158 lines
5.4 KiB
C++
158 lines
5.4 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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#include <FastSerial.h>
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#include <ThirdOrderCompFilter.h>
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#if defined(ARDUINO) && ARDUINO >= 100
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#include "Arduino.h"
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#else
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#include <wiring.h>
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#endif
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// Public Methods //////////////////////////////////////////////////////////////
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// update_gains - update gains from time constant (given in seconds)
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void ThirdOrderCompFilter::update_gains(float time_constant_seconds_xy, float time_constant_seconds_z)
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{
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static float last_time_constant_xy = 0;
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static float last_time_constant_z = 0;
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// X & Y axis time constant
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if( time_constant_seconds_xy == 0 ) {
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_k1_xy = _k2_xy = _k3_xy = 0;
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}else{
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if( time_constant_seconds_xy != last_time_constant_xy ) {
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_k1_xy = 3 / time_constant_seconds_xy;
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_k2_xy = 3 / (time_constant_seconds_xy*time_constant_seconds_xy);
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_k3_xy = 1 / (time_constant_seconds_xy*time_constant_seconds_xy*time_constant_seconds_xy);
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last_time_constant_xy = time_constant_seconds_xy;
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}
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}
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// Z axis time constant
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if( time_constant_seconds_z == 0 ) {
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_k1_z = _k2_z = _k3_z = 0;
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}else{
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if( time_constant_seconds_z != last_time_constant_z ) {
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_k1_z = 3 / time_constant_seconds_z;
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_k2_z = 3 / (time_constant_seconds_z*time_constant_seconds_z);
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_k3_z = 1 / (time_constant_seconds_z*time_constant_seconds_z*time_constant_seconds_z);
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last_time_constant_z = time_constant_seconds_z;
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}
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}
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}
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// set_3rd_order - resets the first order value (i.e. position)
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void ThirdOrderCompFilter::set_3rd_order_xy(float x, float y)
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{
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_comp_h.x = x;
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_comp_h.y = y;
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_comp_h_correction.x = 0;
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_comp_h_correction.y = 0;
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// clear historic estimates
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_hist_3rd_order_estimates_x.clear();
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_hist_3rd_order_estimates_y.clear();
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}
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// set_3rd_order - resets the first order value (i.e. position)
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void ThirdOrderCompFilter::set_3rd_order_z(float z )
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{
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_comp_h.z = z;
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_comp_h_correction.z = 0;
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}
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// set_2nd_order - resets the second order value (i.e. velocity)
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void ThirdOrderCompFilter::set_2nd_order_xy(float x, float y)
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{
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_comp_v.x = x;
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_comp_v.y = y;
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}
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// set_2nd_order - resets the second order value (i.e. velocity)
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void ThirdOrderCompFilter::set_2nd_order_z(float z )
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{
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_comp_v.z = z;
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}
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// correct_3rd_order_z - correct accelerometer offsets using barometer or gps
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void ThirdOrderCompFilter::correct_3rd_order_xy(float x, float y, Matrix3f& dcm_matrix, float deltat)
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{
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float hist_comp_h_x, hist_comp_h_y;
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// 3rd order samples (i.e. position from gps) are delayed by 500ms
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// we store historical position at 10hz so 5 iterations ago
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if( _hist_3rd_order_estimates_x.num_items() >= 4 ) {
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hist_comp_h_x = _hist_3rd_order_estimates_x.peek(3);
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hist_comp_h_y = _hist_3rd_order_estimates_y.peek(3);
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}else{
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hist_comp_h_x = _comp_h.x;
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hist_comp_h_y = _comp_h.y;
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}
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// calculate error in position from gps with our historical estimate
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float err_x = x - (hist_comp_h_x + _comp_h_correction.x);
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float err_y = y - (hist_comp_h_y + _comp_h_correction.y);
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// calculate correction to accelerometers and apply in the body frame
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_comp_k1o += dcm_matrix.mul_transpose(Vector3f((err_x*_k3_xy)*deltat,(err_y*_k3_xy)*deltat,0));
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// correct velocity
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_comp_v.x += (err_x*_k2_xy) * deltat;
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_comp_v.y += (err_y*_k2_xy) * deltat;
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// correct position
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_comp_h_correction.x += err_x*_k1_xy * deltat;
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_comp_h_correction.y += err_y*_k1_xy * deltat;
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}
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// correct_3rd_order_z - correct accelerometer offsets using barometer or gps
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void ThirdOrderCompFilter::correct_3rd_order_z(float third_order_sample, Matrix3f& dcm_matrix, float deltat)
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{
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float hist_comp_h_z;
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// 3rd order samples (i.e. position from baro) are delayed by 150ms (15 iterations at 100hz)
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// so we should calculate error using historical estimates
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if( _hist_3rd_order_estimates_z.num_items() >= 15 ) {
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//hist_comp_h_z = _hist_3rd_order_estimates_z.get();
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hist_comp_h_z = _hist_3rd_order_estimates_z.peek(14);
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}else{
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hist_comp_h_z = _comp_h.z;
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}
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// calculate error in position from baro with our estimate
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float err = third_order_sample - (hist_comp_h_z + _comp_h_correction.z);
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// calculate correction to accelerometers and apply in the body frame
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_comp_k1o += dcm_matrix.mul_transpose(Vector3f(0,0,(err*_k3_z) * deltat));
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// correct velocity
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_comp_v.z += (err*_k2_z) * deltat;
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// correct position
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_comp_h_correction.z += err*_k1_z * deltat;
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}
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// recalculate the 2nd and 3rd order estimates
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void ThirdOrderCompFilter::calculate(float deltat, Matrix3f& dcm_matrix)
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{
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// get earth frame accelerometer correction
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comp_k1o_ef = dcm_matrix * _comp_k1o;
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// calculate velocity by adding new acceleration from accelerometers
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_comp_v += (-_first_order_sample + comp_k1o_ef) * deltat;
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// calculate new estimate of position
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_comp_h += _comp_v * deltat;
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// store 3rd order estimate (i.e. estimated vertical position) for future use
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_hist_3rd_order_estimates_z.add(_comp_h.z);
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// store 3rd order estimate (i.e. horizontal position) for future use at 10hz
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_historic_xy_counter++;
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if( _historic_xy_counter >= THIRD_ORDER_SAVE_POS_10HZ ) {
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_historic_xy_counter = 0;
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_hist_3rd_order_estimates_x.add(_comp_h.x);
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_hist_3rd_order_estimates_y.add(_comp_h.y);
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}
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}
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