Electric Rail Brake Home Position Sensing for Consistent Braking
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Solution Overview
Problem
Existing electrically operated brake assemblies for rail vehicles face challenges in maintaining consistent braking behavior due to wear of friction members, leading to unpredictable idle distances and delayed deceleration.
Innovation Solution
An electrically operated brake assembly that includes a rotating member, friction members, a gear assembly, an electric motor, a force sensor, an angular position sensor, and a controller. The controller defines a home position by using pressure and pulse count signals to ensure consistent idle distance and reliable braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a stepper motor is driven at high speeds to engage brake shoes with a brake drum, then the braking response speed is improved, but the stepper motor may slip or stall before the friction members engage with the rotating member, leading to erroneous home position detection
Solution Approach 1:
The patent employs feedback from a force sensor to detect when the brake shoes actually engage with the brake drum by monitoring the contact force. This feedback mechanism allows the system to accurately determine the home position based on actual engagement conditions rather than relying solely on stepper motor position commands, thereby preventing erroneous detection caused by motor slipping or stalling at high speeds
Solution Approach 2:
The patent replaces the purely mechanical position-based home detection method (relying on stepper motor steps) with a sensor-based detection method using a force sensor. This substitution allows the system to detect actual mechanical engagement conditions directly, eliminating the reliability issues associated with high-speed stepper motor operation and position estimation
2Force
If the friction members are pressed against the rotating member with high force, then the braking effectiveness is improved, but the wear of friction material increases progressively, leading to extended idle distance and delayed deceleration
Solution Approach 1:
The patent implements dynamic adjustment of the idle distance between friction members and the rotating member based on detected wear conditions. The system automatically compensates for wear by adjusting the starting position of the friction members, ensuring that the optimal engagement characteristics are maintained throughout the service life of the brake lining, thereby preserving both braking effectiveness and controlling wear rates
3Duration of action of stationary object
If the idle distance between friction members and rotating member is increased to accommodate wear, then the service life of friction material is extended, but the delay before deceleration begins increases, reducing braking responsiveness
Solution Approach 1:
The patent dynamically adjusts the idle distance based on the actual wear condition of the brake lining. Rather than using a fixed conservative idle distance, the system continuously monitors engagement conditions and adjusts the friction member position to maintain optimal performance, thereby minimizing deceleration delay while accommodating wear over the service life of the brake lining
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a foreseeable and consistent braking behavior by accurately defining the home position, ensuring a predictable braking force application and reducing the risk of premature stepper motor slipping.
Implementation Method 1
a force sensor configured to generate a pressure signal indicating a magnitude of a contact force between the at least one friction member and the rotating member
Implementation Method 2
an angular position sensor configured to generate a pulse-count signal, where each pulse count corresponds to a particular angular movement of an output shaft of the electric motor
Implementation Method 3
an electric motor configured to cause the gear assembly to operate on the at least one friction member to move between the engaged and disengaged positions
Implementation Method 4
a gear assembly arranged to operate on the at least one friction member
Implementation Method 5
the contact between the friction material, i.e. the lining in the brake pads or shoes creates frictional contact with the rotating member, e.g. a disc or a drum, creates the desired amount of braking torque to slow down the rail vehicle
Data Source
Figure 1~2
Figure 3a~3b
Figure 5a~7b
AI summary
An electrically operated brake assembly (200) for a rail vehicle contains: a rotating member mechanically linked to a wheel axle of the rail vehicle, at least one friction member (221; 222) movable between an engaged position in which the at least one friction member (221; 222) contacts the rotating member, and a disengaged position in which the rotating member is freely rotatable without contacting the at least one friction member (221; 222), a gear assembly (220) arranged to operate mechanically on the at least one friction member (221; 222), an electric motor (230) controllable via a control signal (CS) and configured to cause the gear assembly (220) to operate on the at least one friction member 221; 222) to move between the engaged and disengaged positions, a force sensor (225) configured to produce a pressure signal (F) indicating a magnitude of a force at which the at least one friction member (221; 222) contacts the rotating member, an angular position sensor (237) configured to produce a pulse-count signal (PC) where each pulse count reflects a particular angular movement of an output shaft of the electric motor (230) and a controller (120) configured to obtain the pressure signal (F) and the pulse count signal (PC), and based thereon define a home position for the electric motor (230).