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One-armed manipulation robot runs Linux and ROS

Mar 24, 2015 — by Eric Brown 2,864 views

Rethink Robotics’s one-armed, Linux- and ROS-based “Sawyer” manipulation robot is smaller, faster, stronger, and more precise than the earlier Baxter.

When MIT spinoff Rethink Robotics announced the $25,000+ Baxter manipulation robot in 2012, it inspired a whole new category of small, relatively low-cost robots for light manufacturing and product assembly. The fixed, two-armed, “collaborative” robot broke new ground in the flexibility of its arms and grippers, as well as the Linux-based Intera software. Intera integrates algorithms that enable the robot to quickly learn new tasks and safely work alongside humans.

The new $29,000 and up Sawyer is both a next generation follow-on to the Baxter as well as a sibling and potential coworker. It only has one arm, instead of two, but it’s smaller and lighter, and its arm is faster, stronger, and more precise.

Rethink Robotics Sawyer
(click images to enlarge)

Sawyer can take the place of a human in a tightly packed assembly line and perform functions like machine tending, material handling, and circuit board testing, which are difficult or impossible for the larger, less adept Baxter. Like Baxter, Sawyer can learn tasks by having a human guide its arm in a process called “train-by-demonstration,” and it can similarly work side by side with humans without causing harm, says Rethink..


“Baxter is ideal for material transfer and packing, whereas Sawyer is better designed manipulating parts coming down a conveyor,” said Rethink Robotics Research and Academic Product Manager Brian Benoit in a brief interview with LinuxGizmos. “Baxter will feed the conveyor belts and then Sawyer will do the work. Then Baxter can take over at the other end of the line to move the products.”

Sawyer runs the same Intera software, which combines Linux with Robot Operating System (ROS) code. The difference is that Baxter’s “brain” is onboard, whereas the Sawyer is tethered to a separate embedded control computer, explained Benoit. The change was made in order to keep the robot small and light, said Benoit.The tether does not significantly impact latency, he adds.

Neither Benoit nor the Sawyer product page revealed any more about Sawyer’s control computer. Baxter, on the other hand, is fully documented. It features a 3rd Gen Intel Core it-3770 processor with 4GB of DDR3 RAM and a 128GB SSD. On the Baxter (and presumably the Sawyer, too) an Intel Core based workstation running Ubuntu 14.04 and ROS Indigo is required for programming and maintaining the robot. The PC does not need to be connected during standard operation.

Sawyer offers the same safety, compliance, and usability advantages of Baxter, as has essentially the same, but updated, animated “face” screen for communicating the robot’s state, says Rethink Robotics. The bot is said to be similarly capable of “dynamically adapting to real-world conditions on the plant floor and integrating seamlessly into existing work cells.” According to Benoit, the ability to fit into the workspace and better mimic the capabilities of human hands greatly reduces integration costs in factories compared to other manipulation robots.

Sawyer hardware details

The 5 x 2 x 2-foot Sawyer weighs only 19 kilograms (42 pounds) compared to Baxter’s 165 pounds. Yet, Sawyer can support a 4 k (8.8 lb) payload, compared to only 2.2k (5 lb) for its older sibling. Unlike Baxter, Sawyer is IP54-protected protected against dust and spray.

The robot also features an informational display, which features the animated face. In addition, manual controls are embedded in the arm.

Sawyer gripper and elbow
(click images to enlarge)

Like Baxter, Sawyer has a wide-view camera in its head. The new robot adds a Cognex camera attached to its wrist with a built-in light source and the capability for precision vision tasks such as “dynamic re-orientation,” says Rethink Robotics. In the future, it will support more advanced features such as barcode scanning and object recognition, says the company.

The robot arm has a 1-meter reach, and features 7 degrees of freedom. Like Baxter, Sawyer’s arm is built around the series elastic actuators, similarly enabling compliant motion control. However, the arm has been redesigned, according to an IEEE Spectrum interview with MIT robotics wiz Rodney Brooks, the founder, chairman, and CTO at Rethink Wireless, as well as the co-founder of iRobot.

Sawyer controls and base
(click images to enlarge)

Sawyer’s arm incorporates “S” shaped springs made of titanium instead of the earlier, steel-constructed “C”-shaped springs. The new spring design, along with new cabling between joints and the addition of high-resolution force sensors embedded at each joint, enables the robot to “feel” its way into fixtures or machines, even when parts or positions vary, says Rethink. The arm is also said to feature Harmonic Drives in each joint to greatly reduce backlash, further adding to precision and durability.

Whereas Baxter is primarily an academic research robot, and has only sold in the “hundreds,” according to IEEE Spectrum, Sawyer is going straight into factories around the world. A research version will follow, said Benoit.

Brooks told IEEE Spectrum that the chief market will be Chinese electronics assembly and testing facilities, which are seeing rising labor costs and high turnover. According to the Rethink’s Sawyer announcement, “Together, Baxter and Sawyer can address many of the estimated 90 percent of manufacturing tasks that cannot be feasibly automated with traditional solutions today.”

Unbounded Robotics

Baxter has influenced other manipulation robot firms, such as Fetch Robotics, which plans to release two ROS-on-Linux mobile manipulator bots in Q2 2015. Fetch essentially has the same core crew and leadership as the now defunct Willow Garage spinoff Unbounded Robotics. The latter developed a Linux-based UBR-1 manipulation robot for a surprisingly low $35,000 to $50,000, but never got it out the door. The new Fetch bots are expected to be somewhat similar in price and functionality.

“Rethink Robotics continues to lead the way in defining how workers and machines can coexist to leverage the strengths of each, and optimize productivity for all,” stated John Dulchinos, vice president of digital manufacturing at Jabil, an early adopter and field tester of Sawyer.

“Rethink’s Sawyer is a very compelling technology that has the potential to once again change the way manufacturers think about their automation infrastructure moving forward,” stated Dan Kara, robotics practice director at ABI Research.

Sawyer demonstration videos

The videos below were posted to YouTube by Baxter.

Meet Sawyer

Sawyer’s Robot Eyes

Further information

Sawyer is currently being field tested, and will retail for a base price of $29,000 starting this summer, with limited availability until later in the year. More information may be found at the Rethink Robotics Sawyer product page.

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