/** \file \brief Digital differential analyser - this is where we figure out which steppers need to move, and when they need to move */ #include "dda_lookahead.h" #ifdef LOOKAHEAD #include #include #include #include #ifndef SIMULATOR #include #endif #include "dda_maths.h" #include "dda.h" #include "timer.h" #include "delay.h" #include "serial.h" #include "sermsg.h" #include "gcode_parse.h" #include "dda_queue.h" #include "debug.h" #include "sersendf.h" #include "pinio.h" #include "memory_barrier.h" extern uint8_t use_lookahead; uint32_t lookahead_joined = 0; // Total number of moves joined together uint32_t lookahead_timeout = 0; // Moves that did not compute in time to be actually joined // Used for look-ahead debugging #ifdef LOOKAHEAD_DEBUG_VERBOSE #define serprintf(...) sersendf_P(__VA_ARGS__) #else #define serprintf(...) #endif // 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 // rounding error. // Warning: this is an expensive function as it requires a square root to get the result. // uint32_t dda_steps_to_velocity(uint32_t steps) { // v(t) = a*t, with v in mm/s and a = acceleration in mm/s² // s(t) = 1/2*a*t² with s (displacement) in mm // Rewriting yields v(s) = sqrt(2*a*s) // Rewriting into steps and seperation in constant part and dynamic part: // F_steps = sqrt((2000*a)/STEPS_PER_M_X) * 60 * sqrt(steps) static uint32_t part = 0; if(part == 0) part = int_sqrt((uint32_t)((2000.0f*ACCELERATION*3600.0f*10000.0f)/(float)STEPS_PER_M_X)); uint32_t res = int_sqrt((steps) * 10000) * part; return res / 10000; } /** * Determine the 'jerk' between 2 2D vectors and their speeds. The jerk can be * used to obtain an acceptable speed for changing directions between moves. * @param x1 x component of first vector * @param y1 y component of first vector * @param F1 feed rate of first move * @param x2 x component of second vector * @param y2 y component of second vector * @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) { const int maxlen = 10000; // Normalize vectors so their length will be fixed // 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); int32_t len = int_sqrt(x1*x1+y1*y1); x1 = (x1 * maxlen) / len; y1 = (y1 * maxlen) / len; len = int_sqrt(x2*x2+y2*y2); x2 = (x2 * maxlen) / len; y2 = (y2 * maxlen) / len; //sersendf_P(PSTR("Normalized vectors: (%ld, %ld) and (%ld, %ld)\r\n"),x1,y1,x2,y2); // Now scale the normalized vectors by their speeds x1 *= F1; y1 *= F1; x2 *= F2; y2 *= F2; //sersendf_P(PSTR("Speed vectors: (%ld, %ld) and (%ld, %ld)\r\n"),x1,y1,x2,y2); // The difference between the vectors actually depicts the jerk x1 -= x2; y1 -= y2; //sersendf_P(PSTR("Jerk vector: (%ld, %ld)\r\n"),x1,y1); return approx_distance(x1,y1) / maxlen; } /** * Determine the 'jerk' for 2 1D vectors and their speeds. The jerk can be used to obtain an * acceptable speed for changing directions between moves. * @param x component of 1d vector - used to determine if we go back or forward * @param F feed rate */ int dda_jerk_size_1d(int32_t x1, uint32_t F1, int32_t x2, uint32_t F2) { if(x1 > 0) x1 = F1; else x1 = -F1; if(x2 > 0) x2 = F2; else x2 = -F2; // The difference between the vectors actually depicts the jerk x1 -= x2; if(x1 < 0) x1 = -x1; // Make sure it remains positive //sersendf_P(PSTR("Jerk vector: (%ld, %ld)\r\n"),x1,y1); return x1; } /** * Determine the 'jerk' between 2 vectors and their speeds. The jerk can be used to obtain an * acceptable speed for changing directions between moves. * Instead of using 2 axis at once, consider the jerk for each axis individually and take the * upper limit between both. This ensures that each axis does not changes speed too fast. * @param x1 x component of first vector * @param y1 y component of first vector * @param F1 feed rate of first move * @param x2 x component of second vector * @param y2 y component of second vector * @param F2 feed rate of second move */ int dda_jerk_size_2d(int32_t x1, int32_t y1, uint32_t F1, int32_t x2, int32_t y2, uint32_t F2) { return MAX(dda_jerk_size_1d(x1,F1,x2,F2),dda_jerk_size_1d(y1,F1,y2,F2)); } /** * Safety procedure: if something goes wrong, for example an opto is triggered during normal movement, * we shut down the entire machine. * @param msg The reason why the machine did an emergency stop */ void dda_emergency_shutdown(PGM_P msg) { // Todo: is it smart to enable all interrupts again? e.g. can we create concurrent executions? sei(); // Enable interrupts to print the message serial_writestr_P(PSTR("error: emergency stop:")); if(msg!