mirror of https://github.com/ArduPilot/ardupilot
63 lines
1.7 KiB
C++
63 lines
1.7 KiB
C++
/*
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polynomial fitting class, originally written by Siddharth Bharat Purohit
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re-worked for ArduPilot by Andrew Tridgell
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*/
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#include "polyfit.h"
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#include "AP_Math.h"
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#include "vector3.h"
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template <uint8_t order, typename xtype, typename vtype>
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void PolyFit<order,xtype,vtype>::update(xtype x, vtype y)
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{
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xtype temp = 1;
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for (int8_t i = 2*(order-1); i >= 0; i--) {
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int8_t k = (i<order)?0:i - order + 1;
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for (int8_t j = i - k; j >= k; j--) {
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mat[j][i-j] += temp;
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}
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temp *= x;
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}
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temp = 1;
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for (int8_t i = order-1; i >= 0; i--) {
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vec[i] += y * temp;
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temp *= x;
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}
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}
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template <uint8_t order, typename xtype, typename vtype>
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bool PolyFit<order,xtype,vtype>::get_polynomial(vtype res[order]) const
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{
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// we dynamically allocate the inverse matrix to keep stack usage low
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xtype *inv_mat = NEW_NOTHROW xtype[order*order];
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if (inv_mat == nullptr) {
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return false;
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}
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if (!mat_inverse(&mat[0][0], inv_mat, order)) {
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delete[] inv_mat;
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return false;
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}
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// the summation must be done with double precision to get
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// good accuracy
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Vector3d resd[order] {};
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for (uint8_t i = 0; i < order; i++) {
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for (uint8_t j = 0; j < order; j++) {
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resd[i].x += vec[j].x * inv_mat[i*order+j];
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resd[i].y += vec[j].y * inv_mat[i*order+j];
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resd[i].z += vec[j].z * inv_mat[i*order+j];
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}
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}
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for (uint8_t j = 0; j < order; j++) {
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res[j].x = resd[j].x;
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res[j].y = resd[j].y;
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res[j].z = resd[j].z;
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}
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delete[] inv_mat;
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return true;
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}
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// instantiate for order 4 double with Vector3f
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template class PolyFit<4, double, Vector3f>;
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