VehicleDifferential_ControllerTwistPID.cpp

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/*+-------------------------------------------------------------------------+
  |                       MultiVehicle simulator (libmvsim)                 |
  |                                                                         |
  | Copyright (C) 2014-2023  Jose Luis Blanco Claraco                       |
  | Copyright (C) 2017  Borys Tymchenko (Odessa Polytechnic University)     |
  | Distributed under 3-clause BSD License                                  |
  |   See COPYING                                                           |
  +-------------------------------------------------------------------------+ */

#include <mvsim/VehicleDynamics/VehicleDifferential.h>

#include "xml_utils.h"

using namespace mvsim;
using namespace std;

DynamicsDifferential::ControllerTwistPID::ControllerTwistPID(
        DynamicsDifferential& veh)
        : ControllerBase(veh)
{
        // Get distance between wheels:
        // Warning: the controller *assumes* that both wheels are parallel (as it's
        // a rule in differential robots!!)
        distWheels_ = veh_.wheels_info_[0].y - veh_.wheels_info_[1].y;
        ASSERT_(distWheels_ > 0);
}

// See base class docs
void DynamicsDifferential::ControllerTwistPID::control_step(
        const DynamicsDifferential::TControllerInput& ci,
        DynamicsDifferential::TControllerOutput& co)
{
        const auto sp = setpoint();

        // For each wheel:
        // 1) Compute desired velocity set-point (in m/s)
        // 2) Run the PI/PID for that wheel independently (in newtons)
        const double spVelL = sp.vx - 0.5 * sp.omega * distWheels_;
        const double spVelR = sp.vx + 0.5 * sp.omega * distWheels_;

        // Compute each wheel actual velocity (from an "odometry" estimation of
        // velocity, not ground-truth!):
        const mrpt::math::TTwist2D vehVelOdo = veh_.getVelocityLocalOdoEstimate();
        const double actVelL = vehVelOdo.vx - 0.5 * vehVelOdo.omega * distWheels_;
        const double actVelR = vehVelOdo.vx + 0.5 * vehVelOdo.omega * distWheels_;

        // Apply controller:
        for (auto& pid : PIDs_)
        {
                pid.KP = KP;
                pid.KI = KI;
                pid.KD = KD;
                pid.max_out = max_torque;
        }

        // "-" because \tau<0 makes robot moves forwards.
        const double followErrorL = spVelL - actVelL;
        const double followErrorR = spVelR - actVelR;

        const double zeroThres = 0.001;  // m/s

        if (std::abs(spVelL) < zeroThres &&      //
                std::abs(spVelR) < zeroThres &&  //
                std::abs(spVelR) < zeroThres &&  //
                std::abs(spVelR) < zeroThres)
        {
                co.wheel_torque_l = 0;
                co.wheel_torque_r = 0;
                for (auto& pid : PIDs_) pid.reset();
        }
        else
        {
                co.wheel_torque_l = -PIDs_[0].compute(followErrorL, ci.context.dt);
                co.wheel_torque_r = -PIDs_[1].compute(followErrorR, ci.context.dt);
        }
}

void DynamicsDifferential::ControllerTwistPID::load_config(
        const rapidxml::xml_node<char>& node)
{
        TParameterDefinitions params;
        params["KP"] = TParamEntry("%lf", &KP);
        params["KI"] = TParamEntry("%lf", &KI);
        params["KD"] = TParamEntry("%lf", &KD);
        params["max_torque"] = TParamEntry("%lf", &max_torque);

        // Initial speed.
        params["V"] = TParamEntry("%lf", &setpoint_.vx);
        params["W"] = TParamEntry("%lf_deg", &setpoint_.omega);

        parse_xmlnode_children_as_param(node, params);
}

void DynamicsDifferential::ControllerTwistPID::teleop_interface(
        const TeleopInput& in, TeleopOutput& out)
{
        ControllerBase::teleop_interface(in, out);

        auto lck = mrpt::lockHelper(setpointMtx_);

        switch (in.keycode)
        {
                case 'W':
                case 'w':
                        setpoint_.vx += 0.1;
                        break;

                case 'S':
                case 's':
                        setpoint_.vx -= 0.1;
                        break;

                case 'A':
                case 'a':
                        setpoint_.omega += 2.0 * M_PI / 180;
                        break;

                case 'D':
                case 'd':
                        setpoint_.omega -= 2.0 * M_PI / 180;
                        break;

                case ' ':
                {
                        setpoint_ = {0, 0, 0};
                        for (auto& pid : PIDs_) pid.reset();
                }
                break;
        };
        out.append_gui_lines += "[Controller=" + string(class_name()) +
                                                        "] Teleop keys:\n"
                                                        "w/s=forward/backward.\n"
                                                        "a/d=left/right.\n"
                                                        "spacebar=stop.\n";
        out.append_gui_lines += mrpt::format(
                "setpoint: lin=%.03f ang=%.03f deg/s\n", setpoint_.vx,
                180.0 / M_PI * setpoint_.omega);
}