MEMS Mirror Trajectory Control Using Iterative Waveform Feedback
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Solution Overview
Problem
In MEMS-based projectors, the input sawtooth wave signal for controlling vertical mirror movement often does not precisely match the output sawtooth wave movement due to system delays, inertial forces, and mechanical limitations, leading to perceptible degradation in visual quality due to non-linear ramped portions and rounded transitions.
Innovation Solution
A multi-servo time-domain system that iteratively adjusts drive elements in a drive array by calculating errors between target and output wave elements, using a controller to enforce precise trajectory control through MEMS angle feedback, and compensating for errors to minimize discrepancies between target and actual movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a standard sawtooth wave signal is used to control MEMS mirror movement, then the control signal is simple to generate, but the output mirror movement does not precisely match the input signal due to system delays and mechanical limitations
Solution Approach 1:
The patent implements a feedback mechanism where the actual mirror position is measured and used to adjust the drive signal. The controller receives feedback about the mirror's actual position and modifies the sawtooth wave signal in real-time to compensate for deviations, ensuring the mirror follows the desired trajectory despite mechanical limitations and system delays.
Solution Approach 2:
The patent modifies the parameters of the control signal dynamically. Instead of using a fixed standard sawtooth wave, the system adjusts the signal's amplitude, frequency, and waveform shape based on feedback from the mirror's actual position, transforming the control approach from static to adaptive to achieve precise trajectory control.
2Manufacturing precision
If the ramped portion of the sawtooth wave is made steeper to improve linearity, then the visual quality improves, but the acceleration of mechanical components exceeds limitations
Solution Approach 1:
The patent makes the control system dynamic by continuously adjusting the sawtooth wave parameters based on real-time feedback. The system adapts the ramped portion's slope dynamically rather than using a fixed steep slope, allowing it to achieve high linearity while respecting mechanical acceleration limits by modifying the waveform shape in response to actual mirror position and velocity.
Solution Approach 2:
The feedback mechanism allows the system to detect when the mirror is not responding as expected to the drive signal. When deviations are detected, the controller adjusts subsequent drive signals to compensate, ensuring that the mirror achieves the desired linear motion without requiring excessively steep ramps that would exceed mechanical acceleration capabilities.
3Productivity
If the blanking portion of the sawtooth wave is made more vertical to improve transition speed, then the frame rate improves, but the mechanical system cannot instantaneously move the mirror
Solution Approach 1:
The system prepares for transitions by anticipating the need to reset the mirror position. Using feedback information about the mirror's current state and velocity, the controller begins preparing the next drive signal in advance, smoothing the transition into the blanking period to ensure the mirror can realistically complete its movement before the next frame begins, thus maintaining high frame rates without demanding impossible instantaneous movements.
4Manufacturing precision
If iterative adjustment of drive elements is implemented to improve trajectory accuracy, then the precision of mirror movement improves, but the system complexity increases
Solution Approach 1:
The iterative adjustment process is driven by feedback from the actual mirror position. The controller compares the desired trajectory with the actual position, calculates the error, and uses this feedback to adjust the drive signal in subsequent iterations. This feedback-based approach achieves high precision without requiring overly complex control algorithms, as the system learns and adapts based on actual performance.
Data Source
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AI summary
Controlling a mirror in a MEMS based projector. A method includes iteratively performing various acts. The method includes inputting a time domain target wave array, with target elements, to a system for a MEMS coupled to the mirror of the projector. The time domain target wave array includes a set of n target elements. The method further includes driving the driver to move the mirror using elements in a drive array comprising a set of drive elements. The method further includes sampling a time domain output wave for the movement of the mirror to construct an output wave array with output elements corresponding to the target elements. The method further includes identifying errors between the target elements and the output elements. The method further includes modifying the drive elements in the drive array to attempt to minimize the errors when driving the MEMS on subsequent drive cycles.