src/modules/robot/Planner.cpp

   1 /*
   2       This file is part of Smoothie (http://smoothieware.org/). The motion control part is heavily based on Grbl (https://github.com/simen/grbl) with additions from Sungeun K. Jeon (https://github.com/chamnit/grbl)
   3       Smoothie is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
   4       Smoothie is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
   5       You should have received a copy of the GNU General Public License along with Smoothie. If not, see <http://www.gnu.org/licenses/>.
   6 */
   7
   8 using namespace std;
   9 #include <vector>
  10 #include "libs/nuts_bolts.h"
  11 #include "libs/RingBuffer.h"
  12 #include "../communication/utils/Gcode.h"
  13 #include "libs/Module.h"
  14 #include "libs/Kernel.h"
  15 #include "Block.h"
  16 #include "Planner.h"
  17 #include "Conveyor.h"
  18
  19 // The Planner does the acceleration math for the queue of Blocks ( movements ).
  20 // It makes sure the speed stays within the configured constraints ( acceleration, junction_deviation, etc )
  21 // It goes over the list in both direction, every time a block is added, re-doing the math to make sure everything is optimal
  22
  23 Planner::Planner(){
  24     clear_vector(this->position);
  25     clear_vector_double(this->previous_unit_vec);
  26     this->previous_nominal_speed = 0.0;
  27     this->has_deleted_block = false;
  28 }
  29
  30 void Planner::on_module_loaded(){
  31     register_for_event(ON_CONFIG_RELOAD);
  32     this->on_config_reload(this);
  33 }
  34
  35 // Configure acceleration
  36 void Planner::on_config_reload(void* argument){
  37     this->acceleration =       this->kernel->config->value(acceleration_checksum       )->by_default(100 )->as_number() * 60 * 60; // Acceleration is in mm/minute^2, see https://github.com/grbl/grbl/commit/9141ad282540eaa50a41283685f901f29c24ddbd#planner.c
  38     this->junction_deviation = this->kernel->config->value(junction_deviation_checksum )->by_default(0.05)->as_number();
  39 }
  40
  41
  42 // Append a block to the queue, compute it's speed factors
  43 void Planner::append_block( int target[], double feed_rate, double distance, double deltas[] ){
  44
  45     // Stall here if the queue is ful
  46     this->kernel->conveyor->wait_for_queue(2);
  47
  48     // Create ( recycle ) a new block
  49     Block* block = this->kernel->conveyor->new_block();
  50     block->planner = this;
  51
  52     // Direction bits
  53     block->direction_bits = 0;
  54     for( int stepper=ALPHA_STEPPER; stepper<=GAMMA_STEPPER; stepper++){
  55         if( target[stepper] < position[stepper] ){ block->direction_bits |= (1<<stepper); }
  56     }
  57
  58     // Number of steps for each stepper
  59     for( int stepper=ALPHA_STEPPER; stepper<=GAMMA_STEPPER; stepper++){ block->steps[stepper] = labs(target[stepper] - this->position[stepper]); }
  60
  61     // Max number of steps, for all axes
  62     block->steps_event_count = max( block->steps[ALPHA_STEPPER], max( block->steps[BETA_STEPPER], block->steps[GAMMA_STEPPER] ) );
  63
  64     block->millimeters = distance;
  65     double inverse_millimeters = 0;
  66     if( distance > 0 ){ inverse_millimeters = 1.0/distance; }
  67
  68     // Calculate speed in mm/minute for each axis. No divide by zero due to previous checks.
  69     // NOTE: Minimum stepper speed is limited by MINIMUM_STEPS_PER_MINUTE in stepper.c
  70     double inverse_minute = feed_rate * inverse_millimeters;
  71     if( distance > 0 ){
  72         block->nominal_speed = block->millimeters * inverse_minute;           // (mm/min) Always > 0
  73         block->nominal_rate = ceil(block->steps_event_count * inverse_minute); // (step/min) Always > 0
  74     }else{
  75         block->nominal_speed = 0;
  76         block->nominal_rate = 0;
  77     }
  78
  79     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
  80     // average travel per step event changes. For a line along one axis the travel per step event
  81     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
  82     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
  83     // To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
  84     // specifically for each line to compensate for this phenomenon:
  85     // Convert universal acceleration for direction-dependent stepper rate change parameter
  86     block->rate_delta = (float)( ( block->steps_event_count*inverse_millimeters * this->acceleration ) / ( this->kernel->stepper->acceleration_ticks_per_second * 60 ) ); // (step/min/acceleration_tick)
  87
  88     // Compute path unit vector
  89     double unit_vec[3];
  90     unit_vec[X_AXIS] = deltas[X_AXIS]*inverse_millimeters;
  91     unit_vec[Y_AXIS] = deltas[Y_AXIS]*inverse_millimeters;
  92     unit_vec[Z_AXIS] = deltas[Z_AXIS]*inverse_millimeters;
  93
  94     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
  95     // Let a circle be tangent to both previous and current path line segments, where the junction
  96     // deviation is defined as the distance from the junction to the closest edge of the circle,
  97     // colinear with the circle center. The circular segment joining the two paths represents the
  98     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
  99     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 100     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 101     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 102     // nonlinearities of both the junction angle and junction velocity.
 103     double vmax_junction = MINIMUM_PLANNER_SPEED; // Set default max junction speed
 104
 105     if (this->kernel->conveyor->queue.size() > 1 && (this->previous_nominal_speed > 0.0)) {
 106       // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 107       // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 108       double cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 109                          - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 110                          - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 111
 112       // Skip and use default max junction speed for 0 degree acute junction.
