Encoders

Manual Homing

A first manual home position calibration of all axes needs to be performed before the automatic homing can be used. This is also true if there was a power outage or the hand-held terminal was used to control the feedthrough motors.

1. Start encoder control in terminal mode such that it displays positions in counts. See known zero position in the below table.
2. Open python in interactive mode including FeedthroughMotorControls.py (e.g. bpython -i FeedthroughMotorControls.py). Check if Axis Parameters are set correctly, meaning is ROTARYAXIS and LINEARAXIS defined correctly in the file.
3. Initialize COM Port to motor controller: initFeedtrough(COMPORT)
4. Initialize Axis with either: initLinearAxis() or initRotaryAxis()
5. Start moving in small steps in the negative direction: moveVertical(ONETURN/4) or moveHorizontal(ONETURN/4)
6. One can check the end limit switches with the following command: MOTOR.getParameter("IX") where X = 1,2 and AXIS = LINEARAXIS or ROTARYAXIS. 0 means switch is inactive, 1 means switch is active.
7. If the end switch is reached, one sets this position as the zero position (no need to be very accurate) with the following command: MOTOR.setParameter("C1",0). Additionally one sets the user register R1 to 1 with MOTOR.setParameter("R1",1), this register will be checked by the automatic homing algorithm.

Linear Axis:

Parameter	Downstream (lasertwo)	Upstream (laserone)
LINEARAXIS	1	2
Upper Limit Switch	I2 / S2	I2 / S2
Upper Limit Switch Position	Encoder: 0007368572 / Motor: 0	Encoder: 0007396810 / Motor:
Lower Limit Switch	I1 / S1	I1 / S1
Lower Limit Switch Position	Encoder: 0015832471 / Motor: 1708267	Enc: 001585296 / Motor: 1705951

Rotary Axis:

Parameter	Upstream	Downstream
ROTARYAXIS	2	1
Clockwise Limit Switch	I2 / S2	I2 / S2
Clockwise Limit Position	E: / M: 0	E: 118.098 / M: 0
CClockwise Limit Switch	I1 / S1	I1 / S1
CClockwise Limit Position	E: / M: 0	E: -56.015999 / M: 620462

Automatic Homing

The automatic homing procedure is based on the homing command of the motor controller. One of the two limit switches is set as a home switch (so far alway S2) then the homing command is issued to the motor controller, initiating a slew at maximum velocity in the minus direction until the home switch is hit followed by a creep at minimum velocity in the plus direction until the home switch is released. This procedure guarantees a repeatable start position. The function is surrounded by two safety checks:

1. Was a manual homing performed
2. During homing the position is monitored and the movement is aborted if the position deviates to far into the minus direction from the manually set 0 position.

Linear Encoder :

positive direction --> moving down

Rotary encoder:

measurement: 200000 steps = 14.04deg