Adaptive Arc Discharge Detection in Plasma Processes
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Solution Overview
Problem
Existing arc discharge detection methods in plasma processes are unreliable due to variations in output voltage and current, leading to erroneous detection of arcs, especially during plasma ignition and when residual ripple is present, requiring adjustable threshold values that are not optimally selected.
Innovation Solution
A method and device for detecting arc discharges by determining an extreme value of a signal within a predetermined time period, comparing instantaneous values with the extreme value, and detecting arcs when deviations exceed a predetermined deviation, which is adaptively set based on the extreme value to account for varying process conditions, using filtering techniques and a comparator to generate a reference signal for reliable detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold value is used for arc detection, then the detection method is simple, but false detection occurs during plasma ignition and residual ripple
Solution Approach 1:
The patent applies dynamics by making the threshold value adaptive rather than fixed. The threshold automatically adjusts based on the extreme values detected in the signal over a predetermined time period. This allows the detection system to adapt to changing plasma conditions (ignition, steady state, ripple) without requiring manual reconfiguration, thereby maintaining reliability across different operating conditions while keeping the system relatively simple.
Solution Approach 2:
The patent changes the parameter of the threshold value from a static fixed value to a dynamic value that varies with signal conditions. By calculating the extreme values (maximum or minimum) over a time period and using these to set adaptive thresholds, the system responds appropriately to different plasma states. This parameter change enables reliable detection during ignition and steady-state operation without false alarms from residual ripple.
2Reliability
If the predetermined deviation is made large to prevent false detection from residual ripple, then false alarms are reduced, but arc detection sensitivity decreases
Solution Approach 1:
The predetermined deviation is made dynamic rather than fixed. It automatically adjusts based on the extreme values detected in the signal. During steady-state operation with low ripple, the deviation can be smaller, maintaining high sensitivity for arc detection. During plasma ignition or high-ripple conditions, the deviation increases automatically, preventing false alarms. This dynamic adjustment resolves the contradiction between sensitivity and false alarm reduction.
Solution Approach 2:
The deviation parameter changes adaptively based on signal conditions. By recalculating the deviation from extreme values over time, the system maintains optimal sensitivity during normal operation while automatically reducing sensitivity (increasing threshold) during conditions that cause false alarms. This parameter change enables the system to maintain high measurement precision when needed while preventing false detection.
3Measurement precision
If manual threshold adjustment is performed to optimize arc detection, then detection accuracy improves, but operation complexity and time increase
Solution Approach 1:
The detection system performs self-service by automatically adjusting its own threshold values and deviation parameters based on the signal it receives. The system calculates extreme values from the signal, determines appropriate thresholds and deviations, and applies these automatically without requiring manual intervention. This self-adjusting capability maintains high detection accuracy while eliminating the need for manual threshold optimization, thereby improving ease of operation.
Solution Approach 2:
The system uses feedback by continuously monitoring the signal, determining extreme values, and using this information to adjust the detection thresholds and deviation. This closed-loop approach allows the system to automatically optimize its detection parameters based on actual operating conditions, maintaining high accuracy without manual intervention and simplifying operation.
4Speed
If the predetermined time period for extreme value calculation is shortened, then the response time to arcs improves, but the accuracy of extreme value determination decreases
Solution Approach 1:
The predetermined time period is made dynamic rather than fixed. The system can adjust the time period based on operating conditions and requirements. During critical phases like plasma ignition or when arcs are detected, the system can use shorter time periods for faster response. During steady-state operation, longer time periods can be used for more accurate extreme value determination. This dynamic adjustment resolves the contradiction between response speed and measurement accuracy.
Data Source
AI summary
An arc discharge detection device is used for detecting arc discharges in a plasma process. The arc discharge detection device includes a comparator configured to emit an arc discharge detection signal and receive an instantaneous value of the signal or a signal proportional thereto, a minimum or maximum value detection device configured to receive the signal and to determine a minimum or maximum value of the signal within a predetermined time period, a setting means configured to receive the minimum or maximum value and to generate a reference signal from the minimum or maximum value, such that the reference signal is supplied to the comparator, and such that the comparator changes the signal level of the arc discharge detection signal when the comparator detects that the instantaneous value has reached the reference signal.