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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)

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

Linear Parameter Measurement (LPM)

Impedance Task (IMP)
Motor + Suspension Check (MSC)

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)

 

Motor + Suspension Check (MSC)

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

Large Signal Identification (LSI)
Power Testing (PWT)

 

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

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

Standard, Programmable System
Meta-Hearing-Technology (MHT)
Air Leak Detection (ALD)

Air leakage noise localization
(position of modulated noise source)

 

Air Leakage Localization Module

Sound power response

Scanning Vibrometer System(SCN)
Polar Far-Field Measurement (POL)
Transfer Function measurement (TRF)
Higher Modal Analysis (HMA)

 

Phase response
(minimal-phase, excess-phase)

Transfer Function Measurement (TRF)

 

Group time delay response
(total, minimal phase)

Transfer Function Measurement (TRF)

System task in Standard System

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

Transfer Function Measurement (TRF)

 

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

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

Basic, Standard, Programmable System

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)

 

Sinusoidal burst measurement

Transfer Function Measurement (TRF)

 

Thermal and nonlinear compression
(fundamental, harmonics versus voltage)

3D-Distortion Measurement (DIS)

 

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

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

 

HI-2 distortion

3D-Distortion Measurement (DIS)

 

Multi-tone distortion

Linear Parameter Measurement (LPM)

Multi-tone task in Standard System

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

Large Signal Identification (LSI)
Power Testing (PWT)

 

Voice coil temperature

3D-Distortion Measurement (DIS)
Large Signal Identification (LSI)
Power Testing (PWT)

 

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

Auralization Module (AUR)
Large Signal Identification (LSI)
Power Testing (PWT)
Rocking Mode Analysis (RMA)

 

Auralization

Auralization Module (AUR)

 

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

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

 

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

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

 

Accumulated acceleration level (AAL)

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

 

Decomposition into radial and circumferential mode
(indicating rocking mode)

Scanning Vibrometer System (SCN)

 

Rocking mode analysisScanning Vibrometer System (SCN)
Higher Modal Analysis (HMA)

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