Whegs™ I
The robot pictured above is Whegs™ I. It is 20 inches long, and utilizes three-spoke wheel-legs and one drive motor. It can climb obstacles of heights up to 1.5x the wheel-leg radius, and the robot can move up to a speed of 3 body lengths/second (5.5km/hr).

While walking on flat ground, three of the wheel-legs are 60 degrees out of phase with the other three wheel-legs, which allows the robot to use an alternating tripod gait (Part 1 in the figure below). This gait requires that the two front wheel-legs be out of phase with each other. In the illustration below, one front wheel-leg is dark grey, while the other front wheel-leg is light grey.

When an obstacle is encountered (Part 2 in the figure below), passive mechanical compliance allows the front legs to come back into phase with each other, so that they can both be used to pull the robot up and over the obstacle.


After the robot has pulled itself over the obstacle (part 5), the front legs fall back into the previous pattern Since Whegs™ I has 6 wheel-legs, it will return to an alternating tripod gait (part 6).

Below are some movies Whegs™ I. Click on any of the thumbnails to view the movie.

These can be compared to this video of a cockroach climbing on top of an obstacle that was taken by the Ritzmann Lab:

Whegs™ II was an improvement over Whegs™ I in terms of durabily and capability. In addition to a more advanced wheg design, it had a body joint that allowed it to climb over taller obstacles. Below are some pictures of it.

Below are two Quicktime videos of Whegs™ II. Click on the thumbnails to view the movies (25MB, 22MB).

While Whegs™ II is an efficient, capable robot for handling uneven terrain it has been teleoperated until now; requiring a person to control speed, steering, and flexion of the body joint. With the addition of sensors, low-computational power microcontrollers, and basic insect-like behaviors Whegs™ II is able to autonomously navigate its environment.

After analyzing how a cockroach positions its antennae when deciding to climb over or tunnel under a shelf-like obstacle, mechanical antennae were designed and fitted to Whegs™ II. The mechanical antennae swept up and down, each at a different rate, as the robot moved through its environment. When a shelf was encountered, the position of the antennae of the obstacle helped Whegs™ II autonomously decide whether to climb or tunnel. Like the cockroach, when both mechanical antennae touched the bottom of the shelf, the robot tunneled. And when both touched the top of the shelf, a climbing behavior was initiated. When one antenna touched the top while the other touched the bottom, Whegs™ II tunneled, just like the insect in a bright environment.

Two Quicktime videos of Whegs™ II climbing and tunneling with a shelf-like obstacle (20MB, 19MB).

Since the mechanical antennae had limited use in environments without shelf-like obstacles a new sensor and behavior system was developed. This system used ultrasonic range finding sensors to detect obstacles. It used a single emitter and a pair of splayed receivers to detect obstacles left, right, and in front of Whegs™ II.

When teleoperated, the sensor pod and obstacle avoidance behavior would sense potential collisions and adjust the operator's command to avoid trouble. With a different behavior, Whegs™ II was able to specifically locate the position of obstacles by using interaural time differences (ITD) in a similar manner as owls and people. This behavior measured the time it took for an ultrasonic echo to reach the left and right receivers and used triangulation to pinpoint the obstacle's position. The position of the obstacle from the current heading (left or right of centerline) determined steering and the distance from the front of the robot determined speed. All of the obstacle position sensing, speed, and steering was autonomously generated by Whegs™ II without any operator intervention.



Below are several Quicktime videos of Whegs™ II with the Ultrasonic Sensor Pod. Click on the thumbnails to view the movies.

(14MB, 16MB, 8MB)

(156MB, 53MB, 66MB, 72MB)

Autonomous Whegs™ II publications:

Lewinger, W.A., C.M. Harley, R.E. Ritzmann, M.S. Branicky, and R.D. Quinn. (2005) "Insect-like Antennal Sensing for Climbing and Tunneling Behavior in a Biologically-inspired Mobile Robot," IEEE International Conference on Robotics and Automation (ICRA'05) Proceedings, Barcelona, Spain, April 18-22, 2005.

Lewinger, W.A., C.M. Harley, R.E. Ritzmann, M.S. Branicky, and R.D. Quinn. "Insect-like Antennal Sensing for Climbing and Tunneling Behavior in a Biologically-inspired Mobile Robot," IEEE International Conference on Robotics and Automation (ICRA'05) Video Proceedings, Barcelona, Spain, April 18-22, 2005. (Won Best Video Award)

Lewinger, W.A., M.S. Watson, and R.D. Quinn. (2006) "Obstacle Avoidance Behavior for a Biologically-Inspired Mobile Robot Using Binaural Ultrasonic Sensors," Proceeding of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'06), Beijing, China, October 9-13, 2006.

Lewinger, W.A., M.S. Watson, and R.D. Quinn. (2006) "Obstacle Avoidance Behavior for a Biologically-Inspired Mobile Robot Using Binaural Ultrasonic Sensors," Video Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS'06), Beijing, China, October 9-13, 2006.