RHex is an all-terrain walking robot that could one day climb over rubble in a rescue mission or cross the desert with environmental sensors strapped to its back. Pronounced “Rex,” like the over-excited puppy it resembles when it is bounding over the ground, RHex is short for “robot hexapod,” a name that stems from its six springy legs.

Legs have an advantage over wheels when it comes to rough terrain, but the articulated legs often found on walking robots require complex, specialized instructions for each moving part. To get the most mobility out of RHex’s simple, one-jointed legs, Penn researchers are essentially teaching the robot Parkour. Taking inspiration from human free-runners, the team is showing the robot how to manipulate its body in creative ways to get around all sorts of obstacles.

The RHex platform was first developed through a multi-university collaboration more than a decade ago. Graduate student Aaron Johnson and professor Daniel Koditschek, both of the Department of Electrical and Systems Engineering in the School of Engineering and Applied Science, are working on a version of RHex known as XRL, or X-RHex Lite. This lighter and more agile version of the robot, developed in Koditschek’s Kod*Lab, a division of Engineering’s General Robotics, Automation, Sensing and Perception (GRASP) Lab, is ideal for testing new ways for it to run, jump, and climb.

By activating its legs in different sequences, XRL can execute double jumps, flips, and, through a combination of moves, even pull-ups. For the tallest obstacles, the robot can launch itself vertically, hook its front legs on the edge of the object it’s trying to surmount, then drag its body up and over. The researchers fully demonstrated this particular maneuver under more controlled conditions in the lab.

The paper where Johnson and Koditschek outlined these capabilities—”Toward a Vocabulary of Legged Leaping“—was selected as a finalist for best student paper at the IEEE International Conference on Robotics and Automation in May.

“What we want is a robot that can go anywhere, even over terrain that might be broken and uneven,” Johnson says. “These latest jumps greatly expand the range of what this machine is capable of, as it can now jump onto or across obstacles that are bigger than it is.”

ARTICLE By Evan Ackerman

RHex has been practicing its jumping skills, and UPenn has a tremendous new video of the robot doing Parkour across campus rooftops.

Was one of these moves particularly difficult to pull off? If so, why, and how’d you solve it?

The double jump across a gap is probably the hardest, in addition to being one of the more dangerous. There are some interesting trade-offs when it comes to gap jumping: do you want to start closer to the gap so you don’t have to jump as far, or do you want to start farther back so you can get full traction with all of your legs? In the end, it helps to sneak up as close as you can to the edge while still getting some amount of torque out of the middle legs on that second bounce. Backing up farther to let the front legs help ended up being a little worse.

One move that didn’t make it is the pull-up onto the table’s edge. That move is still much too hard to do outdoors, and relies on very subtle leg stretching and ground interactions that we are in the process of modeling more carefully.

What are some ways that you might be able to make RHex faster than a speeding bullet and able to leap tall buildings in a single bound?

Well, we can already leap onto ledges in a single bound that are tall compared to the robot, but in order to really push the performance of a robot such as RHex it helps to have a very good actuator model. The motors in this robot are rated to about 2-3A continuous current, but to get these moves I’ve set the current limit at 20A. This means that they heat up quite quickly, but with a good thermal model we can monitor the motor core temperature and ensure that for these quick leaps they stay within the thermal limits. For the worst of these jumps, we know that the motor core heats up by 50C in less than half a second. Knowing how far you can push your robot is key to getting these kinds of peak performance behaviors.

Will this project be extended? If so, what are you working on next, and what are your long-term hopes/dreams/fantasies for RHex?
Yes, this project is ongoing, and one of the challenges that I’m excited to try and tackle is running transitions. Most of these dynamic transitions start from rest, but we have some early results with running flips that look promising. We are also eager to take these behaviors out to the desert where we’ve done some testing with RHex in the past. These behaviors should enable RHex to access even more of the terrain out there.

Any chance of seeing some outtakes? I bet there are some good ones!
The outtakes are pretty painful, if you have any empathy for the robot. In truth RHex can take quite a beating and still run most of the time, but it is hard to watch. We may post some outtakes in the future, for now though we will be posting a longer version of this video with extended clips and some additional angles that didn’t make it into the final cut.

Links:

http://spectrum.ieee.org/automaton/robotics/aerial-robots/rhex-does-parkour-all-over-upenn

http://kodlab.seas.upenn.edu/Aaron/ICRA2013

The post Rhex Project Update 2013 August 11116 appeared first on Robotpark ACADEMY.

RHex has a sealed body, making it fully operational in wet weather, muddy and swampy conditions. RHex’s remarkable terrain capabilities have been validated in government-run independent testing. RHex is controlled remotely from an operator control unit at distances up to 700 meters. Visible/IR cameras and illuminators provide front and rear views from the robot.

