How to Achieve Synchronized Motion Using Firgelli Linear Actuators

Synchronized motion control is one of the most critical challenges in multi-actuator automation systems. Whether you're building a custom truck bed cover, designing a hidden trapdoor mechanism, or engineering a precision lift system, achieving perfectly synchronized movement between two or more linear actuators can mean the difference between reliable operation and catastrophic failure.

At FIRGELLI Automations, we regularly field questions from customers who have connected multiple actuators to the same power supply, expecting them to move in perfect unison, only to discover that one actuator consistently outpaces the other. In some cases, this speed mismatch has led to bent hatches, broken mechanisms, or burnt-out motors. The good news is that this isn't a defect—it's a fundamental characteristic of DC motor behavior that can be overcome with the right approach.

This comprehensive guide explains why actuators drift out of sync, presents proven solutions for achieving true synchronized motion, and provides practical methods for applications where near-synchronous movement is sufficient. Whether you're an experienced automation engineer or a first-time builder, understanding these principles will help you design more reliable multi-actuator systems.

Why Actuators Don't Naturally Synchronize

Many customers assume that connecting two identical actuators to the same voltage source will result in identical movement. This assumption seems logical—after all, if both motors receive the same electrical input, shouldn't they produce the same mechanical output?

Unfortunately, the reality is more complex. Even when manufactured to tight tolerances and powered identically, two DC motors will never maintain perfect synchronization without active feedback control. This is true regardless of manufacturer or price point—it's an inherent property of DC motor physics.

Manufacturing Tolerances and Component Variation

No manufacturing process produces perfectly identical components. Even with modern precision machining, microscopic variations exist in every motor produced. The magnetic field strength in the permanent magnets can vary by a few percentage points. The armature winding resistance might differ by fractions of an ohm. The air gap between rotor and stator might vary by micrometers. Individually, these variations are negligible, but collectively they affect motor performance.

These manufacturing tolerances apply not just to the motor itself but to every component in the actuator assembly. The lead screw pitch might vary slightly. Bushing dimensions differ minutely. Even the internal lubrication distribution can affect performance. While quality control ensures these variations stay within acceptable ranges, they still cause measurable differences in speed under identical electrical conditions.

Load Distribution and Mechanical Factors

In real-world applications, achieving perfectly balanced loads across multiple actuators is nearly impossible. Consider a truck bed cover lifted by two actuators—unless the cover's center of gravity is exactly centered and the mounting points are perfectly symmetrical, one actuator will bear more load than the other. Even a difference of a few pounds creates unequal torque demands on the motors.

Friction forces also vary between installations. One actuator might be mounted at a slightly different angle, changing the bearing loads. Temperature differences across the installation can affect lubrication viscosity. Dust, moisture, or debris might affect one actuator more than another. All these factors contribute to different operating speeds even with identical electrical inputs.

Realistic Speed Variation Expectations

Under typical operating conditions, expect a 5-10% speed difference between unsynchronized DC motors or linear actuators. This means that over a 12-inch stroke, one actuator might extend fully while the other is still 0.6 to 1.2 inches short of full extension. For many applications—particularly those with rigid coupling between actuators—this difference is unacceptable and can cause mechanical binding, premature wear, or complete system failure.

True Synchronization Methods with Feedback Control

Achieving true synchronized motion requires closed-loop feedback control—a system that continuously monitors actuator position and adjusts motor speed to maintain alignment. This approach eliminates drift and ensures actuators move together regardless of load variations or manufacturing tolerances. If you're in the planning stages of your project, these methods offer the most reliable path to synchronized motion.

FA-SYNC Control Boxes: The Professional Solution

The FA-SYNC-2 and FA-SYNC-4 control boxes represent the most reliable and user-friendly approach to synchronizing feedback actuators. These dedicated controllers handle all the complex signal processing and motor control algorithms internally, providing a true plug-and-play solution for two or four actuators respectively.

These control boxes work with any FIRGELLI actuator that includes position feedback, such as:

• Optical feedback series actuators (200 lb and 400 lb force ratings)
• Bullet actuators (36 Cal and 50 Cal series with Hall Effect sensors)
• Feedback rod actuators with potentiometric position sensing

The FA-SYNC system uses sophisticated control algorithms to continuously compare actuator positions and adjust individual motor speeds to maintain synchronization. When one actuator begins to drift ahead, the controller automatically reduces its speed while increasing the speed of the lagging actuator. This active correction happens hundreds of times per second, maintaining position accuracy within a fraction of an inch throughout the entire stroke.

