wienne

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CC3D, Radio, Servo, Not smooth
« on: December 14, 2019, 03:18:14 am »
CC3D was used as the gyroscope of the drift car, and two Align DS515M Digital Servos were connected in a fixed-wing V tail.

DS515M Digital Servo Specifications:
@ 4.8V: 55.54 oz in (4.0kg.cm)
@ 6.0V: 69.43 oz in (5.0kg.cm)
Motion speed:
@ 4.8V: 0.12sec / 60 °
@ 6.0V: 0.101sec / 60 °
Rating voltage: DC 4.8-6V
Temperature range: -20 ° C ~ + 60 ° C
Dimension: 35.1x15.1x29mm
Weight: 29g
Band: 1520μs standard band

After pressing the following settings:
Controller type: OpenPilot CopterControl 3D
Vehicle type: Fixed wing
Vehicle sub type: Unknown
Input type: Futaba S.Bus
Speed ​​Controller (ESC) type: Standard ESC (50 Hz)
Servo type: Digital Servos (333 Hz)

When the direction of the vehicle body is offset, CC3D automatically controls the steering of the front wheel steering gear, and the steering gear rotates very smoothly at this time.


Symptom: When using the Radio(Futaba 7px) to steer, the rotation of the steering gear has a noticeable sense of freeze, or a very short sense of pause.
The steering of the front wheels is like walking in a grid, turning about 3-5 degrees at a time (approximately estimated).
After running on the ground for three to five minutes in this way, the steering gear became very hot.
The steering hardware of the front wheels is smooth and unobstructed.

What could be the problem?

Try solution:
1. Modify the type of CC3D servos from digital to analog, that is, 50Hz. The sense of pause is more serious.

2. The 333hz of the digital servo was changed to other alternatives such as 300, 400, etc., which did not solve the problem.

3. Connect the steering gear back to the receiver and use the remote control to control the steering gear and steering mechanism to rotate smoothly.

4. The use of receiver power, rather than CC3D, failed to resolve.

5, using an external power supply DC-DC, 6V, max 3A, instead of the receiver power supply, failed to resolve.

6, cleared the configuration, re-flash the firmware, and so on countless times, failed to resolve.

7, using the second CC3D, still not resolved.

Re: CC3D, Radio, Servo, Not smooth
« Reply #1 on: December 14, 2019, 04:09:43 am »
CC3D was used as the gyroscope of the drift car, and two Align DS515M Digital Servos were connected in a fixed-wing V tail.
I'm not sure what you mean here.  I just assume that this is a drift car with these servos for steering.

After running on the ground for three to five minutes in this way, the steering gear became very hot.
The steering hardware of the front wheels is smooth and unobstructed.
Are you saying that the steering servos got hot?  If so, I suggest you try setting the D term of your PIDs to zero.  D term can cause high frequency oscillation that is too fast to see.

You can also try to drive it around in Manual mode to make sure that it doesn't get hot when unstabilized.

wienne

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Re: CC3D, Radio, Servo, Not smooth
« Reply #2 on: December 16, 2019, 02:22:02 pm »
Thanks for your reply, I will test record the video in these two days.




In the first part of the video, the servo is a direct receiver.
I use the remote control to control the steering, and I think the sound from the servo is normal.

In the second segment of the video, the steering gear passed CC3D, and the steering was controlled using the remote control.
You can hear the sound of the steering gear turning, which I think is abnormal.

There was a pause.

This kind of abnormal sound, I guess may be some kind of problem with CC3D, or the parameter is incorrect.
But I don't know what went wrong.

No PID-related settings were used during this period


Re: CC3D, Radio, Servo, Not smooth
« Reply #3 on: December 16, 2019, 05:45:44 pm »
I hear the typical servo sound at first and then the high frequency sound of a digital servo second.  If the servo was being powered with the same voltage in both cases (typically that is 5 volts) then the difference in sound is caused by talking to the servo as if it were a normal servo (50Hz) in the first case and talking to it as a digital servo (higher than 50Hz) in the second case.

This will probably be corrected on the Output page, by setting the Update Rate (Mode is PWM) to whatever the servo is designed for.  Right now the Update Rate seems to be set too high.  I would not just turn it down until it works because it can still get hot if talking too fast.  To make the second case sound and act like the first case set the outputs to PWM and 50Hz.  As far as I know, 50Hz is always safe.

This also explains the servo getting hot.

If this corrects the problem then you can set your PID D term back where it was.

This thread talks about a car, so it should probably go in the "Vehicles - Ground" section of the forum.  :)

wienne

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Re: CC3D, Radio, Servo, Not smooth
« Reply #4 on: December 17, 2019, 10:20:39 am »
I use a digital servo, which was originally used for helicopter models.

In the setting column of the motor, I changed the frequency to something other than 333hz such as 50, 60, 125, 270, 330, 400, 490. The higher the value, the less jitter can be seen when the servo rotates.
If you choose 50hz, the rotation of the servo, or describe it as jitter, is more suitable.
But today I want to make a video. At 50hz, the crazy jitter is gone.

CC3D is indeed installed in the car model, but the configuration of CC3D is fixed wing + V tail.
Because my car model uses 2 rudders, the CC3D vehicle model only supports 1 rudder.
I was also very helpless, so I chose to discuss it on the fixed-wing section.

My CC3D is really strange. After re-flashing the firmware,
It is still 333hz, other settings are not changed, but the servo does not have strong jitter.
At the same time the steering gear no longer overheated.
However, slight jitter is still present.

Re: CC3D, Radio, Servo, Not smooth
« Reply #5 on: December 17, 2019, 08:12:29 pm »
A servo directly connected to perfectly steady signal can have a small buzz (50Hz) or squeal (higher than 50Hz) because servo is not perfectly centered.  Not visually noticeable.  FC in LibrePilot Manual mode is like this.

When servo gets signal from stabilized FC it will jitter a little more with tiny motions actually visible sometimes.  FC in LibrePilot Rate, etc. (anything but Manual) mode is like this.

If your servo doesn't get hot, and servo is using fastest signal it is designed for, then this is the best you can do.

Now to tune PIDs.  Beware that changing servo pulse repetition rate needs changing of PID to match it.  Low tuned PIDs can work with fast servo rate but it will not respond as quickly as it could.  High tuned PIDs will oscillate if used with slow servo rate.
« Last Edit: December 17, 2019, 08:18:38 pm by TheOtherCliff »