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Push old dev_2 draft to work on other things.

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- **NON-FUNCTIONAL**
- Contains an old draft of separating the stepper driver direct access
to the planner buffer. This is designed to keep the stepper and planner
modules independent and prevent overwriting or other complications. In
this way, feedrate override should be able to be installed as well.
- A number of planner optimizations are installed too.
- Not sure where the bugs are. Either in the new planner optimizations,
new stepper module updates, or in both. Or it just could be that the
Arduino AVR is choking with the new things it has to do.
This commit is contained in:
Sonny Jeon
2013-08-19 09:24:22 -06:00
parent 1fa3dad206
commit 7a175bd2db
23 changed files with 3160 additions and 704 deletions
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577
planner.c
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@@ -2,8 +2,8 @@
planner.c - buffers movement commands and manages the acceleration profile plan
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Copyright (c) 2011-2013 Sungeun K. Jeon
Copyright (c) 2009-2011 Simen Svale Skogsrud
Copyright (c) 2011 Jens Geisler
Grbl is free software: you can redistribute it and/or modify
@@ -34,11 +34,11 @@
#define SOME_LARGE_VALUE 1.0E+38 // Used by rapids and acceleration maximization calculations. Just needs
// to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
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 plan_block_t block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
static volatile uint8_t block_buffer_tail; // Index of the block to process now
static uint8_t block_buffer_head; // Index of the next block to be pushed
static uint8_t next_buffer_head; // Index of the next buffer head
// static *block_t block_buffer_planned;
static uint8_t block_buffer_planned; // Index of the optimally planned block
// Define planner variables
typedef struct {
@@ -47,7 +47,6 @@ typedef struct {
// i.e. arcs, canned cycles, and backlash compensation.
float previous_unit_vec[N_AXIS]; // Unit vector of previous path line segment
float previous_nominal_speed_sqr; // Nominal speed of previous path line segment
float last_x, last_y, last_z; // Target position of previous path line segment
} planner_t;
static planner_t pl;
@@ -69,65 +68,7 @@ static uint8_t prev_block_index(uint8_t block_index)
block_index--;
return(block_index);
}
/* STEPPER VELOCITY PROFILE DEFINITION
less than nominal rate-> +
+--------+ <- nominal_rate /|\
/ \ / | \
initial_rate -> + \ / | + <- next->initial_rate
| + <- next->initial_rate / | |
+-------------+ initial_rate -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate distance decelerate distance
Calculates trapezoid parameters for stepper algorithm. Each block velocity profiles can be
described as either a trapezoidal or a triangular shape. The trapezoid occurs when the block
reaches the nominal speed of the block and cruises for a period of time. A triangle occurs
when the nominal speed is not reached within the block. Some other special cases exist,
such as pure ac/de-celeration velocity profiles from beginning to end or a trapezoid that
has no deceleration period when the next block resumes acceleration.
The following function determines the type of velocity profile and stores the minimum required
information for the stepper algorithm to execute the calculated profiles. In this case, only
the new initial rate and n_steps until deceleration are computed, since the stepper algorithm
already handles acceleration and cruising and just needs to know when to start decelerating.
*/
static void calculate_trapezoid_for_block(block_t *block, float entry_speed_sqr, float exit_speed_sqr)
{
// Compute new initial rate for stepper algorithm
block->initial_rate = ceil(sqrt(entry_speed_sqr)*(RANADE_MULTIPLIER/(60*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// TODO: Compute new nominal rate if a feedrate override occurs.
// block->nominal_rate = ceil(feed_rate*(RANADE_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
// Compute efficiency variable for following calculations. Removes a float divide and multiply.
// TODO: If memory allows, this can be kept in the block buffer since it doesn't change, even after feed holds.
float steps_per_mm_div_2_acc = block->step_event_count/(2*block->acceleration*block->millimeters);
// First determine intersection distance (in steps) from the exit point for a triangular profile.
// Computes: steps_intersect = steps/mm * ( distance/2 + (v_entry^2-v_exit^2)/(4*acceleration) )
int32_t intersect_distance = ceil( 0.5*(block->step_event_count + steps_per_mm_div_2_acc*(entry_speed_sqr-exit_speed_sqr)) );
// Check if this is a pure acceleration block by a intersection distance less than zero. Also
// prevents signed and unsigned integer conversion errors.
if (intersect_distance <= 0) {
block->decelerate_after = 0;
} else {
// Determine deceleration distance (in steps) from nominal speed to exit speed for a trapezoidal profile.
// Value is never negative. Nominal speed is always greater than or equal to the exit speed.
