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Paper Digest: A Robot Is Built Using Cockroach Biomimicry

Photo credit: Erik Karits via Unsplash.

Cockroaches are not the most popular organism out there, but a close-up look at their hardware will cause one to appreciate their design more. In 2009, engineer Stuart Burgess and his co-authors did just that. They published a paper titled, “Design and Testing of a Highly Mobile Insect-Inspired Autonomous Robot in a Beach Environment.” Writing in the International Journal of Design & Nature and Ecodynamics, the researchers detailed their design of a cockroach-inspired robot that can traverse a beach environment. This publication shows how complex designs in nature can help inspire and improve human technology through the field of biomimetics. Technology aside, biomimetics as a discipline has a positive impact upon biology as it brings a deeper understanding of what it would take to design the cockroach. 

A Remarkable Gait

Cockroaches are incredibly agile and run with a tripod gait until they encounter an obstacle. Then they use an adjusted gait to climb large obstacles — say, your discarded coffee cup. The paper includes a description of how roaches turn and it connects biological behavior to concepts of mechanical motion.

The cockroach turns by generating asymmetrical motor activity in legs on either side of its body as they extend during stance.

In addition to the mechanisms for generating forward and rotational movement, the front legs of the cockroach can swing up over its head, and it is able to use its middle legs to pitch its body upwards. This enables a cockroach to climb obstacles higher than its head. Cockroaches have flexion joints within the body to bend the front half down to avoid getting stuck on an object (high centering). Burgess and his coauthors recognized that this unwanted guest has a wealth of design information to share about how to navigate different surfaces and climb over obstacles. Accordingly, the team studied the cockroach and sought to mimic its tripod gait, gait modulation, and flexion joints to design a robot to navigate a beach.

Navigating beach terrain poses many unique challenges. For example, the robot must be able to handle soft sand, go over objects, and deal with hard-packed sand. To construct a robot to meet these requirements includes, but is not limited to, a specific design of the robot’s structure, cable steering, foot design, component layout, enclosure, heat dissipation, weight distribution, gait control mechanism, communication, control, performance simulation, and the electronic hardware and controller design — all subheadings within the paper’s section on the prototype beach robot.

An Amphibious, Surf-Zone Robot

Using knowledge gleaned from building the prototype robot, the team then designed an amphibious, surf-zone robot that can move on the sea floor as well as the beach. To add this new capability of being amphibious required several specializations in the areas of mechanical design, component layout, sealed body, and body joint.

To illustrate how understanding these design processes can enhance our appreciation of biological design and the obstacles inherent in system design, let’s examine the component layout design process in detail.

During the component layout, many requirements were considered before a plan for organizing the components was put into place. For example, the overall size of the robot compared to the size of the components needing to be housed within the structure (sensors and related electronics) was considered. Then the positioning of the components relative to their position of action in the system was considered. To do this type of analysis requires understanding the system and its goals, and it requires knowing how to optimally arrange components. Here, for example, is a snippet of text where they justify a design decision:

The front body segment will leave as much room as possible for sensors and related electronics. It will only contain the drive motor, steering servos, and a speed controller. [Emphasis added.]

They then describe a design decision that resulted from switching from the prototype robot to the amphibious robot:

In previous Whegs™ robots, the compliant mechanisms were contained inside the frame. However, there is no need to waterproof these mechanisms, so they have been moved outside the sealed frame to save space. All drive chains run along the sides to prevent dividing up the usable space.

They then go on to describe additional design decisions regarding component layout that will enable the robot to operate optimally in the amphibious environment.

The front and rear bulkheads of the robot will be rounded to give good hydrodynamic characteristics and to allow it to push up and over irregularly shaped obstacles. Windows can be easily added to the bulkhead to allow video cameras to be stored inside the front body segment.

Appreciating the Lowly Cockroach

If the design of such an amphibious robot necessitates this component layout design process, then shouldn’t the design of the imitated system necessitate a similarly intelligent, mind-based process for component layout? The lowly cockroach that inspired this robot should also have needed a determination of where components should be placed. The more complex design of the cockroach is also seen in that it is self-assembling through a developmental process, adding further complexity to component placement.

The success they had in mimicking the cockroach is evident in this summary of what the team was able to accomplish:

Our Beach Whegs™ robot is designed with active and passive mechanisms for maximum mobility and terrain adaptability. The robot is propelled by a single motor to move in a cockroach-like tripod gait normally, but passively adapts its gait for mobility on different terrains. Through extensive field testing, we have isolated, tested, and integrated a range of subsystem designs to create a robot suited for autonomous operation. These innovations have resulted in a robust robot well suited to autonomous operation in the beach and other sandy/rocky environments.

Impressively, the researchers were able to use biological inspiration to develop an amphibious robot for operation in a surf-zone environment. This reminds us how intricate designs in nature can be used to develop human technology. As a further lesson, biomimetics as a discipline leads to a better understanding of what it takes to create a cockroach — I mean, a real one. Although the paper does not investigate questions about origins, the understanding of what it takes to build complex systems sheds light on the causal hurdles that would be necessary for evolutionary processes to overcome.