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main.cpp
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main.cpp
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#include <math.h>
#include <uWS/uWS.h>
#include <chrono>
#include <iostream>
#include <thread>
#include <vector>
#include "Eigen-3.3/Eigen/Core"
#include "Eigen-3.3/Eigen/QR"
#include "MPC.h"
#include "json.hpp"
// for convenience
using json = nlohmann::json;
// For converting back and forth between radians and degrees.
constexpr double pi() { return M_PI; }
double deg2rad(double x) { return x * pi() / 180; }
double rad2deg(double x) { return x * 180 / pi(); }
// Checks if the SocketIO event has JSON data.
// If there is data the JSON object in string format will be returned,
// else the empty string "" will be returned.
string hasData(string s) {
auto found_null = s.find("null");
auto b1 = s.find_first_of("[");
auto b2 = s.rfind("}]");
if (found_null != string::npos) {
return "";
} else if (b1 != string::npos && b2 != string::npos) {
return s.substr(b1, b2 - b1 + 2);
}
return "";
}
// Evaluate a polynomial.
double polyeval(Eigen::VectorXd coeffs, double x) {
double result = 0.0;
for (int i = 0; i < coeffs.size(); i++) {
result += coeffs[i] * pow(x, i);
}
return result;
}
// Fit a polynomial.
// Adapted from
// https://github.com/JuliaMath/Polynomials.jl/blob/master/src/Polynomials.jl#L676-L716
Eigen::VectorXd polyfit(Eigen::VectorXd xvals, Eigen::VectorXd yvals,
int order) {
assert(xvals.size() == yvals.size());
assert(order >= 1 && order <= xvals.size() - 1);
Eigen::MatrixXd A(xvals.size(), order + 1);
for (int i = 0; i < xvals.size(); i++) {
A(i, 0) = 1.0;
}
for (int j = 0; j < xvals.size(); j++) {
for (int i = 0; i < order; i++) {
A(j, i + 1) = A(j, i) * xvals(j);
}
}
auto Q = A.householderQr();
auto result = Q.solve(yvals);
return result;
}
int main() {
uWS::Hub h;
// MPC is initialized here!
MPC mpc;
h.onMessage([&mpc](uWS::WebSocket<uWS::SERVER> ws, char *data, size_t length,
uWS::OpCode opCode) {
// "42" at the start of the message means there's a websocket message event.
// The 4 signifies a websocket message
// The 2 signifies a websocket event
string sdata = string(data).substr(0, length);
if (sdata.size() > 2 && sdata[0] == '4' && sdata[1] == '2') {
string s = hasData(sdata);
if (s != "") {
auto j = json::parse(s);
string event = j[0].get<string>();
if (event == "telemetry") {
// j[1] is the data JSON object
vector<double> ptsx = j[1]["ptsx"];
vector<double> ptsy = j[1]["ptsy"];
double px = j[1]["x"];
double py = j[1]["y"];
double psi = j[1]["psi"];
double v = j[1]["speed"];
double delta = j[1]["steering_angle"];
double a = j[1]["throttle"];
// Transform waypoint coordinates into car's local coordinates, based on the heading direction (+/-).
size_t num_waypoints = ptsx.size();
auto transformed_ptsx = Eigen::VectorXd(num_waypoints);
auto transformed_ptsy = Eigen::VectorXd(num_waypoints);
for (unsigned int i=0; i<num_waypoints; ++i) {
double dx = ptsx[i] - px;
double dy = ptsy[i] - py;
double neg_psi = 0. - psi;
transformed_ptsx(i) = dx * cos(neg_psi) - dy * sin(neg_psi);
transformed_ptsy(i) = dx * sin(neg_psi) + dy * cos(neg_psi);
}
// Fit a 3rd-degree polynomial to the waypoints.
auto coeffs = polyfit(transformed_ptsx, transformed_ptsy, 3);
// Include actuator delay.
const int actuator_delay = 100; // in milliseconds.
const double delay = actuator_delay / 1000.; // in seconds.
