Rodless Inertial Shaker for Direct-Coupled Modal Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modal testing of large and complex structures, such as aircraft, is often expensive, time-consuming, and poses safety risks due to the need for complicated suspension systems and inefficient force application, especially when conducted at elevated heights.
Innovation Solution
The use of a rodless inertial shaker with integrated force transduction, featuring a voice coil actuator and piezoceramic force transducers, allows direct coupling to the structure under test, eliminating the need for stingers and enabling precise force measurement and decoupling of inertial shaker dynamics from the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional shakers with suspension systems are used for modal testing, then force can be applied to the structure, but safety risks increase and setup complexity increases due to elevated height operations and complicated suspension requirements
Solution Approach 1:
The patent extracts and eliminates the suspension system from the testing apparatus. By using a rodless inertial shaker that can be directly coupled to the structure through adhesive or mechanical fasteners, the dangerous suspension components are removed entirely, allowing force application without the safety risks associated with elevated height operations and complex suspension systems
Solution Approach 2:
The patent replaces the mechanical suspension system with a direct coupling mechanism. The rodless inertial shaker uses adhesive bonding or simple mechanical fasteners to attach directly to the structure, substituting the complex mechanical suspension system with a simpler, safer attachment method that eliminates the need for elaborate support structures
2Force
If traditional shakers with stingers are used for modal testing, then force can be transmitted to the structure, but device complexity increases due to the need for stingers and suspension systems
Solution Approach 1:
The patent extracts and removes the stinger component from the force transmission path. The rodless inertial shaker transmits force directly to the structure through its base plate that is adhesively bonded or mechanically fastened to the structure, eliminating the need for intermediate stingers and reducing overall device complexity
Solution Approach 2:
The patent merges the force transmission function directly into the shaker base plate. The base plate serves both as the mounting surface for the inertial mass and as the interface for direct coupling to the structure, combining multiple functions into a single integrated component that simplifies the overall device
3Force
If traditional shakers are used for modal testing, then force can be applied to the structure, but measurement precision decreases due to coupling between shaker dynamics and structure dynamics
Solution Approach 1:
The patent extracts the shaker dynamics from the measurement equation by using a rodless inertial shaker with very low resonant frequency. The shaker's dynamics are effectively removed or decoupled from the structure's dynamics, allowing direct measurement of the structure's response without contamination from shaker resonances or complex coupling effects
Solution Approach 2:
The patent changes the key parameter of the shaker's resonant frequency to be very low (below 10 Hz). This parameter change ensures that the shaker operates in a regime where its dynamics do not interfere with the measurement of the structure's modal parameters, improving measurement precision by decoupling the shaker's mechanical behavior from the structure's dynamic response
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
This approach reduces safety hazards, simplifies setup, enhances force application, and allows for more flexible placement of shakers, providing accurate uncoupled dynamics measurements without the need for additional suspension systems.
Implementation Method 1
a voice coil configured to generate a magnetic field to move the inertial mass in reciprocating directions within the outer housing
Implementation Method 2
one or more force transducers affixed between the housing and the structure under test
Data Source
AI summary
A method of modal testing a structure may include rigidly coupling a body of an inertial shaker to a structure under test, wherein the shaker has a rodless inertial mass enclosed in a housing and a voice coil configured to move the inertial mass in alternating directions within the housing. The shaker is activated by applying an alternating current to the voice coil at a selected frequency, and the resulting vibration response is measured at various points on the structure under test.