grbl-LPC-CoreXY/planner.c
Sonny J ffcc3470a3 Optimized planner re-write. Significantly faster. Full arc support enabled by rotation matrix approach.
- Significant improvements in the planner. Removed or reordered
repetitive and expensive calculations by order of importance:
recalculating unchanged blocks, trig functions [sin(), cos(), tan()],
sqrt(), divides, and multiplications. Blocks long enough for nominal
speed to be guaranteed to be reached ignored by planner. Done by
introducing two uint8_t flags per block. Reduced computational overhead
by an order of magnitude.   - Arc motion generation completely
re-written and optimized. Now runs with acceleration planner. Removed
all but one trig function (atan2) from initialization. Streamlined
computations. Segment target locations generated by vector
transformation and small angle approximation. Arc path correction
implemented for accumulated error of approximation and single precision
calculation of Arduino. Bug fix in message passing.
2011-09-06 19:39:14 -06:00

477 lines
22 KiB
C

/*
planner.c - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Modifications Copyright (c) 2011 Sungeun (Sonny) Jeon
Grbl 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.
Grbl 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.
You should have received a copy of the GNU General Public License
along with Grbl. If not, see <http://www.gnu.org/licenses/>.
*/
/* The ring buffer implementation gleaned from the wiring_serial library by David A. Mellis. */
#include <inttypes.h>
#include <math.h>
#include <stdlib.h>
#include "planner.h"
#include "nuts_bolts.h"
#include "stepper.h"
#include "settings.h"
#include "config.h"
// The number of linear motions that can be in the plan at any give time
#ifdef __AVR_ATmega328P__
#define BLOCK_BUFFER_SIZE 16
#else
#define BLOCK_BUFFER_SIZE 5
#endif
static block_t block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
static volatile uint8_t block_buffer_head; // Index of the next block to be pushed
static volatile uint8_t block_buffer_tail; // Index of the block to process now
static int32_t position[3]; // The current position of the tool in absolute steps
static double previous_unit_vec[3]; // Unit vector of previous path line segment
static double previous_nominal_speed; // Nominal speed of previous path line segment
static uint8_t acceleration_manager_enabled; // Acceleration management active?
#define ONE_MINUTE_OF_MICROSECONDS 60000000.0
// Returns the index of the next block in the ring buffer
static int8_t next_block_index(int8_t block_index) {
return( (block_index + 1) % BLOCK_BUFFER_SIZE );
}
// Returns the index of the previous block in the ring buffer
static int8_t prev_block_index(int8_t block_index) {
block_index--;
if (block_index < 0) { block_index = BLOCK_BUFFER_SIZE-1; }
return(block_index);
}
// Calculates the distance (not time) it takes to accelerate from initial_rate to target_rate using the
// given acceleration:
static double estimate_acceleration_distance(double initial_rate, double target_rate, double acceleration) {
return( (target_rate*target_rate-initial_rate*initial_rate)/(2*acceleration) );
}
/* + <- some maximum rate we don't care about
/|\
/ | \
/ | + <- final_rate
/ | |
initial_rate -> +----+--+
^ ^
| |
intersection_distance distance */
// This function gives you the point at which you must start braking (at the rate of -acceleration) if
// you started at speed initial_rate and accelerated until this point and want to end at the final_rate after
// a total travel of distance. This can be used to compute the intersection point between acceleration and
// deceleration in the cases where the trapezoid has no plateau (i.e. never reaches maximum speed)
static double intersection_distance(double initial_rate, double final_rate, double acceleration, double distance) {
return( (2*acceleration*distance-initial_rate*initial_rate+final_rate*final_rate)/(4*acceleration) );
}
// Calculates the square of the maximum allowable speed at this point when you must be able to reach
// target_velocity using the acceleration within the allotted distance.
// NOTE: sqrt() removed for speed optimization. Related calculations in terms of square velocity.
static double max_allowable_speed_sqr(double acceleration, double target_velocity_sqr, double distance) {
return( target_velocity_sqr-2*acceleration*60*60*distance );
}
// The kernel called by planner_recalculate() when scanning the plan from last to first entry.
static void planner_reverse_pass_kernel(block_t *previous, block_t *current, block_t *next) {
if (!current) { return; }
double entry_speed_sqr = current->max_entry_speed_sqr; // Reset and check to ensure max possible speed
// If nominal length true, nominal speed is guaranteed to be reached. No need to re-compute.
