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Lookahead: refactored code to compute everything in dda steps.

This commit is contained in:
Roland Brochard 2013-09-10 23:03:47 +02:00 committed by Markus Hitter
parent 20686eb52c
commit 297aa28dfd
3 changed files with 82 additions and 185 deletions
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2
dda.c
View File

@ -132,9 +132,7 @@ void dda_create(DDA *dda, TARGET *target) {
// Set the start and stop speeds to zero for now = full stops between // Set the start and stop speeds to zero for now = full stops between
// moves. Also fallback if lookahead calculations fail to finish in time. // moves. Also fallback if lookahead calculations fail to finish in time.
dda->crossF = 0; dda->crossF = 0;
dda->F_start = 0;
dda->start_steps = 0; dda->start_steps = 0;
dda->F_end = 0;
dda->end_steps = 0; dda->end_steps = 0;
// Give this move an identifier. // Give this move an identifier.
dda->id = idcnt++; dda->id = idcnt++;

2
dda.h
View File

@ -150,9 +150,7 @@ typedef struct {
uint32_t distance; uint32_t distance;
uint32_t crossF; uint32_t crossF;
// These two are based on the "fast" axis, the axis with the most steps. // These two are based on the "fast" axis, the axis with the most steps.
uint32_t F_start;
uint32_t start_steps; ///< would be required to reach start feedrate uint32_t start_steps; ///< would be required to reach start feedrate
uint32_t F_end;
uint32_t end_steps; ///< would be required to stop from end feedrate uint32_t end_steps; ///< would be required to stop from end feedrate
// Displacement vector, in um, based between the difference of the starting // Displacement vector, in um, based between the difference of the starting
// point and the target. Required to obtain the jerk between 2 moves. // point and the target. Required to obtain the jerk between 2 moves.

263
dda_lookahead.c
View File

@ -41,7 +41,7 @@ uint32_t lookahead_timeout = 0; // Moves that did not compute in time to be
#endif #endif
// We also need the inverse: given a ramp length, determine the expected speed // We also need the inverse: given a ramp length, determine the expected speed
// Note: the calculation is scaled by a factor 10000 to obtain an answer with a smaller // Note: the calculation is scaled by a factor 16384 to obtain an answer with a smaller
// rounding error. // rounding error.
// Warning: this is an expensive function as it requires a square root to get the result. // Warning: this is an expensive function as it requires a square root to get the result.
// //
@ -53,9 +53,9 @@ uint32_t dda_steps_to_velocity(uint32_t steps) {
// F_steps = sqrt((2000*a)/STEPS_PER_M_X) * 60 * sqrt(steps) // F_steps = sqrt((2000*a)/STEPS_PER_M_X) * 60 * sqrt(steps)
static uint32_t part = 0; static uint32_t part = 0;
if(part == 0) if(part == 0)
part = int_sqrt((uint32_t)((2000.0f*ACCELERATION*3600.0f*10000.0f)/(float)STEPS_PER_M_X)); part = (uint32_t)sqrtf((2000.0f*3600.0f*ACCELERATION*16384.0f)/(float)STEPS_PER_M_X);
uint32_t res = int_sqrt((steps) * 10000) * part; uint32_t res = int_sqrt((steps) << 14) * part;
return res / 10000; return res >> 14;
} }
/** /**
@ -69,7 +69,7 @@ uint32_t dda_steps_to_velocity(uint32_t steps) {
* @param F2 feed rate of second move * @param F2 feed rate of second move
*/ */
int dda_jerk_size_2d_real(int32_t x1, int32_t y1, uint32_t F1, int32_t x2, int32_t y2, uint32_t F2) { int dda_jerk_size_2d_real(int32_t x1, int32_t y1, uint32_t F1, int32_t x2, int32_t y2, uint32_t F2) {
const int maxlen = 10000; const int maxlen = 16384;
// Normalize vectors so their length will be fixed // Normalize vectors so their length will be fixed
// Note: approx_distance is not precise enough and may result in violent direction changes // Note: approx_distance is not precise enough and may result in violent direction changes
//sersendf_P(PSTR("Input vectors: (%ld, %ld) and (%ld, %ld)\r\n"),x1,y1,x2,y2); //sersendf_P(PSTR("Input vectors: (%ld, %ld) and (%ld, %ld)\r\n"),x1,y1,x2,y2);
@ -302,15 +302,16 @@ void dda_join_moves(DDA *prev, DDA *current) {
// Calculating the look-ahead settings can take a while; before modifying // Calculating the look-ahead settings can take a while; before modifying
// the previous move, we need to locally store any values and write them // the previous move, we need to locally store any values and write them
// when we are done (and the previous move is not already active). // when we are done (and the previous move is not already active).
