Tethered payload motion control using magnetorheological actuators for aerial vehicles

悬挂式载荷已经在传统直升机上使用了几十年，用于提升重型有效载荷，或无法装入机身的大型有效载荷。有效载荷通常附着在直升机机身下方的一个单钩上，靠近旋翼推力轴。附加在旋翼飞机上的外部载荷会给飞行员或自动控制系统带来重大挑战。首先，对于轻型有效载荷或钝体，如独木舟或太阳能电池板，在高速下可能发生不稳定。其次，远低于机身的有效载荷（“长线”）的动态运动对于飞行员来说可能很复杂，无法在不引起长周期振荡的情况下手动控制。最近，无人驾驶飞机（UAV）行业对悬挂载荷的兴趣有所增加，用于包裹递送，需要在不需要着陆的情况下扔下有效载荷。由于轻型有效载荷更容易受到阵风的影响，这些挑战对于无人机规模的飞机来说应该比全尺寸的直升机更普遍。控制载荷运动的一种方法是耦合两个刚体的动力学。多个系索可以连接到直升机的机头或机尾。这种方法已经提出，但直升机和无人机有非常有限的外力（和力矩），可以安全地应用，任何变化应该是顺利的。由于传统的从机械绞车（串联到系索）的位置控制，这种方法的风险超过了潜在的好处。本研究旨在评估使用磁流变（MR）致动器作为技术推动者的可行性，为全尺寸直升机和无人机大小的飞机提供主动有效载荷运动控制。MR执行器显示出巨大的潜力，因为它们是在张力（或扭矩）中控制的，具有50 Hz的频率响应，并且自然可以过滤力的快速变化。计划进行数值和物理实验。这项研究项目将使加拿大受益，因为它将为加拿大公司Exonetik提供新的商业机会，该公司旨在在未来几年将基于研究结果的产品商业化。************************************************

Slung loads have been use for decades on conventional helicopter to lift heavy payloads, or large payloads that cannot fit inside the fuselage. The payloads are usually attached to a single hook underneath the helicopter fuselage, near the rotor thrust axis. External loads attached to rotary-wing aircraft can pose significant challenges to the pilot or the automated control system. First, instabilities can occur at high speed for light payloads or for bluff bodies, such as a canoe, or solar panels. Second, the dynamic motion of a payload well below the fuselage ("long lines") can be complex for a pilot to control manually without inducing long period oscillations. More recently, a gain in interest for slung loads has been seen from the unmanned aircraft (UAV) industry for the package delivery, where there is a need to drop a payload without the need to land. Since light payloads are more likely to be affected by wind gusts, those challenges should be more prevalent to UAV-scale aircraft than full-size helicopters. One approach to control the payload motion is to couple the dynamics of the two rigid bodies. Multiple tethers could be attached to the nose or tail of the helicopter. Such approach has been proposed, but helicopters and UAVs have very limited external forces (and moment) that can be applied safely, and any changes should be smooth. Due to the conventional control in position from mechanical winches (in series to the tethers) the risk associated with this approach exceed the potential benefits. This research aims at assessing the feasibility of using magneto-rheological (MR) actuators as the technology enabler to provide active payload motion control both for full-scale helicopters and UAV-size aircraft. MR actuators show great potential since they are controlled in tension (or torque), have a frequency response in the order of 50 Hz, and naturally can filter the rapid changes in forces. Both numerical and physical experiments are planned. This research projet will benefit Canada as it will provide new business opportunities for the Canadian company Exonetik, which aims at commercializing the products based on the research results in the coming years.************************************************