// But, if forward planner changed entry speed, reset to max entry speed just to be sure.
if (!current->nominal_length_flag) {
if (next) {
// If the required deceleration across the block is too rapid, reduce entry_speed_sqr accordingly.
if (entry_speed_sqr > next->entry_speed_sqr) {
entry_speed_sqr = min( entry_speed_sqr,
max_allowable_speed_sqr(-settings.acceleration,next->entry_speed_sqr,current->millimeters));
}
} else {
// Assume last block has zero exit velocity.
entry_speed_sqr = min( entry_speed_sqr,
max_allowable_speed_sqr(-settings.acceleration,0.0,current->millimeters));
}
}
// Check for junction speed change
if (current->entry_speed_sqr != entry_speed_sqr) {
current->entry_speed_sqr = entry_speed_sqr;
current->recalculate_flag = true; // Note: Newest block already set to true
}
}
// planner_recalculate() needs to go over the current plan twice. Once in reverse and once forward. This
// implements the reverse pass.
static void planner_reverse_pass() {
auto int8_t block_index = block_buffer_head;
block_t *block[3] = {NULL, NULL, NULL};
while(block_index != block_buffer_tail) {
block_index = prev_block_index( block_index );
block[2]= block[1];
block[1]= block[0];
block[0] = &block_buffer[block_index];
planner_reverse_pass_kernel(block[0], block[1], block[2]);
}
// Skip buffer tail to prevent over-writing the initial entry speed.
}
// The kernel called by planner_recalculate() when scanning the plan from first to last entry.
static void planner_forward_pass_kernel(block_t *previous, block_t *current, block_t *next) {
if(!current) { return; }
if(previous) {
// If nominal length true, nominal speed is guaranteed to be reached. No need to recalculate.
if (!previous->nominal_length_flag) {
// If the previous block is an acceleration block, but it is not long enough to
// complete the full speed change within the block, we need to adjust the entry
// speed accordingly.
if (previous->entry_speed_sqr < current->entry_speed_sqr) {
double entry_speed_sqr = min( current->entry_speed_sqr, current->max_entry_speed_sqr );
entry_speed_sqr = min( entry_speed_sqr,
max_allowable_speed_sqr(-settings.acceleration,previous->entry_speed_sqr,previous->millimeters) );
// Check for junction speed change
if (current->entry_speed_sqr != entry_speed_sqr) {
current->entry_speed_sqr = entry_speed_sqr;
current->recalculate_flag = true;
}
}
}
}
}
// planner_recalculate() needs to go over the current plan twice. Once in reverse and once forward. This
// implements the forward pass.
static void planner_forward_pass() {
int8_t block_index = block_buffer_tail;
block_t *block[3] = {NULL, NULL, NULL};
while(block_index != block_buffer_head) {
block[0] = block[1];
block[1] = block[2];
block[2] = &block_buffer[block_index];
planner_forward_pass_kernel(block[0],block[1],block[2]);
block_index = next_block_index( block_index );
}
planner_forward_pass_kernel(block[1], block[2], NULL);
}
/* STEPPER RATE DEFINITION
+--------+ <- nominal_rate
/ \
nominal_rate*entry_factor -> + \
| + <- nominal_rate*exit_factor
+-------------+
time -->
*/
// Calculates trapezoid parameters so that the entry- and exit-speed is compensated by the provided factors.
// The factors represent a factor of braking and must be in the range 0.0-1.0.
