Micro-Sized Servo Drives: Big Things in Small Packages

A Shrinking Feeling

Gordon Moore in front of semiconductor wafers

Gordon Moore, creator of Moore's Law

Right now, chances are you're carrying a smartphone less than a centimeter thick with more processing power than the computers that were used to guide the astronauts to the moon. How did we get here?

In 1965, Intel co-founder Gordon Moore stated that the number of transistors fitted in a dense integrated PCB circuit doubles every two years. “Moore’s Law,” as it came to be known, held up for over 50 years of innovation.

While the rate of shrinking has begun to level off in recent years, electronic circuitry is still steadily getting denser. For those of us in motion control, this means providing lighter, smaller, and more powerful micro-sized servo drive solutions to engineers.


Why Do We Need Smaller Servo Drives?

Yes, innovation has allowed us to create very small servo drives. Drives that are not only more compact and intelligent than the bulky amplifiers that came before, but also with higher power density so they can still provide the necessary torque and speed to motors. But we don't make micro-sized servo drives just because we can; there are benefits to having compact servo drive solutions.

As robots are becoming smaller, sleeker, and more intricate, we need smaller servo drive solutions that will fit inside them while delivering the same performance. This isn’t just a matter of aesthetics, smaller and lighter servo drives are better for performance.

Let’s take the example of a simple cobot arm with multiple linkages. Each additional segment means one more motor and one more drive in each joint. Whenever a motor in a joint rotates, it has to provide enough torque to lift the linkages that are further from the cobot’s base point. Therefore, reducing the weight of the servo drives alone reduces the necessary energy consumption of the robot and makes it more efficient.

Yellow robot arm with servo drives weight indicated in joints

Having lighter servo drives in the joints reduces the torque required to lift the arm

Now one might say, “why not just mount all the servo drives at the base of the robot instead of in the joints?” This is theoretically possible, but not very practical. Installing the servo drives with their respective motors in each joints not only is convenient for maintenance purposes, but it also alleviates the need to run different lengths of motor phase cables and feedback cables all the way through the robot arm. This would not only prevent a maintenance nightmare of having to trace a set of cables throughout the entire arm, but it would also prevent electrical noise-related feedback issues.

For the purposes of manufacturability and reliability, it's much better to have compact, light servo drives that can mount with the motors in each joint.

Multiple orange warehouse robots in warehouse with battery icons indicating charge level

Smaller servo drives mean less dead weight wearing robots out.

Beyond fixed robotics, smaller servo drives are also useful in mobile robotic applications. Similar to the cobot example, having small, light servo drives on board can cut unnecessary weight to improve efficiency and/or allowing more room for a larger battery. Either way, the end result is a robot that can work harder and longer throughout the day.

Cutting weight is often essential in medical and military industries as well, particularly with equipment that needs to be portable. In aerospace applications, finding lightweight solutions is critical for reducing fuel consumption in the battle against gravity.

Product Highlight: FlexPro®

FlexPro servo drive

FlexPro FE060-25-EM digital servo drive

FlexPro® is ADVANCED Motion Controls' newest family of digital servo drives. Most of these servo drives are “micro-sized.” With cutting edge engineering, FlexPro is meant to expand the capabilities of AMC’s already powerful and diverse product selection into applications with smaller space constraints.

At just 1.5 x 1 x 0.6 inches (38 x 25 x 16 mm) in size, the footprint of a micro-sized FlexPro servo drive is approximately the same as two standard postage stamps. In other words, four of these drives can fit on a standard business card. For example, the FE060-60C-EM can supply brushed, brushless, stepper, and linear servo motors with up to 60 amps continuous current.

Tiny Servo Drive PCB next to Pencil

Features for micro-sized FlexPro models include:

  • Peak and continuous current ratings up to 60 amps
  • 10-55 VDC or 20-90 VDC input
  • Highest power density servo drives from ADVANCED Motion Controls to date
  • EtherCAT, Ethernet/IP, CANopen, RS485/232 Communication
  • Supports incremental encoder, BISS C-mode, EnDat, Tamagawa, and hall sensor feedback
  • Torque, velocity, and position operating modes

Okay, Then Why Aren't All Servo Drives small?

group of variety of servo drives

Despite advancements in power density, servo drives still come in a variety of sizes

With many micro-sized servo drives available and their benefits apparent, you might be wondering why ADVANCED Motion Controls and other servo drive companies continue to market and sell larger servo drives. It’s a fair question, and there are a couple of reasons.