uint32_t prev_F, prev_F_start, prev_F_end, prev_end; uint32_t prev_F, prev_F_in_steps, prev_F_start_in_steps, prev_F_end_in_steps;
uint32_t prev_rampup, prev_rampdown, prev_total_steps; uint32_t prev_rampup, prev_rampdown, prev_total_steps;
uint32_t crossF, currF; uint32_t crossF, crossF_in_steps;
uint8_t prev_id; uint8_t prev_id;
// Similarly, we only want to modify the current move if we have the results of the calculations; // Similarly, we only want to modify the current move if we have the results of the calculations;
// until then, we do not want to touch the current move settings. // until then, we do not want to touch the current move settings.
// Note: we assume 'current' will not be dispatched while this function runs, so we do not to // Note: we assume 'current' will not be dispatched while this function runs, so we do not to
// back up the move settings: they will remain constant. // back up the move settings: they will remain constant.
uint32_t this_F_start, this_start, this_rampup, this_rampdown; uint32_t this_F, this_F_in_steps, this_F_start_in_steps, this_rampup, this_rampdown, this_total_steps;
uint8_t this_id;
static uint32_t la_cnt = 0; // Counter: how many moves did we join? static uint32_t la_cnt = 0; // Counter: how many moves did we join?
#ifdef LOOKAHEAD_DEBUG #ifdef LOOKAHEAD_DEBUG
static uint32_t moveno = 0; // Debug counter to number the moves - helps while debugging static uint32_t moveno = 0; // Debug counter to number the moves - helps while debugging
@ -321,25 +322,32 @@ void dda_join_moves(DDA *prev, DDA *current) {
if ( ! prev || prev->nullmove || current->crossF == 0) if ( ! prev || prev->nullmove || current->crossF == 0)
return; return;
// Show the proposed crossing speed - this might get adjusted below.
if (DEBUG_DDA && (debug_flags & DEBUG_DDA))
sersendf_P(PSTR("Initial crossing speed: %lu\n"), crossF);
// Make sure we have 2 moves and the previous move is not already active // Make sure we have 2 moves and the previous move is not already active
if (prev->live == 0) { if (prev->live == 0) {
// Perform an atomic copy to preserve volatile parameters during the calculations // Perform an atomic copy to preserve volatile parameters during the calculations
ATOMIC_START ATOMIC_START
prev_id = prev->id; prev_id = prev->id;
prev_F = prev->endpoint.F; prev_F = prev->endpoint.F;
prev_F_start = prev->F_start; prev_F_start_in_steps = prev->start_steps;
prev_F_end = prev->F_end; prev_F_end_in_steps = prev->end_steps;
prev_rampup = prev->rampup_steps; prev_rampup = prev->rampup_steps;
prev_rampdown = prev->rampdown_steps; prev_rampdown = prev->rampdown_steps;
prev_total_steps = prev->total_steps; prev_total_steps = prev->total_steps;
crossF = current->crossF; crossF = current->crossF;
this_id = current->id;
this_F = current->endpoint.F;
this_total_steps = current->total_steps;
ATOMIC_END ATOMIC_END
// Here we have to distinguish between feedrate along the movement // Here we have to distinguish between feedrate along the movement
// direction and feedrate of the fast axis. They can differ by a factor // direction and feedrate of the fast axis. They can differ by a factor
// of 2. // of 2.
// Along direction: F, crossF. // Along direction: F, crossF.
// Fast axis already: F_start, F_end. // Along fast axis already: start_steps, end_steps.
// //
// All calculations here are done along the fast axis, so recalculate // All calculations here are done along the fast axis, so recalculate
// F and crossF to match this, too. // F and crossF to match this, too.
@ -374,185 +382,81 @@ void dda_join_moves(DDA *prev, DDA *current) {
sersendf_P(PSTR("WTF? No current fast axis found\n")); sersendf_P(PSTR("WTF? No current fast axis found\n"));
} }
crossF = muldiv(fast_um, crossF, current->distance); crossF = muldiv(fast_um, crossF, current->distance);
currF = muldiv(fast_um, current->endpoint.F, current->distance); this_F = muldiv(fast_um, current->endpoint.F, current->distance);
prev_F_in_steps = ACCELERATE_RAMP_LEN(prev_F);
this_F_in_steps = ACCELERATE_RAMP_LEN(this_F);
crossF_in_steps = ACCELERATE_RAMP_LEN(crossF);
// Show the proposed crossing speed - this might get adjusted below // Show the proposed crossing speed - this might get adjusted below
if (DEBUG_DDA && (debug_flags & DEBUG_DDA)) serprintf(PSTR("Initial crossing speed: %lu\r\n"), crossF_in_steps);
sersendf_P(PSTR("Initial crossing speed: %lu\n"), crossF);
// Forward check: test if we can actually reach the target speed in the previous move // Compute the maximum speed we can reach for crossing.
