Table of Contents

Why Do Servo Motors Need Homing After Power-Up?

In many automated machines, axes move toward a fixed reference point before production begins. This process, known as homing or return-to-zero, is a fundamental step in industrial motion control.

Many engineers new to automation often ask:

“Servo motors are precise — why can’t they just remember their position after power loss?”

The answer lies in how servo systems detect and maintain positional information.

What Happens to Servo Position When Power Is Lost?

Servo motors rely on feedback devices called encoders to determine their position. When power is interrupted, the control system may lose its position reference depending on the type of encoder used.

Servo Motors Do Not Store Position Themselves

The motor only executes movement. Position tracking happens in the encoder and controller. If the system loses reference data, the motor cannot determine where it stopped.

Loss of Coordinate Reference After Restart

After power-up, the drive can move, but without a known zero point, the system cannot safely calculate target positions. This creates the risk of positioning errors or mechanical crashes.

Incremental Encoders Require a Known Starting Point

Most industrial servo systems use incremental encoders, which measure movement relative to a reference rather than storing absolute coordinates.

How Incremental Encoders Work

They generate pulses as the motor rotates. The controller counts these pulses to calculate motion distance and speed.

Why Homing Is Necessary

Because incremental encoders lose position data during power loss, the system must move to a physical reference point to re-establish the machine coordinate system.

Homing Also Improves Mechanical Accuracy

Homing is not only about defining zero — it also corrects accumulated mechanical deviation.

Mechanical Wear and Backlash

Belts stretch, couplings loosen, and gears develop backlash over time. These factors cause small differences between calculated and actual positions.

Physical Reference as Calibration

Returning to a fixed sensor or limit switch allows the system to realign theoretical coordinates with the true mechanical position.

Absolute Encoders Reduce the Need for Homing

Some advanced servo systems use absolute encoders that retain position data even after power loss.

Advantages of Absolute Encoder Systems

They allow faster startup and eliminate homing sequences, which is useful in high-speed or continuous production environments.

Cost and Application Considerations

Absolute encoder systems are typically more expensive, so incremental systems with homing remain common in cost-sensitive automation equipment.

Homing as Part of Motion System Initialization

In PLC-based automation systems, homing is part of a broader startup routine.

Clearing Previous Fault Conditions

Drives reset alarms and motion errors before operation begins.

Loading Motion Parameters

Speed, acceleration, and positioning settings are reloaded to ensure consistent performance.

Enabling Coordinated Axis Control

Once reference positions are confirmed, multiple axes can operate together accurately.

Reliable Servo Solutions for Industrial Automation

Whether your system uses incremental encoders with homing routines or advanced absolute encoder technology, selecting the right servo platform is key to machine reliability and precision.

We supply a broad range of industrial motion control products, including servo motors and drives from Siemens Servo and Allen-Bradley Servo, suitable for packaging machines, CNC systems, production lines, and factory automation upgrades.

If you’re planning a new automation project or upgrading an existing system, our team can help you choose the right servo components for performance, stability, and cost efficiency.