ROS机器人底盘(10)-pibot的driver的实现及动态P

pibot的ros中driver

目标

• 串口数据发送与接收
• 订阅cmd_vel topic下发至下位机
• 根据下位机的反馈发布odom topic和odom tf

串口数据发送与接收

  boost::shared_ptr<Transport> trans;
  boost::shared_ptr<Dataframe> frame;

    trans = boost::make_shared<Serial_transport>(bdg.port, bdg.buadrate);
    frame = boost::make_shared<Simple_dataframe>(trans.get());

这里实现一个上位机的Serial_transport和一个Simple_dataframe即可完成

subscribe cmd_vel

cmd_vel_sub = nh.subscribe(bdg.cmd_vel_topic, 1000, &BaseDriver::cmd_vel_callback, this);

void BaseDriver::cmd_vel_callback(const geometry_msgs::Twist& vel_cmd)
{
    ROS_INFO_STREAM("cmd_vel:[" << vel_cmd.linear.x << " " << vel_cmd.linear.y << " " << vel_cmd.angular.z << "]");

    Data_holder::get()->velocity.v_liner_x = vel_cmd.linear.x*100;
    Data_holder::get()->velocity.v_liner_y = vel_cmd.linear.y*100;
    Data_holder::get()->velocity.v_angular_z = vel_cmd.angular.z*100;

    need_update_speed = true;
}

void BaseDriver::update_speed()
{
    if (need_update_speed)
    {
        ROS_INFO_STREAM("update_speed");
        need_update_speed = !(frame->interact(ID_SET_VELOCITY));
    }
}

代码容易理解，订阅消息，回调函数中设置标识，循环中根据标识下发设置指令

publish odom

三轮全向机器人底盘(9)-base_link、odom、map关系中有个odom publisher的例子，基本拿过来就可以

void BaseDriver::update_odom()
{
    frame->interact(ID_GET_ODOM);
    
    ros::Time current_time = ros::Time::now(); 

    float x = Data_holder::get()->odom.x*0.01;
    float y = Data_holder::get()->odom.y*0.01;
    float th = Data_holder::get()->odom.yaw*0.01;

    float vxy = Data_holder::get()->odom.v_liner_x*0.01;
    float vth = Data_holder::get()->odom.v_angular_z*0.01;

    //ROS_INFO("odom: x=%.2f y=%.2f th=%.2f vxy=%.2f vth=%.2f", x, y ,th, vxy,vth);
    
    geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(th);

    //send the transform  
    odom_trans.header.stamp = current_time;  
    odom_trans.transform.translation.x = x;  
    odom_trans.transform.translation.y = y;  
    odom_trans.transform.rotation = odom_quat; 
    odom_broadcaster.sendTransform(odom_trans);  

    //publish the message  
    odom.header.stamp = current_time;  
    odom.pose.pose.position.x = x;  
    odom.pose.pose.position.y = y;  
    odom.pose.pose.orientation = odom_quat;  
    odom.twist.twist.linear.x = vxy;  
    odom.twist.twist.angular.z = vth;  
    odom_pub.publish(odom);
}

动态PID调节

概述

底层提供了各个电机输入输出的，参见协议三轮全向机器人底盘(3)-通讯协议

配置

params.yaml打开out_pid_debug_enable

port: /dev/pibot
buadrate: 115200

base_frame: base_link

# topic
cmd_vel_topic: cmd_vel

#pid debug
out_pid_debug_enable: true

PID曲线

运行roslaunch pibot_bringup bringup.launch
rosrun rqt_plot rqt_plot /motor1_input /motor1_output即可展示出实时曲线

plot

控制之前最好先架起小车

为了稳定给出输入直接向cmd_vel发消息

  x: 0.15
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0" -r 20

观察曲线变化输入输出基本一致输出振幅较小即可；否则打开配置页面
rosrun rqt_reconfigure rqt_reconfigure

config
调整PID参数，重复上一步操作直到输出较为稳定即可