 113       if (cos_theta < 0.95) {
 114         vmax_junction = min(this->previous_nominal_speed,block->nominal_speed);
 115         // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 116         if (cos_theta > -0.95) {
 117           // Compute maximum junction velocity based on maximum acceleration and junction deviation
 118           double sin_theta_d2 = sqrt(0.5*(1.0-cos_theta)); // Trig half angle identity. Always positive.
 119           vmax_junction = min(vmax_junction,
 120             sqrt(this->acceleration * this->junction_deviation * sin_theta_d2/(1.0-sin_theta_d2)) );
 121         }
 122       }
 123     }
 124     block->max_entry_speed = vmax_junction;
 125
 126     // Initialize block entry speed. Compute based on deceleration to user-defined MINIMUM_PLANNER_SPEED.
 127     double v_allowable = this->max_allowable_speed(-this->acceleration,0.0,block->millimeters); //TODO: Get from config
 128     block->entry_speed = min(vmax_junction, v_allowable);
 129
 130     // Initialize planner efficiency flags
 131     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 132     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 133     // the current block and next block junction speeds are guaranteed to always be at their maximum
 134     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 135     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 136     // the reverse and forward planners, the corresponding block junction speed will always be at the
 137     // the maximum junction speed and may always be ignored for any speed reduction checks.
 138     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 139     else { block->nominal_length_flag = false; }
 140     block->recalculate_flag = true; // Always calculate trapezoid for new block
 141
 142     // Update previous path unit_vector and nominal speed
 143     memcpy(this->previous_unit_vec, unit_vec, sizeof(unit_vec)); // previous_unit_vec[] = unit_vec[]
 144     this->previous_nominal_speed = block->nominal_speed;
 145
 146     // Update current position
 147     memcpy(this->position, target, sizeof(int)*3);
 148
 149     // Math-heavy re-computing of the whole queue to take the new
 150     this->recalculate();
 151
 152     // The block can now be used
 153     block->ready();
 154
 155 }
 156
 157
 158 // Recalculates the motion plan according to the following algorithm:
 159 //
 160 // 1. Go over every block in reverse order and calculate a junction speed reduction (i.e. block_t.entry_factor)
 161 // so that:
 162 //   a. The junction jerk is within the set limit
 163 //   b. No speed reduction within one block requires faster deceleration than the one, true constant
 164 //      acceleration.
 165 // 2. Go over every block in chronological order and dial down junction speed reduction values if
 166 //   a. The speed increase within one block would require faster accelleration than the one, true
 167 //      constant acceleration.
 168 //
 169 // When these stages are complete all blocks have an entry_factor that will allow all speed changes to
 170 // be performed using only the one, true constant acceleration, and where no junction jerk is jerkier than
 171 // the set limit. Finally it will:
 172 //
 173 // 3. Recalculate trapezoids for all blocks.
 174 //
 175 void Planner::recalculate() {
 176     int block_index = this->kernel->conveyor->queue.head;
 177
 178     Block* previous;
 179     Block* current;
 180     Block* next;
 181
 182     current = &this->kernel->conveyor->queue.buffer[block_index];
 183     current->recalculate_flag = true;
 184
 185     while ((block_index != this->kernel->conveyor->queue.tail) && (current->recalculate_flag))
 186     {
 187         block_index = this->kernel->conveyor->queue.prev_block_index(block_index);
 188
 189         next = current;
 190         current = &this->kernel->conveyor->queue.buffer[block_index];
 191
 192         current->recalculate_flag = false;
 193
 194         current->reverse_pass(next);
 195     }
 196
 197     block_index = this->kernel->conveyor->queue.next_block_index(block_index);
 198
 199     // Recalculates the trapezoid speed profiles for flagged blocks in the plan according to the
 200     // entry_speed for each junction and the entry_speed of the next junction. Must be called by
 201     // planner_recalculate() after updating the blocks. Any recalulate flagged junction will
 202     // compute the two adjacent trapezoids to the junction, since the junction speed corresponds
 203     // to exit speed and entry speed of one another.
 204     while (block_index != this->kernel->conveyor->queue.head)
 205     {
 206         previous = current;
 207         current = &this->kernel->conveyor->queue.buffer[block_index];
 208
 209         current->forward_pass(previous);
 210
 211         // Recalculate if current block entry or exit junction speed has changed.
 212         if (previous->recalculate_flag || current->recalculate_flag )
 213         {
 214             previous->calculate_trapezoid( previous->entry_speed/previous->nominal_speed, current->entry_speed/previous->nominal_speed );
 215             previous->recalculate_flag = false;
 216         }
 217
 218         block_index = this->kernel->conveyor->queue.next_block_index(block_index);
 219     }
 220
 221     // Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
 222     current->calculate_trapezoid( current->entry_speed/current->nominal_speed, MINIMUM_PLANNER_SPEED/current->nominal_speed );
 223     current->recalculate_flag = false;
 224 }
 225
 226 // Debug function
 227 void Planner::dump_queue(){
 228     for( int index = 0; index <= this->kernel->conveyor->queue.size()-1; index++ ){
 229        if( index > 10 && index < this->kernel->conveyor->queue.size()-10 ){ continue; }
 230        this->kernel->streams->printf("block %03d > ", index);
 231        this->kernel->conveyor->queue.get_ref(index)->debug(this->kernel);
 232     }
 233 }
 234
 235 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 236 // acceleration within the allotted distance.
 237 double Planner::max_allowable_speed(double acceleration, double target_velocity, double distance) {
 238   return(
 239     sqrt(target_velocity*target_velocity-2L*acceleration*distance)  //Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 240   );
 241 }
 242
 243