Flying Modular Structures offer a versatile mechanism that can change the arrangement of constituent actuators according to task requirements. In this work, we extend a modular aerial platform that can expand its actuation capabilities depending on the configuration. Each module is composed of a quadrotor in a cage that can rigidly connect with other modules. The quadrotor is connected with the cage by a revolute joint that allows it to rotate with respect to the cage. Modules located in the structure are either parallel or perpendicular to one another. The task specification defines forces and moments needed during the execution. We propose two search methods to find a configuration that can satisfy the specification. The first approach consists of an exhaustive search that yields optimal structure configurations by exploring the whole search space. The second approach proposes a heuristic based on subgroup search, reducing the problem complexity from exponential to linear. We validate our proposed algorithms with several simulations. Our results show that the proposed heuristic is computationally efficient and finds a near-optimal configuration even for flying modular structures composed of a large number of modules.

In this work we introduce ModQuad-DoF, a modular flying robotic structure with enhanced capabilities for yaw actuation. We propose a new module design that allows a one degree of freedom relative motion between the flying robot and the cage, with a docking mechanism allowing rigid connections between cages. A novel method of yaw actuation that increases the structure control authority is also presented. Our new method for the structure yaw control relies on the independent roll angles of each one of the modules, instead of the traditional drag moments from the propellers. In this paper, we propose a controller that allows the ModQuad-DoF to control its position and attitude. In our experiments, we tested a different number of modules flying in cooperation and validated the novel yaw actuation method.

Flying modular robots have the potential to rapidly form temporary structures. In the literature, docking actions rely on external systems and indoor infrastructures for relative pose estimation. In contrast to related work, we provide local estimation during the self-assembly process to avoid dependency on external systems. In this paper, we introduce ModQuad-Vi, a flying modular robot that is aimed to operate in outdoor environments. We propose a new robot design and vision-based docking method. Our design is based on a quadrotor platform with onboard computation and visual perception. Our control method is able to accurately align modules for docking actions. Additionally, we present the dynamics and a geometric controller for the aerial modular system. Experiments validate the vision-based docking method with successful results.

We present a novel flying modular platform capable of grasping and transporting objects. It is composed of four cooperative identical modules where each is based on a quadrotor within a cuboid frame with a docking mechanism. Pairs of modules are able to fly independently and physically connect by matching their vertical edges forming a hinge. Four one degree of freedom (DOF) connections results in a one DOF four-bar linkage that can be used to grasp external objects. In this paper, we propose a decentralized method that allows the Flying Gripper to control its position, attitude and aperture angle. In our experiments, we tested the hovering performance for different aperture angles and with a grasped object. The performance for a closing and opening motion was also verified.

We introduce ModQuad, a novel flying modular robotic structure that is able to self-assemble in midair and cooperatively fly. The structure is composed by agile flying modules that can easily move in a three dimensional environment. The module is based on a quadrotor platform within a cuboid frame which allows it to attach to other modules by matching vertical faces. Using this mechanism, a ModQuad swarm is able to rapidly assemble flying structures in midair using the robot bodies as building units. In this paper, we focus on two important tasks for modular flying structures. First, we propose a decentralized modular attitude controller to allow a team of physically connected modules to fly cooperatively. Second, we develop a docking method that drives pairs of structures to be attached in midair. Our method precisely aligns, and corrects motion errors during the docking process. In our experiments, we tested and analyzed the performance of the cooperative flying method for multiple configurations. We also tested the docking method with successful results.

Recent work in the field of bio-inspired robotic systems has introduced designs for modular robots that are able to assemble into structures (e.g., bridges, landing platforms, fences) using their bodies as the building components. Yet, it remains an open question as to how to program large swarms of robotic modules so that the assembly task is performed as efficiently as possible. Moreover, the problem of designing assembly algorithms is compounded by the scale of these systems, and by the lack of centralized guidance in unstructured environments. The main contribution of this work is a decentralized algorithm to assemble structures with modular robots. Importantly, we coordinate the robots so that docking actions can be parallelized. We show the correctness of our algorithm, and we demonstrate its scalability and generality through multiple scenarios in simulation. Experiments on physical robots demonstrate the validity of our approach in real-world settings.