/* pos.c - Position motor control. */ /* asserv - Position & speed motor control on AVR. {{{ * * Copyright (C) 2005 Nicolas Schodet * * Robot APB Team/Efrei 2006. * Web: http://assos.efrei.fr/robot/ * Email: robot AT efrei DOT fr * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * }}} */ /** * This file is responsible for position motor control. The consign is a * position of the motor shafts, as theta/alpha. Theta is the sum of right * and left position, alpha is the difference between the right and the left * position. * 16 bits are enough as long as there is no long blocking (see 2005 cup!). */ /** Current theta/alpha. */ uint32_t pos_theta_cur, pos_alpha_cur; /** Consign theta/alpha. */ uint32_t pos_theta_cons, pos_alpha_cons; /** Error saturation. */ int32_t pos_e_sat = 1023; /** Integral saturation. */ int32_t pos_int_sat = 1023; /** P coefficients. */ uint16_t pos_theta_kp, pos_alpha_kp; /** I coefficients. */ uint16_t pos_theta_ki, pos_alpha_ki; /** D coefficients. */ uint16_t pos_theta_kd, pos_alpha_kd; /** Blocked value. If error is greater than this value, stop the robot and * report blocked state. */ int32_t pos_blocked = 15000L; /** Current integral values. */ int32_t pos_theta_int, pos_alpha_int; /** Last error values. */ int32_t pos_theta_e_old, pos_alpha_e_old; /** One if blocked. */ uint8_t pos_blocked_state; /* +AutoDec */ /* -AutoDec */ /** Compute a PID. * How to compute maximum numbers size: * Result is 24 bits (16 bits kept after shift). * If e_sat == 1023, e max is 11 bits (do not forget the sign bit), and diff * max is 12 bits. * If int_sat == 1023, i max is 11 bits. * In the final addition, let's give 23 bits to the p part, and 22 bits to the * i and d part (23b + 22b + 22b => 23b + 23b => 24b). * Therefore, kp can be 23 - 11 = 12 bits (f4.8). * ki can be 22 - 11 = 11 bits (f3.8). * kd can be 22 - 12 = 10 bits (f2.8). * How to increase this number: * - lower the shift. * - bound the value returned. * - lower e & int saturation. */ static inline int16_t pos_compute_pid (int32_t e, int32_t *i, int32_t *e_old, uint16_t kp, uint16_t ki, uint16_t kd) { int32_t diff, pid; /* Saturate error. */ UTILS_BOUND (e, -pos_e_sat, pos_e_sat); /* Integral update. */ *i += e; UTILS_BOUND (*i, -pos_int_sat, pos_int_sat); /* Differential value. */ diff = e - *e_old; /* Compute PID. */ pid = e * kp + *i * ki + diff * kd; /* Save result. */ *e_old = e; return pid >> 8; } /** Update PWM according to consign. */ static void pos_update (void) { int16_t pid_theta, pid_alpha; int32_t diff_theta, diff_alpha; /* Update current shaft positions. */ pos_theta_cur += counter_left_diff + counter_right_diff; pos_alpha_cur += counter_right_diff - counter_left_diff; /* Compute PID. */ diff_theta = pos_theta_cons - pos_theta_cur; diff_alpha = pos_alpha_cons - pos_alpha_cur; if (pos_blocked_state || diff_theta < -pos_blocked || pos_blocked < diff_theta || diff_alpha < -pos_blocked || pos_blocked < diff_alpha) { /* Blocked. */ pwm_left = 0; pwm_right = 0; pos_blocked_state = 1; main_sequence_finish = main_sequence | 0x80; } else { pid_theta = pos_compute_pid (diff_theta, &pos_theta_int, &pos_theta_e_old, pos_theta_kp, pos_theta_ki, pos_theta_kd); pid_alpha = pos_compute_pid (diff_alpha, &pos_alpha_int, &pos_alpha_e_old, pos_alpha_kp, pos_alpha_ki, pos_alpha_kd); /* Update PWM. */ pwm_left = pid_theta - pid_alpha; UTILS_BOUND (pwm_left, -PWM_MAX, PWM_MAX); pwm_right = pid_theta + pid_alpha; UTILS_BOUND (pwm_right, -PWM_MAX, PWM_MAX); } } /** Reset position control internal state. */ static void pos_reset (void) { pos_theta_int = pos_alpha_int = 0; pos_theta_cur = pos_alpha_cur = 0; pos_theta_cons = pos_alpha_cons = 0; pos_theta_e_old = pos_alpha_e_old = 0; pos_blocked_state = 0; }