// Computes: steps_decelerate = steps/mm * ( (v_nominal^2 - v_exit^2)/(2*acceleration) )
block->decelerate_after = ceil(steps_per_mm_div_2_acc * (block->nominal_speed_sqr - exit_speed_sqr));
// The lesser of the two triangle and trapezoid distances always defines the velocity profile.
if (block->decelerate_after > intersect_distance) { block->decelerate_after = intersect_distance; }
// Finally, check if this is a pure deceleration block.
if (block->decelerate_after > block->step_event_count) { block->decelerate_after = block->step_event_count; }
}
}
/* PLANNER SPEED DEFINITION
+--------+ <- current->nominal_speed
@@ -185,178 +126,130 @@ static void calculate_trapezoid_for_block(block_t *block, float entry_speed_sqr,
*/
static void planner_recalculate()
{
// float entry_speed_sqr;
// uint8_t block_index = block_buffer_head;
// block_t *previous = NULL;
// block_t *current = NULL;
// block_t *next;
// while (block_index != block_buffer_tail) {
// block_index = prev_block_index( block_index );
// next = current;
// current = previous;
// previous = &block_buffer[block_index];
//
// if (next && current) {
// if (next != block_buffer_planned) {
// if (previous == block_buffer_tail) { block_buffer_planned = next; }
// else {
//
// if (current->entry_speed_sqr != current->max_entry_speed_sqr) {
// current->recalculate_flag = true; // Almost always changes. So force recalculate.
// entry_speed_sqr = next->entry_speed_sqr + 2*current->acceleration*current->millimeters;
// if (entry_speed_sqr < current->max_entry_speed_sqr) {
// current->entry_speed_sqr = entry_speed_sqr;
// } else {
// current->entry_speed_sqr = current->max_entry_speed_sqr;
// }
// } else {
// block_buffer_planned = current;
// }
// }
// } else {
// break;
// }
// }
// }
//
// block_index = block_buffer_planned;
// next = &block_buffer[block_index];
// current = prev_block_index(block_index);
// while (block_index != block_buffer_head) {
//
// // If the current 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 exit speed accordingly. Entry
// // speeds have already been reset, maximized, and reverse planned by reverse planner.
// if (current->entry_speed_sqr < next->entry_speed_sqr) {
// // Compute block exit speed based on the current block speed and distance
// // Computes: v_exit^2 = v_entry^2 + 2*acceleration*distance
// entry_speed_sqr = current->entry_speed_sqr + 2*current->acceleration*current->millimeters;
//
// // If it's less than the stored value, update the exit speed and set recalculate flag.
// if (entry_speed_sqr < next->entry_speed_sqr) {
// next->entry_speed_sqr = entry_speed_sqr;
// next->recalculate_flag = true;
// }
// }
//
// // Recalculate if current block entry or exit junction speed has changed.
// if (current->recalculate_flag || next->recalculate_flag) {
// // NOTE: Entry and exit factors always > 0 by all previous logic operations.
// calculate_trapezoid_for_block(current, current->entry_speed_sqr, next->entry_speed_sqr);
// current->recalculate_flag = false; // Reset current only to ensure next trapezoid is computed
// }
//
// current = next;
// next = &block_buffer[block_index];
// block_index = next_block_index( block_index );
// }
//
// // Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
// calculate_trapezoid_for_block(next, next->entry_speed_sqr, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
// next->recalculate_flag = false;
// Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
uint8_t block_index = block_buffer_head;
plan_block_t *current = &block_buffer[block_index]; // Set as last/newest block in buffer
// TODO: No over-write protection exists for the executing block. For most cases this has proven to be ok, but
// for feed-rate overrides, something like this is essential. Place a request here to the stepper driver to
// find out where in the planner buffer is the a safe place to begin re-planning from.
// Ping the stepper algorithm to check if we can alter the parameters of the currently executing
// block. If not, skip it and work on the next block.
