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
  11 #include "mri.h"
  12 #include "nuts_bolts.h"
  13 #include "RingBuffer.h"
  14 #include "Gcode.h"
  15 #include "Module.h"
  16 #include "Kernel.h"
  17 #include "Block.h"
  18 #include "Planner.h"
  19 #include "Conveyor.h"
  20 #include "StepperMotor.h"
  21 #include "Config.h"
  22 #include "checksumm.h"
  23 #include "Robot.h"
  24 #include "Stepper.h"
  25 #include "ConfigValue.h"
  26
  27 #include <math.h>
  28
  29 #define acceleration_checksum          CHECKSUM("acceleration")
  30 #define max_jerk_checksum              CHECKSUM("max_jerk")
  31 #define junction_deviation_checksum    CHECKSUM("junction_deviation")
  32 #define minimum_planner_speed_checksum CHECKSUM("minimum_planner_speed")
  33
  34 // The Planner does the acceleration math for the queue of Blocks ( movements ).
  35 // It makes sure the speed stays within the configured constraints ( acceleration, junction_deviation, etc )
  36 // It goes over the list in both direction, every time a block is added, re-doing the math to make sure everything is optimal
  37
  38 Planner::Planner(){
  39     clear_vector_float(this->previous_unit_vec);
  40     this->has_deleted_block = false;
  41 }
  42
  43 void Planner::on_module_loaded(){
  44     register_for_event(ON_CONFIG_RELOAD);
  45     this->on_config_reload(this);
  46 }
  47
  48 // Configure acceleration
  49 void Planner::on_config_reload(void* argument){
  50     this->acceleration =       THEKERNEL->config->value(acceleration_checksum       )->by_default(100.0F )->as_number(); // Acceleration is in mm/s^2, see https://github.com/grbl/grbl/commit/9141ad282540eaa50a41283685f901f29c24ddbd#planner.c
  51     this->junction_deviation = THEKERNEL->config->value(junction_deviation_checksum )->by_default(  0.05F)->as_number();
  52     this->minimum_planner_speed = THEKERNEL->config->value(minimum_planner_speed_checksum )->by_default(0.0f)->as_number();
  53 }
  54
  55
  56 // Append a block to the queue, compute it's speed factors
  57 void Planner::append_block( float actuator_pos[], float rate_mm_s, float distance, float unit_vec[] )
  58 {
  59     // Create ( recycle ) a new block
  60     Block* block = THEKERNEL->conveyor->queue.head_ref();
  61
  62     // Direction bits
  63     block->direction_bits = 0;
  64     for (int i = 0; i < 3; i++)
  65     {
  66         int steps = THEKERNEL->robot->actuators[i]->steps_to_target(actuator_pos[i]);
  67
  68         if (steps < 0)
  69             block->direction_bits |= (1<<i);
  70
  71         // Update current position
  72         THEKERNEL->robot->actuators[i]->last_milestone_steps += steps;
  73         THEKERNEL->robot->actuators[i]->last_milestone_mm = actuator_pos[i];
  74
  75         block->steps[i] = labs(steps);
  76     }
  77
  78     // Max number of steps, for all axes
  79     block->steps_event_count = max( block->steps[ALPHA_STEPPER], max( block->steps[BETA_STEPPER], block->steps[GAMMA_STEPPER] ) );
  80
  81     block->millimeters = distance;
  82
  83     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
  84     // NOTE: Minimum stepper speed is limited by MINIMUM_STEPS_PER_MINUTE in stepper.c
  85     if( distance > 0.0F ){
  86         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
  87         block->nominal_rate = ceil(block->steps_event_count * rate_mm_s / distance); // (step/s) Always > 0
  88     }else{
  89         block->nominal_speed = 0.0F;
  90         block->nominal_rate  = 0;
  91     }
  92
  93     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
  94     // average travel per step event changes. For a line along one axis the travel per step event
  95     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
  96     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
  97     // To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
  98     // specifically for each line to compensate for this phenomenon:
  99     // Convert universal acceleration for direction-dependent stepper rate change parameter
 100     block->rate_delta = (block->steps_event_count * acceleration) / (distance * THEKERNEL->stepper->get_acceleration_ticks_per_second()); // (step/min/acceleration_tick)
 101
 102     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 103     // Let a circle be tangent to both previous and current path line segments, where the junction
 104     // deviation is defined as the distance from the junction to the closest edge of the circle,
 105     // colinear with the circle center. The circular segment joining the two paths represents the
 106     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 107     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 108     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 109     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 110     // nonlinearities of both the junction angle and junction velocity.
