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Mechanical Actuators

Examples

 

 

Low-frequency drive unit
  • Shaker
  • Exciter

 


Applications

 

 

  • Home
  • Automotive
  • Multimedia and professional

Particularities

Mechanical actuators convert the electrical input signal into a mechanical excitation force and may be used in combination with a separate radiator (e.g. panel) in distributed mode loudspeakers and active control application for noise and vibration cancellation. 
These transducers are operated below and above the fundamental resonance frequency (usually below 500 Hz) using inertial drive technology. Most actuators contain a moving coil assembly based on electro-dynamical motor principle. 
The electrical, mechanical and thermal behavior of the drive unit at fundamental resonance frequencies can be described by the equivalent network comprising lumped elements with linear and nonlinear parameters. The linear parameters comprise the Thiele-Small parameters, visco-elastic parameters (creep factor) and electrical parameters describing the lossy inductance at higher frequencies. 
The dominant nonlinearities are the force factor Bl(x), stiffness Kms(x) or compliance Cms(x) and inductance L(x) versus displacement x and the inductance L(i) varying with the input current i. Thermal parameters describe the heating of the coil, the heat transfer to the pole tips, magnet and ambience considering conduction, radiation and convection cooling.


Critical Issues

  • Maximal peak displacement
  • High dc displacement (coil is shifted out of the gap)
  • Motor instability (bifurcation, jumping effect)
  • Thermal power handling
  • Rocking modes
  • Intermodulation distortion caused by Le(x) and Bl(x)


Standards

Audio Engineering Society
AES2 Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement

International Electrotechnical Commission
IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
IEC62458 Sound System Equipment – Electroacoustic Transducers - Measurement of Large Signal Parameters


Most relevant Measurements 

Modules of R&D SYSTEM

Modules of QC SYSTEM

Linear lumped parameters
(resonance frequency, Q-factors, Thiele/Small, creep, inductance)

Linear Parameter Measurement (LPM)

Impedance Task (IMP)
Motor + Suspension Check (MSC)
T/S Parameter Laser Fitting (TSX)

Loudspeaker nonlinearities
(Bl(x), Kms(x), L(x) , L(i))

Large Signal Identification (LSI)
Power Testing (PWT)

 

Single-valued nonlinear parameters
(Xmax , XBl , XC , Voice coil offset Xoffset , Suspension asymmetry AKms)

Large Signal Identification (LSI)
Large Signal Identification (LSI3)

Motor + Suspension Check (MSC)

Thermal parameters
(thermal resistances, time constants, capacities, air convection parameter)

Large Signal Identification (LSI)
Large Signal Identification (LSI3)
Power Testing (PWT)

 

Irregular loudspeaker defects
(Rub & Buzz, loose particles, wire beat, bottoming, air leakage noise)

Rocking Mode Analysis (RMA)
Transfer Function Measurement (TRF PRO)

Air Leak Detection (ALD)
Hi-2 Weighted Harmonic Distortion (Hi-2)
Meta-Hearing-Technology (MHT)
Spectrogram 3D Limits (3DL)

Air leakage noise localization
(position of modulated noise source)

 

Air Leak Detection (ALD)
Air Leak Stethoscope (ALS)

Sound power response

Near Field Scanner (NFS)
Polar Far-Field Measurement (POL)
Scanning Vibrometer System(SCN)

 

Phase response
(minimal-phase, excess-phase)

Transfer Function Measurement (TRF)

Spectrum Analysis (SAN)
Sound Pressure Task (SPL)
Sound Pressure and Impedance Task (SPL-IMP)

Group time delay response
(total, minimal phase)

Time Frequency Analysis (TFA)
Transfer Function Measurement (TRF)

 

Time-frequency analysis
(Wigner, cumulative decay spectrum, sonagraph, wavelet, …)

Time Frequency Analysis (TFA)
Transfer Function Measurement (TRF)

Spectrogram 3D Limits (3DL)

Nonlinear harmonic distortion
(THD, THD+N, components)

3D-Distortion Measurement (DIS)
Transfer Function Measurement (TRF)

Equalization & Alignment (EQA)
Hi-2 Weighted Harmonic Distortion (Hi-2)
Spectrum Analysis (SAN) 
Sound Pressure Task (SPL) 
Sound Pressure and Impedance Task (SPL-IMP)

Equivalent Harmonic Input Distortion

Transfer Function Measurement (TRF)

 

Intermodulation distortion
(difference-tone and sum-tone IMD)

3D-Distortion Measurement (DIS)

 

Amplitude intermodulation distortion (AMD)
(modulation of the fundamental)

3D-Distortion Measurement (DIS PRO)

EAR

Sinusoidal burst measurement

Tone Burst Measurement (TBM)
Transfer Function Measurement (TRF)

Sound Pressure Task (SPL)

Thermal and nonlinear compression
(fundamental, harmonics versus voltage)

3D-Distortion Measurement (DIS)
Multi-Tone Measurement (MTON)

 

Voice coil displacement
(peak, bottom, dc component, Xmax)

3D-Distortion Measurement (DIS)
Large Signal Identification (LSI)
Large Signal Identification (LSI3)
Rocking Mode Analysis (RMA)
Transfer Function Measurement (TRF)

Dynamic Excursion Check and Control (DCX)
Motor+Suspension Check (MSC)
T/S Parameter Laser Fitting (TSX)

HI-2 distortion

3D-Distortion Measurement (DIS)

Hi-2 Weighted Harmonic Distortion (Hi-2)

Multi-tone distortion

Linear Parameter Measurement (LPM)
Multi-Tone Measurement (MTON)

 

Accelerated life test, power test
(durability, parameter variation, maximal input power)

Live Audio Analyzer (LAA)
Large Signal Identification (LSI)
Power Testing (PWT)

 

Voice coil temperature

3D-Distortion Measurement (DIS)
Live Audio Analyzer (LAA)
Large Signal Identification (LSI)
Power Testing (PWT)

 

Distortion in reproduced audio signal
(contribution of Bl(x), Cms(x), Le(x), Le(i))

Large Signal Identification (LSI)
Power Testing (PWT)
Rocking Mode Analysis (RMA)
Simulation-Auralization (SIM-AUR)

 

Auralization

Simulation-Auralization (SIM-AUR)

Sound Pressure Task (SPL-Monitoring)

Distributed mechanical parameters
(mechanical vibration scanned on radiator's surface)

Higher Modal Analysis (HMA)
Rocking Mode Analysis (RMA)
Scanning Vibrometer System (SCN)

 

Modal analysis (natural frequencies, shape of modal vibration, modal loss factor)

Higher Modal Analysis (HMA)
Rocking Mode Analysis (RMA) 
Scanning Vibrometer System (SCN)

 

Accumulated acceleration level (AAL)

Scanning Vibrometer System (SCN)

 

Decomposition into radial and circumferential mode

Rocking Mode Analysis (RMA)
Scanning Vibrometer System (SCN)

 

Rocking mode analysis

Rocking Mode Analysis (RMA)

Scanning Vibrometer System (SCN)

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