Autonomous Vehicle Braking Control During Hydraulic Failure
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Solution Overview
Problem
Autonomous vehicles face challenges in controlling braking during hydraulic system failures, such as total loss of pressure or slow leaks, as the fixed relationship between brake pedal position and braking power is disrupted, leading to reduced responsiveness and potential skidding.
Innovation Solution
The vehicle's computing devices detect hydraulic system failures and switch from a first braking control behavior to a second behavior, adjusting brake pedal position based on deceleration targets and wheel slip feedback to maintain safe deceleration without locking up wheels, regardless of the failure type or circuit affected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle uses a fixed relationship between brake pedal position and deceleration control, then the braking system operates normally under healthy conditions, but the braking responsiveness and control accuracy deteriorate when hydraulic system failure occurs
Solution Approach 1:
The patent implements dynamic switching between two braking control behaviors based on the detected hydraulic system state. When hydraulic failure is detected, the system transitions from a fixed pedal-position-to-deceleration relationship to a dynamic control mode that actively adjusts brake pedal position based on target deceleration requirements and actual vehicle response, thereby maintaining braking effectiveness despite hydraulic pressure loss
Solution Approach 2:
The system continuously monitors actual deceleration and compares it with target deceleration, using this feedback to adjust the brake pedal position in real-time. This closed-loop feedback mechanism compensates for the disrupted pedal-deceleration relationship caused by hydraulic failure, allowing the autonomous vehicle to maintain precise braking control adaptability
2Force
If the vehicle increases brake pedal movement to compensate for hydraulic pressure loss, then braking force can be restored, but wheel skidding and loss of control may occur
Solution Approach 1:
The system uses feedback from actual deceleration measurements to modulate brake pedal position adjustments. By continuously comparing target deceleration with actual deceleration and adjusting pedal position accordingly, the system applies just enough braking force to compensate for hydraulic loss without exceeding the threshold that would cause wheel lockup or skidding
Solution Approach 2:
The system dynamically changes the brake pedal position parameter based on detected hydraulic failure conditions and actual vehicle deceleration response. Rather than applying a fixed compensation amount, the pedal position is adjusted as a variable parameter that adapts to the specific failure severity and vehicle state, preventing excessive braking force that would cause skidding
3Device complexity
If the autonomous vehicle uses standard braking control behavior, then the braking system is simple to control, but the system cannot adapt to hydraulic failures and loses braking effectiveness
Solution Approach 1:
The patent implements a dynamic braking control system that automatically switches between a first braking control behavior (for normal operation) and a second braking control behavior (for hydraulic failure conditions). This dynamic adaptation allows the system to maintain simplicity during normal operation while gaining failure adaptability when needed, without requiring complex manual intervention or system redesign
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
This approach allows autonomous vehicles to safely decelerate and prevent skidding even in situations where the brake pedal position-deceleration relationship is variable, without needing to identify the specific failure, ensuring stable operation during hydraulic system failures.
Implementation Method 1
a typical vehicle may include a split hydraulic brake system that includes multiple hydraulic circuits... Once the vehicle's brake pedal is depressed, this cause a push rod 40 to force a plunger 42 towards a floating piston 38 which increases the pressure in the first chamber 20 and the second chamber 22
Implementation Method 2
Pressure in the two chambers 20, 22 is equalized through the floating piston 38... causing the floating piston to force the seal 34 towards the end wall 46... thereby slowing the vehicle down
Data Source
AI summary
The disclosure relates to controlling braking behaviors a vehicle in an autonomous driving mode in the event of a hydraulic system failure. For instance, the vehicle may be controlled in the autonomous driving mode according to a first braking control behavior based on a first relationship between position of a brake pedal of the vehicle and amount of deceleration for the vehicle. While controlling the vehicle, a failure of a hydraulic system may be determined. Based on the determination, the vehicle may be controlled in the autonomous driving mode according to a second braking control behavior by moving the brake pedal until the vehicle reaches a deceleration target defined by the second braking control behavior.