Setup is straightforward: connect your actuators to the control box, wire the power supply, and press the auto-calibration button. The system learns the stroke length and feedback characteristics of your specific actuators, then enables immediate synchronized control via simple up/down buttons or external switch inputs. The auto-calibration feature is particularly valuable because it adapts to your specific installation, compensating for variations in stroke length, mounting configuration, and load distribution.

Arduino-Based Synchronization for Advanced Users

For engineers and experienced makers who need custom control logic or want to integrate actuator control into a larger automation system, Arduino-based solutions offer maximum flexibility. This approach requires significant programming knowledge and system integration skills, but enables sophisticated control strategies tailored to specific application requirements.

Interrupt-Based Control for Optical and Hall Effect Sensors: Actuators with optical or Hall Effect encoders output pulse signals as they move. By connecting these signals to Arduino interrupt pins, you can count pulses with high accuracy and calculate real-time position. The interrupt-driven approach ensures no pulses are missed even when the processor is executing other code, providing reliable position tracking.

Your control algorithm must continuously compare pulse counts from multiple actuators and adjust individual motor speeds through PWM (pulse width modulation) signals sent to motor drivers. The implementation requires careful attention to signal noise filtering, timing precision, and control loop stability. This is an advanced project requiring strong embedded programming skills and understanding of PID control theory.

Analog Position Feedback for Potentiometric Actuators: Feedback actuators with built-in potentiometers provide analog voltage output proportional to rod position. These signals connect to Arduino analog input pins, where the microcontroller's ADC (analog-to-digital converter) samples the voltage and converts it to a position reading.

While reading the analog voltage is relatively straightforward, implementing effective synchronized control is challenging. Your code must continuously read positions from all actuators, calculate position errors, and implement control algorithms that maintain synchronization without causing oscillation or instability. Factors like sensor noise, ADC resolution, and control loop timing all affect performance.

We provide these options for experienced users who understand the technical challenges involved. FIRGELLI does not offer programming support or troubleshooting assistance for custom Arduino implementations—this path is recommended only for users with existing embedded systems experience.

Near-Synchronous Operation Without Feedback

If you've already purchased actuators without built-in position feedback, or if your application can tolerate small position variations, several approaches can minimize (though not eliminate) speed differences between actuators. These methods won't achieve the precision of closed-loop feedback control, but they can reduce the natural 5-10% speed variation to acceptable levels for many applications.

Mechanical Compliance: The Simplest Solution

Sometimes the best engineering solution is to design the mechanical system to accommodate natural variations rather than fighting them. This approach is particularly effective for short-stroke applications (under 6 inches) where absolute position differences remain small even with percentage-based speed variations.

Consider incorporating flexible elements into your design. For a lift platform, use hinged connections rather than rigid mounts, allowing slight angular misalignment without binding. For a hatch mechanism, employ torsion-compliant mounting that lets the structure twist slightly to absorb position differences. For sliding panels, include spring-loaded guides that maintain alignment while accommodating small variations in actuator position.

This mechanical approach often proves more reliable and cost-effective than complex electronic solutions, particularly for DIY projects and applications where precision synchronization isn't critical. It's the engineering principle of "designing for reality" rather than assuming perfect conditions.

Speed Control Through PWM Adjustment

If testing reveals that one actuator consistently moves faster than others, you can reduce its speed using pulse width modulation control. This approach doesn't create true synchronization, but it can narrow the speed gap from 10% down to 2-3% through careful tuning.

FIRGELLI offers dedicated speed controller modules that allow precise speed adjustment through a simple rotary dial. These controllers use PWM to reduce the effective voltage delivered to the motor, slowing its operation without losing torque. The adjustment is continuous, allowing fine-tuning to match actuator speeds as closely as possible.

The tuning process requires patience and iterative testing. Run your system, observe which actuator moves faster, apply speed reduction to that actuator, and test again. Repeat until speeds are matched as closely as possible. Note that this matching is specific to your installation—changing loads, temperatures, or wear patterns may require retuning over time.

