What Is an AC Servo Motor Controller
An AC servo motor controller is a motion control unit that calculates position, speed, and torque commands and sends them to servo drives through real-time industrial communication networks.
It consists of:
Motion control CPU (DSP / FPGA)
Encoder feedback acquisition interface (RS-422 / BiSS / EnDat)
Fieldbus communication module (EtherCAT / CANopen / PROFINET)
Motion interpolation engine
Digital I/O and safety logic unit
During operation, the controller receives motion instructions from a PLC, generates trajectory curves (linear, circular, or S-curve), and updates command values every 250–1000 μs. Encoder feedback is sampled continuously to correct position deviation in closed-loop control.
👉 In multi-axis CNC and packaging systems, controller timing deviation greater than 50–100 μs may cause axis mismatch or mechanical vibration.
Engineering Criteria for Selecting Servo Motor Controllers
Control Cycle Stability
Typical industrial systems require fixed-cycle execution at 250 μs or 500 μs. Cycle jitter affects axis synchronization in gantry and robotic systems.
Motion Interpolation Capability
Supports linear interpolation, circular interpolation, and jerk-limited S-curve motion. This reduces mechanical shock on ball screws and gear reducers.
Encoder Signal Processing
Supports incremental encoders (A/B/Z) and absolute encoders (17–23 bit resolution). Encoder resolution directly affects positioning granularity.
Multi-Axis Synchronization Method
EtherCAT distributed clock (DC mode) is commonly used for sub-millisecond axis synchronization.
Fieldbus Mapping Structure
Motion registers must map to PLC variables such as position command, velocity command, torque limit, and error feedback signals.
Top 5 AC Servo Motor Controller Manufacturers in China
The rankings are in no particular order.
Zhejiang Tonghang E-Drive Technology Co., Ltd.
Zhejiang Tonghang E-Drive Technology Co., Ltd. develops servo motion control systems integrating AC servo drives, servo motors, and controller-level coordination logic. The system is designed to reduce mismatches between motion controller output, servo drive execution, and motor response behavior.
System Architecture
DSP motion CPU for trajectory calculation
Encoder feedback module for real-time sampling
Industrial communication (EtherCAT / CANopen / Modbus)
PLC register mapping interface
Multi-axis synchronization logic
Control structure: position loop → speed loop → torque loop
01
Motion Execution Process
PLC sends motion command
Controller generates S-curve / linear trajectory
Fieldbus sends data to servo drives
Drive outputs current to motor
Encoder returns feedback signal
Controller updates every 250–500 μs
02
Pre-Shipment Matching
Motor current and torque curve setup
Encoder type (17–23 bit / multi-turn)
Drive current loop parameters
Brake resistor configuration
Communication mapping
Reduces onsite PID tuning and inertia adjustment.
03
Application Configuration
EtherCAT / CANopen topology
Axis number definition
Acceleration / jerk settings
Torque limit parameters
PLC register mapping
Enables direct system integration.
04
Applications
CNC gantry systems (inertia control)
Packaging synchronization lines
Automated transfer systems
Robotic motion systems
Typical cycle time: 250–500 μs
05
Beckhoff Automation (PC-based Motion Systems)
Beckhoff uses industrial PC architecture with TwinCAT motion control software. EtherCAT is used for distributed real-time control with synchronized cycle execution across multiple servo axes.
Siemens Digital Motion Control Systems
Siemens integrates PLC-based motion control with SINAMICS drive systems. Motion commands are executed through PROFINET and DRIVE-CLiQ communication for CNC and industrial automation systems.
Yaskawa Motion Control Systems
Yaskawa motion systems combine controller logic with Sigma servo drive coordination. Encoder feedback and torque compensation are used in high-speed robotic and pick-and-place systems.
Delta Motion Control Platforms
Delta integrates PLC, motion controller, and servo drive systems into a unified architecture. EtherCAT-based synchronization is used in packaging and electronics manufacturing equipment.
Engineering Comparison for Procurement Teams
Why Motion System Integration Determines Machine Performance
Servo motion accuracy depends on:
- Controller cycle stability (μs level)
- Encoder feedback delay
- Drive current loop response
- Mechanical inertia matching
👉 If communication delay exceeds mechanical response window, axis drift, vibration, or positioning error occurs in high-speed motion systems.
Motion Control System Configuration Request
To recommend a servo motor controller system, engineers evaluate the following parameters to ensure optimal pre-matching before integration.
- Number of axes
- Motor torque and inertia ratio
- Encoder type and resolution
- Communication protocol (EtherCAT / CANopen / PROFINET)
- Cycle time requirement (250–1000 μs)
- Machine load profile
FAQ
What key data is required before selecting a servo motor controller?
- Motor power, torque, and rated speed
- Load inertia ratio (motor vs. load)
- Encoder type (incremental / absolute / multi-turn)
- Number of axes in the system
- Communication protocol (EtherCAT / CANopen / PROFINET)
These parameters determine whether the controller can maintain stable closed-loop motion.
What happens if the controller is not compatible with the servo drive?
Typical issues include:
- Communication failure between controller and drive
- Encoder signal cannot be decoded
- Axis synchronization delay in multi-axis systems
- Unstable motion during acceleration
👉 Most problems appear during commissioning stage.
Why is multi-axis synchronization difficult?
Synchronization depends on control cycle timing.
If cycle delay exceeds about 500–1000 μs, it may cause:
- Position mismatch between axes
- Vibration during high-speed motion
- Gantry alignment errors
EtherCAT is commonly used to reduce timing deviation.
How does encoder type affect system performance?
- Incremental encoder: requires homing after power loss
- Absolute encoder: retains position data after shutdown
- Higher resolution (17–23 bit) improves positioning accuracy
Unsupported encoder types may prevent normal operation.
Why does commissioning time vary between suppliers?
Main reasons:
- Whether motor-drive-controller parameters are pre-set
- Whether communication mapping is pre-configured
- Whether PID tuning is required onsite
- Encoder calibration status
✔ Pre-configured systems reduce debugging time.
What should be sent to suppliers for quotation?
- Motor specifications (power, torque, speed)
- Load type and inertia
- Encoder details
- Axis count and motion requirement
- Communication protocol
- Accuracy requirement
These data help match controller and system configuration correctly.