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 bool Planner::append_block( ActuatorCoordinates &actuator_pos, uint8_t n_motors, float rate_mm_s, float distance, float *unit_vec, float acceleration, float s_value, bool g123)
  54 {
  55     // Create ( recycle ) a new block
  56     Block* block = THECONVEYOR->queue.head_ref();
  57
  58     // Direction bits
  59     bool has_steps = false;
  60     for (size_t i = 0; i < n_motors; i++) {
  61         int32_t steps = THEROBOT->actuators[i]->steps_to_target(actuator_pos[i]);
  62         // Update current position
  63         if(steps != 0) {
  64             THEROBOT->actuators[i]->update_last_milestones(actuator_pos[i], steps);
  65             has_steps = true;
  66         }
  67
  68         // find direction
  69         block->direction_bits[i] = (steps < 0) ? 1 : 0;
  70         // save actual steps in block
  71         block->steps[i] = labs(steps);
  72     }
  73
  74     // sometimes even though there is a detectable movement it turns out there are no steps to be had from such a small move
  75     if(!has_steps) {
  76         block->clear();
  77         return false;
  78     }
  79
  80     // info needed by laser
  81     block->s_value = roundf(s_value*(1<<11)); // 1.11 fixed point
  82     block->is_g123 = g123;
  83
  84     // use default JD
  85     float junction_deviation = this->junction_deviation;
  86
  87     // use either regular junction deviation or z specific and see if a primary axis move
  88     block->primary_axis = true;
  89     if(block->steps[ALPHA_STEPPER] == 0 && block->steps[BETA_STEPPER] == 0) {
  90         if(block->steps[GAMMA_STEPPER] != 0) {
  91             // z only move
  92             if(!isnan(this->z_junction_deviation)) junction_deviation = this->z_junction_deviation;
  93
  94         } else {
  95             // is not a primary axis move
  96             block->primary_axis= false;
  97             #if N_PRIMARY_AXIS > 3
  98                 for (int i = 3; i < N_PRIMARY_AXIS; ++i) {
  99                     if(block->steps[i] != 0){
 100                         block->primary_axis= true;
 101                         break;
 102                     }
 103                 }
 104             #endif
 105
 106         }
 107     }
 108
 109     block->acceleration = acceleration; // save in block
 110
 111     // Max number of steps, for all axes
 112     auto mi = std::max_element(block->steps.begin(), block->steps.end());
 113     block->steps_event_count = *mi;
 114
 115     block->millimeters = distance;
 116
 117     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
 118     if( distance > 0.0F ) {
 119         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
 120         block->nominal_rate = block->steps_event_count * rate_mm_s / distance; // (step/s) Always > 0
 121     } else {
 122         block->nominal_speed = 0.0F;
 123         block->nominal_rate  = 0;
 124     }
 125
 126     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
 127     // average travel per step event changes. For a line along one axis the travel per step event
 128     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
 129     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
 130
 131     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 132     // Let a circle be tangent to both previous and current path line segments, where the junction
 133     // deviation is defined as the distance from the junction to the closest edge of the circle,
 134     // colinear with the circle center. The circular segment joining the two paths represents the
 135     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 136     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 137     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 138     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 139     // nonlinearities of both the junction angle and junction velocity.
 140
 141     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 142     // 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.
 143     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 144
 145     // if unit_vec was null then it was not a primary axis move so we skip the junction deviation stuff
 146     if (unit_vec != nullptr && !THECONVEYOR->is_queue_empty()) {
 147         Block *prev_block = THECONVEYOR->queue.item_ref(THECONVEYOR->queue.prev(THECONVEYOR->queue.head_i));
 148         float previous_nominal_speed = prev_block->primary_axis ? prev_block->nominal_speed : 0;
 149
 150         if (junction_deviation > 0.0F && previous_nominal_speed > 0.0F) {
 151             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 152             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 153             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 154                               - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 155                               - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS];
 156             #if N_PRIMARY_AXIS > 3
 157                 for (int i = 3; i < N_PRIMARY_AXIS; ++i) {
 158                     cos_theta -= this->previous_unit_vec[i] * unit_vec[i];
 159                 }
 160             #endif
 161
 162             // Skip and use default max junction speed for 0 degree acute junction.