For multi-actuator systems, you may need individual speed controllers for each actuator, adjusting each until all move at approximately the same rate. This manual tuning approach is time-intensive but can yield acceptable results for applications where the mechanical system has some compliance and exact position matching isn't critical.

Arduino PWM Control for Custom Implementations

Experienced Arduino users can implement custom speed control using motor drivers and PWM output pins. This approach provides more flexibility than off-the-shelf speed controllers, allowing programmatic speed adjustment and integration with other control logic.

The implementation requires motor driver modules (H-bridges) capable of handling your actuator's current requirements, proper power supply design, and code that generates stable PWM signals. You can implement simple fixed-speed control or more sophisticated algorithms that attempt to estimate position based on elapsed time (though without feedback, this remains inherently imprecise).

As with the interrupt-based synchronization approach, FIRGELLI does not provide programming support for custom Arduino implementations. This path is suitable only for users with existing Arduino experience and understanding of motor control principles.

Selecting the Right Approach for Your Application

Choosing the optimal synchronization method depends on your specific application requirements, budget, technical skills, and precision needs. Understanding these factors helps you make informed decisions that balance performance, cost, and implementation complexity.

When True Synchronization Is Essential

Certain applications demand precise synchronized motion with minimal position variation. These include:

• Heavy lift systems where binding could damage mechanisms or cause safety hazards
• Precision positioning systems where accumulated position errors are unacceptable
• High-cycle applications where even small variations compound over thousands of operations
• Professional installations where reliability and warranty considerations are paramount
• Systems lifting expensive or fragile loads where any mechanical stress must be minimized

For these applications, invest in feedback actuators and the FA-SYNC control system from the project's inception. The additional cost is modest compared to the risk of system failure, and the plug-and-play implementation saves countless hours compared to custom solutions.

When Near-Synchronization Is Sufficient

Many applications can tolerate small position variations, particularly when mechanical compliance is incorporated into the design:

• Short-stroke applications (under 6 inches) where absolute position errors remain minimal
• Low-cycle hobby projects where wear-related drift develops slowly
• Systems with inherent mechanical flexibility that absorbs position differences
• Budget-constrained projects where component costs must be minimized
• Prototype development where testing simple approaches before investing in precision systems makes sense

For these applications, starting with mechanical compliance design and manual speed tuning often provides adequate performance. You can always upgrade to feedback-based synchronization later if testing reveals the need.

Technical Skill Considerations

Honestly assess your technical capabilities when selecting a synchronization approach. The FA-SYNC controllers require only basic wiring skills and are designed for immediate operation. Arduino-based solutions demand substantial programming knowledge, debugging skills, and patience for iterative development. Starting with off-the-shelf solutions and upgrading to custom implementations once you've mastered the basics often proves more efficient than attempting complex custom development immediately.

Implementation Best Practices

Regardless of which synchronization method you choose, following established best practices improves reliability and performance.

Electrical System Design

Use a properly-rated power supply with adequate current capacity for all actuators operating simultaneously. Undersized power supplies cause voltage sag under load, leading to erratic motor behavior and inconsistent speeds. Calculate total current draw by adding the rated current of all actuators plus a 20% safety margin.

Implement proper wiring practices with appropriate gauge wire for the current and distance involved. Voltage drop in undersized wiring creates different effective voltages at each actuator, contributing to speed variations. For multi-actuator systems, consider star-topology power distribution where each actuator connects directly to the power source rather than daisy-chaining connections.

Mechanical Installation Guidelines

Ensure proper alignment of all actuators. Misalignment creates side-loading on the rod and internal components, increasing friction and causing uneven wear. Use quality mounting brackets and verify alignment with precision measuring tools before finalizing installation.

Balance loads as evenly as possible across multiple actuators. For lift applications, position actuators symmetrically relative to the load's center of gravity. For sliding applications, minimize binding by ensuring rails and guides are properly aligned and lubricated.

Testing and Commissioning

Test your system thoroughly before relying on it for regular operation. Run multiple complete cycles, monitoring for any signs of binding, unusual noise, or uneven movement. For feedback-based systems, verify that the auto-calibration process completes successfully and that synchronization is maintained throughout the full stroke under varying load conditions.

