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 #include <StepTicker.h>
  26
  27 #include <math.h>
  28 #include <algorithm>
  29
  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     memset(this->previous_unit_vec, 0, sizeof this->previous_unit_vec);
  41     config_load();
  42 }
  43
  44 // Configure acceleration
  45 void Planner::config_load()
  46 {
  47     this->junction_deviation = THEKERNEL->config->value(junction_deviation_checksum)->by_default(0.05F)->as_number();
  48     this->z_junction_deviation = THEKERNEL->config->value(z_junction_deviation_checksum)->by_default(NAN)->as_number(); // disabled by default
  49     this->minimum_planner_speed = THEKERNEL->config->value(minimum_planner_speed_checksum)->by_default(0.0f)->as_number();
  50 }
  51
  52
  53 // Append a block to the queue, compute it's speed factors
  54 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)
  55 {
  56     // Create ( recycle ) a new block
  57     Block* block = THECONVEYOR->queue.head_ref();
  58
  59     // Direction bits
  60     bool has_steps = false;
  61     for (size_t i = 0; i < n_motors; i++) {
  62         int32_t steps = THEROBOT->actuators[i]->steps_to_target(actuator_pos[i]);
  63         // Update current position
  64         if(steps != 0) {
  65             THEROBOT->actuators[i]->update_last_milestones(actuator_pos[i], steps);
  66             has_steps = true;
  67         }
  68
  69         // find direction
  70         block->direction_bits[i] = (steps < 0) ? 1 : 0;
  71         // save actual steps in block
  72         block->steps[i] = labs(steps);
  73     }
  74
  75     // sometimes even though there is a detectable movement it turns out there are no steps to be had from such a small move
  76     if(!has_steps) {
  77         block->clear();
  78         return false;
  79     }
  80
  81     // info needed by laser
  82     block->s_value = roundf(s_value*(1<<11)); // 1.11 fixed point
  83     block->is_g123 = g123;
  84
  85     // use default JD
  86     float junction_deviation = this->junction_deviation;
  87
  88     // use either regular junction deviation or z specific and see if a primary axis move
  89     block->primary_axis = true;
  90     if(block->steps[ALPHA_STEPPER] == 0 && block->steps[BETA_STEPPER] == 0) {
  91         if(block->steps[GAMMA_STEPPER] != 0) {
  92             // z only move
  93             if(!isnan(this->z_junction_deviation)) junction_deviation = this->z_junction_deviation;
  94
  95         } else {
  96             // is not a primary axis move
  97             block->primary_axis= false;
  98             #if N_PRIMARY_AXIS > 3
  99                 for (int i = 3; i < N_PRIMARY_AXIS; ++i) {
 100                     if(block->steps[i] != 0){
 101                         block->primary_axis= true;
 102                         break;
 103                     }
 104                 }
 105             #endif
 106
 107         }
 108     }
 109
 110     // Max number of steps, for all axes
 111     auto mi = std::max_element(block->steps.begin(), block->steps.end());
 112     block->steps_event_count = *mi;
 113     block->millimeters = distance;
 114
 115     // check that acceleration/sec does not exceed step frequency
 116     float acceleration_per_second = (acceleration * block->steps_event_count) / block->millimeters;
 117     if(acceleration_per_second > THEKERNEL->step_ticker->get_frequency()) {
 118         // we need to reduce acceleration to keep it under this frequency
 119         acceleration= floorf((block->millimeters * THEKERNEL->step_ticker->get_frequency()) / block->steps_event_count);
 120     }
 121
 122     block->acceleration = acceleration; // save in block
 123
 124     // Calculate speed in mm/sec for each axis. No divide by zero due to previous checks.
