Control Allocation for Multicopter Unmanned Aerial Vehicles

随着机载监控新应用的开发，无人机在民用和商用方面的应用正在激增。ARA Robotics是一家总部位于蒙特利尔的公司，通过为商业应用提供基于多转子的解决方案，利用了这些发展。特别是，ARA目前为建筑工地提供航空摄影测量服务，其中多旋翼飞机被编程通过一系列航路点飞行，以收集这些地点的图像。为了减少这些飞行期间现场操作的停机时间，至关重要的是要尽快执行这些操作。然而，这样做的后果是将飞机上的推进器推到极限，导致需要剪辑电机命令以确保它们在这些限制内运行。这就导致了飞机不可预测和潜在的不安全行为。为了解决非常规飞行中致动器饱和的问题，我们将努力开发一种基于混合器的解决方案，该解决方案结合了推进器的饱和和速率限制。该解决方案将包括实时优化方法，这些方法将优先考虑特定的自由度（dofs），以最大限度地减少执行器饱和对对车辆稳定性和安全性影响最大的自由度的影响。然后将研究第二种方法来开发嵌入执行器和/或运动限制的控制器。将考虑级联控制，其中俯仰和滚转控制将优先考虑并与偏航控制分开执行，只有在执行器未达到限制时才会尝试偏航控制。在此之后，模型预测控制将用于在生成控制命令期间明确考虑执行器的限制。在ARA工程师的协助下，将进行模拟和实验测试，以评估所有这些方法的性能。改进的无人机测量能力将扩大这些小型车辆的应用范围，并将在其他场景中得到应用，例如灾难响应和搜救中的情况评估，这是加拿大在全球舞台上人道主义贡献的关键。

Unmanned aerial vehicles are experiencing a surge in civilian and commercial use as new applications for airborne monitoring are being developed. ARA Robotics is a Montreal-based company that has taken advantage of these developments by providing multi-rotor-based solutions for commercial applications. In particular, ARA currently provides airborne photogrammetry services for construction sites, in which multi-rotor aircraft are programmed to fly through a series of waypoints to collect images of these sites. To reduce downtime of on-site operations during these flights, it is crucial that they be executed as quickly as possible. However, this carries the consequence of pushing the thrusters on the aircraft to their limits, leading to motor commands needing to be clipped to ensure that they operate within these limits. This then leads to unpredictable and potentially unsafe behaviour of the aircraft. To tackle this issue of actuator saturation during unconventional flight, we will work to develop a mixer-based solution that incorporates the saturation and rate limits of the thrusters. This solution will consist of real-time optimization methods that will prioritize particular degrees of freedom (dofs) in order to minimize the impact of actuator saturation on the dofs that have the greatest impact on vehicle stability and safety. A secondary approach will then be investigated to develop a controller which embeds actuator and/or motion limitations. Cascaded control will be considered in which pitch and roll control will be prioritized and performed separately from yaw control, which would be attempted only if actuator limits are not reached. Following this, Model-Predictive Control will be used to explicitly consider actuator limitations during the generation of control commands. Simulations and experimental testing will be performed to evaluate the performance of all these approaches, with the assistance of ARA's engineers. The improved surveying capabilities for drones will broaden the range of applications of these small vehicles and would also have application in other scenarios, such as situation assessment in disaster response and search and rescue, which are key to Canada's humanitarian contribution on the global stage.