Unmanned aerial vehicles (UAVs), commonly referred to as drones, are now utilized for capturing images and performing various tasks in outdoor settings. Although there are numerous UAV designs each with distinct benefits and features, most traditional aerial robots are underactuated, meaning they have fewer independent actuators than their degrees of freedom (DoF).
Underactuated systems are typically more cost-effective and can be managed with simpler control strategies compared to overactuated systems, which have more independent actuators than their degrees of freedom (DoF). However, underactuated systems are often less reliable and not as precise in controlling their position and orientation.
Researchers at Tecnalia’s Basque Research and Technology Alliance (BRTA) in Spain have recently created a new overactuated aerial robot capable of independently controlling the position and orientation of its main body. This robot, detailed in a paper published in *Robotics and Autonomous Systems*, features four quadrotors that collaboratively support its central body.
“Our latest paper was driven by the need to extend UAV capabilities beyond mere observation to automate tasks that are currently hazardous or costly, such as working at heights or in remote areas,” said Imanol Iriarte, co-author of the paper, in an interview with TechXplore. “We aimed to develop a system that can actively interact with its environment, performing tasks like load transportation, cooperative construction, contact-based inspection, or infrastructure maintenance.”
The main goal of Iriarte and his team’s recent research was to design an aerial robot with multiple actuators generating thrust, allowing it to independently control the position and orientation of its central body. The resulting robot features a central body connected to four quadrotors through passive universal joints.
“The quadrotors work together to support the main body, allowing for independent control of its six degrees of freedom. This capability enables the robot to execute complex maneuvers and interact more dexterously with its surroundings,” Iriarte explained. “The main advantages of our system include its high control authority, ability to take off and land on inclined surfaces, and its thrust-vectoring capabilities.”
Alongside the aerial robot, the researchers developed a custom control algorithm that translates desired positions and orientations of the main body into angular speed commands for the robot’s 16 propellers. This algorithm also effectively counteracts external disturbances, further improving the robot’s control.
“Our aerial robot can autonomously track the six degrees of freedom of its main body using only passive mechanisms, something conventional underactuated multirotors cannot achieve,” Iriarte said. “The robot’s potential applications are vast, including load transportation, cooperative construction, contact-based inspection, and infrastructure maintenance.”
The team has tested their robot in both simulated environments and real-world outdoor settings. They found that the robot successfully tracked its central body’s six degrees of freedom, a feat beyond the capabilities of conventional UAVs.
In the future, the researchers aim to enhance the robot’s autonomy and performance, as well as explore variations of the design suited to specific tasks.
“In our upcoming studies, we plan to further increase the robot’s autonomy, improve system performance and robustness, and investigate architectural variations tailored for specific applications,” Iriarte added.