 125     if( distance > 0.0F ) {
 126         block->nominal_speed = rate_mm_s;           // (mm/s) Always > 0
 127         block->nominal_rate = block->steps_event_count * rate_mm_s / distance; // (step/s) Always > 0
 128         // must be >= 1.0 step/sec otherwise timing is off
 129         if(block->nominal_rate < 1.0F) block->nominal_rate= 1.0F;
 130
 131     } else {
 132         block->nominal_speed = 0.0F;
 133         block->nominal_rate  = 0;
 134     }
 135
 136     // Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
 137     // average travel per step event changes. For a line along one axis the travel per step event
 138     // is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
 139     // axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
 140
 141     // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
 142     // Let a circle be tangent to both previous and current path line segments, where the junction
 143     // deviation is defined as the distance from the junction to the closest edge of the circle,
 144     // colinear with the circle center. The circular segment joining the two paths represents the
 145     // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
 146     // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
 147     // path width or max_jerk in the previous grbl version. This approach does not actually deviate
 148     // from path, but used as a robust way to compute cornering speeds, as it takes into account the
 149     // nonlinearities of both the junction angle and junction velocity.
 150
 151     // NOTE however it does not take into account independent axis, in most cartesian X and Y and Z are totally independent
 152     // 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.
 153     float vmax_junction = minimum_planner_speed; // Set default max junction speed
 154
 155     // if unit_vec was null then it was not a primary axis move so we skip the junction deviation stuff
 156     if (unit_vec != nullptr && !THECONVEYOR->is_queue_empty()) {
 157         Block *prev_block = THECONVEYOR->queue.item_ref(THECONVEYOR->queue.prev(THECONVEYOR->queue.head_i));
 158         float previous_nominal_speed = prev_block->primary_axis ? prev_block->nominal_speed : 0;
 159
 160         if (junction_deviation > 0.0F && previous_nominal_speed > 0.0F) {
 161             // Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
 162             // NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
 163             float cos_theta = - this->previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
 164                               - this->previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
 165                               - this->previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS];
 166             #if N_PRIMARY_AXIS > 3
 167                 for (int i = 3; i < N_PRIMARY_AXIS; ++i) {
 168                     cos_theta -= this->previous_unit_vec[i] * unit_vec[i];
 169                 }
 170             #endif
 171
 172             // Skip and use default max junction speed for 0 degree acute junction.
 173             if (cos_theta < 0.95F) {
 174                 vmax_junction = std::min(previous_nominal_speed, block->nominal_speed);
 175                 // Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
 176                 if (cos_theta > -0.95F) {
 177                     // Compute maximum junction velocity based on maximum acceleration and junction deviation
 178                     float sin_theta_d2 = sqrtf(0.5F * (1.0F - cos_theta)); // Trig half angle identity. Always positive.
 179                     vmax_junction = std::min(vmax_junction, sqrtf(acceleration * junction_deviation * sin_theta_d2 / (1.0F - sin_theta_d2)));
 180                 }
 181             }
 182         }
 183     }
 184     block->max_entry_speed = vmax_junction;
 185
 186     // Initialize block entry speed. Compute based on deceleration to user-defined minimum_planner_speed.
 187     float v_allowable = max_allowable_speed(-acceleration, minimum_planner_speed, block->millimeters);
 188     block->entry_speed = std::min(vmax_junction, v_allowable);
 189
 190     // Initialize planner efficiency flags
 191     // Set flag if block will always reach maximum junction speed regardless of entry/exit speeds.
 192     // If a block can de/ac-celerate from nominal speed to zero within the length of the block, then
 193     // the current block and next block junction speeds are guaranteed to always be at their maximum
 194     // junction speeds in deceleration and acceleration, respectively. This is due to how the current
 195     // block nominal speed limits both the current and next maximum junction speeds. Hence, in both
 196     // the reverse and forward planners, the corresponding block junction speed will always be at the
 197     // the maximum junction speed and may always be ignored for any speed reduction checks.
