Linear Actuators

MaxPulse Calculation

For linear actuators, the calculation for MaxPulse is slightly different from rotating actuators, but it follows a similar principle. It takes into account factors such as the encoder resolution (ppr), mechanical gear ratio, electrical gear ratio, and the leadscrew parameters.

Where:

• RIG.ppr: Encoder pulses per revolution

• RIG.mechanik_GearRatio_Servo: Mechanical gear ratio of the servo

• RIG.elektrik_GearRatio_Servo: Electrical gear ratio of the servo

• RIG.leadscrew_length: Total length of the leadscrew (in mm)

• RIG.lin_act_safety: Linear safety margin (in mm)

• RIG.leadscrew_pitch: Leadscrew pitch (in mm per revolution)

Example for Linear Actuators:

For instance, let’s calculate the MaxPulse for the following parameters:

• Encoder Resolution (ppr) = 10,000

• Mechanical Gear Ratio = 1:1

• Electrical Gear Ratio = 2

• Leadscrew Length = 100 mm

• Leadscrew Pitch = 5 mm

• Linear Safety = 5 mm

Using the formula:

Resolution of the Actuator

The resolution of the linear actuator can be calculated by dividing the distance moved per pulse:

In this case, for 90,000 positions per 100 mm, the resolution is:

So, each pulse will move the actuator by 0.0011 mm.

Calibrating and Adjusting the Actuator

• Calibration Offset (Cal. Offset): Similar to rotating actuators, the calibration offset for linear actuators is set for each actuator individually. This offset indicates how many pulses the actuator will move after homing to correct any mechanical inaccuracies, such as misalignments or errors at the hard stop or limit switch.

• Park Position: The Park Position is used to define the position where all actuators should return after calibration. This position is represented in pulses and ensures that all actuators return to a uniform position, reducing the risk of misalignment. The calculation for the park position is similar to the calibration offset, with adjustments made based on the actuator’s travel range.

• Standby Position: The Standby Position for linear actuators is also calculated as half of the actuator's range in pulses, just like rotating actuators. For example, if an actuator has a range of 100 mm and a MaxPulse of 90,000 positions per 100 mm, the standby position would be:

Custom Standby Position Adjustment

The Standby Position can be adjusted as a percentage in the Setup Menu. Instead of always using the mid-range value (50%), you can define a specific standby position based on your needs.

For example:

• 50% → Mid-range position

• 25% → Lower quarter of the range

• 75% → Upper quarter of the range

This flexibility allows for better alignment with your motion platform configuration and startup preferences.

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Summary

For linear actuators, the MaxPulse value depends on the encoder resolution, the mechanical gear ratio, the electrical gear ratio, and the leadscrew parameters. The actuator’s resolution is calculated from these factors, and the calibration and park positions are used to ensure uniformity and accuracy across all actuators. The standby position is set at half the actuator's range to ensure the system is ready for motion.