CN110606195B - Airplane emergency braking system and design method thereof - Google Patents
Airplane emergency braking system and design method thereof Download PDFInfo
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- CN110606195B CN110606195B CN201910877026.7A CN201910877026A CN110606195B CN 110606195 B CN110606195 B CN 110606195B CN 201910877026 A CN201910877026 A CN 201910877026A CN 110606195 B CN110606195 B CN 110606195B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C25/00—Alighting gear
- B64C25/32—Alighting gear characterised by elements which contact the ground or similar surface
- B64C25/42—Arrangement or adaptation of brakes
- B64C25/44—Actuating mechanisms
- B64C25/46—Brake regulators for preventing skidding or aircraft somersaulting
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Abstract
An aircraft emergency braking system and a design method thereof. A brake oil port of a hydraulic electromagnetic valve in the aircraft emergency brake system is communicated with an oil inlet of a hydraulic cylinder seat of the aircraft wheel. The oil inlet of the hydraulic pressure reducing brake valve is externally connected with a hydraulic source. One binding post of the single-knife double-position switch of the hydraulic relay is connected with a direct current power supply, and the other binding post is connected with an electromagnet of the hydraulic electromagnetic valve through a lead. When the oil pressure from the hydraulic pressure reducing brake valve reaches the contact pressure of the hydraulic relay, the contact of the hydraulic relay is conducted, and the direct-current power supply is conducted with the electromagnet on the hydraulic electromagnetic valve, so that the pressure of the hydraulic electromagnetic valve is relieved, and the pressure of an emergency brake system with an active anti-skid brake function is reduced. The emergency braking system with the active anti-skid braking function can compare the actual braking pressure with the braking pressure value set by the system, so that the braking pressure is actively regulated, and the purpose of active anti-skid is achieved.
Description
Technical Field
The invention relates to the field of aircraft braking systems, in particular to an emergency braking system with an active anti-skid braking function and a method for optimizing parameters of accessories in the system.
Background
To ensure safe landing and ground control of the aircraft, the requirements and regulations of an emergency brake system in the general standards (GJB 2879A-2008) of the antiskid brake control system of the aircraft are as follows: "in the event of failure or failure of the normal braking system, the emergency braking system must safely brake the aircraft, and the emergency braking system and the normal braking system must be independent of each other.
The emergency braking system of the aircraft is mainly braked by adopting a manual operation mode and consists of a single hydraulic pressure reducing brake valve or an air pressure reducing brake valve. The emergency braking system has no anti-skid function, and the output emergency braking pressure is in direct proportion to the operating force.
The on-off anti-slip control principle is adopted in a brake system of the Su 27 aircraft, and accessories of the normal brake system comprise a decompression valve, a modulator, an electromagnetic valve and an anti-slip automatic device; the antiskid control accessory comprises a hydraulic switch, a speed sensor, an electromagnetic valve and an antiskid automatic device. The brake oil port of the pressure reducing valve is communicated with the oil inlet of the hydraulic switch, the oil outlet of the hydraulic switch is communicated with the oil inlet of the modulator, the oil outlet of the modulator is communicated with the oil inlet of the electromagnetic valve, and the brake oil port of the electromagnetic valve is communicated with the oil inlet of the anti-skid automatic device; the anti-skid automatic device brake oil port is communicated with the brake device; one binding post of the hydraulic switch is communicated with a power supply, the other binding post of the hydraulic switch is communicated with one end of a front wheel speed sensor, and the other end of the front wheel speed sensor is communicated with an electromagnet of the electromagnetic valve through a lead; the oil return port of the pressure reducing valve is communicated with the oil tank through an oil return pipe; an oil return port of the electromagnetic valve is communicated with the oil tank through a pipeline; the oil inlet of the pressure reducing valve is externally connected with a hydraulic source through a pipeline. In the braking process, if a certain wheel is jammed or the wheel is decelerated too hard, the anti-slip control system works, the anti-slip control system consists of an electric part and a mechanical part, after the aircraft lands, a front wheel speed sensor switch is switched on, a wheel speed sensor is switched off, when the rotating speed of the wheel is reduced to a certain value corresponding to the linear speed, a speed sensor switch on the wheel is switched on, so that an electromagnetic valve works, brake oil is cut off, a brake device is communicated with an oil return path, and braking is released. The wheel speed sensor is normally closed, the front wheel speed sensor is normally open, and the function of the wheel speed sensor is to disconnect a circuit of an anti-slip system when the speed of the airplane is low, and the anti-slip control is completely borne by a mechanical part. The anti-slip robot is a main accessory for mechanical anti-slip. When the angular speed of the wheel reaches a given value, the oil return valve of the anti-skid automatic device is opened, so that the wheel releases the brake. And braking after the trailing tire is released.
The brake system of the Su 27 aircraft consists of simple hydraulic and electric accessories, has complex structure and poorer anti-skid function, but adopts a double-signal working mode and adopts a tire dragging automatic machine and a hydraulic limiter, thereby improving the anti-skid function and having the characteristics of safe system, stable brake and higher brake efficiency. However, the brake system of the Su 27 aircraft adopts a normal anti-skid brake system based on an on-off anti-skid control principle, and is not an emergency brake system.
