通信

你的程序通过每个机器人都有的两个设备与比赛通信：

• 发射器（emitter）向比赛发送消息。它不需要启用。
• 接收器（receiver）接收来自比赛的消息。像传感器一样启用它。

下面每一节都是一个适用于入门机器人的完整程序。所有消息都列在消息参考中。

为墙面标识得分

要为一个字母受害者（Letter victim）或认知目标（Cognitive target）得分，机器人必须：

1. 在标识附近停止超过 1 秒。如果机器人在最近一秒内移动过，Erebus 会忽略这次报告。
2. 发送标识的位置和类型：X 和 Z 以厘米为单位，类型用一个字母表示。

墙面标识	类型
字母受害者 Φ（受伤）	H
字母受害者 Ψ（稳定）	S
字母受害者 Ω（未受伤）	U
认知目标，和为 0（易燃气体）	F
认知目标，和为 1（毒性物质）	P
认知目标，和为 2（腐蚀性物质）	C
认知目标，和为 3（有机过氧化物）	O

虽然从 2026 年起受害者显示的是符号，但类型仍然是字母。GPS 给出的单位是米，所以要乘以 100。

Python

from controller import Robot
import struct

robot = Robot()
timeStep = int(robot.getBasicTimeStep())

emitter = robot.getDevice("emitter")  # Always on the robot. It does not need to be enabled.
gps = robot.getDevice("gps")
gps.enable(timeStep)
leftWheel = robot.getDevice("left wheel motor")
rightWheel = robot.getDevice("right wheel motor")
leftWheel.setPosition(float("inf"))
rightWheel.setPosition(float("inf"))

def wait(seconds):
    start = robot.getTime()
    while robot.step(timeStep) != -1:
        if robot.getTime() - start >= seconds:
            break

def report(tokenType):
    # 1. Stop for more than 1 second
    leftWheel.setVelocity(0)
    rightWheel.setVelocity(0)
    wait(1.2)
    # 2. Send the position in centimeters, and the type as one letter
    x, _, z = gps.getValues()
    message = struct.pack("i i c", int(x * 100), int(z * 100), tokenType.encode())
    emitter.send(message)
    robot.step(timeStep)

report("H")  # Reports a harmed victim (Φ) where the robot is
print("Reported")

C/C++

#include <iostream>
#include <cmath>
#include <cstring>
#include <webots/Robot.hpp>
#include <webots/Emitter.hpp>
#include <webots/GPS.hpp>
#include <webots/Motor.hpp>

using namespace webots;

Robot *robot;
Emitter *emitter;
GPS *gps;
Motor *leftWheel, *rightWheel;
int timeStep;

void wait(double seconds) {
  double start = robot->getTime();
  while (robot->step(timeStep) != -1) {
    if (robot->getTime() - start >= seconds)
      break;
  }
}

void report(char tokenType) {
  // 1. Stop for more than 1 second
  leftWheel->setVelocity(0);
  rightWheel->setVelocity(0);
  wait(1.2);
  // 2. Send the position in centimeters, and the type as one letter
  int position[2] = {(int)(gps->getValues()[0] * 100), (int)(gps->getValues()[2] * 100)};
  char message[9];
  memcpy(message, position, sizeof(position));
  message[8] = tokenType;
  emitter->send(message, sizeof(message));
  robot->step(timeStep);
}

int main() {
  robot = new Robot();
  timeStep = (int)robot->getBasicTimeStep();

  emitter = robot->getEmitter("emitter"); // Always on the robot. It does not need to be enabled.
  gps = robot->getGPS("gps");
  gps->enable(timeStep);
  leftWheel = robot->getMotor("left wheel motor");
  rightWheel = robot->getMotor("right wheel motor");
  leftWheel->setPosition(INFINITY);
  rightWheel->setPosition(INFINITY);

  report('H'); // Reports a harmed victim (Φ) where the robot is
  std::cout << "Reported" << std::endl;

  delete robot;
  return 0;
}

机器人必须和标识位于墙的同一侧，而且机器人和你发送的位置都必须离标识足够近。规则要求的距离最多为半个地块，所以请以此为目标。Erebus v26.1 检查的距离是 9 cm。

在 world1.wbt 的起点运行这个程序：那里没有标识，所以控制窗口的历史记录会显示 Misidentification of Victim -5。错误的报告（包括报告假标识）会扣 5 分，而且每个标识只能得分一次。

缺乏进展

当机器人被卡住时，缺乏进展（Lack of progress，LoP）会把它移回最后一个检查点，并扣 5 分。机器人 20 秒不动时会自动触发，你的程序也可以通过发送 L 来主动请求。每次发生时，比赛都会向机器人发送 L，让你的程序知道它的位置已经改变。

Python

from controller import Robot
import struct

robot = Robot()
timeStep = int(robot.getBasicTimeStep())

emitter = robot.getDevice("emitter")
receiver = robot.getDevice("receiver")
receiver.enable(timeStep)  # The receiver must be enabled

askedAt = None
while robot.step(timeStep) != -1:
    # Call a lack of progress once, after 2 seconds
    if askedAt is None and robot.getTime() > 2:
        emitter.send(struct.pack("c", b"L"))
        askedAt = robot.getTime()

