Vehicle Brake Hold Control for Low-Gradient Roll Prevention
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Solution Overview
Problem
Electric vehicles without a creep function may roll excessively on flat slopes, as drivers rely solely on the accelerator pedal, leading to imperceptible movement and potential accidents.
Innovation Solution
A vehicle controller that automatically applies the brakes when the vehicle is stationary on a slope with a small gradient, using measured speed and time-based thresholds to determine when to engage the brakes, without the need for additional sensors like inertial measurement units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If no creep torque is provided in electric vehicles, then the driver can modulate vehicle speed using only the accelerator pedal, but the vehicle may start to roll excessively on flat slopes after a small period of time
Solution Approach 1:
The brake system automatically applies itself to hold the vehicle stationary on slopes without driver intervention. The controller monitors vehicle speed and gradient conditions, and autonomously activates the brake when the vehicle is stationary on a slope below the threshold gradient, making the system self-regulating and eliminating the need for creep torque.
Solution Approach 2:
The controller continuously receives feedback about vehicle speed from speed sensors and gradient information, comparing these against threshold values. When the vehicle speed is below the threshold speed and the gradient is below the threshold gradient, the controller activates the brake. This closed-loop feedback mechanism ensures the brake is applied only when necessary, maintaining stability without interfering with normal driving operations.
2Reliability
If the brake is automatically applied to hold the vehicle stationary on slopes, then excessive rolling is prevented, but the system complexity increases
Solution Approach 1:
The existing brake system and controller are utilized for multiple functions: normal braking, creep function operation, and automatic slope holding. By making the brake system multi-functional and using the existing controller to manage slope holding logic, no additional dedicated components are required, thereby limiting the increase in system complexity while achieving improved reliability.
Solution Approach 2:
The controller acts as an intermediary that receives inputs from existing sensors (speed sensors and gradient information) and activates the brake system when necessary. This intermediary approach allows the system to integrate slope holding functionality using existing components, avoiding the need for additional sensors or complex mechanical systems while still achieving the desired stability.
3Measurement precision
If additional sensors like inertial measurement units are used to detect slope, then gradient detection accuracy is improved, but the cost and device complexity increase
Solution Approach 1:
The system utilizes existing vehicle sensors and available data (speed sensors and gradient information from the vehicle's existing sensor suite) to determine when the brake should be applied. By making use of already-available information and existing sensor infrastructure, the system achieves adequate gradient detection without requiring additional expensive sensors like inertial measurement units, thereby avoiding increased complexity and cost.
Solution Approach 2:
The controller changes the parameter being monitored from requiring precise absolute gradient measurement to detecting relative conditions (whether the gradient is below a threshold and the vehicle is stationary). This parameter change allows the system to use less precise but simpler existing sensors rather than requiring high-precision inertial measurement units, achieving the necessary functional accuracy without the complexity of additional sensors.
Data Source
AI summary
A controller for a vehicle, a system, a vehicle, a method, a computer program and a non-transitory computer-readable storage medium are disclosed. The controller is configured to receive an indication of a measured speed of the vehicle, and determine whether a gradient on which the vehicle is located is below a threshold gradient. The controller is also configured to provide an output signal to cause a brake of the vehicle to be automatically applied to hold the vehicle stationary, in dependence on: the received indication of the measured speed of the vehicle being below a threshold speed; and the determination that the gradient is below the threshold gradient.