=NULL) serial_writestr_P(msg); serial_writestr_P(PSTR("\r\n")); delay_ms(20); // Delay so the buffer can be flushed - otherwise the message is never sent timer_stop(); queue_flush(); power_off(); cli(); for (;;) { } } /** * Join 2 moves by removing the full stop between them, where possible. * To join the moves, the expected jerk - or force - of the change in direction is calculated. * The jerk is used to scale the common feed rate between both moves to obtain an acceptable speed * to transition between 'prev' and 'current'. * * Premise: we currently join the last move in the queue and the one before it (if any). * This means the feed rate at the end of the 'current' move is 0. * * Premise: the 'current' move is not dispatched in the queue: it should remain constant while this * function is running. * * Note: the planner always makes sure the movement can be stopped within the * last move (= 'current'); as a result a lot of small moves will still limit the speed. */ void dda_join_moves(DDA *prev, DDA *current) { // Calculating the look-ahead settings can take a while; before modifying // 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). uint32_t prev_F, prev_F_start, prev_F_end, prev_end; uint32_t prev_rampup, prev_rampdown, prev_total_steps; uint8_t prev_id; // 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. // 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. uint32_t this_F_start, this_start, this_rampup, this_rampdown; int32_t jerk, jerk_e; // Expresses the forces if we would change directions at full speed static uint32_t la_cnt = 0; // Counter: how many moves did we join? #ifdef LOOKAHEAD_DEBUG static uint32_t moveno = 0; // Debug counter to number the moves - helps while debugging moveno++; #endif // Bail out if there's nothing to join (e.g. G1 F1500). if ( ! prev || prev->nullmove) return; serprintf(PSTR("Current Delta: %ld,%ld,%ld E:%ld Live:%d\r\n"), current->delta_um.X, current->delta_um.Y, current->delta_um.Z, current->delta_um.E, current->live); serprintf(PSTR("Prev Delta: %ld,%ld,%ld E:%ld Live:%d\r\n"), prev->delta_um.X, prev->delta_um.Y, prev->delta_um.Z, prev->delta_um.E, prev->live); // Look-ahead: attempt to join moves into smooth movements // Note: moves are only modified after the calculations are complete. // Only prepare for look-ahead if we have 2 available moves to // join and the Z axis is unused (for now, Z axis moves are NOT joined). if (prev->live == 0 && prev->delta_um.Z == current->delta_um.Z) { // Calculate the jerk if the previous move and this move would be joined // together at full speed. jerk = dda_jerk_size_2d(prev->delta_um.X, prev->delta_um.Y, prev->endpoint.F, current->delta_um.X, current->delta_um.Y, current->endpoint.F); serprintf(PSTR("Jerk: %lu\r\n"), jerk); jerk_e = dda_jerk_size_1d(prev->delta_um.E, prev->endpoint.F, current->delta_um.E, current->endpoint.F); serprintf(PSTR("Jerk_e: %lu\r\n"), jerk_e); } else { // Move already executing or Z moved: abort the join return; } // Make sure we have 2 moves and the previous move is not already active if (prev->live == 0) { // Perform an atomic copy to preserve volatile parameters during the calculations ATOMIC_START prev_id = prev->id; prev_F = prev->endpoint.F; prev_F_start = prev->F_start; prev_F_end = prev->F_end; prev_rampup = prev->rampup_steps; prev_rampdown = prev->rampdown_steps; prev_total_steps = prev->total_steps; ATOMIC_END // The initial crossing speed is the minimum between both target speeds // Note: this is a given: the start speed and end speed can NEVER be // higher than the target speed in a move! // Note 2: this provides an upper limit, if needed, the speed is lowered. uint32_t crossF = prev_F; if(crossF > current->endpoint.F) crossF = current->endpoint.F; //sersendf_P(PSTR("j:%lu - XF:%lu"), jerk, crossF); // If the XY jerk is too big, scale the proposed cross speed if(jerk > LOOKAHEAD_MAX_JERK_XY) { serprintf(PSTR("Jerk too big: scale cross speed between moves\r\n")); // Get the highest speed between both moves if(crossF < prev_F) crossF = prev_F; // Perform an exponential scaling uint32_t ujerk = (uint32_t)jerk; // Use unsigned to double the range before overflowing crossF = (crossF*LOOKAHEAD_MAX_JERK_XY*LOOKAHEAD_MAX_JERK_XY)/(ujerk*ujerk); // Optimize: if the crossing speed is zero, there is no join possible between these // two (fast) moves. Stop calculating and leave the full stop that is currently between // them. if(crossF == 0) return; // Safety: make sure we never exceed the maximum speed of a move if(crossF > current->endpoint.F) crossF = current->endpoint.F; if(crossF > prev_F) crossF = prev_F; sersendf_P(PSTR("=>F:%lu"), crossF); } // Same to the extruder jerk: make sure we do not yank it if(jerk_e > LOOKAHEAD_MAX_JERK_E) { sersendf_P(PSTR("Jerk_e too big: