The aim of this chapter is to investigate the effect of vehicle dynamics control systems (VDCS) on both the collision of the vehicle body and the kinematic behaviour of the vehicle's occupant in case of offset frontal vehicle-to-vehicle collision. The study also investigates the full-frontal vehicle-to-barrier crash scenario. A unique 6-degree-of-freedom (6-DOF) vehicle dynamics/crash mathematical model and a simplified lumped mass occupant model are developed. The first model is used to define the vehicle body crash parameters and it integrates a vehicle dynamics model with a vehicle front-end structure model. The second model aims to predict the effect of VDCS on the kinematics of the occupant. It is shown from the numerical simulations that the vehicle dynamics/crash response and occupant behaviour can be captured and analysed quickly and accurately. Furthermore, it is shown that the VDCS can affect the crash characteristics positively and the occupant behaviour is improved in the full and offset crash scenarios.
Top1. Introduction
Complex issues and problems can be easily discussed using the powerful methodology and computer simulation modelling which is the system dynamics. It is widely used to analyse a range of systems in, e.g. business, ecology, medical and social systems as well as engineering (Azar 2012). System dynamics research has been also used for several applications on mechanical engineering field. For example, a dynamic system as adaptive and self-controlling was made to solve the problem of the Active thruster control in AUV (Joshi and Talange, 2016). Another example, to solve the backlash problem, a frequency domain approach is implemented for the control of nonlinear system of any kind such as robotics, mechatronics, other kind of mechanisms, electrical motors etc (Azar and Serrano, 2016). To avoid derailment and hunting, and to improve ride comfort at high speed, forced/active steering bogie design was studied; the actively steered bogie was able to negotiate cant excess and deficiency (Samantaray and Pradhan, 2016).
Vehicle dynamics control systems (VDCS) exist on the most modern vehicles and play important roles in vehicle ride, stability, and safety (Khosravi, 2015). For example, Anti-lock brake system (ABS) is used to allow the vehicle to follow the desired steering angle while intense braking is applied (Yu et al., 2002; Morteza, et al, 2015; Siramdasu and Taheri, 2016). In addition, the ABS helps reducing the stopping distance of a vehicle compared to the conventional braking system. The Active suspension control system (ASC) is used to improve the quality of the vehicle ride and reduce the vertical acceleration (Yue et al., 1988; Alleyne and Hedrick, 1995; Jongsang, et al., 2015; Mirko, et al., 2016; Khan and Qamar, 2015). From the view of vehicle transportation safety, nowadays, occupant safety becomes one of the most important research areas and the automotive industry increased their efforts to enhance the safety of vehicles. Seat belts, airbags, and advanced driver assistant systems (ADAS) are used to prevent a vehicle crash or mitigate vehicle collision when a crash occurs.
To evaluate the crashworthiness, real crash tests or vehicle modelling are carried out. Due to the complexity and the high cost of crash tests, vehicle modelling is commonly used in the first stage of development. Vehicle modelling can be mainly classified as finite element and mathematical modelling. Finite element models of vehicles are increasingly used in preliminary design analysis, component design, and roadside hardware design (Belytschko, 1992). However, finite element modelling is also costly and slow in its simulation analysis. Mathematical modelling produces very quick results and it can be accurately used for unlimited numbers of different types of vehicles in case of vehicle-to-barrier crash tests (Kamal, 1970).
Using mathematical models in crash simulation is useful at the first design concept because rapid analysis is required at this stage. In addition, the well-known advantage of mathematical modelling provides a quick simulation analysis compared with FE models. Vehicle crash structures are designed to be able to absorb the crash energy and control vehicle deformations, therefore simple mathematical models are used to represent the vehicle front structure (Emori, 1968). In this model, the vehicle mass is represented as a lumped mass and the vehicle structure is represented as a spring in a simple model to simulate a frontal and rear-end vehicle collision processes. Also, other analyses and simulations of vehicle-to-barrier impact using a simple mass spring model were established by Kamal (1970) and widely extended by Elmarakbi & Zu (2005, 2007) to include smart-front structures. To achieve enhanced occupant safety, the crash energy management system was explored by Khattab (2010). This study, using a simple lumped-parameter model, discussed the applicability of providing variable energy-absorbing properties as a function of the impact speed.