The invention with the application number 201610902426.5 creates an electronic anti-skid brake system for an airplane, which ensures the emergency brake operation, and comprises a normal brake system and an emergency brake system. The normal braking system mainly comprises a braking valve, an electrohydraulic servo valve, a control box and a wheel speed sensor; the emergency braking system mainly comprises an emergency braking valve, a switching valve and a switch, and the normal braking system and the emergency braking system are connected and switched through the switching valve. The normal braking system and the emergency braking system adopt two independent pressure supply systems. The invention improves the system structure by adding the control device, so that the normal braking is disabled during the emergency braking, the complete conversion of the conversion valve under the action of the emergency braking pressure is ensured, and even if the emergency braking is used together with the normal braking, the conversion valve can be converted into an emergency braking system. Thereby ensuring the implementation of the emergency brake and fundamentally eliminating the failure and accident hidden trouble of the emergency brake caused by the simultaneous use of the emergency brake and the normal brake. But the emergency braking system of the invention has no anti-skid function.
The invention with the application number of 201610902427.X creates an aircraft brake system for preventing improper use of emergency brakes, including a normal brake system and an emergency brake system. The normal braking system comprises a braking instruction sensor, an electromagnetic hydraulic lock, an electrohydraulic servo valve, a control box and a wheel speed sensor. The emergency braking system comprises an emergency braking valve, a switching valve and a switch. The normal braking system and the emergency braking system are connected and switched through the switching valve. The invention can force the normal braking system to release pressure if the normal braking is used during the emergency braking, so that the normal input port of the switching valve is not pressurized, and the switching valve is ensured to be completely switched to the emergency braking system, thereby ensuring the implementation of the emergency braking and fundamentally eliminating the failure and accident hidden trouble of the emergency braking caused by the simultaneous use of the emergency braking and the normal braking. But the emergency braking system of the invention has no anti-skid function.
The invention with the application number 201610906014.9 creates an aircraft inertia anti-skid braking system for ensuring emergency braking, which consists of a normal braking system and an emergency braking system, wherein the normal braking system and the emergency braking system adopt two independent pressure supply source systems and are converted through a conversion valve. The invention improves the system structure by adding the control device, so that the normal braking is disabled during emergency braking, and the complete conversion of the conversion valve under the action of emergency braking pressure is ensured. But the emergency braking system of the invention has no anti-skid function.
The invention with the application number 201811188978.X creates a remote-operated emergency brake system and a design method thereof, and the invention directly controls an electromagnetic hydraulic lock and an electrohydraulic pressure servo valve which are arranged in a main landing gear cabin by a brake command sensor arranged in a cockpit, thereby realizing the remote operation of the emergency brake system. The electromagnetic hydraulic lock and the electrohydraulic pressure servo valve which are arranged in the main landing gear cabin are connected to a hydraulic source nearby, and the hydraulic pipeline of the brake system is arranged in the main landing gear cabin close to the brake wheels, so that the problem that the hydraulic pipeline must enter the cabin is solved, the length of the hydraulic pipeline is reduced, the emergency brake system is easy to maintain, and the complexity and the maintenance difficulty of the emergency brake system are reduced. But the emergency braking system of the invention has no anti-skid function.
Through searching, the emergency braking system in the prior art has no anti-skid function, and the schematic diagram of the emergency braking system with no anti-skid function is shown in the emergency braking system of a certain machine in fig. 1. The braking pressure is lower than that of a normal braking system, the emergency braking system has no anti-skid function, and the emergency braking system has no data of related active anti-skid braking control. The emergency braking system relies on a pilot to control an emergency braking handle to enable an emergency braking valve to output braking pressure, so that an emergency braking control is realized for braking an aircraft, but the emergency braking system without the active anti-skid function has no anti-skid function, and if under the special conditions of raining, ice, snow, oil runways and the like, the binding force moment of the ground is suddenly reduced, and as long as the braking moment is larger than the binding moment of the ground, the emergency braking system can not release pressure through active anti-skid, so that the locomotive dragging or tire burst accident can be caused.
Disclosure of Invention
The invention provides an airplane emergency braking system and a design method thereof, which aim to overcome the defect that an emergency braking system without an active anti-skid function in the prior art can cause accidents of tire dragging or tire burst of an airplane when the braking moment is larger than the ground combined moment.
The aircraft emergency braking system provided by the invention comprises a hydraulic electromagnetic valve, a hydraulic relay, a hydraulic pressure reducing braking valve and a 28V direct current power supply; wherein: the brake oil port of the hydraulic pressure reducing brake valve is respectively communicated with the oil inlet of the hydraulic relay and the oil inlet of the hydraulic electromagnetic valve through a pressure oil pipe; the oil return port of the hydraulic pressure reducing brake valve is communicated with the oil tank through an oil return pipe. The brake oil port of the hydraulic solenoid valve is communicated with the oil inlet of the hydraulic cylinder seat of the machine wheel. The oil return box of the hydraulic electromagnetic valve is communicated with the oil tank through a pipeline. And an oil inlet of the hydraulic pressure reducing brake valve is connected with a hydraulic source through a pipeline. One binding post of the single-pole double-set switch in the hydraulic relay is connected with a 28V direct current power supply, and the other binding post of the single-pole double-set switch in the hydraulic relay is connected with an electromagnet in the hydraulic electromagnetic valve through a wire. And oil return ports of the hydraulic pressure reducing brake valve, the hydraulic relay and the hydraulic electromagnetic valve are communicated with the oil tank through oil return pipes.
