What Is an Electrodynamic Shaker?
What Is an Electrodynamic Shaker?An electrodynamic shaker is a test system used in vibration testing that converts electrical energy into controlled mechanical vibration, applying loads to the test specimen at defined frequency, amplitude, and acceleration values.
Electrodynamic shakers allow precise control of vibration parameters such as frequency (Hz), acceleration (g), displacement (mm), velocity (mm/s), and RMS/Grms values. These systems make it possible to perform vibration tests including sine, random, shock, resonance search, Sine on Random (SoR), Random on Random (RoR), and mechanical shock tests with high precision and repeatability.
An electrodynamic shaker consists of five main components:
- Shaker body
- Power amplifier
- Vibration controller
- Accelerometers
- Head expander and/or slip table
When alternating current is applied to the coil (armature / moving coil) placed inside a fixed magnetic field, the coil moves back and forth, transmitting this motion to the specimen attached to the test table as vibration. The magnitude and character of the vibration are precisely controlled based on the properties of the applied electrical signal.
Electrodynamic shakers are widely preferred in automotive, defense, aerospace, and industrial product testing thanks to their wide frequency range, precise and repeatable testing capability, broad test scenario support, and compliance with international standards.
The head expander enlarges the test surface to make vertical vibration tests easier, while
the slip table shifts vibration to the horizontal axis, allowing simulation of real operating conditions. These two pieces of equipment are essential complements to vibration test systems.
With slip tables and head expanders:
- Real-world usage scenarios are simulated more accurately
- Test repeatability improves
- Connection errors and measurement uncertainty are reduced
- Compliance with international standards is ensured.
A head expander is a rigid adapter plate attached to the moving table (armature) of an electrodynamic shaker that increases the test surface area. It can be used for specimens that don’t fit on the small armature surface, for testing multiple specimens at the same time, for more balanced load distribution, and to make specimen mounting easier.
The head expander is included in the shaker system’s maximum payload capacity. Its own resonance frequencies must lie outside the test frequency range, and it must be sufficiently rigid so that it does not damp the vibration.
A slip table is a mechanical system that converts the vertical (Z-axis) motion produced by the electrodynamic shaker into horizontal (X- or Y-axis) vibration. This way, the product can be tested under the horizontal vibration conditions it experiences in real use.
The slip table can be used for simulating horizontal vibrations during transport and operation, testing large and heavy specimens, and direction-dependent testing of automotive and aerospace components. Slip table systems are usually supported by oil-film bearings or air bearings to provide low friction.
The armature is the moving main part of an electrodynamic shaker that directly produces the vibration and transfers it to the test specimen. It is considered the heart of the shaker. All mechanical motion applied during vibration testing is generated by the armature’s back-and-forth linear motion.
The main duties of the armature: to convert electromagnetic force into mechanical motion, to transmit the generated vibration to the test table, and to provide the moving surface to which the test specimen is attached. In short, the part that vibrates and shakes the specimen during the test is the armature.
The specimen can be attached directly to the armature. If needed, a head expander is mounted on the armature. For large specimens, the armature works together with a slip table. The maximum mass the armature can carry defines the system’s payload capacity.