Brushless Motor Speed Control via Deviation Correction
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Solution Overview
Problem
The existing technologies for controlling the rotation of brushless motors in image forming apparatuses face challenges due to fluctuations in rotation speed caused by changes in magnetic flux, leading to ineffective PI control and unstable motor operation.
Innovation Solution
The implementation of a control unit that performs multiple rotation control processes, including switching between FG and BD rotation control based on deviation and integrated values, and determines the sign correspondence of deviations to manage the integration of speed deviations, thereby stabilizing the motor speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If PI control is used to suppress residual deviation in brushless motor rotation speed, then the rotation speed stability should be improved, but the control becomes ineffective due to fluctuation in rotation speed caused by magnetic flux changes
Solution Approach 1:
The patent changes the control parameter from integrating the raw deviation signal to integrating a corrected deviation signal that has been adjusted by adding a value proportional to the square of the rotation speed. This parameter transformation eliminates the harmful effect of rotation speed fluctuation on the integrated value, allowing PI control to function effectively despite magnetic flux changes.
Solution Approach 2:
The patent implements a feedback mechanism where the rotation speed is continuously monitored and used to calculate a correction value that is added to the deviation signal before integration. This feedback loop compensates for the harmful effects of magnetic flux changes by dynamically adjusting the integrated value based on actual rotation speed, thereby maintaining control effectiveness.
2Stability of the object's composition
If the integrated value of deviation is continuously updated in PI control, then the residual deviation should be suppressed, but the integrated value increases due to fluctuation in rotation speed, causing unwanted increase in integrated factors
Solution Approach 1:
The patent transforms the integration parameter by adding a correction term proportional to the square of rotation speed before integration. This prevents the unwanted accumulation of integrated factors by compensating for rotation speed fluctuations, allowing continuous integration without harmful accumulation.
3Measurement precision
If Hall elements are used to detect rotor position and rotation speed, then the detection precision should be improved, but the detected rotation speed is greatly varied by noise and magnetic flux changes
Solution Approach 1:
The patent uses the detected rotation speed as feedback to calculate a correction value that compensates for noise and magnetic flux variations. By continuously monitoring the actual rotation speed and adjusting the integrated deviation accordingly, the system maintains accurate control despite detection variations caused by noise.
Solution Approach 2:
The patent introduces an intermediary correction mechanism that mediates between the noisy detection signal and the control action. The correction value, calculated based on the detected rotation speed, acts as an intermediary that filters out the harmful effects of noise and magnetic flux changes before the signal is used for control.
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 approach effectively suppresses residual deviations and stabilizes the rotation speed of the brushless motor, overcoming the limitations of PI control and ensuring accurate motor control despite magnetic flux fluctuations.
Implementation Method 1
a magnetic flux change detection unit outputting a detection signal in accordance with a change in a magnetic flux of the coils caused by the rotation of the rotor
Implementation Method 2
an optical sensor outputting a photoreception signal in accordance with the presence or absence of reception of the light beam deflected by the rotating polygon mirror
Data Source
AI summary
An image forming apparatus includes a control unit performing a first rotation control process of switching on and off current-supplying in accordance with a change in a first deviation between a first rotation speed of a brushless motor and a target speed regardless of a change in an integrated value of the first deviation; a second rotation control process of calculating an integrated value of a second deviation between a second rotation speed of the brushless motor and the target speed, and switching on and off the current-supplying in accordance with a change in the second deviation and a change in the integrated value of the second deviation; and a rotation control switching process of switching to the second rotation control process when it is determined that the first deviation has entered a prescribed range during the first rotation control process.