The 28V direct current power supply is communicated with a normally open contact of the positive electrode of the hydraulic relay; the contact of the negative electrode of the hydraulic relay is connected with the positive electrode of the hydraulic electromagnetic valve; the negative pole of the hydraulic electromagnetic valve is connected to the ground wire of the aircraft power supply system. When the oil pressure is equal to or greater than the contact pressure of the hydraulic relay, the contact of the hydraulic relay is switched on, the 28V direct current power supply is switched on with the hydraulic electromagnetic valve, and the pressure of the emergency braking system is reduced.
The design process of the aircraft emergency braking system provided by the invention is as follows:
Step 1, determining emergency brake pressure P s of an emergency brake system:
Determining emergency brake pressure P s through axial thrust S t of the brake wheel emergency brake device and brake wheel emergency brake pressure P se;
And I, determining axial thrust S t of an emergency brake device of the brake wheel:
The axial thrust S t of the emergency braking device of the braking machine wheel is determined according to the formula (1):
In the formula (1), L s is the braking distance required by the aircraft, R is the inner radius of a movable disc, R is the outer radius of a static disc, mu is the dynamic friction coefficient, A s is the kinetic energy at the landing moment of the aircraft during landing, N ms is the number of friction surfaces, and R g is the rolling radius of the aircraft wheel.
II, determining emergency brake pressure P se of the brake wheel:
Determining the emergency brake pressure P se of the brake wheel through a formula (2):
In the formula (2), N hs is the number of pistons, F hs is the piston area, and Δp is the pressure loss.
III determining the emergency brake pressure P s of the emergency brake system:
And determining the emergency brake pressure P s of the emergency brake system through a formula (3).
Ps＝Pse+Pi (3)
In the formula (3), P i is a system pressure safety margin.
The emergency brake pressure P s of the emergency brake system is the same as the emergency brake pressure P se of the brake wheel.
Step two, determining the intermediate brake pressure P s1 of the emergency brake system:
the intermediate brake pressure P s1 of the emergency brake system is determined according to equation (4).
Ps1＝η×(Pse-ΔP)+ΔP (4)
In the formula (4), eta is the pressure efficiency of the brake system; Δp is the pressure loss.
Step three, determining a slip period T s of an emergency braking system with an active anti-slip braking function:
The slipping period T s is that the emergency braking pressure of the emergency braking system is increased from the middle braking pressure to the contact pressure of the hydraulic relay, so that the contact of the hydraulic relay is connected, and the emergency braking pressure of the emergency braking system is relieved through the hydraulic electromagnetic valve; and the process of reducing the brake pressure of the emergency brake system to the middle brake pressure.
According to the test data of the braking system, the number of skidding times of the braking system is not more than 3-5 times per second under the test load of 1/2 tyre compression amount of the normal anti-skidding braking system, and the braking system is normal.
The slip period T s is determined by the formula (5):
And step four, determining the maximum braking pressure P m and the middle braking pressure P z of the hydraulic pressure reducing brake valve.
The brake pressure of the hydraulic pressure reducing brake valve includes a maximum brake pressure P m and an intermediate brake pressure P z.
The maximum braking pressure P m of the hydraulic pressure reducing brake valve is determined by a formula (6):
Pm＝Ps (6)
The intermediate brake pressure P z of the hydraulic pressure reducing brake valve is determined by the formula (7):
Pz＝Ps1 (7)
In the formula (6) and the formula (7), P m is the maximum brake pressure output by the hydraulic pressure reducing brake valve; p z is the intermediate brake pressure output by the hydraulic pressure reducing brake valve.
When the active anti-skid emergency braking system is applied, the emergency braking system with the active anti-skid braking function is divided into three layers:
when the operating force of the first level is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98MPa;
When the operating force of the second level is more than 98N and less than or equal to 280+/-20N, the output braking pressure is more than 0.98MPa and less than or equal to 4.5+/-0.5 MPa; the output braking pressure of 4.5+/-0.5 MPa is the middle braking pressure; when the output braking pressure is 0.98-4.5+/-0.5 MPa, the braking machine wheel cannot be locked or burst;
When the operating force of the third level is more than 280+/-20N and less than or equal to the maximum value 1080+/-50N, the output braking pressure is more than 4.5+/-0.5 MPa and less than or equal to 8+/-0.5 MPa; when the output braking pressure is 4.5+/-0.5 MPa to 8+/-0.5 MPa, the braking pressure is larger than the switching-on pressure of the hydraulic relay, the hydraulic electromagnetic valve is electrified, and the braking pressure of the emergency braking system with the active anti-skid braking function is reduced.
