Page - 68 - in Proceedings of the OAGM&ARW Joint Workshop - Vision, Automation and Robotics

3DVisionGuided Robotic Charging Station for Electric and Plug-in Hybrid Vehicles Justinas Misˇeikis1, Matthias Ru¨ther2, Bernhard Walzel3, Mario Hirz3 and Helmut Brunner3 Abstract—Electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) are rapidly gaining popularity on our roads. Besides a comparatively high purchasing price, the main two problems limiting their use are the short driving range and inconvenient chargingprocess. In this paper we address the latter by presenting an automatic robot-basedcharging stationwith3Dvisionguidance for plugging and unplugging the charger. First of all, the whole system concept consisting of a 3D vision system, an UR10 robot and a charging station is presented. Then we show the shape-basedmatchingmethods used to successfully identify and get the exact pose of the charging port. The same approach is used to calibrate the camera-robot system by using just known structure of theconnectorplugandnoadditionalmarkers.Finally, a three-step robot motion planning procedure for plug- in is presented and functionality is demonstrated in a series of successful experiments. I. INTRODUCTION Nowadays it is common to see electric vehicles and plug-in hybrids on our roads. Worldwide plug- in vehicle sales in 2016 were 773600 units, 42% higher compared to 2015 [1]. For example Norway plans to rule out sales of any combustion engine cars by 2025 [4]. However, a new problem being faced by EV and PHEV drivers is having an accessible, fast and convenient battery charging, especially when traveling longer distances. It is a common problem of fast chargers being idly occupied after the car is fully charged if the owner does not return to the vehicle. For example, Tesla has added an additional idle fee to discourage drivers leaving their cars at the chargers for longer than necessary [7]. A solution to avoid this problem and to enable a comfortable fast charging would be an automated robot-based charging system combined with automated car parking. A. Charging Ports and Cables Worldwide, there are many types of EV and PHEV charging ports, as well as different charging port placement locations on the vehicle. Each one of them 1Justinas Misˇeikis is with Department of Informatics, University of Oslo, Oslo, Norwayjustinm@ifi.uio.no 2Matthias Ru¨ther is with Graz University of Technology, Institute for Computer Graphics and Vision, Graz, Austria ruether@icg.tugraz.at 3Bernhard Walzel, Mario Hirz and Helmut Brunner are with Graz University of Technology, Institute for Automotive Engineer- ing, Graz, Austria {bernhard.walzel, mario.hirz, helmut.brunner}@tugraz.at has benefits and detriments, and car manufacturers have not decided on a common standard yet. This introduces an additional inconvenience of finding the correct type of charger, or having to carry a number of bulky adapters. As long as there is no standard, it would be more convenient to let the charging station detect the correct port type and adapt accordingly. Another issue is the current weight and stiffness of a quick charging cable. For example, the weight of a CCS-Type 2 charging cable rated for the power up to 200 kW is 2.26 kg/m and outer diameter of 32 mm. With longer cable lengths, this becomes difficult for people to handle, but would not be an issue for a robot [6]. Cooled charging cables can help to solve thisproblemwithout increasing thecablediameter,but these are not yet standard [17]. B. Existing Automated EVChargingMethods Automatic charging solutions have been researched both in academic and industrial environments. Volks- wagenhaspresentedane-smartConnect system,where a Kuka LBR-iiwa robot automatically plugs in the vehicle after it autonomously parks in a specific target area (allowing for less than 20 cm by 20 cm error). It is also limited to one charging port type [8]. Tesla has demonstrated a concept of a snake-like robot automatically plugging in their EV, however, no technical details on the charging port localisation or robot operation were revealed [9]. The Dortmund Technical University has presented a prototype of the automatic charging system called ALanE. It is based on a robot arm capable of auto- matically plugging and unplugging a standard energy supply to an electric vehicle. The system is controlled via smartphone. However, full capabilities and flexi- bility of this concept system are not clear [3]. The NRG-X concept presents itself as a fully auto- matic charging solution. It can be adapted to any EV or PHEV and is capable of fast charging. Furthermore, it has a tolerance for inaccurate parking positions. The NRG-X system is based on combination of conductive and inductive charging on the under-body of the vehicle, thus an adapter for the vehicle is necessary. Furthermore, in the current concept configuration the charging power is limited to 22 kW [5], which re- sults in over 7 times longer charging compared to 170 kW charging [22] and perspective 350kW [11]. 68