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