Field Distortion Compensation Algorithm

If the LPMS is operated in an environment with a partially distorted (non-homogeneous) earth magnetic field, there is the possibility of the orientation readings becoming inaccurate due to invalid data from the magnetometer unit. To prevent this we have extended our sensor fusion algorithm to detect such field distortion and automatically switch to operation without magnetometer. The switching between the two states happens seamlessly (without orientation jump) and, if the exposure to the distorted magnetic field happens for a limited amount of time, without any major orientation drift.

Please see the video below for a demonstration of the improved filter. An iron plate is used to distort the magnetic field. As soon as the sensor gets close to the metal surface the magnetic field vector starts changing direction deliberately. The color of the cube on the monitor turns red in case of the detection of a distorted magnetic field.

Ask Slashdot

Lin, Professor Takanishi and me recently had quite a lively discussion about the question if and to which degree we should open-source the company’s motion analysis software. On the one hand I strongly voted for open-sourcing everything, to quickly make our company known and to support the open-source community. Lin and Prof. Takanishi on the other hand were worried about competitors re-using our code for their own products without giving us proper credits (and therefore violating the GPL). Obviously both sides have their pros and cons, so I thought it might be nice to ask that question to the community on Slashdot.

Today the questions has been published. Check here to read the comments.

Better Batteries

So far we used quite a small battery (80 mAh) to power the LPMS. This worked quite well for some time, but in the end we realized that continuous runtimes of about 1h are just not enough to do practical measurements. We therefore started experimenting with batteries with higher capacity. As you can see in the image below, we were able to prolong runtimes quite a bit, with luckily not having to compromise on size and weight of the sensor too much.

We are not quite ready release the complete specifications of these new types, but basically they will be energy optimized also on the software side and the battery will be exchangeable, so that the user can decide which size he prefers. Also for longer measurements, it might be handy to have a few spare batteries. We will sell additional batteries separately at a decent price.

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