Combining exteroceptive sensors aboard a UGV


This initial blog post will discuss the use of exteroceptive sensor systems aboard the Daredevil PackBot unmanned ground vehicle (UGV) to navigate in all weather conditions, as outlined in Yamauchi’s paper titled “Fusing Ultra-Wideband Radar (UWB) and LIDAR for Small UGV Navigation in All-Weather Conditions.”
Yamauchi’s research into the use of UWB radar and LIDAR builds upon previous research that showed UWB radar was capable of detecting objects “in a snowstorm, through dense fog, and through sparse foliage” (2010).  However, the use of radar is not as accurate as LIDAR or visual navigation techniques, reducing the speed at which the UGV can operate.  The use of a calibrated max filter algorithm addressed issues experience differentiating between ground clutter returns and obstacles, but remained unable to match the accuracy of LIDAR or stereo vision sensors. 
Yamauchi, Brian. (2010). Daredevil Packbot [digital image]. doi: 10.1117/12.850386
Advantages to the incorporation of UWB radar were evident when the detection capabilities of radar, LIDAR, and stereo vision ranging were compared between a room filled with clear air and a room filled with dense fog.  While the visual and LIDAR sensors produced the most accurate depiction of the room in clear air, they were completely obscured by the fog.  Performance of the UWB radar was unaffected in the foggy environment. 

Yamauchi, Brian. (2010). RADAR/LIDAR Experiments [digital image]. doi: 10.1117/12.850386

Rather than trying to combine the inputs of all three sensor capabilities into one navigational program, Yamauchi combined the use of LIDAR and stereo vision ranging for unobstructed viewing situations, while utilizing UWB radar for situations when fog was present.  This was accomplished by switching to radar as a means of navigation whenever all LIDAR returns were less than two meters (Yamauchi refers to this method as automatic fog detection).  This method of switching between the most ideal sensing situation given environmental conditions increased overall system performance in all conditions when compared to the use of a singular sensor system.   

As mentioned at the beginning of this post, the navigational sensors and processes summarized above represent the use of exteroceptive sensor systems to obtain a sense of the environment surrounding the UGV.  In this instance, active and passive sensor systems are utilized in harmony to provide the most suitable system given environmental conditions.  While LIDAR (active) and stereo vision (passive) are utilized in clear air, UWB radar (active) is utilized when LIDAR and stereo vision are ineffective.  This novel method enables the UGV to navigate in all conditions and will likely see further development for battlefield or rescue operations.
Reference:

Yamauchi, Brian. (2010).   Fusing ultra-wideband radar and lidar for small UGV navigation in all-weather conditions. Proceedings of SPIE. 7692. doi: 10.1117/12.850386


Comments

  1. UnknownNovember 22, 2017 at 5:18 PM

    John, I enjoyed reading your blog it was very informative As a caveat I like to say that I believe that one of the most important things about the future of sensors is minimizing the size so that all unmanned vehicles can have more sensing capability while simultaneously taking away the hurdle of not having enough space to fit them.

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  2. RachaelNovember 22, 2017 at 5:23 PM

    Jon,

    Nice post! Very interesting, navigation in all-weather conditions is certainly a challenge. I think a hybrid solution using LiDAR and radar is a promising concept but I know there have been some other promising innovations that also may solve the detect and avoid problem for UAVs. Have you read about Echodyne's metamaterial radar arrays? ( https://echodyne.com/ )

    Echodyne's radar unit is made out of a metamaterial that manipulates electromagnetic waves in a unique way that mimics the phased-array radar systems that the military uses, at a fraction of the cost and size (Ackerman, 2016). The material has been developed to be able to physically manipulate electromagnetic waves in order to steer the antenna's beam. You can see how a UAV navigates using this sensor in a early test video:
    https://www.youtube.com/watch?v=OGy9sDNMm2Q

    By using this metamaterial to construct its radar unit, Echodyne has been able to produce a high functioning unit at 1/10 of the cost of comparable units (phased array radar) that are used in the military’s combat jets and is aiming to reduce the cost even more (Ackerman, 2016).

    Great post, I enjoyed reading it!
    Respectfully,
    Rachael

    Ackerman, E. (2016, Nov 8). Metamaterial Radar is Exactly What Delivery Drones Need. Retrieved from: http://spectrum.ieee.org/automaton/robotics/drones/metamaterial-radar-is-exactly-what-delivery-drones-need

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