Richard J. Bachmann

Abstracted biological principles applied with reduced actuation improve mobility of legged vehicles

Applying abstracted biological locomotion principles with reduced actuation can result in an energetic vehicle with greater mobility because a vehicle with the fewest number of motors can have the highest power to mass ratio. One such hexapod is Whegs II, which benefits from abstracted cockroach locomotion principles and has just one motor for propulsion. Similar to Whegs I, it nominally runs in a tripod gait and passive mechanisms enable it to adapt its gait to the terrain. One of the drawbacks of Whegs I is that it cannot change its body posture. Cockroaches pitch their bodies up in anticipation of climbing a step to enable their front legs to reach higher. They also flex their bodies down while climbing to permit their front legs to maintain contact with the substrate. A bidirectional servo-driven body flexion joint has been implemented in Whegs II to accomplish both of these behaviors. It is shown to be highly mobile and energetic.

Parallel Complementary Strategies for Implementing Biological Principles into Mobile Robots

Our goal is to use intelligent biological inspiration to develop robots that capture the capacity of animals to traverse complex terrain. We follow two distinct but complementary strategies to meet this goal. In one, we have produced a series of robots that have mechanical and control designs increasingly more similar to those of a cockroach. The leg designs of these robots ensure that they can generate movements used by the cockroach to walk and climb over a range of objects. However, in order to take advantage of these complex designs, we must first solve difficult problems in actuation, proprioception and control. The second parallel strategy seeks to capture the principles of biological movement, but in an abstract form that does not require complex platforms. Following the second strategy, we designed and built two new robots that each use only one propulsion motor to generate a nominal tripod gait. Gait changes similar to those used by the animal are accomplished through passive mechanisms. Rearing movements in anticipation of climbing are accomplished by way of a body flexion joint, which also allows the robot to avoid high-centering. The parallel development of these robotic lines provides the best of both worlds. The multi-segmented leg designs will ultimately be more versatile and agile than the abstracted line, but will take more effort to perfect. The simplified line provides short-term solutions that can be deployed immediately and confirm, in principle, the value of biological properties for complex locomotion.

Design and simulation of a cockroach-like hexapod robot

This paper describes the design and simulation of a cockroach-like hexapod robot which is under construction for the purpose of testing control principles which are being extracted from the cockroach. The cockroach was chosen because of its remarkable running and climbing capabilities and because much is known about its biomechanics and control. The robot is designed with five, four, and three degrees of freedom in the front, middle and rear legs, respectively, to permit it to mimic the different functions of cockroach legs. Pneumatic cylinders actuate each joint and provide opposing muscle-like forces to actuate the joints. Pulse-width modulation controls the actuators with the necessary smoothness and precision. A dynamic simulation has been developed to predict loads on the structure and the required joint torques.

Comparing cockroach and Whegs robot body motions

Abstracting cockroach locomotion principles with reduced actuation can lead to a simple yet effective cockroach-like vehicle able to traverse irregular terrain. One such hexapod robot is Whegs VP, which achieves a cockroach-like nominal tripod gait using only a single DC motor. Whegs VP uses compliant mechanisms in its axles to passively adapt its gait to the terrain such that it can climb obstacles 175% of its leg height. High speed video analysis of walking cockroaches and Whegs VP illustrates that Whegs VP walks with cockroach-like body motions. The experiments indicate that stepping patterns play a major role in an animals or robots overall body motions.

A sensor platform capable of aerial and terrestrial locomotion

A sensor platform has been developed that is capable of both aerial and terrestrial locomotion, as well as transitioning between the two. The morphing micro air-land vehicle (MMALV) implements biological inspiration in both flying and walking. MMALV integrates the University of Floridas micro air vehicle (MAV) technology with the terrain mobility of Mini-Whegs/spl trade/. Fabricated of lightweight carbon fiber, the UF-MAV employs a flexible wing design to achieve improved stability over other MAVs of similar size. Mini-Whegs/spl trade/ employs the patented (pending) wheel leg running gear that makes the Whegs/spl trade/ and Mini-Whegs/spl trade/ line of robots fast, agile, and efficient. MMALV has a 30.5cm wingspan, and is 25.4cm long. Terrestrial locomotion is achieved using two independently controlled wheel legs, which are differentially actuated to perform turning. The vehicle successfully performs the transition from flight to walking. Furthermore, MMALV is capable of transitioning from terrestrial to aerial locomotion by walking off a structure of only 20 feet. A wing retraction mechanism improves the portability of the vehicle, as well as its terrestrial stealth and ability to enter small openings.

