Motor Control System for Laser Scanning Unit Chatter Reduction
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Solution Overview
Problem
Existing motor control systems for polygonal mirrors in electrophotographic imaging devices suffer from significant overshoot and undershoot, known as 'chatter', due to the accumulation of integral error during startup, leading to extended times to reach steady state speed.
Innovation Solution
A closed-loop control system with a controller that generates a reference signal with a gradual acceleration profile, allowing the motor to accumulate integral error more slowly, preventing overshoot and undershoot, and enabling the motor to reach steady state faster.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If full acceleration current is provided to the mirror motor during startup, then the motor accelerates quickly towards target speed, but the integrator accumulates significant integral error causing overshoot and undershoot (chatter)
Solution Approach 1:
The system performs preliminary action by pre-charging the capacitor in the integrator circuit to a predetermined voltage level before motor startup. This preliminary charging establishes an initial integral error value that counteracts the accumulated error during acceleration, preventing overshoot and undershoot while maintaining quick acceleration response.
2Measurement precision
If the integrator accumulates integral error during motor acceleration, then the control system can respond to speed deviations, but the accumulated error causes the motor to overshoot and undershoot target speed
Solution Approach 1:
The system applies preliminary anti-action by pre-charging the integrator capacitor to create an initial error signal that opposes the direction of error accumulation during acceleration. This counteracts the harmful effect of integral error buildup, preventing the motor from overshooting or undershooting target speed while maintaining accurate error detection.
3Device complexity
If the motor accelerates in a substantially linear manner, then the control is simple, but the integrator cannot subtract accumulated error fast enough causing extended time to reach steady state
Solution Approach 1:
By pre-charging the integrator capacitor before startup, the system performs preliminary action that reduces the time required to reach steady state. The pre-established initial error value allows the integrator to more quickly counteract accumulated error during acceleration, reducing the time the motor spends in the transient phase while maintaining simple linear acceleration control.
Data Source
AI summary
A scanning system for use in an imaging apparatus includes a mirror assembly having a rotating mirror with a plurality of facets, a motor operatively coupled to the rotating mirror and closed loop control circuitry coupled to the motor. The mirror assembly generates a lock signal indicative of whether or not the motor is substantially at a target speed. A controller is communicatively coupled to the mirror assembly for controlling rotation of the rotating mirror, the controller generating a reference signal received by the motor assembly indicating the target speed for the rotating mirror. The reference signal is varied based at least in part upon an acceleration profile that accelerates the motor so that overshoot of the target speed is substantially reduced.