Connectors for robotics and automation apps

Trends and issues designers should consider when selecting a connector for this unique market

BY RALPH C. RAIOLA

While robotics and similar applications still have not evolved to the level of human companionship offered from the likes of C-3PO from the original Star Wars films or the robot from the Lost in Space television series, as a society we are more reliant than ever on robots and processes driven by automation. Robots are everywhere — in the military, the hospital operating room, underwater, on the factory floor, and even in our homes — performing a variety of functions as varied as defusing explosive devices, exploring the farthest reaches of space, and cleaning our living room floor (see Figs. 1 and 2 ).

Fig. 1. Robots in NASA's Robonaut program assist astronauts (far right) with various tasks.

Fig. 2. Harwin's Datamate Mix-Tex connector was used to handle signal and power in an award-winning robot from Warwick Mobile Robotics, part the University of Warwick's School of Engineering.

Depending upon the robot’s design and ultimate use, various connectors are integral to the functionality in these applications. As such, many different requirements exist.

The connector inside the robot

For instance, robot hands, which operate via millivolt sense and touch circuitry, require light and small cable and connectors to carry signals to the end of a finger or similar crimp-like structure. Motor connectors that move a finger or hand require more robust, lockable designs that can sustain residual torque motion and handle micro-amp capacitance. For a circuit that controls a rolling track or for motors that drive an entire robot, connectors are typically bigger so they can handle larger current capacities.

When a robot is destined for deep-space applications, designers may need to select a connector in which the manufacturer controls the outgassing of materials used. “If the deep-space application is board-mounted, we consider the thermal coefficient of expansion and contraction to the board’s to ensure the assembly does not tear itself apart during geothermal navigation temperature change,” says Robert Stanton, director of technology at Omnetics Connector, a Minneapolis, MN-based connector manufacturer.

Power and signal connections are most often found in today’s robotics devices. However, Ethernet and networking are trends. When high-speed data processing is required, it is necessary to select RF connectors and cable that are shielded against EMI/RFI. But if the circuitry already supports RF, analog signals can be handled with standard matched-impedance cables.

“Digital signals are handled somewhat differently as the speed rises above 480 Mbits/s and as the length of the cable increases,” Stanton says. For digital data transfer, connectors are often custom-designed and designers should involve themselves in the testing process early on to optimize impedance and overall digital performance.

Harting, an Elgin, IL-based connector company, is seeing a “renewed focus on modularity and also easy serviceability,” says Edmund Garstkiewicz, Harting’s market development manager. “Flexibility in design requirements and the ability to add performance without having to change the footprint of the selected design is important as well.” Harting’s Han Modular connectors were created to enable designers to build a custom hybrid connector from standard parts (see Fig. 3 ).

Fig. 3. Harting's Han-Modular connector lets robotics designers customize and combine data, signal, and power capabilities in one connector.

Size matters

As in most other applications, available space is a major issue facing robot and automation designers, who are beginning to turn to hybrid connectors to handle both power and data. “Hybrid connectors are often specified as there is a need to keep size and weight to a minimum,” says Bill Neukomm, vice president for sales and marketing at Salem, NH-based Harwin.

For Harwin, the demand for smaller components is also pushing the company toward developing a 1-mm version of its Datamate products to achieve greater pin density.

Omnetics offers custom connectors that mix micro- and nano-sized pins and sockets to help designs in which real estate is an issue. “These are often used in robotics to reduce the number of cables routing about the inside of robot,” says Stanton. “Large-pin sockets handle the higher current and robust applications while the nano-sized sets handle micro-volt analog signals and low-level digital signals.”

On the factory floor

Robots used in manufacturing can have very different connection requirements than the walking, talking, clanking metal devices that are prevalent in YouTube videos or at university design contests. On the factory floor, the most important place for connectors is between robot and cabinet, according to Garstkiewicz.

“Because the robot is usually not a standalone solution and has to be implemented into a manufacturing process, further consideration must be given to the connections at the cabinet for communication purposes with other devices like feeder units, turning tables, etc.,” Garstkiewicz says. “So, overall system requirements must be taken into consideration, as well as existing connectivity requirements on these other units.”

