Belt Driving Controller Dual-Loop Speed Control
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Solution Overview
Problem
Existing belt driving controllers for image forming devices struggle to accurately control the surface speed of intermediate transfer belts due to limitations in response frequency, which leads to misalignment of toner images and image failures like color shifts, as they cannot effectively compensate for variations in the reduction mechanism and motor eccentricity without destabilizing the feedback control system.
Innovation Solution
A belt driving controller with a dual-speed control loop system, utilizing a first speed control loop to manage surface speed and a second speed control loop to manage driving axis speed, including detectors for rotation angle and belt displacement, and compensators to adjust motor speed, allowing for higher response frequencies and accurate control of belt speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the response frequency of the feedback control system is increased to control motor eccentricity and reduction mechanism variations, then the control accuracy of belt surface speed is improved, but the system becomes unstable due to mechanical resonance frequency limitations
Solution Approach 1:
The patent divides the single feedback control system into two separate control loops: a first speed control loop that controls the surface speed of the belt at a lower response frequency (below mechanical resonance), and a second speed control loop that controls the driving axis speed at a higher response frequency (above mechanical resonance). This segmentation allows each loop to operate within its stable frequency range while achieving overall high-precision control.
Solution Approach 2:
The patent introduces a speed calculator as an intermediary component that calculates both the surface speed of the belt and the driving axis speed from detector signals. This intermediary processing enables the separation of control targets and frequencies without requiring direct high-frequency feedback from the belt surface speed detector.
2Measurement precision
If the response frequency of the control system is set above the mechanical resonance frequency (e.g., 500 Hz), then the control accuracy for motor eccentricity compensation is improved, but the system cannot effectively control lower frequency disturbances (e.g., 40 Hz motor rotation variations)
Solution Approach 1:
The patent segments the control frequency range by assigning different response frequencies to different control loops. The second speed control loop operates at high response frequency (above 500 Hz) to control motor eccentricity and reduction mechanism variations, while the first speed control loop operates at lower frequency to control overall belt surface speed and compensate for low-frequency disturbances through integration control.
Solution Approach 2:
The patent implements dual feedback loops where the second loop provides high-frequency feedback for precise motor axis control and the first loop provides low-frequency feedback for overall belt speed stabilization. The integrated control signals from both loops ensure comprehensive disturbance rejection across the full frequency spectrum.
3Measurement precision
If a filter is disposed in the feedback control system to control belt thickness variation and driving roller eccentricity, then the control accuracy is improved, but the phase lag increases and mechanical resonance frequency interference occurs
Solution Approach 1:
The patent segments the filtering and control functions between two loops. The first speed control loop uses filtering to control belt thickness variation and driving roller eccentricity at low frequency, avoiding phase lag and resonance issues. The second speed control loop operates unfiltered at high frequency to control motor and reduction mechanism variations, where filtering would be ineffective anyway.
Data Source
AI summary
A belt driving controller includes a driving roller connected to a driving axis, a plurality of driven rollers, an endless belt provided to surround the driving roller and the driven rollers in a tensioned state, a motor connected to the driving axis via a reduction mechanism; a first detector provided near the driving axis and configured to detect a rotation angle of the driving axis, a second detector configured to detect a displacement of the endless belt, and a control unit configured to control driving of the endless belt.