// This converts the planner parameters to the data required by the stepper controller.
static void calculate_trapezoid_for_block(block_t *block, double entry_factor, double exit_factor) {
block->initial_rate = ceil(block->nominal_rate*entry_factor);
block->final_rate = ceil(block->nominal_rate*exit_factor);
int32_t acceleration_per_minute = block->rate_delta*ACCELERATION_TICKS_PER_SECOND*60.0;
int32_t accelerate_steps =
ceil(estimate_acceleration_distance(block->initial_rate, block->nominal_rate, acceleration_per_minute));
int32_t decelerate_steps =
floor(estimate_acceleration_distance(block->nominal_rate, block->final_rate, -acceleration_per_minute));
// Calculate the size of Plateau of Nominal Rate.
int32_t plateau_steps = block->step_event_count-accelerate_steps-decelerate_steps;
// Is the Plateau of Nominal Rate smaller than nothing? That means no cruising, and we will
// have to use intersection_distance() to calculate when to abort acceleration and start braking
// in order to reach the final_rate exactly at the end of this block.
if (plateau_steps < 0) {
accelerate_steps = ceil(
intersection_distance(block->initial_rate, block->final_rate, acceleration_per_minute, block->step_event_count));
plateau_steps = 0;
}
block->accelerate_until = accelerate_steps;
block->decelerate_after = accelerate_steps+plateau_steps;
}
/* PLANNER SPEED DEFINITION
+--------+ <- current->nominal_speed
/ \
current->entry_speed -> + \
| + <- next->entry_speed
+-------------+
time -->
*/
// Recalculates the trapezoid speed profiles for flagged blocks in the plan according to the
// entry_speed for each junction and the entry_speed of the next junction. Must be called by
// planner_recalculate() after updating the blocks. Any recalulate flagged junction will
// compute the two adjacent trapezoids to the junction, since the junction speed corresponds
// to exit speed and entry speed of one another.
static void planner_recalculate_trapezoids() {
int8_t block_index = block_buffer_tail;
block_t *current;
block_t *next = NULL;
while(block_index != block_buffer_head) {
current = next;
next = &block_buffer[block_index];
if (current) {
// Recalculate if current block entry or exit junction speed has changed.
if (current->recalculate_flag || next->recalculate_flag) {
// Compute entry and exit factors for trapezoid calculations.
// NOTE: sqrt(square velocities) now performed only when required in trapezoid calculation.
double entry_factor = sqrt( current->entry_speed_sqr ) / current->nominal_speed;
double exit_factor = sqrt( next->entry_speed_sqr ) / current->nominal_speed;
calculate_trapezoid_for_block(current, entry_factor, exit_factor);
current->recalculate_flag = false; // Reset current only to ensure next trapezoid is computed
}
}
block_index = next_block_index( block_index );
}
// Last/newest block in buffer. Exit speed is zero.
calculate_trapezoid_for_block(next, sqrt( next->entry_speed_sqr ) / next->nominal_speed, 0.0);
next->recalculate_flag = false;
}
// Recalculates the motion plan according to the following algorithm:
//
// 1. Go over every block in reverse order and calculate a junction speed reduction (i.e. block_t.entry_speed)
// so that:
// a. The junction speed is equal to or less than the maximum junction speed limit
// b. No speed reduction within one block requires faster deceleration than the one, true constant
// acceleration.
// 2. Go over every block in chronological order and dial down junction speed values if
// a. The speed increase within one block would require faster acceleration than the one, true
// constant acceleration.
//
// When these stages are complete all blocks have an entry speed that will allow all speed changes to
// be performed using only the one, true constant acceleration, and where no junction speed is greater
// than the max limit. Finally it will:
//
// 3. Recalculate trapezoids for all blocks using the recently updated junction speeds. Block trapezoids
// with no updated junction speeds will not be recalculated and assumed ok as is.
