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Spherical Induction Motor Eliminates Robot’s Mechanical Drive System
PITTSBURGH— More than a decade ago, Ralph Hollis invented the ballbot, an elegantly simple robot whose tall, thin body glides atop a sphere slightly smaller than a bowling ball. The latest version, called SIMbot, has an equally elegant motor with just one moving part: the ball.
The only other active moving part of the robot is the body itself.
The spherical induction motor (SIM) invented by Hollis, a research professor in Carnegie Mellon University’s Robotics Institute, and Masaaki Kumagai, a professor of engineering at Tohoku Gakuin University in Tagajo, Japan, eliminates the mechanical drive systems that each used on previous ballbots. Because of this extreme mechanical simplicity, SIMbot requires less routine maintenance and is less likely to suffer mechanical failures.
The new motor can move the ball in any direction using only electronic controls. These movements keep SIMbot’s body balanced atop the ball.
Early comparisons between SIMbot and a mechanically driven ballbot suggest the new robot is capable of similar speed — about 1.9 meters per second, or the equivalent of a very fast walk — but is not yet as efficient, said Greg Seyfarth, a former member of Hollis’ lab who recently completed his master’s degree in robotics.
Induction motors are nothing new; they use magnetic fields to induce electric current in the motor’s rotor, rather than through an electrical connection. What is new here is that the rotor is spherical and, thanks to some fancy math and advanced software, can move in any combination of three axes, giving it omnidirectional capability. In contrast to other attempts to build a SIM, the design by Hollis and Kumagai enables the ball to turn all the way around, not just move back and forth a few degrees.
Though Hollis said it is too soon to compare the cost of the experimental motor with conventional motors, he said long-range trends favor the technologies at its heart.
“This motor relies on a lot of electronics and software,” he explained. “Electronics and software are getting cheaper. Mechanical systems are not getting cheaper, or at least not as fast as electronics and software are.”
SIMbot’s mechanical simplicity is a significant advance for ballbots, a type of robot that Hollis maintains is ideally suited for working with people in human environments. Because the robot’s body dynamically balances atop the motor’s ball, a ballbot can be as tall as a person, but remain thin enough to move through doorways and in between furniture. This type of robot is inherently compliant, so people can simply push it out of the way when necessary. Ballbots also can perform tasks such as helping a person out of a chair, helping to carry parcels and physically guiding a person.
Until now, moving the ball to maintain the robot’s balance has relied on mechanical means. Hollis’ ballbots, for instance, have used an “inverse mouse ball” method, in which four motors actuate rollers that press against the ball so that it can move in any direction across a floor, while a fifth motor controls the yaw motion of the robot itself.
“But the belts that drive the rollers wear out and need to be replaced,” said Michael Shomin, a Ph.D. student in robotics. “And when the belts are replaced, the system needs to be recalibrated.” He said the new motor’s solid-state system would eliminate that time-consuming process.
The rotor of the spherical induction motor is a precisely machined hollow iron ball with a copper shell. Current is induced in the ball with six laminated steel stators, each with three-phase wire windings. The stators are positioned just next to the ball and are oriented slightly off vertical.
The six stators generate travelling magnetic waves in the ball, causing the ball to move in the direction of the wave. The direction of the magnetic waves can be steered by altering the currents in the stators.
Hollis and Kumagai jointly designed the motor. Ankit Bhatia, a Ph.D. student in robotics, and Olaf Sassnick, a visiting scientist from Salzburg University of Applied Sciences, adapted it for use in ballbots.
Getting rid of the mechanical drive eliminates a lot of the friction of previous ballbot models, but virtually all friction could be eliminated by eventually installing an air bearing, Hollis said. The robot body would then be separated from the motor ball with a cushion of air, rather than passive rollers.
“Even without optimizing the motor’s performance, SIMbot has demonstrated impressive performance,” Hollis said. “We expect SIMbot technology will make ballbots more accessible and more practical for wide adoption.”
The National Science Foundation and, in Japan, Grants-in-Aid for Scientific Research (KAKENHI) supported this research. A report on the work was presented at the May IEEE International Conference on Robotics and Automation in Stockholm, Sweden.
Video by: Carnegie Mellon University
About Carnegie Mellon University: Carnegie Mellon (www.cmu.edu) is a private, internationally ranked research university with programs in areas ranging from science, technology and business, to public policy, the humanities and the arts. More than 13,000 students in the university’s seven schools and colleges benefit from a small student-to-faculty ratio and an education characterized by its focus on creating and implementing solutions for real problems, interdisciplinary collaboration and innovation.
Carnegie Mellon University
5000 Forbes Ave.
Pittsburgh, PA 15213
Contact: Byron Spice For immediate release:
412-268-9068 October 4, 2016
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Servosila, a robotics technology company, announced a launch of a new line of robotic arm manipulators specifically targeted at mobile robotics market.
“Servosila Robotic Arms are the first manipulators specifically designed for mobile robots,” – said the company’s spokesperson, – “it is very easy to retrofit any existing robotic chassis or a torso with a Servosila Robotic Arm”.
Servosila Robotic Arms are attachable payload modules for mobile service robots or other robotic platforms. Servosila Robotic Arms shall typically be mounted on a chassis or a torso of a mobile robot and be powered by an on-board power supply system of the host robotic platform.
The robotic arms can be used both outdoors and indoors. The arms are water-tight, dust-proof and function properly in the rain and in the snow. The arms are designed to withstand impacts, collisions with obstacles and, in general, the harsh treatment so common to mobile robotics applications.
The servo drives and external electrical connectors of the robotic arms are water-tight and dust-proof (IP68 rating). The entire arm can be occasionally submersed in water without any adverse effects on its performance. The robotic arms may be operated in cold or hot weather.
