Hello @maes2ro,

- In this test are you using SOLO in Speed mode or Torque mode?

- Have you tried to apply to P/F pin a 5V input during stop conditions to set the current limit at Zero? after doing this SOLO will stop the switching at the output, and there must be no resistance, however, the drive will go into OCP mode ( over current protection ), thus once you want to start the motor again, you'll need to release the P/F pin from the 5V and you'll need to reset the Error by writing zero into the error register, to that end you'd need to use USB, UART or CAN line, you can also do this resetting action in motion terminal for your initial tests.

Let me know if this could help or if you have any other questions.

Milad

@milad I am using the drive in open loop torque mode. If I short the P/F input to ground, to ensure that there is no commanded input, there is still resistance to movement of the motor if I move it by hand, and there are no errors generated. If I switch the drive off, then there is no resistance at all.

We might see a similar behaviour I think if we connected a short across the motor and tried to move it, then back emf in the windings would create a braking effect. Might we be seeing something like that here?

I'm still trying to understand the control mechanism that is causing this phenomenon.

To review my setup: The controller is in analogue, sensorless, torque mode and I have a brushed DC motor.

I can confirm that the P/F input is zero, and I have tied it to ground to confirm that state. It's pretty clear that there is no drive being applied because the motor does not move and the voltage at the terminals is zero.

I have connected a voltmeter to the motor terminals to try and get more information, and what happens is that if I move the motor by hand I can see a voltage developed on the motor terminals, which is exactly as I would expect. At the speed I am trying to move, this is about 3V max.

What I am trying to understand is why I feel resistance to this movement if there is no torque command. This must be a function of the control loop because if I switch off power to the Solo drive this residual torque completely disappears and the motor can be turned freely.

I have tried this with the regenerative resistors disconnected and also with supply voltages down to the minimum 8V, and the damping effect is the same.

I'm trying to form a concept of what the controller is trying to do here: is it trying to hold the drive current at zero by applying a negative control voltage equal to the voltage generated by the motor when I try and move it? In which case I guess I would experience this as a resisting torque?

I would greatly appreciate any thoughts you might have as I urgently need to find a way to either avoid this problem or develop a work-around

Hi @maes2ro,

Posted by: @maes2ro

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I can confirm that the P/F input is zero

P/F input in closed-loop mode once Grounded ( connected to 0 volts) will cause you to have the maximum current Limit of 32A! So to disable the current, you need to connect P/F directly to 5V ( please check the user manual and there you'll see the relation between P/F voltage and current limit is actually reverse).

Once you connect P/F to 5V directly, SOLO will stop switching at the output completely, thus the Mosfets are completely disconnected, however, due to the body diode of the Mosefts they can still redirect the current to the BUS if the Motor moves fast enough, in any case once the P/F is at 5V ( zero current limit) you will have SOLO completely disconnected from your motor.

Another Point is once P/F goes to 5V, SOLO will enter into OCP (over-current protection) mode as well and the E1 LED will start to Blink, thus to make the unit operational again, you need to reset the Error register ( through UART, USB or CAN bus)  or if you can't do that you need to recycle the power of the unit.

let me know if you have other questions.

Milad

Hi Milad

My apologies, I am setting S/T to zero to command zero torque.

Is P/F a functional input when switch 4 is in torque mode?

Hi @maes2ro,

Posted by: @maes2ro

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My apologies, I am setting S/T to zero to command zero torque.

 

Ok this is good.

Posted by: @maes2ro

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Is P/F a functional input when switch 4 is in torque mode?

Yes it is, it again defines the current limit.

Please test the situation with P/F connected to 5V and let me know the feeling then.

Remember, zero torque reference is very different with no resistance in the Motor, the 0 reference is for the controller, so once you move externally the motor, you are creating a non-zero feedback and the controller wants to bring it back to zero and that's why you might see some resistance.

For this part, you can also change the Current controller gains of Kp and Ki, and reducing them ( specially Kp) and seeing if the resistance drops.

remember that new current controller gains will be applied after power recycling.

please test these points and let me know.

Milad