Product Review: DRC Sensor Head (Hokuyo UTM-30LX-EW LIDAR)

Slide from Kickoff Meeting on Robot Sensor Head

In less than 2-months, software teams will compete in the Virtual DRC.  The top teams will get their own Boston Dynamics Petman/Atlas humanoid!

Big Question: So what comes with the Petman/Atlas robot?  And more specifically, what are the sensors?

Possible Answer: At the October DRC Kickoff Meeting, I snapped a photo of the slide describing the Robot Sensor Head. Apparently a company called Carnegie Robots will provide a MultiSense-SL with the Petman/Atlas.  The DRC website has a datasheet describing this head.  It isn’t very detailed but from looking at the photo, my “best guess” is that the head employs a Hokuyo UTM-30LX-EW LIDAR sensor to provide range data.  I asked some colleagues for their “best guess” and they agree.

Why the Hokuyo UTM-30LX-EW?  First off, a DRC robot needs a suitable sensor to gauge range, and LIDAR (Laser Imaging Detection and Ranging) is a viable choice.  Second, the sensor should be light-weight and operate outdoors.  Looking at Hokuyo’s product line, a photo of the UTM-30LX-EW matches the ones in the DARPA slide and the MultiSense-SL datasheet.

Specifications for the UTM-30LX-EW: (See datasheet)

• About $6000
• Uses Multi-Echo Detection for outdoor usage
• Range of distances: 0.1 to 30 meters
• Accuracy: around 10 mm
• 270 degree field-of-view
• Mass: 210 grams
• Interface connection: ethernet
• Dimensions: Width (63 mm) by Depth (66 mm) by Height (87 mm)

One might know that Willow Garage’s PR2 robot employs a similar LIDAR sensor called the Hokuyo UTM-30LX.  It’s similar to the UTM-30LX-EW but employs USB interfacing and doesn’t have multi-echo detection (and hence not suited for outdoor use).

LIDAR output using the Hokuyo UTM-30LX-EW (right) measuring our surrogate DRC vehicle (left)

Sample Trials Using the Hokuyo UTM-30LX-EW: Our lab acquired one of these sensors.  In the above photo, the sensor captured range data (right) of a golf cart (left).  Here’s a video using the sensor to segment different areas of the vehicle.

Tutorial on the Hokuyo UTM-30LX-EW: A quick Google search doesn’t show much info beyond performance specifications.  So, I had my student (Mr. Karthikeyan Yuvraj) write a “Getting Started” tutorial. He’s working with our DRC partner Prof. Christopher Rasmussen from the University of Delaware.  Below is a photo of his prototype sensor.  One can see the Hokuyo UTM-30LX-EW mounted below the cameras (binocular lens).

Prototyping a sensor head for Team DRC-Hubo

The tutorial assumes knowledge of Linux (Ubuntu) and ROS (Robot Operating System).  The tutorial uses open-source tools like the 3D visualization tool RVIZ.

Summary and Impact to DRC: The Hokuyo UTM-30LX-EW is a relatively affordable sensor that can fit on a DRC robot without taking up much space or consuming much power.  It can operate outdoors and hence meets DARPA’s requirement that all 8-events of the DRC will be held outdoors.

One issue is that the Hokuyo UTM-30LX-EW is only effective in sensing objects between 0.1 to 30 meters. In other words, the robot will be “far-sighted“; it may be able to “see” objects far away (as is the case for vehicle-driving), but not those that are close (as may be the case with handling objects like valves, door-handles, hose-connectors and ladder-rungs).  The net effect is that we must give DRC-Hubo “bifocals” – and hence add sensors (like cameras) for “near-sightedness“.  Alas, our sensor head prototyping continues – stay tuned for more product reviews and tutorials…

Godspeed!