Prototyping Body Tracking with IMUs

Remember our article on Body Tracking with 5 Tags ? Well decided to go further and test something new, something requiring quite more development, but that could become an extension to our Tags !

I am talking body tracking with IMU ! IMU stands for Inertial Motion Unit, those are sensors containing accelerometer, gyroscope and magnetometer. There is one IMU in each Tag, we mostly use them to get the Tag orientation and linear acceleration.

But today we tried to connect external IMU to the Tag, the objective is to be able to put those IMUs on different parts of the body. It could be used to do a full body tracking suit, but also hand and finger tracking. I love that last application as gloves are great for natural interactions.

In this test we are trying to read data for 4 to 6 IMUs. We discovered a limitation : the communication speed with the sensors is too slow and therefore we quickly max out the communication bus. With 4 IMUs we can retrieve orientation at 40 FPS, 5 IMUs – 30FPS and 6 IMUs – 20FPS.

This is a limitation on the Tag V1 and V2 but we are already working on a Bluetooth version (V3) that will solve this problem by changing the communication protocol with the IMU for one 17x faster. We should therefore be able to read from at least 40 IMUS at 60FPS ! I think it should be enough 😉

Note that this future version is only on prototyping, we still have a lot to work on before being able to release it.

2 Comments

  1. Han Ooi

    Are you building Tag V3 based on the Nordic SoC? Looks like your I2C bus is saturating. I presume Tag V3 will be based on SPI? Put me on the list for the new V3 Tag.

  2. JulesThuillier

    You are right on both points 🙂

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