ACC Target Acceleration Mapping for Smooth Low-Speed Restart
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Solution Overview
Problem
In adaptive cruise control (ACC) systems, the torque required for acceleration from vehicle-stoppage or a speed close to vehicle-stoppage is greater than during normal traveling, leading to unsatisfactory responsiveness and inability to achieve smooth acceleration.
Innovation Solution
A driving assistance apparatus that includes an inter-vehicle-distance detection section, a relative-speed detection section, and a target-acceleration/deceleration-speed output section with two maps: a first map for normal speeds and a second map for vehicle-stoppage or near-stoppage speeds, which outputs a greater target acceleration speed when the vehicle is stopped or near stopped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single target acceleration speed map is used for all vehicle speeds, then the ACC system is simple to implement, but acceleration responsiveness from vehicle-stoppage or near-stoppage is unsatisfactory
Solution Approach 1:
The patent divides the target acceleration speed determination into two separate maps: a first map for vehicle speeds above a threshold and a second map for vehicle speeds at or below the threshold. This segmentation allows each map to be optimized for its specific speed range, with the second map providing greater target acceleration speeds for stoppage conditions, thereby resolving the contradiction between system simplicity and acceleration responsiveness.
2Speed
If a greater target acceleration speed is output from vehicle-stoppage, then acceleration responsiveness is improved, but the risk of collision with leading car increases due to insufficient inter-vehicle distance
Solution Approach 1:
The patent applies different target acceleration speed characteristics to different vehicle speed conditions through the use of two distinct maps. The second map is specifically designed for vehicle-stoppage or near-stoppage conditions and outputs greater target acceleration speeds, while the first map handles normal traveling conditions. This local differentiation ensures that high acceleration is applied only where needed (at low speeds) without compromising safety at higher speeds, thus resolving the contradiction between responsiveness and collision risk.
Data Source
AI summary
Provided is a driving assistance device that makes it possible to smoothly accelerate from a stop or from a speed close to a stop. A target acceleration/deceleration output unit of the driving assistance device has: a first map that stores first target accelerations which are associated with inter-vehicle distance and with relative speed; a second map that stores second target accelerations which are associated with inter-vehicle distance and with relative speed and which are greater than the first target accelerations with respect to inter-vehicle distance and relative speed; and a selection unit that selects, according to a vehicle speed, whether to use the output of the first map and/or whether to use the output of the second map.