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Rotorigami: A Rotary Origami Protective System for Robotic Rotorcraft

Penelitian - Researchers report the development of a protection system for robotic rotorcraft consisting of a free-to-spin circular protector that is able to decouple impact yawing moments from the vehicle, combined with a cyclic origami impact cushion capable of reducing the peak impact force experienced by the vehicle.

“We report the design and development of a lightweight and cost-effective mechanical impact protection system for miniature quadrotor aerial platforms, and we compare it with traditional rigid propeller protection concepts,” said Pooya Sareh of the Imperial College London in UK.

Penelitian Rotorigami A Rotary Origami Protective System for Robotic Rotorcraft

“The proposed design allows these platforms to remain stable after a variety of normal and oblique collisions that are intolerable with rigid protectors,“ Sareh and team said.

The emergence of rotorcraft aerial robots, popularly known as drones, offers major opportunities for applications in various areas, such as environmental sensing, sampling, and surveillance. Although the potential uses of flying robots are increasing, flying in complex, constrained environments still remains a challenge.

Environments with several potential collision surfaces prove to be major limitations for unmanned aerial operations. To date, research into drone adaptation to cluttered environments has taken two different routes: obstacle detection and avoidance, and mechanical impact resilience.

Conventional approaches are largely focused on obstacle avoidance by using sensors to map the environment and potential collision surfaces. State-of-the art obstacle-avoidance systems have their basis in either vision-aided techniques, such as optical flow, or distance sensors exploiting radar, lidar, and sonar technologies.

A widely used obstacle detection and avoidance method is simultaneous localization and mapping, which builds an accurate map of obstacles by using high-precision onboard sensors.

Other effectively demonstrated methods include collision-recovering controllers along with simple motion planners, enabling robots to navigate without complete knowledge of their surroundings. This technique allows aerial vehicles to fly in dark, Global Positioning System–denied environments.

Mechanical impact resilience is an alternative approach to impact protection. It seeks to cope with collisions rather than to avoid them, which can also complement avoidance-based methods.

It is based on the fact that most conventional flying platforms are generally unable to sustain flight after a collision with a surface, because the disturbance from the impact will likely cause a loss of control and lead to a crash. Traditional drones are not equipped with any impact resilience systems, with collisions often causing failure in the major components of the vehicle.

Oblique collisions will also cause an additional yawing moment around the vehicle’s center of mass, possibly leading to instabilities, further collisions, and crashes, which generally include high impact forces and potential damage to the vehicle. Commercially available mechanical protection concepts are not sufficiently effective and are often based on rigid components that do not mitigate collision forces.

For example, propeller guards made of expanded/extruded polystyrene foam (EPS/XPS) are used as a lightweight and inexpensive solution for the protection of commercial multirotor drones. However, because EPS and XPS are both rigid materials with poor elastic behavior, they are unable to properly cushion impact forces in a recoverable manner.

Collision-resilient robots aim to increase the robustness of flight operations and can be deployed where collisions are unavoidable. Advanced mechanical concepts have been developed to tackle this problem innovatively by mitigating the translational and rotational effects of collisions on the flying platform.

However, in general, these concepts are heavy and cumbersome, severely limiting the flight time and the capability of flying in constrained and narrow spaces. As an example, GimBall outstandingly reduced the impact of friction forces on the attitude of the flying platform but imposed considerable penalties on flight time, versatility, and transportability of the vehicle.

Moreover, it did not cushion impact forces; thus, normal collisions still led to high loads on the vehicle and the colliding object. Mitigating the impact forces in both normal and oblique collisions is a major challenge, especially for very small vehicles for which substantial payload constraints prevent the possibility of using large and heavy protective structures.

Origami engineering can be a solution to address this structural design challenge. Over the past decade, origami (the traditional Japanese art of paper folding) has found numerous novel applications in various areas of robotics.

Because of the wide range of applications of origami engineering, the structural, acoustic, and thermal properties of origami-inspired structures and metamaterials have been of great interest to scientists and engineers.

For example, origami structures have been used as impact protection concepts for potential applications such as novel crash boxes in automotive industry. Furthermore, biological morphing structures, such as insect and bird wings, have inspired the development of origami patterns, typically finite folding patterns with a small number of vertices, as concepts for mechanical flapping wings.

“Because collisions would become more tolerable and because flight speed through complex environments can be limited due to sensing and compensation time scales, the proposed design may allow locomotion at potentially higher speeds,“ said Sareh.

“Impact avoidance strategies can be complemented with the impact resilient nature of the proposed design, leading to a potential reduction in the weight and complexity of the employed onboard sensors,“ Sareh said.

Journal : Pooya Sareh et al. Rotorigami: A rotary origami protective system for robotic rotorcraft, Science Robotics, 26 Sep 2018, DOI:10.1126/scirobotics.aah5228



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