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[wpilib] Add physics simulation support with state-space (#2615)
This includes physics simulation support for arms/elevator models, as well as differential drivetrains. Swerve might be added at a later date. Co-authored-by: Claudius Tewari <cttewari@gmail.com> Co-authored-by: Prateek Machiraju <prateek.machiraju@gmail.com> Co-authored-by: Tyler Veness <calcmogul@gmail.com>
This commit is contained in:
Matt
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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 2017-2020 FIRST. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#include <frc/Encoder.h>
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#include <frc/GenericHID.h>
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#include <frc/Joystick.h>
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#include <frc/PWMVictorSPX.h>
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#include <frc/RobotController.h>
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#include <frc/StateSpaceUtil.h>
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#include <frc/TimedRobot.h>
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#include <frc/controller/PIDController.h>
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#include <frc/simulation/BatterySim.h>
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#include <frc/simulation/EncoderSim.h>
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#include <frc/simulation/RoboRioSim.h>
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#include <frc/simulation/SingleJointedArmSim.h>
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#include <frc/system/plant/LinearSystemId.h>
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#include <units/angle.h>
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#include <units/moment_of_inertia.h>
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#include <wpi/math>
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/**
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* This is a sample program to demonstrate how to use a state-space controller
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* to control an arm.
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*/
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class Robot : public frc::TimedRobot {
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static constexpr int kMotorPort = 0;
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static constexpr int kEncoderAChannel = 0;
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static constexpr int kEncoderBChannel = 1;
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static constexpr int kJoystickPort = 0;
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// The P gain for the PID controller that drives this arm.
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static constexpr double kArmKp = 5.0;
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// distance per pulse = (angle per revolution) / (pulses per revolution)
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// = (2 * PI rads) / (4096 pulses)
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static constexpr double kArmEncoderDistPerPulse =
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2.0 * wpi::math::pi / 4096.0;
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// The arm gearbox represents a gerbox containing two Vex 775pro motors.
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frc::DCMotor m_armGearbox = frc::DCMotor::Vex775Pro(2);
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// Standard classes for controlling our arm
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frc2::PIDController m_controller{kArmKp, 0, 0};
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frc::Encoder m_encoder{kEncoderAChannel, kEncoderBChannel};
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frc::PWMVictorSPX m_motor{kMotorPort};
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frc::Joystick m_joystick{kJoystickPort};
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// Simulation classes help us simulate what's going on, including gravity.
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// This sim represents an arm with 2 775s, a 100:1 reduction, a mass of 5kg,
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// 30in overall arm length, range of motion nin [-180, 0] degrees, and noise
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// with a standard deviation of 0.5 degrees.
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frc::sim::SingleJointedArmSim m_armSim{
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m_armGearbox, 100.0, 5_kg, 30_in,
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-180_deg, 0_deg, true, {(0.5_deg).to<double>()}};
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frc::sim::EncoderSim m_encoderSim{m_encoder};
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public:
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void RobotInit() { m_encoder.SetDistancePerPulse(kArmEncoderDistPerPulse); }
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void SimulationPeriodic() {
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// In this method, we update our simulation of what our arm is doing
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// First, we set our "inputs" (voltages)
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m_armSim.SetInput(frc::MakeMatrix<1, 1>(
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m_motor.Get() * frc::RobotController::GetInputVoltage()));
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// Next, we update it. The standard loop time is 20ms.
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m_armSim.Update(20_ms);
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// Finally, we set our simulated encoder's readings and simulated battery
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// voltage
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m_encoderSim.SetDistance(m_armSim.GetAngle().to<double>());
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// SimBattery estimates loaded battery voltages
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frc::sim::RoboRioSim::SetVInVoltage(
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frc::sim::BatterySim::Calculate({m_armSim.GetCurrentDraw()})
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.to<double>());
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}
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void TeleopPeriodic() {
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if (m_joystick.GetTrigger()) {
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// Here, we run PID control like normal, with a constant setpoint of 30in.
