Pre-Limit Vehicle Speed Calculation With Deceleration Constraints
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Solution Overview
Problem
Existing methods for automated driving systems fail to accurately determine the ideal speed for a motor vehicle approaching a speed limit area, leading to unnecessary acceleration or braking, which affects fuel efficiency and safety.
Innovation Solution
A method calculates the maximum end speed of a motor vehicle before entering a speed limit area by estimating time to the limit, determining a speed increase using an algorithm or characteristic map, and adjusting for deceleration limits, thereby ensuring smooth transition to the speed limit value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the vehicle accelerates to maximum permitted speed before a speed limit area, then the travel time is reduced, but unnecessary braking occurs when the current speed is already sufficient
Solution Approach 1:
The system performs preliminary calculation of the ideal target speed before the vehicle reaches the speed limit area. By computing the optimal speed profile in advance based on distance to the speed limit area, current speed, and deceleration characteristics, the vehicle can accelerate appropriately without overshooting the speed limit, thus avoiding unnecessary braking and energy waste.
Solution Approach 2:
The system dynamically adjusts the target speed parameter based on changing conditions such as distance to the speed limit area, current vehicle speed, and deceleration rate. By continuously updating the ideal target speed as these parameters change, the system optimizes the balance between acceleration and deceleration to minimize both time loss and energy consumption.
2Measurement precision
If complex algorithms are used to calculate ideal target speed, then accuracy is improved, but computing power requirements increase
Solution Approach 1:
The system uses characteristic maps that pre-store ideal speed increase values for various distance and speed conditions. Instead of performing complex real-time calculations, the control unit simply looks up the appropriate value from the pre-computed characteristic map based on current conditions, achieving high accuracy with minimal computing power.
Solution Approach 2:
The characteristic maps are pre-calculated and stored before the vehicle operates. All complex computational work is performed in advance during system setup or manufacturing, allowing the vehicle's control unit to quickly retrieve pre-computed optimal speed values during actual operation without requiring significant computing resources.
3Loss of time
If high speed increase is applied before speed limit area, then time loss is reduced, but deceleration may exceed comfortable or safe limits
Solution Approach 1:
The system incorporates deceleration limit parameters into the speed calculation process. By adjusting the target speed based on maximum comfortable deceleration rates and the vehicle's deceleration characteristics, the system ensures that even when aggressive acceleration is used to minimize time loss, the subsequent deceleration will not exceed safe or comfortable limits for the occupants.
Data Source
AI summary
A method for determining a maximum end speed of a motor vehicle before the start of a speed limit area. The method includes determining a current motor vehicle speed, a speed limit value of an upcoming speed limit area, and a distance to the start of the speed limit area. A time is estimated to the speed limit area on the basis of the previously determined values. A speed increase with respect to the current motor vehicle speed is determined, dependent on the time to the speed limit area. A deceleration is estimated, so that based on the current motor vehicle speed, the speed increase, and the distance to the start of the speed limit area, the speed limit value is present at the start of the speed limit are. The determined speed increase is reduced if the estimated deceleration is greater than a deceleration limit value.