How to Achieve Micron-Level Accuracy with Stepper Motors

In high-precision automation environments like semiconductor manufacturing, even the smallest error can lead to costly defects and downtime.   What if you could deliver servo-like precision without the complexity or cost of servo motors?

What's covered?

• The Precision Challenge in Automation
• The CVD Series Fully Closed-Loop Control Type Driver: A Game-Changer
• How Does It Work?
• Application Example
• Summary

Automation engineers are increasingly challenged to meet tighter tolerances in compact systems.  For machine builders who do not like the complexity or cost of servo motors, there is an alternative.

Oriental Motor’s Fully Closed-Loop Control Type Driver brings stepper motor accuracy to a whole new level by integrating high-resolution encoder feedback for micron-level stop accuracy and vibration-free positioning.  It delivers servo-like precision without the complexity of a PID loop and presents a complete solution for automation engineers who need accuracy, simplicity, and performance in one package.

The Precision Challenge in Automation

Stepper motors are known for their precision, ease of control, and ability to maintain position.  In an open-loop system, a stepper motor simply rotates a certain number of steps, which is dictated by the number of pulses received at its driver.  Speed is determined by the frequency of pulses, and torque is determined by the driver's current setting.

Traditional open-loop stepper motor limitations include positioning error due to missed steps resulting from undersized motors, and lack of encoder feeback can lead to unreliable position control under dynamic loads.  Adding encoder feedback resolves this issue, however, to correct position accuracy at the micron level, a special type of driver is necessary.

Where Micron-Level Accuracy Matters

• Precision applications such as semiconductor wafer handling, medical diagnostics, and precision inspection
• Miniaturization demands tighter control over motion endpoints

The CVD Series Fully Closed-Loop Control Type Driver: A Game-Changer

The unique advantage of the CVD Series Fully Closed-Loop Control Type Driver is its ability to fully integrate with a high-resolution encoder and provide position correction at the micron level.

Developed for linear encoders, the Fully Closed-Loop Control Type Driver combines the high-resolution feedback from encoders, microstepping from the driver, and fine step angles of a 5-phase stepper motor to offer micron-level positioning accuracy.  

What Encoders Does The Fully Closed-Loop Control Type Driver Accept?

• Rotary encoder with resolution from 100 to 16,777,215 P/R 
• Linear encoders with resolution from 1 to 50,000 nm
• Compatible with encoders from manufacturers like Mitutoyo, Heidenhain, Magnescale, and Renishaw

The encoder resolution can be set with the MEXE02 product support software or by Modbus (RTU) network commands.

What Are The Key Features Of The Fully Closed-Loop Control Type Driver?

• Lowest vibration and noise with advanced microstepping
• Microstep resolution settings from 100 to 125,000 P/R
• Adaptive microstepping and digital signal processing for smooth motion
• Encoder feedback loop ensures accurate load position detection at the mechanism level
• Automatic correction of position errors during operation
• No gain tuning required, even with low-rigidity loads
• Compatible with a full lineup of PKP Series 5-phase stepper motors

What Is Fully Closed-Loop Control?

Fully Closed-Loop Control is a term to describe a method to close the loop by installing an encoder at the mechanism instead of the motor.  By integrating an encoder at the load mechanism (ie: index table, ball screw...etc.) instead of on the rear shaft of the motor, the accuracy improves by eliminating backlash, pitch error, and thermal expansion of the interconnecting hardware.

How Does It Work?

Position information from a high-resolution encoder, such as a linear encoder, is connected to the driver.  During motor operation, the driver operates in open-loop mode, comparing the command pulse data with the detected pulse data from the encoder.  If the driver detects a difference that exceeds the accuracy threshold, then it switches into closed-loop mode and corrects the position at the end of the move.  After the correction is done, the driver switches back to open-loop operation.

By combining higher encoder resolution with microstepping, smaller errors can be detected and corrected, thus improving the stop position accuracy of the stepper motor.

How Does The Fully Closed-Loop Control Type Driver Compare To Open-Loop Systems?

The video compares the difference in stop position accuracy between a CVD Series open-loop driver and a CVD Series Fully Closed-Loop Control Type Driver.  By watching the encoder pulse meter, the demo with the Fully Closed-Loop Control Type Driver always arrives at its target perfectly, while the demo with the Open-Loop Type Driver is off by a few pulses to over a hundred pulses.  We used a pulse meter since this error is not visible to the naked eye.

Here are the measurement results.  The Fully Closed-Loop Control Type Driver shows much more consistency in repeated motion than an open-loop type driver.

※1 The motor is positioned from the CW and CCW directions to the target position, and the difference in rotation of the stop position at that time is the difference.

How Does The Fully Closed-Loop Control Type Driver Compare To Servo Systems?

• Lower cost and simpler integration
• No hunting or overshooting/undershooting at stop positions
• Ideal for applications where servo systems are overkill
  
  

Application Example

• Micron-Level Precision Without Servo Complexity: Oriental Motor’s CVD Fully Closed-Loop Control Type Driver delivers servo-like accuracy using stepper motors, eliminating the need for complex PID tuning or expensive servo systems.
• Fully Closed-Loop Control: By placing the encoder at the load instead of the motor, the system eliminates mechanical errors like backlash and thermal expansion, achieving superior positioning accuracy.
• High-Resolution Encoder Integration: Supports rotary encoders and linear encoders with resolutions up to 16.7 million P/R and 50 nm, enabling precise motion control in demanding applications like semiconductor and medical equipment.
• Superior Performance Over Open-Loop Systems: Automatically corrects position errors during operation, reduces vibration, and ensures consistent stop accuracy—outperforming traditional open-loop stepper systems by a mile.
• Ideal for Compact, High-Precision Automation: Offers easy integration, built-in diagnostics, and is well-suited for Industry 4.0 trends, such as smart factories and edge computing.

For automation engineers seeking a high-performance stepper driver that offers high-resolution encoder compatibility and network command capability, the CVD Series Fully Closed-Loop Control Type Driver offers a compelling alternative to servo systems.  By combining the simplicity of stepper motors with the precision of high-resolution encoder feedback and advanced microstepping features, this driver delivers ultra-low vibration, consistent performance, and high-resolution encoder compatibility for micron-level accuracy without the complexity of PID tuning.

Its ability to eliminate mechanical errors like backlash and thermal drift through mechanism-mounted encoders ensures that your systems operate with unmatched reliability and precision. Whether you're designing semiconductor tools, medical devices, or high-speed inspection systems, this driver empowers you to meet today’s tighter tolerances in a compact package.

Ready to elevate your motion control?  Explore how the CVD Series Fully Closed-Loop Control Type Driver can simplify your design, enhance performance, and future-proof your automation systems.

Discuss your current project with Oriental Motor's Technical Support Engineers for application-specific guidance and ask our Inside Sales Engineers for quotes or samples!