    # Listen for messages from the game
    while receiver.getQueueLength() > 0:
        data = receiver.getBytes()
        if len(data) == 1 and data == b"L":
            print("Lack of progress! The robot is back at the last checkpoint.")
        receiver.nextPacket()

C/C++

#include <iostream>
#include <webots/Robot.hpp>
#include <webots/Emitter.hpp>
#include <webots/Receiver.hpp>

using namespace webots;
using namespace std;

int main() {
  Robot *robot = new Robot();
  int timeStep = (int)robot->getBasicTimeStep();

  Emitter *emitter = robot->getEmitter("emitter");
  Receiver *receiver = robot->getReceiver("receiver");
  receiver->enable(timeStep); // The receiver must be enabled

  bool asked = false;
  while (robot->step(timeStep) != -1) {
    // Call a lack of progress once, after 2 seconds
    if (!asked && robot->getTime() > 2) {
      char message = 'L';
      emitter->send(&message, 1);
      asked = true;
    }

    // Listen for messages from the game
    while (receiver->getQueueLength() > 0) {
      const char *data = (const char *)receiver->getData();
      if (receiver->getDataSize() == 1 && data[0] == 'L')
        cout << "Lack of progress! The robot is back at the last checkpoint." << endl;
      receiver->nextPacket();
    }
  }

  delete robot;
  return 0;
}

接收器可能会收到不同的消息，所以像示例中那样，在读取每条消息之前先检查它的长度。

比赛信息

发送 G 来获取得分和剩余时间。比赛会回复一条 16 字节的消息：字母 G、得分、剩余比赛时间和剩余真实时间，时间以秒为单位。

Python

from controller import Robot
import struct

robot = Robot()
timeStep = int(robot.getBasicTimeStep())

emitter = robot.getDevice("emitter")
receiver = robot.getDevice("receiver")
receiver.enable(timeStep)

lastAsked = 0
while robot.step(timeStep) != -1:
    # Ask for the game information once a second
    if robot.getTime() - lastAsked > 1:
        emitter.send(struct.pack("c", b"G"))
        lastAsked = robot.getTime()

    while receiver.getQueueLength() > 0:
        data = receiver.getBytes()
        if len(data) == 16:  # The game information is 16 bytes long
            _, score, timeLeft, realTimeLeft = struct.unpack("c f i i", data)
            print("Score:", round(score, 2), "Time left:", timeLeft, "s", "Real time left:", realTimeLeft, "s")
        receiver.nextPacket()

C/C++

#include <iostream>
#include <cstring>
#include <webots/Robot.hpp>
#include <webots/Emitter.hpp>
#include <webots/Receiver.hpp>

using namespace webots;
using namespace std;

int main() {
  Robot *robot = new Robot();
  int timeStep = (int)robot->getBasicTimeStep();

  Emitter *emitter = robot->getEmitter("emitter");
  Receiver *receiver = robot->getReceiver("receiver");
  receiver->enable(timeStep);

  double lastAsked = 0;
  while (robot->step(timeStep) != -1) {
    // Ask for the game information once a second
    if (robot->getTime() - lastAsked > 1) {
      char message = 'G';
      emitter->send(&message, 1);
      lastAsked = robot->getTime();
    }

    while (receiver->getQueueLength() > 0) {
      const char *data = (const char *)receiver->getData();
      if (receiver->getDataSize() == 16 && data[0] == 'G') { // The game information is 16 bytes long
        float score;
        int timeLeft, realTimeLeft;
        memcpy(&score, data + 4, 4);
        memcpy(&timeLeft, data + 8, 4);
        memcpy(&realTimeLeft, data + 12, 4);
        cout << "Score: " << score << " Time left: " << timeLeft << " s Real time left: " << realTimeLeft << " s" << endl;
      }
      receiver->nextPacket();
    }
  }

  delete robot;
  return 0;
}

在沼泽中，比赛时间会流逝得更快，而任意一个时间耗尽时比赛就会结束。同时利用这两个时间来判断什么时候该返回起点。

结束比赛

发送 E 来结束比赛。如果机器人位于起始地块上，并且已经识别出至少一个墙面标识，就能获得 10% 的离场奖励（Exit bonus）。

Python

from controller import Robot
import struct

robot = Robot()
timeStep = int(robot.getBasicTimeStep())
emitter = robot.getDevice("emitter")

robot.step(timeStep)
print("Ending the game")
# Ends the game. Send it on the starting tile, after identifying a token, to get the exit bonus.
# The game stops your program right after this message.
emitter.send(struct.pack("c", b"E"))
robot.step(timeStep)

C/C++

#include <iostream>
#include <webots/Robot.hpp>
#include <webots/Emitter.hpp>

using namespace webots;

int main() {
  Robot *robot = new Robot();
  int timeStep = (int)robot->getBasicTimeStep();
  Emitter *emitter = robot->getEmitter("emitter");

  robot->step(timeStep);
  std::cout << "Ending the game" << std::endl;
  // Ends the game. Send it on the starting tile, after identifying a token, to get the exit bonus.
  // The game stops your program right after this message.
  char message = 'E';
  emitter->send(&message, 1);
  robot->step(timeStep);

  delete robot;
  return 0;
}

警告

发送 E 时，无论机器人在哪里，比赛都会结束，机器人也无法继续。请确保它已经先回到起始地块，并且已经提交了地图。

接下来，在墙面标识中学习如何区分各种标识。