PI CONTROL ALGORITHM - SERIES IMPLEMENTATION

PI.c

/*          PI CONTROL ALGORITHM - SERIES IMPLEMENTATION
** /desc    Algoritimo para Controlador Proporcional Integrativo Diferencial.
**  ref1: https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/902/PI-controller-equations.pdf
** /var		r é o valor desejado para a saída, o 'set-point'.
** /var 	y é o valor da saída.
** /ret		retorna a ação de controle u.
*/
float pi(float r, float y){
	// PI CONFIGURATIONS:
	const float Kp = 0.08*0.8;		// analog series proportional gain
	const float Ti = 5e-3;		// analog series integration period
	const float Ts = PERIOD;		// digital sampling period

	// INTERNAL CONSTANTS COMPUTATION:
	const float a0 = -Kp;		// IIR coefficient for old sample
	const float a1 = Kp*(1+Ts/Ti);	// IIR coefficient for new sample

	// CONTROLLER STATIC VARIABLES
	static float e0 = 0;			// old error
	static float e1 = 0;			// new error
	static float u = 0;			// control action

	// Compute error:
	e0 = e1;
	e1 = r -y;

	// Compute control action:
	u += + a1*e1 + a0*e0;

	// Anti windup
	//if(u < D_MIN)		u = D_MIN;
	//else if(u > D_MAX)		u = D_MAX;

  	return u;
}