Servo Motor and Drive Technology Moves Ahead

According to a recent blog post by Michelle Figgs, senior analyst for industrial automation with analyst firm IHS, a couple of trends promise to have a significant impact on motion control decisions for machine builders and their customers.

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One is a change from analog to digital feedback signals between servo drives and servo motors. Traditional servo motors use an analog feedback signal that is susceptible to electromagnetic interference and must be housed in a separate cable from the motor’s power source, resulting in two cable inputs for each servo motor. An encoder that transmits feedback via a digital signal can eliminate the dual cable, allowing power and feedback to be housed within a single cable.

Single-cable encoder technology has existed in the marketplace for some time, says Figgs, but over the past two years the number of servo motor suppliers offering it has increased significantly. The benefits are clear. The elimination of a cable and its connection saves costs related to materials and installation. In addition, the digital feedback signal requires a much smaller number of terminations than the traditional analog signal. This simplifies wiring and increases the reliability of the connection.

Single-cable servo technology may be hard to find, however. “Despite the potential advantages of single-cable servo motors, this trend is still in its early stages, and many large suppliers do not yet offer this product,” Figgs says.

The servo drive market is also trending toward the incorporation of more safety features. Safe torque off (STO) is the most common feature offered and used, says Figgs. More advanced safety features include safe stop 1 and 2, safe limited speed, safe speed monitor, and safe direction.

Advanced safety features may be integrated into the drive—as STO typically is—or provided through optional safety hardware or software modules. “IHS found that SS1 was the most common advanced safety feature enabled on servo drive unit shipments in 2012,” she says.

Overall, there are more than 15 safety features being incorporated into servo drives, and the number of servo drive units shipped with safety features is forecast to increase significantly between 2012 to 2017, says Figgs. Safety implementations still vary significantly by region, however.

“In the Americas, STO has also evolved as a standard feature in servo drives, but it is still seen as a way to differentiate products rather than as an absolute requirement, as it is in Western Europe,” says Figgs.

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