Robots have been a valuable tool for providing a remote presence in areas that are either inaccessible or too dangerous for humans. Having a robot with a high degree of adaptability becomes crucial during such events. The adaptability that comes from high mobility and high durability greatly increases the potential uses of a robot in these situations, and therefore greatly increases its usefulness to humans. DROP is a lightweight robot that addresses these challenges with the capability to survive large impacts, carry a usable payload, and traverse a variety of surfaces, including climbing vertical surfaces like wood, stone, and concrete. The platform is crash-proof, allowing it to be deployed in ways including being dropped from an unmanned aerial vehicle or thrown from a large MSL-class (Mars Science Laboratory) rover.
The goal of the DROP project is to create a robot that is lightweight, durable, and capable of climbing a variety of vertical surfaces. The robot is also designed to transition easily from horizontal to vertical travel, and vice versa, as well as having the ability to scamper over very rough or rocky approaches. Shape Deposition Manufacturing (a specialized multi-material fabrication process) and rapid prototyping (3D printing) were used to create a new climbing mechanism and simple body design to meet these specifications.
The climbing mechanism uses microspine hooks for climbing. These hooks are arranged in a completely new manner on DROP that will allow climbing without complex mechanics or controls. This same mechanism has the additional benefit of increasing the maximum ground speed.
The body of DROP merges elements necessary for vertical climbing with a design that is compliant and impactresistant. The main sections of the body are radially symmetric and allow impact forces to be absorbed similarly, regardless of the orientation during impact. The body features multi-material construction for the purpose of being both lightweight and durable. The use of impact-dampening materials, such as polymers in the Shore 20A-60A hardness range, serves to reduce the impact forces on the controls, the parts most susceptible to impact failure. The body design is similar to the “two-wheeled-plus-tail.”
DROP achieves its mobility through the use of wheel-like microspine sprockets. Microspines provide a low-mass, zero-power solution to climbing. For these reasons, microspines are desirable for use in smaller robots. Creating a circular array of these microspines, each with an independent flexible suspension, allows continuous engagement with the climbing surface using a straightforward, rotary motion. The suspension feature enables each microspine hook to engage the surface independently of other hooks, increasing the chances of multiple engagements. The flexibility of the suspension then allows the microspine hook to remain engaged as the sprocket rotates through a greater range of motion than would otherwise be possible.
The body is constructed from a highelongation, polyamide-based material and features a two-wheeled design with a tail for stability. The body can be produced quickly and cheaply via selective laser sintering (SLS) from materials that feature high impact resistance. The body is divided into two main components: a central section that houses the motors, and a tail section that contains the batteries, RF receiver, and microprocessor unit. The center and tail sections are connected by alternating sections of SLS material and a polymer of Shore-60A hardness. These alternating sections of hard and soft allow the tail to bend and twist relative to the central section. This flexible connection not only allows the two sections to absorb impacts independently, but also serves to absorb impacts through its capacity to deform.
Two motors allow the robot to turn in confined spaces and climb with a usable payload. A microcontroller makes it possible to accurately manipulate the rotation of the microspine sprockets. Doing so enables DROP to use one motor control algorithm for ground travel at high speed and another for more controlled, secure climbing.
This work was done by Aaron Parness and Clifford F. McKenzie of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management NPO-48314
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
E-mail:
This Brief includes a Technical Support Package (TSP).
DROP: Durable Reconnaissance and Observation Platform
(reference NPO-48314) is currently available for download from the TSP library.
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Overview
The document discusses the Durable Reconnaissance and Observation Platform (DROP), a robotic system developed to enhance remote presence in environments that are inaccessible or hazardous for humans. The project, associated with the California Institute of Technology and NASA, aims to address the limitations of existing climbing robots, particularly their durability and ability to transition between different terrains.
DROP is equipped with a 7.4V, 180mAh LiPo battery, providing approximately 20 minutes of operational life. The robot has demonstrated impressive capabilities, including the ability to transition from horizontal to vertical surfaces with high success and repeatability, achieving a ground speed of 45 cm/s—50% above its initial goal of 30 cm/s. It can also climb steep surfaces, reaching speeds of 25 cm/s on 85° inclines. However, the design currently limits transitions from vertical to horizontal surfaces due to the mass and stiffness of the tail, which creates a large moment that hinders this movement.
The document highlights the durability of DROP, noting that it can survive falls from heights of 3 meters onto concrete, although it failed to survive a 4-meter fall due to material choices and design flaws in the end cap connecting the sprocket array to the drive axle. This aspect underscores the challenges faced in balancing robustness and weight in climbing robots.
Existing platforms like SpinyBot, RiSE, and WaalBot are mentioned as having mobility in vertical environments but lacking the durability required for significant falls. The document emphasizes the need for improved durability in climbing robots, which can be achieved through various methods, such as increasing shock absorption or reducing weight.
Overall, the DROP project represents a significant advancement in robotic technology, aiming to create a versatile and durable platform capable of navigating complex terrains. The research findings and technological developments outlined in the document are intended to inform future innovations in robotics, particularly for applications in unpredictable environments. The document serves as a technical support package, providing insights into the design, testing, and potential applications of the DROP system.
