Unable to properly set up Odometer [closed]

asked 2020-11-21 11:18:53 -0600

Robot_fox gravatar image

Hello, I am using ROS NOETIC on Ubuntu mate 20.04. I am using an arduino mega, rover 5 platform (link text ) that has 2 encoders and motors that i am using. I am trying to send the data collected by the encoders to ros via Rosserial_arduino. I was able to get the data collected but when ran on RVIZ to see how the distance traveled from its starting position, it is going in a circle. It should be going straight because both motors are moving in the same direction at the same speed. Is there something I'm missing? Should i use the nav_msg/Odometry instead? Also for anybody using slam toolbox, do i only need the odometry data to finally start using it properly?

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#include <Encoder.h>
#include <ros.h>
#include <ros/time.h>
#include <tf/tf.h>
#include <tf/transform_broadcaster.h>
#include <math.h>

//DC Motor inputs
const int left_dir=12;
const int left_brake=9;
const int right_dir=13;
const int right_brake=8;

//Setting up Ros
ros::NodeHandle  nh;
geometry_msgs::TransformStamped t;
tf::TransformBroadcaster broadcaster;
char base_link[] = "/base_link";
char odom[] = "/odom";

//Using Encoder library to specify which pins are being used 
Encoder L_Enc(19, 18);
Encoder R_Enc(20,21);

// paramters of robot in mm
float Pi=3.14;
float dia=60;   //diameter 
float ER= 333; // Number of ticks per one full revolution 
float b= 183;
float Dl, Dr, Dc, Ori_ch,Dl_old,Dr_old,x_cor,y_cor;
float Ori  = 0;  //orientation
float x = 0;           
float y = 0; 
float deltaL;
float deltaR;
float L_oldPosition  = 0;
float R_oldPosition  = 0;

//make both dc motors move forward then stop 
void forward_move() {

void setup() {
  // put your setup code here, to run once:


void loop() {
  //Left this function a comment when not using motors

  //changes in distance traveled by motor set to zero in beginning 

  //Reads the number of ticks  odometer  in each motor
  float R_newPosition = L_Enc.read();
  float L_newPosition = R_Enc.read();

  //If there is a change in ticks for either odometer 
  if (L_newPosition != L_oldPosition) {

    //Converts ticks into distance (Circumference * ticks/resolution) for previous distance
    Dl_old= Pi * dia * (L_oldPosition/ ER);

    L_oldPosition = L_newPosition;

    //Converts ticks into distance (Circumference * ticks/resolution) for previous distance
    Dl= Pi * dia * (L_newPosition/ ER);

    //calculates change in distance 


  if (R_newPosition != R_oldPosition) {
    Dr_old= Pi * dia * (R_oldPosition/ ER);
    R_oldPosition = R_newPosition;

    Dr= Pi * dia * (R_newPosition/ ER);


  // calculates position
  if ((deltaR!=0)||(deltaL!=0)){

    //Where the center of the rover is 
    Dc=( Dl + Dr) /2 ;

    // Using triangle rule, finds orientation 
    Ori_ch=(Dr - Dl)/b; 

    //if change in orientation, adds it to the previous orientation
    Ori = Ori + Ori_ch;

    // X and y position of rover in mm
    x = x + Dc * cos(Ori);
    y = y + Dc * sin(Ori);

    //Since the distance travel is very small and ...
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Closed for the following reason the question is answered, right answer was accepted by Robot_fox
close date 2020-11-22 20:22:23.295836


What was the answer? I don't see it.

gvdhoorn gravatar image gvdhoorn  ( 2020-11-23 02:52:21 -0600 )edit