speed curve, and then a correction coefficient, i.e., the second speed correction coefficient, is determined according to the similarity between the target climatic conditions and the climatic conditions corresponding to the target standard speed curve. Thus, according to the first speed correction coefficient and the second speed correction coefficient, a more accurate speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

[0096] In step 104, the target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

[0097] In this embodiment, after obtaining the corrected speed curve, a simulation test can be performed on the actual aircraft brake controller based on the corrected speed curve, or a simulation test can be performed on the simulation model of the aircraft brake controller based on the corrected speed curve.

[0098] For example, Figure 2 As shown, when the aircraft brake controller to be tested is a physical aircraft brake controller, the user operates the simulation device to simulate the pedal brake, and outputs the wheel speed simulation signal based on the modified speed curve. The aircraft brake controller to be tested collects the pedal brake signal and the wheel speed simulation signal, processes the pedal brake signal and the wheel speed simulation signal, and outputs the brake system pressure and flow signal, etc. The brake system on the test bench of the ground integrated iron bird (including hydraulic pipelines, brackets and brake system components and accessories, etc.) receives the brake system pressure and flow signal, and the brake system starts to work. The aircraft brake controller to be tested collects the output signal of the brake system (including the brake system pressure and flow signal, etc.), and transmits the signal to the computer for display, thereby obtaining the simulation test result.

[0099] For example, Figure 3 As shown, when the aircraft brake controller to be tested is a simulation model, the aircraft brake controller to be tested is simulated by a data acquisition device and a signal excitation device. The digital model can provide the customer with a digital model of the controller, which can be run through the simulation environment in the signal excitation device. The user manipulates the simulation device to simulate the pedal brake, and outputs the wheel speed simulation signal based on the modified speed curve. The data acquisition device collects the pedal brake signal and the wheel speed simulation signal, and transmits the pedal brake signal and the wheel speed simulation signal to the signal excitation device. The simulation model starts to run, outputs the pressure and flow signals required for braking and transmits them to the brake system. The brake system on the test bench of the ground integrated iron bird (including hydraulic pipelines, brackets and brake system accessories, etc.) receives the brake system pressure and flow signals, and the brake system starts to work. The data acquisition device collects the output signal of the brake system (including the brake system pressure and flow signals, etc.), and transmits the signal to the computer for display, thereby obtaining the simulation test results. Among them, the controller digital model provided by the customer requires a certain environment when running. The digital model is output as a dynamic link library file, i.e., a dll file, and then this file is imported in the simulation environment to realize the real-time simulation calculation of the digital model. Apply the simulation environment to establish the simulation model and build the simulation monitoring and control interface.

[0100] Exemplarily, the brake system pressure and flow signals may also be simulated by a signal excitation device, and the data acquisition device acquires the brake system pressure and flow signals simulated by the signal excitation device and transmits the signals to a computer for display.

[0101] Among them, when performing fault simulation test on the brake controller of the aircraft to be tested, fault injection can be achieved through cable settings, for example, disconnecting the cables to form an open circuit to simulate the open circuit of each component of the brake system. Or the cables at both ends of each component are directly connected to form a short circuit to simulate the short circuit of each component. Among them, the brake system can include hydraulic pipelines, simulation brackets, brake system accessories, etc. The brake system accessories can include shut-off valves, two-way control valves, brake device components (brake actuators), one-way valves, accumulators, wheel speed sensors, pressure reducing valves, etc., so as to realize the construction of a semi-physical simulation environment for anti-skid brake test hardware, that is, the construction of a semi-physical simulation test environment for the brake controller of the aircraft to be tested.

[0102] Among them, the simulation equipment may include a flight simulation cockpit, which is equipped with all simulated flight environment equipment including the switch operation of the brake system and the operation of the foot brake. It may include a brake system cockpit simulation operation panel, aircraft simulation driving instruments and aircraft visual display equipment, etc. The cockpit simulation operation panel can simulate the brake system switch and foot pedal operation.

