Auto Calibration & Servo Insertion
Auto Calibration & Servo Insertion for XM2 Labs SLG-20 Retractable Landing Gear
Introduction
SLG-20 units are delivered fully calibrated and ready to operate, however there are scenarios where the user may need to perform the calibration process. If the servo motor needs to be replaced or refitted, the calibration process will need to be implemented. Each time the firmware is updated on the control board, this action resets the parameters and calibration is required by the SLG-20 user.
Alternative Servo Warning
Each SLG-20 factory servo has been individually preprogrammed by XM2 Labs for enhanced parameters and movement range. We strongly advise against replacing the servo motor with third-party variants. Third-party servos have not been programmed for use with the SLG-20 and this will result in limited functionally and a potential safety risk. Spare SLG-20 Servos are available for purchase. If the user has a technical issue, please contact XM2 Labs directly for support and servicing.
Calibration Procedure
The calibration process is in two states:
Insert State: The servo it set to a central position for alignment with the mechanism.
Calibration State: To calibrate the trim parameter, the servo moves DOWN until it finds the mechanical endstop of the mechanism. When the endstop is successfully found, the parameters are saved.
The calibration procedure is performed using the console interface. For details on how to connect to the console interface, see here.
If your servos are already inserted into the mechanism in the right position (this will be the case if the servos have never been removed since the purchase) then you do not need to remove them. You can refer to the instructions for calibration without servo insertion.
If you had to remove or replace a servo, it is important to follow the correct procedure to insert it back into the mechanism at the correct position. Refer to the instructions for calibration with servo insertion.
Safety Notice for Servo Insertion
When performing the servo insertion procedure, it is necessary to work on the SLG-20 while the unit is powered. This is a potentially dangerous situation if the mechanism was to move without warning.
To mitigate this risk, while inserting the servos and bolting them on to the frame, make sure you never put your fingers inside the mechanism where they could be pinched by the moving parts. The easiest way to prevent injury is to perform this procedure when the SLG-20 is bolted to the aircraft, as it is much easier to do safely when the frame of the SLG-20 is held rigidly.
Calibration using Console – Without Servo Insertion
If your servos are already inserted into the mechanism correctly, use this procedure. This would be the case if you have updated the firmware which will wipe the parameters of the board.
Setting Servo Type
The default servo type for the SLG-20 software is the D951-TW. If your retracts are equipped with HS-7950-TH servos, you must set SRV_TYPE to 1, and if you have D951-TW-V2 servos, you must change the parameter "SRV_TYPE" to 2. If unsure which servos you have, refer to Servo Types
Procedure
Ensure legs are removed from the SLG-20 and springs are disconnected
Power the SLG-20 and ensure the input signal is either disconnected or in the DOWN position
Using the console interface, issue the command “control insert left”
The left mechanism will jump to the insertion position (keep hands well clear)
Using the console interface, issue the command “control cal”
The left servo will move DOWN until it finds the endstop. As it does so, watch the movement of the mechanism. The mechanism must reach the mechanical lockout point
Repeat the process for the right servo
After calibrating both servos, issue the command "param save" to store the calibration in persistent memory
Calibration using Console – With Servo Insertion
HS-7950-TH Servo Type
The default servo type for the SLG-20 software is the D951-TW. If your retracts are equipped with HS-7950-TH servos, you must set SRV_TYPE to 1, and if you have D951-TW-V2 servos, you must change the parameter "SRV_TYPE" to 2. If unsure which servos you have, refer to Servo Types
Procedure
Ensure SLG-20 legs are removed from the SLG-20 and the springs are disconnected.
Power the SLG-20 and ensure the input signal is either disconnected or in the DOWN position.
Using the console interface, issue the command “control insert left”.
The left servo will jump to the insertion position. (The left servo goes in the module with the control board).
Hold the mechanism in the insertion position (with the secondary arm parallel with the frame, see below). Insert the servo into the mechanism and bolt it in.
Using the console interface, issue the command “control cal”.
The left servo will move DOWN until it finds the endstop. As it does so, watch the movement of the mechanism. The mechanism must reach the mechanical lockout point.
Repeat the process for the right servo. (The right servo goes in the module without the control board).
After calibrating both servos, issue the command "param save" to store the calibration in persistent memory.
Insertion Position
When inserting the servo into the mechanism, the mechanism must be held in the "Insertion Position". This position is when the secondary support arm is parallel with the frame, as shown in the pictures below. If it is not possible to insert the servo with the arm straight, err on the side of having the mechanism extended slightly in the "Legs down" direction.
Last updated
