Hi Odrive community!
I just got my Odrive yesterday and I’m eventually going to be working on a position control project, but for now I don’t have an encoder to use with my gimbal BLDC motor, so to start, I wanted to play with sensorless control. Well technically it does have an encoder but the encoder can only interface with SPI/I2C/PWM, but not AB/I pulse encoding. I hope to eventually update firmware to interface with this encoder through SPI.
Here is a link to the motor specs:
Yesterday I was able to get some progress going with odrivetool on Ubuntu, and by the end of the day when I boot up the Odrive my motor slowly ramps up to what LOOKS close to my vel_setpoint, but then comes to a sudden stop as soon as it gets there, and won’t budge until a reboot. I say “as soon as it gets there” only because if I set a much faster vel_setpoint and reboot, it speeds up beyond where it had stopped before and stops once it gets to a speed that again LOOKS close to the new vel_setpoint. This behavior is consistent with whatever vel_setpoint I program as well as spin_up_acceleration. I’ve played with different controller.config.vel_gain and vel_integrator_gain values but I cannot change the behavior. On previous posts I saw that when people had this problem, it could be solved by correctly tuning the vel_gain/vel_integrator_gain, and also being very sure about the sensorless_estimator.pm_flux_linkage value.
HERE’S WHAT I’VE DONE:
14.915258407592773 //Also tried with 20V, 24V and 12V to the board, same results
odrv0.axis0.motor.config.motor_type = MOTOR_TYPE_GIMBAL
odrv0.axis0.motor.config.pole_pairs = 11 //the motor is “configuration 24N22P” - 22 Magnets, 11 pole pairs
odrv0.config.brake_resistance = 0.6 //Using the provided 50W resistor, ohmeter measures 0.6 ohm
odrv0.axis0.motor.config.current_lim = 1 //Specs show motor rated for 1.2A
odrv0.axis0.motor.config.calibration_current = 1
odrv0.axis0.controller.config.vel_gain = 0.01
odrv0.axis0.controller.config.vel_integrator_gain = 0.05
odrv0.axis0.controller.config.control_mode = 2
odrv0.axis0.controller.vel_setpoint = 500
odrv0.axis0.sensorless_estimator.config.pm_flux_linkage = 5.51328895422 / (11*143) //Specs show KV = 143
odrv0.axis0.config.startup_motor_calibration = True
odrv0.axis0.config.startup_encoder_index_search = False
odrv0.axis0.config.startup_encoder_offset_calibration = False
odrv0.axis0.config.startup_closed_loop_control = False
odrv0.axis0.config.startup_sensorless_control = True
//Motor immediately turned ~60degrees counter clockwise (calibration?) then began ramping up quickly and abruptly stopped, there is some holding torque (harder to turn by hand than if it were powered off)
//So then I did this:
odrv0.axis0.motor.config.phase_resistance = 5.7 //measured with ohmeter as 5.7ohms - consistent for all 3 coils
odrv0.axis0.motor.config.phase_inductance = 0.0007 //Specs say “inductance: 0.7mH”
odrv0.axis0.controller.config.vel_integrator_gain = 0
odrv0.axis0.config.spin_up_acceleration = 30
odrv0.axis0.config.spin_up_target_vel = 500
//From here the motor does not do the initial 60degree turn, but immediately starts slowly ramping up speed (counterclockwise). All is stable until it reaches some speed that seems close to my set point (visually) then suddenly stops with holding torque. As I said above, this behavior is the same for multiple different vel_setpoints and it’s clear that it stops at different speeds depending on the vel_setpoint I give it. Also, I’m sure to mach the spin_up_target_vel with the vel_setpoint I give, but still the result is the same. And every time I reboot those errors are now zero:
Has anyone else run into this issue? I’m pretty stuck Any ideas or advice would be greatly appreciated!!!
I want to at least confirm that I can control the motor speed and direction with sensorless before I start messing around with the firmware, because it will be helpful for me to spin the motor in sensorless with a script in the firmware to confirm that I’m atleast compiling and uploading correctly.
Thank you so much for reading! I’m sorry it was a long one, but I wanted to give as much info as possible,