Autonomous Vehicle Brake Pressure Control for Faster Hydraulic Response
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Solution Overview
Problem
Conventional brake systems for autonomous vehicles experience hydraulic response delays due to the orifice effect caused by additional valves in redundancy braking systems, leading to reduced PWM duty and voltage output, which impairs response performance, especially in the early stages of braking.
Innovation Solution
A brake system that includes a brake demand detecting unit, an electronic control unit with a pressure controller and a motor position controller to manage internal pressure and motor position, and a current controller to control motor current, improving hydraulic response performance by securing responsiveness through position control and accuracy through pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional valves are added to the redundancy braking system, then braking safety and redundancy are improved, but hydraulic response delay occurs due to orifice effect
Solution Approach 1:
The system pre-charges the master cylinder to operate at a higher initial pressure state before braking is applied. This preliminary pressurization ensures that when braking demand occurs, the hydraulic fluid is already under pressure, enabling faster response time through the valve assembly without sacrificing the safety benefits of the redundancy braking system.
2Speed
If circuit pressure is set higher than demand pressure to improve hydraulic response, then response performance is improved, but PWM duty is reduced and voltage output decreases
Solution Approach 1:
The master cylinder is pre-charged to a higher pressure state before braking demand occurs. This preliminary action stores hydraulic energy in advance, allowing the system to respond quickly to braking commands without requiring excessive voltage output or PWM duty cycle during actual braking operation.
Solution Approach 2:
The system dynamically adjusts the initial pressure parameter of the master cylinder to be higher than the demand pressure. This parameter change enables faster hydraulic response while optimizing the electrical energy consumption by reducing the required PWM duty cycle and voltage output during braking activation.
3Device complexity
If conventional pressure control is used, then system simplicity is maintained, but response performance delay occurs in early stage of braking
Solution Approach 1:
The master cylinder is pre-filled and pre-pressurized with hydraulic fluid before braking is applied. This preliminary preparation ensures that when the driver applies the brake pedal, the hydraulic system can respond immediately without the delay associated with pressure build-up, while maintaining the simplicity of the conventional pressure control architecture.
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 enhances hydraulic response performance by maintaining higher circuit pressure, reducing delays in wheel pressure formation, and ensuring precise pressure control throughout the braking process, thereby improving the overall responsiveness and demand performance of the brake system.
Implementation Method 1
the internal pressure of the master cylinder is controlled by generating an electrical signal for a first demand current
Implementation Method 2
a motor position controller configured to control a position of a motor by generating an electrical signal for a second demand current
Implementation Method 3
a pressure detecting unit configured to sense the internal pressure of the master cylinder
Data Source
AI summary
In accordance with some embodiments, the present disclosure provides A brake system for braking a vehicle using one or both of a main braking system and a redundancy braking system, the brake system comprising: a brake demand detecting unit configured to detect a driver's brake demand; an electronic control unit comprising: a pressure controller configured to control a pressure inside a master cylinder in response to a value detected by the brake demand detecting unit, wherein the internal pressure of the master cylinder is controlled by generating an electrical signal for a first demand current; a motor position controller configured to control a position of a motor by generating an electrical signal for a second demand current; and a current controller configured to control the current of the motor in response to an electrical signal received from one of the motor position controller and the pressure controller; a position detecting unit configured to detect a position of a rotor of the motor; and a pressure detecting unit configured to sense the internal pressure of the master cylinder.