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double pidOutput =
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m_controller.Calculate(m_encoder.GetDistance(), (30_in).to<double>());
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m_motor.SetVoltage(units::volt_t(pidOutput));
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} else {
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// Otherwise, we disable the motor.
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m_motor.Set(0.0);
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}
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}
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void DisabledInit() {
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// This just makes sure that our simulation code knows that the motor's off.
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m_motor.Set(0.0);
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}
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};
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#ifndef RUNNING_FRC_TESTS
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int main() { return frc::StartRobot<Robot>(); }
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#endif
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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 2019-2020 FIRST. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#include "Drivetrain.h"
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#include <frc/RobotController.h>
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void Drivetrain::SetSpeeds(const frc::DifferentialDriveWheelSpeeds& speeds) {
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auto leftFeedforward = m_feedforward.Calculate(speeds.left);
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auto rightFeedforward = m_feedforward.Calculate(speeds.right);
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double leftOutput = m_leftPIDController.Calculate(m_leftEncoder.GetRate(),
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speeds.left.to<double>());
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double rightOutput = m_rightPIDController.Calculate(
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m_rightEncoder.GetRate(), speeds.right.to<double>());
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m_leftGroup.SetVoltage(units::volt_t{leftOutput} + leftFeedforward);
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m_rightGroup.SetVoltage(units::volt_t{rightOutput} + rightFeedforward);
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}
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void Drivetrain::Drive(units::meters_per_second_t xSpeed,
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units::radians_per_second_t rot) {
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SetSpeeds(m_kinematics.ToWheelSpeeds({xSpeed, 0_mps, rot}));
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}
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void Drivetrain::UpdateOdometry() {
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m_odometry.Update(m_gyro.GetRotation2d(),
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units::meter_t(m_leftEncoder.GetDistance()),
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units::meter_t(m_rightEncoder.GetDistance()));
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}
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void Drivetrain::SimulationPeriodic() {
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// To update our simulation, we set motor voltage inputs, update the
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// simulation, and write the simulated positions and velocities to our
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// simulated encoder and gyro. We negate the right side so that positive
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// voltages make the right side move forward.
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m_drivetrainSimulator.SetInputs(units::volt_t{m_leftLeader.Get()} *
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frc::RobotController::GetInputVoltage(),
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units::volt_t{-m_rightLeader.Get()} *
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frc::RobotController::GetInputVoltage());
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m_drivetrainSimulator.Update(20_ms);
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m_leftEncoderSim.SetDistance(m_drivetrainSimulator.GetState(
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frc::sim::DifferentialDrivetrainSim::State::kLeftPosition));
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m_leftEncoderSim.SetRate(m_drivetrainSimulator.GetState(
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frc::sim::DifferentialDrivetrainSim::State::kLeftVelocity));
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m_rightEncoderSim.SetDistance(m_drivetrainSimulator.GetState(
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frc::sim::DifferentialDrivetrainSim::State::kRightPosition));
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m_rightEncoderSim.SetRate(m_drivetrainSimulator.GetState(
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frc::sim::DifferentialDrivetrainSim::State::kRightVelocity));
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m_gyroSim.SetAngle(
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-m_drivetrainSimulator.GetHeading().Degrees().to<double>());
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m_fieldSim.SetRobotPose(m_odometry.GetPose());
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}
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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 2019-2020 FIRST. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#include <frc/SlewRateLimiter.h>
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#include <frc/TimedRobot.h>
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#include <frc/XboxController.h>
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#include "Drivetrain.h"
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class Robot : public frc::TimedRobot {
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public:
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void AutonomousPeriodic() override {
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TeleopPeriodic();
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m_drive.UpdateOdometry();
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}
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void TeleopPeriodic() override {
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// Get the x speed. We are inverting this because Xbox controllers return
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// negative values when we push forward.