scale cross speed between moves\r\n")); uint32_t crossF2 = MAX(current->endpoint.F, prev_F); // Perform an exponential scaling uint32_t ujerk = (uint32_t)jerk_e; // Use unsigned to double the range before overflowing crossF2 = (crossF2*LOOKAHEAD_MAX_JERK_E*LOOKAHEAD_MAX_JERK_E)/(ujerk*ujerk); // Only continue with joining if there is a feasible crossing speed if(crossF2 == 0) return; // Safety: make sure the proposed speed is not higher than the target speeds of each move crossF2 = MIN(crossF2, current->endpoint.F); crossF2 = MIN(crossF2, prev_F); if(crossF2 > crossF) { sersendf_P(PSTR("Jerk_e: %lu => crossF: %lu (original: %lu)\r\n"), jerk_e, crossF2, crossF); } // Pick the crossing speed for these 2 move to be within the jerk limits crossF = MIN(crossF, crossF2); } // Show the proposed crossing speed - this might get adjusted below serprintf(PSTR("Initial crossing speed: %lu\r\n"), crossF); // Forward check: test if we can actually reach the target speed in the previous move // If not: we need to determine the obtainable speed and adjust crossF accordingly. // Note: these ramps can be longer than the move: if so we can not reach top speed. 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 > current->endpoint.F) crossF = current->endpoint.F; // 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 // Sanity check: the ramp up should never exceed the move length 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 // Sanity check: make sure the speed limits are maintained if(prev_F_start > prev_F || crossF > prev_F) { 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); dda_emergency_shutdown(PSTR("Prev target speed exceeded")); } #endif } // Save the results prev_rampup = up; prev_rampdown = prev_total_steps - down; prev_F_end = crossF; prev_end = ACCELERATE_RAMP_LEN(prev_F_end); #ifdef LOOKAHEAD_DEBUG // Sanity check: make sure the speed limits are maintained if(crossF > current->endpoint.F) { serprintf(PSTR("This target speed exceeded!: F_start:%lu ; F:%lu ; prev_F_end:%lu\r\n"), crossF, current->endpoint.F); dda_emergency_shutdown(PSTR("This target speed exceeded")); } #endif // Forward check 2: test if we can actually reach the target speed in this move. // If not: determine obtainable speed and adjust crossF accordingly. If that // happens, a third (reverse) pass is needed to lower the speeds in the previous move... //ramp_scaler = ACCELERATE_SCALER(current->lead); // Use scaler for current leading axis up = ACCELERATE_RAMP_LEN(current->endpoint.F) - ACCELERATE_RAMP_LEN(crossF); down = ACCELERATE_RAMP_LEN(current->endpoint.F); // 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 > current->endpoint.F) crossF = current->endpoint.F; // crossF will be conservative: calculate the actual ramp down length down = ACCELERATE_RAMP_LEN(crossF); #ifdef LOOKAHEAD_DEBUG // Make sure we can break to a full stop before the move ends 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 this_rampup = up; 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: // Make sure the crossing speed is the same, if its not, we need to slow the previous move to // the current crossing speed (note: the crossing speed could only be lowered). // This can happen when this move is a short move and the previous move was a larger or faster move: // 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); } #ifdef LOOKAHEAD_DEBUG if(crossF > current->endpoint.F || crossF > prev_F) dda_emergency_shutdown(PSTR("Lookahead exceeded speed limits in crossing!")); // When debugging, print the 2 moves we joined // Legenda: Fs=F_start, len=# of steps, up/down=# steps in ramping, Fe=F_end 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, prev->total_steps-prev->rampdown_steps, prev->F_end, moveno, current->F_start, current->total_steps, current->rampup_steps, current->total_steps - this_rampdown); #endif uint8_t timeout = 0; ATOMIC_START // Evaluation: determine how we did... lookahead_joined++; // 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 // move, we compare the DDA id. if(prev->live == 0 && prev->id == prev_id) { prev->F_end = prev_F_end; prev->end_steps = prev_end; prev->rampup_steps = prev_rampup; prev->rampdown_steps = prev_rampdown; current->rampup_steps = this_rampup; current->rampdown_steps = this_rampdown; current->F_end = 0; current->end_steps = 0; current->F_start = this_F_start; current->start_steps = this_start; la_cnt++; } else timeout = 1; ATOMIC_END // If we were not fast enough, any feedback will happen outside the atomic block: if(timeout) { sersendf_P(PSTR("Error: look ahead not fast enough\r\n")); lookahead_timeout++; } } } #endif /* LOOKAHEAD */