UM0585

PID controller

Doc ID 14988 Rev 2

7/25

2

PID controller

2.1

Description

The proportional-integral-derivative or PID controller is commonly used in the industry. It is a

feedback loop controller that manages the process command with a view to reducing the

error between the desired set point and the measured process variable.

The following block diagram shows the parallel structure of a PID controller. This is the

structure implemented in this DSP library.

Figure 1.

Block diagram of PID controller

2.2

DSP library functions

The DSP library provides three PID functions:

●

DoPID

: a PID core loop coded in C (the error is computed outside the function)

●

DoFullPID

: a full PID controller coded in C (with error computing)

●

PID_stm32

: an optimized PID core loop written in assembly

2.2.1

DoPID

function

Table 2 describes the DoPID function.

Example

/* Fill the coefficients table */

Coeff[0] = Kp;/*proportional coefficient*/

+ -

+

+

+

In

Ref

Error

Output

P

I

D

Process

command

ai15447

Table 2.

DoPID

function

Function name

DoPID

Prototype

uint16_t DoPID(uint16_t Error, uint16_t *Coeff)

Behavior description

PID in C, error computed outside the function.

Input parameter

– Error: difference between reference and measured values

– Coeff: pointer to the coefficients table

Output parameter

None

Return parameter

PID output command