Step five, determining the on pressure and the off pressure of the hydraulic relay:
Determining the on pressure P 2 of the hydraulic relay through a formula (8), and determining the off pressure P 1 of the hydraulic relay through a formula (9);
P2＝Pse (8)
P1＝Ps1 (9)
In the formula, P se is the emergency brake pressure of the brake wheel, and P s1 is the intermediate brake pressure of the emergency brake system with the active anti-skid brake function.
When the determined switching-on pressure P 2 of the hydraulic relay is smaller than the braking pressure output by the hydraulic pressure reducing braking valve, the hydraulic relay is contacted; and when the disconnection pressure P 1 of the hydraulic relay is larger than the brake pressure output by the hydraulic pressure reducing brake valve, the contact of the hydraulic relay is disconnected. The connection pressure P 2 of the hydraulic relay is the same as the maximum brake pressure P m output by the hydraulic pressure reducing brake valve; the opening pressure P 1 of the hydraulic relay is the same as the intermediate brake pressure P z output by the hydraulic pressure reducing brake valve.
The design of the emergency braking system with the active anti-skid braking function is completed.
The invention is composed of a hydraulic pressure reducing brake valve, a hydraulic relay and a hydraulic electromagnetic valve, and forms an emergency brake system with an active anti-skid function. Emergency braking system working principle with active anti-skid braking function:
1) The pilot presses the emergency brake handle when the emergency brake switch is turned on, the output brake pressure of the hydraulic pressure reducing brake valve 4 is smaller than the middle brake pressure, and the emergency brake system with the active anti-skid function does not work.
2) When the brake pressure output by the hydraulic pressure reducing brake valve 4 is larger than the intermediate brake pressure P s1 of the emergency brake system, the emergency brake system with the active anti-skid function works; when the brake pressure output by the hydraulic pressure reducing brake valve 4 is larger than the maximum brake pressure P s of the emergency brake system and is higher than the contact pressure of the hydraulic relay, the hydraulic relay 3 is contacted, and meanwhile, the hydraulic electromagnetic valve 2 is electrified, so that the emergency brake pressure is reduced; when the brake pressure of the hydraulic pipeline is lower than the contact breaking pressure of the hydraulic relay 3, the contact of the hydraulic relay 3 is broken, the hydraulic electromagnetic valve 2 is powered off, and the emergency brake pressure rises. The pilot presses the emergency brake handle to the bottom, and the emergency brake system performs brake control according to the preset control rate until the aircraft is braked.
The brake pressure curve of the emergency brake system with the active anti-skid brake function is shown in fig. 3 when the emergency brake system works.
In order to overcome the defect that an emergency braking system without an active anti-skid function in the prior art can cause a tire dragging or tire burst accident when the braking moment is larger than the ground combined moment, the invention provides an aircraft emergency braking system and a design method thereof on the basis of researching a test curve in a normal braking system factory, referring to the references of a test flight, a test and a use conclusion of a normal braking system in an external field and the like. The emergency brake switch is disconnected, the emergency brake system with the active anti-skid brake function does not work, the pilot presses the emergency brake handle, and the hydraulic pressure reducing brake valve outputs brake pressure. The pilot has obvious difference of force sense in the operation process, and can realize safe and reliable braking by virtue of pilot operation. Because the pilot has the difference of sense of force in the operation process, the emergency braking system with the active anti-skid braking function is convenient to use and has good man-machine interface. When the operating force is small, the output brake pressure is lower than the middle brake pressure, so that safe and reliable braking can be realized; when the operating force is increased and the force sense is obvious, the emergency braking system with the active anti-skid braking function can compare the actual braking pressure with the braking pressure value set by the system when the output braking pressure is above the middle braking pressure, so that the braking pressure is actively adjusted, and the purpose of active anti-skid is achieved. Realizing safe braking.
According to the requirements of HB5648 on braking moment in the design specification of aircraft wheel and brake device, the friction coefficient of the wheel and the ground is 0.35-0.55. The moment acting on the wheel during the braking of the wheel comprises a braking moment M s and a ground combined moment M c, and has three states: m s＜Mc、Ms is close to M c and M s＞Mc.
When M s＞Mc, the machine wheel slides without rolling; when M s＜Mc, the machine wheel rolls without sliding; when M c＝Ms, the wheel will be in an unstable equilibrium state. In HB5648, M s＜Mc or M s is near M c when the wheel is required to be braked.
During braking, the ground friction coefficient is continuously changed, resulting in a continuous change in the coupling moment M c. The braking moment M s of the machine wheel is smaller than the binding force moment M c, the braking machine wheel cannot be locked or burst, the braking efficiency is high, the braking distance is short, and landing is safe.
The invention solves the defect that the braking system can cause the tire dragging or tire burst accident when the braking moment is larger than the ground combined moment by adding the active anti-skid braking function in the emergency braking system, and the invention does not adopt the conventional practice of the personnel in the field to require the pilot to adopt the point braking operation when the pilot uses the emergency braking or reduce the braking pressure under the condition of meeting the braking distance efficiency of the airplane. The working intensity of pilots is lightened, and the landing safety of the aircraft is ensured.
