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[wpimath] LinearSystemId: Fix docs, move C++ impls out of header (#4388)

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- Fix inaccuracies and inconsistencies in Java & C++ LinearSystemId documentation.
- Move LinearSystemId function definitions to LinearSystemId.cpp
This commit is contained in:
CarloWoolsey
2022-08-31 09:12:48 -07:00
committed by GitHub
parent d22ff8a158
commit 97c15af238
3 changed files with 333 additions and 301 deletions
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193
wpimath/src/main/native/cpp/system/plant/LinearSystemId.cpp Normal file
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// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
#include "frc/system/plant/LinearSystemId.h"
using namespace frc;
LinearSystem<2, 1, 1> LinearSystemId::ElevatorSystem(DCMotor motor,
units::kilogram_t mass,
units::meter_t radius,
double G) {
if (mass <= 0_kg) {
throw std::domain_error("mass must be greater than zero.");
}
if (radius <= 0_m) {
throw std::domain_error("radius must be greater than zero.");
}
if (G <= 0.0) {
throw std::domain_error("G must be greater than zero.");
}
Matrixd<2, 2> A{
{0.0, 1.0},
{0.0, (-std::pow(G, 2) * motor.Kt /
(motor.R * units::math::pow<2>(radius) * mass * motor.Kv))
.value()}};
Matrixd<2, 1> B{0.0, (G * motor.Kt / (motor.R * radius * mass)).value()};
Matrixd<1, 2> C{1.0, 0.0};
Matrixd<1, 1> D{0.0};
return LinearSystem<2, 1, 1>(A, B, C, D);
}
LinearSystem<2, 1, 1> LinearSystemId::SingleJointedArmSystem(
DCMotor motor, units::kilogram_square_meter_t J, double G) {
if (J <= 0_kg_sq_m) {
throw std::domain_error("J must be greater than zero.");
}
if (G <= 0.0) {
throw std::domain_error("G must be greater than zero.");
}
Matrixd<2, 2> A{
{0.0, 1.0},
{0.0, (-std::pow(G, 2) * motor.Kt / (motor.Kv * motor.R * J)).value()}};
Matrixd<2, 1> B{0.0, (G * motor.Kt / (motor.R * J)).value()};
Matrixd<1, 2> C{1.0, 0.0};
Matrixd<1, 1> D{0.0};
return LinearSystem<2, 1, 1>(A, B, C, D);
}
LinearSystem<2, 2, 2> LinearSystemId::IdentifyDrivetrainSystem(
decltype(1_V / 1_mps) kVLinear, decltype(1_V / 1_mps_sq) kALinear,
decltype(1_V / 1_mps) kVAngular, decltype(1_V / 1_mps_sq) kAAngular) {
if (kVLinear <= decltype(kVLinear){0}) {
throw std::domain_error("Kv,linear must be greater than zero.");
}
if (kALinear <= decltype(kALinear){0}) {
throw std::domain_error("Ka,linear must be greater than zero.");
}
if (kVAngular <= decltype(kVAngular){0}) {
throw std::domain_error("Kv,angular must be greater than zero.");
}
if (kAAngular <= decltype(kAAngular){0}) {
throw std::domain_error("Ka,angular must be greater than zero.");
}
double A1 = -(kVLinear.value() / kALinear.value() +
kVAngular.value() / kAAngular.value());
double A2 = -(kVLinear.value() / kALinear.value() -
kVAngular.value() / kAAngular.value());
double B1 = 1.0 / kALinear.value() + 1.0 / kAAngular.value();
double B2 = 1.0 / kALinear.value() - 1.0 / kAAngular.value();
Matrixd<2, 2> A = 0.5 * Matrixd<2, 2>{{A1, A2}, {A2, A1}};
Matrixd<2, 2> B = 0.5 * Matrixd<2, 2>{{B1, B2}, {B2, B1}};
Matrixd<2, 2> C{{1.0, 0.0}, {0.0, 1.0}};
Matrixd<2, 2> D{{0.0, 0.0}, {0.0, 0.0}};
return LinearSystem<2, 2, 2>(A, B, C, D);
}
LinearSystem<2, 2, 2> LinearSystemId::IdentifyDrivetrainSystem(
decltype(1_V / 1_mps) kVLinear, decltype(1_V / 1_mps_sq) kALinear,
decltype(1_V / 1_rad_per_s) kVAngular,
decltype(1_V / 1_rad_per_s_sq) kAAngular, units::meter_t trackwidth) {
if (kVLinear <= decltype(kVLinear){0}) {
throw std::domain_error("Kv,linear must be greater than zero.");
}
if (kALinear <= decltype(kALinear){0}) {
throw std::domain_error("Ka,linear must be greater than zero.");
}
if (kVAngular <= decltype(kVAngular){0}) {
throw std::domain_error("Kv,angular must be greater than zero.");
}
if (kAAngular <= decltype(kAAngular){0}) {
throw std::domain_error("Ka,angular must be greater than zero.");
}
if (trackwidth <= 0_m) {
throw std::domain_error("r must be greater than zero.");
}
// We want to find a factor to include in Kv,angular that will convert
// `u = Kv,angular omega` to `u = Kv,angular v`.
