Linear electromagnetic actuation system for active vehicle suspension

汽车悬架的基本功能是支撑车辆的重量，最大限度地增加轮胎与路面之间的摩擦，提供良好操控的转向稳定性，并确保乘客的舒适性。汽车运动动力学一般从平顺性和操控性两个角度来考虑，其中隔振、持道和转弯是三个重要问题。汽车悬架系统试图通过(i)在崎岖不平的道路上行驶时吸收能量并在不引起车辆过度振荡的情况下消散能量，（ii）保持车轮几何形状以最大限度地增加轮胎与道路的接触，（iii）在转弯时对汽车的重量作出反应，以尽量减少车身侧倾。虽然汽车悬架经过多年的发展和改进，但三个基本部件仍然是弹簧、减震器和防滚杆。本质上，弹簧吸收了车轮的振荡运动；减震器通过阻尼振动运动来控制不需要的弹簧运动，将悬架运动的动能转化为热能，由液压流体耗散；然后，防侧倾杆提供额外的稳定性，通过抵抗一个车轮相对于另一个车轮的垂直运动，来对抗汽车在转弯时悬架上的侧倾，从而使行驶更加平稳。当然，悬架有很多变化和不同的配置，一辆车通常有不同的前部和后部设计。然而，虽然悬架系统是任何车辆的基本元素，可能看起来相对简单，但设计和实施它们以平衡乘客的舒适性和操控性是一项复杂的任务。软悬架提供了平稳的行驶，但在制动、加速和转弯时导致车身侧倾或俯仰，而硬悬架最大限度地减少了车身运动，允许汽车更积极地行驶，尽管以牺牲行驶质量为代价。为了克服传统悬架系统的局限性，多年来，各种替代悬架技术已经开发出来。例如，流体静力、氢气、液压气动和液压——这是一种以前在赛车运动中被利用的创新。然而，这些也有其局限性和/或过于昂贵的量产车。然而，由于磁性材料、电力电子和数字控制系统的进步，线性电磁机器的最新进展可能会引入一种全新的悬挂技术。这是拟议研究的主题，该研究设想在每个车轮上使用单个直线电机来代替传统的减震器和弹簧系统。采用直线电机的主要好处是，它们可以比传统的基于流体的阻尼悬架系统移动得更快，因此可以足够快地响应，几乎可以消除所有驾驶和道路条件下车身的所有运动和振动，并通过在转弯时自动加强悬架来抵消车身侧倾，从而给驾驶员更大的控制感，从而提高安全性。该研究计划将解决力密集、节能的线性电动机的设计优化以及相关的数学算法，这将是提供悬挂系统所需的主动控制所必需的。开发的悬架技术的实用性将在四分之一的汽车钻机上进行演示，由此产生的车辆性能改进也将通过全范围的驾驶、操控和稳定性模拟来量化。

The basic function of a car suspension is to support the weight of the vehicle, maximise the friction between the tyres and the road surface, provide steering stability with good handling, and ensure the comfort of the passengers. The dynamics of a moving car are generally considered from two perspectives, viz. ride and handling, three important issues being vibration isolation, road holding and cornering. The car suspension system attempts to solve the challenges unique to each, by (i) absorbing energy while travelling over rough roads and dissipating it without causing undue oscillation of the vehicle, (ii) maintaining the wheel geometry to maximise tyre contact with the road, (iii) reacting the weight of the car during cornering, so as to minimise body roll. Although car suspensions have evolved and improved over the years, the three fundamental components remain springs, dampers (shock absorbers) and anti-roll bars. In essence, the springs absorb the oscillatory motion of the wheels; the shock absorbers control unwanted spring motion by damping vibratory motions, the kinetic energy of the suspension movement being converted into heat energy which is dissipated by hydraulic fluid; the anti-roll bars then provide additional stability, combatting the roll of the car on its suspension as it corners, by resisting the vertical movement of one wheel relative to the other, which results in a more level ride. There are, of course, numerous variations and different configurations of suspension, and a car usually has a different design on the front and back. However, whilst suspension systems are a fundamental element of any vehicle and may appear to be relatively simple, designing and implementing them to balance passenger comfort with handling is a complex task. Soft suspensions provide a smooth ride, but result in body roll or pitch during braking, acceleration and cornering, whilst stiff suspensions minimise body motion and allow cars to be driven more aggressively, albeit at the expense of ride quality. To overcome the limitations of conventional suspension systems, over the years, various alternative suspension technologies have been developed. For example, hydrostatic, hydrogas, hydropneumatic and hydraulic - an innovation which has previously been exploited in motorsport. However, these also have their limitations and/or are too expensive for production cars. Recent advances in linear electromagnetic machines, facilitated by advances in magnetic materials, power electronics and digital control systems, may, however, make it possible to introduce a totally new suspension technology. This is the subject of the proposed research, which envisages using a single linear motor at each wheel in place of the conventional shock absorber and spring system. The main benefit of employing linear motors is that they can move much faster than conventional fluid-based damper suspension systems, and can, therefore, respond quickly enough to virtually eliminate all movement and vibration of the body of a car under all driving and road conditions, and to counter body roll, by automatically stiffening the suspension when cornering, thereby giving the driver a greater sense of control and hence improving safety.The research programme will address the design optimisation of force-dense, energy-efficient linear electrical motors and the associated mathematical algorithms which will be necessary to provide the required active control of the suspension system. The utility of the developed suspension technology will be demonstrated on a quarter car rig, and the resulting vehicle performance improvements will also be quantified by simulations over the full range of ride, handling and stability.