Vehicles that are capable of driving on and off paved or gravel surface are referred to as off-road vehicles. In general, these vehicles are characterized by having large tyres with deep, open treads and a flexible suspension, or even caterpillar tracks. Other types of vehicles that do not travel on public streets or highways are generally referred to as off-highway vehicles, which would include cranes, tractors, bulldozers, backhoes and forklifts (Faris et al, 2009a; http://en.wikipedia.org/wiki/Off-road_vehicle). Unlike a road vehicle, an off-road vehicle is subjected to ride vibrations of low frequency and large amplitude, which cause bodily discomfort to the operator, and limit the mobility and performance of the vehicle (Srivinasa et al., 2003). Generally, the speed of off-road vehicles over rough terrain is determined by the ride quality not by the engine power. For this reason, researches are currently being undertaken to improve the ride dynamics of these vehicles using an advanced suspension system. In recent years, a lot of studies, analyses, and optimizations have been conducted in the area of semi-active suspension systems for multiple-axle off-road vehicle. Among the most recently published are by Faris et al., (2009) who performed analysis of semi-active suspension systems for four-axles off-road vehicle using half-car model and by BenLahcene et al., (2009) who compared the performance of two-axle, three-axle, and four-axle off-road vehicles. Therefore, to further improve the ride quality of the off-road vehicles, it is logical that the next step is to introduce an active element to the systems. A lot has been reported on the control strategies of an active suspension system for a passenger car, which basically falls under the category of active vibration isolation. Linear and fuzzy logic controllers are among popular controllers used for the active suspension system. Sam et al. (2000) have analyzed the aspects of passive and active suspension with focus on the ride quality improvement by implementing Linear Quadratic Regulator (LQR) control scheme to control an actuator in active suspension using a quarter-car model. The result shows that an active suspension gives a better performance in terms of comfort ride compared to the passive suspension and also increases a tyre-to-road contact thus making the vehicle more stable. Sam et al., (2000) concluded that LQR controller can be considered one of the solutions for excellent ride comfort and good handling of cars.
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机译：能够铺设或砾石表面驱动的车辆被称为越野车辆。通常，这些车辆的特征在于具有大的轮胎，具有深，开放的胎面和柔性悬架，甚至毛毛虫轨道。其他类型的车辆，不在公共街道或高速公路上旅行的车辆通常被称为偏远车辆，包括起重机，拖拉机，推土机，反向和叉车（Faris等，2009a; http：//en.wikipedia。 org / wiki / off-load_vehicle）。与公路车辆不同，越野车辆经受低频和大振幅的振动，这导致操作者的身体不适，并限制车辆的移动性和性能（Srivinasa等，2003）。通常，粗糙地形上的越野车辆的速度由不由发动机功率的乘坐质量决定。出于这个原因，目前正在使用先进的悬架系统来改善这些车辆的乘坐动态。近年来，在多轴越野车辆的半主动悬架系统面积中，已经进行了大量的研究，分析和优化。最近发表的是Faris等，（2009），使用半汽车模型和Benlahcene等人的四轴越野车辆的半主动悬架系统进行了分析，（2009）双轴，三轴和四轴越野车的性能。因此，为了进一步提高越野车辆的乘坐质量，是逻辑的，下一步是向系统引入有源元素。已经报告了乘用车主动悬架系统的控制策略，基本上属于主动振动隔离类别。线性和模糊逻辑控制器是用于主动悬架系统的流行控制器。萨姆等人。 （2000）通过实施线性二次调节器（LQR）控制方案来分析被动和主动悬架的各个方面，重点通过实施线性二次调节器（LQR）控制方案来使用四分之一车模型控制主动悬架中的致动器。结果表明，与无源悬架相比，活性悬架在舒适骑行方面具有更好的性能，并且还增加了轮胎到道路接触，从而使车辆更稳定。 Sam等人，（2000）得出的结论是，LQR控制器可被认为是优良的乘坐舒适和良好的汽车的解决方案之一。
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