激光雷达

激光雷达（LIDAR）测量机器人四周的距离，单位为米，就像同时使用许多个距离传感器一样。在入门机器人上，它的名字是 lidar，位于机器人顶部。

它会测量机器人周围的 512 个点，共有 4 层，一层叠在另一层上面，最远可达 1 m。没有碰到任何物体的点读数为 inf。

读取距离

getLayerRangeImage(0) 给出某一层的 512 个距离。第一个点在机器人正前方，之后按顺时针方向排列：四分之一处在右侧，一半处在后方，四分之三处在左侧。

Python

from controller import Robot

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

lidar = robot.getDevice("lidar")
lidar.enable(timeStep)
n = lidar.getHorizontalResolution()  # Number of points in each layer
print("Points per layer:", n, "Layers:", lidar.getNumberOfLayers())

while robot.step(timeStep) != -1:
    distances = lidar.getLayerRangeImage(0)  # One layer, in meters, clockwise from the front
    front = distances[0]
    right = distances[n // 4]
    back = distances[n // 2]
    left = distances[3 * n // 4]
    print("front:", round(front, 3), "right:", round(right, 3), "back:", round(back, 3), "left:", round(left, 3))

C/C++

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

using namespace webots;
using namespace std;

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

  Lidar *lidar = robot->getLidar("lidar");
  lidar->enable(timeStep);
  int n = lidar->getHorizontalResolution(); // Number of points in each layer
  cout << "Points per layer: " << n << " Layers: " << lidar->getNumberOfLayers() << endl;

  while (robot->step(timeStep) != -1) {
    const float *distances = lidar->getLayerRangeImage(0); // One layer, in meters, clockwise from the front
    cout << "front: " << distances[0] << " right: " << distances[n / 4] << " back: " << distances[n / 2]
         << " left: " << distances[3 * n / 4] << endl;
  }

  delete robot;
  return 0;
}

下图是入门机器人在 world1.wbt 中测得的一层数据，从上方绘制，机器人位于中心。周围的墙壁显示为一排排的点。

点云

激光雷达还可以把每个点表示为相对于激光雷达的位置，这对于绘制机器人所见环境的地图很有用。计算点云需要额外的时间，所以只有在用到时才启用它。

Python

from controller import Robot

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

lidar = robot.getDevice("lidar")
lidar.enable(timeStep)
lidar.enablePointCloud()  # Computing the point cloud takes extra time

while robot.step(timeStep) != -1:
    points = lidar.getPointCloud()
    point = points[0]  # Positions relative to the lidar, in meters
    print("x:", round(point.x, 3), "y:", round(point.y, 3), "z:", round(point.z, 3), "layer:", point.layer)

C/C++

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

using namespace webots;
using namespace std;

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

  Lidar *lidar = robot->getLidar("lidar");
  lidar->enable(timeStep);
  lidar->enablePointCloud(); // Computing the point cloud takes extra time

  while (robot->step(timeStep) != -1) {
    const LidarPoint *points = lidar->getPointCloud();
    const LidarPoint &point = points[0]; // Positions relative to the lidar, in meters
    cout << "x: " << point.x << " y: " << point.y << " z: " << point.z << " layer: " << point.layer_id << endl;
  }

  delete robot;
  return 0;
}

放置激光雷达

在你自己的机器人上，请把激光雷达放在顶部，并使用与入门机器人相同的旋转角度，让它保持水平。如果放在车身内部或者倾斜放置，它会测到机器人自己。