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allwpilib/wpilibc/src/main/native/cpp/simulation/ElevatorSim.cpp

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C++

// 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/simulation/ElevatorSim.h"
#include <wpi/MathExtras.h>
#include "frc/RobotController.h"
#include "frc/system/NumericalIntegration.h"
#include "frc/system/plant/LinearSystemId.h"
using namespace frc;
using namespace frc::sim;
ElevatorSim::ElevatorSim(const LinearSystem<2, 1, 2>& plant,
const DCMotor& gearbox, units::meter_t minHeight,
units::meter_t maxHeight, bool simulateGravity,
units::meter_t startingHeight,
const std::array<double, 2>& measurementStdDevs)
: LinearSystemSim(plant, measurementStdDevs),
m_gearbox(gearbox),
m_minHeight(minHeight),
m_maxHeight(maxHeight),
m_simulateGravity(simulateGravity) {
SetState(startingHeight, 0_mps);
}
ElevatorSim::ElevatorSim(const DCMotor& gearbox, double gearing,
units::kilogram_t carriageMass,
units::meter_t drumRadius, units::meter_t minHeight,
units::meter_t maxHeight, bool simulateGravity,
units::meter_t startingHeight,
const std::array<double, 2>& measurementStdDevs)
: ElevatorSim(LinearSystemId::ElevatorSystem(gearbox, carriageMass,
drumRadius, gearing),
gearbox, minHeight, maxHeight, simulateGravity,
startingHeight, measurementStdDevs) {}
template <typename Distance>
requires std::same_as<units::meter, Distance> ||
std::same_as<units::radian, Distance>
ElevatorSim::ElevatorSim(decltype(1_V / Velocity_t<Distance>(1)) kV,
decltype(1_V / Acceleration_t<Distance>(1)) kA,
const DCMotor& gearbox, units::meter_t minHeight,
units::meter_t maxHeight, bool simulateGravity,
units::meter_t startingHeight,
const std::array<double, 2>& measurementStdDevs)
: ElevatorSim(LinearSystemId::IdentifyPositionSystem(kV, kA), gearbox,
minHeight, maxHeight, simulateGravity, startingHeight,
measurementStdDevs) {}
void ElevatorSim::SetState(units::meter_t position,
units::meters_per_second_t velocity) {
SetState(
Vectord<2>{std::clamp(position, m_minHeight, m_maxHeight), velocity});
}
bool ElevatorSim::WouldHitLowerLimit(units::meter_t elevatorHeight) const {
return elevatorHeight <= m_minHeight;
}
bool ElevatorSim::WouldHitUpperLimit(units::meter_t elevatorHeight) const {
return elevatorHeight >= m_maxHeight;
}
bool ElevatorSim::HasHitLowerLimit() const {
return WouldHitLowerLimit(units::meter_t{m_y(0)});
}
bool ElevatorSim::HasHitUpperLimit() const {
return WouldHitUpperLimit(units::meter_t{m_y(0)});
}
units::meter_t ElevatorSim::GetPosition() const {
return units::meter_t{m_y(0)};
}
units::meters_per_second_t ElevatorSim::GetVelocity() const {
return units::meters_per_second_t{m_x(1)};
}
units::ampere_t ElevatorSim::GetCurrentDraw() const {
// I = V / R - omega / (Kv * R)
// Reductions are greater than 1, so a reduction of 10:1 would mean the motor
// is spinning 10x faster than the output.
double kA = 1.0 / m_plant.B(1, 0);
using Kv_t = units::unit_t<units::compound_unit<
units::volt, units::inverse<units::meters_per_second>>>;
Kv_t Kv = Kv_t{kA * m_plant.A(1, 1)};
units::meters_per_second_t velocity{m_x(1)};
units::radians_per_second_t motorVelocity = velocity * Kv * m_gearbox.Kv;
// Perform calculation and return.
return m_gearbox.Current(motorVelocity, units::volt_t{m_u(0)}) *
wpi::sgn(m_u(0));
}
void ElevatorSim::SetInputVoltage(units::volt_t voltage) {
SetInput(Vectord<1>{voltage.value()});
ClampInput(frc::RobotController::GetBatteryVoltage().value());
}
Vectord<2> ElevatorSim::UpdateX(const Vectord<2>& currentXhat,
const Vectord<1>& u, units::second_t dt) {
auto updatedXhat = RKDP(
[&](const Vectord<2>& x, const Vectord<1>& u_) -> Vectord<2> {
Vectord<2> xdot = m_plant.A() * x + m_plant.B() * u;
if (m_simulateGravity) {
xdot += Vectord<2>{0.0, -9.8};
}
return xdot;
},
currentXhat, u, dt);
// Check for collision after updating x-hat.
if (WouldHitLowerLimit(units::meter_t{updatedXhat(0)})) {
return Vectord<2>{m_minHeight.value(), 0.0};
}
if (WouldHitUpperLimit(units::meter_t{updatedXhat(0)})) {
return Vectord<2>{m_maxHeight.value(), 0.0};
}
return updatedXhat;
}