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Steering Trapezoidal Mechanism

The steering of the front wheels can be achived by a simple trapeizoidal mechanism, with following geometry:

Trapeizoidal steering mechanism

with:

  • w: front wheel track
  • d: mechanism lever arm
  • β: trapezoidal angle

This mechanism allows to get close to the Akerman steering geometry. However, it is not perfect and may deviate significantly from the Akerman steering geometry.

To reduce the error between Akerman geometry and the trapezoidal aprroximation, an optimization tool has been writen in python. This script computes the steering angles of the inner wheel δ_i ; and the outter wheel angle δ_o and minimizes the RMS error for a give range of:

  • steering angles
  • mechanism lever arm d
  • trapeizoidal angle β

The script can be downloaded here

The optimal trapeizoidal mechanism for the current version of eVECTORS is:

  • Optimal d: 0.100000
  • Optimal beta: 28.251086 degrees (0.493074 radians)
  • Minimum angle RMS error between Akerman and trapeizoidal mechanism: 1.412828e-01 [deg]

The difference between Akerman geometry and trapezoidal steering angles is shown in following figure.

Akerman and optimized trapezoidal steering angle, and error