 111     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 112
 113     if (!THEKERNEL->conveyor->is_queue_empty())
 114     {
 115         float previous_nominal_speed = THEKERNEL->conveyor->queue.item_ref(THEKERNEL->conveyor->queue.prev(THEKERNEL->conveyor->queue.head_i))->nominal_speed;
 116
 117         if (previous_nominal_speed > 0.0F) {
 118             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 119             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 120             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 121                                 - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 122                                 - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 123
 124             // Skip and use default max junction speed for 0 degree acute junction.
 125             if (cos_theta < 0.95F) {
 126                 vmax_junction = min(previous_nominal_speed, block->nominal_speed);
 127                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 128                 if (cos_theta > -0.95F) {
 129                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 130                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 131                     vmax_junction = min(vmax_junction, sqrtf(this->acceleration * this->junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 132                 }
 133             }
 134         }
 135     }
 136     block->max_entry_speed = vmax_junction;
 137
 138     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 139     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters); //TODO: Get from config
 140     block->entry_speed = min(vmax_junction, v_allowable);
 141
 142     // Initialize planner efficiency flags
 143     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 144     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 145     // the current block and next block junction speeds are guaranteed to always be at their maximum
 146     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 147     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 148     // the reverse and forward planners, the corresponding block junction speed will always be at the
 149     // the maximum junction speed and may always be ignored for any speed reduction checks.
 150     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 151     else { block->nominal_length_flag = false; }
 152
 153     // Always calculate trapezoid for new block
 154     block->recalculate_flag = true;
 155
 156     // Update previous path unit_vector and nominal speed
 157     memcpy(this->previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 158
 159     // Math-heavy re-computing of the whole queue to take the new
 160     this->recalculate();
 161
 162     // The block can now be used
 163     block->ready();
 164
 165     THEKERNEL->conveyor->queue_head_block();
 166 }
 167
 168 void Planner::recalculate() {
 169     Conveyor::Queue_t &queue = THEKERNEL->conveyor->queue;
 170
 171     unsigned int block_index;
 172
 173     Block* previous;
 174     Block* current;
 175
 176     /*
 177      * a newly added block is decel limited
 178      *
 179      * we find its max entry speed given its exit speed
 180      *
 181      * for each block, walking backwards in the queue:
 182      *
 183      * if max entry speed == current entry speed
 184      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 185      * and thus we don't need to check entry speed for this block any more
 186      *
 187      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 188      *
 189      * for each block, walking forwards in the queue:
 190      *
 191      * given the exit speed of the previous block and our own max entry speed
 192      * we can tell if we're accel or decel limited (or coasting)
 193      *
 194      * if prev_exit > max_entry
 195      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 196      * if max_entry >= prev_exit
 197      *     then we're accel limited. set recalculate to false, work out max exit speed
 198      *
 199      * finally, work out trapezoid for the final (and newest) block.
 200      */
 201
 202     /*
 203      * Step 1:
 204      * For each block, given the exit speed and acceleration, find the maximum entry speed
 205      */
 206
 207     float entry_speed = minimum_planner_speed;
 208
 209     block_index = queue.head_i;
 210     current     = queue.item_ref(block_index);
 211
 212     if (!queue.is_empty())
 213     {
 214         while ((block_index != queue.tail_i) && current->recalculate_flag)
 215         {
 216             entry_speed = current->reverse_pass(entry_speed);
 217
 218             block_index = queue.prev(block_index);
 219             current     = queue.item_ref(block_index);
 220         }
 221
 222         /*
 223          * Step 2:
 224          * now current points to either tail or first non-recalculate block
 225          * and has not had its reverse_pass called
 226          * or its calc trap
 227          * entry_speed is set to the *exit* speed of current.
 228          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 229          */
 230
 231         float exit_speed = current->max_exit_speed();
 232
 233         while (block_index != queue.head_i)
 234         {
 235             previous    = current;
 236             block_index = queue.next(block_index);
 237             current     = queue.item_ref(block_index);
 238
 239             // we pass the exit speed of the previous block
 240             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 241             exit_speed = current->forward_pass(exit_speed);
 242
 243             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 244         }
 245     }
 246
 247     /*
 248      * Step 3:
 249      * work out trapezoid for final (and newest) block
 250      */
 251
 252     // now current points to the head item
 253     // which has not had calculate_trapezoid run yet
 254     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 255 }
 256
 257
 258 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 259 // acceleration within the allotted distance.
 260 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance) {
 261   return(
 262     sqrtf(target_velocity*target_velocity-2.0F*acceleration*distance)  //Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 263   );
 264 }
 265
 266