Document your installation settings, particularly if using speed controllers that require manual adjustment. Taking photos of controller settings and wiring configurations helps with future troubleshooting and maintenance.

Conclusion

Synchronized motion control represents a fundamental challenge in multi-actuator automation, but it's a challenge with well-established solutions. Understanding why actuators naturally drift out of sync—and more importantly, knowing which solutions match your specific requirements—enables you to design reliable systems that perform consistently over thousands of cycles.

For applications demanding precision, feedback actuators paired with FA-SYNC control boxes provide professional-grade synchronization with minimal setup complexity. For less demanding applications, mechanical compliance and manual speed tuning often deliver acceptable performance at lower cost. The key is matching the solution to your actual requirements rather than over-engineering simple applications or under-engineering critical ones.

Whether you're automating a custom vehicle modification, building specialized industrial equipment, or developing a unique mechanism, the principles and methods outlined in this guide provide a roadmap to successful synchronized motion control.

Frequently Asked Questions

Why won't two identical actuators move at the same speed when connected to the same power supply?

Even identical actuators contain small manufacturing variations in motor magnets, winding resistance, bearing friction, and dozens of other components. These microscopic differences compound to create measurable speed variations of 5-10%. Additionally, no installation perfectly balances loads, friction, and alignment between multiple actuators. Without feedback control actively correcting these differences, DC motors will never maintain perfect synchronization. This is an inherent characteristic of DC motor physics, not a defect—it affects all manufacturers' products equally.

What happens if I run unsynchronized actuators in a rigid system without compensation?

Operating unsynchronized actuators in a rigidly-coupled system creates mechanical binding as faster actuators pull ahead of slower ones. This binding dramatically increases stress on motors, mechanisms, and structural components. In the best case, this causes premature wear and shortened component life. In worse cases, it leads to bent shafts, stripped gears, burnt-out motors, or broken structures. For any rigid multi-actuator system, either implement true feedback-based synchronization or design mechanical compliance into the structure to absorb position differences.

Can I achieve perfect synchronization with actuators I already own that lack position feedback?

No. Perfect synchronization requires closed-loop feedback control, which is impossible without position sensors. However, you can minimize speed variations through careful speed controller adjustment and mechanical design that accommodates remaining differences. For short-stroke applications with built-in mechanical compliance, this approach often proves adequate. If your application demands true synchronization, you'll need to upgrade to feedback actuators and appropriate control electronics.

How much position error should I expect with different synchronization methods?

Unsynchronized actuators typically exhibit 5-10% speed differences, translating to 0.6-1.2 inches of position error over a 12-inch stroke. Manual speed tuning can reduce this to 2-3% (0.25-0.36 inches over 12 inches) with careful adjustment. Feedback-based synchronization with FA-SYNC controllers maintains position accuracy within a fraction of an inch regardless of stroke length, load variations, or operating conditions. The performance difference between open-loop speed matching and closed-loop feedback control is dramatic—choose based on your application's precision requirements.

Which FIRGELLI actuators work with the FA-SYNC synchronization controllers?

The FA-SYNC-2 and FA-SYNC-4 controllers work with any FIRGELLI actuator that includes position feedback sensors. This includes the Optical Series actuators (200 lb and 400 lb force ratings with optical encoders), Bullet actuators (36 Cal and 50 Cal series with Hall Effect sensors), and feedback rod actuators with potentiometric position sensing. The controllers cannot synchronize actuators without feedback sensors, such as the Classic or Premium series. When planning a synchronized system, select actuators with built-in feedback from the beginning—retrofitting feedback to non-feedback actuators isn't practical.

Is Arduino-based synchronization worth the effort compared to using an FA-SYNC controller?

For most users, the FA-SYNC controllers provide superior value. They're pre-programmed, pre-tested, and ready to use immediately with simple wiring. The auto-calibration feature eliminates complex setup procedures. Arduino-based solutions make sense only if you need custom control logic integration, have existing Arduino expertise, and understand that you're taking responsibility for all programming, debugging, and troubleshooting. Development time for a reliable Arduino synchronization system typically exceeds 20-40 hours even for experienced programmers—far more than the cost difference between solutions. Choose Arduino implementation only when the FA-SYNC controllers' functionality genuinely doesn't meet your requirements.