# vehicle dynamics code problems

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Patrick Bradford on 30 Jul 2019
says t isn't defined and gives me a hard time. Where t is the time component of the function.
%%VEHICLE_MODEL IDNLGREY model file
%%function [dx,y] = VEHICLE_MODEL(t, x, u, m, a, b, Cy, varargin)
function [dx,y] = VEHICLE_MODEL_test(t, x, u, m, a, b, Cy, varargin)
%% prompt = 'Please enter the intial start time. ';
%% t = input(prompt);
%% prompt = 'Please enter the Vehicle Mass in Kg ';
%% m = input(prompt);
% function parameters:
% t: the current time
% x: the state vector at time t
% u: the input vector at time t
% m: mass of the vehicle [kg]
% a: distance from front axle to COG [m]
% b: distance from rear axle to COG [m]
% Cy: lateral tire stiffness (Axis skew stiffness) [N/rad]
% varargin: optional inputs to the model file
J = m * 0.25 *(a+b)^2; % moment of inertia [kg*m^2]
Fyf = Cy*(u(1)-atan((x(4)+a*x(2))./x(3))); % lateral tire force on front tires [N]
Fyr = -Cy*atan((x(4)-b*x(2))./x(3)); % lateral tire force on rear tires [N]
vx_inertial = x(3).*cos(x(1))-x(4).*sin(x(1)); % longitudinal velocity in inertial reference frame [m/s]
vy_inertial = x(3).*sin(x(1))+x(4).*cos(x(1)); % lateral velocity in inertial reference frame [m/s]
% state equations.
dx = [x(2); ... % yaw angle velocity [rad/s]
1/J*(a*(u(2)*sin(u(1))+Fyf*cos(u(1)))-b*Fyr); ... % yaw angle accel. [rad/s^2]
1/m*(u(2)*cos(u(1))-Fyf*sin(u(1))+u(3))+x(4).*x(2); ... % longitudinal accel. in body reference frame [m/s^2]
1/m*(u(2)*sin(u(1))+Fyf*cos(u(1))+Fyr)-x(3).*x(2); ... % lateral accel. in body reference frame [m/s^2]
vx_inertial; ... % longitudinal velocity in inertial reference frame [m/s]
vy_inertial ... % lateral velocity in inertial reference frame [m/s]
];
% output equations.
y = [x(1); ... % yaw angle [rad]
x(2); ... % yaw angle velocity [rad/s]
x(3); ... % longitudinal velocity in body reference frame [m/s]
x(4); ... % lateral velocity in body reference frame [m/s]
x(5); ... % longitudinal position in inertial reference frame [m]
x(6); ... % lateral position in inertial reference frame [m]
vx_inertial; ... % longitudinal velocity in inertial reference frame [m/s]
vy_inertial; ... % lateral velocity in inertial reference frame [m/s]
Fyf; ... % lateral tire force on front tires [N]
Fyr ... % lateral tire force on rear tires [N]
];
end