Servomotor Control Circuit for Vehicle Air Conditioner
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Solution Overview
Problem
Conventional air conditioner systems for vehicles face challenges in detecting servomotor abnormalities and stopping the servomotor quickly, especially when communications with the main control unit are impaired, leading to potential damage and unnecessary current flow due to frequent collisions with the air conditioner unit walls.
Innovation Solution
A servomotor control circuit with a receiver section, drive control section, rotation position change detection section, and operation limit check section that allows for autonomous detection of abnormality and immediate stopping of the servomotor without a command from the main control apparatus, even if communication is lost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electronic control unit and motor control circuit perform regular communications to detect abnormalities, then the system can identify servomotor issues, but the response time is delayed and communication overhead increases
Solution Approach 1:
The motor control circuit autonomously monitors its own operation status by detecting rotation position changes and determining whether the servomotor has reached the operation limit position, eliminating the need for continuous communication with the electronic control unit for status monitoring. This self-diagnosis capability enables immediate local response to abnormalities without waiting for communication cycles.
2Reliability
If the electronic control unit transmits stop commands to the servomotor control circuit, then the servomotor can be stopped, but communication delays prevent immediate stopping when abnormalities occur
Solution Approach 1:
The motor control circuit pre-establishes the capability to stop the servomotor by having the operation limit check section continuously monitor rotation position changes and compare them against predetermined limits. When the limit is exceeded, the stop command is immediately executed without waiting for communication from the electronic control unit, achieving preliminary preparation for emergency stopping.
3Adaptability or versatility
If the number of servomotors increases in the air conditioner system, then the system functionality improves, but communication time and processing delay necessarily increase
Solution Approach 1:
The system divides the monitoring and control functions into independent segments at each motor control circuit level. Each servomotor control circuit independently performs rotation position monitoring, abnormality detection, and emergency stopping without requiring centralized coordination for these basic safety functions. This segmentation allows multiple servomotors to operate independently with minimal communication overhead.
4Ease of operation
If the servomotor operates beyond the normal range without stopping, then the actuator can reach target positions, but the air mixing door or mode switching door hits the wall causing damage
Solution Approach 1:
The operation limit check section pre-establishes safety boundaries by storing predetermined operation limit positions and continuously comparing actual rotation positions against these limits. When the servomotor approaches the limit position, the system prepares to stop the motor before actual wall collision occurs, preventing damage to the air mixing door or mode switching door while still allowing full normal operation range.
Data Source
AI summary
A servomotor control circuit for an air conditioner apparatus of a vehicle includes a drive control section for controlling drive of a servomotor so that the servomotor attains a target stop position, a rotation position change detection section for detecting a change in the rotation position of the servomotor, and an operation limit check section for checking, based on the change in the rotation position of the servomotor, whether the servomotor has attained the operation limit position. The drive control section stops drive of the servomotor without reception of a servomotor drive stop command produced from a main control apparatus, when the servomotor is determined as having attained the operation limit position.