blob: c54edb4f630cffe8fa0896005761a1fdbcc19855 [file] [log] [blame]
 // 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 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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; p_param.kd = 0.19; p_param.t_target = target_temp_user; return ret; } 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))); }