Sixense Wireless Motion Tracking System!

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cybereality
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Re: Sixense Wireless Motion Tracking System!

Post by cybereality »

The Hydra was supposed to track down to 1mm, so that would make the STEM less precise.

However if they did this to increase the range, I think it may have been a good trade-off.

EdZ
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Re: Sixense Wireless Motion Tracking System!

Post by EdZ »

Depending on whether someone has patented it already, signal strength (and receiver amplifier gain) could be optimised depending on the distance between the STEM and the basestation. Replace the 'quiet' emission phase (or add another phase) with all 3 field coils active, and measure the total received input for each STEM (could also be done by averaging each of the 3 orthogonal phases, I guess). Then change the coil emission strength and update each STEM with a new amplifier gain to keep the largest dynamic range possible. This way, if all your STEMs are clustered close to one another (i.e. attached to one person, rather than to multiple people) increasing the distance from the basestation would suffer a smaller drop in spatial resolution.
They're probably already doing that, though.

The 'whole hog' version would be to keep received power constant with a fast closed-loop and measure position solely from the output power of the base station, but this requires three transmission phases for each receiver, so the update rate would suffer (might be compensated for by simpler and more sensitive receiver circuitry allowing shorter phases).

Krenzo
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Re: Sixense Wireless Motion Tracking System!

Post by Krenzo »

They already vary receiver gain in the Hydra to maximize dynamic range. I'm not sure what you're getting at by wanting all field coils active at once. That would defeat the ability to determine rotation.

EdZ
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Re: Sixense Wireless Motion Tracking System!

Post by EdZ »

The 'all field' pulse was to provide a uniform field for ranging. Averaging each orthogonal field may have some temporal shift issues when moving at high speeds (probably not a problem), but using a uniform field would increase range sensitivity by allowing all three orthogonal coils to be combined for measurement.

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V8Griff
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Re: Sixense Wireless Motion Tracking System!

Post by V8Griff »

EdZ wrote:Depending on whether someone has patented it already, signal strength (and receiver amplifier gain) could be optimised depending on the distance between the STEM and the basestation. Replace the 'quiet' emission phase (or add another phase) with all 3 field coils active, and measure the total received input for each STEM (could also be done by averaging each of the 3 orthogonal phases, I guess). Then change the coil emission strength and update each STEM with a new amplifier gain to keep the largest dynamic range possible. This way, if all your STEMs are clustered close to one another (i.e. attached to one person, rather than to multiple people) increasing the distance from the basestation would suffer a smaller drop in spatial resolution.
They're probably already doing that, though.

The 'whole hog' version would be to keep received power constant with a fast closed-loop and measure position solely from the output power of the base station, but this requires three transmission phases for each receiver, so the update rate would suffer (might be compensated for by simpler and more sensitive receiver circuitry allowing shorter phases).

You'll need to check out Patents granted to both Polhemus and Ascension Tech who have been the main players in the magnetic tracker space for around 40 or so years.I suspect that the original Hydra Razer and now the STEM technology are using the older lapsed patents granted back in the '80s and early '90s which is why they are limited to what they can do to improve the systems as they may well be prevented from using the methods you're suggesting.

By it's nature magnetic tracking is limited by the size of the magnetic field the base station can generate, hence the huge cube used in Ascension's now discontinued 'Flock of Birds' product.

o1113199
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Re: Sixense Wireless Motion Tracking System!

Post by o1113199 »

En: If your Razer Hydra starts spinning crazily and their location is confused, then the power contacts of the coils in the base station have oxidized. You need to disassemble the base station, remove the circuit, disconnect the red removable contacts and scratch the contacts themselves with a needle or solder the contacts directly to the board, then everything becomes as before. The controllers are old and these contacts have oxidized.

Ru: Если ваши Razer Hydra начинаются безумно вращаться и их местоположение спутанное, то контакты питания катушек в базовой станции окислились. Вам нужно разобрать базовую станцию, снять схему, отключить красные съемные контакты и поцарапать сами контакты иголкой или припаять контакты напрямую к плате, тогда всё становится как раньше. Контроллеры старые и эти контакты окислились.

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