Vehicle Cabin Antifogging Control Using Water Vapor Estimation
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Solution Overview
Problem
Conventional air conditioners in vehicles, particularly in battery electric vehicles (BEVs), face challenges in reducing the frequency of outside air introduction mode to prevent windshield fogging due to low humidity measurement accuracy, leading to reduced heating efficiency and increased power consumption.
Innovation Solution
An air conditioning control method that calculates the amount of water vapor in a vehicle cabin by obtaining parameters related to water vapor entering and exiting the cabin, as well as condensation on vehicle forming panels, without relying on humidity sensors, and executes antifogging operations based on these parameters to reduce windshield fogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the air conditioner switches to outside air introduction mode to prevent windshield fogging, then the dew point temperature decreases and fogging is prevented, but the heating efficiency is reduced and power consumption increases
Solution Approach 1:
The system continuously monitors water vapor amount in the vehicle cabin and uses this feedback to dynamically control the air conditioner's operation mode. When water vapor exceeds the threshold, the system switches to outside air introduction mode; otherwise, it maintains inside air circulation, creating a closed-loop control system that optimizes energy usage while preventing fogging
Solution Approach 2:
The patent replaces conventional humidity sensors with a calculation-based water vapor amount detection method that uses temperature and pressure data from existing sensors. This substitution eliminates measurement errors associated with conventional sensors and enables more accurate control decisions, reducing unnecessary mode switches and power consumption
2Measurement precision
If conventional humidity sensors are used to detect water vapor in the vehicle cabin, then the system can monitor humidity levels, but the measurement accuracy is low under certain conditions leading to increased frequency of outside air introduction mode
Solution Approach 1:
The patent replaces physical humidity sensors with a calculation-based detection method that derives water vapor amount from temperature and pressure measurements using thermodynamic relationships. This substitution eliminates sensor drift and measurement errors, providing accurate water vapor detection without the limitations of conventional humidity sensors
Solution Approach 2:
The system uses temperature and pressure data as intermediary measurements to calculate water vapor amount indirectly. Rather than directly measuring humidity with unreliable sensors, the system uses these intermediate physical quantities that can be measured accurately with existing sensors to infer the water vapor state
Data Source
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AI summary
[Problem] To cause an air conditioner to appropriately execute antifogging operation for reducing fogging of a front windshield by accurately grasping the amount of water vapor in a vehicle cabin. [Means for Solution] An air conditioning control method for a vehicle includes: obtaining a first parameter related to an amount of water vapor entering inside of a vehicle cabin 21 defined by a front windshield 22 and a vehicle cabin forming panel (roof panel 23), and an amount of water vapor exiting from the inside of the vehicle cabin; obtaining a second parameter related to condensation occurring on the vehicle cabin forming panel in the vehicle cabin; calculating an amount of water vapor in the vehicle cabin based on the first parameter and the second parameter; and executing antifogging operation for the front windshield by an air conditioner 3 that blows air-conditioning air into the vehicle cabin, based on the amount of water vapor.