[0103] The embodiment of the present invention obtains the standard speed curve of the aircraft wheel under various runway conditions, as well as the target runway conditions, target load state and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test; first, the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test can be determined from the various standard speed curves according to the target runway conditions; then, the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test can be determined according to the target load state and the target climate conditions; and then, the target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test of the brake controller of the aircraft to be tested based on the corrected speed curve. Then, accurate wheel speed simulation of the brake controller of the aircraft to be tested under the target runway conditions, target load state and target climate conditions can be achieved according to the corrected speed curve, thereby improving the test accuracy of the aircraft brake controller.

[0104] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0105] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0106] Figure 4 The structure diagram of the aircraft brake controller simulation test device provided by the embodiment of the present invention is shown. For the convenience of description, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0107] like Figure 4 As shown, the aircraft brake controller simulation test device 4 includes: an acquisition module 41, a first processing module 42, a second processing module 43 and a simulation test module 44.

[0108] The acquisition module 41 is used to acquire the standard speed curve of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test;

[0109] A first processing module 42 is used to determine the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test from each of the standard speed curves according to the target runway condition;

[0110] The second processing module 43 is used to determine the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition;

[0111] The simulation test module 44 is used to correct the target standard speed curve according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

[0112] The embodiment of the present invention obtains the standard speed curve of the aircraft wheel under various runway conditions, as well as the target runway conditions, target load state and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test; first, the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test can be determined from the various standard speed curves according to the target runway conditions; then, the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test can be determined according to the target load state and the target climate conditions; and then, the target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test of the brake controller of the aircraft to be tested based on the corrected speed curve. Then, accurate wheel speed simulation of the brake controller of the aircraft to be tested under the target runway conditions, target load state and target climate conditions can be achieved according to the corrected speed curve, thereby improving the test accuracy of the aircraft brake controller.

[0113] In a possible implementation, the runway conditions include a dry runway, a wet runway, a thin ice runway, and a snowy runway; the acquisition module 41 may be used to acquire a plurality of speed curves corresponding to the wheels of the aircraft on the dry runway, the wet runway, the thin ice runway, and the snowy runway, respectively, wherein each speed curve includes a load state and a climate condition corresponding to the current speed curve;

[0114] Determining a standard speed curve of the aircraft wheels under the dry runway condition according to the plurality of speed curves corresponding to the dry runway, and recording it as a first standard speed curve;

[0115] Determining a standard speed curve of the aircraft wheels under the wet runway condition according to the plurality of speed curves corresponding to the wet runway, and recording the standard speed curve as a second standard speed curve;

[0116] From the speed curves corresponding to the dry runway, a speed curve whose similarity to the first standard speed curve reaches a first threshold is selected and recorded as a first speed curve;

[0117] From the speed curves corresponding to the wet runway, a speed curve whose similarity to the second standard speed curve reaches a second threshold is selected and recorded as a second speed curve;

[0118] screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, and determining a standard speed curve of the aircraft wheels under the thin ice runway condition according to the screening result, recorded as a third standard speed curve;

[0119] According to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, multiple speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway conditions is determined according to the screening results, which is recorded as a fourth standard speed curve.

[0120] In a possible implementation, the acquisition module 41 may be used to screen multiple speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve, and determine a first candidate speed curve corresponding to the thin ice runway;

[0121] Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the second speed curve to determine a second candidate speed curve corresponding to the thin ice runway;

[0122] According to the correlation between the thin ice runway and the dry runway and the first alternative speed curve, as well as the correlation between the thin ice runway and the wet runway and the second alternative speed curve, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined and recorded as a third standard speed curve.

[0123] In a possible implementation, the acquisition module 41 may be used to Determine a standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve;

[0124] Wherein, V3 is the standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve, r1 is the correlation between the thin ice runway and the dry runway, is the i-th first candidate speed curve, r2 is the correlation between the thin ice runway and the wet runway, The i-th second candidate speed curve.

[0125] In a possible implementation, the acquisition module 41 may be used to screen multiple speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the first speed curve, and determine a third candidate speed curve corresponding to the snow-covered runway;

[0126] Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the second speed curve to determine a fourth candidate speed curve corresponding to the snow-covered runway;

[0127] According to the correlation between the snow-covered runway and the dry runway and the third alternative speed curve, as well as the correlation between the snow-covered runway and the wet runway and the fourth alternative speed curve, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined and recorded as the fourth standard speed curve.

