How to configure a rotatory brushless motor with resolver feedback
I have a rotatory brushless motor with resolver as feedback but I don't know how to properly configure it and tune it. What is the right process that I need to follow?
Clarifications and checkings
- This step by step process assumes that your motor does not have a brake. If you do have one, ensure that you have configured it correctly like it is shown in the following article before proceeding with any configuration: How to configure the brake of your motor.
- This step by step process assumes that neither the motor or the power stage of the drive is damaged. Please, if you are not sure of this, follow the instructions in the How to know if the motor phases or the power stage of the drive are damaged article in order to verify it.
- This step by step process assumes that your feedback device is working properly and no noise is coupled to the resolver lines. Please ensure that you have checked this by following the step process described in How to know if the feedback device is working properly.
- This step by step process assumes that there is no digital input mapped to the "Motor Enable" functionality of the drive. If that is the case, ensure to have the digital input ON (if active high, otherwise OFF) in all the steps that involve movement during the configuration or otherwise those steps will fail.
- Once you have connected to the drive, go to the Actuator window and set the right parameters for the Motor Type, Position sensor and Velocity sensor. Your window should look like the following:
- Then, you need to go to the Motor window in order to input all the motor data from its datasheet (it should all be in there). The parameters that you need to input mandatory are torque constant, continuous current, peak current (if known), max permissible speed and motor pair poles. The inductance and the resistance can be obtained in later steps with the system identification included in the torque tuning stage and the rated torque can be determined by the product of torque constant and continuous current. An example of motor parameters for a brushless motor could be the following:
- The next step is to configure the resolver feedback. The resolver is the only feedback device that does not have its particular MotionLab window, so it needs to be configured all by direct register modification of the resolver parameters. We used to use the Register Watcher for that purpose. The following are the parameters that need to be set:
- The resolver pole pairs is an easy one to know since it can be taken from the datasheet, but the resolver polarity needs to be identified through a manual procedure. We advise checking the following link on how to do that: How to calibrate the polarity of your feedback device manually.
- Once the resolver parameters have been correctly set, it is time to calibrate the commutation process, which leads us to 2 cases:
a. The number of resolver pole pairs is a submultiple of the motor pole pairs number
In this case, we can use "Non incremental sensor used" as the Initial angle determination method in order to calibrate the commutation angle. The COMMUTATION window should look like the following in this case:
By using the Calibrate button and selecting the appropriately required torque you should be able to calibrate the motor successfully.
b. The number of resolver pole pairs is a submultiple of the motor pole pairs number
In this case, the "Forced alignment method" needs to be chosen as Initial angle determination method so the user needs to be aware that after every power cycle of the drive the phasing process will need to be done before any movement is commanded. As far as the forced alignment parameters are concerned, here are some basic guidelines in order to choose its values:
- Process time: 2000-5000 ms
- Process current: 5-20% of rated current if done with the motor without a load. If there is a load on the shaft, increase gradually beyond 20% until you get enough movement to get the alignment process done correctly.
- Process tolerance: 5-10%
- After having successfully calibrated the reference sensor, it is of good practice to do a quick verification to ensure that the commutation has indeed been properly calibrated. This can be very easily done by using the Open-loop by using the commutation sensor mode from the Move window while plotting in the Scope both position and velocity actual values. Try applying different target voltages in both directions and check that the motor is spinning at the same speed (for a certain target level) in both directions. If the motor does not spin the same way in both directions, if it spins erratically in one direction or any other strange anomaly please repeat the previous step and recalibrate the initial commutation angle. An example of this verification procedure is shown in the following image:
- Once the calibration is verified, it is time to move to the Limits window. In that window, make sure that your position, velocity and torque limits are properly set accordingly to your system. Make sure that the position limits match your motion range (if there is one), that the velocity/acceleration limits are correct and that the minimum and maximum torque limits match the peak torque value:
- After having set the Limits correctly, make sure that the Protections parameters are set up correctly as well. Adjust the voltage range to your application's and make sure that the maximum system current is equal to or higher than the peak current value:
- After this last step, the configuration is ready to start with the tuning of the different motion loops. In order to do a proper tuning, we advise to take a look at the following links: