Electronic – Does multiple IMU increase accuracy

I have noticed some accellerometers and gyros to have a bit of a memory effect.

For example, you can place a accellerometer horizontal and null out the reading. I will stay close to zero but of course still drift a little. Now move it sideways and back again to the original position and the reading won't be zero anymore. The stronger and more sudden the movement, the more it seems to change the zero offset.

It is this unpredictable drift in the zero value that messes up inertial navigation over a longer time. Sometimes long is only a few seconds with MEMs gyros and accellerometers.

I did a sports head tracking device once, and even if you had the person hold still before starting a motion, the position would unusable after a couple of seconds. Fortunately that was long enough, and we designed the algorithm to use things like accelleration and angular rate directly instead of relying much on their integrals. This was with rather cheap MEMs units.

The issue is primarily with the sensors themselves. The MEMS devices just do not have exceptionally good performance characteristics. The readout electronics are noisy and do not have very good dynamic range. The biasing will also vary with voltage and temperature, manifesting as an offset that results in drift. It's a classic engineering/economics trade-off. The devices are very small, low power, and relatively easy to mass-produce. If you want a 'real' gyro, then you need to get a high-precision mechanical gyro, or fiber optic gyro or a ring laser gyro. However, these are high precision devices that require expensive precision components and time-consuming alignment and calibration. They are also quite large and consume a lot of power. They're perfect for a commercial or military airplane, missile, or rocket, but outside of that they are far too expensive. (Not to mention probably ITAR controlled)

There is really no way to improve the accuracy of an IMU aside from either using better inertial sensors, putting the whole shebang in a constant temperature oven, and/or adding data from other, non-inertial sensors, such as a magnetometer or a motion capture system. Of course this is presuming you are already using all of the standard IMU sensors (3x gyro and 3x accelerometer) with a good sensor fusion algorithm. Adding a second IMU will likely not help much as they are just as likely to drift in the same direction as they are to drift in opposite directions.