Perching onto objects can allow flying robots to stay at a desired height at low or no cost of energy. This paper presents a novel passive mechanism for aerial perching onto smooth surfaces. This mechanism is made from a bistable mechanism and a soft suction cup. Different from existing designs, it can be easily attached onto and detached from a
surface, but it can also hold a large weight when attached to a surface. Further, the mechanism can still work when the suction cup is not precisely aligned with the surface,
alleviating the requirement for precise motion control of flying robots. The attachment and detachment are facilitated by the bistable mechanism, while the strong holding is enabled by a locking mechanism that can disable the bistable mechanism. We conduct experiments to characterize the required forces for successful attachments and detachments. We also equip the perching mechanism onto a quadcopter to demonstrate it can be successfully used for perching onto smooth surfaces (e.g., glass).
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A Mechanically Intelligent and Passive Gripper for Aerial Perching and Grasping
Perching onto an object (e.g., tree branches) has recently been leveraged for addressing the limited flight time for flying robots. Successful perching needs a mechanical mechanism to damp out the impact and robustly grasp the object. Generally, such a mechanism requires actuation for grasping. In this article, we present a fully passive mechanism without using any actuator: a mechanically intelligent and passive (MIP) gripper that can be used for either aerial perching or grasping. Initially open, the gripper can be closed by the impact force during perching. After closure, if a sufficient mass (e.g., the robot’s mass) is applied, the gripper can switch to a holding state and maintain that state to hold the mass. Once the mass is removed, the gripper can automatically open. We establish static models for the gripper to predict the required forces for successful state transitions. Based on the models, we develop design guidelines for the gripper so that it can be used for different flying robots with different weights. Experiments are conducted to validate the models. Attaching the gripper onto a quadcopter, we demonstrated aerial perching onto rods and aerial grasping rod-like objects. Because the MIP gripper is lightweight (can reach a mass ratio of 0.75% between the gripper and the grasped object for static grasping), we expect it would be well suited for aerial perching or grasping due to the limited payload capability for flying robots.
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- Award ID(s):
- 1815476
- NSF-PAR ID:
- 10338705
- Date Published:
- Journal Name:
- IEEE/ASME Transactions on Mechatronics
- ISSN:
- 1083-4435
- Page Range / eLocation ID:
- 1 to 11
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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This work proposes a novel generative design tool for passive grippers---robot end effectors that have no additional actuation and instead leverage the existing degrees of freedom in a robotic arm to perform grasping tasks. Passive grippers are used because they offer interesting trade-offs between cost and capabilities. However, existing designs are limited in the types of shapes that can be grasped. This work proposes to use rapid-manufacturing and design optimization to expand the space of shapes that can be passively grasped. Our novel generative design algorithm takes in an object and its positioning with respect to a robotic arm and generates a 3D printable passive gripper that can stably pick the object up. To achieve this, we address the key challenge of jointly optimizing the shape and the insert trajectory to ensure a passively stable grasp. We evaluate our method on a testing suite of 22 objects (23 experiments), all of which were evaluated with physical experiments to bridge the virtual-to-real gap. Code and data are at https://homes.cs.washington.edu/~milink/passive-gripper/
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1109/TMECH.2022.3175649
