Gas Discharge Laser Pulse Energy Control via Duty Cycle Feedforward
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Solution Overview
Problem
Existing gas discharge laser systems face challenges in maintaining consistent pulse energy during bursts, particularly at the initiation of a burst, due to varying trigger intervals and duty cycles, leading to inefficiencies and errors in energy output.
Innovation Solution
A duty cycle feedforward algorithm is introduced to predict and adjust the first pulse voltage based on historical data, using a model that accounts for trigger interval and duty cycle changes, ensuring consistent energy output by pre-filtering the trigger interval signal and adapting the voltage command to maintain constant energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback-based energy control system is used to maintain constant pulse energy, then energy stability is improved, but response time to trigger interval changes is insufficient and initial pulse energy errors occur
Solution Approach 1:
The patent implements a feedforward control mechanism that calculates and applies voltage adjustments before the burst sequence begins. The controller pre-computes the necessary voltage command modifications based on the anticipated trigger interval and duty cycle, eliminating the need to wait for feedback from actual energy measurements. This preliminary action ensures that the first pulse energy is correct from the start rather than requiring correction after the fact.
Solution Approach 2:
The patent combines feedforward prediction with feedback correction. While the feedforward mechanism provides immediate response to trigger interval changes, the system also incorporates feedback from actual energy measurements to refine and adjust the voltage commands for subsequent pulses. This hybrid approach maintains both rapid response and long-term energy stability.
2Reliability
If voltage commands are adjusted based on previous pulse energy errors, then energy consistency is improved, but initial pulse energy accuracy deteriorates due to lack of prior data
Solution Approach 1:
The system performs preliminary calculations of the required voltage command based on the known trigger interval and duty cycle parameters before the burst begins. By using the feedforward model to predict the appropriate voltage adjustment in advance, the system eliminates the need to rely on previous pulse data that may not be available or accurate for the first pulse.
Solution Approach 2:
The patent introduces a feedforward control model as an intermediary between the trigger signal and the voltage command. This intermediary component uses the trigger interval and duty cycle information to compute the necessary voltage adjustment, acting as a mediator that provides accurate initial pulse energy control without depending on feedback from previous pulses.
3Adaptability or versatility
If the laser system adapts to varying trigger intervals and duty cycles, then versatility is improved, but energy control precision deteriorates during transitions
Solution Approach 1:
The patent implements a dynamic control model that continuously adapts to changing trigger intervals and duty cycles. The feedforward controller uses real-time information about the trigger interval and duty cycle to dynamically adjust the voltage command, allowing the system to maintain energy precision across varying operating conditions rather than being fixed to a single operating point.
Solution Approach 2:
The system changes its control parameters based on the trigger interval and duty cycle values. By using these parameters as inputs to the feedforward model, the controller automatically adjusts its voltage commands to compensate for the effects of varying trigger intervals and duty cycles, maintaining energy precision across different operating conditions.
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
The solution effectively suppresses inefficiencies and errors in initial pulse energy, maintaining consistent output energy across bursts by continuously adapting to changes in trigger intervals and duty cycles, thereby improving laser efficiency and accuracy.
Implementation Method 1
A gas discharge laser system may include: a laser which may produce pulses of laser light... a resonant charger... which may produce a voltage across a pair of electrodes in the laser for a discharge between the electrodes
Implementation Method 2
a laser which may produce pulses of laser light... An exemplary energy controller aims to keep the measured laser system output pulse energy of each pulse constant
Data Source
AI summary
A method and apparatus is disclosed which may comprise: a gas discharge laser system energy controller which may comprise: a laser system energy controller providing a first laser operating parameter control signal based on an error signal related to a value of the output energy of the laser system compared to a target value for output energy and an energy controller model of the value of the first laser operating parameter necessary to change the value of the laser system output energy to the target value; a first laser system operating parameter control signal modifier providing a modification to the first laser system operating parameter control signal based upon a controller signal modification model of the impact of a second laser system operating parameter on the value of the first laser system operating parameter necessary to change the value of the output energy to the target value.