**2. Modelling of a 7DoF heavy vehicle**

In this study, a full vehicle model is developed with the aim to simulate the vehicle's behaviour in lateral direction. The model, developed based on a heavy vehicle, namely, a High Mobility Multipurpose Wheeled Vehicle (HMMWV), is closely related to an armoured vehicle as shown in **Figure 1**. It consists of several

**Figure 2.** *Configuration of the heavy vehicle model [12, 14, 15].*

subsystems in order to simulate the different elements in the vehicle system that contribute to the overall vehicle performance in lateral directions: a 7DoF handling model to simulate the vehicle dynamic responses at its centre of gravity during manoeuvrings; a tyre model in order to simulate all four tyres' behaviour from the road surface interactions; a slip model to calculate the generated slips in lateral and longitudinal directions during driving manoeuvrings, which will be an important input to the tyre model; a load distribution model to estimate the static and dynamic load transfers in longitudinal and lateral directions, which are significant during accelerating, braking, and/or cornering; an engine model; and lastly, a kinematic model to evaluate the vehicle's position relative to the local and global coordinates. The configuration of the overall vehicle model and its respective subsystem is shown in **Figure 2**.

Few assumptions and simplifications are made in developing this model. Firstly, this model focuses mainly on the vehicle responses in lateral and longitudinal directions. Responses and disturbances in vertical direction are considered less significant by assuming an ideal suspension system between vehicles'sprung body, and the vehicle is assumed to travel on even and smooth roads. With these two assumptions, the ride model involving suspension forces and road disturbances is not considered in this model. Next, the vehicle is modelled as a rigid body with concentrated sprung mass at the centre of gravity and four wheels that are connected to each of the vehicle four corners. The vehicle is moving on a level, unbanked, and uninclined road, and therefore, the weight is acting along the *z*-axis. The vehicle body is represented in three-dimensional *x-y-z* planes, which is allowed to displace in lateral and longitudinal directions, as well as rotating about the *z*-axis (yaw). Each of the connected wheels is modelled as a rigid body, which is allowed to rotate about its rotational axis, which is parallel with the vehicle's lateral axis. Only the two front wheels are allowed to steer, which is equipped with an active Pitman arm steering system. Modelling of this system is also considered in this chapter. In calculating the tyre responses, the vertical load on each tyre is calculated using the vehicle's load transfer model by considering the amount of load transfer during manoeuvrings. The load transfer is based on weight distribution in lateral direction during cornering and longitudinal direction during acceleration/braking. To ensure that the model generate response as close as possible to a real condition, rolling and air resistance are considered in this model. In terms of the steering system, the

*Knowledge-Based Controller Optimised with Particle Swarm Optimisation for Adaptive Path… DOI: http://dx.doi.org/10.5772/intechopen.92667*

armoured vehicle is equipped with a Pitman arm steering system where the output steering values were saturated at �10 deg. This is due to the consideration of the system's limitation as well as the controller's stability region that has been tested as described previously [3, 14].

The previous work from the authors has demonstrated the derivations and verifications of this model [12, 15]. Also, several previous studies have been evaluating its controller's performance on the same model [11, 14, 16]. **Figure 1** also shows the symbols and vehicle parameters used in developing the model. Perhaps it is worth noting a common confusion between the fixed global coordinate axes (*X*, *Y*, and *Z*), which are commonly associated with the Earth's longitude, latitude, and altitude, respectively, and the moving local coordinate axes (*x*, *y*, and *z*). This model has been validated by verifying the simulated vehicle responses against the HMMWV responses from a CarSim software as described in detail by Aparow et al. [12]. The verification was done using the standard manoeuvring procedures, namely, Slalom tests, double lane change, and step steer manoeuvrings.
