wiki/ InertialMeasurementUnit

PSAS Inertial Measurement Units (IMUs)

See also our sensor comparison chart

We've built two IMUs so far. The first is almost not worth mentioning. The second is great, but represents what happens when you have to build something really complicated really quickly. We can't WAIT to do the third generation IMU - slowly and carefully ;)

LV1 IMU

First Flight April 11, 1999
Accelerometers 3x Analog Devices ADXL50
Gyroscopes 3x Tokin CG-16DO ceramic rate gyroscopes
Calibration No calibration except initial values before launch
Bandwidth Sensors bandwidth limited to 500Hz (A) and 100Hz (G) Sensors sampled at 1.00KHz
DSP Data low pass filtered to 12Hz for transmission down 2.4kbps downlink
Final data format Raw data values of X,Y,Z acceleration and a,b,g angular velocities

LV1b IMU

First Flight Spring 2000
Accelerometers Analog Devices ADXL202 and ADXL 250
Gyroscopes 3x Tokin CG-16DO ceramic rate gyroscopes
Calibration Simple 1g and constant rotation calibrations
Bandwidth Sensors bandwidth limited to 1kHz (A) and 100Hz (G) Sensors sampled at 2.50KHz (A) and 833Hz (G)
DSP Data low-pass filtered to 100Hz for position calculation
Final data format X,Y,Z,a,b,q position and attitude values

Here are a few pictures of the IMU, which was meant to mount directly with the Lv1b Flight computer:

Back_Oblique_IMU_2.thumb.jpg Oblique_Green_Front_IMU.thumb.jpg

Current Tasks:

"Q" acceleration axis

In our current IMU we make some redundant acceleration measurements. We want to use the extra data to refine our estimates and increase sensor reliability. Here is a first cut at integrating the x, y, and "q" axis accelerometer data.

Raw Data


Inertial Sensors

Our current list of inertial sensors, with our own incomprehensable comments:

Various Commercial 6DOF IMUs:

Design files: