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Hi,
has anybody successfully connected to a NXT using ROS (e.g. nxt_lejos or nxt_ros) over remotely?
Which hardware did you use? How much effort did you put into making it work?
Best regards,
Andreas
While I have no personal experience with those sensors/blocks, I can say that nxt_ros only supports the 'standard' sensors/motors that come with the NXT set. Anything else will require you to add support. In theory however, using wifi would allow for (much) higher data rates and ranges. Of course you are still limited to what the brick can do, CPU wise.
The example shown here on the Dexter Industries blog looks promising: the 'only' thing for you to do would be to write a kind of 'proxy', akin to rosserial and nxt_ros itself actually (which is also a proxy). Perhaps nxt_ros could be extended to include support for such a setup.
what I've done in the past is to create a movable 'base' out of Legos, with a laptop / netbook on top. This allows the laptop to function as a wifi-bridge, alleviating the range problem. Bandwidth is still limited, as USB is still used.
What do you mean exactly with 'over wifi'? The brick supports only usb and bluetooth, so I assume you are talking about anything after that? This would then also involve a multi machine ROS setup, with one machine running nxt_ros and some other(s) running a master and other nodes?
If so, this would not be any different from any other multi machine ROS setups. See ROS/Tutorials/MultipleMachines for general setup and here for some Windows details (in case you need it).
Thank you for your reply, ipso. I suppose I didn't make my concern clear enough ;)
The more precise question would've been:
How to use ROS to control mobile Lego Mindstorms robots?
For our next term robotics lab, we're going to teach model based software development using java and mindstorms. As nxt_ros doesn't work properly with bluetooth (due to bandwith limitations), this either implies to build stationary robots only - which is a bit dull - or to find another way to connect nxt_ros or nxt_lejos to the brick remotely.
One options might be one of the available wifi blocks for mindstorms
I'm curious if anybody had similiar issues and how they've solved it and if somebody maybe had experience with external wifi adapters or other hardware solutions.
@andreasw "nxt_ros doesn't work properly with bluetooth (due to bandwith limitations)" Is that the case?
@Peshala: Using a Brick with a contact sensor and a motor, I'm unable to detect any contact as the frequency breaks down to ~0.3Hz. Pressing the touch sensor even for minutes doesn't trigger a single Contact message with contact = true. This may be due to my desired frequency setting though.
@andreasw: just use the nxt_ros tutorials, but over bluetooth. Be sure to adjust the appropriate parameters in the launch files as in the ROS answer mentioned earlier.
The Dexter NXT Wifi Sensor is just that - a sensor. So essentially, you will need to write your own proxy as ipso said, along with a corresponding program on the NXT that will read the "sensor" messages (i.e. whatever custom messages you send over Wifi), and react to control the motors/send back sensors. There is currently no way to connect directly to the NXT's immediate command API connection, as the USB and Bluetooth do.
However, if you're in java already ... there is the Android NXT-Bluetooth SDK.
Thank you for your replies. I supposed we'll develop a nxt_lejos or nxt_ros WiFi proxy for each of the mentioned WiFi Blocks, as I am sick and tired of messing with bluetooth issues ;)
Although I'm still curious whether there are other apporaches to Lego NXT over WiFi besides
Somebody could've tried - for example - to connect the NXT Brick to an android phone using bluetooth and either run android_core on this or use the phone as proxy (gaining access to GPS, a camera etc. alongside).
Best regards, Andreas
Asked: 2012-06-20 04:54:08 -0600
Seen: 2,219 times
Last updated: Jul 04 '12
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