static void planner_recalculate() {
planner_reverse_pass();
planner_forward_pass();
planner_recalculate_trapezoids();
}
void plan_init() {
block_buffer_head = 0;
block_buffer_tail = 0;
plan_set_acceleration_manager_enabled(true);
clear_vector(position);
clear_vector_double(previous_unit_vec);
previous_nominal_speed = 0.0;
}
void plan_set_acceleration_manager_enabled(uint8_t enabled) {
if ((!!acceleration_manager_enabled) != (!!enabled)) {
st_synchronize();
acceleration_manager_enabled = !!enabled;
}
}
int plan_is_acceleration_manager_enabled() {
return(acceleration_manager_enabled);
}
void plan_discard_current_block() {
if (block_buffer_head != block_buffer_tail) {
block_buffer_tail = next_block_index( block_buffer_tail );
}
}
block_t *plan_get_current_block() {
if (block_buffer_head == block_buffer_tail) { return(NULL); }
return(&block_buffer[block_buffer_tail]);
}
// Add a new linear movement to the buffer. x, y and z is the signed, absolute target position in
// millimaters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
// rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
void plan_buffer_line(double x, double y, double z, double feed_rate, uint8_t invert_feed_rate) {
// Calculate target position in absolute steps
int32_t target[3];
target[X_AXIS] = lround(x*settings.steps_per_mm[X_AXIS]);
target[Y_AXIS] = lround(y*settings.steps_per_mm[Y_AXIS]);
target[Z_AXIS] = lround(z*settings.steps_per_mm[Z_AXIS]);
// Calculate the buffer head after we push this byte
int next_buffer_head = next_block_index( block_buffer_head );
// If the buffer is full: good! That means we are well ahead of the robot.
// Rest here until there is room in the buffer.
while(block_buffer_tail == next_buffer_head) { sleep_mode(); }
// Prepare to set up new block
block_t *block = &block_buffer[block_buffer_head];
// Compute direction bits for this block
block->direction_bits = 0;
if (target[X_AXIS] < position[X_AXIS]) { block->direction_bits |= (1<<X_DIRECTION_BIT); }
if (target[Y_AXIS] < position[Y_AXIS]) { block->direction_bits |= (1<<Y_DIRECTION_BIT); }
if (target[Z_AXIS] < position[Z_AXIS]) { block->direction_bits |= (1<<Z_DIRECTION_BIT); }
// Number of steps for each axis
block->steps_x = labs(target[X_AXIS]-position[X_AXIS]);
block->steps_y = labs(target[Y_AXIS]-position[Y_AXIS]);
block->steps_z = labs(target[Z_AXIS]-position[Z_AXIS]);
block->step_event_count = max(block->steps_x, max(block->steps_y, block->steps_z));
// Bail if this is a zero-length block
if (block->step_event_count == 0) { return; };
// Compute path vector in terms of absolute step target and current positions
double delta_mm[3];
delta_mm[X_AXIS] = (target[X_AXIS]-position[X_AXIS])/settings.steps_per_mm[X_AXIS];
delta_mm[Y_AXIS] = (target[Y_AXIS]-position[Y_AXIS])/settings.steps_per_mm[Y_AXIS];
delta_mm[Z_AXIS] = (target[Z_AXIS]-position[Z_AXIS])/settings.steps_per_mm[Z_AXIS];
block->millimeters = sqrt(square(delta_mm[X_AXIS]) + square(delta_mm[Y_AXIS]) +
square(delta_mm[Z_AXIS]));
uint32_t microseconds;
if (!invert_feed_rate) {
microseconds = lround((block->millimeters/feed_rate)*1000000);
} else {
microseconds = lround(ONE_MINUTE_OF_MICROSECONDS/feed_rate);
}
// Calculate speed in mm/minute for each axis
double multiplier = 60.0*1000000.0/microseconds;
block->speed_x = delta_mm[X_AXIS] * multiplier;
block->speed_y = delta_mm[Y_AXIS] * multiplier;
block->speed_z = delta_mm[Z_AXIS] * multiplier;
block->nominal_speed = block->millimeters * multiplier;
block->nominal_rate = ceil(block->step_event_count * multiplier);
// This is a temporary fix to avoid a situation where very low nominal_speeds would be rounded
// down to zero and cause a division by zero. TODO: Grbl deserves a less patchy fix for this problem
if (block->nominal_speed < 60.0) { block->nominal_speed = 60.0; }
// Compute the acceleration rate for the trapezoid generator. Depending on the slope of the line
// average travel per step event changes. For a line along one axis the travel per step event
// is equal to the travel/step in the particular axis. For a 45 degree line the steppers of both
// axes might step for every step event. Travel per step event is then sqrt(travel_x^2+travel_y^2).
