Sensorless Fan Motor Control for Smooth Open- to Closed-Loop Switching
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Solution Overview
Problem
Existing fan systems with permanent magnet synchronous motors lacking position sensors experience noise and vibration due to large torque commands during transitions from open-loop to closed-loop control, especially when adjusting air quantity.
Innovation Solution
A control method that initiates operation with a d-axis current command, transitions to closed-loop control by gradually decreasing d-axis and increasing q-axis current, and stabilizes with proportional integral control, reducing torque commands and enhancing smooth operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a greater torque command is used in the low-speed stage before closed-loop control to ensure motor starting success, then the motor starting reliability is improved, but the actual air quantity becomes larger than commanded, causing obvious noise during air quantity adjustment
Solution Approach 1:
The patent applies dynamics by transitioning the control system from open-loop to closed-loop control as the motor speed increases. The control mode dynamically changes based on the motor's operating state, allowing the system to use high torque commands only during the initial open-loop stage when noise is less problematic, and switch to precise closed-loop control at higher speeds to eliminate excessive air quantity and noise.
Solution Approach 2:
The patent changes the control parameters by switching from torque-based open-loop control to speed/position-based closed-loop control. This parameter transformation allows the system to achieve reliable starting with high torque commands while subsequently maintaining precise air quantity control through back electromotive force observation, thereby resolving the noise issue during air quantity adjustment.
2Power
If the air quantity command is set to be small at the starting moment of the motor, then the torque command required for switching to closed-loop control is reduced, but the actual air quantity becomes larger due to the high starting speed, causing noise
Solution Approach 1:
The patent applies preliminary action by using open-loop control with high torque commands during the initial motor starting phase to achieve reliable startup and reach a sufficient speed threshold. This preliminary high-power action is acceptable because it occurs before the fan blades fully engage with the air flow, minimizing noise. Once the motor reaches adequate speed, the system transitions to closed-loop control to precisely regulate air quantity and eliminate noise during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method ensures smooth start and operation of the fan, reduces noise and vibration, and improves user comfort by minimizing air quantity noise during transitions.
Implementation Method 1
Speed and position of such a permanent magnet synchronous motor free of the position sensor are generally determined through observation of its back electromotive force.
Implementation Method 2
controlling the electric motor to start to operate through a d-axis current command... by applying a current to a d-axis of the electric motor
Implementation Method 3
increasing a q-axis current corresponding to a q-axis current command until the q-axis current is increased to a first target current
Data Source
AI summary
A control method for a fan, a fan, a household appliance, and a computer-readable storage medium are provided. The fan includes an electric motor. The control method includes: controlling the electric motor to start to operate through a d-axis current command in response to a start command; obtaining an actual speed of the electric motor, and starting timing when the actual speed reaches a first target speed; and decreasing, when the timed duration reaches a first preset duration, a d-axis current corresponding to the d-axis current command until the d-axis current is decreased to 0, and increasing a q-axis current corresponding to a q-axis current command until the q-axis current is increased to a first target current.