Brake Pedal Reaction Force Control for Vehicle Deceleration
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Solution Overview
Problem
In brake-by-wire systems, the separation of operating characteristics between the vehicle operator and the vehicle leads to deviations in expected operation and actual vehicle behavior, particularly due to the mechanical play in the brake mechanism, causing an inconsistent feel and delayed perception of deceleration.
Innovation Solution
A braking control device with an electronic control unit that sets a braking rigidity characteristic based on the ratio of reaction force to brake pedal stroke and vehicle deceleration, allowing for correlated control of reaction force and braking force, thereby aligning operator perception with vehicle behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the operational reaction force is set higher to secure rigid feel, then the braking force decreases, but this causes deviation between operator expectation and actual vehicle behavior
Solution Approach 1:
The patent applies dynamics by making the reaction force characteristic changeable based on vehicle speed. The ECU switches between a first reaction force characteristic (at low speed) and a second reaction force characteristic (at high speed), allowing the system to adapt its rigidity feel dynamically rather than maintaining a fixed characteristic. This resolves the contradiction by providing rigid feel when needed (high speed) while maintaining accurate operator-vehicle correspondence when precision is critical (low speed).
Solution Approach 2:
The patent changes the parameter of reaction force characteristic based on vehicle speed. By detecting vehicle speed and selecting different reaction force characteristics accordingly, the system adjusts the relationship between brake pedal stroke and reaction force. This parameter change allows the system to optimize both rigid feel and operator-vehicle correspondence under different operating conditions.
2Ease of operation
If the brake mechanism mechanical play is eliminated, then the stepping operation feel improves, but the step-on stroke becomes indistinguishable from actual stepping stroke
Solution Approach 1:
The patent applies local quality by providing different reaction force characteristics for different braking scenarios. Instead of a uniform reaction force characteristic, the system provides a first characteristic during step-on stroke (with mechanical play elimination) and a second characteristic during actual stepping stroke. This local differentiation allows the system to improve stepping operation feel in the actual stepping phase while maintaining the ability to detect and handle step-on stroke separately through brake fluid pressure detection.
Data Source
AI summary
A braking control device for a vehicle is provided, which includes an operating amount detecting part configured to detect an operating amount of a brake pedal, a reaction-force giving part configured to generate a reaction force of the brake pedal, a braking-force generating part configured to generate a braking force for wheels according to the brake pedal operating amount, and an electronic control unit (ECU) electrically connected with them. The ECU includes a processor configured to control the giving part and generating part, and set a braking rigidity characteristic based on a braking rigidity that is a ratio of the reaction force to the operating amount, and a vehicle deceleration. The ECU sets a braking rigidity value so that the braking rigidity value increases as the vehicle deceleration becomes larger. The ECU controls the reaction-force giving part based on the braking rigidity value.