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trapq: Limit the duration of "null" sentinal moves on the trapq 

If a null move is added as the first move on the trapezoid motion
queue then it could have a very large move->move_t value.  This could
cause numerical stability issues with some advanced kinematic
formulas.  Place a limit on the move_t value to avoid this.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2019-12-14 10:26:23 -05:00
parent b921b8a1c1
commit 54149e38f9
1 changed files with 7 additions and 1 deletions
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8
klippy/chelper/trapq.c
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@ -133,6 +133,8 @@ trapq_check_sentinels(struct trapq *tq)
tail_sentinel->start_pos = move_get_coord(m, m->move_t);
}
#define MAX_NULL_MOVE 1.0
// Add a move to the trapezoid velocity queue
void
trapq_add_move(struct trapq *tq, struct move *m)
@ -143,7 +145,11 @@ trapq_add_move(struct trapq *tq, struct move *m)
// Add a null move to fill time gap
struct move *null_move = move_alloc();
null_move->start_pos = m->start_pos;
null_move->print_time = prev->print_time + prev->move_t;
if (!prev->print_time && m->print_time > MAX_NULL_MOVE)
// Limit the first null move to improve numerical stability
null_move->print_time = m->print_time - MAX_NULL_MOVE;
else
null_move->print_time = prev->print_time + prev->move_t;
null_move->move_t = m->print_time - null_move->print_time;
list_add_before(&null_move->node, &tail_sentinel->node);
}