Predictive Downhill Speed Control Using Gear Preselection
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Solution Overview
Problem
Existing vehicle speed control systems face challenges in managing fuel economy and brake wear when traveling along hilled routes, particularly due to excessive use of foundation brakes and overheating.
Innovation Solution
A predictive dynamic speed control system that adjusts vehicle speed and transmission gear before and during downhill segments using an electronic control system, incorporating powertrain retarders and foundation brakes to maintain speed limits and optimize fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If foundation brakes are used to control vehicle speed during downhill segments, then vehicle speed can be maintained within limits, but brake wear increases and overheating occurs
Solution Approach 1:
The control system performs preliminary speed reduction before the downhill segment begins, using the prime mover and transmission to lower vehicle speed in advance. This prevents excessive speed accumulation that would require intensive brake application during the downhill, thereby reducing brake wear and overheating while still maintaining speed limits.
Solution Approach 2:
The system introduces powertrain retarders as an intermediary mechanism between the vehicle's kinetic energy and the foundation brakes. These retarders (including engine braking and transmission-based retardation) absorb excess energy during downhill segments, reducing the burden on foundation brakes and preventing overheating while maintaining effective speed control.
2Use of energy by moving object
If vehicle speed is reduced before downhill segments to improve fuel economy, then fuel consumption decreases, but travel time increases
Solution Approach 1:
The system dynamically adjusts the pre-downhill speed reduction strategy based on real-time conditions including downhill grade, distance to downhill segment, current vehicle speed, and road conditions. This optimized dynamic control achieves fuel economy benefits while minimizing unnecessary speed reduction that would extend travel time, adapting the speed profile to each specific situation.
Solution Approach 2:
The control system modifies multiple parameters including target speed, gear selection, and retarding force application based on the specific characteristics of the upcoming downhill segment. By changing these parameters optimally, the system achieves fuel economy through reduced braking energy recovery while maintaining reasonable travel times through intelligent speed management.
3Reliability
If aggressive speed control is applied to minimize brake usage, then brake wear is reduced, but vehicle speed may fall below optimal levels
Solution Approach 1:
The control system continuously monitors vehicle speed, acceleration, downhill grade, and brake temperature, using this feedback to adjust retarding force application in real-time. This feedback control ensures that speed reduction is applied minimally and only when necessary to protect the brakes, preventing excessive speed reduction that would compromise vehicle performance and travel time.
Data Source
AI summary
A vehicle system includes a powertrain with a prime mover, a transmission with a number of gears, and foundation brakes. The vehicle system includes an electronic control system configured to determine, prior to reaching a downhill route segment, a pre-downhill target vehicle speed, a pre-downhill target transmission gear for the vehicle, and a downhill vehicle speed limit, control the vehicle to achieve the pre-downhill target vehicle speed and the pre-downhill target transmission gear for the vehicle prior to or upon reaching the downhill route segment, and control the vehicle during the downhill route segment not to exceed the downhill vehicle speed limit.