It depends on how you implement them. I'm running a setup comparable to the nitro RC cars.
Two servos - one connected by cable to the throttle, and one connected by cable to the brake.
The throttle servo has idle at about mid-travel, so for half the range it's not actually pulling on the throttle. The brake servo starts engaging the brake at about the same point the throttle drops to idle.
I set the throttle "RC3_TRIM" to the point where the throttle just starts pulling (around PWM 1500). THROTTLE_MAX is 100% and THROTTLE_MIN is -50%.
It gives me the ability to brake in MANUAL mode, HOLD mode puts it at idle.
In theory, it should also work in AUTO mode, based on the code. I should get "negative" throttle if I'm significantly above my target speed, however I've yet to see it eventuate in practice. I'm still debugging the system though.
One of the problems is that the more conservative your throttle settings (lower P, lower I and lower IMAX), the less braking effect you will see.
Presently we are just using the motor to provide braking.
This weekend at our code hacking hangout we are going to get started on active motor braking where a mild reverse pwm signal (<1500us) will be sent to the motor to increase the motor braking action as an operator would do when in the Manual Mode.
Presently the motor just slows down or speeds up in relation to the throttle pwm input.
We can probably put mechanical braking in the to do list, but for right now we are trying to optimize the rover functions for the AVC.
Replies
It depends on how you implement them. I'm running a setup comparable to the nitro RC cars.
Two servos - one connected by cable to the throttle, and one connected by cable to the brake.
The throttle servo has idle at about mid-travel, so for half the range it's not actually pulling on the throttle. The brake servo starts engaging the brake at about the same point the throttle drops to idle.
I set the throttle "RC3_TRIM" to the point where the throttle just starts pulling (around PWM 1500). THROTTLE_MAX is 100% and THROTTLE_MIN is -50%.
It gives me the ability to brake in MANUAL mode, HOLD mode puts it at idle.
In theory, it should also work in AUTO mode, based on the code. I should get "negative" throttle if I'm significantly above my target speed, however I've yet to see it eventuate in practice. I'm still debugging the system though.
One of the problems is that the more conservative your throttle settings (lower P, lower I and lower IMAX), the less braking effect you will see.
A bigger issue is the fact that throttle nudging in AUTO mode appears broken in that throttling BACK can actually give you full throttle - https://github.com/diydrones/ardupilot/issues/840
Long term, it would be ideal to be able to run two separate channels for brake and throttle so you have full travel on each.
I am going to play around with your set up ideas..
@BTE,
Presently we are just using the motor to provide braking.
This weekend at our code hacking hangout we are going to get started on active motor braking where a mild reverse pwm signal (<1500us) will be sent to the motor to increase the motor braking action as an operator would do when in the Manual Mode.
Presently the motor just slows down or speeds up in relation to the throttle pwm input.
We can probably put mechanical braking in the to do list, but for right now we are trying to optimize the rover functions for the AVC.
Regards,
TCIII ArduRover2 Developer
Ok. Thanks for the quick reply.
If you would, adding it to the to do would be appreciated.
Cheers
Teddy.