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How to fix timing issue?

asked 2021-02-08 15:44:30 -0600

sh_ec_ks
1 ●2 ●6 ●7

updated 2021-02-08 15:45:39 -0600

I'm having an issue calculating the change of time that corresponds with values being published by one of my nodes. My calculations of the delta are as follows and I run this function every loop of my subscriber.

void estimate::getTime(){
      now= ros::Time::now().toSec();
       if(last_update>0){
            dt=(now-last_update);
       }
       last_update=now;
}

I have noticed that as I add subscribers to the node i'm working on, I begin to get lots of errors in the delta t. is there some concept I'm missing that is causing this to happen?

Thanks for any help

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answered 2021-02-09 07:36:28 -0600

miura

1908 ●1 ●171 ●24 https://twitter.com/miura

Since last_update>0, (now-last_update) is calculated every time, and both now and last_update are updated in seconds, dt is usually set to 0 (zero).

dt=(now-last_update); itself should be done every time, but it is better to use ros::Time::now() instead of ros::Time::now().toSec().

For example, the following

ros::Time now;
ros::Time last_update;
ros::Duration dt;

void estimate::getTime(){
  now= ros::Time::now();
  dt=(now-last_update);
  last_update=now;
  /* dt.sec : Time difference in seconds */
  /* dt.nsec : Time difference in nanoseconds */
}

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Asked: 2021-02-08 15:44:30 -0600

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Last updated: Feb 09 '21

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