//
// v = omega r
// omega = v/r
// omega = 1/r v
// omega = 1/(trackwidth/2) v
// omega = 2/trackwidth v
//
// So multiplying by 2/trackwidth converts the angular gains from V/(rad/s)
// to V/(m/s).
return IdentifyDrivetrainSystem(kVLinear, kALinear,
kVAngular * 2.0 / trackwidth * 1_rad,
kAAngular * 2.0 / trackwidth * 1_rad);
}
LinearSystem<1, 1, 1> LinearSystemId::FlywheelSystem(
DCMotor motor, units::kilogram_square_meter_t J, double G) {
if (J <= 0_kg_sq_m) {
throw std::domain_error("J must be greater than zero.");
}
if (G <= 0.0) {
throw std::domain_error("G must be greater than zero.");
}
Matrixd<1, 1> A{
(-std::pow(G, 2) * motor.Kt / (motor.Kv * motor.R * J)).value()};
Matrixd<1, 1> B{(G * motor.Kt / (motor.R * J)).value()};
Matrixd<1, 1> C{1.0};
Matrixd<1, 1> D{0.0};
return LinearSystem<1, 1, 1>(A, B, C, D);
}
LinearSystem<2, 1, 2> LinearSystemId::DCMotorSystem(
DCMotor motor, units::kilogram_square_meter_t J, double G) {
if (J <= 0_kg_sq_m) {
throw std::domain_error("J must be greater than zero.");
}
if (G <= 0.0) {
throw std::domain_error("G must be greater than zero.");
}
Matrixd<2, 2> A{
{0.0, 1.0},
{0.0, (-std::pow(G, 2) * motor.Kt / (motor.Kv * motor.R * J)).value()}};
Matrixd<2, 1> B{0.0, (G * motor.Kt / (motor.R * J)).value()};
Matrixd<2, 2> C{{1.0, 0.0}, {0.0, 1.0}};
Matrixd<2, 1> D{0.0, 0.0};
return LinearSystem<2, 1, 2>(A, B, C, D);
}
LinearSystem<2, 2, 2> LinearSystemId::DrivetrainVelocitySystem(
const DCMotor& motor, units::kilogram_t mass, units::meter_t r,
units::meter_t rb, units::kilogram_square_meter_t J, double G) {
if (mass <= 0_kg) {
throw std::domain_error("mass must be greater than zero.");
}
if (r <= 0_m) {
throw std::domain_error("r must be greater than zero.");
}
if (rb <= 0_m) {
throw std::domain_error("rb must be greater than zero.");
}
if (J <= 0_kg_sq_m) {
throw std::domain_error("J must be greater than zero.");
}
if (G <= 0.0) {
throw std::domain_error("G must be greater than zero.");
}
auto C1 = -std::pow(G, 2) * motor.Kt /
(motor.Kv * motor.R * units::math::pow<2>(r));
auto C2 = G * motor.Kt / (motor.R * r);
Matrixd<2, 2> A{{((1 / mass + units::math::pow<2>(rb) / J) * C1).value(),
((1 / mass - units::math::pow<2>(rb) / J) * C1).value()},
{((1 / mass - units::math::pow<2>(rb) / J) * C1).value(),
((1 / mass + units::math::pow<2>(rb) / J) * C1).value()}};
Matrixd<2, 2> B{{((1 / mass + units::math::pow<2>(rb) / J) * C2).value(),
((1 / mass - units::math::pow<2>(rb) / J) * C2).value()},
{((1 / mass - units::math::pow<2>(rb) / J) * C2).value(),
((1 / mass + units::math::pow<2>(rb) / J) * C2).value()}};
Matrixd<2, 2> C{{1.0, 0.0}, {0.0, 1.0}};
Matrixd<2, 2> D{{0.0, 0.0}, {0.0, 0.0}};
return LinearSystem<2, 2, 2>(A, B, C, D);
}