The invention has two points:
1, adding an active anti-skid brake control function in an emergency brake system; the brake system is used for solving the defect that when the brake moment is larger than the ground combined moment, the tire dragging or tire burst accident of the airplane can be caused, the working intensity of the pilot is lightened, the landing safety of the airplane is ensured, and the pilot does not need to adopt point brake operation to prevent the tire burst accident when using emergency brake.
And 2, the brake pressure PWM control of the emergency brake system. According to the invention, the pressure relay is selected, the emergency braking system is selected from normal braking system test and test experience, and the PWM control of the braking pressure of the emergency braking system is realized by controlling the flow and the pressure of the hydraulic pressure reducing braking valve. In summary, the invention aims to solve the practical problem of adding the anti-skid function in the emergency braking system, reducing the workload of pilots and avoiding tire burst accidents when the braking system is used. "
Drawings
FIG. 1 is a schematic diagram of an emergency braking system of a machine;
FIG. 2 is a schematic diagram of the structure of the present invention;
Fig. 3 is an operational curve of the present invention.
1. A wheel; 2. a hydraulic solenoid valve; 3. a hydraulic relay; 4. a hydraulic pressure reducing brake valve; 5. a pressure oil pipe; 6. an oil return pipe; 7. an oil tank; 8.28V DC power supply.
Detailed Description
The embodiment is an emergency braking system with an active anti-skid braking function, and comprises a hydraulic electromagnetic valve 2, a hydraulic relay 3, a hydraulic pressure reducing brake valve 4, a 28V direct current power supply 8 and an oil return pipe 6. Wherein: the brake oil port of the hydraulic pressure reducing brake valve 4 is respectively communicated with the oil inlet of the hydraulic relay 3 and the oil inlet of the hydraulic electromagnetic valve 2 through a pressure oil pipe 5; the oil return port of the hydraulic pressure reducing brake valve 4 is communicated with an oil tank 7 through an oil return pipe 6. The brake oil port of the hydraulic solenoid valve 2 is communicated with the oil inlet of the hydraulic cylinder seat of the machine wheel. The oil return box of the hydraulic electromagnetic valve 2 is communicated with an oil tank 7 through a pipeline. And an oil inlet of the hydraulic pressure reducing brake valve 4 is connected with a hydraulic source through a pipeline.
One binding post of the single-pole double-position switch in the hydraulic relay 3 is connected with a 28V direct-current power supply 8, and the other binding post of the single-pole double-position switch in the hydraulic relay 3 is connected with an electromagnet in the hydraulic electromagnetic valve 2 through a wire. When the hydraulic pressure reducing brake valve 4 works, when the brake pressure output by the hydraulic pressure reducing brake valve reaches the contact connection pressure of the hydraulic relay 3, the hydraulic relay is connected, the 28V direct current power supply is connected with the electromagnet on the hydraulic electromagnetic valve 2, so that the hydraulic electromagnetic valve 2 discharges oil and releases pressure, and the pressure of an emergency brake system with an active anti-skid brake function is reduced.
In the embodiment, a hydraulic source is connected to an oil inlet of the hydraulic pressure reducing brake valve 4 through a pipe joint of M12 and an oil pipe 5 with the length of 3.6M and the inner diameter of 5.5 mm; the brake oil port of the hydraulic pressure reducing brake valve 4 is connected with the hydraulic relay 3 through a three-way pipe, a pipe joint of M12 and an oil pipe 5 with the length of 0.2M, and the other joint of the three-way pipe joint is communicated with the oil inlet of the hydraulic electromagnetic valve 2 through the pipe joint of M12, the oil pipe 5 with the length of 2.1M and the inner diameter of phi 5.5 mm; the oil enters the hydraulic cylinder seat of the wheel 1 from the brake working port of the hydraulic electromagnetic valve 2 through the pipe joint of the M12 and the oil pipe with the length of 1.5M and the inner diameter of phi 5.5mm to push the hydraulic cylinder to work for braking.
The return pipe 6 connects the return oil of the hydraulic pressure reducing brake valve 4, the hydraulic relay 3 and the hydraulic solenoid valve 2, and connects the return oil to the oil tank 7, and leads the return oil to the oil tank 7 when the system brake pressure is reduced.
The 28V direct current power supply 8 of the aircraft power supply system is communicated with a normally open contact of the positive electrode of the hydraulic relay 3; the contact of the negative electrode of the hydraulic relay 3 is connected with the positive electrode of the hydraulic electromagnetic valve 2; the negative pole of the hydraulic solenoid valve 2 is connected to the ground of the aircraft power system. When the oil pressure is equal to or greater than the contact pressure of the hydraulic relay 3, the contact of the hydraulic relay 3 is switched on, the 28V direct current power supply is switched on with the hydraulic electromagnetic valve 2, and the pressure of the emergency braking system is reduced.
