Vehicle Braking Force Control for Smooth Stop Pitch Suppression
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Solution Overview
Problem
Conventional braking control devices cause discomfort to occupants due to pitching behavior during vehicle stopping, as they result in a large deceleration feeling and potential oil striking sounds from rapid hydraulic pressure changes.
Innovation Solution
A braking control device that executes reducing and increasing control of braking force based on calculated differences in traveling distances to minimize deceleration sensation, setting the increase amount of braking force to prevent vehicle delay and improve comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If deceleration is increased to Gmax before smoothing control to prevent stopping delay, then stopping time is reduced, but deceleration feeling becomes large and comfort deteriorates
Solution Approach 1:
The control device increases deceleration to Gmax before the smoothing control is executed. This preliminary increase in deceleration ensures that the vehicle can stop on time without delay, while the subsequent smoothing control mitigates the harsh deceleration feeling for comfort.
Solution Approach 2:
The braking control is executed in two distinct phases: first increasing deceleration to Gmax, then reducing it during smoothing control. This periodic variation in deceleration level allows the system to achieve both timely stopping and comfortable deceleration experience.
2Object-affected harmful factors
If deceleration is increased and then reduced to smooth braking, then comfort is improved, but change gradient of braking force becomes large causing oil striking sound
Solution Approach 1:
The control device changes the deceleration parameter dynamically during braking. By increasing deceleration to Gmax and then reducing it during smoothing control, the system optimizes both comfort and prevents oil striking sounds through controlled parameter variation.
3Object-affected harmful factors
If reducing control is executed before stopping, then pitching behavior is suppressed, but traveling distance increases due to braking force reduction
Solution Approach 1:
The increasing control is executed before the reducing control to preliminarily increase the braking force. This ensures that when reducing control is later executed to suppress pitching behavior, the vehicle does not experience excessive traveling distance increase because the braking force was already elevated.
Solution Approach 2:
The control device calculates the difference distance between two scenarios (with and without reducing control) and uses this feedback to determine the increase amount in increasing control. This feedback mechanism optimizes the braking force adjustment to minimize traveling distance increase while still suppressing pitching behavior.
Data Source
AI summary
A braking control device, when stopping a vehicle in a state where a braking force is being applied to the vehicle, executes a reducing control of reducing the braking force corresponding to a braking request before the vehicle stops and executes an increasing control of increasing the braking force corresponding to the braking request before the reducing control in order to suppress vehicle pitching behavior generated when the braking force is applied to the vehicle. The control device sets braking force increase amount in the increasing control based on a difference distance that is a difference between a first distance correlated with a vehicle traveling distance from a reduction start timing when the reducing control is executed until the stopping of the vehicle and a second distance correlated with a vehicle traveling distance from the reduction start timing when the reducing control is not executed until the stopping of the vehicle.