Brake System Pedal Simulator for Autonomous Handoff
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Solution Overview
Problem
Conventional vehicle braking systems face challenges in maintaining precise control, especially under adverse conditions, leading to wheel lock-up and loss of directional control, and struggle with smooth transitions between autonomous and driver-initiated braking, resulting in disconcerting deceleration changes.
Innovation Solution
A hydraulic braking system with an electronic control unit, isolation valves, and a plunger assembly that allows for dynamic pressure control and smooth transitions between autonomous and driver-initiated braking, using solenoid actuated valves and a pedal simulator to maintain consistent deceleration and pedal feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a driver applies excessive braking pressure under adverse conditions, then braking force is increased, but wheel lock-up occurs causing loss of directional control
Solution Approach 1:
The ABS system continuously monitors wheel rotational behavior and uses this feedback to selectively apply and relieve brake pressure, maintaining wheel speed within a selected slip range to prevent wheel lock-up while preserving directional control
Solution Approach 2:
The system dynamically adjusts brake pressure in real-time based on wheel speed feedback, transitioning between pressure apply, pressure dump, and pressure hold modes to maintain optimal slip levels without causing wheel lock-up
2Reliability
If ABS valves are used to separately control braking pressures on front and rear wheels, then optimum braking performance is achieved, but device complexity increases
Solution Approach 1:
The ABS valves are designed to perform multiple functions: they control braking pressure distribution between front and rear wheels for dynamic rear proportioning, and also provide traction control by applying pressure to slipping wheels during acceleration, reducing the need for separate dedicated control mechanisms
3Reliability
If valves are added to existing ABS systems to provide traction control, then wheel slippage is reduced during acceleration, but device complexity increases
Solution Approach 1:
The same ABS valves that control braking pressure distribution are used for traction control functions. The electronic control system activates these existing valves to apply pressure to slipping wheels during acceleration, eliminating the need for separate traction control valves and reducing overall system complexity
4Extent of automation
If autonomous braking is activated without driver pedal input, then vehicle deceleration is achieved, but smooth transition to driver-initiated braking is difficult
Solution Approach 1:
A pedal simulator is introduced as an intermediary mechanism that replicates the mechanical feel of brake pedal engagement. When autonomous braking is activated, the pedal simulator provides realistic pedal resistance and movement feedback to the driver, maintaining consistent pedal feel during transitions between autonomous and driver-initiated braking modes
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 ensures precise control and smooth transitions between autonomous and driver-initiated braking, maintaining consistent deceleration and eliminating disconcerting pedal feel changes, thereby enhancing vehicle stability and driver experience.
Implementation Method 1
Electronically controlled ABS valves, comprising apply valves and dump valves, are located between the master cylinder and the wheel brakes
Implementation Method 2
When the brake pedal is depressed, the master cylinder generates hydraulic forces in both brake circuits by pressurizing brake fluid
Implementation Method 3
wheel brakes in each circuit... actuate brake cylinders at the wheels to slow the vehicle
Data Source
AI summary
A method of controlling the fluid pressure at wheel brakes of a brake system, the method comprising: (a) providing a brake system capable of delivering fluid pressure to the wheel brakes during an autonomous braking event, and wherein the brake system includes a brake pedal and sensor for sensing a driver's braking intent when applying force to the brake pedal; (b) controlling the fluid pressure at the wheel brakes at a predetermined pressure during an autonomous braking event, wherein the sensor detects no depression of the brake pedal; (c) cancelling the autonomous braking event when the sensor detects depression of the brake pedal; and (d) subsequently to step (c), the brake system enters into a handoff procedure to maintain the predetermined pressure at the wheel brakes after the sensor senses the brake pedal being depressed when a requested pressure by the driver is less than the predetermined pressure.