The embodiment also provides a design method of the emergency braking system with the active anti-skid braking function, which comprises the following specific processes:
Step one, determining emergency brake pressure P s of an emergency brake system with an active anti-skid brake function:
The emergency braking pressure P s of the emergency braking system with the active anti-skid braking function is determined through the axial thrust S t of the emergency braking device of the braking machine wheel and the emergency braking pressure P se of the braking machine wheel. The specific process is as follows:
And I, determining axial thrust S t of an emergency brake device of the brake wheel:
The axial thrust S t of the emergency braking device of the braking machine wheel is determined according to the formula (1):
In the formula (1), L s is the braking distance required by the aircraft, R is the inner radius of a movable disc, R is the outer radius of a static disc, mu is the dynamic friction coefficient, A s is the kinetic energy at the landing moment of the aircraft during landing, N mc is the number of friction surfaces, and R g is the rolling radius of the aircraft wheel.
In the embodiment, the braking distance required by the aircraft is L s =810 m, the inner radius R of the movable disc is=0.122 m, the outer radius R of the static disc is=0.162 m, and r+r is=0.284 m; dynamic friction coefficient μ=0.23; kinetic energy a s = 12000000J at landing moment of aircraft landing; the number of friction surfaces N mc =6; wheel roll radius R g = 0.365.
Bringing the data into equation (1) to obtain
II, determining emergency brake pressure P se of the brake wheel:
Determining the emergency brake pressure P se of the brake wheel through a formula (2):
In the formula (2), N hs is the number of pistons, F hs is the piston area, and Δp is the pressure loss.
In this embodiment, the number of pistons N hs =5; piston area F hs＝π×17.52＝961.625mm2; pressure loss Δp=1.2 MPa.
Bringing the data into equation (2) to obtain
III, determining emergency brake pressure P s of an emergency brake system with an active anti-skid brake function:
the emergency brake pressure P s is determined by equation (3).
Ps＝Pse+Pi (3)
In the formula (3), P i is a system pressure safety margin.
In the embodiment, the emergency brake pressure P s of the emergency brake system with the active anti-skid brake function is the same as the emergency brake pressure P se of the brake wheel, and the safety margin of the system operation is increased from the safety design point of view.
In this example, P i =1 MPa is substituted into formula (3), and P s =6.9+1=7.9 MPa.
In this embodiment, the emergency braking pressure P s =8±0.5MPa of the emergency braking system having the active anti-skid braking function.
Step two, determining the middle brake pressure P s1 of the emergency brake system with the active anti-skid brake function:
According to the description of the related distance efficiency and the pressure efficiency of a brake system of HB6080 general technical condition of an anti-skid brake control system of an airplane wheel, the external field use efficiency of the brake system is 60-80%.
The intermediate brake pressure P s1 is a brake pressure at which the brake wheel will not lock in any case.
And determining the intermediate brake pressure P s1 of the emergency brake system with the active anti-skid brake function according to the formula (4).
Ps1＝η×(Pse-ΔP)+ΔP (4)
In the formula (4), eta is the pressure efficiency of the braking system and is obtained by inquiring HB6080 general technical condition of an anti-skid braking control system of an airplane wheel; Δp is the pressure loss.
In this embodiment, the brake system pressure efficiency η=60%; the pressure loss was Δp=1.2 MPa. Bringing the data into equation (4) gives P s1 =4.68 MPa
In this embodiment, the intermediate brake pressure of the emergency brake system is determined as
Step three, determining a slip period T s of an emergency braking system with an active anti-slip braking function:
Slip period T s: the slipping period T s is that the emergency brake pressure of the emergency brake system with the active anti-slip brake function is increased from the middle brake pressure to the contact pressure of the hydraulic relay 3, so that the contact of the hydraulic relay is switched on, and the emergency brake pressure of the emergency brake system is relieved through a hydraulic electromagnetic valve; and the process of reducing the brake pressure of the emergency brake system to the middle brake pressure.
According to the test data of the braking system, the number of skidding times of the braking system is not more than 3-5 times per second under the test load of 1/2 tyre compression amount of the normal anti-skidding braking system, and the braking system is normal.
The slip period T s is determined by the formula (5):
In the embodiment, the slip period T s of the emergency braking system with the active anti-slip braking function is 0.2-0.3 s.
And step four, determining the braking pressure of the hydraulic pressure reducing brake valve.
The brake pressure of the hydraulic pressure-reducing brake valve 4 includes a maximum brake pressure P m and an intermediate brake pressure P z.
When the brake pressure of the hydraulic pressure reducing brake valve is less than or equal to the middle brake pressure, the handle has small operating force, and the brake is reliable and safe;
When the brake pressure of the hydraulic pressure reducing brake valve is determined to be the maximum brake pressure, the handle operating force is increased, the force sense is obvious, and the safety and reliability brake can be realized by the pilot operation.
