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( ActuatorCoordinates &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 (size_t i = 0; i < THEKERNEL->robot->actuators.size(); 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     int steps_event_count = 0;
  92     for (size_t s = 0; s < THEKERNEL->robot->actuators.size(); s++)
  93         steps_event_count = std::max(steps_event_count, block->steps[s]);
  94     block->steps_event_count = steps_event_count;
  95
  96     block->millimeters = distance;
  97
  98     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
  99     // NOTE: Minimum stepper speed is limited by MINIMUM_STEPS_PER_MINUTE in stepper.c
 100     if( distance > 0.0F ){
 101         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
 102         block->nominal_rate = ceilf(block->steps_event_count * rate_mm_s / distance); // (step/s) Always > 0
 103     }else{
 104         block->nominal_speed = 0.0F;
 105         block->nominal_rate  = 0;
 106     }
 107
 108     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
 109     // average travel per step event changes. For a line along one axis the travel per step event
 110     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
 111     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
 112     // To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
 113     // specifically for each line to compensate for this phenomenon:
 114     // Convert universal acceleration for direction-dependent stepper rate change parameter
 115     block->rate_delta = (block->steps_event_count * acceleration) / (distance * THEKERNEL->acceleration_ticks_per_second); // (step/min/acceleration_tick)
 116
 117     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 118     // Let a circle be tangent to both previous and current path line segments, where the junction
 119     // deviation is defined as the distance from the junction to the closest edge of the circle,
 120     // colinear with the circle center. The circular segment joining the two paths represents the
 121     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 122     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 123     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 124     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 125     // nonlinearities of both the junction angle and junction velocity.
 126
 127     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 128     // 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.
 129     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 130
 131     if (!THEKERNEL->conveyor->is_queue_empty())
 132     {
 133         float previous_nominal_speed = THEKERNEL->conveyor->queue.item_ref(THEKERNEL->conveyor->queue.prev(THEKERNEL->conveyor->queue.head_i))->nominal_speed;
 134
 135         if (previous_nominal_speed > 0.0F && junction_deviation > 0.0F) {
 136             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 137             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 138             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 139                                 - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 140                                 - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 141
 142             // Skip and use default max junction speed for 0 degree acute junction.
 143             if (cos_theta < 0.95F) {
 144                 vmax_junction = min(previous_nominal_speed, block->nominal_speed);
 145                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 146                 if (cos_theta > -0.95F) {
 147                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 148                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 149                     vmax_junction = min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 150                 }
 151             }
 152         }
 153     }
 154     block->max_entry_speed = vmax_junction;
 155
 156     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 157     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 158     block->entry_speed = min(vmax_junction, v_allowable);
 159
 160     // Initialize planner efficiency flags
 161     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 162     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 163     // the current block and next block junction speeds are guaranteed to always be at their maximum
 164     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 165     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 166     // the reverse and forward planners, the corresponding block junction speed will always be at the
 167     // the maximum junction speed and may always be ignored for any speed reduction checks.
 168     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 169     else { block->nominal_length_flag = false; }
 170
 171     // Always calculate trapezoid for new block
 172     block->recalculate_flag = true;
 173
 174     // Update previous path unit_vector and nominal speed
 175     memcpy(this->previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 176
 177     // Math-heavy re-computing of the whole queue to take the new
 178     this->recalculate();
 179
 180     // The block can now be used
 181     block->ready();
 182
 183     THEKERNEL->conveyor->queue_head_block();
 184 }
 185
 186 void Planner::recalculate() {
 187     Conveyor::Queue_t &queue = THEKERNEL->conveyor->queue;
 188
 189     unsigned int block_index;
 190
 191     Block* previous;
 192     Block* current;
 193
 194     /*
 195      * a newly added block is decel limited
 196      *
 197      * we find its max entry speed given its exit speed
 198      *
 199      * for each block, walking backwards in the queue:
 200      *
 201      * if max entry speed == current entry speed
 202      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 203      * and thus we don't need to check entry speed for this block any more
 204      *
 205      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 206      *
 207      * for each block, walking forwards in the queue:
 208      *
 209      * given the exit speed of the previous block and our own max entry speed
 210      * we can tell if we're accel or decel limited (or coasting)
 211      *
 212      * if prev_exit > max_entry
 213      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 214      * if max_entry >= prev_exit
 215      *     then we're accel limited. set recalculate to false, work out max exit speed
 216      *
 217      * finally, work out trapezoid for the final (and newest) block.
 218      */
 219
 220     /*
 221      * Step 1:
 222      * For each block, given the exit speed and acceleration, find the maximum entry speed
 223      */
 224
 225     float entry_speed = minimum_planner_speed;
 226
 227     block_index = queue.head_i;
 228     current     = queue.item_ref(block_index);
 229
 230     if (!queue.is_empty())
 231     {
 232         while ((block_index != queue.tail_i) && current->recalculate_flag)
 233         {
 234             entry_speed = current->reverse_pass(entry_speed);
 235
 236             block_index = queue.prev(block_index);
 237             current     = queue.item_ref(block_index);
 238         }
 239
 240         /*
 241          * Step 2:
 242          * now current points to either tail or first non-recalculate block
 243          * and has not had its reverse_pass called
 244          * or its calc trap
 245          * entry_speed is set to the *exit* speed of current.
 246          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 247          */
 248
 249         float exit_speed = current->max_exit_speed();
 250
 251         while (block_index != queue.head_i)
 252         {
 253             previous    = current;
 254             block_index = queue.next(block_index);
 255             current     = queue.item_ref(block_index);
 256
 257             // we pass the exit speed of the previous block
 258             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 259             exit_speed = current->forward_pass(exit_speed);
 260
 261             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 262         }
 263     }
 264
 265     /*
 266      * Step 3:
 267      * work out trapezoid for final (and newest) block
 268      */
 269
 270     // now current points to the head item
 271     // which has not had calculate_trapezoid run yet
 272     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 273 }
 274
 275
 276 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 277 // acceleration within the allotted distance.
 278 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance) {
 279   return(
 280     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
 281   );
 282 }
 283
 284