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const auto xSpeed = -m_speedLimiter.Calculate(
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m_controller.GetY(frc::GenericHID::kLeftHand)) *
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Drivetrain::kMaxSpeed;
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// Get the rate of angular rotation. We are inverting this because we want a
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// positive value when we pull to the left (remember, CCW is positive in
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// mathematics). Xbox controllers return positive values when you pull to
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// the right by default.
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auto rot = -m_rotLimiter.Calculate(
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m_controller.GetX(frc::GenericHID::kRightHand)) *
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Drivetrain::kMaxAngularSpeed;
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m_drive.Drive(xSpeed, rot);
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}
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void SimulationPeriodic() override { m_drive.SimulationPeriodic(); }
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private:
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frc::XboxController m_controller{0};
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// Slew rate limiters to make joystick inputs more gentle; 1/3 sec from 0
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// to 1.
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frc::SlewRateLimiter<units::scalar> m_speedLimiter{3 / 1_s};
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frc::SlewRateLimiter<units::scalar> m_rotLimiter{3 / 1_s};
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Drivetrain m_drive;
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};
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#ifndef RUNNING_FRC_TESTS
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int main() { return frc::StartRobot<Robot>(); }
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#endif
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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 2019-2020 FIRST. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#pragma once
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#include <frc/AnalogGyro.h>
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#include <frc/Encoder.h>
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#include <frc/PWMVictorSPX.h>
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#include <frc/SpeedControllerGroup.h>
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#include <frc/controller/PIDController.h>
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#include <frc/controller/SimpleMotorFeedforward.h>
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#include <frc/kinematics/DifferentialDriveKinematics.h>
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#include <frc/kinematics/DifferentialDriveOdometry.h>
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#include <frc/simulation/AnalogGyroSim.h>
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#include <frc/simulation/DifferentialDrivetrainSim.h>
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#include <frc/simulation/EncoderSim.h>
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#include <frc/simulation/Field2d.h>
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#include <frc/system/plant/LinearSystemId.h>
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#include <units/angle.h>
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#include <units/angular_velocity.h>
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#include <units/length.h>
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#include <units/velocity.h>
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#include <wpi/math>
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/**
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* Represents a differential drive style drivetrain.
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*/
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class Drivetrain {
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public:
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Drivetrain() {
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m_gyro.Reset();
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// Set the distance per pulse for the drive encoders. We can simply use the
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// distance traveled for one rotation of the wheel divided by the encoder
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// resolution.
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m_leftEncoder.SetDistancePerPulse(2 * wpi::math::pi * kWheelRadius /
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kEncoderResolution);
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m_rightEncoder.SetDistancePerPulse(2 * wpi::math::pi * kWheelRadius /
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kEncoderResolution);
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m_leftEncoder.Reset();
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m_rightEncoder.Reset();
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}
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static constexpr units::meters_per_second_t kMaxSpeed =
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3.0_mps; // 3 meters per second
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static constexpr units::radians_per_second_t kMaxAngularSpeed{
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wpi::math::pi}; // 1/2 rotation per second
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void SetSpeeds(const frc::DifferentialDriveWheelSpeeds& speeds);
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void Drive(units::meters_per_second_t xSpeed,
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units::radians_per_second_t rot);
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void UpdateOdometry();
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void SimulationPeriodic();
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private:
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static constexpr units::meter_t kTrackWidth = 0.381_m * 2;
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static constexpr double kWheelRadius = 0.0508; // meters
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static constexpr int kEncoderResolution = 4096;
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frc::PWMVictorSPX m_leftLeader{1};
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frc::PWMVictorSPX m_leftFollower{2};
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frc::PWMVictorSPX m_rightLeader{3};
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frc::PWMVictorSPX m_rightFollower{4};
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frc::SpeedControllerGroup m_leftGroup{m_leftLeader, m_leftFollower};
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frc::SpeedControllerGroup m_rightGroup{m_rightLeader, m_rightFollower};
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frc::Encoder m_leftEncoder{0, 1};
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frc::Encoder m_rightEncoder{2, 3};
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frc2::PIDController m_leftPIDController{1.0, 0.0, 0.0};
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frc2::PIDController m_rightPIDController{1.0, 0.0, 0.0};
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frc::AnalogGyro m_gyro{0};
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frc::DifferentialDriveKinematics m_kinematics{kTrackWidth};
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frc::DifferentialDriveOdometry m_odometry{m_gyro.GetRotation2d()};
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// Gains are for example purposes only - must be determined for your own
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// robot!
