Vehicle A/C Compressor Control for Evaporator Undershoot
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Solution Overview
Problem
Conventional air conditioner control systems for vehicles experience undershoot and delayed temperature convergence in vehicles, especially when the outdoor temperature is low or the target evaporator temperature is high, leading to discomfort for passengers.
Innovation Solution
A method for controlling the air conditioner that involves calculating a discharge capacity control value for a variable capacity swash type compressor using proportional-integral control, where the compressor's discharge capacity is maximized before shutdown and adjusted based on the temperature deviation and lapse time to prevent undershoot and ensure quick convergence to the target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If maximum capacity control is performed at initial operation, then temperature convergence speed is improved, but evaporator temperature drops sharply causing undershoot
Solution Approach 1:
The control method stores the discharge capacity control value from directly before A/C shutdown and applies it as the initial control value upon restart. This preliminary action prepares the system in advance to avoid sharp temperature drops, allowing the evaporator temperature to converge to the target temperature without undershoot while maintaining fast response.
Solution Approach 2:
The system uses proportional-integral control with feedback from the evaporator temperature sensor to continuously adjust the discharge capacity control value. This feedback mechanism ensures that the evaporator temperature converges to the target temperature smoothly by correcting deviations in real-time, preventing both undershoot and delayed response.
2Temperature
If proportional-integral control is performed with maximum and minimum capacity control, then undershoot is reduced, but convergence time is extended due to delayed temperature decrease
Solution Approach 1:
By storing and reusing the discharge capacity control value from before shutdown, the system eliminates the delay in temperature decrease that occurs with conventional minimum capacity control. This preliminary preparation allows the evaporator to reach the target temperature quickly without undershoot, resolving the contradiction between stability and convergence time.
3Speed
If discharge capacity is increased to reach target temperature quickly, then response time is improved, but temperature control precision deteriorates
Solution Approach 1:
The system dynamically adjusts the discharge capacity control value based on the A/C operation state. During initial operation or after shutdown, it uses the stored control value for rapid response, then transitions to proportional-integral control for precise temperature maintenance. This dynamic adaptation achieves both fast response time and high temperature control precision.
Solution Approach 2:
The proportional-integral control continuously monitors evaporator temperature and adjusts the discharge capacity to eliminate temperature deviations. This feedback ensures that once the target temperature is reached, the system maintains precise temperature control without oscillation or undershoot.
Data Source
AI summary
The present invention relates to a method for controlling a vehicle air-conditioner, which can prevent undershoot of an evaporator by performing a maximum capacity control or controlling an discharge capacity of a compressor through the outputting of an discharge capacity control value of the compressor directly before the stop of the air conditioner, and can improve the pleasant feelings of the passengers by preventing delay of response, which converges into the target temperature of the evaporator due to the delay of the decrease of the temperature of the evaporator.