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 "ConfigValue.h"
  25
  26 #include <math.h>
  27 #include <algorithm>
  28
  29 #define junction_deviation_checksum    CHECKSUM("junction_deviation")
  30 #define z_junction_deviation_checksum  CHECKSUM("z_junction_deviation")
  31 #define minimum_planner_speed_checksum CHECKSUM("minimum_planner_speed")
  32
  33 // The Planner does the acceleration math for the queue of Blocks ( movements ).
  34 // It makes sure the speed stays within the configured constraints ( acceleration, junction_deviation, etc )
  35 // It goes over the list in both direction, every time a block is added, re-doing the math to make sure everything is optimal
  36
  37 Planner::Planner()
  38 {
  39     memset(this->previous_unit_vec, 0, sizeof this->previous_unit_vec);
  40     config_load();
  41 }
  42
  43 // Configure acceleration
  44 void Planner::config_load()
  45 {
  46     this->junction_deviation = THEKERNEL->config->value(junction_deviation_checksum)->by_default(0.05F)->as_number();
  47     this->z_junction_deviation = THEKERNEL->config->value(z_junction_deviation_checksum)->by_default(NAN)->as_number(); // disabled by default
  48     this->minimum_planner_speed = THEKERNEL->config->value(minimum_planner_speed_checksum)->by_default(0.0f)->as_number();
  49 }
  50
  51
  52 // Append a block to the queue, compute it's speed factors
  53 void Planner::append_block( ActuatorCoordinates &actuator_pos, uint8_t n_motors, float rate_mm_s, float distance, float *unit_vec, float acceleration)
  54 {
  55     // Create ( recycle ) a new block
  56     Block* block = THECONVEYOR->queue.head_ref();
  57
  58     // Direction bits
  59     for (size_t i = 0; i < n_motors; i++) {
  60         int32_t steps = THEROBOT->actuators[i]->steps_to_target(actuator_pos[i]);
  61         // Update current position
  62         THEROBOT->actuators[i]->update_last_milestones(actuator_pos[i], steps);
  63
  64         // find direction
  65         block->direction_bits[i] = (steps < 0) ? 1 : 0;
  66
  67         // save actual steps in block
  68         block->steps[i] = labs(steps);
  69     }
  70
  71     // use default JD
  72     float junction_deviation = this->junction_deviation;
  73
  74     // use either regular junction deviation or z specific and see if a primary axis move
  75     block->primary_axis= true;
  76     if(block->steps[ALPHA_STEPPER] == 0 && block->steps[BETA_STEPPER] == 0){
  77         if(block->steps[GAMMA_STEPPER] != 0) {
  78             // z only move
  79             if(!isnan(this->z_junction_deviation)) junction_deviation = this->z_junction_deviation;
  80         }else{
  81             // is not a primary axis move
  82             block->primary_axis= false;
  83         }
  84     }
  85
  86     block->acceleration = acceleration; // save in block
  87
  88     // Max number of steps, for all axes
  89     auto mi= std::max_element(block->steps.begin(), block->steps.end());
  90     block->steps_event_count = *mi;
  91
  92     block->millimeters = distance;
  93
  94     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
  95     if( distance > 0.0F ) {
  96         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
  97         block->nominal_rate = block->steps_event_count * rate_mm_s / distance; // (step/s) Always > 0
  98     } else {
  99         block->nominal_speed = 0.0F;
 100         block->nominal_rate  = 0;
 101     }
 102
 103     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
 104     // average travel per step event changes. For a line along one axis the travel per step event
 105     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
 106     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
 107
 108     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 109     // Let a circle be tangent to both previous and current path line segments, where the junction
 110     // deviation is defined as the distance from the junction to the closest edge of the circle,
 111     // colinear with the circle center. The circular segment joining the two paths represents the
 112     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 113     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 114     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 115     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 116     // nonlinearities of both the junction angle and junction velocity.
 117
 118     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 119     // 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.
 120     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 121
 122     // if unit_vec was null then it was not a primary axis move so we skip the junction deviation stuff
 123     if (unit_vec != nullptr && !THECONVEYOR->is_queue_empty()) {
 124         Block *prev_block= THECONVEYOR->queue.item_ref(THECONVEYOR->queue.prev(THECONVEYOR->queue.head_i));
 125         float previous_nominal_speed = prev_block->primary_axis ? prev_block->nominal_speed : 0;
 126
 127         if (junction_deviation > 0.0F && previous_nominal_speed > 0.0F) {
 128             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 129             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 130             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 131                               - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 132                               - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 133
 134             // Skip and use default max junction speed for 0 degree acute junction.
 135             if (cos_theta < 0.95F) {
 136                 vmax_junction = std::min(previous_nominal_speed, block->nominal_speed);
 137                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 138                 if (cos_theta > -0.95F) {
 139                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 140                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 141                     vmax_junction = std::min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 142                 }
 143             }
 144         }
 145     }
 146     block->max_entry_speed = vmax_junction;
 147
 148     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 149     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 150     block->entry_speed = std::min(vmax_junction, v_allowable);
 151
 152     // Initialize planner efficiency flags
 153     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 154     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 155     // the current block and next block junction speeds are guaranteed to always be at their maximum
 156     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 157     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 158     // the reverse and forward planners, the corresponding block junction speed will always be at the
 159     // the maximum junction speed and may always be ignored for any speed reduction checks.
 160     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 161     else { block->nominal_length_flag = false; }
 162
 163     // Always calculate trapezoid for new block
 164     block->recalculate_flag = true;
 165
 166     // Update previous path unit_vector and nominal speed
 167     if(unit_vec != nullptr) {
 168         memcpy(previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 169     }else{
 170         memset(previous_unit_vec, 0, sizeof(previous_unit_vec));
 171     }
 172
 173     // Math-heavy re-computing of the whole queue to take the new
 174     this->recalculate();
 175
 176     // The block can now be used
 177     block->ready();
 178
 179     THECONVEYOR->queue_head_block();
 180 }
 181
 182 void Planner::recalculate()
 183 {
 184     Conveyor::Queue_t &queue = THECONVEYOR->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         while ((block_index != queue.tail_i) && current->recalculate_flag) {
 229             entry_speed = current->reverse_pass(entry_speed);
 230
 231             block_index = queue.prev(block_index);
 232             current     = queue.item_ref(block_index);
 233         }
 234
 235         /*
 236          * Step 2:
 237          * now current points to either tail or first non-recalculate block
 238          * and has not had its reverse_pass called
 239          * or its calculate_trapezoid
 240          * entry_speed is set to the *exit* speed of current.
 241          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 242          */
 243
 244         float exit_speed = current->max_exit_speed();
 245
 246         while (block_index != queue.head_i) {
 247             previous    = current;
 248             block_index = queue.next(block_index);
 249             current     = queue.item_ref(block_index);
 250
 251             // we pass the exit speed of the previous block
 252             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 253             exit_speed = current->forward_pass(exit_speed);
 254
 255             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 256         }
 257     }
 258
 259     /*
 260      * Step 3:
 261      * work out trapezoid for final (and newest) block
 262      */
 263
 264     // now current points to the head item
 265     // which has not had calculate_trapezoid run yet
 266     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 267 }
 268
 269
 270 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 271 // acceleration within the allotted distance.
 272 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance)
 273 {
 274     // Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 275     return(sqrtf(target_velocity * target_velocity - 2.0F * acceleration * distance));
 276 }
 277
 278