Adaptive Cruise Control Brake Fluid Pre-filling for Delay Reduction
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Solution Overview
Problem
Adaptive cruise control (ACC) systems face challenges in braking response due to initial delays and noise/vibration/harshness issues when transitioning from non-braking to braking, leading to jerky movements and increased noise, especially in vehicles with large brake fluid volumes.
Innovation Solution
A method that determines the needed braking force, fills the brake system with fluid at a predetermined rate to reduce pump noise, sets an initial delay for brake pad contact, and adjusts the delay to zero once the actual braking force matches the requested force, allowing for smoother and quicker braking responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the brake system is filled with brake fluid rapidly to reduce initial delay, then the braking response speed is improved, but pump noise increases
Solution Approach 1:
The brake system is pre-filled with brake fluid before the actual braking maneuver is initiated. This preliminary action ensures that when braking is required, the fluid is already in position, eliminating the initial delay without requiring rapid pumping during the actual brake application.
Solution Approach 2:
The pump operates in periodic cycles: filling the brake system with fluid at a controlled rate during non-braking periods, then maintaining pressure during braking. This periodic operation allows the system to prepare in advance without continuous high-speed pumping that would generate noise during actual braking.
2Speed
If the ACC brake deceleration request catches up quickly, then the response time is improved, but the jerk executed by the ESP system becomes greater than ACC demands
Solution Approach 1:
The system dynamically adjusts the braking force application rate based on the ACC's deceleration request. By controlling the rate at which brake pads are applied to discs, the system achieves rapid response while limiting the jerk to match ACC demands, preventing excessive force application that would be felt by the driver.
3Ease of operation
If a constant delay is maintained throughout the control, then the jerk requested by the ACC is executed as requested, but the system reacts as late as the initial delay and is susceptible to oscillations
Solution Approach 1:
The brake system performs preliminary fluid filling and pressure building before actual braking is required. This advance preparation eliminates the need for constant delay compensation, allowing the system to respond immediately when braking is requested without oscillations.
Solution Approach 2:
The system continuously monitors brake fluid pressure and braking force application, adjusting the pump operation and brake application rate in real-time. This feedback mechanism ensures that the brake system responds smoothly without oscillations while maintaining minimal delay.
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 approach reduces initial delays and jerkiness, providing a more responsive and comfortable braking experience by minimizing startup noise and maintaining fluid in the system for rapid subsequent braking requests, suitable for various vehicle types including heavy vehicles with large brake fluid volumes.
Implementation Method 1
filling the brake system with brake fluid at a predetermined rate to reduce pump noise
Implementation Method 2
applying a brake pad to a brake disc at the amount of braking force needed
Data Source
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AI summary
A method of controlling braking in an adaptive cruise control (ACC) of a vehicle. The method includes determining that braking is needed, including determining an amount of braking force needed, providing an indication to the brake system that braking is needed, filling the brake system with brake fluid at a predetermined rate to reduce pump noise, setting a delay equal to the amount of time needed to fill the brake system with fluid, applying a brake pad to a brake disc at the amount of braking force needed after waiting the delay, comparing the amount of braking force needed to the amount of braking force actually occurring, and reducing the delay to zero when the amount of braking force needed is less than or equal to the amount of braking force actually occurring.