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Closed Loop Position Mode
118 AX2500/2850 Motor Controller User’s Manual Version 1.7. February 1, 2005
In the Position mode, the controller compares the actual position, as measured by the sen-
sor, to the desired position. If the motor is not at that position, the controller will apply
power to the motor so that it turns towards that destination, until reached.
Important Warning:
If there is a polarity mismatch, the motor will turn in the wrong direction and the
position will never be reached. The motor will turn continuously with no way of
stopping it other than cutting the power or hitting the Emergency Stop buttons.
Determining the right polarity is best done experimentally using the Roborun utility (see
“Using the Roborun Configuration Utility” on page 159) and following these steps:
1. Disconnect the controller’s Motor Power (thick power wires).
2. Configure the controller in Position Mode using the PC utility.
3. Loosen the sensor’s axle from the motor assembly.
4. Launch the Roborun utility and click on the Run tab. Click the “Start” button to
begin communication with the controller. The sensor values will be displayed in the
Ana1 and Ana2 boxes.
5. Move the sensor manually to the middle position until you measure “0” using
Roborun utility
6. Verify that the motor sliders are in the “0” (Stop) position. Since the desired posi-
tion is 0 and the measured position is 0, the controller will not attempt to move the
motors, and the Power graph on the PC must be 0.
7. Apply power to the Motor Power wires (thick power wires). The motor will be
stopped.
8. With a hand ready to disconnect the Motor Power cable, or ready to press the “Pro-
gram” and “Set” buttons at the same time (Emergency Stop), SLOWLY move the
sensor off the center position and observe the motor’s direction of rotation.
9. If the motor turns in the direction you moved the sensor, the polarity is correct. You
may tighten the sensor axle to the motor assembly.
10. If the motor turns in the direction away from the sensor, then the polarity is
reversed. You should either exchange the wire polarity on the motors. If you are
using a potentiometer as sensor, you can instead the 0 and +5V wires on the poten-
tiometer. If you are using an Optical Encoder, you can swap its ChA and ChB out-
puts.
11. Move the sensor back to the center point to stop the motor. Cut the power if you
feel you are losing control.
12. If the polarity was wrong, invert it and repeat steps 8 to 11.
13. Tighten the sensor.
Important Safety Warning