Adaptive Gain Adjustment for Fatigue Test Apparatus
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Solution Overview
Problem
Fatigue testing is expensive and lengthy due to the need for repeated adjustments to apply precise forces over long periods, often resulting in overshoot or undershoot conditions that delay reaching a steady state, increasing production costs and time.
Innovation Solution
A fatigue test apparatus with a control system, gain calculation device, and variable gain feedforward device that adjusts stabilization gains based on error signals from previous iterations to reduce or eliminate overshoot/undershoot conditions, thereby shortening the test duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fatigue testing is performed with repeated adjustments to apply precise forces, then measurement precision is improved, but duration of action worsens (tests become lengthy)
Solution Approach 1:
The system performs preliminary characterization during a first iteration of the fatigue test to determine system dynamics parameters and optimal gain values. This preliminary action allows subsequent iterations to use pre-determined gain schedules, eliminating the need for repeated adjustments and significantly reducing test duration while maintaining force application precision
Solution Approach 2:
The system implements feedback control by continuously monitoring force application and adjusting actuator commands based on deviation from target forces. The feedback mechanism uses gain schedules determined from preliminary characterization to maintain precision across multiple iterations without requiring lengthy repeated adjustments
2Manufacturing precision
If traditional fatigue testing is performed with repeated adjustments, then manufacturing precision is improved, but loss of time worsens (production delays increase)
Solution Approach 1:
The system performs preliminary characterization during the first iteration to establish optimal control parameters. This preliminary action enables all subsequent iterations to proceed with pre-determined gain schedules, maintaining manufacturing precision while dramatically reducing the time lost to repeated adjustments and thereby reducing production delays
3Productivity
If stabilization gains are adjusted based on error signals from previous iterations, then productivity is improved (test duration reduced), but device complexity increases
Solution Approach 1:
The system uses feedback from error signals during the first iteration to determine optimal gain values. These gain values are then stored and reused in subsequent iterations through gain schedules, improving productivity by eliminating repeated adjustments while adding only moderate complexity through the implementation of feedback control and gain scheduling mechanisms
Solution Approach 2:
The system changes control parameters (gain values) based on error signals from the first iteration. By determining optimal gain values preliminarily and reusing them in subsequent iterations, the system improves productivity while the parameter changes themselves are computed once rather than repeatedly, limiting the increase in device complexity
Data Source
AI summary
A fatigue test apparatus includes a control system configured to receive, during a first iteration of a fatigue test of an article under test, a command signal corresponding to a particular test step of the fatigue test. The control system is configured to generate, based on the command signal and during the first iteration, a test output signal to cause a force to be applied to the article under test. The control system is configured to generate an error signal associated with the particular test step during the first iteration. A gain calculation device is configured to generate, based on the error signal, a gain adjustment value associated with the particular test step. A variable gain feedforward device is configured to provide, during a second iteration of the fatigue test and based on the gain adjustment value, a stabilization gain to the control system.