// If not: we need to determine the obtainable speed and adjust crossF accordingly. crossF_in_steps = MIN(crossF_in_steps, this_total_steps);
// Note: these ramps can be longer than the move: if so we can not reach top speed. crossF_in_steps = MIN(crossF_in_steps, prev_total_steps + prev_F_start_in_steps);
uint32_t up = ACCELERATE_RAMP_LEN(prev_F) - ACCELERATE_RAMP_LEN(prev_F_start);
uint32_t down = ACCELERATE_RAMP_LEN(prev_F) - ACCELERATE_RAMP_LEN(crossF);
// Test if both the ramp up and ramp down fit within the move
if(up+down > prev_total_steps) {
// Test if we can reach the crossF rate: if the difference between both ramps is larger
// than the move itself, there is no ramp up or down from F_start to crossF...
uint32_t diff = (up>down) ? up-down : down-up;
if(diff > prev_total_steps) {
// Cannot reach crossF from F_start, lower crossF and adjust both ramp-up and down
down = 0;
// Before we can determine how fast we can go in this move, we need the number of
// steps needed to reach the entry speed.
uint32_t prestep = ACCELERATE_RAMP_LEN(prev_F_start);
// Calculate what feed rate we can reach during this move
crossF = dda_steps_to_velocity(prestep+prev_total_steps);
// Make sure we do not exceed the target speeds
if(crossF > prev_F) crossF = prev_F;
if(crossF > currF) crossF = currF;
// The problem with the 'dda_steps_to_velocity' is that it will produce a
// rounded result. Use it to obtain an exact amount of steps needed to reach
// that speed and set that as the ramp up; we might stop accelerating for a
// couple of steps but that is better than introducing errors in the moves.
up = ACCELERATE_RAMP_LEN(crossF) - prestep;
#ifdef LOOKAHEAD_DEBUG if (crossF_in_steps == 0)
// Sanity check: the ramp up should never exceed the move length return;
if(up > prev_total_steps) {
sersendf_P(PSTR("FATAL ERROR during prev ramp scale, ramp is too long: up:%lu ; len:%lu ; target speed: %lu\r\n"),
up, prev_total_steps, crossF);
sersendf_P(PSTR("F_start:%lu ; F:%lu ; crossF:%lu\r\n"),
prev_F_start, prev_F, crossF);
dda_emergency_shutdown(PSTR("LA prev ramp scale, ramp is too long"));
}
#endif
// Show the result on the speed on the clipping of the ramp
serprintf(PSTR("Prev speed & crossing speed truncated to: %lu\r\n"), crossF);
} else {
// Can reach crossF; determine the apex between ramp up and ramp down
// In other words: calculate how long we can accelerate before decelerating to exit at crossF
// Note: while the number of steps is exponentially proportional to the velocity,
// the acceleration is linear: we can simply remove the same number of steps of both ramps.
uint32_t diff = (up + down - prev_total_steps) / 2;
up -= diff;
down -= diff;
}
#ifdef LOOKAHEAD_DEBUG // Build ramps for previous move.
