Control Input Allocation for Tilting Multirotors - A Review

Tilting multirotor platforms have gained significant attention in the research community due to their over-actuation and input redundancy capabilities. However, these features introduce complex challenges, such as the design of new nonlinear controllers and the use of control input allocation to fully exploit the redundancy of these platforms. A cascaded architecture comprising a high-level controller, a control allocation layer, and a low-level controller to command the actuators and rotors, offers great flexibility and space for co-design. This allows adhoc control allocation approaches to be defined without requiring modifications to the high-level controller. This review analyzes different methods of allocating control inputs presented in the literature and discusses their respective advantages and disadvantages. Furthermore, it categorizes these methods into three distinct classes based on their fundamental characteristics.