[0128] In a possible implementation, the acquisition module 41 may be used to Determine a standard speed curve of the aircraft wheels under the snow-covered runway condition, recorded as a fourth standard speed curve;

[0129] Wherein, V4 is the standard speed curve of the aircraft wheels under the condition of the snow-covered runway, recorded as the fourth standard speed curve, r3 is the correlation between the snow-covered runway and the dry runway, is the kth third candidate speed curve, r4 is the correlation between the snow runway and the wet runway, It is the fourth candidate speed curve described in the kth item.

[0130] In a possible implementation, the simulation test module 44 may be used to determine a first speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target load state and the load state corresponding to the target standard speed curve;

[0131] Determining a second speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target climate condition and the climate condition corresponding to the target standard speed curve;

[0132] According to the first speed correction coefficient and the second speed correction coefficient, a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

[0133] Figure 5 is a schematic diagram of a terminal provided by an embodiment of the present invention. Figure 5 As shown, the terminal 5 of this embodiment includes: a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, the steps in the above-mentioned various aircraft brake controller simulation method embodiments are implemented, such as Figure 1 Alternatively, when the processor 50 executes the computer program 52, the functions of each module / unit in the above-mentioned device embodiments are implemented, for example Figure 4 Functionality of the modules / units 41 to 44 shown.

[0134] Exemplarily, the computer program 52 may be divided into one or more modules / units, one or more modules / units are stored in the memory 51 and executed by the processor 50 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, and the instruction segments are used to describe the execution process of the computer program 52 in the terminal 5. For example, the computer program 52 may be divided into Figure 4 Modules / units 41 to 44 are shown.

[0135] The terminal 5 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will appreciate that Figure 5 It is only an example of terminal 5 and does not constitute a limitation on terminal 5. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal may also include input and output devices, network access devices, buses, etc.

[0136] The processor 50 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0137] The memory 51 may be an internal storage unit of the terminal 5, such as a hard disk or memory of the terminal 5. The memory 51 may also be an external storage device of the terminal 5, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the terminal 5. Further, the memory 51 may also include both an internal storage unit of the terminal 5 and an external storage device. The memory 51 is used to store computer programs and other programs and data required by the terminal. The memory 51 may also be used to temporarily store data that has been output or is to be output.

[0138] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0139] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0140] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0141] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0142] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0143] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0144] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various aircraft brake controller simulation method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form. The computer-readable medium can include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium.

[0145] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A simulation test method for an aircraft brake controller, characterized in that: include: Obtain the standard speed curve of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test; Determine the target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test from each of the standard speed curves according to the target runway condition; Determining a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition; The target standard speed curve is corrected according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

2. The aircraft brake controller simulation test method according to claim 1, characterized in that: The runway conditions include dry runways, wet runways, thin ice runways and snow-covered runways; The step of obtaining the standard speed curve of the aircraft wheels under various runway conditions includes: Acquire a plurality of speed curves corresponding to the wheels of the aircraft on the dry runway, the wet runway, the thin ice runway and the snow-covered runway, respectively, wherein each speed curve includes a load state and a climate condition corresponding to the current speed curve; Determining a standard speed curve of the aircraft wheels under the dry runway condition according to the plurality of speed curves corresponding to the dry runway, and recording it as a first standard speed curve; Determining a standard speed curve of the aircraft wheels under the wet runway condition according to the plurality of speed curves corresponding to the wet runway, and recording the standard speed curve as a second standard speed curve; From the speed curves corresponding to the dry runway, a speed curve whose similarity to the first standard speed curve reaches a first threshold is selected and recorded as a first speed curve; From the speed curves corresponding to the wet runway, a speed curve whose similarity to the second standard speed curve reaches a second threshold is selected and recorded as a second speed curve; screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, and determining a standard speed curve of the aircraft wheels under the thin ice runway condition according to the screening result, recorded as a third standard speed curve; According to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, multiple speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway conditions is determined according to the screening results, which is recorded as a fourth standard speed curve.