// To generate trapezoids with contant acceleration between blocks the rate_delta must be computed
// specifically for each line to compensate for this phenomenon:
double step_per_travel = block->step_event_count/block->millimeters; // Compute inverse to remove divide
block->rate_delta = step_per_travel * ceil( // convert to: acceleration steps/min/acceleration_tick
settings.acceleration*60.0 / ACCELERATION_TICKS_PER_SECOND ); // acceleration mm/sec/sec per acceleration_tick
// Perform planner-enabled calculations
if (acceleration_manager_enabled) {
// Compute path unit vector
double unit_vec[3];
double inv_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple divides
unit_vec[X_AXIS] = delta_mm[X_AXIS]*inv_millimeters;
unit_vec[Y_AXIS] = delta_mm[Y_AXIS]*inv_millimeters;
unit_vec[Z_AXIS] = delta_mm[Z_AXIS]*inv_millimeters;
// Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
// Does not actually deviate from path, but used as a robust way to compute cornering speeds.
// Let a circle be tangent to both previous and current path line segments, where the junction
// deviation is defined as the distance from the junction to the closest edge of the circle,
// colinear with the circle center. The circular segment joining the two paths represents the
// path of centripetal acceleration. Solve for max velocity based on max acceleration about the
// radius of the circle, defined indirectly by junction deviation. This may be also viewed as
// path width or max_jerk in the previous grbl version.
// NOTE: sqrt() removed for speed optimization. Related calculations in terms of square velocity.
double vmax_junction_sqr = 0.0; // Set default zero max junction speed
// Skip first block or when previous_nominal_speed is used as a flag for homing and offset cycles.
if ((block_buffer_head != block_buffer_tail) && (previous_nominal_speed > 0.0)) {
// Compute cosine of angle between previous and current path. (prev_unit_vec is negative)
// NOTE: Max junction velocity is computed without sin() or acos() by trig half angle identity.
double cos_theta = - previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
- previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
- previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
// Skip and use default zero max junction speed for 0 degree acute junction.
if (cos_theta < 1.0) {
vmax_junction_sqr = square( min(previous_nominal_speed,block->nominal_speed) );
// Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
if (cos_theta > -1.0) {
// Compute maximum junction velocity based on maximum acceleration and junction deviation
double sin_theta_d2 = sqrt(0.5*(1.0-cos_theta)); // Trig half angle identity. Always positive.
vmax_junction_sqr = min(vmax_junction_sqr,
settings.acceleration*60*60 * settings.junction_deviation * sin_theta_d2/(1.0-sin_theta_d2) );
}
}
}
block->max_entry_speed_sqr = vmax_junction_sqr;
block->entry_speed_sqr = vmax_junction_sqr;
// Initialize planner efficiency flags
// Set flag if block will always reach nominal speed regardless of entry/exit speeds.
if (block->nominal_speed <= sqrt(max_allowable_speed_sqr(-settings.acceleration,0.0,0.5*block->millimeters)) )
{ block->nominal_length_flag = true; }
else { block->nominal_length_flag = false; }
block->recalculate_flag = true; // Always calculate trapezoid for new block
// Update previous path unit_vector and nominal speed
memcpy(previous_unit_vec, unit_vec, sizeof(unit_vec)); // previous_unit_vec[] = unit_vec[]
previous_nominal_speed = block->nominal_speed;
} else {
// Acceleration planner disabled. Set minimum that is required.
block->initial_rate = block->nominal_rate;
block->final_rate = block->nominal_rate;
block->accelerate_until = 0;
block->decelerate_after = block->step_event_count;
block->rate_delta = 0;
}
// Move buffer head
block_buffer_head = next_buffer_head;
// Update position
memcpy(position, target, sizeof(target)); // position[] = target[]
if (acceleration_manager_enabled) { planner_recalculate(); }
st_wake_up();
}
// Reset the planner position vector and planner speed
void plan_set_current_position(double x, double y, double z) {
position[X_AXIS] = lround(x*settings.steps_per_mm[X_AXIS]);
position[Y_AXIS] = lround(y*settings.steps_per_mm[Y_AXIS]);
position[Z_AXIS] = lround(z*settings.steps_per_mm[Z_AXIS]);
previous_nominal_speed = 0.0;
}