Automotive project to determine road gradient during braking

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Discussion Overview

The discussion revolves around determining the gradient of a road during a braking event using Inertial Measurement Units (IMUs), specifically accelerometers and gyroscopes, alongside wheel speed inputs. The focus is on the practical application of these sensors in automotive projects.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Tim seeks suggestions on using IMUs to determine road gradient during braking, noting the availability of wheel speed inputs for calculating deceleration.
  • One participant questions the implications of constant wheel speed while measuring acceleration, prompting a discussion on potential causes and how to distinguish them.
  • Another participant asks if the assumption is made that wheels do not slip during acceleration, suggesting that if this assumption holds, sufficient information may be available to analyze the situation.
  • Tim confirms the assumption of no wheel slip but raises concerns about the potential for skidding during heavy braking tests, questioning how race cars manage this issue, hinting at the use of GPS.
  • Tim reiterates the assumption of no wheel slip and requests more practical advice, specifically mentioning the need for a gyro and accelerometer.

Areas of Agreement / Disagreement

Participants generally agree on the assumption of no wheel slip, but there are concerns about the implications of this assumption during heavy braking. The discussion includes multiple viewpoints on the practicality of using IMUs and the challenges posed by skidding.

Contextual Notes

The discussion does not resolve the uncertainties regarding the effects of wheel slip during braking and the specific requirements for sensor integration in the project.

Tim Steer
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Hello Forum,

Does anybody have suggestions as to how we can use IMU's (accelerometers and gyros) to determine the gradient of a road during a braking event. We have wheel speed inputs so can calculate decelerations independently from the IMU.

Thank You

Tim
 
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If wheel speed is constant but acceleration is being measured what are the possible causes and how could you distinguish them?
 
Tim Steer said:
We have wheel speed inputs so can calculate decelerations independently from the IMU.
Are you assuming the wheels don't slip during the acceleration? If yes then you should have enough information. Draw the vector diagram for the accelerations.
 
A.T. said:
Are you assuming the wheels don't slip during the acceleration?
Yes, like most car speedos do. Though if it's a heavy braking test then skidding is likely so it maybe a problem.
I'm not sure how race cars get around this? GPS?
 
Yes the assumption is no wheel slip. Can anybody add anything more practical like, we need a gyro and accelerometer ?
 

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