Power Density Limitations

As observed with Moore’s law, electronics are continuously becoming more compact. However, unlike most computer components, servo drives don't just have to perform logic functions– they must actually transmit enough power through the PCB to drive a motor.
For high power motors, this requires a lot of current, and there's only so much current that you can pump through a small circuit board without components getting damaged from overheating, even with cooling fans, heat sinks, and other thermal management techniques.

In addition, as voltage increases, the required spacing between traces on a printed circuit board also must increase to prevent noise interference or even arcing.

Even as the possible power density within the PCB itself improves, finding reliable motor and power connectors that can handle high current output without melting while still fitting neatly on the servo drives becomes a limiting factor.

For heavy duty motion control applications, you simply need bigger, heavy duty servo drives.

Cost vs. Necessity

3 men working on machine

In large machines, micro-sized servo drives aren't necessary and are sometimes impractical.

The other factor is cost versus necessity. In many cases, less compact drives can actually be easier and less expensive to manufacture, so naturally they can be priced lower. Small drives can be very nice, but if the application doesn't have tight space constraints, a larger but lower-priced drive can suffice.

If you’re designing a large gantry system that has plenty of space for a big servo drive to be mounted, then there’s no sense paying the extra money to have a tiny servo drive that will have virtually no effect on performance.

Sometimes, having a bulkier servo drive isn’t just acceptable, it’s actually preferable. Imagine having to stick your upper body deep into a large manufacturing machine for maintenance. Do you want to spend 10 minutes bent over trying to connect dozens of tiny clip connectors with crimped pins, fiddling with them in the bad lighting, or do you just want to screw in the power leads and a couple D-Sub connectors and be done in 30 seconds?

The demand and uses for smaller drives are certainly expanding, but the need for large drives certainly isn't going away either.

Product Highlight: µZ

µZ (Micro-Z) drivesA subset of AxCent servo drive family, the µZ (Micro-Z) drives are tiny analog PCB-mount servo drives. For those seeking an especially lightweight solution for applications with centralized control schemes, these little drives are the way to go.

µZ servo drives are designed to drive brushless and brushed DC motors at a high switching frequency. To increase system reliability and to reduce cabling costs, the drives are designed for direct integration into your PCB. Weighing in at just 8.5 grams, µZ Drives output 10A peak and 5A continuous and operate with a bus voltage range of 10-36VDC.

tiny micro pcb servo drive

μZ AZBDC10A4 analog servo drive

Features include:

  • Designed for direct board-to-board integration.
  • No heatsink and no need for additional heatsinking results in the smallest installed volume
  • Feather weight, 8.5 grams
  • Dimensions: 1.50 x 1.50 x 0.29 in (38.1 x 38.1 x 7.34 mm)
  • Compatible with low inductance motors
  • ±10V or PWM/Direction command signals
  • 40 kHz switching frequency

Final Thoughts

FlexPro Servo Drive PCB and machine mount groupMicro-sized drives are perfect for cobots (collaborative robots), AGVs, fixed robotics, mobile robotics, animatronics, portable devices, lab automation, military equipment, aerospace, medical equipment, and truly any application that requires a compact and/or lightweight embedded solution.

Are you working on a project that could use a micro-sized servo drive? Contact us and we'll find the drive that works best for you. ADVANCED Motion Controls' µZ and FlexPro™ servo drives are all standard products, but if you're looking for a micro-sized solution, your options aren't limited to those. We're happy to develop custom micro-sized servo drives, including ones that use the same IMPACT™ architecture that makes FlexPro™ possible.

The need for smaller servo drives is only going to increase in the coming years, and anyone who knows us knows that we are always up for task. Bring it on.


by Jackson McKay, Marketing Engineer

Interested in Micro-Sized Products? Be sure to check out...

FlexPro Info Box
AxCent Info Box
Custom & Modified Servo Drives