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Diffstat (limited to 'tools/thermal/tmon/pid.c')
-rw-r--r-- | tools/thermal/tmon/pid.c | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/tools/thermal/tmon/pid.c b/tools/thermal/tmon/pid.c new file mode 100644 index 000000000..da2008828 --- /dev/null +++ b/tools/thermal/tmon/pid.c @@ -0,0 +1,119 @@ +// 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 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) +{ + + /* init pid params */ + p_param.ts = ticktime; + /* TODO: get it from TUI tuning tab */ + p_param.kp = .36; + p_param.ki = 5.0; + p_param.kd = 0.19; + + p_param.t_target = target_temp_user; + + return 0; +} + +void controller_reset(void) +{ + /* TODO: relax control data when not over thermal limit */ + syslog(LOG_DEBUG, "TC inactive, relax p-state\n"); + p_param.y_k = 0.0; + xk_1 = 0.0; + xk_2 = 0.0; + set_ctrl_state(0); +} + +/* To be called at time interval Ts. Type C PID controller. + * 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 + * TODO: add low pass filter for D term + */ +#define GUARD_BAND (2) +void controller_handler(const double xk, double *yk) +{ + double ek; + double p_term, i_term, d_term; + + ek = p_param.t_target - xk; /* error */ + if (ek >= 3.0) { + syslog(LOG_DEBUG, "PID: %3.1f Below set point %3.1f, stop\n", + xk, p_param.t_target); + controller_reset(); + *yk = 0.0; + return; + } + /* compute intermediate PID terms */ + p_term = -p_param.kp * (xk - xk_1); + i_term = p_param.kp * p_param.ki * p_param.ts * ek; + d_term = -p_param.kp * p_param.kd * (xk - 2 * xk_1 + xk_2) / p_param.ts; + /* compute output */ + *yk += p_term + i_term + d_term; + /* update sample data */ + xk_1 = xk; + xk_2 = xk_1; + + /* clamp output adjustment range */ + if (*yk < -LIMIT_HIGH) + *yk = -LIMIT_HIGH; + else if (*yk > -LIMIT_LOW) + *yk = -LIMIT_LOW; + + p_param.y_k = *yk; + + set_ctrl_state(lround(fabs(p_param.y_k))); + +} |