Robots See With Sentek

Feb. 5, 2008

Accurate analysis of a robot’s surroundings requires good sensors. Bill Wong takes a look at the Hokuyo laser range finder in conjunction with Whitebox Robotics’ PC-Bot.

William G. Wong

Sentek Solutions, a provider of sensor solutions for robotics, factory automation and material handling applications, supplied Hokuyo’s URG-04LX laser range finder (Fig. 1). The URG-04LX is a bit pricey at about $2300, but its compact size and performance put it in a category by itself. I tested the URG-04LX with Whitebox Robotic’s PC-Bot and the Player project software (See Real Robots: Player Project). This is one of many applications where the URG-04LX can be used. The URG-04LX is about 5cm by 5cm by 7.1cm. It has a serial interface and a USB interface that looks like a soft COM port. Both deliver a serial stream based on the feedback from the laser range finder unit inside. The range finder operates at about 10Hz and has a 240 degree view. This is typically forward-looking on a robot like the PC-Bot. It has an angular resolution around 0.36 degrees with a distance range on the order of 4m and a resolution of 10mm. It consumes only 2.5W and can run off either the USB power or the connector for the serial interface. The 160g unit is sealed from dust, although it is not waterproof. Utilizing the URG-04LX was actually a trivial exercise because the unit is compatible with the laser range finder for the Player project I had running under Linux on Whitebox Robotic’s PC-Bot. Getting it to work was a matter of matching the Linux device name once the unit was installed. Placement of the unit was actually a more complex issue. Placing the unit on top of the PC-Bot proved easiest (Fig. 2). The downside is that obstacles it detects will essentially be above the unit. This works well for corridors and walls but it is not as good for tables and chairs. I has better success when I placed it on some of the ledges on the front of the PC-Bot – but this reduces the view to about 180 degrees. That’s not a problem with the PC-Bot because it can only move forward or backward or pivot. If you limit movement to forward and pivoting or maintain a map to make backup possible, results are pretty good. Still, the URG-04LX’s detection area is limited to a horizontal slice. The URG-04LX is not cheap but it is extremely accurate and easy to use. Its compact size will make it a good choice for a range of applications and robotics projects. Related Links Hokuyo Player Project Sentek Solutions Whitebox Robotics

About the Author

William G. Wong | Senior Content Director - Electronic Design and Microwaves & RF

I am Editor of Electronic Design focusing on embedded, software, and systems. As Senior Content Director, I also manage Microwaves & RF and I work with a great team of editors to provide engineers, programmers, developers and technical managers with interesting and useful articles and videos on a regular basis. Check out our free newsletters to see the latest content.

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I earned a Bachelor of Electrical Engineering at the Georgia Institute of Technology and a Masters in Computer Science from Rutgers University. I still do a bit of programming using everything from C and C++ to Rust and Ada/SPARK. I do a bit of PHP programming for Drupal websites. I have posted a few Drupal modules.

I still get a hand on software and electronic hardware. Some of this can be found on our Kit Close-Up video series. You can also see me on many of our TechXchange Talk videos. I am interested in a range of projects from robotics to artificial intelligence.