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
  28 #define acceleration_checksum          CHECKSUM("acceleration")
  29 #define z_acceleration_checksum        CHECKSUM("z_acceleration")
  30 #define junction_deviation_checksum    CHECKSUM("junction_deviation")
  31 #define z_junction_deviation_checksum  CHECKSUM("z_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 {
  40     clear_vector_float(this->previous_unit_vec);
  41     config_load();
  42 }
  43
  44 // Configure acceleration
  45 void Planner::config_load()
  46 {
  47     this->acceleration = THEKERNEL->config->value(acceleration_checksum)->by_default(100.0F )->as_number(); // Acceleration is in mm/s^2
  48     this->z_acceleration = THEKERNEL->config->value(z_acceleration_checksum)->by_default(0.0F )->as_number(); // disabled by default
  49
  50     this->junction_deviation = THEKERNEL->config->value(junction_deviation_checksum)->by_default(0.05F)->as_number();
  51     this->z_junction_deviation = THEKERNEL->config->value(z_junction_deviation_checksum)->by_default(-1)->as_number(); // disabled by default
  52     this->minimum_planner_speed = THEKERNEL->config->value(minimum_planner_speed_checksum)->by_default(0.0f)->as_number();
  53 }
  54
  55
  56 // Append a block to the queue, compute it's speed factors
  57 void Planner::append_block( ActuatorCoordinates &actuator_pos, float rate_mm_s, float distance, float unit_vec[] )
  58 {
  59     float acceleration, junction_deviation;
  60
  61     // Create ( recycle ) a new block
  62     Block* block = THEKERNEL->conveyor->queue.head_ref();
  63
  64
  65     // Direction bits
  66     for (size_t i = 0; i < THEKERNEL->robot->actuators.size(); i++) {
  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     uint32_t 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     }
  95     block->steps_event_count = steps_event_count;
  96
  97     block->millimeters = distance;
  98
  99     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
 100     if( distance > 0.0F ) {
 101         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
 102         block->nominal_rate = 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
 113     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 114     // Let a circle be tangent to both previous and current path line segments, where the junction
 115     // deviation is defined as the distance from the junction to the closest edge of the circle,
 116     // colinear with the circle center. The circular segment joining the two paths represents the
 117     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 118     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 119     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 120     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 121     // nonlinearities of both the junction angle and junction velocity.
 122
 123     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 124     // 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.
 125     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 126
 127     if (!THEKERNEL->conveyor->is_queue_empty()) {
 128         float previous_nominal_speed = THEKERNEL->conveyor->queue.item_ref(THEKERNEL->conveyor->queue.prev(THEKERNEL->conveyor->queue.head_i))->nominal_speed;
 129
 130         if (previous_nominal_speed > 0.0F && junction_deviation > 0.0F) {
 131             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 132             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 133             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 134                               - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 135                               - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
 136
 137             // Skip and use default max junction speed for 0 degree acute junction.
 138             if (cos_theta < 0.95F) {
 139                 vmax_junction = min(previous_nominal_speed, block->nominal_speed);
 140                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 141                 if (cos_theta > -0.95F) {
 142                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 143                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 144                     vmax_junction = min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 145                 }
 146             }
 147         }
 148     }
 149     block->max_entry_speed = vmax_junction;
 150
 151     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 152     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 153     block->entry_speed = min(vmax_junction, v_allowable);
 154
 155     // Initialize planner efficiency flags
 156     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 157     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 158     // the current block and next block junction speeds are guaranteed to always be at their maximum
 159     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 160     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 161     // the reverse and forward planners, the corresponding block junction speed will always be at the
 162     // the maximum junction speed and may always be ignored for any speed reduction checks.
 163     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 164     else { block->nominal_length_flag = false; }
 165
 166     // Always calculate trapezoid for new block
 167     block->recalculate_flag = true;
 168
 169     // Update previous path unit_vector and nominal speed
 170     memcpy(this->previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 171
 172     // Math-heavy re-computing of the whole queue to take the new
 173     this->recalculate();
 174
 175     // The block can now be used
 176     block->ready();
 177
 178     THEKERNEL->conveyor->queue_head_block();
 179 }
 180
 181 void Planner::recalculate()
 182 {
 183     Conveyor::Queue_t &queue = THEKERNEL->conveyor->queue;
 184
 185     unsigned int block_index;
 186
 187     Block* previous;
 188     Block* current;
 189
 190     /*
 191      * a newly added block is decel limited
 192      *
 193      * we find its max entry speed given its exit speed
 194      *
 195      * for each block, walking backwards in the queue:
 196      *
 197      * if max entry speed == current entry speed
 198      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 199      * and thus we don't need to check entry speed for this block any more
 200      *
 201      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 202      *
 203      * for each block, walking forwards in the queue:
 204      *
 205      * given the exit speed of the previous block and our own max entry speed
 206      * we can tell if we're accel or decel limited (or coasting)
 207      *
 208      * if prev_exit > max_entry
 209      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 210      * if max_entry >= prev_exit
 211      *     then we're accel limited. set recalculate to false, work out max exit speed
 212      *
 213      * finally, work out trapezoid for the final (and newest) block.
 214      */
 215
 216     /*
 217      * Step 1:
 218      * For each block, given the exit speed and acceleration, find the maximum entry speed
 219      */
 220
 221     float entry_speed = minimum_planner_speed;
 222
 223     block_index = queue.head_i;
 224     current     = queue.item_ref(block_index);
 225
 226     if (!queue.is_empty()) {
 227         while ((block_index != queue.tail_i) && current->recalculate_flag) {
 228             entry_speed = current->reverse_pass(entry_speed);
 229
 230             block_index = queue.prev(block_index);
 231             current     = queue.item_ref(block_index);
 232         }
 233
 234         /*
 235          * Step 2:
 236          * now current points to either tail or first non-recalculate block
 237          * and has not had its reverse_pass called
 238          * or its calculate_trapezoid
 239          * entry_speed is set to the *exit* speed of current.
 240          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 241          */
 242
 243         float exit_speed = current->max_exit_speed();
 244
 245         while (block_index != queue.head_i) {
 246             previous    = current;
 247             block_index = queue.next(block_index);
 248             current     = queue.item_ref(block_index);
 249
 250             // we pass the exit speed of the previous block
 251             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 252             exit_speed = current->forward_pass(exit_speed);
 253
 254             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 255         }
 256     }
 257
 258     /*
 259      * Step 3:
 260      * work out trapezoid for final (and newest) block
 261      */
 262
 263     // now current points to the head item
 264     // which has not had calculate_trapezoid run yet
 265     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 266 }
 267
 268
 269 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 270 // acceleration within the allotted distance.
 271 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance)
 272 {
 273     // Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 274     return(sqrtf(target_velocity * target_velocity - 2.0F * acceleration * distance));
 275 }
 276
 277