How do motors on gimbals work? (2-axis camera mount application)

[emdezla]

Hello everyone,

I am trying to build a 2-axis camera gimbal, which will control yaw and pitch. I have bought sensorless BLDC motors (GB280870KV) which I drive using SPWM. For knowing the camera orientation, I am using IMU sensors (accelerometer, gyroscope, and magnetometer) integrated on the microcontroller board (STM32F3DISCOVERY).

So now my problem comes on how to implement a controller. I don't know how real gimbals work: do motors use a position control strategy or a speed control strategy? In other words, should my motors stop working when the ideal position is reached or should they continue to work at super loooow speeds?

Thank you very much for your answers.

 

[davenn]

I am trying to build a 2-axis camera gimbal, which will control yaw and pitch.

is this for a security camera or something else ?

For knowing the camera orientation, I am using IMU sensors (accelerometer, gyroscope, and magnetometer) integrated on the microcontroller board (STM32F3DISCOVERY).

that's a serious overkill for a security camera, those things are not needed to be known as the camera operator can see where the camera is pointing.
It would only be needed if the camera was fully self controlling

I don't know how real gimbals work: do motors use a position control strategy or a speed control strategy?

usually position control

In other words, should my motors stop working when the ideal position is reached or should they continue to work at super loooow speeds?

that depends on what you are trying to achieve ... no point in it continuing to move past whatever you are wanting the camera to look at

So, maybe some info on what you are actually trying to achieve with this projectDave

 

[Nik_2213]

Um, IMHO, you could cut a LOT of grief by using modelling / robotic servo motors, which have all the feedback / dead-zone / approach stuff built in...

 

[emdezla]

is this for a security camera or something else ?
that's a serious overkill for a security camera, those things are not needed to be known as the camera operator can see where the camera is pointing.
It would only be needed if the camera was fully self controlling
usually position controlthat depends on what you are trying to achieve ... no point in it continuing to move past whatever you are wanting the camera to look at

So, maybe some info on what you are actually trying to achieve with this projectDave

What I am trying to achieve is a stabilized platform for a camera. This platform will be placed on top of a boat and will have to compensate for the boat movements in order to point always in the right direction. The final aim of this project is actually to record boat races so the "right direction" at which the camera should point is the finish line

 

[essenmein]

I would say a sensorless BLDC driver is likely not going to work very well for you, they need a certain amount of motor speed to detect the back EMF to then determine what rotor sector its into then be able to control the machine, basically they don't work too cleanly if the machine is not above some speed. I imagine in your case you'd like it to probably know this location if its not turning and maybe provide some zero speed torque (ie holding position), so you'll want a motor controller that uses a rotor position sensor.

 

[davenn]

What I am trying to achieve is a stabilized platform for a camera. This platform will be placed on top of a boat and will have to compensate for the boat movements in order to point always in the right direction. The final aim of this project is actually to record boat races so the "right direction" at which the camera should point is the finish line

OK great ... that was the sort of info we all needed right at the start

OK, there are already a couple of gimbal systems out there that I am personally aware of.
One where a standard camera eg a DSLR can be mounted into and they give aweome stabilisation
I have always wanted one of them
The other is like those used in drones ... my Parrot drone has a wonderful 3 axis gimbal system in it, keeps the video really stable

It would probably be a great idea to look into what either of those systems are doing/usingEDIT: Ohhh and I think you will probably find you need a 3 axis one ... boats don't move in just 2 directions

Dave

 

[Tom.G]

As @davenn pointed out, his Parrot drone has a stabilized camera. Most likely the fastest and cheapest way is to get one of those systems and modify as needed.