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| author | Kevin O'Connor <kevin@koconnor.net> | 2020-10-23 22:59:20 -0400 |
|---|---|---|
| committer | Kevin O'Connor <kevin@koconnor.net> | 2020-10-23 22:59:20 -0400 |
| commit | 1b6b7fc58c5037256f9d0935c94916a51bdfd6b3 (patch) | |
| tree | 1018123fc2339fc209b592111f220ed22a7c3deb | |
| parent | 2bcf06a295e5c9696b1bf556a0520b49957a369f (diff) | |
| download | kutter-1b6b7fc58c5037256f9d0935c94916a51bdfd6b3.tar.gz kutter-1b6b7fc58c5037256f9d0935c94916a51bdfd6b3.tar.xz kutter-1b6b7fc58c5037256f9d0935c94916a51bdfd6b3.zip | |
kin_extruder: Fix numerical stability when using pressure advance
Avoid using the absolute E position when calculating pressure advance
as that position can grow arbitrarily large, which can result in
"numerical stability" problems. That instability could eventually
lead to internal errors during step compression.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
| -rw-r--r-- | klippy/chelper/kin_extruder.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/klippy/chelper/kin_extruder.c b/klippy/chelper/kin_extruder.c index 2fce006b..63dca909 100644 --- a/klippy/chelper/kin_extruder.c +++ b/klippy/chelper/kin_extruder.c @@ -52,7 +52,8 @@ extruder_integrate_time(double base, double start_v, double half_accel // Calculate the definitive integral of extruder for a given move static double -pa_move_integrate(struct move *m, double start, double end, double time_offset) +pa_move_integrate(struct move *m, double base, double start, double end, + double time_offset) { if (start < 0.) start = 0.; @@ -60,7 +61,7 @@ pa_move_integrate(struct move *m, double start, double end, double time_offset) end = m->move_t; // Calculate base position and velocity with pressure advance double pressure_advance = m->axes_r.y; - double base = m->start_pos.x + pressure_advance * m->start_v; + base += pressure_advance * m->start_v; double start_v = m->start_v + pressure_advance * 2. * m->half_accel; // Calculate definitive integral double ha = m->half_accel; @@ -75,20 +76,23 @@ pa_range_integrate(struct move *m, double move_time, double hst) { // Calculate integral for the current move double res = 0., start = move_time - hst, end = move_time + hst; - res += pa_move_integrate(m, start, move_time, start); - res -= pa_move_integrate(m, move_time, end, end); + double start_base = m->start_pos.x; + res += pa_move_integrate(m, 0., start, move_time, start); + res -= pa_move_integrate(m, 0., move_time, end, end); // Integrate over previous moves struct move *prev = m; while (unlikely(start < 0.)) { prev = list_prev_entry(prev, node); start += prev->move_t; - res += pa_move_integrate(prev, start, prev->move_t, start); + double base = prev->start_pos.x - start_base; + res += pa_move_integrate(prev, base, start, prev->move_t, start); } // Integrate over future moves while (unlikely(end > m->move_t)) { end -= m->move_t; m = list_next_entry(m, node); - res -= pa_move_integrate(m, 0., end, end); + double base = m->start_pos.x - start_base; + res -= pa_move_integrate(m, base, 0., end, end); } return res; } @@ -109,7 +113,7 @@ extruder_calc_position(struct stepper_kinematics *sk, struct move *m return m->start_pos.x + move_get_distance(m, move_time); // Apply pressure advance and average over smooth_time double area = pa_range_integrate(m, move_time, hst); - return area * es->inv_half_smooth_time2; + return m->start_pos.x + area * es->inv_half_smooth_time2; } void __visible |