System overview:
      The aero-braking system is an important part of aircraft, which has strong time-varying and nonlinear characteristics. The main function is to realize the safe, reliable, smooth and efficient braking of the aircraft in the case of landing and taxiing or RTO (Reject Take Off) , and to ensure certain directional maneuverability of the aircraft. Generally include normal braking system (including automatic braking) , backup braking system and emergency/stop braking system, etc. . The common brake system is generally composed of wheel speed sensor, brake command sensor, (automatic brake selector) , anti-skid Brake Control Unit, electro-hydraulic Servo Valve, hydraulic safety, shuttle Valve SHV, pressure sensor, wheel and brake device.

System Features:
        The simulation system is composed of anti-skid braking control unit, which outputs the brake pressure according to the request obtained by the brake pedal sensor or the automatic brake selector, and monitors the wheel speed signal, the reference speed of the aircraft is calculated, and the wheel skidding state is judged according to the change of the wheel speed signal, the anti-skid signal is calculated, and the output of the brake pressure is adjusted to release the wheel lock-up and restore the normal rolling state. Therefore, the safe, stable and efficient braking of aircraft is realized. Aircraft Braking relies on the friction provided by the tires and the ground when braking (also known as the binding force) , which converts the Kinetic Energy of the aircraft into the heat energy of the braking devices (brake discs) and consumes it, while also preventing excessive wear or “Blowout”of the tires, to achieve the safety of aircraft braking. The friction varies non-linearly with the tire load, the slip ratio and the runway state. The anti-skid Braking hardware-in-the-loop simulation test platform designed by US can not only realize the full digital simulation of the braking system, but also realize the semi-physical simulation. And a comprehensive simulation of aircraft landing conditions (multi-wheel, single theory, symmetric, asymmetric, variable load, cross-wind, dry, wet, water, snow, etc.) under the aircraft braking situation, and with the following test functions:
     1) Simulation and verification of the input-output relationship of a single product;

     2)Simulation and verification of structure principle and design parameters of single product;

     3) The Control Law of Brake Control Unit is designed and verified by simulation

     4)Hydraulic and electric brake system function and performance simulation validation (including all digital and semi-physical simulation test) ;

     5) Fault/safety simulation and verification of system and accessory products

     6) Data recording, storage, processing system and real-time scene display;

     7) Can carry on the aircraft two (or six) degrees of freedom condition simulation;

     8) That can simulate the actions of a driver

        The simulation test-bed system can be used to simulate the actual working condition of the aircraft anti-skid braking system, real-time software simulation of aircraft motion and dynamic process, runway condition, landing gear mechanical characteristic and brake device pressure/torque characteristic is realized. Take the relevant accessories of the brake as the object, the rest part can be either hardware or software, and carry on the comprehensive simulation test of the large system. The hardware-in-the-loop simulation test of aircraft braking system realizes the simulation of take-off and landing in all kinds of environments, which provides theoretical and experimental basis for product design, improvement and parameter optimization. The hardware-in-the-loop Simulation test-bed of brake system is composed of physical part, measurement and control part, simulation and control part and cockpit simulation part.

Key components of the system:

Create a simulation model of each subsystem:

Physical Part:
        This part includes: Brake Control Unit, hydraulic/all-electric simulation system, visual part and so on. The hydraulic simulation part mainly simulates the airplane braking system using traditional hydraulic power All-electric simulation system for the new aircraft design, including all-electric actuator, feedback sensors, brakes, and so on.

Measurement and control:

The key link of the whole test is responsible for the collection, processing, operation, reality, model establishment, solution, control and correction of every input and output interface of the system.

Simulation control part:
        It is mainly composed of simulation computer and control software. Responsible for aircraft braking system modeling and configuration, software real-time simulation and debugging. And can be separated from the real part of the system for digital simulation.

Simulation part:
        By the brake operation, monitoring display, brake control and other parts. The braking operation part is a subsystem which simulates the actual operation of the pilot’s brake, and turns the pilot’s pedal brake into the corresponding hydraulic pressure reducing control pressure signal, or the corresponding proportional electronic control signal. The Monitor display part is to monitor the status of each part of the system, and the image is displayed in front of the audience. The brake control part mainly simulates the brake control and the hydraulic system remote control in the cockpit.

System Features and advantages:
        At present, the application of multi-processor based on real-time operating system (RTOS) to the simulation and calculation of the steady and dynamic characteristics of the aero-braking system is very extensive in the aero-braking simulation system of the relevant research institutions and units at home and abroad. For a brake system which exists or is still being developed, a computer program including the steady-state and dynamic processes of each subsystem can be compiled, the dynamic parameters and performance parameters of the braking system and its accessories can be obtained through the program calculation, which is very close to the prototype operation of the real braking system in the test workshop, it can also greatly reduce the risk of full-scale physical test under extreme conditions and special variables and protect the investment.

This test system can improve team efficiency in the following R & D AND OPTIMIZATION DESIGN:
       1. Study the influence and relationship of tire structure, runway condition, brake system dynamic characteristic and buffer structure characteristic on anti-skid Brake System Control Law, test the new brake control algorithm.

2. Study how to avoid the interaction of brake and landing gear vibration: based on the quantitative relationship between the stiffness of the landing gear Strut, the rotation speed of the wheel, the rolling radius, the vibration period, the amount of skid set by the anti-skid brake system and the brake Torque, as a whole, the friction between the brake disc and the static disc can be avoided to induce the “Walk”and “Squeal”of the main landing gear.

3. How to improve the efficiency of aircraft anti-skid braking system and the reliability of structure and motion function under various working conditions to realize the optimal design of brake system parameters.

4. To study the influence of different brake materials on the braking process, it is required that the torque change from high speed to low speed is small and too smooth.

5. The quantitative and qualitative evaluation and analysis of component level, component level and system level brake faults are carried out by means of computer semi-physical simulation. The hardware-in-the-loop simulation system of air brake is designed and implemented according to the actual demand, which takes the high-performance real-time simulation computer as the core and is equipped with other simulation and physical equipment, can provide aircraft brake system design, development, testing and semi-physical simulation, the Hardware In the Loop (Hil: Hardware In the Loop) simulation test, sensor signal simulation and digital modeling environment of landing gear, brake, wheel/runway etc. , the simulation conditions are more close to the actual situation, and the performance of the designed controller can be tested and debugged correctly, which is beneficial to the development of new control rate and Algorithm and to the reduction of on-site debugging. Through the actual simulation test, it is proved that the semi-physical simulation can shorten the development cycle, reduce the development of wood, and improve the development efficiency, it can meet the simulation requirements of parameters optimization, model validation and prediction of flight test results for aircraft braking and accessory unit simulation control system.

Category: Electronic System Simulation