 163             if (cos_theta < 0.95F) {
 164                 vmax_junction = std::min(previous_nominal_speed, block->nominal_speed);
 165                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 166                 if (cos_theta > -0.95F) {
 167                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 168                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 169                     vmax_junction = std::min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 170                 }
 171             }
 172         }
 173     }
 174     block->max_entry_speed = vmax_junction;
 175
 176     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 177     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 178     block->entry_speed = std::min(vmax_junction, v_allowable);
 179
 180     // Initialize planner efficiency flags
 181     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 182     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 183     // the current block and next block junction speeds are guaranteed to always be at their maximum
 184     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 185     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 186     // the reverse and forward planners, the corresponding block junction speed will always be at the
 187     // the maximum junction speed and may always be ignored for any speed reduction checks.
 188     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 189     else { block->nominal_length_flag = false; }
 190
 191     // Always calculate trapezoid for new block
 192     block->recalculate_flag = true;
 193
 194     // Update previous path unit_vector and nominal speed
 195     if(unit_vec != nullptr) {
 196         memcpy(previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 197     } else {
 198         memset(previous_unit_vec, 0, sizeof(previous_unit_vec));
 199     }
 200
 201     // Math-heavy re-computing of the whole queue to take the new
 202     this->recalculate();
 203
 204     // The block can now be used
 205     block->ready();
 206
 207     THECONVEYOR->queue_head_block();
 208
 209     return true;
 210 }
 211
 212 void Planner::recalculate()
 213 {
 214     Conveyor::Queue_t &queue = THECONVEYOR->queue;
 215
 216     unsigned int block_index;
 217
 218     Block* previous;
 219     Block* current;
 220
 221     /*
 222      * a newly added block is decel limited
 223      *
 224      * we find its max entry speed given its exit speed
 225      *
 226      * for each block, walking backwards in the queue:
 227      *
 228      * if max entry speed == current entry speed
 229      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 230      * and thus we don't need to check entry speed for this block any more
 231      *
 232      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 233      *
 234      * for each block, walking forwards in the queue:
 235      *
 236      * given the exit speed of the previous block and our own max entry speed
 237      * we can tell if we're accel or decel limited (or coasting)
 238      *
 239      * if prev_exit > max_entry
 240      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 241      * if max_entry >= prev_exit
 242      *     then we're accel limited. set recalculate to false, work out max exit speed
 243      *
 244      * finally, work out trapezoid for the final (and newest) block.
 245      */
 246
 247     /*
 248      * Step 1:
 249      * For each block, given the exit speed and acceleration, find the maximum entry speed
 250      */
 251
 252     float entry_speed = minimum_planner_speed;
 253
 254     block_index = queue.head_i;
 255     current     = queue.item_ref(block_index);
 256
 257     if (!queue.is_empty()) {
 258         while ((block_index != queue.tail_i) && current->recalculate_flag) {
 259             entry_speed = current->reverse_pass(entry_speed);
 260
 261             block_index = queue.prev(block_index);
 262             current     = queue.item_ref(block_index);
 263         }
 264
 265         /*
 266          * Step 2:
 267          * now current points to either tail or first non-recalculate block
 268          * and has not had its reverse_pass called
 269          * or its calculate_trapezoid
 270          * entry_speed is set to the *exit* speed of current.
 271          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 272          */
 273
 274         float exit_speed = current->max_exit_speed();
 275
 276         while (block_index != queue.head_i) {
 277             previous    = current;
 278             block_index = queue.next(block_index);
 279             current     = queue.item_ref(block_index);
 280
 281             // we pass the exit speed of the previous block
 282             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 283             exit_speed = current->forward_pass(exit_speed);
 284
 285             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 286         }
 287     }
 288
 289     /*
 290      * Step 3:
 291      * work out trapezoid for final (and newest) block
 292      */
 293
 294     // now current points to the head item
 295     // which has not had calculate_trapezoid run yet
 296     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 297 }
 298
 299
 300 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 301 // acceleration within the allotted distance.
 302 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance)
 303 {
 304     // Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 305     return(sqrtf(target_velocity * target_velocity - 2.0F * acceleration * distance));
 306 }
 307
 308