# Vehicle-in-the-Loop in Global Coordinates for Advanced Driver Assistance System
## 1 Introduction  
Recently, Advanced Driver Assistance Systems (ADAS) and Autonomous Driving (AD) have been actively developed to increase the convenience and safety of the driver and passengers. The systems that are closely linked to the safety of the driver and the occupant will need to be developed more cautiously [1, 2]. There are effective development tools for each development stage of the vehicle controller. Model-in-the-Loop (MIL) is very useful for quickly verifying and developing algorithms by implementing a controller as a computer simulation model. Software-in-the-Loop (SIL) is usually verified for pseudo-code in a form that can be embedded in an actual automotive controller. Both tests can be simulated faster than real-time, so many scenarios can be verified in a short time. Next, Hardware-in-the-Loop (HIL) validates the actual ECU design and operating characteristics at the hardware level in a laboratory environment. Finally, the verification of the completed system is performed at the actual vehicle stage. In the actual vehicle phase, the most reliable verification is possible, including vehicle dynamic characteristics. For each step, the time required for verification and reliability are regarded as a trade-off relationship, as in Figure 1[2, 3, 4, 5, 6]. Normally, stand-alone vehicle testing after the MIL-SIL-HIL process is acceptable for conventional vehicle controllers--headlamps, wipers and smart keys in a body control system, and Anti-lock Brake System (ABS), Electronic Stabilization Control (ESC) and Electric Power Steering (MDPS) in a chassis control system. In the case of ADAS, however, external environments such as surrounding vehicles, pedestrians, and lanes should be accompanied as a factor in the verification. To overcome these limitations, new approaches have been proposed to validate ADAS. For driver acceptance in the ADAS vehicle, Driver-in-the-Loop (DIL) and Human-and-Hardware-In-the-Loop (H2 IL) are suggested as cyber-physical systems [7; 8]. DIL has conducted a fixed-base driving simulator with TNO PreScan software and is used for testing the human-automation interaction design of the lane-keeping assistance system (LKAS) and adaptive cruise control (ACC). H2 IL has components to generate, operate and communicate with the virtual environment as a driving simulator. It is designed to analyze driving performance and safety affected by V2X communication support. The Vehicle-Hardware-in-the-Loop (VEHIL) is operated on the chassis dynamometer and simulates the surrounding environment with a moving base and a front display device each for a radar and vision sensor [9; 10; 11]. Additionally, the Vehicle-Traffic-Hardware-in-the-Loop (VTHIL) robots validated a radar sensor using a moving base and a commercial vision sensor using a front display device [12]. These can verify the sensor effectiveness, but there is a limit to reflect the own vehicle dynamic characteristics. In addition, the cost of construction and maintenance is high, and it is difficult to reuse and modify the built system when verification is not in accordance with the initial system. Alternatively, building a proving ground for ADAS is suitable for the recognition and judgment of the sensor and the dynamic characteristics of the own, and it can be verified very similarly to the real environment. The proving ground needs a test road dedicated to ADAS and to simulate objects with a robot or a dummy [13; 14]. However, the test road construction and the individual test costs are very high. There is also a high risk of collision by surrounding objects during testing. In order to solve these problems, the Vehicle-in-the-Loop (VIL) technique is emerging to construct and utilize a virtual environment. VIL is a fusion environment of a real testing vehicle in the real-world and a virtual environment, as shown in Figure 2a. It can reflect vehicle dynamics at the same level as the real-world and save the cost of constructing an external environment for system verification.