/* postrack.c */ /* asserv - Position & speed motor control on a ATmega128. {{{ * * Copyright (C) 2004 Nicolas Schodet * * Robot APB Team/Efrei 2005. * 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. * * }}} */ /** Current position, f24.8. */ int32_t postrack_x, postrack_y; /** Current angle, f8.24. */ int32_t postrack_a; /** Distance between the weels, u16. */ uint16_t postrack_footing; /** Precomputed footing factor, f8.24. * postrack_footing_factor = (1/2pi * 256) / postrack_footing * Explanations: * - Angles are between 0 and 1, corresponding to 0 and 2pi, therefore we * must divide by 2pi to convert unit (Arc=Angle * Radius only works for * radians). * - dd (see postrack_update) is in f11.16 format, we multiply by 256 to have * a angle in 8.24 format. * - this factor is in f8.24 format, therefore, 1 is writen (1L << 24). */ int32_t postrack_footing_factor; /* +AutoDec */ /** Initialise the position tracker. */ static inline void postrack_init (void); /** Update the current position. */ static inline void postrack_update (void); /** Change the footing value. */ static inline void postrack_set_footing (uint16_t footing); /* -AutoDec */ /** Initialise the position tracker. */ static inline void postrack_init (void) { postrack_set_footing (5142); } /** Update the current position. */ static inline void postrack_update (void) { int32_t d, dd, da, r, na; d = counter_right_diff + counter_left_diff; /* 10b */ d <<= 16; /* 10.16b */ d >>= 1; /* 9.16b */ if (counter_right_diff == counter_left_diff) { postrack_x += dsp_mul_f824 (d, dsp_cos (postrack_a)) >> 8; postrack_y += dsp_mul_f824 (d, dsp_sin (postrack_a)) >> 8; } else { dd = counter_right_diff - counter_left_diff; /* 11b */ dd <<= 16; /* 11.16b */ da = dsp_mul_f824 (dd, postrack_footing_factor); // XXX: WARNING ! could r overflow ? r = dsp_div_f824 (d, da); /* 16.16b */ na = postrack_a + da; postrack_x += dsp_mul_f824 (r, dsp_sin (na) - dsp_sin (postrack_a)) >> 8; postrack_y += dsp_mul_f824 (r, dsp_cos (postrack_a) - dsp_cos (na)) >> 8; postrack_a = na; postrack_a &= 0x00ffffff; } } #define M_1_PI 0.31830988618379067154 /* 1/pi */ /** Change the footing value. */ static inline void postrack_set_footing (uint16_t footing) { postrack_footing = footing; postrack_footing_factor = (int32_t) (0.5 * M_1_PI * (1L << 8) * (1L << 24)) / footing; }