// TODO: Need to look into if there are conditions where this fails.
uint8_t block_buffer_safe = next_block_index( block_buffer_tail );
// TODO: Need to recompute buffer tail millimeters based on how much is completed.
if (block_buffer_safe == next_buffer_head) { // Only one safe block in buffer to operate on
// if (block_buffer_head != block_buffer_tail) {
float entry_speed_sqr;
block_buffer_planned = block_buffer_safe;
// calculate_trapezoid_for_block(current, 0.0, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
// Perform reverse planner pass. Skip the head(end) block since it is already initialized, and skip the
// tail(first) block to prevent over-writing of the initial entry speed.
uint8_t block_index = prev_block_index( block_buffer_head ); // Assume buffer is not empty.
block_t *current = &block_buffer[block_index]; // Head block-1 = Newly appended block
block_t *next;
if (block_index != block_buffer_tail) { block_index = prev_block_index( block_index ); }
while (block_index != block_buffer_tail) {
next = current;
current = &block_buffer[block_index];
// TODO: Determine maximum entry speed at junction for feedrate overrides, since they can alter
// the planner nominal speeds at any time. This calc could be done in the override handler, but
// this could require an additional variable to be stored to differentiate the programmed nominal
// speeds, max junction speed, and override speeds/scalar.
// If entry speed is already at the maximum entry speed, no need to recheck. Block is cruising.
// If not, block in state of acceleration or deceleration. Reset entry speed to maximum and
// check for maximum allowable speed reductions to ensure maximum possible planned speed.
if (current->entry_speed_sqr != current->max_entry_speed_sqr) {
} else {
// TODO: need to account for the two block condition better. If the currently executing block
// is not safe, do we wait until its done? Can we treat the buffer head differently?
// Calculate trapezoid for the last/newest block.
current->entry_speed_sqr = min( current->max_entry_speed_sqr,
MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED + 2*current->acceleration*current->millimeters);
// calculate_trapezoid_for_block(current, current->entry_speed_sqr, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
current->entry_speed_sqr = current->max_entry_speed_sqr;
current->recalculate_flag = true; // Almost always changes. So force recalculate.
if (next->entry_speed_sqr < current->max_entry_speed_sqr) {
// Computes: v_entry^2 = v_exit^2 + 2*acceleration*distance
// Reverse Pass: Back plan the deceleration curve from the last block in buffer. Cease
// planning when: (1) the last optimal planned pointer is reached. (2) the safe block
// pointer is reached, whereby the planned pointer is updated.
float entry_speed_sqr;
plan_block_t *next;
block_index = prev_block_index(block_index);
while (block_index != block_buffer_planned) {
next = current;
current = &block_buffer[block_index];
// Exit loop and update planned pointer when the tail/safe block is reached.
if (block_index == block_buffer_safe) {
block_buffer_planned = block_buffer_safe;
break;
}
// Crudely maximize deceleration curve from the end of the non-optimally planned buffer to
// the optimal plan pointer. Forward pass will adjust and finish optimizing the plan.
if (current->entry_speed_sqr != current->max_entry_speed_sqr) {
entry_speed_sqr = next->entry_speed_sqr + 2*current->acceleration*current->millimeters;
if (entry_speed_sqr < current->max_entry_speed_sqr) {
current->entry_speed_sqr = entry_speed_sqr;
} else {
current->entry_speed_sqr = current->max_entry_speed_sqr;
}
}
}
block_index = prev_block_index( block_index );
}
}
block_index = prev_block_index(block_index);
}
// Perform forward planner pass. Begins junction speed adjustments after tail(first) block.
// Also recalculate trapezoids, block by block, as the forward pass completes the plan.
block_index = next_block_index(block_buffer_tail);
next = &block_buffer[block_buffer_tail]; // Places tail(first) block into current
while (block_index != block_buffer_head) {
current = next;
next = &block_buffer[block_index];
// If the current 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 exit speed accordingly. Entry
// speeds have already been reset, maximized, and reverse planned by reverse planner.
// Forward Pass: Forward plan the acceleration curve from the planned pointer onward.
// Also scans for optimal plan breakpoints and appropriately updates the planned pointer.
block_index = block_buffer_planned; // Begin at buffer planned pointer
next = &block_buffer[prev_block_index(block_buffer_planned)]; // Set up for while loop
while (block_index != next_buffer_head) {
current = next;
next = &block_buffer[block_index];
// Any acceleration detected in the forward pass automatically moves the optimal planned
// pointer forward, since everything before this is all optimal. In other words, nothing
// can improve the plan from the buffer tail to the planned pointer by logic.
if (current->entry_speed_sqr < next->entry_speed_sqr) {
// Compute block exit speed based on the current block speed and distance
// Computes: v_exit^2 = v_entry^2 + 2*acceleration*distance
block_buffer_planned = block_index;
entry_speed_sqr = current->entry_speed_sqr + 2*current->acceleration*current->millimeters;
// If it's less than the stored value, update the exit speed and set recalculate flag.
if (entry_speed_sqr < next->entry_speed_sqr) {
next->entry_speed_sqr = entry_speed_sqr;
next->recalculate_flag = true;
next->entry_speed_sqr = entry_speed_sqr; // Always <= max_entry_speed_sqr. Backward pass set this.
