Aircraft Antiskid Brake Control Valve

1
Aircraft Antiskid Brake Control Valve

• Jeremy Goldin
• Mechatronics ECE 5320 Sensor/Actuator Literature
  Survey Assignment 1
• Dept. of Electrical and Computer Engineering
• Utah State University
• E jeremy.goldin_at_aggiemail.usu.edu
• F [phone] (ECE Dept.)

March 7, 2010
2
Outline

• Reference list
• To probe further
• Detailed References and Handbooks
• Introduction
• Major Applications
• History
• Basic Operating Principle
• Major Specifications
• Limitations
• Benefits

3
Reference list

• Crane Aerospace (2010).
• 1 Antiskid Tutorial Technical Document, June
  2000. From http//www.craneae.com/Products/Landin
  g/downloads/AntiskidTutorial.pdf
• 2 Antiskid Systems Solutions for Regional
  Aircraft Technical Document, June 2000. From
  http//www.craneae.com/products/landing/downloads/
  RegionalSystems.pdf
• IEEE Transactions on Control Systems Technology,
  Vol. 9, No. 2
• 3 I. Tunay, E. Rodin, A. Beck, Modeling and
  Robust Control Design for Aircraft Brake
  Hydraulics, March 2001.

4
Reference List

• 4 Norman S. Currey - Aircraft Landing Gear
  Design Principles and Practices, AIAA Education
  Series, 1988, ISBN 0930403-41-X
• 5 Hirzel, E.A., Antiskid and Modern Aircraft,
  SAE Paper 720868, Oct 1972

5
To explore further

• http//en.wikipedia.org/wiki/Anti-lock_braking_sys
  tem
• MIL-H-5440 - Hydraulic Systems, Aircraft, Type 1.
  Design, Installation, and Data Requirements
• MIL-B-8075D-1 Brake Control Systems, Antiskid, -
  Aircraft Wheels - General Specification for
• SAE Aerospace Recommended Practice ARP 1070
  Design and Testing of Antiskid Brake Control
  Systems for Total Aircraft Compatibility
• SAE Aerospace AIR 1739 Information on
  Antiskid Systems

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Introduction

• When an aircraft is implementing a landing, its
  obvious primary goal is to come to a controlled
  stop. At some point this stopping involves the
  application of wheel brakes, typically once the
  aircraft has completely settled a majority of its
  weight upon the ground.
• A major concern upon applying wheel brakes for a
  fast moving, high load object, is the possibility
  of skidding the tires and thus losing control of
  the stop.

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Introduction

• One solution to preventing the tires from
  skidding is by modulating the brake pressure that
  is being applied to the brake, so that some of
  that pressure is returned to the system and thus
  the brake pressure is reduced at the brake and
  the wheel will spin back up (i.e. stop skidding).
  
• Another form of this method is to have even the
  brake pedal signal be electronic so that the
  brake pressure doesnt have to be released at the
  valve, but rather just the brake command to the
  valve is reduced.
• Control of the brake valve would be accomplished
  through the use of a controller and a speed
  sensing device.

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Major Applications

• Hydraulic Valves are very common, and all
  hydraulic braking systems use brake valves to
  apply pressure to the brake. A brake control or
  antiskid valve is a specific subset of these
  types of valves.

Figure 1 Antiskid Control Loop 1
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Major Applications

• The brake control or antiskid valve is usually in
  addition to the typical hydraulic valve that
  applies pressure to the brakes, although they can
  be combined. Its usual purpose is not to apply
  pressure to the brake, but rather to release
  pressure according to a controller that is
  determining over-braking conditions (e.g.
  skidding).
• Some systems combine the braking valve and the
  antiskid valve into a single valve, and so its
  purpose is to apply brake pressure according to a
  combination of pilot input and a brake controller.

