Sensorless Motor Control via Induced EMF Positioning
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Solution Overview
Problem
Existing motor control devices for vehicular cooling fans require position sensors to determine the magnetic pole position of the motor rotor, which increases costs and complexity, and struggle to quickly transition from a non-driving to a driving state without these sensors, leading to delayed fan operation.
Innovation Solution
A motor control device that detects rotational position and speed without sensors, using induced electromotive force to position the rotor and decelerate the motor through short-circuiting phases, allowing immediate start-up and preventing excessive current flow by controlling energization phases based on predetermined speed thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is provided to detect magnetic pole position, then the motor can be controlled accurately, but the number of parts and costs increase
Solution Approach 1:
The patent extracts the position detection function from a separate physical sensor and integrates it into the existing inverter circuitry. The inverter's switching devices and detection circuits are used to sense the magnetic pole position indirectly through current measurements and commutation timing, eliminating the need for a dedicated position sensor while maintaining detection accuracy
Solution Approach 2:
The inverter circuit is designed to serve multiple functions: motor control, energy regeneration, and magnetic pole position detection. The same switching devices and detection circuits used for motor control are also utilized to determine the magnetic pole position, making the system multi-functional and reducing overall component count
2Speed
If the motor is driven immediately upon receiving a drive directive, then the cooling fan starts quickly, but the motor may not be positioned correctly without sensor feedback
Solution Approach 1:
The system performs preliminary positioning actions by detecting the magnetic pole position through the inverter circuits before initiating full motor drive. The control device determines the appropriate energization phase based on the detected magnetic pole position, ensuring the rotor is correctly positioned before rapid acceleration begins
Solution Approach 2:
The system implements feedback by continuously monitoring the magnetic pole position through the inverter's detection circuits during motor operation. This feedback allows the control device to adjust energization timing and phase to maintain accurate rotor positioning even during rapid start-up, ensuring both speed and positioning accuracy
3Measurement precision
If the motor rotates at high speed, then the detection accuracy of rotational position is sufficient, but the motor cannot start quickly from a non-driving state
Solution Approach 1:
The system performs preliminary detection of the magnetic pole position through the inverter circuits before initiating motor rotation. This preliminary action provides the necessary positioning information to start the motor immediately at the correct phase, eliminating the need for gradual acceleration or positioning routines that would waste time
Solution Approach 2:
The system changes the detection parameters dynamically based on motor speed. At low speeds or during startup, the system uses inverter-based detection methods that provide sufficient accuracy without requiring high rotation speeds. The detection strategy is adapted according to the operational phase, allowing immediate startup while maintaining accuracy
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
Enables rapid transition from a non-driving to a driving state without sensors, preventing damage from excessive current and ensuring accurate motor control, thus improving the efficiency and reliability of the motor control system.
Implementation Method 1
A publicly known technology can detect a magnetic pole position of the motor rotor without using sensors based on an induced electromotive force of an idle coil when the motor is driven.
Implementation Method 2
a deceleration device that decelerates the motor by short-circuiting a plurality of energization phases of the motor via the inverter
Data Source
AI summary
A motor control device includes: a motor; an inverter; and a control device. The control device includes: a detection device detecting a rotational position and a revolution speed of the motor; a positioning control device for a rotor; a deceleration device for the motor; and a determination device for the revolution speed of the motor. When the revolution speed is higher than or equal to the first predetermined revolution speed, the motor control device starts controlling the motor to rotate at the target speed, according to the rotational position, without executing the positioning control. When the revolution speed is lower than the first predetermined revolution speed and higher than or equal to the second predetermined revolution speed, the deceleration device decelerates the motor. When the revolution speed is lower than the second predetermined revolution speed, the positioning control device starts executing the positioning control.