Rotation Detection for Sensorless Motor Startup in Image Forming
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Solution Overview
Problem
Conventional image forming apparatuses with sensorless brushless motors face instability and startup failures due to incorrect estimation of the rotor's initial position, especially when the rotor is forced to rotate during estimation, leading to misalignment and prolonged startup times.
Innovation Solution
A rotation detector system that includes a motor with coils of two or more phases, a current detector, and a hardware processor to estimate the initial rotor position and control energization patterns, while determining whether the rotor is rotating or stopped, ensuring accurate startup by avoiding external rotation during estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulsed current is applied to estimate rotor initial position, then the initial position can be determined, but the estimation becomes inaccurate if the rotor rotates during measurement
Solution Approach 1:
The system applies pulsed current to the motor coils before starting the motor to forcibly position the rotor at a specific position. This preliminary action ensures the rotor is stationary during initial position estimation, preventing rotation that would disrupt the measurement. The controller then determines the initial position based on current values measured during this controlled preliminary phase.
2Productivity
If the motor is started with wrongly estimated initial position, then startup can proceed, but the startup operation becomes unstable with violent rotor behavior
Solution Approach 1:
The controller measures current values flowing in the motor coils during the preliminary positioning phase and uses this feedback to determine the initial position of the rotor. This feedback mechanism ensures accurate position detection, which then enables stable motor startup with proper synchronization between rotor position and energization pattern, preventing violent rotor behavior and startup failures.
3Ease of operation
If rotor position is estimated while rotor is rotating by external force, then measurement can be performed, but reverse voltage disturbs the pulsed current and causes wrong estimation
Solution Approach 1:
The system applies pulsed current in a controlled manner before motor startup to counteract any external forces that might cause rotor rotation. By establishing this preliminary controlled state, the system prevents reverse voltage generation that would otherwise disturb the pulsed current measurement, ensuring accurate initial position estimation even in the presence of external influences.
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 solution stabilizes the startup process by accurately determining the rotor's initial position and preventing misalignment, reducing startup time and failure rates in image forming apparatuses.
Implementation Method 1
a current detector that detects currents flowing in coils of at least two phases among the coils of two or more phases
Implementation Method 2
estimates an initial position of the rotor based on current values of the currents detected by the current detector
Data Source
AI summary
A rotation detector includes a motor, a current detector and a hardware processor. The motor includes coils of two or more phases and a rotor. The current detector detects currents flowing in coils of at least two phases among the coils of two or more phases. The hardware processor estimates an initial position of the rotor based on current values of the currents detected by the current detector to start the motor, controls an energization pattern on the phases to rotate and start the motor based on the estimated initial position, and determines whether the rotor stops or is rotating before completing the estimation of the initial position.