Vehicle Rolling Distance Detection Using Interrupt Counting
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Solution Overview
Problem
Current vehicle rolling distance detection systems are too sensitive, leading to frequent pump or active booster activations that generate noticeable noise, vibration, and harshness (NVH) in vehicles equipped with Electronic Brake Systems (EBS) and Automatic Vehicle Hold (AVH) or Full Speed Range Adaptive (FSRA) cruise control.
Innovation Solution
A system utilizing a tone wheel with encoding members and Hall effect sensors to detect wheel rotation, counting interrupts to determine when to supply brake pressure and return the vehicle to standstill, with a microprocessor-controlled Electronic Brake System that adjusts interrupts based on rolling distance and hydraulic brake pressure build time to minimize unnecessary activations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rolling distance detection system uses a sensitive detection threshold to accurately detect vehicle rolling, then the detection precision is improved, but the pump activation frequency increases causing noise and vibration
Solution Approach 1:
The system changes the detection parameter from a simple speed threshold to a cumulative interrupt count threshold. By counting the number of tone wheel encoding member passages (interrupts) and comparing against a maximum allowed value, the system achieves precise rolling distance detection while avoiding over-sensitive responses to minor wheel rotations, thereby reducing unnecessary pump activations and associated noise.
2Reliability
If the pump is activated frequently to ensure the vehicle returns to standstill, then the reliability of vehicle hold function is improved, but the noise and vibration increase
Solution Approach 1:
The system implements feedback by continuously monitoring wheel rotation through the speed sensor and tone wheel, counting interrupts, and using this information to determine when to activate the brake system. The control unit receives feedback from the rolling detection and only activates the pump when the interrupt count exceeds the maximum allowed value, ensuring reliable vehicle hold while minimizing unnecessary activations that cause noise and vibration.
Solution Approach 2:
The system uses partial action by setting a maximum allowed interrupt count that is less than the total number of encoding members on the tone wheel. This allows the system to detect rolling distance without requiring complete rotation detection, enabling timely brake activation while avoiding excessive pump operations that would generate noise and vibration.
3Measurement precision
If the detection system counts all encoding member passages to determine rolling distance, then the measurement precision is improved, but the system complexity increases
Solution Approach 1:
The system applies partial action by counting only a maximum allowed number of interrupts rather than tracking all encoding member passages. This approach maintains sufficient measurement precision for determining when the vehicle has rolled far enough to require brake activation, while simplifying the control logic and reducing computational complexity compared to tracking complete rotation cycles or using more complex sensor systems.
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
This solution reduces unnecessary brake system activations, thereby minimizing noise, vibration, and harshness (NVH) in vehicles by accurately determining the rolling distance and timing of brake pressure application, ensuring the vehicle is brought to a standstill before reaching the required distance.
Implementation Method 1
Each sensor is a Hall effect sensor
Data Source
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Figure 3~4
AI summary
A vehicle includes a tone wheel having a plurality of encoding members spaced substantially evenly about a periphery thereof. Each tone wheel is rotates with an associated wheel. A fixed speed sensor is mounted adjacent to each tone wheel. The vehicle includes a brake system. A method determines a travel distance between adjacent encoding members. A required rolling distance of a vehicle from standstill is established. Maximum allowed interrupts per wheel is established, with an interrupt defined as each instance an encoding member passes an associated speed sensor. It is determined whether the vehicle is actually rolling from standstill. Once the vehicle is actually rolling, a number of interrupts is counted at each wheel. When the maximum allowed interrupts is counted at each wheel, the brake system is supplied with pressure increase to return the vehicle to, and hold the vehicle at, standstill prior to reaching the required rolling distance.