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 z_acceleration_checksum        CHECKSUM("z_acceleration")
  31 #define junction_deviation_checksum    CHECKSUM("junction_deviation")
  32 #define z_junction_deviation_checksum  CHECKSUM("z_junction_deviation")
  33 #define minimum_planner_speed_checksum CHECKSUM("minimum_planner_speed")
  34
  35 // The Planner does the acceleration math for the queue of Blocks ( movements ).
  36 // It makes sure the speed stays within the configured constraints ( acceleration, junction_deviation, etc )
  37 // It goes over the list in both direction, every time a block is added, re-doing the math to make sure everything is optimal
  38
  39 Planner::Planner(){
  40     clear_vector_float(this->previous_unit_vec);
  41     config_load();
  42 }
  43
  44 // Configure acceleration
  45 void Planner::config_load(){
  46     this->acceleration = THEKERNEL->config->value(acceleration_checksum)->by_default(100.0F )->as_number(); // Acceleration is in mm/s^2
  47     this->z_acceleration = THEKERNEL->config->value(z_acceleration_checksum)->by_default(0.0F )->as_number(); // disabled by default
  48
  49     this->junction_deviation = THEKERNEL->config->value(junction_deviation_checksum)->by_default(0.05F)->as_number();
  50     this->z_junction_deviation = THEKERNEL->config->value(z_junction_deviation_checksum)->by_default(-1)->as_number(); // disabled by default
  51     this->minimum_planner_speed = THEKERNEL->config->value(minimum_planner_speed_checksum)->by_default(0.0f)->as_number();
  52 }
  53
  54
  55 // Append a block to the queue, compute it's speed factors
  56 void Planner::append_block( float actuator_pos[], float rate_mm_s, float distance, float unit_vec[] )
  57 {
  58     float acceleration, junction_deviation;
  59
  60     // Create ( recycle ) a new block
  61     Block* block = THEKERNEL->conveyor->queue.head_ref();
  62
  63
  64     // Direction bits
  65     for (int i = 0; i < 3; i++)
  66     {
  67         int steps = THEKERNEL->robot->actuators[i]->steps_to_target(actuator_pos[i]);
  68
  69         block->direction_bits[i] = (steps < 0) ? 1 : 0;
  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     acceleration= this->acceleration;
  79     junction_deviation= this->junction_deviation;
  80
  81     // use either regular acceleration or a z only move accleration
  82     if(block->steps[ALPHA_STEPPER] == 0 && block->steps[BETA_STEPPER] == 0) {
  83         // z only move
  84         if(this->z_acceleration > 0.0F) acceleration= this->z_acceleration;
  85         if(this->z_junction_deviation >= 0.0F) junction_deviation= this->z_junction_deviation;
  86     }
  87
  88     block->acceleration= acceleration; // save in block
  89
  90     // Max number of steps, for all axes
  91     block->steps_event_count = max( block->steps[ALPHA_STEPPER], max( block->steps[BETA_STEPPER], block->steps[GAMMA_STEPPER] ) );
  92
  93     block->millimeters = distance;
  94
  95     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
  96     // NOTE: Minimum stepper speed is limited by MINIMUM_STEPS_PER_MINUTE in stepper.c
  97     if( distance > 0.0F ){
  98         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
  99         block->nominal_rate = ceilf(block->steps_event_count * rate_mm_s / distance); // (step/s) Always > 0
 100     }else{
 101         block->nominal_speed = 0.0F;
 102         block->nominal_rate  = 0;
 103     }
 104
 105     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
 106     // average travel per step event changes. For a line along one axis the travel per step event
 107     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
 108     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
 109     // To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
 110     // specifically for each line to compensate for this phenomenon:
 111     // Convert universal acceleration for direction-dependent stepper rate change parameter
 112     block->rate_delta = (block->steps_event_count * acceleration) / (distance * THEKERNEL->acceleration_ticks_per_second); // (step/min/acceleration_tick)
 113
 114     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 115     // Let a circle be tangent to both previous and current path line segments, where the junction
 116     // deviation is defined as the distance from the junction to the closest edge of the circle,
 117     // colinear with the circle center. The circular segment joining the two paths represents the
 118     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 119     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 120     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 121     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 122     // nonlinearities of both the junction angle and junction velocity.
 123
 124     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 125     // and this allows one to stop with little to no decleration in many cases. This is particualrly bad on leadscrew based systems that will skip steps.
