How to read the torque of the motor?


#1

Well, after reading your fantastic work, I still have two question about this project. One is can I get current info to calculate torque. Second is can bldc motor generate great torque while the speed is near zero. I am also working on a quadruped robot and I just start the design.


Reading velocity and torque from hoverboard setup
High-torque actuator for legged robots
#2

Sure, take a look in this spreadsheet. The data for this particular motor is on line 13.

Yes. In fact, maximum torque for a DC motor (stall torque) is reached at zero speed.


#3

thank you for your answer


#4

will the odrive provide foc control for the bldc motor?is any extra sensor needed for this function?


#5

Yes, the ODrive does FOC. You don’t need any extra sensors besides the encoder.


#6

well, after searching and reading the documents, i don’t find any information about how to get current information from a computer. this drives me mad. could you please give me a hint on this?


#7

The board is in position control mode by default, so you have to change it to current control mode. Then you can command new values of current_setpoint from the computer.

Look at the “Control Mode” section here.


#8

actually, i mean that i want to get current value in computer but not setting it from this command. i found that i could only get voltage info from odrive board. i want to perform an accurate and fast force control using the t-motor and odrive. after reading some thesis, i find perform an accurate and fast force measure and control with dynamics model is a key to success. i want to do all computation task on my pc, while odrive have not provide the complex function i need, so i want to get current info from odrive to calculate torque in pc and using some other method to finish my control goal through odrive.


#9

I think what you are looking for is to read the property:
odrv0.axis0.motor.current_control.Iq_setpoint. That will tell you the current the motor is trying to do right now.
odrv0.axis0.motor.current_control.Iq_measured is the current that is measured in the current sensors.


#10

what’s the difference for the current_meas_phB+ current_meas_phC compare to Iq_measured? can you do Iq_measured in other mode too(like position control)


#11

current_meas_phB is along the B axis.
current_meas_phC is along the C axis.
Iq_measured is along the q axis, which is the direction that produces torque.
See here: Recommended books/resources.

Yes you can read it at all times.