// Sanity check: make sure the speed limits are maintained if (crossF_in_steps == prev_F_in_steps) {
if(prev_F_start > prev_F || crossF > prev_F) { prev_rampup = prev_F_in_steps - prev_F_start_in_steps;
serprintf(PSTR("Prev target speed exceeded!: prev_F_start:%lu ; prev_F:%lu ; prev_F_end:%lu\r\n"), prev_F_start, prev_F, crossF); prev_rampdown = 0;
dda_emergency_shutdown(PSTR("Prev target speed exceeded"));
}
#endif
} }
// Save the results else if (crossF_in_steps < prev_F_start_in_steps) {
prev_rampup = up; uint32_t extra, limit;
prev_rampdown = prev_total_steps - down;
prev_F_end = crossF;
prev_end = ACCELERATE_RAMP_LEN(prev_F_end);
#ifdef LOOKAHEAD_DEBUG prev_rampup = 0;
// Sanity check: make sure the speed limits are maintained prev_rampdown = prev_F_start_in_steps - crossF_in_steps;
if(crossF > currF) { extra = (prev_total_steps - prev_rampdown) >> 1;
serprintf(PSTR("This target speed exceeded!: F_start:%lu ; F:%lu ; prev_F_end:%lu\r\n"), crossF, currF); limit = prev_F_in_steps - prev_F_start_in_steps;
dda_emergency_shutdown(PSTR("This target speed exceeded")); extra = MIN(extra, limit);
prev_rampup += extra;
prev_rampdown += extra;
} }
#endif else {
uint32_t extra, limit;
// Forward check 2: test if we can actually reach the target speed in this move. prev_rampup = crossF_in_steps - prev_F_start_in_steps;
// If not: determine obtainable speed and adjust crossF accordingly. If that prev_rampdown = 0;
// happens, a third (reverse) pass is needed to lower the speeds in the previous move... extra = (prev_total_steps - prev_rampup) >> 1;
//ramp_scaler = ACCELERATE_SCALER(current->lead); // Use scaler for current leading axis limit = prev_F_in_steps - crossF_in_steps;
up = ACCELERATE_RAMP_LEN(currF) - ACCELERATE_RAMP_LEN(crossF); extra = MIN(extra, limit);
down = ACCELERATE_RAMP_LEN(currF);
// Test if both the ramp up and ramp down fit within the move
if(up+down > current->total_steps) {
// Test if we can reach the crossF rate
// Note: this is the inverse of the previous move: we need to exit at 0 speed as
// this is the last move in the queue. Implies that down >= up
if(down-up > current->total_steps) {
serprintf(PSTR("This move can not reach crossF - lower it\r\n"));
// Cannot reach crossF, lower it and adjust ramps
// Note: after this, the previous move needs to be modified to match crossF.
up = 0;
// Calculate what crossing rate we can reach: total/down * F
crossF = dda_steps_to_velocity(current->total_steps);
// Speed limit: never exceed the target rate
if(crossF > currF) crossF = currF;
// crossF will be conservative: calculate the actual ramp down length
down = ACCELERATE_RAMP_LEN(crossF);
#ifdef LOOKAHEAD_DEBUG prev_rampup += extra;
// Make sure we can break to a full stop before the move ends prev_rampdown += extra;
if(down > current->total_steps) {
sersendf_P(PSTR("FATAL ERROR during ramp scale, ramp is too long: down:%lu ; len:%lu ; target speed: %lu\r\n"),
down, current->total_steps, crossF);
dda_emergency_shutdown(PSTR("LA current ramp scale, ramp is too long"));
}
#endif
} else {
serprintf(PSTR("This: crossF is usable but we will not reach Fmax\r\n"));
// Can reach crossF; determine the apex between ramp up and ramp down
// In other words: calculate how long we can accelerate before decelerating to start at crossF
// and end at F = 0
uint32_t diff = (down + up - current->total_steps) / 2;
up -= diff;
down -= diff;
serprintf(PSTR("Apex: %lu - new up: %lu - new down: %lu\r\n"), diff, up, down);
// sanity stuff: calculate the speeds for these ramps
serprintf(PSTR("Ramp up speed: %lu mm/s\r\n"), dda_steps_to_velocity(up+prev->rampup_steps));
serprintf(PSTR("Ramp down speed: %lu mm/s\r\n"), dda_steps_to_velocity(down));
}
} }
// Save the results prev_rampdown = prev_total_steps - prev_rampdown;
this_rampup = up; prev_F_end_in_steps = crossF_in_steps;
this_rampdown = current->total_steps - down;
this_F_start = crossF;
this_start = ACCELERATE_RAMP_LEN(this_F_start);
serprintf(PSTR("Actual crossing speed: %lu\r\n"), crossF);
// Potential reverse processing: // Build ramps for current move.
// Make sure the crossing speed is the same, if its not, we need to slow the previous move to if (crossF_in_steps == this_F_in_steps) {
// the current crossing speed (note: the crossing speed could only be lowered). this_rampup = 0;
// This can happen when this move is a short move and the previous move was a larger or faster move: this_rampdown = crossF_in_steps;
// since we need to be able to stop if this is the last move, we lowered the crossing speed
// between this move and the previous move...
if(prev_F_end != crossF) {
// Third reverse pass: slow the previous move to end at the target crossing speed.
