aerso

aerso is a Rust library for kinematics with helpers for aerodynamic forces.

The core kinematics code is in src/kinematics.rs. The integration is performed using a 4th order Runge-Kutta process. At present, a fixed timestep is used.

The kinematics code is then wrapped in the AeroBody interface which adds options for wind and density models to enable modelling the atmosphere.

The final layer of helpers comes in the AffectedBody interface, which adds the option to attach AeroEffects to the body. These provide a wrapper for forces and torques that are generated by a combination of the vehicle airstate, body-axis rates and a generic input state.

Example

The full code for the example can be found in examples/demo.rs.

The first step is to create a Body which represents the base kinematic properties:

let initial_position = Vector3::zeros();
let initial_velocity = Vector3::zeros();
let initial_attitude = UnitQuaternion::from_euler_angles(0.0,0.0,0.0);
let initial_rates = Vector3::zeros();

let k_body = Body::new(
        1.0,                 // Mass (kg)
        Matrix3::identity(), // Inertia matrix/tensor
        initial_position,
        initial_velocity,
        initial_attitude,
        initial_rates
        );

This is then wrapped in an AeroBody, where wind and density models can be attached:

let wind = Vector3::new(0.0,-1.0,0.0);
let wind_model = ConstantWind::new(wind);

let a_body = AeroBody::with_wind_model(k_body,wind_model);

Next any AeroEffects can be defined:

struct Lift;
impl<I> AeroEffect<I> for Lift {
    fn get_effect(&self, airstate: AirState, _rates: Vector3, _inputstate: &I) -> (Force,Torque) {
        const S: f64 = 0.5;
        const AR: f64 = 5.0;
        
        const C_L_ALPHA: f64 = 2.0*std::f64::consts::PI;
        const C_L0: f64 = 0.1;
        
        let c_l = C_L_ALPHA * (AR/(AR+2.0)) * airstate.alpha + C_L0;
        let lift = airstate.q * S * c_l;
        
        (Force::body(0.0,0.0,-lift),Torque::body(0.0,0.0,0.0))
    }
}

Finally, the effects are attached via the AffectedBody:

let mut vehicle = AffectedBody {
    body: a_body,
    effectors: vec![Box::new(Lift)],
    };

Then propogating the system is just calling step:

let delta_t = 0.01;
let mut time = 0.0;
while time < 100.0 {
    vehicle.step(delta_t, &[200.0]);
    }