Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Steering angle for Autonomous vehicle

  1. May 2, 2016 #1
    Dear All,
    Hello,
    I'm studying electronics engineering and I'm new in vehicle dynamics,
    Recently, I make an autonomous vehicle for my final project. In order to control steering angle of vehicle, I have difficulty to measure the steering angle based on curvature road and vehicle velocity.
    Anybody can help me, how to calculate steering angle when wheelbase, curvature road and vehicle are already known?

    Thanks
     
  2. jcsd
  3. May 2, 2016 #2

    billy_joule

    User Avatar
    Science Advisor

  4. May 2, 2016 #3
    Thanks @billy_joule
    I already read that kind of steering tutorial.
    am I not wrong steering angle (δ) can be determined by δ=L/R
    where
    L = Wheelbase
    R= Radius of curvature
    But there isn't relation with the speed.
    is the steering angle is same both at high or low speed?
     
  5. May 2, 2016 #4

    billy_joule

    User Avatar
    Science Advisor

    Generally, yes.
     
  6. May 2, 2016 #5

    jack action

    User Avatar
    Science Advisor
    Gold Member

    Steering angle usually varies with lateral acceleration ([itex]a_y[/itex]), which is related to speed ([itex]v[/itex]) and radius of curvature ([itex]R[/itex]) with the following equation: [itex]a_y = \frac{v^2}{R}[/itex].

    The steering angle ([itex]\delta[/itex]), lateral acceleration (related to standard gravity [itex]g[/itex]) and wheelbase ([itex]L[/itex]) are related the following way:
    [tex]\delta = \frac{L}{R} + K_{us}\frac{a_y}{g}[/tex]
    Where [itex]K_{us}[/itex] is the understeer coefficient of the vehicle. If [itex]K_{us} = 0[/itex] then the vehicle is said to be «neutral steer» (steering angle independent of lateral acceleration); if [itex]K_{us} < 0[/itex] then the vehicle is said to be «oversteer».

    Theoretically, based on the bicycle model, [itex]K_{us} = \frac{W_f}{C_f} - \frac{W_r}{C_r}[/itex], where [itex]W[/itex] is the normal weight acting on a tire and [itex]C[/itex] is the cornering stiffness of the tire ([itex]f[/itex] & [itex]r[/itex] subscripts are for «front» and «rear»). The cornering stiffness relates lateral tire force to slip angle.

    In practice, [itex]K_{us}[/itex] for a given vehicle varies with lateral acceleration. The way to determine [itex]K_{us}[/itex] for a given vehicle following a path is by plotting the variable [itex]\frac{a_y}{g}[/itex] with respect to [itex]\frac{L}{R} - \delta[/itex] and evaluate:
    [tex]\frac{d\left(\frac{a_y}{g}\right)}{d\left(\frac{L}{R} - \delta\right)} = - \frac{1}{K_{us}}[/tex]
    From measurements taken within the vehicle, [itex]R = \frac{v}{\Omega_z}[/itex]. Where [itex]\Omega_z[/itex]is the yaw velocity of the vehicle.

    Ref.: Theory of ground vehicles, 2nd ed. by J.Y. Wong
    kus-vs-ay.jpg find-kus.jpg
     
  7. May 3, 2016 #6
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Steering angle for Autonomous vehicle
  1. Steering angle (Replies: 6)

Loading...