With Two Arms and a Smile, Pi4 Workerbot Is One Happy Factory Bot

pi4 workerbot

Is this robot the factory worker of the future?

The pi4 Workerbot is a new industrial robot capable of using its two arms to perform a variety of handling, assembly, and inspection tasks. It's designed to work alongside human workers --  and the robot's LCD face even displays a broad smile when things are running smoothly.

The robot is a creation of German firm pi4 robotics in collaboration with the Fraunhofer Institute for Production Systems and Design Technology, in Berlin.

pi4 workerbotOne of the innovative things about the robot is its control system. The Workerbot, which made its debut at the Automatica show last June, relies on a method known as impedance control, which allows the robot's arms to cooperate as they handle objects, keeping forces at desired levels and adjusting to disturbances -- a crucial capability when it comes to bimanual manipulations.

With its human-inspired size and looks [see images above], the Workerbot is a far cry from traditional factory bots, especially those used by the auto industry.

That's not to say that the automotive industry hasn't been good to robotics. Quite the opposite. Thanks to car manufacturers, industrial robots evolved into fast, reliable, powerful, and precise machines. But there's a flip side to the story.

Traditional industrial robots are rather complex to integrate into existing manufacturing processes; deploying them at a factory is an arduous, costly, and time-consuming task. The robots are also difficult to reprogram when changes become necessary, and they can't safely share spaces with human workers.

This barrier to entry has kept small and medium companies in industrialized countries "robot-less" -- at a time when robots, more than ever, could boost productivity and ameliorate labor shortages. To automate their production lines, which often include many different items manufactured in low volumes, these companies need robots that are inexpensive and intuitive, but still reliable and precise.

This is a promising, and potentially hugely lucrative, market that pi4_robotics and other companies -- including, it appears, Rodney Brooks' secretive start-up, Heartland Robotics -- want to explore.

The Workerbot's arms have seven degrees of freedom each (like humans arms), with grippers equipped with force sensors that can adjust the pressure that they apply. The head has two inspection cameras on the sides, a 3-D camera on the forehead, and a display screen that provides feedback to operators (a smile means all is okay; a frown indicates that something is wrong, or that the robot could work faster). The Workerbot is not a mobile robot, though human workers can use its wheeled base to move it manually.

Watch the robot in action:

According to Fraunhofer engineer Dragoljub Surdilovic, their approach to compliant control is what makes the Workerbot different from similar two-armed bots, like the Motoman SDA10D and the DLR/KUKA Justin humanoid.

"We created a new dual-arm programming language and environment that incorporate impedance control and make it easier to plan, program, and realize bimanual contact tasks," Surdilovic says.

Most industrial robots don't use impedance control, but rather they implement position control. In this approach, the robot tries to make its arms follow as closely as possible a series of positions in space. If the arms go off their trajectory, the motors try to bring them back on track.

The problem is, if you have two robots, or one robot with two arms, that need to collaborate and they are position controlled, coordinating their movements can be difficult. Imagine that the two arms are manipulating the same object. If at any point one of the arms becomes off-trajectory and starts pushing to get back on track, the other arm might go off-trajectory and start exerting forces as well.

Using impedance control, bimanual manipulation becomes much easier. The way this scheme works is the robot simulates a dynamic behavior for its arms that is different from the arms' intrinsic mechanical dynamics (which depends on its linkages, motors, and joints). The idea is to actuate the motors by simulating a mass-damper system. Imagine moving an object through a viscous liquid. The control system can adjust its parameters so you feel that you are moving a greater mass, for example, or add more damping so you don't overshoot when trying to bring the arm to a given position.

The upshot is that impedance control makes the arms capable of adjusting to errors and disturbances while at the same time keeping applied forces within desired limits.

This approach is also key to improve safety, because the robot won't push back if a person accidentally comes into contact with it. Indeed, the Workerbot meets the ISO 10218 norm for "inherent safe design of industrial robot." Another important benefit is that human operators can manually guide the robot arms to teach it an assortment of tasks, simplifying the programming process.

It will be interesting to compare the Workerbot to the Heartland Robotics system. Both companies seem to target assembly, handling, and inspection tasks. Whereas pi4_robotics claims that its bot will "help keep European production competitive," Heartland wants to "reinvigorate American manufacturing." The German firm plans to lease their robot for about 4,800 euros per month, and recent reports indicate that Heartland might sell its robot for US $5,000, although details are still murky.

One thing is certain: This is going to be an exciting chapter in robotics, and I'm looking forward to seeing how things will unfold -- and most important, whether these robots will help the many manufacturers that have long awaited for them.

Images: Copyright pi4_robotics

Samuel Bouchard is a co-founder of Robotiq Gripper, in Quebec City.

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