Optical Capture | Magnetic Capture | Motion Base | Other Methods

CAREN Base

OTHER METHODS

Even though optical and magnetic motion capture systems are the two most prominently used, there are several other systems available. Some systems are preferred under certaincircumstances.


Inertial devices
Inertial measurement includes such devices as accelerometers, gyros, and devices for measuring orientation or acceleration of moving vehicles. Accelerometers are devices for measuring the rate of change in velocity and can provide estimations of distance or be used to detect high forces. Much of the initial research, development and marketing in this area were for military applications.

Range finding devices
There are basic techniques for distance measurement using electromagnetic radiation. All are used in practice for distance measurement depending on the particular application.

These are:

  • Pulse Timing - Pulse timing involves measuring the round-trip time for a signal to be transmitted to a reflective surface and return. This is the principle used in Radar, DME for aircraft, LORAN, Satellite Altimetry, Airborne RADAR Altimetry, Lunar Laser Ranging etc. Some of the newer EDM instruments used by surveyors are also using pulse timing and accuracies of +/-5mm are possible
  • Phase Comparison - Phase difference involves the use of a carrier wave which may be modulated at different wavelengths. By measuring the difference in phase between the transmitted signal and the received signal after it has been reflected from the other end of the target, the distance can be determined as an integer number (unknown) of wavelengths plus a fraction of a wavelength which is known from the phase comparison.
  • Doppler Methods - Doppler techniques were used in the earlier satellite positioning systems. The received frequency of a low orbit satellite is compared with the actual transmitted signal as a function of time. The rate of change of frequency gives the slant range between the satellite and the observer while the instant when the two frequencies are the same gives the point of closest approach.

Force/torque, accelerometers, tactile:
Force measurement provides indications of magnitude and direction of forces for use in manipulation or locomotion. A variety of control schemes have been implemented in force controlled systems to allow smooth and accurate control in situations that would otherwise be precluded without such devices. A number of load cells and acceleration measuring devices exist.

MOTEK Medical offers motion capture services in the medical field for those who need to acquire motion capture data for fundamental research, applied research and clinical applications.

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