Coast Stop Control for Automated Vehicles
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Solution Overview
Problem
Existing engine stop-start control systems in self-driving vehicles are inefficient due to repeated engine startups and shutdowns when following a preceding vehicle that accelerates and decelerates, leading to increased fuel consumption and reduced fuel efficiency.
Innovation Solution
A control method for self-driving vehicles that determines whether to execute a coast stop based on required driving force and predicts the behavior of preceding vehicles, prohibiting engine restart during predicted deceleration and preventing engine shutdown during predicted acceleration to maintain a predetermined intervehicular distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is automatically stopped during vehicle traveling to reduce fuel consumption, then fuel efficiency is improved, but the engine starts and stops repeatedly when the preceding vehicle accelerates and decelerates, which worsens fuel efficiency
Solution Approach 1:
The control device predicts the future behavior (acceleration or deceleration) of the preceding vehicle based on current situation data. This preliminary prediction allows the system to prepare and prohibit unnecessary engine restarts before they occur, preventing repeated engine operations that would waste fuel. The prediction mechanism acts in advance to avoid the contradiction between stopping the engine for fuel savings and restarting it due to preceding vehicle behavior changes.
2Length of moving object
If the engine is restarted when the intervehicular distance expands due to acceleration of the preceding vehicle, then the intervehicular distance is maintained, but the engine stops and starts repeatedly, reducing the effect of fuel consumption reduction
Solution Approach 1:
The system predicts whether the preceding vehicle will decelerate in the future based on current situation data. If deceleration is predicted, the engine restart is prohibited even if the intervehicular distance temporarily expands. This preliminary prediction prevents unnecessary engine restarts that would occur if the system only reacted to current distance changes, thereby maintaining fuel savings while still ensuring the engine restarts when actually needed.
Solution Approach 2:
The control device continuously monitors the intervehicular distance and compares it with the predetermined distance. When the distance expands, the system evaluates whether an engine restart is needed based on predicted preceding vehicle behavior. This feedback mechanism ensures the intervehicular distance is maintained within acceptable ranges while avoiding unnecessary engine operations that would increase fuel consumption.
3Length of moving object
If the engine operation is controlled solely based on relative traveling state to the preceding vehicle, then the intervehicular distance is maintained, but repeated acceleration and deceleration of the preceding vehicle causes repeated engine start and stop
Solution Approach 1:
The control device acquires situation data about the preceding vehicle and predicts its future behavior (acceleration or deceleration) before the actual behavior occurs. This prediction allows the system to proactively prohibit unnecessary engine restarts, preventing the cycle of repeated engine start-stop operations. By acting in advance based on predicted behavior rather than reacting to actual behavior, the system maintains intervehicular distance control while improving fuel efficiency.
Data Source
AI summary
A control method for a self-driving vehicle provided with an engine as a driving source, comprising: determining whether or not coast stop is executed in accordance with required driving force of the vehicle, the coast stop being for automatically stopping the engine during the vehicle traveling at speed not more than predetermined vehicle speed; setting the required driving force so that an intervehicular distance between the host vehicle and a preceding vehicle becomes closer to a predetermined distance under presence of the preceding vehicle in front of the host vehicle; predicting a behavior of the preceding vehicle from a situation in front of the preceding vehicle under presence of the preceding vehicle; and prohibiting release of the coast stop for the engine during an automatic stop when future deceleration of the preceding vehicle is predicted in response to an expansion of the intervehicular distance.