The discussion revolves around estimating the pitch rate and roll rate of a vehicle using data from three axial accelerometers. Participants explore methodologies for measuring these rates based on the placement of accelerometers and the challenges posed by vehicle dynamics and alignment issues.
Participants do not reach a consensus on the best methodology for measuring pitch and roll rates, and multiple competing views on the placement and alignment of accelerometers remain. The discussion includes various proposed approaches and uncertainties regarding the effectiveness of these methods.
Limitations include the dependence on the accurate placement and alignment of accelerometers, the need for knowledge of the vehicle's dimensions, and the challenges in separating pitch from roll in dynamic conditions.
serbring said:I have to estimate the pitch rate and the roll rate of a vehicle, from measured accelerations. I have many three axial accelerometers. How can i accomplish it?
GRDixon said:For pitch, you might place an acc. in the nose, at the center of mass, and in the tail, and analyze on that basis. Similarly, for roll an acc. in each wing tip and one at the cm might be worth considering. Of course you need your aircraft's dimensions in order to translate linear accelerations into angular velocities, etc.
Jeff Reid said:If these are "axial" accelerometers, than placement doesn't matter, as long as you get the "axis" of the accelertometers aligned with the desired axis, pitch, roll, yaw. You wouldn't need to calculate anything, just convert the outputs of the "axial" accelerometers into a rate such as radians / second. Radio control helicopter generally use silicon based "gyros" which include axial accelerometers in the form of a vibrating component that varies electrical output based on rate of rotation.
If the 3 accelerometers are mutually orthogonal, then a simple mathematical coordinate system rotation of axes (Euler angles)serbring said:thank you. I have understand. A question, if i can't align the accelerometers with the desired axis, how can measure the pitch rate? I ask you this only for better comprehension of the vehicle dynamic
If you can't align them, but you have 3, then you can do a conversion as mentioned in previous post, but you'd need to accurately know the axis angle offsets, which would probably be just as difficult as aligning them.serbring said:If i can't align the accelerometers with the desired axis, how can measure the pitch rate?
Jeff Reid said:If you can't align them, but you have 3, then you can do a conversion as mentioned in previous post, but you'd need to accurately know the axis angle offsets, which would probably be just as difficult as aligning them.
If you can setup or buy a 3 orthogonal axis cluster, then you could mount the cluster, then accelerate and brake, adjusting the cluster until you just get a readout for pitch. Yaw and roll would be more difficult to separate, perhaps pushing on the car from the side. You could use a level to make sure the cluster was vertically and horizontally aligned, but the yaw axis would still be an issue.
faisalzia84 said:I need some information from you guys.
I have readings from acceleration sensors i.e. Acceleration along X-axis, Y-axis and Z-axis.
I want to find the Pitch and roll angle from the above data. Is it possible to find the Pitch and roll data from acceleration data.
Regards
waiting for your kind and early reply
naeemKhan said:Dear
Actually this book is not frequently available. Can you upload those equation which help for combine angular and translational accelerations?