Arduino Math problem

You need to give a lot more detail about your problem - currently the scope addressed by your question is too wide for a simple answer.

Michael Kellett

I have a system that with the feedback it calculate out the acceleration of the motor, then I need to integrate the acceleration to get its velocity then integrate again to get the position of the motor.

As for the transfer function, I have a potential meter and the output of it need to go through a transfer function 1/(0.5s + 1).

Hope this is what you want?

Regards

Chao Hong

I have a system that with the feedback it calculate out the acceleration of the motor, then I need to integrate the acceleration to get its velocity then integrate again to get the position of the motor.

As for the transfer function, I have a potential meter and the output of it need to go through a transfer function 1/(0.5s + 1).

Hope this is what you want?

Regards

Chao Hong

I'm suprised that you have an acceleration signal, velocity or dispalcement are more common - you will find it very difficult to control displacement from acceleration.

The way to tackle this problem is to do the maths first and write the code afterwards. Once you've got the maths sorted the code is easy.

I know a few ways to get the maths done -

find an example  - books - Google etc

work it out from first principles

model the system using something like MATLAB/SIMULINK, VISIM, MAPLE SIM etc etc

One problem is that your Arduino, being digital, can't (no matter how clever the maths) avoid the fact that it will process discrete samples from and ADC with finite resolution - in real systems this is often very important and it is often easier to model the effects rather than calculate them.

Let me know if you have access to any of the tools above and please describe your problem a bit more - what are you trying to control and why. ( If it's a one off and money is no object just buy a controller, if you want to make loads of them cheap that's one problem, if its a hobby thing and you just want to make it work - that's another or if you're a student and you have to do it a particular way .............)

Michael Kellett

Thanks for your patient. I'm a student working on a project of sch.

Mine is like doing an automated rocking chair and I have the fomular and simulink model(done by other) already.

There is a virtual rocking motion in the system which will always use to compare with the actual position of the chair.

I'm using a hall sensor to get the position of the chair. Besides, the acceleration, velocity is just generate by the virtual system through internal setting.

Now I have to program with arduino and I stuck with how to implement integration and transfer function in coding.

Chao Hong

I don't understand what you mean by "virtual rocking motion in the system which will always use to compare with the actual position of the chair" and "velocity is just generate by the virtual system through internal setting".

Does the hall sensor give you a linear output proportional to the position of the chair or just a pulse. What sensor inputs does the 'virtual system' have. What kind of actuator are you using.

If you have a SIMULINK model you could post it here. You should separate out the controller in the model from the system you are controlling (ie separate the plant and the controller). Then you need to use the SIMULINK tools to make a discrete time and quantised controller. Once you've got that (unless it's mega complicated) it will be easy to see how to code it.

int32_t integrate(int32_t input)

     {

     static int32_t integral = 0;

     integral += input;

     return(integral);

     }

Simple (and almost useless) discrete integrator (1/z) in C. There is no means to reset it (which is why it is (probably) useless).

Michael Kellett