Calculation of vehicle pitch rate and roll rate from acceleration

In summary: You can find the pitch and roll data from the acceleration data by measuring the pitch and roll angles.
  • #1
serbring
269
2
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?
 
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  • #2
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?

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.
 
  • #3
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.

i have to measuring these quantities in a vehicle for measuring the roll rate and pitch rate inducted from the road roughness. Moreover i don't know where the centre of mass is placed, and also it isn't possibile to place accelerometer in that point. Does your methodology work the same one?
 
  • #4
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.
 
  • #5
For an accelerating automobile, the torque in the propeller shaft (into the differential) creates an axial pitch (torque). For a propeller plane, the prop torque (power/radians per sec) may create a pitch also.
Bob S
 
  • #6
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.

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
 
  • #7
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 the 3 accelerometers are mutually orthogonal, then a simple mathematical coordinate system rotation of axes (Euler angles)
http://en.wikipedia.org/wiki/Euler_angles
will align the accelerometer readout with the vehicle axes.
Bob S
 
  • #8
serbring said:
If i can't align the accelerometers with the desired axis, how can measure the pitch rate?
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.
 
  • #9
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.

i don't understand how i can separate the pitch from roll, could you explain me better, please?
 
  • #10
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 accleration data.

Regards
waiting for your kind and early reply
 
  • #11
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 accleration data.

Regards
waiting for your kind and early reply

Try to take a look at pag 193 of this book.
http://elib.tu-darmstadt.de/tocs/209699132.pdf

You can read it from google books.
 
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  • #12
Dear

Actually this book is not frequently available. Can you upload those equation which help for combine angular and translational accelerations?
 
  • #13

1. How is vehicle pitch rate and roll rate calculated from acceleration?

The vehicle pitch rate and roll rate can be calculated using the vehicle's acceleration data, which can be collected using various sensors such as accelerometers and gyroscopes. By integrating the acceleration data over time, the pitch rate and roll rate can be determined.

2. What factors can affect the accuracy of calculating vehicle pitch rate and roll rate from acceleration?

The accuracy of calculating vehicle pitch rate and roll rate from acceleration can be affected by various factors such as the quality and calibration of the sensors, external forces like wind or road conditions, and the vehicle's design and mechanics. It is important to consider and account for these factors when analyzing the data.

3. Can vehicle pitch rate and roll rate be calculated in real-time?

Yes, vehicle pitch rate and roll rate can be calculated in real-time by continuously collecting and processing acceleration data. This can be useful for monitoring and controlling the vehicle's stability and handling.

4. How can vehicle pitch rate and roll rate be used in vehicle dynamics analysis?

Vehicle pitch rate and roll rate are important parameters in vehicle dynamics analysis as they provide information about the vehicle's movement and stability. This data can be used to evaluate the vehicle's handling, suspension performance, and overall driving dynamics.

5. Are there any limitations to calculating vehicle pitch rate and roll rate from acceleration?

While calculating vehicle pitch rate and roll rate from acceleration is a useful tool, there are limitations to its accuracy. External factors and sensor errors can affect the results, and it is important to consider these limitations when interpreting the data. It is also recommended to use other methods, such as vehicle simulation software, to validate the results.

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