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frc::SimpleMotorFeedforward<units::meters> m_feedforward{1_V, 3_V / 1_mps};
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// Simulation classes help us simulate our robot
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frc::sim::AnalogGyroSim m_gyroSim{m_gyro};
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frc::sim::EncoderSim m_leftEncoderSim{m_leftEncoder};
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frc::sim::EncoderSim m_rightEncoderSim{m_rightEncoder};
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frc::Field2d m_fieldSim{};
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frc::LinearSystem<2, 2, 2> m_drivetrainSystem =
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frc::LinearSystemId::IdentifyDrivetrainSystem(1.98, 0.2, 1.5, 0.3);
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frc::sim::DifferentialDrivetrainSim m_drivetrainSimulator{
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m_drivetrainSystem, kTrackWidth, frc::DCMotor::CIM(2), 8, 2_in};
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};
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@@ -0,0 +1,109 @@
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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 2017-2020 FIRST. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#include <frc/Encoder.h>
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#include <frc/GenericHID.h>
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#include <frc/Joystick.h>
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#include <frc/PWMVictorSPX.h>
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#include <frc/RobotController.h>
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#include <frc/StateSpaceUtil.h>
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#include <frc/TimedRobot.h>
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#include <frc/controller/PIDController.h>
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#include <frc/simulation/BatterySim.h>
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#include <frc/simulation/ElevatorSim.h>
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#include <frc/simulation/EncoderSim.h>
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#include <frc/simulation/RoboRioSim.h>
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#include <frc/system/plant/LinearSystemId.h>
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#include <units/angle.h>
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#include <units/moment_of_inertia.h>
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#include <wpi/math>
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/**
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* This is a sample program to demonstrate how to use a state-space controller
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* to control an arm.
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*/
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class Robot : public frc::TimedRobot {
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static constexpr int kMotorPort = 0;
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static constexpr int kEncoderAChannel = 0;
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static constexpr int kEncoderBChannel = 1;
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static constexpr int kJoystickPort = 0;
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static constexpr double kElevatorKp = 5.0;
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static constexpr double kElevatorGearing = 10.0;
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static constexpr units::meter_t kElevatorDrumRadius = 2_in;
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static constexpr units::kilogram_t kCarriageMass = 4.0_kg;
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static constexpr units::meter_t kMinElevatorHeight = 0_in;
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static constexpr units::meter_t kMaxElevatorHeight = 50_in;
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// distance per pulse = (distance per revolution) / (pulses per revolution)
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// = (Pi * D) / ppr
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static constexpr double kArmEncoderDistPerPulse =
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2.0 * wpi::math::pi * kElevatorDrumRadius.to<double>() / 4096.0;
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// This gearbox represents a gearbox containing 4 Vex 775pro motors.
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frc::DCMotor m_elevatorGearbox = frc::DCMotor::Vex775Pro(4);
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// Standard classes for controlling our elevator
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frc2::PIDController m_controller{kElevatorKp, 0, 0};
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frc::Encoder m_encoder{kEncoderAChannel, kEncoderBChannel};
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frc::PWMVictorSPX m_motor{kMotorPort};
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frc::Joystick m_joystick{kJoystickPort};
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// Simulation classes help us simulate what's going on, including gravity.
