SIN COS Encoder on FBL Series

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Setup and Test the Sin/Cos Encoder Feedback Mode
Sin/Cos encoders are absolute devices. A one-time setup and calibration must be performed in order to calibrate the encoder’s voltage levels, and set the mechanical zero degree angle offset.

The first calibration step measures and stores the minimum and maximum voltages of the encoder’s signals at of each of the controller’s inputs:
After the controller is configured in Sinusoidal mode with Sin/Cos Feedback, from the console, type:
%CLMOD 2 for motor channel 1
%CLMOD 3 for motor channel 2
This will cause the controller to enter the calibration mode. Move the shaft of the motor slowly by hand in order to make a couple of full mechanical turns.
Then press %CLMO 0 (for either motor channels) in order to get out of the calibration mode.
Pressing the command ~ZSMC you can see the calibration values (3 first values for motor 1 and the other 3 for motor 2). Verify that the values are different than 0.
In order to save the calibration values permanently to flash type
%CLSAV 321654987.
You can verify that the sensor works, enable the Angle capture in the Roborun chart. Then move the shaft by hand and verify that the reported angle smoothly ramps from 0 to 512 (512 = 360 electrical degrees).
Once the sensor is verified to be working, a one-time calibration must be performed to captures the mechanical offset of the sensor. In most cases, a small difference exists between the 0 degrees from the sensor vs the actual 0 degrees of the motor. Verify that the motor shaft is rotating freely. Then perform a Zero Angle reference search (See XREF Sinusoidal Zero-Angle Reference Search and Adjustments).

Single Pole vs Multi Pole Sin/Cos sensors
Some sin/cos sensors will produce a full 360 degrees output for each full 360 mechanical turns. These are single pole sensors. Other sensors have multiple poles, meaning that the sine or cosine signal will perform two or more full 360 degrees cycles for every mechanical cycles. The number of sensor poles is a critical configuration parameter which must be set using the Sensor Poles menu. It can also be set from the console or serial port with

^SPOL ch poles


Sinusoidal Zero-Angle Reference Search Process
Most angle sensors will not give an accurate absolute position of the rotor. Incremental encoder give relative position by their nature and must be set with a reference angle at every power up.
Absolute sensors like SPI or Sin/Cos are not always mounted with a precise zero-degree reference and must be calibrated at least one time.

A reference search can be initiated manually by sending the serial command:

!BND 1 for channel 1
!BND 2 for channel 2
The controller will then respond by energizing the U, V and W coils with the voltages levels needed to force the rotor to move to predetermined positions. The sequence is +90, -90, +90, -90, +90 and back to -90 electrical degrees. The reference search is considered a success if the rotor correctly reached the last four end position. The motor will they then be allowed to operate

If the reference search failed, the Bind Error LED will appear in red in the Run screen of the PC utility. The motor will then not be energized if a command is sent.

For the reference search to work, the motor must be free to move at least a full electrical turn (mechanical turn divided by the number of pole pairs). If a brake is present, it must be disengaged during the search sequence.

The amount of current (ie torque) that the controller will apply to the motor for the search is set in the Reference Seek Power menu of the configuration utility, or the serial command:

^BZPW ch Amps*10

Verify then that in open loop, the motor spins at the same speed in the forward or reverse direction when the same command is given with different signs. If the motor rotates at different speeds and/or draws a significantly different amount of current in each direction, the zero degree reference was not captured correctly.