Terrain Specifications

Traverses rock fields, mud, sand, snow, gravel, 60% inclines and other rough terrain
• Crosses railroad tracks, curbs, logs and pipes
• Culvert inspection
• Climbs stairs
• Rugged modular design for maximum reliability in harsh conditions
• Operator control unit (OCU) with live video feed for remote operation
• IP Radio with 400-700m range
• Modular payload bay for mission specific packages

Specifications

RHex is a power – and computation – autonomous hexapod robot with compliant legs and only one actuator per leg. It is the first documented autonomous legged machine to have exhibited general mobility (speeds at bodylengths per second) over general terrain (variations in level at bodyheight scale). RHex is presently capable of speeds exceeding five body lengths per second (2.7 m/s), negotiates a wide variety of rugged terrains over thousands of bodylengths (3700 m distance on one set of batteries), manages slopes exceeding 45 degrees, swims, and climbs stairs.

Size:
Weight: 27.5lbs without batteries
Dimensions: 22”L x 16”W x 5.2”H (legs not extended)
Power:
Battery: Two BB2590 Batteries
Endurance: 6 hours
Mobility:
Entrapment Risk: Extremely low
Speed: over 2mph on natural terrain
Slopes: Up to 60% slope walk, up to 84% climb mode
Vertical Step: 8.5”
Water Ford Depth: 6”+
Environmental:
Temperature: -15C to 45C ambient continuous operation
Water: IP67 sealed, water submersible
Exposure: Tolerant of humidity, salt, oil, sand extremes
Cameras:
Fore and aft cameras and illuminators
Driving Resolution: 320×240 pixels
Still Image Resolution: 1280×960 pixels
Illuminators: Adjustable 6W Visible, 6W Infrared

11019-RHex-BostonDynamics2

Capabilities of RHex

Throughout its development, RHex acquired a large number of capabilities in its behavioral repertoire. In fact, it is the only robot that is capable of performing such a wide variety of behaviors as a single, autonomous robot. This performance is due to the significant amount of inspiration from the study of biological systems, leading to a number of principles underlying RHex’s design.

• The use of legs instead of wheels or tracks opens the way for a large number of behaviors
• Passive compliance in the legs overcomes limitations of underactuation and helps simplify mechanical design, yielding robustness
• Sprawled posture, inspired from insects, results in passive stabilization of lateral motion
• Control is open-loop at the gait level, but closed loop at the task level. Stability comes as a result of passive mechanics, not high-bandwidth active control

At the end of the project’s five years, RHex was capable of performing the following, mostly open-loop behaviors
–Running on reasonably flat, natural terrain at speeds up to 6 body lengths per second (just over 2.7 m/s)
–Climbing a wide range of stairs
–Climbing slopes up to 45 degrees
–Traverse obstacles as high as 20 cm (about twice RHex’s leg clearance)
–Continuously run for 45 minutes, covering up to 3 miles with an efficient gait
–Successfully traverse badly broken terrain with large rocks and obstacles
–Walk and run upside down
–Flip itself over to recover nominal body orientation
–Leaping across ditches up to 30 cm wide
–Support remote control from up to 150m distance

in addition to a number of behaviors that increasingly relied on feedback from sensors such as the onboard gyro, camera and strain gauges on the legs.

–Perform autonomous stabilization of yaw heading while running using feedback from the gyro
–Autonomously follow a line on the ground without any operator control
–Perform simultaneous localization and mapping by using artificial landmarks scattered over natural terrain
–Locomote on only two legs using active pendulum stabilization
–Autonomously change the rest lengths of its leg springs
–Autonomously run systematic experiments to tune its running gaits
–Use inertial sensors in combination with leg strain gauges to accurately estimate its body pose

JUMPING RHEX Light Robot

Move aside, Sand Flea, you’re not the only jumping robot in town. The researchers over at the University of Pennsylvania have taught their little six-legged X-RHex Light to make leaps and bounds as well, making it one of a few bots to both run and jump effectively.

While it can’t spring as high as the Boston Dynamics critter, the X-RHex can cross gaps with not just a bound but a running gait, given enough room. It can also flip itself over, climb onto a ledge with a double hop and perform a leaping grab to something as high as 73 centimeters (28.74 inches).

The X-RHex itself isn’t new; the curved-legged contraption has been around for at least a couple years, and even sported a cat-like tail for balance at one point. Still, the fact that the hefty 6.7 kilogram (14.8 pound) machine can now somersault through the air is a quite a victory, and one that reminds us of the impending robocalypse.

Video Links
Youtube- http://youtu.be/ISznqY3kESI
Youtube- http://youtu.be/kV9J-oayCBU

Resource Links

http://www.bostondynamics.com

http://www.engadget.com/2013/05/10/x-rhex-light-jumping-robot/

The post RHex Rough-Terrain Robot (Boston Dynamics) – 11019 appeared first on Robotpark ACADEMY.