Random-on-random

A vibration controller feature used within a closed-loop test system to drive shakers by generating a profile that combines broadband random excitation with multiple narrow-band signals.

Random-on-random

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Random-on-random (RoR) control simulates real-world complex vibration environments with a combination of a broadband random signal and one or more superimposed random narrow-bands. Both signal types are usually present simultaneously and the narrow-bands can appear at fixed frequencies or sweep over a predefined range. The overall random PSD (power spectral density) shifts with time or is related to a variable-speed device.

In RoR, a more complex function of the basic random control profile, all resonant frequencies of any given payload are excited at once; thus, it is well suited for product qualification and fatigue tests. A typical example is the repetitive stress on a truck’s headlights, as the vehicle changes speed while travelling on rough terrain.

USE SCENARIOS

Simulation of vibration characterized by a broadband random profile with one or more superimposed random narrow-band signals
Truck vibration testing during variations in speed
Testing of caterpillar-tracked vehicles that have two or more drive trains for changing speed and direction, such as bulldozers, tanks and excavators
Testing of machines with reciprocating or rotating components, such as propeller-driven aircraft

CHARACTERISTICS

In this type of test profile, the broadband signal also consists of a user-specified breakpoint table of PSD versus frequency. Typically, up to 12 narrow-band signals can be concurrently generated, where each band has independently set PSD amplitude, frequency-sweep range and rate. Narrow-bands can be configured both at user-specified fixed frequencies or in sweeping mode.

Slopes and crossover points are automatically calculated by the control algorithm. There is usually a choice to sum the narrow-band and broadband or to use the largest PSD value from the profile. This allows the swept narrow-band to either dominate on a broadband slope or to be reduced where the broadband is higher.

There usually is a harmonic mode, whereby subsequent narrow-bands are configured using integer multiples of the first narrow-band’s frequency parameters.

RoR control contains all of the automatic and manual test controls that are available in the random profile feature. A PSD amplitude versus frequency sweep envelope for narrow-bands is typically included, providing a pre-test validation of the configuration. During tests, individual narrow-bands and the broadband can usually be turned on and off manually, or automatically according to a pre-defined timetable.

File	Description	Type	Languages	Size
Vibration Control Software for VC-LAN Vibration Controller Types 7541 and 7542		Technical Document	English	867 KB

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Random-on-random

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