Vehicle Speed Control Apparatus Rate Limiting
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Solution Overview
Problem
Existing vehicle speed control systems cause unexpected changes in vehicle speed when road speed limits change, leading to a disconcerting experience for drivers who expect constant speed while accelerating or decelerating.
Innovation Solution
A vehicle speed control apparatus that generates a speed command value based on the accelerator pedal's tread amount and adjusts vehicle speed to maintain a predetermined upper-limit speed, limiting the rate of change in vehicle speed when road speed limits change, ensuring a smoother transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the vehicle speed control system immediately updates the upper-limit speed when road speed limits change, then the vehicle speed control responds quickly to new speed limits, but the vehicle speed changes abruptly causing driver discomfort
Solution Approach 1:
The patent applies dynamics by making the rate of change of vehicle speed adjustable rather than fixed. The control system dynamically adapts the rate of change based on current driving conditions, allowing the vehicle speed to transition smoothly from the old upper-limit speed to the new upper-limit speed over a predetermined period, thereby reducing abrupt changes and driver discomfort while still responding to speed limit changes
Solution Approach 2:
The patent changes the parameter of rate of change of vehicle speed from a constant value to a time-varying parameter. By controlling the rate of change to decrease continuously until a predetermined timing after speed limit changes, the system transforms the abrupt speed change into a gradual transition, resolving the contradiction between quick response and driver comfort
2Adaptability or versatility
If the vehicle speed control system maintains constant speed according to accelerator pedal input, then the driver's speed control intent is respected, but the vehicle may exceed the updated speed limit after road speed limits change
Solution Approach 1:
The patent implements feedback by continuously monitoring both the accelerator pedal input (driver's speed control intent) and the updated speed limit information. The control system compares the desired speed based on pedal input with the current upper-limit speed and adjusts the vehicle speed accordingly, ensuring that the vehicle remains compliant with speed limits while still respecting the driver's acceleration or deceleration intentions
Solution Approach 2:
The system dynamically adjusts the vehicle speed by controlling the rate of change based on the relationship between the current speed and the updated upper-limit speed. When the speed limit is updated, the system gradually adjusts the speed rather than making abrupt changes, maintaining both adaptability to driver input and reliability in speed limit compliance
Data Source
AI summary
A vehicle speed control apparatus generate a speed command value to control a vehicle speed according to a detected treading amount of an accelerator pedal, determines an upper-limit speed of the vehicle according to a speed limit of a road, generates a limit command value to control the vehicle speed to be the upper-limit speed, and adjusts the vehicle speed according to one of the speed command value and the limit command value to cause the lower vehicle speed. If the upper-limit speed is updated due to a change in the speed limit of the road while the vehicle speed is being adjusted according to the limit command value, a rate of change of the vehicle speed is limited continuously until a predetermined timing.