//ramp_scaler = ACCELERATE_SCALER(current->lead); //todo: prev_lead // Use scaler for previous leading axis (again)
// Note: use signed values so we can check if results go below zero
// Note 2: when up2 and/or down2 are below zero from the start, you found a bug in the logic above.
int32_t up2 = ACCELERATE_RAMP_LEN(prev_F) - ACCELERATE_RAMP_LEN(prev_F_start);
int32_t down2 = ACCELERATE_RAMP_LEN(prev_F) - ACCELERATE_RAMP_LEN(crossF);
// Test if both the ramp up and ramp down fit within the move
if(up2+down2 > prev_total_steps) {
int32_t diff = (up2 + down2 - (int32_t)prev_total_steps) / 2;
up2 -= diff;
down2 -= diff;
#ifdef LOOKAHEAD_DEBUG
if(up2 < 0 || down2 < 0) {
// Cannot reach crossF from prev_F_start - this should not happen!
sersendf_P(PSTR("FATAL ERROR during reverse pass ramp scale, ramps are too long: up:%ld ; down:%ld; len:%lu ; F_start: %lu ; crossF: %lu\r\n"),
up2, down2, prev_total_steps, prev_F_start, crossF);
sersendf_P(PSTR("Original up: %ld - down %ld (diff=%ld)\r\n"),up2+diff,down2+diff,diff);
dda_emergency_shutdown(PSTR("reverse pass ramp scale, can not reach F_end from F_start"));
}
#endif
}
// Assign the results
prev_rampup = up2;
prev_rampdown = prev_total_steps - down2;
prev_F_end = crossF;
prev_end = ACCELERATE_RAMP_LEN(prev_F_end);
} }
else {
this_rampup = 0;
this_rampdown = crossF_in_steps;
#ifdef LOOKAHEAD_DEBUG uint32_t extra = (this_total_steps - this_rampdown) >> 1;
if(crossF > current->endpoint.F || crossF > prev_F) uint32_t limit = this_F_in_steps - crossF_in_steps;
dda_emergency_shutdown(PSTR("Lookahead exceeded speed limits in crossing!")); extra = MIN(extra, limit);
// When debugging, print the 2 moves we joined this_rampup += extra;
// Legenda: Fs=F_start, len=# of steps, up/down=# steps in ramping, Fe=F_end this_rampdown += extra;
serprintf(PSTR("LA: (%lu) Fs=%lu, len=%lu, up=%lu, down=%lu, Fe=%lu <=> (%lu) Fs=%lu, len=%lu, up=%lu, down=%lu, Fe=0\r\n\r\n"), }
moveno-1, prev->F_start, prev->total_steps, prev->rampup_steps, this_rampdown = this_total_steps - this_rampdown;
prev->total_steps-prev->rampdown_steps, prev->F_end, this_F_start_in_steps = crossF_in_steps;
moveno, current->F_start, current->total_steps, current->rampup_steps,
current->total_steps - this_rampdown); serprintf(PSTR("prev_F_start: %lu\r\n"), prev_F_start_in_steps);
#endif serprintf(PSTR("prev_F: %lu\r\n"), prev_F_in_steps);
serprintf(PSTR("prev_rampup: %lu\r\n"), prev_rampup);
serprintf(PSTR("prev_rampdown: %lu\r\n"), prev_total_steps - prev_rampdown);
serprintf(PSTR("crossF: %lu\r\n"), crossF_in_steps);
serprintf(PSTR("this_rampup: %lu\r\n"), this_rampup);
serprintf(PSTR("this_rampdown: %lu\r\n"), this_total_steps - this_rampdown);
serprintf(PSTR("this_F: %lu\r\n"), this_F_in_steps);
uint8_t timeout = 0; uint8_t timeout = 0;
@ -563,17 +467,14 @@ void dda_join_moves(DDA *prev, DDA *current) {
// Determine if we are fast enough - if not, just leave the moves // Determine if we are fast enough - if not, just leave the moves
// Note: to test if the previous move was already executed and replaced by a new // Note: to test if the previous move was already executed and replaced by a new
// move, we compare the DDA id. // move, we compare the DDA id.
if(prev->live == 0 && prev->id == prev_id) { if(prev->live == 0 && prev->id == prev_id && current->live == 0 && current->id == this_id) {
prev->F_end = prev_F_end; prev->end_steps = prev_F_end_in_steps;
prev->end_steps = prev_end;
prev->rampup_steps = prev_rampup; prev->rampup_steps = prev_rampup;
prev->rampdown_steps = prev_rampdown; prev->rampdown_steps = prev_rampdown;
current->rampup_steps = this_rampup; current->rampup_steps = this_rampup;
current->rampdown_steps = this_rampdown; current->rampdown_steps = this_rampdown;
current->F_end = 0;
current->end_steps = 0; current->end_steps = 0;
current->F_start = this_F_start; current->start_steps = this_F_start_in_steps;
current->start_steps = this_start;
la_cnt++; la_cnt++;
} else } else
timeout = 1; timeout = 1;