Boston Dynamics created Stretch Gen 2 for reliable, consistent performance

Boston Dynamics Inc. this week introduced Stretch Gen 2, the latest generation of its autonomous mobile robot for unloading trailers. With more than 100,000 hours of operation and tens of millions of boxes handled under its belt, the company built the updated robot to maximize uptime and simplify maintenance.

This was said by Brian Donnelly, vice president and general manager of logistics robotics at Boston Dynamics The robot report that the company has been working on the new version of Stretch for about two and a half years.

“When we built the first generation of Stretch, we were focused on trying to get a product to market as quickly as possible, to really get it into the hands of customers and get it operational,” he said. “It wasn’t the easiest to produce; there were a lot of components.”

“[With Stretch 2]we were really focused on simplifying, strengthening the robot, and improving reliability and performance,” added Donnelly. “That’s what drove a lot of our decisions: making the robot better in every way.”

Stretch Gen 2 can unload up to 1,000 cases per hour. This rate depends heavily on factors such as the weight of the crates and how neatly or haphazardly the crates are stacked. It has a multipick function, a battery that can last two shifts, and a fast charger that can charge it to 90% in about 75 minutes.

The mobile manipulator is also equipped with on-board lighting, which simplifies working in dark trailers, and a pre-trained vision system that can detect most packages without the need for programming.

Stretch hardware upgrades improve durability

Boston Dynamics geared many of the Stretch Gen 2 upgrades to reduce downtime and make the robot more durable. For example, the Waltham, Massachusetts-based company also cut 81 percent of its internal wiring, or about half a mile.

“[Cabling] it’s the weight, the cost and its weaknesses, particularly when you have something that’s constantly moving, you create tension on those cables with every movement,” Donnelly said. “If you don’t have a good cable gland, you don’t have good ways to manage the cables in the robot. It can cause stress on the cables and therefore failures.

Donnelly said Hyundai helped the company source a harness through its automotive supply chain. That’s not the only thing Boston Dynamics has learned from the auto industry. Stretch Gen 2 uses heavy-duty automotive-style connectors. They resist vibrations resulting from fast, high-torque handling of the box and driving on uneven floors.

“In the automotive industry, their vehicles face a lot of real-world challenges. There are a lot of miles driven dealing with shock, vibration and things like that,” Donnelly said. “As a robot moves through the world, just like a car, if you don’t have connectors clipped together, they can kind of move around. By leveraging these automotive connectors, we’re much more confident that the connectors will stay clipped together and not come apart in the field.”

The robot is also equipped with continuously rotating joints that move beyond 360° so that it no longer suffers sudden stops. This can help prevent previously caused mechanical stress. Donnelly pointed out that this also makes the robot more productive, as it can fully optimize trajectory planning and move in any direction.

The robot’s emergency stop is now lower and recessed. Boston Dynamics made the exterior panels from new materials so that a falling box is much less likely to trip you into an inadvertent safety stop or break a panel.

How Stretch Gen 2 manages to tick more boxes

The gripper is the part of the robot that is often subjected to the greatest stress. It’s coming into contact with all the things the robot needs to handle. Stretch Gen 2 features an updated gripper with new valve systems, and more precise sensing improves grip and positioning to optimize fast-paced picking.

“[The new gripper] has value in each suction cup, which allows us to pick up more boxes with a single arm movement, which substantially increases our productivity,” Donnelly explained. “If we can pick up more boxes, with a single arm movement, we get much higher productivity because the cycle of picking a box off the floor of a container and placing it on a conveyor is dominated by the arm movement. So if we can keep the arm moving and do more with each cycle, that will be really effective and improve the speed at which we can unload a truck for our customers.”

The new gripper is also able to better configure boxes on the conveyor in a way that best suits Boston Dynamics’ customers and uses less energy to grip the boxes.

“Each cup is individually detected and activated, so we know when we have good suction,” Donnelly said. “We have the value open to only vacuum when we have good contact on a box, so we can reduce the amount of energy we’re spending running the vacuum pump, so we’re not vacuuming through suction cups that don’t have good contact. It also allows us, when we pick up multiple boxes, to single them out on the conveyor.”

Stretch Gen 2 reduces service times to just a few hours

With Stretch Gen 2, Boston Dynamics didn’t just want to reduce the frequency of service calls; he also wanted to make service calls faster when they occur.

“We didn’t have the same experience from a maintenance perspective as a company when we built the first generation robot,” Donnelly said. “We have since deployed these robots, maintained them in the field, and hired many people who have much more experience than we originally had in service. Their input and guidance has really helped us make a much more manufacturable, more maintainable robot.”

The robot does not require dynamic cables and complex wiring. Instead, it uses standardized, high-strength fasteners to reduce tool changes and hands-on repair times. For example, the company can perform a complete replacement of the steering transmission in just an hour. Previously, this process could take an entire day.

Stretch Gen 2 also features new built-in diagnostics and maintenance tools. These put more routine services in the hands of the customer’s maintenance team, so the robots remain on the dock with less reliance on external support.

The updated robot continuously improves its performance

The new robot runs on a redesigned and constantly improving on-board computing platform. Boston Dynamics said it will regularly release software updates to bring improvements in case detection, motion planning, selection strategies and world modeling across an entire fleet, with no hardware changes required.

Donnelly said that with the company’s most recent update, a 24% increase in unloading speed was seen across its fleet of field robots.

“A lot of our work on this program is software-focused. We’re constantly improving our computer vision capabilities to be able to better sense boxes, conveyors and container walls, and then actually pick out boxes and position them to deliver more and more productivity over time,” Donnelly said.

Currently, Donnelly said Boston Dynamics releases new software, on average, on a monthly basis.

How have customers reacted to Gen 2 so far?

Donnelly said Boston Dynamics already has Stretch Gen 2 running at several customer sites.

“Customers are really happy with it and continue to rely on it to do their jobs every day,” Donnelly said. “We will go into these existing sites and deploy these robots within two weeks. The people who will be operating the robots are the people who would otherwise be doing the heavy, repetitive lifting of these boxes and containers.”

“We put a lot of effort into making sure that the user experience, from an operator perspective, is really simple. It doesn’t require a lot of training,” he added. “A person can drive the robot into a container, exit the safety work cell, and press a large Play button, then the robot does the rest.”

Many of the people who worked with Stretch spent their days unloading heavy boxes from trailers.

“Basically, unloading trailers is one of the worst jobs in the warehouse,” Donnelly said. “It can be very hot in a shipping container that sits in a backyard in the summer. It can be very cold in the winter. Then the work itself involves repeatedly moving heavy boxes from below or above. This puts a lot of strain and stress on people’s bodies.”