Motor Control Back-EMF Detection for Startup Reliability
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Solution Overview
Problem
In motor driving control systems using single sensor driving, abnormal states such as backward rotation due to external loads cannot be effectively detected, leading to unreliable startup and continued backward rotation.
Innovation Solution
A motor driving control device and method that detects transitions in back electromotive force values during startup, determining the rotational state and direction of the motor by analyzing these values over specific detection periods, allowing for appropriate energization control to address abnormal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single sensor driving is used to reduce device complexity, then the number of sensors is reduced, but the ability to detect abnormal states such as backward rotation is lost
Solution Approach 1:
The patent uses back electromotive force (EMF) as an intermediary parameter to detect rotor rotational state. By monitoring the back EMF voltage waveform characteristics during startup, the system can determine whether the rotor is rotating in the correct direction or backward, enabling abnormal state detection without additional sensors.
Solution Approach 2:
The patent replaces mechanical sensor-based detection with electrical signal analysis. Instead of using multiple physical sensors to detect rotor position and direction, the system analyzes the electrical characteristics (back EMF) of the motor windings to infer rotational state, substituting a mechanical sensing system with an electrical measurement approach.
2Manufacturing precision
If rotor locking control is implemented before startup, then the rotor can be positioned at a predetermined position, but the system cannot respond to externally forced backward rotation
Solution Approach 1:
The patent implements feedback control by continuously monitoring the back EMF voltage waveform during startup and comparing it against expected characteristics for forward rotation. Based on this feedback, the control system can detect backward rotation and respond by preventing startup or correcting the rotational direction, enabling adaptive response to external load conditions.
Solution Approach 2:
The patent transitions from a static rotor locking approach to a dynamic detection and response system. The control system actively monitors back EMF characteristics during the startup process and can dynamically adjust its behavior based on the detected rotational state, allowing it to respond to changing external conditions such as forced backward rotation.
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 quick and reliable startup of the motor by accurately detecting abnormal states and adjusting energization to prevent backward rotation, ensuring proper motor operation.
Implementation Method 1
the control circuit unit detects a transition of values of a back electromotive force induced in the one phase in a detection period corresponding to a change timing of the position signal
Data Source
AI summary
A motor driving control device has a motor driving unit configured to selectively energize coils with a plurality of phases of a motor, a control circuit unit configured to control an operation of the motor driving unit by outputting a driving control signal to the motor driving unit, and a position detector configured to output a position signal which corresponds to any one phase of the plurality of phases and a phase of which changes depending on a position of a rotor of the motor. the control circuit unit detects a transition of values of a back electromotive force induced in the one phase in a detection period corresponding to a change timing of the position signal when beginning to start up the motor, and determines a rotational state of the motor including a rotational direction of the motor based on a detection result of the transition of the values of the back electromotive force.