 198     if (block->nominal_speed <= v_allowable) { block->nominal_length_flag = true; }
 199     else { block->nominal_length_flag = false; }
 200
 201     // Always calculate trapezoid for new block
 202     block->recalculate_flag = true;
 203
 204     // Update previous path unit_vector and nominal speed
 205     if(unit_vec != nullptr) {
 206         memcpy(previous_unit_vec, unit_vec, sizeof(previous_unit_vec)); // previous_unit_vec[] = unit_vec[]
 207     } else {
 208         memset(previous_unit_vec, 0, sizeof(previous_unit_vec));
 209     }
 210
 211     // Math-heavy re-computing of the whole queue to take the new
 212     this->recalculate();
 213
 214     // The block can now be used
 215     block->ready();
 216
 217     THECONVEYOR->queue_head_block();
 218
 219     return true;
 220 }
 221
 222 void Planner::recalculate()
 223 {
 224     Conveyor::Queue_t &queue = THECONVEYOR->queue;
 225
 226     unsigned int block_index;
 227
 228     Block* previous;
 229     Block* current;
 230
 231     /*
 232      * a newly added block is decel limited
 233      *
 234      * we find its max entry speed given its exit speed
 235      *
 236      * for each block, walking backwards in the queue:
 237      *
 238      * if max entry speed == current entry speed
 239      * then we can set recalculate to false, since clearly adding another block didn't allow us to enter faster
 240      * and thus we don't need to check entry speed for this block any more
 241      *
 242      * once we find an accel limited block, we must find the max exit speed and walk the queue forwards
 243      *
 244      * for each block, walking forwards in the queue:
 245      *
 246      * given the exit speed of the previous block and our own max entry speed
 247      * we can tell if we're accel or decel limited (or coasting)
 248      *
 249      * if prev_exit > max_entry
 250      *     then we're still decel limited. update previous trapezoid with our max entry for prev exit
 251      * if max_entry >= prev_exit
 252      *     then we're accel limited. set recalculate to false, work out max exit speed
 253      *
 254      * finally, work out trapezoid for the final (and newest) block.
 255      */
 256
 257     /*
 258      * Step 1:
 259      * For each block, given the exit speed and acceleration, find the maximum entry speed
 260      */
 261
 262     float entry_speed = minimum_planner_speed;
 263
 264     block_index = queue.head_i;
 265     current     = queue.item_ref(block_index);
 266
 267     if (!queue.is_empty()) {
 268         while ((block_index != queue.tail_i) && current->recalculate_flag) {
 269             entry_speed = current->reverse_pass(entry_speed);
 270
 271             block_index = queue.prev(block_index);
 272             current     = queue.item_ref(block_index);
 273         }
 274
 275         /*
 276          * Step 2:
 277          * now current points to either tail or first non-recalculate block
 278          * and has not had its reverse_pass called
 279          * or its calculate_trapezoid
 280          * entry_speed is set to the *exit* speed of current.
 281          * each block from current to head has its entry speed set to its max entry speed- limited by decel or nominal_rate
 282          */
 283
 284         float exit_speed = current->max_exit_speed();
 285
 286         while (block_index != queue.head_i) {
 287             previous    = current;
 288             block_index = queue.next(block_index);
 289             current     = queue.item_ref(block_index);
 290
 291             // we pass the exit speed of the previous block
 292             // so this block can decide if it's accel or decel limited and update its fields as appropriate
 293             exit_speed = current->forward_pass(exit_speed);
 294
 295             previous->calculate_trapezoid(previous->entry_speed, current->entry_speed);
 296         }
 297     }
 298
 299     /*
 300      * Step 3:
 301      * work out trapezoid for final (and newest) block
 302      */
 303
 304     // now current points to the head item
 305     // which has not had calculate_trapezoid run yet
 306     current->calculate_trapezoid(current->entry_speed, minimum_planner_speed);
 307 }
 308
 309
 310 // Calculates the maximum allowable speed at this point when you must be able to reach target_velocity using the
 311 // acceleration within the allotted distance.
 312 float Planner::max_allowable_speed(float acceleration, float target_velocity, float distance)
 313 {
 314     // Was acceleration*60*60*distance, in case this breaks, but here we prefer to use seconds instead of minutes
 315     return(sqrtf(target_velocity * target_velocity - 2.0F * acceleration * distance));
 316 }
 317
 318