When the emergency braking system with the active anti-skid braking function is applied, the emergency braking system is divided into three layers on a certain type of aircraft: the first level presses the brake handle, and when the operating force is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98MPa. The second level, when the operating force is more than 98N and less than or equal to 280+/-20N, the output braking pressure is more than 0.98MPa and less than or equal to 4.5+/-0.5 MPa; the output braking pressure of 4.5+/-0.5 MPa is the middle braking pressure; the brake wheel cannot lock or burst under the brake pressure of 0.98-4.5+/-0.5 MPa. The third level, when the operating force is more than 280 plus or minus 20N and less than or equal to 1080 plus or minus 50N of the maximum value, the output braking pressure is more than 4.5 plus or minus 0.5MPa and less than or equal to 8 plus or minus 0.5MPa; when the braking pressure is 4.5+/-0.5 MPa to 8+/-0.5 MPa, the braking pressure is larger than the switching-on pressure of the hydraulic relay 3, the hydraulic electromagnetic valve 2 is electrified, and the braking pressure of the emergency braking system with the active anti-skid braking function is reduced.
According to the use characteristics of the emergency braking system with the active anti-skid braking function, the maximum braking pressure P m of the hydraulic pressure reducing brake valve is determined according to a formula (6), and the middle braking pressure P z of the hydraulic pressure reducing brake valve is determined according to a formula (7).
Pm＝Ps (6)
Pz＝Ps1 (7)
P m is the maximum brake pressure output by the hydraulic pressure reducing brake valve; p z is the intermediate brake pressure output by the hydraulic pressure reducing brake valve.
In this embodiment, the emergency braking pressure P s =8±0.5MPa of the emergency braking system with the active anti-skid braking function and the intermediate braking pressure of the emergency braking system with the active anti-skid braking function are setCarrying out the operation in the formula (6) to obtain the maximum brake pressure of 8+/-0.5 MPa output by the hydraulic pressure reducing brake valve 4; the output intermediate braking pressure of the hydraulic pressure reducing brake valve 4 is 4.5+/-0.5 MPa.
Step five, determining the on pressure and the off pressure of the hydraulic relay:
When the brake pressure output by the hydraulic pressure reducing brake valve is larger than the switching-on pressure P 2 of the hydraulic relay, the hydraulic relay is contacted; when the brake pressure output by the hydraulic pressure reducing brake valve is smaller than the breaking pressure P 1 of the hydraulic relay, the contact of the hydraulic relay is broken. The connection pressure P 2 of the hydraulic relay is the same as the maximum brake pressure P m output by the hydraulic pressure reducing brake valve; the opening pressure P 1 of the hydraulic relay is the same as the intermediate brake pressure P z output by the hydraulic pressure reducing brake valve.
Determining the on pressure P 2 of the hydraulic relay through a formula (8), and determining the off pressure P 1 of the hydraulic relay through a formula (9);
P2＝Pse (8)
P1＝Ps1 (9)
In the formula, P se is the emergency brake pressure of the brake wheel, and P s1 is the intermediate brake pressure of the emergency brake system with the active anti-skid brake function.
P se = 6.9MPa andRespectively carrying into the formula (8) and the formula (9) to obtain the maximum braking pressure P 2 = 6.9MPa when the hydraulic relay is switched on, and the intermediate braking pressure/>, when the hydraulic relay is switched off
Thus, the design of the emergency braking system with the active anti-skid braking function is completed.
Claims (6)
1. An aircraft emergency braking system is characterized by comprising a hydraulic electromagnetic valve, a hydraulic relay, a hydraulic pressure reducing braking valve and a 28V direct current power supply; wherein: the brake oil port of the hydraulic pressure reducing brake valve is respectively communicated with the oil inlet of the hydraulic relay and the oil inlet of the hydraulic electromagnetic valve through a pressure oil pipe; the oil return port of the hydraulic pressure reducing brake valve is communicated with the oil tank through an oil return pipe; the brake oil port of the hydraulic electromagnetic valve is communicated with the oil inlet of the hydraulic cylinder seat of the machine wheel; the oil return box of the hydraulic electromagnetic valve is communicated with the oil tank through a pipeline; an oil inlet of the hydraulic pressure reducing brake valve is connected with a hydraulic source through a pipeline; one binding post of the single-pole double-set switch in the hydraulic relay is connected with a 28V direct-current power supply, and the other binding post of the single-pole double-set switch in the hydraulic relay is connected with an electromagnet in a hydraulic electromagnetic valve through a wire; and oil return ports of the hydraulic pressure reducing brake valve, the hydraulic relay and the hydraulic electromagnetic valve are communicated with the oil tank through oil return pipes.
2. The aircraft emergency brake system of claim 1, wherein the 28V dc power supply is in communication with a normally open contact of a hydraulic relay anode; the contact of the negative electrode of the hydraulic relay is connected with the positive electrode of the hydraulic electromagnetic valve; the negative electrode of the hydraulic electromagnetic valve is connected to the ground wire of the aircraft power supply system; when the oil pressure is equal to or greater than the contact pressure of the hydraulic relay, the contact of the hydraulic relay is switched on, the 28V direct current power supply is switched on with the hydraulic electromagnetic valve, and the pressure of the emergency braking system is reduced.