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frc::sim::ElevatorSim m_elevatorSim{m_elevatorGearbox,
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kCarriageMass,
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kElevatorGearing,
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kElevatorDrumRadius,
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kMinElevatorHeight,
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kMaxElevatorHeight,
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true,
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{0.01}};
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frc::sim::EncoderSim m_encoderSim{m_encoder};
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public:
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void RobotInit() { m_encoder.SetDistancePerPulse(kArmEncoderDistPerPulse); }
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void SimulationPeriodic() {
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// In this method, we update our simulation of what our elevator is doing
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// First, we set our "inputs" (voltages)
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m_elevatorSim.SetInput(frc::MakeMatrix<1, 1>(
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m_motor.Get() * frc::RobotController::GetInputVoltage()));
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// Next, we update it. The standard loop time is 20ms.
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m_elevatorSim.Update(20_ms);
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// Finally, we set our simulated encoder's readings and simulated battery
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// voltage
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m_encoderSim.SetDistance(m_elevatorSim.GetPosition().to<double>());
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// SimBattery estimates loaded battery voltages
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frc::sim::RoboRioSim::SetVInVoltage(
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frc::sim::BatterySim::Calculate({m_elevatorSim.GetCurrentDraw()})
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.to<double>());
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}
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void TeleopPeriodic() {
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if (m_joystick.GetTrigger()) {
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// Here, we run PID control like normal, with a constant setpoint of 30in.
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double pidOutput =
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m_controller.Calculate(m_encoder.GetDistance(), (30_in).to<double>());
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m_motor.SetVoltage(units::volt_t(pidOutput));
|
||||
} else {
|
||||
// Otherwise, we disable the motor.
|
||||
m_motor.Set(0.0);
|
||||
}
|
||||
}
|
||||
|
||||
void DisabledInit() {
|
||||
// This just makes sure that our simulation code knows that the motor's off.
|
||||
m_motor.Set(0.0);
|
||||
}
|
||||
};
|
||||
|
||||
#ifndef RUNNING_FRC_TESTS
|
||||
int main() { return frc::StartRobot<Robot>(); }
|
||||
#endif
|
||||
@@ -611,5 +611,55 @@
|
||||
"gradlebase": "cpp",
|
||||
"mainclass": "Main",
|
||||
"commandversion": 2
|
||||
},
|
||||
{
|
||||
"name": "ElevatorSimulation",
|
||||
"description": "Demonstrates the use of physics simulation with a simple elevator.",
|
||||
"tags": [
|
||||
"Elevator",
|
||||
"State space",
|
||||
"Digital",
|
||||
"Sensors",
|
||||
"Simulation",
|
||||
"Physics"
|
||||
],
|
||||
"foldername": "ElevatorSimulation",
|
||||
"gradlebase": "cpp",
|
||||
"mainclass": "Main",
|
||||
"commandversion": 2
|
||||
},
|
||||
{
|
||||
"name": "ArmSimulation",
|
||||
"description": "Demonstrates the use of physics simulation with a simple single-jointed arm.",
|
||||
"tags": [
|
||||
"Arm",
|
||||
"State space",
|
||||
"Digital",
|
||||
"Sensors",
|
||||
"Simulation",
|
||||
"Physics"
|
||||
],
|
||||
"foldername": "ArmSimulation",
|
||||
"gradlebase": "cpp",
|
||||
"mainclass": "Main",
|
||||
"commandversion": 2
|
||||
},
|
||||
{
|
||||
"name": "DifferentialDriveSimulation",
|
||||
"description": "Demonstrates the use of physics simulation with a differential drivetrain and the Field2d class.",
|
||||
"tags": [
|
||||
"Differential Drive",
|
||||
"State space",
|
||||
"Digital",
|
||||
"Sensors",
|
||||
"Simulation",
|
||||
"Physics",
|
||||
"Drivetrain",
|
||||
"Field2d"
|
||||
],
|
||||
"foldername": "DifferentialDriveSimulation",
|
||||
"gradlebase": "cpp",
|
||||
"mainclass": "Main",
|
||||
"commandversion": 2
|
||||
}
|
||||
]
|
||||
|
||||
Reference in New Issue
Block a user