3. The aircraft brake controller simulation test method according to claim 2, characterized in that: According to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, a plurality of speed curves corresponding to the thin ice runway are screened, and a standard speed curve of the aircraft wheels under the thin ice runway condition is determined according to the screening result, which is recorded as a third standard speed curve, including: Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the first speed curve to determine a first candidate speed curve corresponding to the thin ice runway; Screening a plurality of speed curves corresponding to the thin ice runway according to the load state and climate conditions corresponding to the second speed curve to determine a second candidate speed curve corresponding to the thin ice runway; According to the correlation between the thin ice runway and the dry runway and the first alternative speed curve, as well as the correlation between the thin ice runway and the wet runway and the second alternative speed curve, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined and recorded as a third standard speed curve.

4. The aircraft brake controller simulation test method according to claim 3, characterized in that: According to the correlation between the thin ice runway and the dry runway and the first alternative speed curve, and the correlation between the thin ice runway and the wet runway and the second alternative speed curve, a standard speed curve of the aircraft wheels under the thin ice runway condition is determined, which is recorded as a third standard speed curve, including: according to Determine a standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve; Wherein, V3 is the standard speed curve of the aircraft wheels under the thin ice runway condition, recorded as the third standard speed curve, r1 is the correlation between the thin ice runway and the dry runway, is the i-th first candidate speed curve, r2 is the correlation between the thin ice runway and the wet runway, The i-th second candidate speed curve.

5. The aircraft brake controller simulation test method according to claim 2, characterized in that: According to the load state and climate conditions corresponding to the first speed curve and the load state and climate conditions corresponding to the second speed curve, a plurality of speed curves corresponding to the snow-covered runway are screened, and a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined according to the screening result, which is recorded as a fourth standard speed curve, including: Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the first speed curve to determine a third candidate speed curve corresponding to the snow-covered runway; Screening a plurality of speed curves corresponding to the snow-covered runway according to the load state and climate conditions corresponding to the second speed curve to determine a fourth candidate speed curve corresponding to the snow-covered runway; According to the correlation between the snow-covered runway and the dry runway and the third alternative speed curve, as well as the correlation between the snow-covered runway and the wet runway and the fourth alternative speed curve, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined and recorded as the fourth standard speed curve.

6. The aircraft brake controller simulation test method according to claim 5, characterized in that: According to the correlation between the snow-covered runway and the dry runway and the third alternative speed curve, and the correlation between the snow-covered runway and the wet runway and the fourth alternative speed curve, a standard speed curve of the aircraft wheels under the snow-covered runway condition is determined, which is recorded as the fourth standard speed curve, including: according to Determine a standard speed curve of the aircraft wheels under the snow-covered runway condition, recorded as a fourth standard speed curve; Wherein, V4 is the standard speed curve of the aircraft wheels under the condition of the snow-covered runway, recorded as the fourth standard speed curve, r3 is the correlation between the snow-covered runway and the dry runway, is the kth third candidate speed curve, r4 is the correlation between the snow runway and the wet runway, It is the fourth candidate speed curve mentioned in the kth item.

7. The aircraft brake controller simulation test method according to claim 1, characterized in that: According to the target load state and the target climate condition, determining a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test, including: Determining a first speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target load state and the load state corresponding to the target standard speed curve; Determining a second speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the similarity between the target climate condition and the climate condition corresponding to the target standard speed curve; According to the first speed correction coefficient and the second speed correction coefficient, a speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test is determined.

8. An aircraft brake controller simulation test device, characterized in that: include: An acquisition module is used to acquire the standard speed curve of the aircraft wheels under various runway conditions, as well as the target runway conditions, target load states and target climate conditions corresponding to the brake controller of the aircraft to be tested during the simulation test; A first processing module is used to determine a target standard speed curve required by the brake controller of the aircraft to be tested during the simulation test from each of the standard speed curves according to the target runway condition; The second processing module is used to determine the speed correction coefficient corresponding to the brake controller of the aircraft to be tested during the simulation test according to the target load state and the target climate condition; The simulation test module is used to correct the target standard speed curve according to the speed correction coefficient to obtain a corrected speed curve, so as to perform a simulation test on the brake controller of the aircraft to be tested based on the corrected speed curve.

9. A terminal, characterized in that: The method comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method as claimed in any one of claims 1 to 7 are implemented.

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