Following Distance Control Device Low Speed Stop Accuracy
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Solution Overview
Problem
Existing following distance control devices struggle to smoothly bring a vehicle to a stop in extremely low speed ranges due to wheel speed sensors failing to detect speed, leading to inaccurate stop determination and sudden braking, causing shocks and inability to maintain a smooth stop.
Innovation Solution
A following distance control device that includes a vehicle speed detecting device to determine zero speed, a stop determining device to accurately assess stop time by dividing real vehicle speed by requested acceleration, and a control system to manage requested accelerations to prevent sudden braking, ensuring smooth stops by determining the stop based on elapsed time and adjusting accelerations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wheel speed sensor is used to detect vehicle speed in extremely low speed range, then device complexity is reduced, but measurement precision deteriorates because the sensor cannot detect speed at 1 km/h or less
Solution Approach 1:
The patent introduces an intermediary calculation method that uses the relationship between following distance and relative speed to estimate actual vehicle speed when the wheel speed sensor reads zero. This intermediary approach bridges the gap between the sensor's limited capability and the need for accurate low-speed measurement.
Solution Approach 2:
The patent replaces direct mechanical speed sensing with a computational approach that derives speed information from following distance control parameters. This substitution allows the system to infer actual vehicle speed through calculation rather than direct measurement.
2Ease of operation
If stop determination is made based on wheel speed becoming zero, then ease of operation is improved, but reliability deteriorates because the vehicle may not have actually stopped yet
Solution Approach 1:
The patent implements feedback by continuously monitoring the relationship between following distance changes and relative speed to determine when the vehicle has truly stopped. This feedback mechanism ensures accurate stop detection despite the wheel speed sensor's limitations.
Solution Approach 2:
The patent performs preliminary calculations of expected stopping distance and time before actual stop determination. By comparing actual following distance changes against predicted values, the system can reliably determine stop completion in advance of traditional sensor-based methods.
3Productivity
If base requested acceleration is continued during elapsed time after wheel speed becomes zero, then productivity is maintained, but object-generated harmful factors increase due to sudden braking shocks
Solution Approach 1:
The patent applies preliminary anti-action by preemptively adjusting the base requested acceleration before the vehicle actually stops. By reducing acceleration commands in anticipation of stop completion, the system prevents the harmful shock that would otherwise occur when the stop-holding brake is applied.
Solution Approach 2:
The patent cushions against potential braking shocks by smoothly reducing the base requested acceleration as the vehicle approaches complete stop. This beforehand cushioning ensures a gentle transition to the stop-holding brake application, eliminating sudden shocks while maintaining control efficiency.
Data Source
AI summary
A following distance control device includes a vehicle speed detecting device that detects the vehicle speed VSPD of an own vehicle and outputs a vehicle speed equal to or less than a predetermined speed as zero, a following distance detecting device that detects a following distance between a preceding vehicle and the own vehicle, a first requested acceleration computing device that computes a requested acceleration GBASE from the vehicle speed and the following distance, and a stop determining device that determines the stop of the own vehicle, on the basis of a requested acceleration Greq_pre_0 kph at a time point when the output value of the vehicle speed detecting device becomes zero.