PID for DC motor

[isso11]

Hi Trent,
I need to design a PID to control the speed of a simple DC motor attached with an optical encoder using your lib. I have some issues utilizing your lib, would you please note down the sequence of the functions in your lib.? in ordered steps.

[tcleg]

Hi isso11,

Sure. I'm assuming you're using the C++ library. Here are the basic steps:

1. Start by creating a class instance by calling the function
   PIDControl. Pass all of the initial arguments to the function.
2. Next, if you already have a default setpoint in mind, call the
   PIDInputSet function. Otherwise, the setpoint will be set to a default of
   zero.
3. After the amount of time passes (indicated by the sampleTimeSeconds
   value passed to the PIDControl function) , call the PIDInputSet function
   and pass the input that was sampled to it.
4. Immediately after, call the PIDCompute function.
5. Now, the new updated PID controller output value can be obtained by
   calling the PIDOutputGet function.
6. Afterward, proceed to repeat steps 3-5 as desired.
7. If the setpoint or gain constant values have to be adjusted at any
   point in this process, use the PIDSetpointSet and PIDTuningsSet functions
   respectively.

That's the basic gist. I suppose you want for the PID controller to
regulate the speed of a DC motor by using the encoder as a feedback device?

Sounds like a good exercise.

On Fri, Jul 8, 2016 at 5:30 PM, isso11 notifications@github.com wrote:

Hi Trent,
I need to design a PID to control the speed of a simple DC motor attached
with an optical encoder using your lib. I have some issues utilizing your
lib, would you please note down the sequence of the functions in your lib.?
in ordered steps.

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-Trent Cleghorn

[isso11]

Thank you for replying and help. Actually I'm using the C lib. I'm using Tiva C TM4C123GH6PM microcontroller with Keil IDE. The exercise targeted is as follows : get coordination data from an IMU, use the values of pitch or roll to alter PWM value and control the speed of a dc motor.
Does the sequence differ ?
With the new given data, is there any other notes you'd recommend concerning with PID design?

Regards

[tcleg]

The sequence shouldn't differ. They're virtually the exact same libraries.

The C version is written in an object-oriented style and is the same
library I used for my auto-balancing robot project back in college.
Ironically enough, I also used the TM4C123G on that project with Code
Composer Studio. We used the Tiva C Launchpad for prototyping. Except on
that project, we were using something called a Cascade Controller, which is
two PID controllers cascaded together to generate the final output.

On Sat, Jul 9, 2016 at 9:47 AM, isso11 notifications@github.com wrote:

Thank you for replying. Actually I'm using the C lib. I using Tiva C
TM4C123G with Keil IDE.
Does the sequence differ ? is there any other notes?

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-Trent Cleghorn

[isso11]

Hi Trent,
I have some issues. First I'm using a PWM module in Tiva C to generate pulses' signal with duty cycle varying in a manner corresponding to a value from 0 to 40000 (where 0: 0% duty , 10000:10% duty, 20000: 50% duty, 40000: 100% and so on... written to comparator register of PWM module)..
An external interrupt is used to count encoder pulses, and a timer module is used to set the update rate (dt).. �
Could you guide me- What's more promising for a DC motor: speed PID control, or positon PID control? and what's the input to the PID in this case, is it the number of pulses counted within dt, or the calculated speed of motor in rev/min ? and also for the set point? and for the output ?
I just need some hints..

Many Thanks,
Islam