Dual-Actuator Open-Loop Drift and Skew Calculator
Estimate position separation and platform skew between two open-loop actuators from initial offset, measured speed mismatch, correction interval, and actuator spacing. The result is a preliminary engineering estimate, not a product rating or safety approval.
Calculate open-loop drift and skew
Enter the measured or assumed inputs in one unit system. The calculator converts to SI internally, evaluates the stated model, and displays the result in the selected unit system.
Engineering visualizer
Schematic, not to scale. The drawing updates from the production calculation engine and labels the main outputs.
Calculator by FIRGELLI Automations.
Embed this calculator
When embedded on another page, the calculator shows only the working tool. FIRGELLI attribution, the visualizer, and the calculation-error report remain available.
What the separation and skew numbers mean
Left speed minus right speed, times the time you wait before anyone corrects, plus the offset you started with, is how far the two pins have walked apart. Skew is that separation over the distance between the axes. It is open-loop geometry. Two motors on one switch will do this. Matched SKUs do not cancel it.
A few millimeters of split on a short hatch is a bind. The same split on a long lid is a twist you can see. This page does not model a Hall controller or a sync box. If the skew is already ugly in a few seconds, you need feedback and a correction loop, not a hope that the next pair will run closer. Fix the speed mismatch or stop running them open-loop.
What This Calculator Calculates
What does dual-actuator open-loop drift and skew mean? This quantity describes one specific part of the actuator design problem. It should be read as a model output, not as a complete product selection rule.
How To Interpret The Results
How should I interpret the dual-actuator open-loop drift and skew result? A larger result means the checked effect is becoming more important and should be compared with product data, mounting limits, or the next design check. A smaller result does not prove the whole system is safe.
When Not To Use This Calculator
When should I not use the dual-actuator open-loop drift and skew model? Do not use this model when the inputs are unknown, the mechanism is outside the stated boundary, or the decision depends on manufacturer ratings, fatigue, shock, compliance, or regulated safety approval.
Engineering model and calculation details
Estimate position separation and platform skew between two open-loop actuators from initial offset, measured speed mismatch, correction interval, and actuator spacing.
The page separates the calculator result from product selection. It explains the inputs, limitations, interpretation, and next design checks so the result is not mistaken for a complete actuator rating.
Governing equations
| Quantity | Equation | Model meaning |
|---|---|---|
| Signed speed difference | Delta v = v_right - v_left |
Calculates signed speed difference for the stated simplified model. |
| Estimated end-of-interval position separation | Delta x = x_0 + Delta v t |
Calculates estimated end-of-interval position separation for the stated simplified model. |
| Estimated platform skew angle | phi = atan(Delta x / s) |
Calculates estimated platform skew angle for the stated simplified model. |
Variables and canonical units
| Symbol | Variable | SI unit | Domain |
|---|---|---|---|
left_speed |
Left actuator speed | m_s | finite engineering value in the documented model domain |
right_speed |
Right actuator speed | m_s | finite engineering value in the documented model domain |
correction_time |
Open-loop time between corrections | s | finite engineering value in the documented model domain |
initial_offset |
Initial position offset | m | finite engineering value in the documented model domain |
axis_spacing |
Distance between actuator axes | m | finite engineering value in the documented model domain |
speed_difference |
Signed speed difference | m_s | finite result from valid inputs |
position_separation |
Estimated end-of-interval position separation | m | finite result from valid inputs |
skew_angle |
Estimated platform skew angle | rad | finite result from valid inputs |
Assumptions and boundary conditions
- Inputs represent one consistent operating condition.
- The model uses the simplified boundary stated on the page.
- The model begins and ends at the user-defined actuator or mechanism boundary.
Limitations and omitted checks
- The result depends on user-entered values and simplified boundary conditions.
- The model does not replace FIRGELLI product data, installation review, endurance testing, or a qualified engineering review.
- Shock, fatigue, misalignment, mounting strength, and controller behavior may govern before the calculated value.
Worked example
12 mm/s and 11.4 mm/s, 8 s no correction, 600 mm between pins. Δv = 0.6 mm/s, Δx = 4.8 mm, skew ≈ 0.46°. That binds a hatch. Feedback or it racks.
Related checks: FCB-2 controller, Hall Super Duty actuators, FCB-2 controller guide.
What this model evaluates
| Mode or effect | Status | Disclosure |
|---|---|---|
| calculated quantity | evaluated | The named output is evaluated for the stated model. |
| manufacturer rating | not evaluated | The result is not a manufacturer product rating. |
| installation detail | not evaluated | Mounting, alignment, shock, fatigue, and environment require separate review. |
Common mistakes
- Treating a simplified estimate as a manufacturer rating.
- Mixing units or entering values measured at a different operating point.
- Ignoring mounting, alignment, shock, duty cycle, or controller limitations.
- Failing to compare the result with the next logical FIRGELLI design check.
Engineering references
- OpenStax. University Physics Volume 1 - Motion Along a Straight Line. Rice University, 2016. Supports: Position change from speed and time used for drift accumulation.. Accessed 2026-07-28. Source.
- National Institute of Standards and Technology. NIST Guide to the SI. National Institute of Standards and Technology, Accessed 2026. Supports: SI unit definitions and unit-consistent engineering calculation display.. Accessed 2026-07-28. Source.
- Barry N. Taylor and Chris E. Kuyatt. Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results. National Institute of Standards and Technology, NIST Technical Note 1297. Supports: Root-sum-square treatment of independent standard uncertainty components.. Accessed 2026-07-28. Source.
Author, validation, and review status
Author: Robbie Dickson
Author profile: Robbie Dickson prepares FIRGELLI actuator education and calculator content for product users and engineering teams.
Engineering model type: Two-axis constant-speed open-loop drift estimate
Validation: The production JavaScript engine is compared with a separately written Python oracle across known-answer, SI/imperial-equivalent, boundary, invalid-input, and randomized cases.
Questions about this calculator or found an error? Message our engineering team.