 126     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 127
 128     if (!THEKERNEL->conveyor->is_queue_empty())
 129     {
 130         float previous_nominal_speed = THEKERNEL->conveyor->queue.item_ref(THEKERNEL->conveyor->queue.prev(THEKERNEL->conveyor->queue.head_i))->nominal_speed;
 131
 132         if (previous_nominal_speed > 0.0F && junction_deviation > 0.0F) {
 133             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 134             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 135             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 136                                 - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 137                                 - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 138
 139             // Skip and use default max junction speed for 0 degree acute junction.
 140             if (cos_theta < 0.95F) {
 141                 vmax_junction = min(previous_nominal_speed, block->nominal_speed);
 142                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 143                 if (cos_theta > -0.95F) {
 144                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 145                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 146                     vmax_junction = min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 147                 }
 148             }
 149         }
 150     }
 151     block->max_entry_speed = vmax_junction;
 152
 153     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 154     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 155     block->entry_speed = min(vmax_junction, v_allowable);
 156
 157     // Initialize planner efficiency flags
 158     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 159     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 160     // the current block and next block junction speeds are guaranteed to always be at their maximum
 161     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 162     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 163     // the reverse and forward planners, the corresponding block junction speed will always be at the
 164     // the maximum junction speed and may always be ignored for any speed reduction checks.
 165     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 166     else { block->nominal_length_flag = false; }
 167
 168     // Always calculate trapezoid for new block
 169     block->recalculate_flag = true;
 170
 171     // Update previous path unit_vector and nominal speed
 172     memcpy(this->previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 173
 174     // Math-heavy re-computing of the whole queue to take the new
 175     this->recalculate();
 176
 177     // The block can now be used
 178     block->ready();
 179
 180     THEKERNEL->conveyor->queue_head_block();
 181 }
 182
 183 void Planner::recalculate() {
 184     Conveyor::Queue_t &queue = THEKERNEL->conveyor->queue;
 185
 186     unsigned int block_index;
 187
 188     Block* previous;
 189     Block* current;
 190
 191     /*
 192      * a newly added block is decel limited
 193      *
 194      * we find its max entry speed given its exit speed
 195      *
 196      * for each block, walking backwards in the queue:
 197      *
 198      * if max entry speed == current entry speed
 199      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 200      * and thus we don't need to check entry speed for this block any more
 201      *
 202      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 203      *
 204      * for each block, walking forwards in the queue:
 205      *
 206      * given the exit speed of the previous block and our own max entry speed
 207      * we can tell if we're accel or decel limited (or coasting)
 208      *
 209      * if prev_exit > max_entry
 210      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 211      * if max_entry >= prev_exit
 212      *     then we're accel limited. set recalculate to false, work out max exit speed
 213      *
 214      * finally, work out trapezoid for the final (and newest) block.
 215      */
 216
 217     /*
 218      * Step 1:
 219      * For each block, given the exit speed and acceleration, find the maximum entry speed
 220      */
 221
 222     float entry_speed = minimum_planner_speed;
 223
 224     block_index = queue.head_i;
 225     current     = queue.item_ref(block_index);
 226
 227     if (!queue.is_empty())
 228     {
 229         while ((block_index != queue.tail_i) && current->recalculate_flag)
 230         {
 231             entry_speed = current->reverse_pass(entry_speed);
 232
 233             block_index = queue.prev(block_index);
 234             current     = queue.item_ref(block_index);
 235         }
 236
 237         /*
 238          * Step 2:
 239          * now current points to either tail or first non-recalculate block
 240          * and has not had its reverse_pass called
 241          * or its calc trap
 242          * entry_speed is set to the *exit* speed of current.
 243          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 244          */
 245
 246         float exit_speed = current->max_exit_speed();
 247
 248         while (block_index != queue.head_i)
 249         {
 250             previous    = current;
 251             block_index = queue.next(block_index);
 252             current     = queue.item_ref(block_index);
 253
 254             // we pass the exit speed of the previous block
 255             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 256             exit_speed = current->forward_pass(exit_speed);
 257
 258             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 259         }
 260     }
 261
 262     /*
 263      * Step 3:
 264      * work out trapezoid for final (and newest) block
 265      */
 266
 267     // now current points to the head item
 268     // which has not had calculate_trapezoid run yet
 269     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 270 }
 271
 272
 273 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 274 // acceleration within the allotted distance.
 275 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance) {
 276   return(
 277     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
 278   );
 279 }
 280
 281