Hindawi Journal of Advanced Transportation Volume 2019, Article ID 7308590, 17 pages https://doi.org/10.1155/2019/7308590 Research Article Advanced Modeling and Simulation of Vehicle Active Aerodynamic Safety Krzysztof Kurec ,1 MichaB Remer ,1 Jakub Broniszewski ,1 PrzemysBaw Bibik ,1 Sylwester Tudruj,2 and Janusz Piechna 1 1 Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics, Warsaw 00-665, Poland 2Warsaw University of Technology, Institute of Micromechanics and Photonics, Warsaw 02-525, Poland Correspondence should be addressed to Janusz Piechna; [email protected] Received 3 August 2018; Accepted 6 January 2019; Published 3 February 2019 Guest Editor: Mihai Dimian Copyright © 2019 Krzysztof Kurec et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te aim of this study was to extend the safety limits of fast moving cars by the application, in a controlled way, of aerodynamic forces which increase as the square of a car’s velocity and, if lef uncontrolled, dramatically reduce car safety. Tis paper presents the methods, assumptions, and results of numerical and experimental investigations by modeling and simulation of the aerodynamic characteristics and dynamics of a small sports car equipped with movable aerodynamic elements operated by an electronic subsystem for data acquisition and aerodynamics active automatic control. 1. Introduction such action has drawbacks in the form of car bodies gener- ating aerodynamic lif forces at high speed, together with a Currently, the trend to minimize emissions by limiting decrease in a car’s directional stability and reduction of safety fossil fuel consumption leads to lighter cars with a low limits during fast cornering. Te frailty of the car body shape drag coefcient. Tis situation introduces new challenges is typically compensated by fxed or movable aerodynamic for car designers. Tey need to ensure that stability will be elements activated at high speed. Typically, such aerodynamic good enough to allow safe driving in all road conditions elements have the form of a wing, generating downforce (wind gusts, moving obstacles, etc.). Studies found in the which compensates the lif force generated by the car body. literature mainly focus on sensitivity to lateral wind. Tese Te additional aerodynamic elements generate additional methods attempt to reproduce the test procedure according drag, so it is desirable to activate the movable elements only to the ISO 12021:2010 standard [1]. However, it is rather when necessary. Some sports cars such as, for example, the rare to take into account the coupling of car dynamics and Porsche 918 Spyder [3], have predefned aerodynamic settings aerodynamics. Very ofen, it is assumed that car movement for a specifc range of speeds which make it possible to either will not afect aerodynamic forces. Te study presented in [2] minimize drag or maximize downforce, while the active is in contrast to this assumption. Te authors have shown aerodynamics of the McLaren Senna additionally enables it that the inclusion of a bidirectional fuid structure interac- to shif the aerodynamics balance towards the rear of the car tion can lead to a signifcant change in the aerodynamics to enhance braking. Tese two examples relate to a case when forces. the active aerodynamics is used to support the maneuvers Te development of the quality of highways together with performed by the driver. However, with the increased number the increase in the potential maximum speed of cars has of diferent types of sensors [4] that can be mounted on a car, turned the attention of car designers towards the dynamic it is possible to design a driver assistance system that is able features of cars at high speeds. Te external shapes of cars are to evaluate the current road conditions [5] and automatically typically optimized for low aerodynamic drag. Unfortunately, modify the aerodynamic properties. One example where 2 Journal of Advanced Transportation Analysis Evolution Geometry Preparation Single Physics Coupled Analysis Road Tests Elastic FSI Wind CAD Tunnel CFD FSI Fully Coupled FSI Field Test Dynamic Model One-way FSI Control Figure 1: Scheme of the data fow in the project of vehicle active aerodynamic safety, where CAD is computer aided design, CFD is computer fuid dynamics, and FSI is fuid structure interaction. a driver can be assisted during a rapid maneuver could 2. System of Data Acquisition and Active be the use of machine vision technology to estimate the Control of Movable Aerodynamic Elements road curvature [6] and utilize the driving assistance system to assess not only whether the speed is within the safety A measurement and control system was developed to achieve margin