nyx_space/dynamics/guidance/
mod.rs

1/*
2    Nyx, blazing fast astrodynamics
3    Copyright (C) 2018-onwards Christopher Rabotin <christopher.rabotin@gmail.com>
4
5    This program is free software: you can redistribute it and/or modify
6    it under the terms of the GNU Affero General Public License as published
7    by the Free Software Foundation, either version 3 of the License, or
8    (at your option) any later version.
9
10    This program is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13    GNU Affero General Public License for more details.
14
15    You should have received a copy of the GNU Affero General Public License
16    along with this program.  If not, see <https://www.gnu.org/licenses/>.
17*/
18
19use crate::cosmic::{GuidanceMode, Orbit, Spacecraft, STD_GRAVITY};
20use crate::errors::{NyxError, StateError};
21use crate::linalg::Vector3;
22use anise::astro::PhysicsResult;
23use anise::errors::PhysicsError;
24use anise::math::rotation::DCM;
25use anise::prelude::Almanac;
26use serde::{Deserialize, Serialize};
27
28mod finiteburns;
29pub use finiteburns::FiniteBurns;
30
31mod mnvr;
32pub use mnvr::{Maneuver, MnvrRepr};
33
34mod ruggiero;
35pub use ruggiero::{Objective, Ruggiero, StateParameter};
36use snafu::Snafu;
37
38use std::fmt;
39use std::sync::Arc;
40
41/// Defines a thruster with a maximum isp and a maximum thrust.
42#[allow(non_snake_case)]
43#[derive(Copy, Clone, Debug, PartialEq, Serialize, Deserialize)]
44pub struct Thruster {
45    /// The thrust is to be provided in Newtons
46    pub thrust_N: f64,
47    /// The Isp is to be provided in seconds
48    pub isp_s: f64,
49}
50
51impl Thruster {
52    /// Returns the exhaust velocity v_e in meters per second
53    pub fn exhaust_velocity_m_s(&self) -> f64 {
54        self.isp_s * STD_GRAVITY
55    }
56}
57
58/// The `GuidanceLaw` trait handles guidance laws, optimizations, and other such methods for
59/// controlling the overall thrust direction when tied to a `BaseSpacecraft`. For delta V control,
60/// tie the DeltaVctrl to a MissionArc.
61pub trait GuidanceLaw: fmt::Display + Send + Sync {
62    /// Returns a unit vector corresponding to the thrust direction in the inertial frame.
63    fn direction(&self, osc_state: &Spacecraft) -> Result<Vector3<f64>, GuidanceError>;
64
65    /// Returns a number between [0;1] corresponding to the engine throttle level.
66    /// For example, 0 means coasting, i.e. no thrusting, and 1 means maximum thrusting.
67    fn throttle(&self, osc_state: &Spacecraft) -> Result<f64, GuidanceError>;
68
69    /// Updates the state of the BaseSpacecraft for the next maneuver, e.g. prepares the controller for the next maneuver
70    fn next(&self, next_state: &mut Spacecraft, almanac: Arc<Almanac>);
71
72    /// Returns whether this thrust control has been achieved, if it has an objective
73    fn achieved(&self, _osc_state: &Spacecraft) -> Result<bool, GuidanceError> {
74        Err(GuidanceError::NoGuidanceObjectiveDefined)
75    }
76}
77
78/// Converts the alpha (in-plane) and beta (out-of-plane) angles in the RCN frame to the unit vector in the RCN frame
79fn unit_vector_from_plane_angles(alpha: f64, beta: f64) -> Vector3<f64> {
80    Vector3::new(
81        alpha.sin() * beta.cos(),
82        alpha.cos() * beta.cos(),
83        beta.sin(),
84    )
85}
86
87/// Converts the provided unit vector into in-plane and out-of-plane angles in the RCN frame, returned in radians
88pub fn plane_angles_from_unit_vector(vhat: Vector3<f64>) -> (f64, f64) {
89    (vhat[1].atan2(vhat[0]), vhat[2].asin())
90}
91
92/// Converts the alpha (in-plane) and beta (out-of-plane) angles in the RCN frame to the unit vector in the RCN frame
93pub(crate) fn unit_vector_from_ra_dec(alpha: f64, delta: f64) -> Vector3<f64> {
94    Vector3::new(
95        delta.cos() * alpha.cos(),
