ROS与Arduino-IR Ranger(红外测距仪)

IR Ranger(红外测距仪)

说明

• 这个教程展示通过Arduino和rosserial使用红外测距仪
• 使用sharp IR Ranger 红外测距仪

硬件

• Arduino
• sharp IR Ranger 或其他

连接图

• 确保连接到模拟插脚0

代码

/* 
 * rosserial IR Ranger Example  
 * 
 * This example is calibrated for the Sharp GP2D120XJ00F.
 */

#include <ros.h>
#include <ros/time.h>
#include <sensor_msgs/Range.h>

ros::NodeHandle  nh;
sensor_msgs::Range range_msg;
ros::Publisher pub_range( "range_data", &range_msg);

const int analog_pin = 0;
unsigned long range_timer;

/*
 * getRange() - samples the analog input from the ranger
 * and converts it into meters.  
 */
float getRange(int pin_num){
    int sample;
    // Get data
    sample = analogRead(pin_num)/4;
    // if the ADC reading is too low, 
    //   then we are really far away from anything
    if(sample < 10)
        return 254;     // max range
    // Magic numbers to get cm
    sample= 1309/(sample-3);
    return (sample - 1)/100; //convert to meters
}

char frameid[] = "/ir_ranger";

void setup()
{
  nh.initNode();
  nh.advertise(pub_range);
  
  range_msg.radiation_type = sensor_msgs::Range::INFRARED;
  range_msg.header.frame_id =  frameid;
  range_msg.field_of_view = 0.01;
  range_msg.min_range = 0.03;
  range_msg.max_range = 0.4;
  
}

void loop()
{
  // publish the range value every 50 milliseconds
  //   since it takes that long for the sensor to stabilize
  if ( (millis()-range_timer) > 50){
    range_msg.range = getRange(analog_pin);
    range_msg.header.stamp = nh.now();
    pub_range.publish(&range_msg);
    range_timer =  millis();
  }
  nh.spinOnce();
}

代码解释

1. 代码

#include <ros.h>
#include <ros/time.h>
#include <sensor_msgs/Range.h>

ros::NodeHandle  nh;
sensor_msgs::Range range_msg;
ros::Publisher pub_range( "range_data", &range_msg);

解释:

• 必需包含的头文件
• 实例化节点处理类
• 实例化发布对象

2. 代码

const int analog_pin = 0;
unsigned long range_timer;

/*
 * getRange() - samples the analog input from the ranger
 * and converts it into meters.  
 */
float getRange(int pin_num){
    int sample;
    // Get data
    sample = analogRead(pin_num)/4;
    // if the ADC reading is too low, 
    //   then we are really far away from anything
    if(sample < 10)
        return 254;     // max range
    // Magic numbers to get cm
    sample= 1309/(sample-3);
    return (sample - 1)/100; //convert to meters
}

解释：

• 定义连接的引脚
• 创建定时器变量
• 创建函数用于转换模拟信号为对应的以米计量的距离。

3. 代码

char frameid[] = "/ir_ranger";

解释：

• 创建全局可用的参考系ID

4. 代码

void setup()
{
  nh.initNode();
  nh.advertise(pub_range);
  
  range_msg.radiation_type = sensor_msgs::Range::INFRARED;
  range_msg.header.frame_id =  frameid;
  range_msg.field_of_view = 0.01;
  range_msg.min_range = 0.03;
  range_msg.max_range = 0.4;
  
}

解释：

• Arduino的setup函数，初始变量

5. 代码

void loop()
{
  // publish the range value every 50 milliseconds
  //   since it takes that long for the sensor to stabilize
  if ( (millis()-range_timer) > 50){
    range_msg.range = getRange(analog_pin);
    range_msg.header.stamp = nh.now();
    pub_range.publish(&range_msg);
    range_timer =  millis();
  }
  nh.spinOnce();
}

解释：

• Arduino的loop函数，每50毫秒发布一次红外数据

测试

1. 新窗口打开

$roscore

2. 新窗口打开，/dev/ttyUSB0为设备端口号

$ rosrun rosserial_python serial_node.py _port:=/dev/ttyUSB0

3. 新窗口打开，用rxplot来可视化红外数据

$ rxplot range_data/range