Robotic Arms Embrace Precision, Reliability, and Safety

Robots can go where humans can’t, either for safety or practical reasons. They can achieve levels of precision or repeatability to augment or simplify the work that people do. The right connectors make them efficient, durable, and reliable.

Complex robots are deployed in a wide variety of applications — in industrial and manufacturing facilities, hospital surgical suites, oil & gas drilling rigs, and in space on the ISS and rovers that explore planetary surfaces. Robotic arms can be programmed or controlled to manipulate objects and perform extremely precise movements.

Whether downhole in a drilling site or performing surgery, these robots require highly reliable connections. Past this, robotic arms with multiple joints have very tight weight constraints that mean designers need to reduce mass as much as possible, said Eric Bergquist, project engineer at Omnetics Connector Corporation. “The farther you get away from the attachment point, the more torque a small amount of mass will generate. Mass at the end of an arm has a disproportionate effect on the dynamics of the robot compared to mass at the base. When you have a robot arm with multiple successive axes, the mass constraints get more and more critical as you go out to those farthest extents of the arm.” That’s where high reliability, miniaturized connectors are needed.

The Polarized Nano series is Omnetics Connector Corporation’s most compact arrangement yet. The insulators are designed to hold one row of pins and one row of sockets. This configuration effectively polarizes the connector without the additional space required for guide pins.

In addition to the connectors, the concerns about mass also impact how signals get to those actuators efficiently. “When there are several very complex linkages stacking up, you need high-flex cable harnesses that are small enough to fit into whatever small channel is built into the design, so that you don’t have wires hanging externally off the robot. Instead, they are routed through the mechanism itself,” said Bergquist. He further explained that, often, very small end effectors require surprising large infrastructure to support them. This is the case in many surgical robots.

“You basically have a whole bank of heavy actuators that are responsible for all the motions the robot needs to make. These actuators add up, as surgical robots can have many more degrees of freedom than standard industrial robots. With smart mechanical design and linkages, all that heavy infrastructure can be moved to the periphery, so the actual tools that are used all the way down in the surgical site can be as small as possible,” Bergquist said. “It is unlikely that you could, for example, add a servo actuator right where you need a little gripper to pull the flap of skin back. So, instead, you run a mechanical cable. This is not electrical, but just a physical loop of cable going down to the gripper and back up to the main body of the robot. You run that cable to an actuator that can be much larger than the gripper, and when that actuator turns the cable, the motion translates all the way down into this tiny little pincer, without completely blocking all the other tools in the surgical site from doing what they need to do.”

Robots in space have additional concerns. Anything going into space is exceptionally mass constrained so it can’t have that luxury of a large bank of equipment off to the side. Launch costs are a major factor that directly impacts size, weight, and other design issues. A robot going up in a rocket needs to meet a very strict payload limit, say, 2,000 kg. It not only has to be designed with a small enough mass to get to orbit but must also be able to handle the vibration and shock load that results from a rocket going to space. A robot in space also requires significantly more autonomy. “Unlike surgical robotics, which are often controlled directly by an operator, the robot arm on the Perseverance rover, for example, has a massive communication delay that can’t be overcome. Whatever the rover is going to do has to be pre-programmed so it can complete the tasks on its own. Any problems that arise will be resolved through clever programming or activity will stop until a human can provide an alternate plan,” said Bergquist.

Miniaturization is a huge driver for customers. They want the same reliability they have had for decades with larger connectors, like the Micro-D, and environments are just getting tougher. “By standard, we have products that can survive up to 125 °C and we have a high-tech line of high-temp products that go to 200 °C, but customers are pushing that to 260 °C. Space customers want to put connectors as close to a rocket engine as possible, so they’re asking for 300 °C,” said Bergquist. “That eliminates a lot of materials that won’t survive those conditions. So, we keep redesigning and redesigning until we’ve got all the materials that will survive.”

Adam Tech discrete spring loaded pins are manufactured with precision from the highest quality brass barrels and plungers, supported by industry leading spring steel for long life cycles and high reliability. Pins come in a wide range of heights, stroke length, mounting orientations, and electrical capabilities.

Spring pins are another advantage in applications like industrial assembly and automotive assembly lines. “A connection is made between a spring pin connector and a pad connector. It’s a solderless connection between two gold-plated surfaces that make a good electrical connection simply by the pin touching the pad. It’s very user friendly,” said Martin Houlroyd, FAE and business development manager at Adam Tech. “A robotic arm could reach over to a carousel that has different types of tools and pick the one it wants. The pad connector might be attached to the tool and the spring pin connector attached to the arm. This allows the arm to easily swap out, for example, a drill and a screwdriver. The spring pins allow for a quick, secure electrical connection. No wires need to be attached and nothing has to be screwed down.”

The simplicity of the spring pins adds a level of flexibility for designers. Robot vacuums are a good example of this. “A traditional type of pin and socket must be fully aligned. This might mean someone would have to physically take the robot and plug it in. But in this case, the robot just roams over to the docking station with these pins sticking out and just makes contact. There are no wires and no soldering required. You don’t have to bolt it down. You don’t have to plug anything in. And misalignment is not an issue. it doesn’t matter where the pin touches the pad. And since this is a spring pin, it compresses so it can make contact with an uneven surface. This is a very forgiving technology.”

At electronica 2024, Weidmüller showcased a robotic arm with SNAP IN, the  connector that is capable of precision manufacturing tasks. See it in action.

To learn more about the companies mentioned in this article, visit the Preferred Supplier pages for Omnetics Connector Corporation, Adam Tech, and Weidmuller.

Like this article? Check out our other High-Reliability and Miniaturization articles, our Industrial Market Page, and our 2024 and 2025 Article Archives. 

Subscribe to our weekly e-newsletters, follow us on LinkedIn, Twitter, and Facebook, and check out our eBook archives for more applicable, expert-informed connectivity content.