webots学习笔记

webots 笔记

第一天 Controller Programming

开始

#include <webots/xyz.h> 头文件表示Webots的一个节点。

• 代码也可以包含C语言的标准库，比如 #include <stdio.h>。

• wb_robot_init()是C语言API 的初始化函数。就是用C语言来编写控制器的话用这个函数来进行初始化

  • 该函数初始化控制器与Webots之间的通信，并且仅在C语言里存在。

• 最高层的控制代码一般写在 for 或者 while 循环里。在此循环里调用wb_robot_step()函数。

  • 该函数需要在所有控制器中出现，它让程序有规则的时隔。
  • 它会运算32ms的仿真后反馈。这里的时间并不是实际的时间，它会是毫秒或者一分钟对应的CPU时间。

• 实例

  /*
  
   * File:          hello_world.c
   * Date:
   * Description:
   * Author:
   * Modifications:
     */
  
  /*
  
   * You may need to add include files like <webots/distance_sensor.h> or
   * <webots/motor.h>, etc.
     */
     #include <webots/robot.h>
     #include <stdio.h>
  
  /*
  
   * You may want to add macros here.
     */
     #define TIME_STEP 64
  
  /*
  
   * This is the main program.
   * The arguments of the main function can be specified by the
   * "controllerArgs" field of the Robot node
     */
     int main(int argc, char **argv) {
       /* necessary to initialize webots stuff */
       wb_robot_init();
  
    /*
  
     * You should declare here WbDeviceTag variables for storing
     * robot devices like this:
     * WbDeviceTag my_sensor = wb_robot_get_device("my_sensor");
     * WbDeviceTag my_actuator = wb_robot_get_device("my_actuator");
       */
  
    /* main loop
  
     * Perform simulation steps of TIME_STEP milliseconds
     * and leave the loop when the simulation is over
       */
  
    while(1){
      printf("Hello World!n");
      wb_robot_step(32);
    }
    //while (wb_robot_step(TIME_STEP) != -1) {
      /*
       * Read the sensors :
       * Enter here functions to read sensor data, like:
       *  double val = wb_distance_sensor_get_value(my_sensor);
       */
  
      /* Process sensor data here */
      
      /*
       * Enter here functions to send actuator commands, like:
       * wb_motor_set_position(my_actuator, 10.0);
       */
  
    //};
  
    /* Enter your cleanup code here */
  
    /* This is necessary to cleanup webots resources */
    wb_robot_cleanup();
  
    return 0;
  }
  

传感器读取

• 先使用设备（device）之前， 必须要给定相应的设备（device）标签。Wb_Device_Tag

  • 该标签调用wb_robot_get_device(”string“)。
  • 该标签是隐含类型，它在控制代码里用于识别设备或者装置。
  • string代表设备名称。
  • 如果该机器人没有此设备就返回 0 。

• 每个传感器必须使用之前被打开，相应的函数为wb_*_enable()。这里的星号表示传感器的类型。

  • 每个传感器的数据都以毫秒为单位更新。
  • 一般情况下更新数据的延迟是跟控制步伐（TIME_STEP）相似，因为它是每个wb_robot_step()运行后被更新。
  • 这个时隔也可以选择为两个step，越大的更新延迟可以提高仿真速度，比如相机。
  • 关闭函数为wb_*_disable()。

• 传感器值是调用wb_robot_step()函数的时候更新的。比如用wb_distance_sensor_get_value()找回最新值。

• 一些传感器的标签如下：

  1 const double *wb_gps_get_values(WbDeviceTag tag);//GPS定位
  2 const double *wb_accelerometer_get_values(WbDeviceTag tag);//加速度传感器
  3 const double *wb_gyro_get_values(WbDeviceTag tag);//陀螺仪
  

• GPS传感器的使用实例

  const double *pos = wb_gps_get_values(gps);
  
  //OK, to read the values they should never be explicilty deleted by the controller code.
  
  printf("MY_ROBOT_is_at_position:%g %g %gn", pos[0],pos[1],pos[2]);
  
  //OK, to copy the values
  double x,y,z;
  x = pos[0];
  y = pos[1];
  z = pos[2];
  
  //OK, another wa to copy the values
  double a[3] = {pos[0],pos[1],pos[2]};
  
  //OK, yet another wa to copy these values
  double b[3];
  memcpy(b,pos,sizeof(b));
  
  

  • 一些不对的用法

    const double *pos = wb_gps_get_values(gps);
    
    pos[0] = 3.5;         //ERROR: assigment of read-only location
    double a = pos[3];    //ERROR: index out of range
    delete [] pos;        //ERROR: illegal free
    free(pos);            //ERROR: illegal free
    

• 实例

  /*
   * File:          distance_sensor.c
   * Date:
   * Description:
   * Author:
   * Modifications:
   */
  
  /*
   * You may need to add include files like <webots/distance_sensor.h> or
   * <webots/motor.h>, etc.
   */
  #include <webots/robot.h>
  #include <webots/distance_sensor.h>
  #include <stdio.h>
  
  /*
   * You may want to add macros here.
   */
  #define TIME_STEP 32
  
  /*
   * This is the main program.
   * The arguments of the main function can be specified by the
   * "controllerArgs" field of the Robot node
   */
  int main(int argc, char **argv) {
    /* necessary to initialize webots stuff */
    wb_robot_init();
  
    /*
     * You should declare here WbDeviceTag variables for storing
     * robot devices like this:
     *  WbDeviceTag my_sensor = wb_robot_get_device("my_sensor");
     *  WbDeviceTag my_actuator = wb_robot_get_device("my_actuator");
     */
    WbDeviceTag ds = wb_robot_get_device("my_distance_sensor");
    wb_distance_sensor_enable(ds, TIME_STEP);
    
    while(1){
      wb_robot_step(TIME_STEP);
      double dist = wb_distance_sensor_get_value(ds);
      printf("sensor value is %fn", dist);
    }
  
    /* main loop
     * Perform simulation steps of TIME_STEP milliseconds
     * and leave the loop when the simulation is over
     */
    //while (wb_robot_step(TIME_STEP) != -1) {
      /*
       * Read the sensors :
       * Enter here functions to read sensor data, like:
       *  double val = wb_distance_sensor_get_value(my_sensor);
       */
  
      /* Process sensor data here */
  
      /*
       * Enter here functions to send actuator commands, like:
       * wb_motor_set_position(my_actuator, 10.0);
       */
    //};
  
    /* Enter your cleanup code here */
  
    /* This is necessary to cleanup webots resources */
    wb_robot_cleanup();
  
    return 0;
  }
  

代码007普通

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