Following the designs

Chip design and innovation, of course, is the driving force behind robotics and automation functionality, and interconnects are vital to the enablement of robots to do the bidding of their masters.

“Chips are dramatically increasing their complex functions and that increases the demand for more and more interconnection wiring, but at lower and lower current and voltage levels,” says Stanton. “Chips are also moving nearer and nearer to the functions or applications they support. Since this moves chips from deep inside the box to ‘out-there’ at the data acquisition point, a new demand on connectors is that they must be very small, fast, and very rugged.

“This is why high-reliability nano-connectors are one of the fastest growing connector market segments in the industry.”

Rugged and reliable

Due to the harsh conditions and environments in which robots and automation equipment must perform, connector manufacturers note reliability and ruggedness as key features to look for when selecting an interconnect. “The overriding requirement is for high reliability, since robotic applications often function is harsh environments,” Neukomm says. “The connectors used must be rugged, capable of withstanding high levels of shock and vibration and wide extremes of temperature.”

Fig. 4. NASA is using multiple Mix-Tek Datamate connectors in its Robonaut humanoid robotic systems.

When NASA chose Harwin’s Datamate connector for its Robonaut 1 and 2 programs (see Fig. 4 ), it was the device’s reputation as a military-grade component capable of performing in harsh environments that won it the job. “It is vital to consider the operating conditions. Shock and vibration, and temperature range determine the level of product which is appropriate,” adds Neukomm. “Also important are the presence of contaminating substances such as cleaning fluids, bodily fluids, oils. Humidity can [also] be a factor.”

According to Garstkiewicz, IP67-rated Ethernet solutions are becoming more common as well.

The selection process

Robotics applications must be small, rugged, capable of unique functionality, and able to operate in non-traditional environments. Even the large automation equipment on the factory floor is subject to the size requirements.

Stanton recommends a process, in which the design engineer:

• Defines the application, function, and environment thoroughly.

• Defines the circuit’s electrical performance, as more precise specifications will aid in cable and connector selection.

• Reviews standard designs to find off-the-shelf connectors that meet most of the criteria, such as size selections, current level, reliability, and price.

• Establishes the custom design process with the manufacturer when no current design exists, to move quickly to a new shape or design that can be sent via e-mail to the designer.

Ready-made for your application

Custom products are a growing trend, though buying off the shelf remains the predominant way in which designers specify connectors for today’s robotics applications. For Harwin, around 25% of the products they sell into these markets are custom. Stanton concurs, and sees that part of the business growing. “We used to be at 75% off the shelf,” he says. “But we are moving way beyond that number as designers begin with the commodity and add an overmold, change a shape, or ask for a different latching feature.”

While anything made to order carries a premium, Stanton encourages designers to get away from thinking they are limited to only what they see in the pages of a catalog. “We now manufacture miniature and nanoconnectors to custom designs,” he says. “This allows significant freedom in form and function of the interconnection system. Designers should call and ask, “Can you design a connector for us?”

Customization is also affecting the entire design process, Stanton adds, with manufacturers and designers engaging in online interactive design to work together. “Together we quickly and efficiently match the best elements of a proven connector to new shapes and latching systems to meet the needs of newly designed modules in the robotics and automation fields. We see brand new connector designs weekly, each specialized to the demand of the system designer at the other end of the e-line.”

Testing

Because of the unique environments in which robots must perform, the components used must meet extreme requirements. Designers would do well to ensure that they see “test data covering all the aspects of electrical and mechanical performance as well as comprehensive shock, vibration, and temperature behavior,” Neukomm says. Some manufacturers even test the materials used in the interconnects, such as the outgassing example mentioned previously.

Custom designs, however, require the engineer and manufacture work closely together, and this extends to the testing phase. “Custom designs and applications should be tested to some functions that fit the specific applications,” Stanton says. “This is a key role between design engineer and component supplier.”

Cost

Component cost is a major driver in robotics, as it is in every other market. “A premium is sometimes paid for performance and reliability for connectors in robotics as the cost of downtime — be it maintenance or installation — is high,” Garstkiewicz says. In the end, it really depends on the application. If a robot is going to be marketed to the average consumer, it must meet certain pricing requirements to be competitive, as opposed to high-reliability applications, where expectations are for prices to be higher. ■