}
}
// Recalculate if current block entry or exit junction speed has changed.
if (current->recalculate_flag || next->recalculate_flag) {
// NOTE: Entry and exit factors always > 0 by all previous logic operations.
calculate_trapezoid_for_block(current, current->entry_speed_sqr, next->entry_speed_sqr);
current->recalculate_flag = false; // Reset current only to ensure next trapezoid is computed
// Any block set at its maximum entry speed also creates an optimal plan up to this
// point in the buffer. The optimally planned pointer is updated.
if (next->entry_speed_sqr == next->max_entry_speed_sqr) {
block_buffer_planned = block_index;
}
block_index = next_block_index( block_index );
}
// Automatically recalculate trapezoid for all buffer blocks from last plan's optimal planned
// pointer to the end of the buffer, except the last block.
// calculate_trapezoid_for_block(current, current->entry_speed_sqr, next->entry_speed_sqr);
block_index = next_block_index( block_index );
}
}
// Last/newest block in buffer. Exit speed is set with MINIMUM_PLANNER_SPEED. Always recalculated.
calculate_trapezoid_for_block(next, next->entry_speed_sqr, MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED);
next->recalculate_flag = false;
// }
}
void plan_init()
{
block_buffer_head = 0;
block_buffer_tail = block_buffer_head;
next_buffer_head = next_block_index(block_buffer_head);
// block_buffer_planned = block_buffer_head;
block_buffer_planned = block_buffer_head;
memset(&pl, 0, sizeof(pl)); // Clear planner struct
}
inline void plan_discard_current_block()
void plan_discard_current_block()
{
if (block_buffer_head != block_buffer_tail) {
block_buffer_tail = next_block_index( block_buffer_tail );
}
}
inline block_t *plan_get_current_block()
plan_block_t *plan_get_current_block()
{
if (block_buffer_head == block_buffer_tail) { return(NULL); }
return(&block_buffer[block_buffer_tail]);
}
plan_block_t *plan_get_block_by_index(uint8_t block_index)
{
if (block_buffer_head == block_index) { return(NULL); }
return(&block_buffer[block_index]);
}
// Returns the availability status of the block ring buffer. True, if full.
uint8_t plan_check_full_buffer()
{
@@ -364,6 +257,7 @@ uint8_t plan_check_full_buffer()
return(false);
}
// Block until all buffered steps are executed or in a cycle state. Works with feed hold
// during a synchronize call, if it should happen. Also, waits for clean cycle end.
void plan_synchronize()
@@ -374,43 +268,54 @@ void plan_synchronize()
}
}
// Add a new linear movement to the buffer. x, y and z is the signed, absolute target position in
// millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
// Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position
// in millimeters. 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.
// All position data passed to the planner must be in terms of machine position to keep the planner
// independent of any coordinate system changes and offsets, which are handled by the g-code parser.
// NOTE: Assumes buffer is available. Buffer checks are handled at a higher level by motion_control.
// Also the feed rate input value is used in three ways: as a normal feed rate if invert_feed_rate
// is false, as inverse time if invert_feed_rate is true, or as seek/rapids rate if the feed_rate
// value is negative (and invert_feed_rate always false).
void plan_buffer_line(float x, float y, float z, float feed_rate, uint8_t invert_feed_rate)
// In other words, the buffer head is never equal to the buffer tail. Also the feed rate input value
// is used in three ways: as a normal feed rate if invert_feed_rate is false, as inverse time if
// invert_feed_rate is true, or as seek/rapids rate if the feed_rate value is negative (and
// invert_feed_rate always false).
void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
{
// Prepare to set up new block
block_t *block = &block_buffer[block_buffer_head];
// Prepare and initialize new block
plan_block_t *block = &block_buffer[block_buffer_head];
block->step_event_count = 0;
block->millimeters = 0;
block->direction_bits = 0;
block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
// Calculate target position in absolute steps
int32_t target[N_AXIS];
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]);
// Compute and store initial move distance data.
int32_t target_steps[N_AXIS];
float unit_vec[N_AXIS], delta_mm;
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
// Calculate target position in absolute steps. This conversion should be consistent throughout.
target_steps[idx] = lround(target[idx]*settings.steps_per_mm[idx]);
// Number of steps for each axis and determine max step events
block->steps[idx] = labs(target_steps[idx]-pl.position[idx]);
block->step_event_count = max(block->step_event_count, block->steps[idx]);
// Compute individual axes distance for move and prep unit vector calculations.
