How to Achieve Servo Motor Synchronization in Multi-Axis Robotic Systems: Introduction and Technical Analysis

At the heart of industrial automation, multi-axis robotic systems are an indispensable part of today’s manufacturing processes. These systems deliver performance that surpasses human capabilities in tasks requiring high speed, repeatability, and precision. However, one of the most critical elements underlying this superior performance is the ability of each servo motor in the system to operate in perfect synchronization. It is not enough for each axis to move independently; in applications that follow complex trajectories, perform precise assembly, or where multiple motors share a common load, it is vital that the instantaneous position, speed, and even torque information of all motors are in harmony. Synchronization ensures that every link in the kinematic chain, which allows a robot to reach a specific point in space or follow a particular path, moves at the right time and by the right amount. This technical article and field guide will provide an in-depth analysis of servo motor synchronization in multi-axis robotic systems for industrial automation professionals, offering a wide range of information from fundamental principles to advanced techniques, common problems to practical solutions. Our goal is to explain this complex yet critical topic in an understandable language to help field engineers and system integrators overcome the challenges they face. Correct synchronization not only enhances system performance but also increases energy efficiency, reduces mechanical wear, and ensures consistency in production quality.

How to Achieve Servo Motor Synchronization in Multi-Axis Robotic Systems: Operating Principle and Technical Data

How to Achieve Servo Motor Synchronization in Multi-Axis Robotic Systems: Field Considerations

• Mechanical Assembly and Alignment: During the assembly of servo motors and mechanical transmission elements (gearboxes, belts, ball screws), utmost care must be taken to ensure zero backlash. Misalignment between axes can lead to vibrations, excessive loading, and synchronization deviations. All connections must be tight and made with correct torque values, and couplings should be selected for flexibility and vibration damping. The overall rigidity of the mechanical structure is critically important for maintaining synchronization, especially in high-dynamic movements.
• Cable Quality and Shielding: The quality of power and feedback cables for servo motors, as well as communication cables, directly impacts synchronization. Electromagnetic interference (EMI) in industrial environments can disrupt signal integrity, causing errors in position and speed feedback data. Therefore, high-quality, double-shielded (braid and foil) cables should be used and kept separate from power cables in cable trays to minimize crosstalk. Grounding and shielding must be performed completely according to manufacturer recommendations.
• Correct Motor and Driver Selection: Selecting the appropriate servo motor and driver combination for the system’s required load, speed, acceleration, and inertia values forms the foundation of synchronization. Inertia mismatch, especially when the ratio between motor inertia and load inertia is significantly different, leads to control difficulties and synchronization errors. Generally, an inertia ratio between 1:1 and 1:10 is acceptable, but for precise applications, this ratio should be kept between 1:1 and 1:3. The driver’s bandwidth and processing power must be sufficient for fast response times and tight control.
• Controller Settings and Optimization (PID Tuning): The PID gains (P, I, D), filter settings, and feedforward parameters of servo drives and the motion controller directly affect the system’s dynamic response and synchronization performance. Incorrectly set PID gains can lead to excessive oscillation, slow response, or instability. Automatic tuning functions can be a starting point, but manual fine-tuning by an experienced engineer is often necessary for optimal synchronization. If necessary, resonance filters and notch filters should be used to suppress the system’s natural frequencies.
• Power Quality and Grounding: The stability and quality of the mains voltage supplying robotic systems are important. Voltage fluctuations, sudden drops, or harmonics can adversely affect the performance of servo drives and cause temporary synchronization losses. In industrial environments, a correct and effective grounding scheme reduces electrical noise, increasing system stability. All equipment should be connected to a common grounding point, and the grounding resistance should be low.
• Environmental Conditions: The temperature, humidity, and vibration levels of the operating environment affect the lifespan and performance of electronic components and mechanical parts. Extreme temperatures shorten the life of electronics, while high humidity can cause short circuits. Excessive vibration can lead to mechanical loosening and errors in sensor readings, disrupting synchronization. Therefore, it must be ensured that the equipment operates within specified environmental conditions, and measures such as air conditioning or vibration isolation should be taken if necessary.
• Software and Firmware Updates: The software for motion controllers, servo drives, and even robot operating systems sometimes receives updates containing performance improvements, bug fixes, and new features. Regularly tracking these updates and applying them to the system after appropriate testing can improve synchronization performance and close known security vulnerabilities. However, backing up before each update and checking compatibility are of great importance.

How to Achieve Servo Motor Synchronization in Multi-Axis Robotic Systems: Common Problems and Solutions

Servo motor synchronization in multi-axis robotic systems is a complex topic, and many different problems can be encountered in the field. These problems are usually mechanical, electrical, or software-related, and accurate diagnosis is critical for a quick and effective solution.