10
History

• Aircraft Brake Control Valves were first
  introduced as part of an antiskid control system

• 1929 - The first system was introduced by Gabriel
  Voisin a simple valve was placed in

the path of the brake line and connected to a
local reservoir. The valve was controlled by a
flywheel that would open the valve when it spun
faster than a drum connected to the wheel
Figure 2 Typical Modern Brake Control Valve 2
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History

• 1946 Hydro-aire Hytrol System implemented on
  the B-47. Utilized a simple solenoid based valve
  that would either be completely closed and apply
  all pressure commanded by the brake master
  cylinder or completely release (to system
  pressure) all pressure going to the brake
• 1960s Hydro-aire Mark II System available
  utilized a servo-based valve that could modulate
  the amount of brake pressure that would be
  applied to the brake

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Basic Operating Principle

• There are 2 broad application types of Brake
  Control Valves
• Antiskid Control Valve (Release Commanded Valve)
• Brake By Wire Valve (Application Commanded Valve)
• These application types are most commonly
  implemented as electro-hydraulic pressure valves

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Basic Operating Principle

• These types of valves typically include the
  following characteristic
• Two Hydraulic Stages
• The first stage is a small amount of fluid
  slightly separated from the body and it acts to
  adjust the pressure according to the movement of
  the lever inside which is activated by the
  attached electric servo
• The second stage is the primary body of the valve
  where the real pressure fluid fluctuations are
  occurring. It responds to the changes in pressure
  balance of the first stage to react similarly.
  This is similar to a cascaded controller system,
  where the first stage is the controller and the
  second stage is the plant modified by a gain

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Antiskid Control Valve

• The complexity of the servo actuation and
  pressure regulation varies by implementation, but
  the basic principle is that a current is applied
  to an attached servo.

Figure 3 Brake Control Valve Schematic 2
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Antiskid Control Valve

• Varying current levels through the solenoid will
  apply various amounts of force to an internal
  poppet that will move between return and metered
  pressure, thus modulating the amount of pressure
  being sent to the brake.
• The key aspect to this valve is that the valve
  functions as a simple bypass when the servo is
  not activated, so it can only affect the pressure
  that is being applied, it cannot add pressure to
  the system.

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Brake By Wire Valve

• The Brake By Wire Valve is simpler than the
  antiskid valve, since it no longer has to
  modulate pressure through a servo. It only
  receives one input, which is to a servo,

and in a similar fashion to the antiskid
valve, will modify the location of a poppet to
equalize pressure within its body to send system
pressure to the brake.
Figure 4 Brake By Wire Control Valve 2
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Brake By Wire Valve

• The Brake By Wire Valve is dependent on a
  separate controller that converts the pilot input
  pedal command into brake pressure application
  (and adding skid control adjustments) which is
  commanded using the servo.

Figure 5 Brake By Wire Control Valve Schematic
2

• This valve can thus apply brake pressure by
  itself

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Major Specifications

• For aircraft usage, typical requirements for the
  antiskid valve involve basic hydraulic
  requirements, rather than specific to the
  antiskid valve
• Proof Pressure (Usually 1.5x operating pressure)
• Burst Pressure (Usually 2.5x operating pressure)
• Low Internal Leakage (Between Metered and
  System), dependent of operating pressure, but
  usually around max of 1000CCs/min
• Typical aircraft high environment requirements
  (vibration, shock, humidity, temperature, etc)
• Endurance requirements of electrical operation
  and pressure release/application cycles
  10,0000-20,000 cycles

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Limitations

• The use of Hydraulic Actuators are limited by the
  predominantly non-linear nature of hydraulic
  fluid and pressure responses
• Aspects of the system are difficult to measure or
  to estimate during operation
• Viscosity, Temperature, oil bulk modulus
• Despite typically offering fast responses due to
  low inertia of the valve, there are always issues
  with delays due to connecting lines

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Benefits

• Hydraulic power/actuators offer
• High power to weight ratio
• Reliable, self-lubricating operation
• The Antiskid valve fits simply within typical
  hydraulic braking systems
• Long history of hydraulic systems usage even
  though not well model-able, has established usage
  history. Modeling is worked around using Hardware
  in the Loop for the hydraulic systems

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Future Work

• Electric braking system actuators are starting to
  emerge in the marketplace, such as are set for
  the upcoming Boeing 787 (which will have electric
  brakes)
• More work needs to be done on this systems
  regarding reliability, design capability,
  modeling, efficiency and cost
• It is also not well understood how much benefit
  will be gained by converting all these systems to
  electrical at this time. As has been borne out
  with other mechanical systems, they are piecewise
  converted to electrical, as design tools,
  software methods and other control aspects are
  worked out and made efficient, cheap and reliable.