3. The method for designing an aircraft emergency braking system according to claim 1, wherein the specific process is as follows:
Step 1, determining emergency brake pressure P s of an emergency brake system:
Determining emergency brake pressure P s through axial thrust S t of the brake wheel emergency brake device and brake wheel emergency brake pressure P se;
And I, determining axial thrust S t of an emergency brake device of the brake wheel:
The axial thrust S t of the emergency braking device of the braking machine wheel is determined according to the formula (1):
In the formula (1), L s is the braking distance required by the aircraft, R is the inner radius of a movable disc, R is the outer radius of a static disc, mu is the dynamic friction coefficient, A s is the kinetic energy at the landing moment of the aircraft during landing, N ms is the number of friction surfaces, and R g is the rolling radius of the aircraft wheel;
II, determining emergency brake pressure P se of the brake wheel:
Determining the emergency brake pressure P se of the brake wheel through a formula (2):
In the formula (2), N hs is the number of pistons, F hs is the piston area, Δp is the pressure loss;
III determining the emergency brake pressure P s of the emergency brake system:
Determining an emergency brake pressure P s of the emergency brake system through a formula (3);
Ps＝Pse+Pi (3)
In the formula (3), P i is the system pressure safety margin;
Step two, determining the intermediate brake pressure P s1 of the emergency brake system:
determining an intermediate brake pressure P s1 of the emergency brake system according to formula (4);
Ps1＝η×(Pse-△P)+△P (4)
In the formula (4), eta is the pressure efficiency of the brake system; Δp is the pressure loss;
Step three, determining a slip period T s of an emergency braking system with an active anti-slip braking function:
The slipping period T s is that the emergency braking pressure of the emergency braking system is increased from the middle braking pressure to the contact pressure of the hydraulic relay, so that the contact of the hydraulic relay is connected, and the emergency braking pressure of the emergency braking system is relieved through the hydraulic electromagnetic valve; a process of reducing the brake pressure of the emergency brake system to a middle brake pressure;
According to the test data of the braking system, the number of skidding times of the braking system is not more than 3-5 times per second under the test load of 1/2 tyre compression amount of the normal anti-skidding braking system, and the braking system is normal;
the slip period T s is determined by the formula (5):
Determining the maximum braking pressure P m and the middle braking pressure P z of the hydraulic pressure reducing brake valve;
The braking pressure of the hydraulic pressure reducing brake valve comprises a maximum braking pressure P m and a middle braking pressure P z;
The maximum braking pressure P m of the hydraulic pressure reducing brake valve is determined by a formula (6):
Pm＝Ps (6)
The intermediate brake pressure P z of the hydraulic pressure reducing brake valve is determined by the formula (7):
Pz＝Ps1 (7)
In the formula (6) and the formula (7), P m is the maximum brake pressure output by the hydraulic pressure reducing brake valve; p z is the intermediate brake pressure output by the hydraulic pressure reducing brake valve;
step five, determining the on pressure and the off pressure of the hydraulic relay:
Determining the on pressure P 2 of the hydraulic relay through a formula (8), and determining the off pressure P 1 of the hydraulic relay through a formula (9);
P2＝Pse (8)
P1＝Ps1 (9)
In the formula, P se is the emergency brake pressure of the brake wheel, and P s1 is the intermediate brake pressure of an emergency brake system with an active anti-skid brake function;
the design of the emergency braking system with the active anti-skid braking function is completed.
4. A method of designing an aircraft emergency brake system according to claim 3, wherein in step five, the hydraulic relay is contacted when the determined contact pressure P 2 of the hydraulic relay is less than the brake pressure output by the hydraulic pressure reducing brake valve; when the disconnection pressure P 1 of the hydraulic relay is larger than the brake pressure output by the hydraulic pressure reducing brake valve, the contact of the hydraulic relay is disconnected; the connection pressure P 2 of the hydraulic relay is the same as the maximum brake pressure P m output by the hydraulic pressure reducing brake valve; the opening pressure P 1 of the hydraulic relay is the same as the intermediate brake pressure P z output by the hydraulic pressure reducing brake valve.
5. A method of designing an aircraft emergency braking system according to claim 3, wherein the emergency braking system with active anti-skid braking function is divided into three levels when in use:
when the operating force of the first level is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98MPa;
When the operating force of the second level is more than 98N and less than or equal to 280+/-20N, the output braking pressure is more than 0.98MPa and less than or equal to 4.5+/-0.5 MPa;
When the operating force of the third level is more than 280+/-20N and less than or equal to the maximum value 1080+/-50N, the output braking pressure is more than 4.5+/-0.5 MPa and less than or equal to 8+/-0.5 MPa.
6. The method of designing an aircraft emergency braking system according to claim 5, wherein the output braking pressure of 4.5 ± 0.5MPa is an intermediate braking pressure; when the output braking pressure is 0.98-4.5+/-0.5 MPa, the braking machine wheel cannot be locked or burst; when the output braking pressure is 4.5+/-0.5 MPa to 8+/-0.5 MPa, the braking pressure is larger than the switching-on pressure of the hydraulic relay, the hydraulic electromagnetic valve is electrified, and the braking pressure of the emergency braking system with the active anti-skid braking function is reduced.
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