Design of a Quadruped Robot Driven by Air Muscles

This paper describes the development of Puppy, a canine-inspired quadruped robot driven by Festo air muscles. Puppy was designed to be a test bed for implementation and control of pneumatic muscles in legged locomotion. A two-dimensional kinematic model was developed using joint range of motion data and skeletal dimensions from large-breed canines, specifically the adult greyhound. This model was used to predict structural loads, required joint torques, muscle origin and insertion locations, and actuator lengths. Based on this study, the quadruped robot was designed with three degrees of freedom in each leg, all confined to motion in the vertical plane. Festo air muscles were mounted in antagonistic pairs and have been controlled using pulse-width modulation with closed-loop position feedback. Currently, the front legs and spine have been assembled and have successfully tracked position angles during air walking. The two legs can lift a 13.5 kg payload, nearly twice the predicted weight of the entire robot

Design of a semi-autonomous hybrid mobility surf-zone robot

Surf-zone environments pose extreme challenges to robot operation. A robot that could autonomously navigate through the rocky terrain, constantly changing underwater currents, hard-packed moist sand, and loose dry sand characterizing this environment, would have very significant utility for a range of defence and civilian missions. The study of animal locomotion mechanisms can elucidate specific movement principles that can be applied to address these demands. In this work, we report on the design and optimization of a biologically inspired autonomous robot for deployment and operation in an ocean beach environment. Based on recent success with beach environment autonomy and a new rugged waterproof robotic platform, we propose a new design that will fuse a range of insect-inspired passive mechanisms with active autonomous control architectures to seamlessly adapt to and traverse through a range of challenging substrates both in and out of the water.

Toward Mission Capable Legged Robots through Biological Inspiration

Insects provide good models for the design and control of mission capable legged robots. We are using intelligent biological inspiration to extract the features important for locomotion from insect neuromechanical designs and implement them into legged robots. Each new model in our series of robots represents an advance in agility, strength, or energy efficiency, which are all important for performing missions. Robot IV is being constructed with a cockroach mechanical design. It features a lightweight exoskeleton structure and McKibben artificial muscles for passive joint stiffness. Our self-contained microrobot has rear legs that are inspired by cricket. Its diminutive size required us to custom fabricate almost all of its parts, including its McKibben actuators.

Worm-Like Robotic Locomotion with a Compliant Modular Mesh

In order to mimic and better understand the way an earthworm uses its many segments to navigate diverse terrain, this paper describes the design, performance, and sensing capabilities of a new modular soft robotic worm. The robot, Compliant Modular Mesh Worm CMMWorm, utilizes a compliant mesh actuated at modular segments to create waveforms along its body. These waveforms can generate peristaltic motion of the body similar to that of an earthworm. The modular mesh is constructed from 3-D printed and commercially available parts allowing for the testing of a variety of components that can be easily interchanged. In addition to having independently controlled segments and interchangeable mesh properties, CMMWorm also has greater range of contraction 52% of maximum diameter than our previous robot Softworm 73% of maximum diameter. The six-segment robot can traverse flat ground and pipes. We show that a segment is able to detect the wall of a pipe and return to its initial position using actuator-based load-sensing. A simple kinematic model predicts the outer diameter of the worm robots mesh as a function of encoder position.

A rapidly reconfigurable robot for assistance in urban search and rescue

A robot is being developed for urban search and rescue missions. USAR Whegs™ implements several new features into Whegs™ robot design. It is the first quadruped Whegs™ robot of this scale. It uses differential steering and the user can rapidly change its running gear to and from tracks and wheel-legs. This is also the first implementation of carbon fiber wheel-legs on a Whegs™ vehicle. The carbon-fiber reduces the mass moment of inertia eight times compared to previous aluminum designs. The running gear can be changed in 30 seconds and the resulting connections are secure. GeoSystems Zippermast allows a camera to be deployed as high as eight feet above the robot. The robot is 47.6 cm long, can travel 1.9 meters per second on its tracks, and can climb 15 cm obstacles using its wheel-legs. A two-speed transmission is being developed to permit it to run more slowly on wheel-legs for better control on irregular terrain.