About the 'time stamps' error in ROS

rostime

asked 2017-04-24 20:57:30 -0600

little_bob
88 ●12 ●17 ●25

Hello,I am doing some work on ROS navigation,just at the start，and I encountered some problems.When I roslaunch the *.launch,there are a lot of erros like this:[ERROR] [1493084059.568174116]: Extrapolation Error: Lookup would require extrapolation into the future. Requested time 1493084059.049999952 but the latest data is at time 1493084059.012892115, when looking up transform from frame [odom] to frame [map].It seems that time differences exist during the program running.How can I fix this error or how can I set the time to be the same during the program?

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What launch files are you running? Are you using a simulator or a real robot? What simulator or robot? Is your computer's clock set accurately?

Geoff ( 2017-04-24 21:01:28 -0600 )edit

not a real robot,but a small car based on arduino and raspberry Pi.the name of the launch file ishongrobot_configuration.launch,this may be a launch to set the nodes.Can I upload this file?

little_bob ( 2017-04-25 01:12:54 -0600 )edit

If you are using hardware, then you are using a real robot. Not all robots are made by Kuka! :)

Yes, upload the launch file and the rest of your source so we can check it for problems.

Geoff ( 2017-04-25 01:51:51 -0600 )edit

Are you using running nodes on any computers other than the Raspberry Pi? If you are, then you need to make sure their clocks are synchronised.

Geoff ( 2017-04-25 01:52:42 -0600 )edit

Let's put the file aside.Sorry to forget the details:I run nodes on the raspberrypi to manipulate the arduino to controll the little car and send data of laser_scanner to a Vmware machine(Ubuntu 14.04,bridged to the physical machine) and generating maps with RVIZ.But these errors only happen on the

little_bob ( 2017-04-25 05:19:46 -0600 )edit

RaspberryPi's terminal and maps did exist on RVIZ,but not so correc、explicit.And the car can't be self-navigated.How can I sychronize the time of raspberrypi with the virtualmachine？I baidu and googled these things and doubt about the time.Should I change the codes or just run some commands in the

little_bob ( 2017-04-25 05:25:37 -0600 )edit

terminal?谢谢你的热心帮助。望回复。

little_bob ( 2017-04-25 05:26:05 -0600 )edit

remote refid st t when poll reach delay offset jitter

*ntp1.flashdance 193.11.166.20 2 u 32 64 377 396.120 -29.788 8.509

+ec2-34-198-99-1 192.53.103.108 2 u 42 64 277 278.546 -36.187 8.326

little_bob ( 2017-04-27 02:23:19 -0600 )edit

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really thanks

little_bob ( 2017-04-25 06:17:56 -0600 )edit

Hi,It's me.I found some strange things.Shall I scnchronize the system time of raspberrypi(os:Raspbian:jessie) to the Ubuntu or synchronize the ubuntu systemtime to raspberrypi?Shortly,I mean which is the time server?I install chrony on Ubuntu and did these:sudo nano /etc/chrony/chrony.conf

little_bob ( 2017-04-26 02:25:12 -0600 )edit

add a lineserver 192.168.0.104 minpoll 0 maxpoll 5 maxdelay .05192.168.0.104is the IP address of th Pi.Then,I restarted the chrony and ntpdate,it showed26 Apr 15:23:22 ntpdate[4922]: no servers can be used, exiting.It seems that Pi isn't the server.

little_bob ( 2017-04-26 02:28:01 -0600 )edit

or should I synchronize both of the two's time to the ntpserver:cn.pool.ntp.org?

little_bob ( 2017-04-26 02:30:45 -0600 )edit

You can sync one to the other, but you will need to set up a server on one of them and that's more trouble than it's worth in your case. Sync both of them to the same external server, such as ntp.ubuntu.com.

Geoff ( 2017-04-26 02:33:39 -0600 )edit

Raspbian Jessie apparently also has NTP time sync working out of the box. Does your Raspberry Pi have Internet access?

Geoff ( 2017-04-26 02:35:21 -0600 )edit

yes,with Wifi to the Internet

little_bob ( 2017-04-26 02:48:21 -0600 )edit

Please post the output of ntpq -p on both computers.

Geoff ( 2017-04-26 02:49:52 -0600 )edit

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