Brake System Load Compensation via Deceleration Feedback
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Solution Overview
Problem
Existing brake systems cause strange feelings during braking due to varying load conditions, as they increase the stroke amount of the output rod, leading to decreased vehicle deceleration and inconsistent brake hydraulic pressure, which affects the driver's experience.
Innovation Solution
A brake system that adjusts brake hydraulic pressure based on estimated deceleration, using a deceleration estimator and solenoid valves to manage brake fluid pulsation and simulate a consistent braking experience, eliminating the need for a load detection sensor and optimizing brake control according to actual deceleration, thereby maintaining consistent braking feel across different load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the stroke amount of the output rod is increased to assist braking force, then the braking assistance is improved, but the stroke amount of the input rod increases causing strange feeling to the driver
Solution Approach 1:
The master cylinder is introduced as an intermediary device between the brake booster output rod and the brake calipers. The master cylinder converts the longitudinal movement of the output rod into hydraulic pressure, which then acts on the brake calipers. This mediation allows braking assistance to be provided without directly transmitting excessive stroke to the driver's input rod, thus resolving the contradiction between braking assistance and operation feeling.
2Force
If brake hydraulic pressure is increased to maintain deceleration under heavy load, then the braking performance is improved, but the brake operator transmission to the driver increases causing strange feeling
Solution Approach 1:
The mechanical connection between the output rod and brake calipers is replaced with a hydraulic system. The master cylinder generates hydraulic pressure based on the output rod's movement, and this hydraulic pressure is transmitted to the brake calipers. This substitution allows the system to generate the necessary braking force under heavy load without transmitting excessive mechanical force and strange feelings to the driver through the brake operator.
3Measurement precision
If a load detection sensor is used to detect carried load, then the braking control accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The system uses the existing brake pedal stroke sensor to detect the driver's braking input and combines this with vehicle deceleration data (from wheel speed sensors or other available sensors) to infer the effective braking force and estimate carried load. This self-service approach eliminates the need for separate load detection sensors, reducing device complexity and cost while maintaining sufficient braking control accuracy.
Solution Approach 2:
The system implements feedback control by monitoring vehicle deceleration and comparing it with the driver's brake pedal input. Based on this feedback, the control apparatus adjusts the brake hydraulic pressure to achieve the desired deceleration, effectively compensating for carried load without requiring direct load measurement. This feedback mechanism replaces complex load detection with simpler deceleration-based control.
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
The system effectively controls brake hydraulic pressure to match reference deceleration, reducing pulsation and ensuring a consistent braking experience without the need for additional sensors, thus suppressing changes in braking feel due to load variations and reducing costs by eliminating the requirement for a load detection sensor.
Implementation Method 1
the brake hydraulic pressure is increased by the electric actuator, the first solenoid valve is closed and the second solenoid valve is opened. Thus, pulsation of brake liquid transmitted from the slave cylinder apparatus to the master cylinder can be suppressed
Implementation Method 2
the hydraulic pressure generated from the master cylinder is absorbed by the stroke simulator through the second solenoid valve
Data Source
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AI summary
A brake system includes a master cylinder, a first solenoid valve, a stroke simulator, a slave cylinder apparatus, and a control apparatus. The master cylinder generates a brake hydraulic pressure in response to an operation on a brake operator. The first solenoid valve is provided between the master cylinder and a wheel brake. The stroke simulator is connected to the master cylinder through a second solenoid valve. The slave cylinder apparatus includes an electric actuator and a cylinder mechanism. The cylinder mechanism generates a brake hydraulic pressure. The control apparatus closes the first solenoid valve and opens the second solenoid valve when the brake hydraulic pressure is increased by the electric actuator. The control apparatus controls the electric actuator so that the larger a carried load on a vehicle is, the larger the brake hydraulic pressure is.