# Driving Safety Improved with Control of Magnetorheological Dampers in Vehicle Suspension
## 5 Conclusions  
The paper is dedicated to the analysis of driving safety for a vehicle model. The applied model was, in detail, referred to an actual, commercially available, and real-size all-terrain vehicle (ATV), additionally equipped with suspension MR dampers. The simulation environment was implemented in C programming language and supported by GNU scientific libraries, including, among others, algorithms for numerically solving differential equations. The original contribution of the manuscript consists of a comprehensive study on vehicle behaviour with respect to driving safety while taking into account interactions between road surface and the vehicle model. The model includes MR dampers which are controlled with standard semi-active control algorithms. The main effort was placed on modelling major phenomena that occur during different road manoeuvres, i.e., tire slip, vehicle body heave and pitch motion, wheel vibration, rolling resistance, and aerodynamic drag. One of the most important issues was to validate the impact of suspension control on the vehicle's behaviour during the typical driving phase, i.e., accelerating,  
Figure 20: Comparison of vehicle handling for different suspension settings: passive, separate and coupled Skyhook control: (**a**) vehicle longitudinal velocity of 5 ms\({}^{-1}\), (**b**) vehicle longitudinal velocity of 10 ms\({}^{-1}\). driving with a constant speed, and braking. For the purpose of research, a half-car vehicle model was implemented, which describes the major behaviour of the vehicle during the mentioned road manoeuvres, i.e., longitudinal and vertical motion and vehicle pitching motion. The proposed half-car model exhibits seven degrees of freedom (DoFs), where the first DoF is related to the longitudinal motion of the vehicle model; next, two DoFs describe the heave and pitch motion of the vehicle body, respectively, and an additional four DoFs are related to wheel vertical and rotational motion. The vehicle model was subjected to the random road-induced excitation in the form of a road profile of class F generated according to the norm ISO 8608. Three different settings of semi-active suspension are tested in the presented study. First, a case of MR dampers that are controlled by different values of constant current is defined, which reflects different soft and hard configurations of passive suspension. Further, two types of Skyhook control are examined, i.e., based on separate control of suspension parts or emulating different damping force exerted on heave and pitch velocities of the vehicle body. A methodology that is related to driving safety was proposed and a comprehensive analysis was presented in frequency domain based on transmissibility and power spectral density characteristics, as well as road holding and vehicle handling indices were defined and discussed. It was shown that properly tuned variants of Skyhook control algorithms improve road holding quality indices for 5 ms\({}^{-1}\) vehicle longitudinal velocity by about 13% (Skyhook-1 DOF) or 11% (Skyhook-2 DOF) for the front wheel and braking, when compared to the passive suspension with zero control current. For the rear wheel and accelerating an improvement of 5% (Skyhook-1 DOF) or 4% (Skyhook-2 DOF) was obtained. In the case of 10 ms\({}^{-1}\) vehicle longitudinal velocity, the following improvement was reached: 19% (Skyhook-1 DOF) and 18% (Skyhook-2 DOF) for the front wheel, and 17% (Skyhook-1 DOF) and 20% (Skyhook-2 DOF) for the rear wheel. The vehicle handling is similarly improved by both algorithms, i.e., 33% (Skyhook-1 DOF) and 31% (Skyhook-2 DOF) tested for constant vehicle longitudinal velocity of 5 ms\({}^{-1}\), 20% (Skyhook-1 DOF) and 21% (Skyhook-2 DOF) for vehicle longitudinal velocity of 10 ms\({}^{-1}\). The Groundhook control of the separate suspension parts was also implemented and tested. However, its improvement with respect to road holding and vehicle handling indices was only slightly visible.