but also whether the vehicle’s aerodynamic setup is the project goals. It was decided that, for research purposes, the most appropriate for the car’s safety. Tis could also give the system should be fexible and easy to modify. Te other the time essential to perform more signifcant movements requirement for the hardware was immunity to vibrations oftheactiveaerodynamicsurfacessothatahighervalue and an ability to work in a broad range of environmental of the aerodynamic forces can be utilized, even before the conditions. For those reasons, an industrial real-time con- driver realizes that some kind of action needs to be taken. troller was selected as the core of the system. Te controller Te introduction of autonomous driving itself can make it was ftted with a set of diferent types of communication possible to increase safety limits during rapid maneuvers [7]. interfaces, which enabled the connection of diferent sensors Te development of such systems needs to rely on model and devices. Te general architecture of the developed system based validation due to the costs and complexity, which is presented in Figure 2. Te whole system is divided into was emphasized by researchers developing a highway pilot three subsystems: the measurement subsystem, the actuation assisting the driver [8]. (control) subsystem, and the user interface. An aerodynamic active control system requires infor- Te measurement subsystem consists of several sensors mation about the actual state of the car, the position of together with their interfaces. In the current confguration, the movable aerodynamic elements located on the car body all the sensors were connected to the system controller and the steering algorithms. Tis paper presents information via RS-232C interfaces. Te main sensor is an integrated about the methods used for modeling and simulation to GPS (Global Positioning System) and AHRS (Attitude and develop an active system extending the safety limits of a Heading Reference System) sensor. Tis sensor provides fast moving car. Te electronic control system is the key to navigation and vehicle state data: linear acceleration, linear the integration of many aspects of scientifc and technical velocity components, inertial position, angular rates, and activity. attitude angles in three perpendicular axes. All the data was It was considered that information can be collected from collected at a frequency of 200 Hz. Te next sensor is the sensors located inside the car and that a set of movable vehicle control measurement sensor. Tis sensor provides aerodynamic elements would be attached to the car body data of the vehicle steering wheel angle and the throttle to form a control loop. Te control part of the system was and brake pedal positions at a frequency of 100 Hz. Tese assumed to be open for programming taking into account two sensors are sufcient for the control of the vehicle information about the characteristics of the sensors, the aerodynamic surfaces. For some parts of this research, the actuators and the aerodynamic characteristics of the added system may also use suspension defection sensors which use aerodynamic elements. Te general scheme of data fow in linear potentiometer sensors in each of the vehicle shock the project is presented in Figure 1. absorbers. Journal of Advanced Transportation 3 Suspension Measurement System RS-232 measure and Actuation System control User Interface Navigation sensor GPS+AHRS Real-Time RS-232 Steering wheel Control Panel angle Ethernet industrial Notebook controller Vehicle control Trottle pedal RS-232 measurement position Brakes RS-485 Servomechanism RS-485 PWM converter Servomechanism RS-485 Servomechanism PWM converter Servomechanism RS-485 Servomechanism PWM converter Servomechanism RS-485 Servomechanism PWM converter Servomechanism Figure 2: Hardware architecture of the measurement and control system. Te actuation subsystem consists of two parts, actua- User interface tion of aerodynamic elements and suspension control. Te System processes Data acquisition communication aerodynamic surfaces are ftted with PWM (Pulse Width Modulation) signal controlled servomechanisms. An RS-485 interface is used to control those servomechanisms and all servomechanisms are connected to the RS-485 control line Control algorithms Actuation Logger via signals converters. All servomechanisms are controlled at afrequencyof20Hz. Te third subsystem is the user interface. Te GUI is Figure 3: System sofware modules. installed on the notebook connected to the system controller via an Ethernet interface. Te GUI allows the operator to observe the measurement data, confgure the controller (diferent modes of operation are possible),