thermal/tmon/pid.c

1 // SPDX-License-Identifier: GPL-2.0-or-later
29  * PID (Proportional-Integral-Derivative) controller is commonly used in
39  *   y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
40  *          - 2*x[k-1]+x[k-2])/Ts
46 static double xk_1, xk_2; /* input temperature x[k-#] */
51  * 2. calculate PID based on Ziegler-Nichols rule
73 	syslog(LOG_DEBUG, "TC inactive, relax p-state\n");  in controller_reset()
81  *    y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
82  *          - 2*x[k-1]+x[k-2])/Ts
86 void controller_handler(const double xk, double *yk)  in controller_handler()
88 	double ek;  in controller_handler()
89 	double p_term, i_term, d_term;  in controller_handler()
91 	ek = p_param.t_target - xk; /* error */  in controller_handler()
100 	p_term = -p_param.kp * (xk - xk_1);  in controller_handler()
102 	d_term = -p_param.kp * p_param.kd * (xk - 2 * xk_1 + xk_2) / p_param.ts;  in controller_handler()
109 	/* clamp output adjustment range */  in controller_handler()
110 	if (*yk < -LIMIT_HIGH)  in controller_handler()
111 		*yk = -LIMIT_HIGH;  in controller_handler()
112 	else if (*yk > -LIMIT_LOW)  in controller_handler()
113 		*yk = -LIMIT_LOW;  in controller_handler()