linux-imx

// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * pid.c PID controller for testing cooling devices

 *

 * Copyright (C) 2012 Intel Corporation. All rights reserved.

 *

 * Author Name Jacob Pan <jacob.jun.pan@linux.intel.com>

 */

​

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <stdint.h>

#include <sys/types.h>

#include <dirent.h>

#include <libintl.h>

#include <ctype.h>

#include <assert.h>

#include <time.h>

#include <limits.h>

#include <math.h>

#include <sys/stat.h>

#include <syslog.h>

​

#include "tmon.h"

​

/**************************************************************************

 * PID (Proportional-Integral-Derivative) controller is commonly used in

 * linear control system, consider the the process.

 * G(s) = U(s)/E(s)

 * kp = proportional gain

 * ki = integral gain

 * kd = derivative gain

 * Ts

 * We use type C Alan Bradley equation which takes set point off the

 * output dependency in P and D term.

 *

 *   y[k] = y[k-1] - kp*(x[k] - x[k-1]) + Ki*Ts*e[k] - Kd*(x[k]

 *          - 2*x[k-1]+x[k-2])/Ts

 *

 *

 ***********************************************************************/

struct pid_params p_param;

/* cached data from previous loop */

static double xk_1, xk_2; /* input temperature x[k-#] */

​

/*

 * TODO: make PID parameters tuned automatically,

 * 1. use CPU burn to produce open loop unit step response

 * 2. calculate PID based on Ziegler-Nichols rule

 *

 * add a flag for tuning PID

 */

int init_thermal_controller(void)

{

    int ret = 0;

​

    /* init pid params */

    p_param.ts = ticktime;

    /* TODO: get it from TUI tuning tab */

    p_param.kp = .36;

    p_param.ki = 5.0;