Talk:Inertial measurement unit

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This page is pretty much redundant with Inertial guidance system, which is more detailed

Why? Inertial Measurement Unit is a part of the Inertial guidance system. I believe it is the hardware that actually performs the measuring i.e. the gyroscopes and the accelerometers. However, that is not clearly explained in this article. I don't know enough about it but maybe someone else feels up to the task?

from a user without a wikipedia log: To my experience, the term IMU is widely used to refer to a box, where: 3 accelerometers are placed such that their measuring axis are orthogonal to each other, measuring the so called specific forces (inertial acceleration - gravity); 3 gyros are placed such that their measuring axis are orthogonal to each other, measuring the rotation rates; one or more temperature sensors are included, maybe already incorporated in each acc or gyro, or as an additional sensor which data will be used to calibrate the raw data from the other sensors. To achieve superior accuracy, the box may be designed such that the temperature is controlled and kept constant, and the walls of the box are made of materials that minimize electromagnetic interference. If the output signals are analog, further considerations must be taken about the cables and the A/D card. If the output data is already in digital format, time delays become the major concern that should be carefully modelled. The data provided by an IMU box is all you need to perform dead-reckoning. It's not said on the article, but perhaps the first use of such box was in a ship, and still today almost every ship has one. Satellites have one also. Almost anything that must somehow use some electronics to know its acceleration, velocity and/or attitude, have an IMU. Nowadays you can buy an out-of-the-shelf MEMS based IMU for something like 2000 eur, and that's a good one already for many purposes. If we work a bit the kinematic equations and let it run on a Kalman filter, the data from an IMU can be transformed into an ARS system (Attitude Reference System). This means roll and pitch. The dead-reckon integration of the rate gyros will cause drifting errors, but the observation of the gravity vector by the accs serves as an external observation of the local vertical, which corrects for these drifting errors. In dynamic environments like in a jet fighter, the gravity will be masked by the aircraft's body accelerations, thus normally in these cases the IMU is coupled together with the GPS or other sensors. This brings us a bit closer to a Navigation and Guidance System and a bit away from the IMU. Maybe this is why a lot of engineers don't really make a distintion.

well, perhaps some good english writer and more baldy than me, will make this official... feel free


- Reply on your text: An INS and an IMU are different products. IMU's are also used for human motion tracking (for rehabilitation, animation and Virtual Reality for example). An INS is used for machine motion and IMU's are indeed part of INS's, but the use of IMU's is not limited to this appliction.

I revamped the article to address all these issues. Also, to those who posted to the former "external links" section, I've removed that section because it only had corporate websites listed and was becoming a kind of free ad space. Generally, we should probably limit external links to scientific information resources. 20:26, 4 September 2007 (UTC)


[edit] Accuracy of measurements

How much accuracy can you expect from an IMU? --Singularitarian (talk) 18:18, 23 May 2008 (UTC)