96        delta.cos() * alpha.sin(),
97        delta.sin(),
98    )
99}
100
101/// Converts the provided unit vector into in-plane and out-of-plane angles in the RCN frame, returned in radians
102pub(crate) fn ra_dec_from_unit_vector(vhat: Vector3<f64>) -> (f64, f64) {
103    let alpha = vhat[1].atan2(vhat[0]);
104    let delta = vhat[2].asin();
105    (alpha, delta)
106}
107
108#[derive(Debug, PartialEq, Snafu)]
109pub enum GuidanceError {
110    #[snafu(display("No thruster attached to spacecraft"))]
111    NoThrustersDefined,
112    #[snafu(display("Throttle is not between 0.0 and 1.0: {ratio}"))]
113    ThrottleRatio { ratio: f64 },
114    #[snafu(display("Invalid finite burn control direction u = [{x}, {y}, {z}] => i-plane = {in_plane_deg} deg, Delta = {out_of_plane_deg} deg",))]
115    InvalidDirection {
116        x: f64,
117        y: f64,
118        z: f64,
119        in_plane_deg: f64,
120        out_of_plane_deg: f64,
121    },
122    #[snafu(display("Invalid finite burn control rate u = [{x}, {y}, {z}] => in-plane = {in_plane_deg_s} deg/s, out of plane = {out_of_plane_deg_s} deg/s",))]
123    InvalidRate {
124        x: f64,
125        y: f64,
126        z: f64,
127        in_plane_deg_s: f64,
128        out_of_plane_deg_s: f64,
129    },
130    #[snafu(display("Invalid finite burn control acceleration u = [{x}, {y}, {z}] => in-plane = {in_plane_deg_s2} deg/s^2, out of plane = {out_of_plane_deg_s2} deg/s^2",))]
131    InvalidAcceleration {
132        x: f64,
133        y: f64,
134        z: f64,
135        in_plane_deg_s2: f64,
136        out_of_plane_deg_s2: f64,
137    },
138    #[snafu(display("when {action} encountered {source}"))]
139    GuidancePhysicsError {
140        action: &'static str,
141        source: PhysicsError,
142    },
143    #[snafu(display(
144        "An objective based analysis or control was attempted, but no objective was defined"
145    ))]
146    NoGuidanceObjectiveDefined,
147    #[snafu(display("{param} is not a control variable in this guidance law"))]
148    InvalidControl { param: StateParameter },
149    #[snafu(display("guidance encountered {source}"))]
150    GuidState { source: StateError },
151}
152
153/// Local frame options, used notably for guidance laws.
154#[derive(Copy, Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
155pub enum LocalFrame {
156    Inertial,
157    RIC,
158    VNC,
159    RCN,
160}
161
162impl LocalFrame {
163    pub fn dcm_to_inertial(&self, state: Orbit) -> PhysicsResult<DCM> {
164        match self {
165            LocalFrame::Inertial => Ok(DCM::identity(
166                state.frame.orientation_id,
167                state.frame.orientation_id,
168            )),
169            LocalFrame::RIC => state.dcm_from_ric_to_inertial(),
170            LocalFrame::VNC => state.dcm_from_vnc_to_inertial(),
171            LocalFrame::RCN => state.dcm_from_rcn_to_inertial(),
172        }
173    }
174}
175
176#[test]
177fn ra_dec_from_vec() {
178    use std::f64::consts::{FRAC_PI_2, PI, TAU};
179    let mut delta = -FRAC_PI_2;
180    let mut alpha = 0.0;
181    loop {
182        loop {
183            let unit_v = unit_vector_from_ra_dec(alpha, delta);
184            let (alpha2, delta2) = ra_dec_from_unit_vector(unit_v);
185            assert!((alpha - alpha2).abs() < f64::EPSILON);
186            assert!((delta - delta2).abs() < f64::EPSILON);
187            alpha += TAU * 0.1; // Increment right ascension by one tenth of a circle
188            if alpha > PI {
189                alpha = 0.0;
190                break;
191            }
192        }
193        delta += TAU * 0.1; // Increment declination by one tenth of a circle
194        if delta > FRAC_PI_2 {
195            break;
196        }
197    }
198}
nyx_space/dynamics/guidance/mod.rs

nyx_space/dynamics/guidance/
mod.rs
