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Fix acceleration reading from IMU #10

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merged 3 commits into from
Nov 5, 2024
Merged

Fix acceleration reading from IMU #10

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64ac9da
fix acceleration from read_imu for euler method
makeecat Nov 5, 2024
f34ebc3
add acceleration update in rk4
makeecat Nov 5, 2024
fe1ab59
fix state_derivate test
makeecat Nov 5, 2024
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20 changes: 10 additions & 10 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,8 @@ pub struct Quadrotor {
pub position: Vector3<f32>,
/// Current velocity of the quadrotor
pub velocity: Vector3<f32>,
/// Current acceleration of the quadrotor
pub acceleration: Vector3<f32>,
/// Current orientation of the quadrotor
pub orientation: UnitQuaternion<f32>,
/// Current angular velocity of the quadrotor
Expand Down Expand Up @@ -117,6 +119,7 @@ impl Quadrotor {
Ok(Self {
position: Vector3::zeros(),
velocity: Vector3::zeros(),
acceleration: Vector3::zeros(),
orientation: UnitQuaternion::identity(),
angular_velocity: Vector3::zeros(),
mass,
Expand Down Expand Up @@ -151,8 +154,8 @@ impl Quadrotor {
let gravity_force = Vector3::new(0.0, 0.0, -self.mass * self.gravity);
let drag_force = -self.drag_coefficient * self.velocity.norm() * self.velocity;
let thrust_world = self.orientation * Vector3::new(0.0, 0.0, control_thrust);
let acceleration = (thrust_world + gravity_force + drag_force) / self.mass;
self.velocity += acceleration * self.time_step;
self.acceleration = (thrust_world + gravity_force + drag_force) / self.mass;
self.velocity += self.acceleration * self.time_step;
self.position += self.velocity * self.time_step;
let inertia_angular_velocity = self.inertia_matrix * self.angular_velocity;
let gyroscopic_torque = self.angular_velocity.cross(&inertia_angular_velocity);
Expand Down Expand Up @@ -271,7 +274,7 @@ impl Quadrotor {
/// use nalgebra::UnitQuaternion;
/// let (time_step, mass, gravity, drag_coefficient) = (0.01, 1.3, 9.81, 0.01);
/// let inertia_matrix = [0.0347563, 0.0, 0.0, 0.0, 0.0458929, 0.0, 0.0, 0.0, 0.0977];
/// let quadrotor = Quadrotor::new(time_step, mass, gravity, drag_coefficient, inertia_matrix).unwrap();
/// let mut quadrotor = Quadrotor::new(time_step, mass, gravity, drag_coefficient, inertia_matrix).unwrap();
/// let state = [
/// 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
/// ];
Expand All @@ -280,7 +283,7 @@ impl Quadrotor {
/// let derivative = quadrotor.state_derivative(&state, control_thrust, &control_torque);
/// ```
pub fn state_derivative(
&self,
&mut self,
state: &[f32],
control_thrust: f32,
control_torque: &Vector3<f32>,
Expand All @@ -298,15 +301,15 @@ impl Quadrotor {
let gravity_force = Vector3::new(0.0, 0.0, -self.mass * self.gravity);
let drag_force = -self.drag_coefficient * velocity.norm() * velocity;
let thrust_world = orientation * Vector3::new(0.0, 0.0, control_thrust);
let acceleration = (thrust_world + gravity_force + drag_force) / self.mass;
self.acceleration = (thrust_world + gravity_force + drag_force) / self.mass;

let inertia_angular_velocity = self.inertia_matrix * angular_velocity;
let gyroscopic_torque = angular_velocity.cross(&inertia_angular_velocity);
let angular_acceleration = self.inertia_matrix_inv * (control_torque - gyroscopic_torque);

let mut derivative = [0.0; 13];
derivative[0..3].copy_from_slice(velocity.as_slice());
derivative[3..6].copy_from_slice(acceleration.as_slice());
derivative[3..6].copy_from_slice(self.acceleration.as_slice());
derivative[6..10].copy_from_slice(q_dot.coords.as_slice());
derivative[10..13].copy_from_slice(angular_acceleration.as_slice());
derivative
Expand All @@ -327,10 +330,7 @@ impl Quadrotor {
/// let (true_acceleration, true_angular_velocity) = quadrotor.read_imu().unwrap();
/// ```
pub fn read_imu(&self) -> Result<(Vector3<f32>, Vector3<f32>), SimulationError> {
let gravity_world = Vector3::new(0.0, 0.0, self.gravity);
let true_acceleration =
self.orientation.inverse() * (self.velocity / self.time_step - gravity_world);
Ok((true_acceleration, self.angular_velocity))
Ok((self.acceleration, self.angular_velocity))
}
}
/// Represents an Inertial Measurement Unit (IMU) with bias and noise characteristics
Expand Down