// Initial state.
const double x0 = 0.;
const double y0 = 0.;
const double psi0 = 0.;
const double cte0 = coeffs[0];
const double epsi0 = -atan(coeffs[1]);
// State after actuator delay.
double x_d = x0 + (v * cos(psi0) * delay);
double y_d = y0 + (v * sin(psi0) * delay);
double psi_d = psi0 - (v * delta * delay / Lf);
double v_d = v + a * delay;
double cte_d = cte0 + (v * sin(epsi0) * delay);
double epsi_d = epsi0 - (v * delta * delay / Lf);
// State vector.
Eigen::VectorXd state(6);
state << x_d, y_d, psi_d, v_d, cte_d, epsi_d;
// Solve for a MPC trajectory.
auto vars = mpc.Solve(state, coeffs);
double steer_value = vars[0] / deg2rad(25);
double throttle_value = vars[1];
json msgJson;
// NOTE: Remember to divide by deg2rad(25) before you send the steering value back.
// Otherwise the values will be in between [-deg2rad(25), deg2rad(25] instead of [-1, 1].
msgJson["steering_angle"] = steer_value;
msgJson["throttle"] = throttle_value;
//// Display the MPC predicted trajectory
vector<double> mpc_x_vals;
vector<double> mpc_y_vals;
// Extract MPC predicted-trajectory points.
for (unsigned int i=2; i<vars.size(); ++i) {
if (i % 2 == 0) { // x-coordinate.
mpc_x_vals.push_back(vars[i]);
}
else {
mpc_y_vals.push_back(vars[i]);
}
}
msgJson["mpc_x"] = mpc_x_vals;
msgJson["mpc_y"] = mpc_y_vals;
//// Display the waypoints/reference line
vector<double> next_x_vals;
vector<double> next_y_vals;
// Create a polyline based on current position.
int num_points = 25;
double step_len = 2.5;
for (int i=0; i<num_points; ++i) {
double x = step_len * i;
next_x_vals.push_back(x);
next_y_vals.push_back(polyeval(coeffs, x));
}
msgJson["next_x"] = next_x_vals;
msgJson["next_y"] = next_y_vals;
auto msg = "42[\"steer\"," + msgJson.dump() + "]";
//// DEBUG
// std::cout << msg << std::endl;
// Latency
// The purpose is to mimic real driving conditions where
// the car does actuate the commands instantly.
// NOTE: REMEMBER TO SET THIS TO actuator_delay MILLISECONDS BEFORE
// SUBMITTING.
this_thread::sleep_for(chrono::milliseconds(actuator_delay));
ws.send(msg.data(), msg.length(), uWS::OpCode::TEXT);
}
} else {
// Manual driving
std::string msg = "42[\"manual\",{}]";
ws.send(msg.data(), msg.length(), uWS::OpCode::TEXT);
}
}
});
// We don't need this since we're not using HTTP but if it's removed the
// program
// doesn't compile :-(
h.onHttpRequest([](uWS::HttpResponse *res, uWS::HttpRequest req, char *data,
size_t, size_t) {
const std::string s = "<h1>Hello world!</h1>";
if (req.getUrl().valueLength == 1) {
res->end(s.data(), s.length());
} else {
// i guess this should be done more gracefully?
res->end(nullptr, 0);
}
});
h.onConnection([&h](uWS::WebSocket<uWS::SERVER> ws, uWS::HttpRequest req) {
std::cout << "Connected!!!" << std::endl;
});
h.onDisconnection([&h](uWS::WebSocket<uWS::SERVER> ws, int code,
char *message, size_t length) {
ws.close();
std::cout << "Disconnected" << std::endl;
});
int port = 4567;
if (h.listen(port)) {
std::cout << "Listening to port " << port << std::endl;
} else {
std::cerr << "Failed to listen to port" << std::endl;
return -1;
}
h.run();
}