Vehicle Braking Force Control for Hill Start Assist
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Solution Overview
Problem
Existing braking force control systems for vehicles face challenges in hill start assist control, particularly when transitioning from braking force holding to reduction, as they struggle to balance preventing vehicle slippage while avoiding driver discomfort due to excessive braking force during driver-initiated starts, and ensuring adequate braking force during automated driving support control.
Innovation Solution
A braking force control apparatus that differentiates between driver-initiated and automated driving support requests by adjusting the braking force reduction strategy, applying a larger braking force during automated driving support to prevent slippage and maintaining a sufficient braking force during driver-initiated starts to avoid discomfort, using a control unit that calculates and applies a target braking force based on estimated required driving forces and lowering forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If braking force is reduced promptly to avoid driver discomfort during driver-initiated starts, then driver comfort is improved, but vehicle slippage risk increases during automated driving support control
Solution Approach 1:
The patent segments the braking force reduction control into two distinct modes: a first control pattern for driver-initiated starts and a second control pattern for automated driving support control. The control unit identifies which mode is active and applies the appropriate reduction strategy, allowing optimized performance for each scenario without compromise.
Solution Approach 2:
The patent implements dynamic adjustment of braking force reduction characteristics based on the operating mode. The control unit varies the reduction rate and timing of braking force release according to whether the system is in driver-initiated or automated driving support mode, enabling adaptive optimization of both comfort and safety.
2Reliability
If braking force decreases slowly to prevent vehicle slippage during automated driving support control, then vehicle stability is improved, but driver feels sense of getting stuck during driver-initiated starts
Solution Approach 1:
The patent divides the braking force control into separate patterns for different operating modes. The first pattern enables faster braking force reduction for driver-initiated starts, while the second pattern maintains more conservative reduction for automated driving support, eliminating the need to compromise either scenario.
Solution Approach 2:
The patent changes the control parameters (braking force reduction rate, timing, and magnitude) based on the detected operating mode. By adjusting these parameters dynamically, the system optimizes vehicle stability for automated control while maintaining driver comfort for manual operation.
3Speed
If braking force is reduced quickly when actual braking force is lower than target due to system degradation, then response time is improved, but vehicle slippage risk increases
Solution Approach 1:
The patent incorporates feedback mechanisms where the control unit continuously monitors actual braking force output and compares it with target values. Based on this feedback and the detected operating mode, the control unit adjusts the braking force reduction strategy to maintain safety margins while achieving appropriate response characteristics.
Data Source
AI summary
A braking force control apparatus for a vehicle has a control unit that executes a braking force reduction control that controls a braking device such that a braking force is gradually reduced when it is determined that a drive request for driving the vehicle is generated during execution of the braking force holding control for controlling the braking device to hold a braking force applied to the vehicle when the vehicle stops in the uphill direction on a slope. The control unit controls the braking device such that the braking force during execution of the braking force reduction control is larger when the drive request is generated by the driving support control than when the drive request is generated by the driver's driving operation.