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Diffstat (limited to 'src/lingot-gauge.c')
| -rw-r--r-- | src/lingot-gauge.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/src/lingot-gauge.c b/src/lingot-gauge.c new file mode 100644 index 0000000..4e5a17f --- /dev/null +++ b/src/lingot-gauge.c @@ -0,0 +1,91 @@ +/* + * lingot, a musical instrument tuner. + * + * Copyright (C) 2004-2011 Ibán Cereijo Graña, Jairo Chapela Martínez. + * + * This file is part of lingot. + * + * lingot 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. + * + * lingot 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 lingot; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include "lingot-gauge.h" + +LingotGauge* lingot_gauge_new(FLT initial_position) + { + + // + // ----- ERROR GAUGE FILTER CONFIGURATION ----- + // + // dynamic model of the gauge: + // + // 2 + // d d + // --- s(t) = k (e(t) - s(t)) - q -- s(t) + // 2 dt + // dt + // + // acceleration of gauge position 's(t)' linealy depends on the difference + // respect to the input stimulus 'e(t)' (destination position). Inserting + // a friction coefficient 'q', acceleration proportionaly diminish with + // velocity (typical friction in mechanics). 'k' is the adaptation constant, + // and depends on the gauge mass. + // + // with the following derivatives approximation (valid for high sample rate): + // + // d + // -- s(t) ~= (s[n] - s[n - 1])*fs + // dt + // + // 2 + // d 2 + // --- s(t) ~= (s[n] - 2*s[n - 1] + s[n - 2])*fs + // 2 + // dt + // + // we can obtain a difference equation, and implement it with an IIR digital + // filter. + // + + FLT k = 60; + // adaptation constant. + FLT q = 6; + // friction coefficient. + + FLT a[] = + { + k + GAUGE_RATE*(q + GAUGE_RATE), + -GAUGE_RATE*(q + 2.0*GAUGE_RATE), + GAUGE_RATE*GAUGE_RATE}; + FLT b[] = + { k}; + + LingotGauge* gauge = malloc(sizeof(LingotGauge)); + + gauge->filter = lingot_filter_new( 2, 0, a, b ); + lingot_gauge_compute(gauge, initial_position); + return gauge; + } + +void lingot_gauge_destroy(LingotGauge* gauge) + { + lingot_filter_destroy(gauge->filter); + free(gauge); + } + +void lingot_gauge_compute(LingotGauge* gauge, FLT sample) + { + gauge->position = lingot_filter_filter_sample(gauge->filter, sample); + } + |