Mobile robots tend to bump into things and hit obstacles while on the move. The harsh nature of outdoor mobile robotics applications caused a profound effect on the design of Servosila Robotic Arms, especially on the internal structure of servo drives and their harmonic reduction gears.
There are no exposed cables on the outside of the robotic arms that could be torn off when a mobile robot moves through bushes or forests.
Numerous protection measures built into electronic servo controllers and mechanical parts of Servosila Robotic Arms ensure reliable operation on-board of outdoor mobile service robots.
Servosila Robotic Arms are lightweight by design. For a given lifting capability, Servosila Robotic Arms have a significantly lower weight than their industrial counterparts. The lower weight of a Servosila Robotic Arm enables a mobile robot equipped with the arm to operate longer on a single battery charge, keep its center of gravity lower for better balance, climb stairs easier or have a superior mobility.
When not in an active use, Servosila Robotic Arms can folded into a very compact form that doesn’t occupy much space on the top of a robotic chassis or on the side of a torso. This feature protects the robotic arm of a mobile robot in case of an unexpected collision with an obstacle or whenever a rough terrain is encountered by the mobile robotic platform. The compact folded form also comes handy during transportation.
By folding its robotic arm into the compact form, the robot frees up its working area for other payloads to operate in. This is useful in case the robot is equipped with additional payloads other than the robotic arm.
Photo Credits: Servosila Limited (Hong Kong)
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We have made updates to our robotics events calendar at Robotic Magazine. See the calendar at our home and events pages. We update our calendar time to time, so do not forget to check back with us later…
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When researchers recently unveiled the first pop song composed by an artificial intelligence (AI) system, some creative types may have been nervous about the idea of robots taking over their jobs. But how exactly was AI used to write a song? Continue reading
Today by far the most commonly used robotics software is ROS, which stands for Robot Operating System. This is an open source software, and the most number of developers and robotics users are involved with this program with an ever increasing rate. It contains set of libraries, algorithms, developer tools and drivers for developing robotics projects. The first release of ROS was in 2010, and as of end of 2016, ROS has reached its 10th official release, which is called “ROS Kinetic Kame”. There are translations to 11 languages other than English, which are: German, Spanish, French, Italian, Japanese, Turkish, Korean, Portuguese, Russian, Thai and Chinese. It currently has 2000+ software libraries, which keeps increasing every year.
Many robots use ROS now, including but not limited to hobby robots, drones, educational or advanced humanoid robots, domestic robots including cleaning robot vacuums, cooking robots or telepresence robots and more, robot arms, farming robots, industrial robots, even Robonaut of NASA in space or the four legged military robots in development. A list of robots which use ROS can be found here: http://wiki.ros.org/Robots.
We were checking the Alexa.Com ranking of ROS since few years, in order to track the increase in usage, and we believe it is time to share it now, as we have enough data. The numbers on the left are dates we looked and the numbers on the right indicate the ranking of Ros.Org website from top, among all websites in the world:
May 2011: 189,000 th in the world, from top, among all other websites
April 2012: 187,900 th
January 2014: 107,821
May 2014: 112,236
September 2014: 83,875 (7219 in Canada, the country where it is most accessed)
January 2015: 83,556 (4,258 in Canada)
February 2015 : 75,680 (33185 in USA)
April 2015: 59,200 (31,334 in USA)
August 2015: 65,754 (50,132 in USA)
September 2016: 30,201 (China 5073)
This chart shows the increasing rank of ros.org among other websites in the world, which is a good indicator of its growth. The numbers on the left represent the site’s ranking from the top, among all other sites in the world. Chart Copyright: Robokingdom LLC.
As can be seen here, in May 2011, when we first checked this ranking, ROS.org was at 189,000 th place in the world from the top among all other websites in terms of unique visitors that visit the site, and it almost continuously increased its ranking. As of September 2016, it is now the 30,201st most reached website in the world, with mostly being accessed in China (5073 from top in China). Let’s not forget that even if it’s position remained the same, let alone going up, it would still mean the traffic of the site was going up, as every year there are more websites in the world which means the same ranking means better place and more traffic. The ranking of 30,201 means ROS.org is a very high traffic website in the world right now, being accessed probably by at least hundreds of thousands of people every day, with no indication of slowing down its rise yet.
The most important result of all of this, is that the use of robots is increasing, both in terms of number and type (when you look at the type of robots that use ros, as it also increases in variety all the time).
From Alexa, we were also able to see, from publicly available information, that the percentage of reach among countries for ROS.org is as follows:
South Korea 3.5%
This also shows us that in China, a lot of things are going on for robotics development right now, as it gets most of its traffic from there with 47.5%. USA then follows with 11.5% and Japan is third with 8.7%.
With ROS, any type of sensors can be controlled, including 1d/2d range sensors, 3d range finders and cameras, audio/speech recognition sensors, cameras, environmental sensors, force/torque/touch sensors, motion capture, pose estimation, power supply, RFID, and sensor interfaces.
In ros.org site, in addition to all packages, there are also extensive tutorials and a discussion board that one can ask questions and share knowledge.
ROS also has an industrial section, the version of software modified for industrial applications. It is called ROS industrial, and can be reached at: http://rosindustrial.org/. Although we see domestic robots with new abilities or advanced research projects that aim to develop capabilities of robotics every year, according to the results of a study that is shown on http://rosindustrial.org/the-challenge/ website, the abilities of industrial robots are not progressing and the abilities are restricted to welding, material handling, dispensing, coating (although we know that they do additional tasks such as packaging, inspection, labeling etc…). ROS Industrial aims to solve this challenge by providing a common skeleton to all developers, with its extensive and stronger software architecture, than other individual robotics programs.
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