webots学习笔记

webots 笔记

第一天 Con t roll e r Pro g ram ming

开始

#include <webots/xyz.h> 头文件表示We bot s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We b o ts 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 fo r 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。

/*

 * File:          hello_world.c
 * Date:
 * Description:
 * Author:
 * Modifications:
   */

/*

 * You may need to add include files like &lt;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;
}