We are working on Low speed and high torque application robot. In this our robot should pull 500kg to 1000kg at 0.3 m/s. Hence how to configure the odrive pro to operate that speed and torque ? or how to use this drive for that applications.
I would appreciate if someone could tell me solution.
Thank you
Hello! The short answer is yes, a servo drive like the Odrive is likely what you are looking for To answer your question, you’ll need to look a bit more at the details of the drivetrain design. You’ll first want to size the motor and any gear reduction. How much motor torque is needed, and how fast will the motor be spinning at that speed? Don’t forget to assume reasonable losses in the system. The motor torque/current should be under the continuous rating for the motor, unless you know this is a short duty cycle and then you can go above this but less than the peak rating. Half to 2/3 the rated rpm is a reasonable place to start for your operating point assuming you don’t want to drive the system any faster. This can be slower, however, you don’t want to be spinning the motor very slowly at very high torque, the efficiency will be poor.
The other factor is your feedback encoder resolution. If you want a smooth velocity, you’ll need enough encoder resolution to give the feedback loop a good velocity measurement. With the approach I describe above, you’d be in good shape, potentially even with sensorless control, though only if the motor load at startup is low.
Any other concerns you wanted feedback on? Feel free to come back with technical questions about your application. Good luck!
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Thank you for the information.
We are using 2 AMT102 encoder for speed measurements that are connected to two free wheel at front side of our robot. The drive motor at back side and this will pull the 1000 kg load in range of 20 -120 rpm. The continuous torque at this time was 45 Nm. Also the peak torque at below 30 RPM is 120 Nm.
A TI microcontroller was used to generate the speed command in the form of PWM. The feedback for this controller is taken from the AMT102 encoders and reference is given through compute board. This error passed through PI and get the PWM (speed ref). Again this speed refrence is given to the drive controller to trigger the Mosfets (to energize the motor windings).
However when we give this PWM to odrive there was no response from the motor.
Kindly advise how to operate odrive by giving external PWM (from microcontroller).
Connection of odrive is as follows:
1.50.4 V , 36 Ah battery was connected to odrive DC supply
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Motor three phase wires were connected to the odrive three phases
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Motor hall sensors connected to the Hall A, B, C (J8_ 5,12,13) connector along with 5 V (J8_5)and GND (J8_4)
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External PWM connected to the GO8 (J12_ 3 pin) and direction to GO9 (J12_4), ground to ISO gnd (J12_2 pin )
Are the torques and rpms you are quoting at the motor, or is that at the wheel and there is gear reduction to the motor? A hover board motor is as close as I’m aware, which I’ve seen ~12 N*m torque rating and ~600 rpm no load speed at 48V. Hopefully you are using a more reasonable motor spinning at least a few thousand rpm with gear reduction.
It would be much better to connect the encoder to the motor controller rather than a separate microcontroller. If connected to the motor controller, the commutation at low speed will be much improved for better slow speed commutation (torque and efficiency).
But the real reason is that if the Odrive gets the encoder feedback directly, you can operate it in velocity control mode with much better performance
than with hall feedback. Velocity control with halls would only provide his results at higher motors speeds. The Odrive can the report the actual speed to your external microcontroller at whatever update interval you like, say 10-100 Hz.
Depending on the application, everything I just said also applies for Position rather than Velocity mode.
- What operating mode are you trying to use on the Odrive?
- Have you gone through the documentation to configure the Odrive? Are you getting error feedback?
- I’m sure you are, but you should be testing with an unloaded motor to get the configuration sorted out first.
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