• Synchronization Loss or Deviation:

  Problem: The robot fails to follow the expected trajectory, with a noticeable delay or drift between axes, especially evident in high-speed or high-acceleration movements. Dimensional errors or degradation in surface quality may be observed in manufactured parts.

  Solution: First, mechanical backlash (gearbox, coupling, bearings) should be checked. If backlash exists, it should be eliminated or replaced with zero-backlash transmission elements. The PID gains and feedforward parameters of the servo drives should be re-tuned; often, insufficient P gain or excessively high D gain can lead to this situation. Cycle times and jitter values of the communication protocol (EtherCAT, PROFINET IRT) should be checked, and cable connections should be inspected for looseness or damage. If the problem persists, encoder feedback should be checked, and the encoder’s integrity and signal quality tested.

• Vibration and Noise:

  Problem: The robot exhibits abnormal vibrations while moving or at rest, or loud noises are heard from the motors or mechanical components. This condition accelerates mechanical wear over time and reduces precision.

  Solution: Vibrations typically result from inertia mismatch, high PID gains, or mechanical resonances. The ratio between motor and load inertia should be checked, and if necessary, the gearbox ratio should be changed to improve inertia matching. PID gains can be reduced to ensure a smoother system response. If mechanical resonances are present, notch filters in the servo drives or motion controller should be used to suppress resonance frequencies. Loose mechanical assembly should be checked, ensuring all fasteners are tight. Wiring and grounding issues can also cause electrical noise and vibration.

• Error Codes (Over-current, Over-voltage, Communication Error):

  Problem: Warning or error codes such as over-current, over-voltage, or communication errors appear on servo drives or the motion controller. This usually causes the system to shut down completely or operate unstably.

  Solution: Over-current errors can result from incorrect motor or load sizing, mechanical jams, or overloading of the drive. The motor’s nominal and instantaneous current values should be checked, and mechanical obstructions removed. Over-voltage errors are often related to energy feedback during regenerative braking; ensure the braking resistor is correctly sized or the DC bus voltage is controlled. Communication errors can be caused by cable damage, connector failure, incorrect IP address or protocol settings, or electromagnetic interference. The physical condition of the cables, the integrity of the connectors, and network settings should be carefully checked. In all these situations, consulting the manufacturer’s error code guide will provide the most accurate solution.

• Insufficient Precision or Repeatability:

  Problem: The robot produces different results each time it repeats the same task or fails to reach the target position with the desired precision. This directly affects production quality.

  Solution: Such problems typically stem from low encoder resolution, mechanical flexibility, expansion/contraction due to temperature changes, or poor controller resolution. Switching to higher-resolution encoders can improve precision. The rigidity of the mechanical structure should be reviewed, and elements causing flexibility should be strengthened or replaced. Systems with temperature compensation features can be used. Additionally, the accuracy of interpolation algorithms and position control loops within the controller should be examined. If necessary, the system should be recalibrated, and the kinematic model updated.

How to Achieve Servo Motor Synchronization in Multi-Axis Robotic Systems: Conclusion and Expert Advice

Servo motor synchronization in multi-axis robotic systems is one of the fundamental pillars of modern industrial automation and has a direct, decisive impact on the system’s overall performance, production quality, and efficiency. As we have seen, this is a complex engineering discipline, closely related not only to the correct selection and adjustment of electrical and electronic components but also to the quality of mechanical design and the effectiveness of software control algorithms. Successful synchronization requires many different components to work in harmony, from real-time communication protocols operating with microsecond-level precision, to high-resolution feedback systems, rigid mechanical structures, and optimally tuned PID controllers.

Our field experience shows that synchronization problems often arise not from a single cause but from a combination of multiple factors. Therefore, when a problem is encountered, adopting a holistic approach is essential. A wide range of investigations, from checking mechanical backlash to researching sources of electrical noise, optimizing controller parameters, and following software updates, is critical to finding the root cause of the problem. It should be remembered that even the most advanced electronic system cannot deliver desired performance with a weak mechanical design or inadequate cabling.

As expert advice, we would like to recommend the following to industrial automation professionals: First, ensure that all system components (motors, drives, controller, mechanical transmission) are correctly sized according to application requirements. Second, during the installation phase, pay meticulous attention to mechanical assembly and electrical connections (especially grounding and shielding) according to manufacturer standards and best practice methods. Third, when the system is commissioned, use automatic tuning tools to make initial adjustments, but ensure that manual fine-tuning and performance tests are carried out by an experienced engineer for final optimization. Fourth, regularly check for mechanical wear, cable integrity, and environmental conditions during periodic maintenance routines. Finally, continuous education and keeping up with current technologies, especially with the development of AI and machine learning-supported predictive maintenance and adaptive control algorithms, will be key to further advancing synchronization performance in the future. By adhering to these principles, you can achieve maximum precision, reliability, and efficiency in your multi-axis robotic systems.