Brake-by-Wire Correction Restriction for Load-Fluid Loss Perception
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Solution Overview
Problem
In brake-by-wire systems, vehicle operators cannot perceive changes in the load versus fluid loss property, leading to delayed detection of abnormal conditions, which can cause unfamiliar or unpleasant responses during braking.
Innovation Solution
A vehicle brake system that includes a fluid pressure generating unit, friction braking unit, actual brake fluid pressure detecting unit, brake pedal operation amount detecting unit, target operation amount setting unit, correcting unit, and correction restricting unit, which allows the operator to perceive changes in braking force by adjusting the target operation amount based on actual brake fluid pressure deviations, within predetermined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control unit performs target brake fluid pressure correction by adding the deviation between reference brake fluid pressure and detected actual brake fluid pressure to the target brake fluid pressure, then the actual brake fluid pressure tracks the target brake fluid pressure accurately, but the vehicle operator cannot perceive changes in the load versus fluid loss property
Solution Approach 1:
The invention applies partial correction by introducing a correction restriction that limits the magnitude of pressure correction. Instead of fully compensating for deviations (excessive action), the system applies only a portion of the required correction, allowing some deviation to remain. This residual deviation enables the operator to perceive changes in load versus fluid loss property while still maintaining acceptable tracking accuracy through the corrected target brake fluid pressure.
2Productivity
If the system maintains exact tracking of brake fluid pressure to target pressure through correction, then braking performance is optimized, but the operator is unable to identify abnormal conditions until failure detecting region is reached
Solution Approach 1:
The invention introduces a correction restriction as an intermediary element between the pressure deviation detection and the target pressure adjustment. This intermediary component selectively transmits information about pressure deviations to the operator while still maintaining corrected target pressure for optimal braking performance. The correction restriction acts as a mediator that balances the conflicting requirements of braking efficiency and abnormal condition detection.
3Reliability
If the normal control process is terminated when load versus fluid loss property reaches failure detecting region, then system safety is protected, but the vehicle response changes significantly causing unfamiliar or unpleasant impression to the operator
Solution Approach 1:
The invention applies beforehand cushioning by gradually reducing the correction amount as the system approaches the failure detecting region, rather than abruptly terminating the control process. This progressive reduction cushions the transition, preventing sudden changes in vehicle response that would cause unfamiliar or unpleasant impressions to the operator. The correction restriction ensures that safety protection is maintained while preserving braking feel consistency throughout the operation range.
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
Enables the vehicle operator to perceive changes in the load versus fluid loss property through changes in braking force, maintaining a familiar braking feel and preventing uncomfortable responses.
Implementation Method 1
a motor actuated cylinder 13 power actuated according to a given target operation amount (St) to generate a brake fluid pressure
Implementation Method 2
a friction braking means (2a, 2b, 3a, 4a) configured to be actuated by the brake fluid pressure generated by the fluid pressure generating means
Data Source
AI summary
Upon occurrence of a change in the load versus fluid loss property, the braking force for the given brake pedal operation amount is changed so that the vehicle operator is enabled to perceive the change in the load versus fluid loss property. In a vehicle brake system comprising a motor actuated cylinder, wheel cylinders, a stroke sensor for detecting a brake pedal operation amount, a target value setting circuit for setting a target stoke of the motor actuated cylinder, and a fluid pressure compensating circuit for correcting the target stoke upon detection of a deviation between a brake fluid pressure reference value corresponding to the brake pedal operation amount and an actual brake fluid pressure in a direction to reduce the deviation, a stroke limiting circuit restricts a compensation value produced by the fluid pressure compensation circuit according to the brake pedal operation amount.