Valve Duty Control Using Load Torque Feedback
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Solution Overview
Problem
Conventional control devices for valve devices face challenges in setting an appropriate upper limit for the duty ratio due to uncertainties such as foreign substance entry or fluid freezing, which can lead to malfunction or reduced performance, and balancing this with maintaining responsiveness.
Innovation Solution
The control device includes a stress computation unit to calculate the stress on the valve member based on the actual rotation angle and duty ratio, and an actual duty computation unit to adjust the duty ratio dynamically, ensuring the valve member is not subjected to excessive stress, thereby preventing malfunctions while maintaining responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the duty ratio upper limit is set high to maintain responsiveness, then the responsiveness is improved, but the reliability deteriorates due to risk of malfunction from foreign substance entry or fluid freezing
Solution Approach 1:
The duty ratio upper limit is made dynamic rather than fixed. The control device adjusts the duty ratio upper limit based on the operating condition of the valve member, specifically using the relationship between the driving force and rotation speed. When the valve member encounters resistance (foreign substance or freezing), the rotation speed decreases, which automatically reduces the duty ratio upper limit, preventing malfunction while maintaining responsiveness during normal operation.
Solution Approach 2:
The control device uses feedback from the valve member's rotation speed to adjust the duty ratio upper limit. By monitoring the actual rotation speed and comparing it with the driving force, the system determines the operating condition and dynamically adjusts the duty ratio upper limit accordingly, creating a closed-loop control that balances responsiveness and reliability.
2Reliability
If the duty ratio upper limit is set low to prevent malfunction, then the reliability is improved, but the responsiveness deteriorates
Solution Approach 1:
The duty ratio upper limit is made dynamic rather than fixed. The control device adjusts the duty ratio upper limit based on the operating condition of the valve member, specifically using the relationship between the driving force and rotation speed. When the valve member encounters resistance (foreign substance or freezing), the rotation speed decreases, which automatically reduces the duty ratio upper limit, preventing malfunction while maintaining responsiveness during normal operation.
Solution Approach 2:
The control device changes the parameter (duty ratio upper limit) based on operating conditions. By using the relationship between driving force and rotation speed as a basis for adjustment, the system adapts the duty ratio upper limit to match the actual operating state, allowing high responsiveness during normal operation and high reliability during abnormal conditions.
Data Source
AI summary
An instruction duty computation unit computes an instruction duty ratio representing a ratio between an energization time and a non-energization time of a motor based on an actual rotation angle detected by a rotation angle sensor and a target rotation angle of a valve member. The rotation angle sensor detects an actual rotation angle of a valve member of a fluid control valve. A stress computation unit computes a valve member load torque of the valve member based on the actual rotation angle and an actual duty ratio of the motor. An actual duty computation unit computes a new value of the actual duty ratio based on an instruction duty ratio computed by using an instruction duty computation unit and a valve member load torque computed by using a stress computation unit.