# Hard/Instantaneous Breaking possible?

I have the Odrive v3.5 48v board, and have it hooked up to two hoverboard motors. All calibrated fine using the Hoverboard Calibration doc here on the website.

Is it possible to have the motors break faster then they currently do? Here is what ours do at the moment:

And here is what we’d like for it to do (at about the 3:00 mark):

Is this achievable with the ODrive?

Thanks!

In what mode are you controlling the odrive? How do you power the odrive?

`odrv0.axis0.controller.config.control_mode`

If you use position control mode you could try to increase the deacceleration value at

`odrv0.axis0.trap_traj.config.decel_limit` in steps/s²

But you need to watch out to not make it too large, because then you could run into overvoltage problems. So tweaking of the power resistor value may also be needed to get large enough values.

To add to @LowiekVDS’s point, any time you perform large decelerations on anything with inertia you will be putting the odrive into a quadrant where your motor is acting like a generator where power flows from the motor back onto the odrive DC bus rather than the other way around. This is perfectly acceptable as long as you have somewhere to send that power. Without having a mechanism to either bleed off the power or store it, the DC bus voltage will start to rise until it gets to a condition where the odrive will fall over to a fail-safe condition due to excessive bus voltages.

The odrive comes with a resistor that can be used to bleed off excessive bus voltages. Make sure at a minimum you have that hooked up. It would be best to figure out how big of a change in kinetic energy you are looking for in order to make sure your bleed circuit is sized appropriately. Power is in units of watts which is equivalent to 1 J/s. Hyperphysics has a good explanation of what kinetic energy is and how to calculate it.

I am in Velocity Control:

`odrv0.axis0.controller.config.control_mode = CTRL_MODE_VELOCITY_CONTROL`

How do I go about configuring the motors once I have them in Position Control?

Very true! I have the 2 ohm resistor that came with the ODrive installed for this exact reason. Would you suggest just a larger value/wattage resistor for harder stops or a different approach entirely? Like a circuit or something else?

To get a sharper response, you need to increase the gains.

I can’t directly answer your question without knowing a lot more about your test setup and what magnitude of deceleration you are trying to achieve. Wheel inertia is important. I’m also not sure what the power rating is on the power resistor that is shipped with the odrive.

Is this just done with the setup guides? I keep adjusting the gain values listed in the hoverboard section, but I can’t seem to get it tuned right… are those the only gain values I need be concerned with? Or are there others?