Unmanned Systems Technology 025 | iXblue DriX I Maintenance I UGVs I IDEX 2019 I Planck Aero Shearwater I Sky Power hybrid system I Delph Dynamics RH4 I GCSs I StreetDrone Twizy I Oceanology Americas 2019

88 Digest | StreetDrone Twizy a given time interval, to estimate rpm and therefore vehicle speed. Atop the vehicle is a 360° Lidar, typically a Velodyne VLP-16 Puck system, although the company is building a Twizy that uses an RS-Lidar-16, another 16- beam 3D unit, from Robosense. The latter weighs 840 g, has a measurement range of up to 150 cm and an rpm range of 300 to 1200. Both sensors have a vertical FOV of +15.0° to -15.0°, a vertical angular resolution of 2.0°, a horizontal angular resolution of roughly 0.1° to 0.4°, an update rate of 5-20 Hz, and an operating temperature range of -10 C to +60 C. “None of our customers have requested more than just the one Lidar, but the actual bodywork has been designed to handle up to three,” O’Sullivan says. “Having our own internal production facility means the bodywork is entirely adaptable in-house – if customers particularly want, say, a nose cone Lidar for some reason then we can do that. We can quickly prototype that and get it integrated.” In addition, a radar (from a company such as SmartMicro or Continental) is sometimes integrated into the front of the Twizy if a customer requests it. As well as fastening it to the bumper, the mount also contains the braking motor. For vision, a total of eight cameras are fitted around the Twizy – three at the front, one at the rear and two on each side. “So far, most of our customers have gone for gigabit multimedia serial link [GMSL] cameras because they’ve been using the Nvidia Drive PX2 for their computing,” explains O’Sullivan. “We are now integrating other types of cameras too, particularly following requests for power-over-Ethernet [PoE] cameras and systems from Point Grey and Basler. The range of computer power available has changed, so we can change to other interfaces as well.” The advent of PoE has improved StreetDrone’s bandwidths for accruing self-driving data while also reducing the number of cables and interfaces needed to run between the cameras and to the power and computer systems. The front vision sensors typically consist of two 60° cameras and one 120° camera, oriented in a line across the front of the vehicle’s roof with the 120° system in the middle and the 60° ones on either side for stereo vision. This architecture arose following early experimentation, when StreetDrone’s engineers found that the 60° cameras didn’t always provide a high enough vertical FOV to see traffic lights when halting directly in front of them, creating the need for the 120° optical sensor in the middle. The remaining five cameras are all 120° FOV. “Using GMSL cameras means the actual connector is quite ‘tamper-proof’: it’s a Fakra connector so it essentially locks in place,” O’Sullivan notes. “If you’re looking to develop SAE Level 4 and 5 systems, where the driver really has to be hands-off, you can’t risk any connections breaking, regardless of speed, vibrations or bumps.” Lastly, six or more ultrasound sensors are integrated via the CAN bus, typically with two each at the front and rear, and one on either door. Navigation Although the GNSS and IMU can be selected and configured for end-user requests, the base StreetDrone Twizy features a PCAN-GPS module from PEAK- System, which integrates an NXP LPC4000 series processor (with an ARM Cortex-M4 core) and magnetometer alongside its GNSS receiver, accelerometer and gyroscope. It is also programmable via the CAN interface. “Some of our customers want to understand the vehicle dynamics more closely, so they want higher-precision GPS and IMU systems,” O’Sullivan says. “Some have requested USB interfaces, but for the most part the PCAN-GPS has proved to be cost-effective in terms of accuracy and developer accessibility.” The system’s satellite receiver is a u-blox MAX-7W, which is compatible with the GPS, Galileo, GLONASS, QZSS and SBAS constellations. The triple-axis accelerometer and magnetometer April/May 2019 | Unmanned Systems Technology A nose cone on the Twizy’s front bumper contains the braking motor and the radar, although the latter is not always requested by StreetDrone’s customers