1cd5e85f5SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
294f69966SJacob Pan /*
394f69966SJacob Pan * pid.c PID controller for testing cooling devices
494f69966SJacob Pan *
594f69966SJacob Pan * Copyright (C) 2012 Intel Corporation. All rights reserved.
694f69966SJacob Pan *
794f69966SJacob Pan * Author Name Jacob Pan <jacob.jun.pan@linux.intel.com>
894f69966SJacob Pan */
994f69966SJacob Pan
1094f69966SJacob Pan #include <unistd.h>
1194f69966SJacob Pan #include <stdio.h>
1294f69966SJacob Pan #include <stdlib.h>
1394f69966SJacob Pan #include <string.h>
1494f69966SJacob Pan #include <stdint.h>
1594f69966SJacob Pan #include <sys/types.h>
1694f69966SJacob Pan #include <dirent.h>
1794f69966SJacob Pan #include <libintl.h>
1894f69966SJacob Pan #include <ctype.h>
1994f69966SJacob Pan #include <assert.h>
2094f69966SJacob Pan #include <time.h>
2194f69966SJacob Pan #include <limits.h>
2294f69966SJacob Pan #include <math.h>
2394f69966SJacob Pan #include <sys/stat.h>
2494f69966SJacob Pan #include <syslog.h>
2594f69966SJacob Pan
2694f69966SJacob Pan #include "tmon.h"
2794f69966SJacob Pan
2894f69966SJacob Pan /**************************************************************************
2994f69966SJacob Pan * PID (Proportional-Integral-Derivative) controller is commonly used in
30*7a12f918SSlark Xiao * linear control system, consider the process.
3194f69966SJacob Pan * G(s) = U(s)/E(s)
3294f69966SJacob Pan * kp = proportional gain
3394f69966SJacob Pan * ki = integral gain
3494f69966SJacob Pan * kd = derivative gain
3594f69966SJacob Pan * Ts
3694f69966SJacob Pan * We use type C Alan Bradley equation which takes set point off the
3794f69966SJacob Pan * output dependency in P and D term.
3894f69966SJacob Pan *
3994f69966SJacob Pan * y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
4094f69966SJacob Pan * - 2*x[k-1]+x[k-2])/Ts
4194f69966SJacob Pan *
4294f69966SJacob Pan *
4394f69966SJacob Pan ***********************************************************************/
4494f69966SJacob Pan struct pid_params p_param;
4594f69966SJacob Pan /* cached data from previous loop */
4694f69966SJacob Pan static double xk_1, xk_2; /* input temperature x[k-#] */
4794f69966SJacob Pan
4894f69966SJacob Pan /*
4994f69966SJacob Pan * TODO: make PID parameters tuned automatically,
5094f69966SJacob Pan * 1. use CPU burn to produce open loop unit step response
5194f69966SJacob Pan * 2. calculate PID based on Ziegler-Nichols rule
5294f69966SJacob Pan *
5394f69966SJacob Pan * add a flag for tuning PID
5494f69966SJacob Pan */
init_thermal_controller(void)5594f69966SJacob Pan int init_thermal_controller(void)
5694f69966SJacob Pan {
5794f69966SJacob Pan
5894f69966SJacob Pan /* init pid params */
5994f69966SJacob Pan p_param.ts = ticktime;
6094f69966SJacob Pan /* TODO: get it from TUI tuning tab */
6194f69966SJacob Pan p_param.kp = .36;
6294f69966SJacob Pan p_param.ki = 5.0;
6394f69966SJacob Pan p_param.kd = 0.19;
6494f69966SJacob Pan
6594f69966SJacob Pan p_param.t_target = target_temp_user;
6694f69966SJacob Pan
67d7fbdc57Sran jianping return 0;
6894f69966SJacob Pan }
6994f69966SJacob Pan
controller_reset(void)7094f69966SJacob Pan void controller_reset(void)
7194f69966SJacob Pan {
7294f69966SJacob Pan /* TODO: relax control data when not over thermal limit */
7394f69966SJacob Pan syslog(LOG_DEBUG, "TC inactive, relax p-state\n");
7494f69966SJacob Pan p_param.y_k = 0.0;
7594f69966SJacob Pan xk_1 = 0.0;
7694f69966SJacob Pan xk_2 = 0.0;
7794f69966SJacob Pan set_ctrl_state(0);
7894f69966SJacob Pan }
7994f69966SJacob Pan
8094f69966SJacob Pan /* To be called at time interval Ts. Type C PID controller.
8194f69966SJacob Pan * y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]
8294f69966SJacob Pan * - 2*x[k-1]+x[k-2])/Ts
8394f69966SJacob Pan * TODO: add low pass filter for D term
8494f69966SJacob Pan */
8594f69966SJacob Pan #define GUARD_BAND (2)
controller_handler(const double xk,double * yk)8694f69966SJacob Pan void controller_handler(const double xk, double *yk)
8794f69966SJacob Pan {
8894f69966SJacob Pan double ek;
8994f69966SJacob Pan double p_term, i_term, d_term;
9094f69966SJacob Pan
9194f69966SJacob Pan ek = p_param.t_target - xk; /* error */
9294f69966SJacob Pan if (ek >= 3.0) {
9394f69966SJacob Pan syslog(LOG_DEBUG, "PID: %3.1f Below set point %3.1f, stop\n",
9494f69966SJacob Pan xk, p_param.t_target);
9594f69966SJacob Pan controller_reset();
9694f69966SJacob Pan *yk = 0.0;
9794f69966SJacob Pan return;
9894f69966SJacob Pan }
9994f69966SJacob Pan /* compute intermediate PID terms */
10094f69966SJacob Pan p_term = -p_param.kp * (xk - xk_1);
10194f69966SJacob Pan i_term = p_param.kp * p_param.ki * p_param.ts * ek;
10294f69966SJacob Pan d_term = -p_param.kp * p_param.kd * (xk - 2 * xk_1 + xk_2) / p_param.ts;
10394f69966SJacob Pan /* compute output */
10494f69966SJacob Pan *yk += p_term + i_term + d_term;
10594f69966SJacob Pan /* update sample data */
10694f69966SJacob Pan xk_1 = xk;
10794f69966SJacob Pan xk_2 = xk_1;
10894f69966SJacob Pan
10994f69966SJacob Pan /* clamp output adjustment range */
11094f69966SJacob Pan if (*yk < -LIMIT_HIGH)
11194f69966SJacob Pan *yk = -LIMIT_HIGH;
11294f69966SJacob Pan else if (*yk > -LIMIT_LOW)
11394f69966SJacob Pan *yk = -LIMIT_LOW;
11494f69966SJacob Pan
11594f69966SJacob Pan p_param.y_k = *yk;
11694f69966SJacob Pan
11794f69966SJacob Pan set_ctrl_state(lround(fabs(p_param.y_k)));
11894f69966SJacob Pan
11994f69966SJacob Pan }
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