// NOTE: Computes true distance from converted step values.
delta_mm = (target_steps[idx] - pl.position[idx])/settings.steps_per_mm[idx];
unit_vec[idx] = delta_mm; // Store unit vector numerator. Denominator computed later.
// Set direction bits. Bit enabled always means direction is negative.
if (delta_mm < 0 ) { block->direction_bits |= get_direction_mask(idx); }
// Incrementally compute total move distance by Euclidean norm. First add square of each term.
block->millimeters += delta_mm*delta_mm;
}
block->millimeters = sqrt(block->millimeters); // Complete millimeters calculation with sqrt()
// Number of steps for each axis
block->steps_x = labs(target[X_AXIS]-pl.position[X_AXIS]);
block->steps_y = labs(target[Y_AXIS]-pl.position[Y_AXIS]);
block->steps_z = labs(target[Z_AXIS]-pl.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; };
if (block->step_event_count == 0) { return; }
// Compute path vector in terms of absolute step target and current positions
float delta_mm[N_AXIS];
delta_mm[X_AXIS] = x-pl.last_x;
delta_mm[Y_AXIS] = y-pl.last_y;
delta_mm[Z_AXIS] = z-pl.last_z;
block->millimeters = sqrt(delta_mm[X_AXIS]*delta_mm[X_AXIS] + delta_mm[Y_AXIS]*delta_mm[Y_AXIS] +
delta_mm[Z_AXIS]*delta_mm[Z_AXIS]);
// Adjust feed_rate value to mm/min depending on type of rate input (normal, inverse time, or rapids)
// TODO: Need to distinguish a rapids vs feed move for overrides. Some flag of some sort.
if (feed_rate < 0) { feed_rate = SOME_LARGE_VALUE; } // Scaled down to absolute max/rapids rate later
@@ -422,117 +327,151 @@ void plan_buffer_line(float x, float y, float z, float feed_rate, uint8_t invert
// and axes properties as well.
// NOTE: This calculation assumes all axes are orthogonal (Cartesian) and works with ABC-axes,
// if they are also orthogonal/independent. Operates on the absolute value of the unit vector.
uint8_t i;
float unit_vec[N_AXIS], inverse_unit_vec_value;
float inverse_unit_vec_value;
float inverse_millimeters = 1.0/block->millimeters; // Inverse millimeters to remove multiple float divides
block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration in loop
for (i=0; i<N_AXIS; i++) {
if (delta_mm[i] == 0) {
unit_vec[i] = 0; // Store zero value. And avoid divide by zero.
} else {
// Compute unit vector and its absolute inverse value
unit_vec[i] = delta_mm[i]*inverse_millimeters;
inverse_unit_vec_value = abs(1.0/unit_vec[i]);
// Check and limit feed rate against max axis velocities and scale accelerations to maximums
feed_rate = min(feed_rate,settings.max_velocity[i]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[i]*inverse_unit_vec_value);
float junction_cos_theta = 0;
for (idx=0; idx<N_AXIS; idx++) {
if (unit_vec[idx] != 0) { // Avoid divide by zero.
unit_vec[idx] *= inverse_millimeters; // Complete unit vector calculation
inverse_unit_vec_value = abs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
// Check and limit feed rate against max individual axis velocities and accelerations
feed_rate = min(feed_rate,settings.max_velocity[idx]*inverse_unit_vec_value);
block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
// Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
// between the current move and the previous move is simply the dot product of the two unit vectors,
// where prev_unit_vec is negative. Used later to compute maximum junction speed.
junction_cos_theta -= pl.previous_unit_vec[idx] * unit_vec[idx];
}
}
// Compute nominal speed and rates
block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min)^2. Always > 0
block->nominal_rate = ceil(feed_rate*(RANADE_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
/* Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
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. This approach does not actually deviate
from path, but used as a robust way to compute cornering speeds, as it takes into account the
nonlinearities of both the junction angle and junction velocity.
NOTE: If the junction deviation value is finite, Grbl executes the motions in an exact path
mode (G61). If the junction deviation value is zero, Grbl will execute the motion in an exact
stop mode (G61.1) manner. In the future, if continuous mode (G64) is desired, the math here
is exactly the same. Instead of motioning all the way to junction point, the machine will
just follow the arc circle defined here. The Arduino doesn't have the CPU cycles to perform
a continuous mode path, but ARM-based microcontrollers most certainly do.
*/
// TODO: Acceleration need to be limited by the minimum of the two junctions.
// TODO: Need to setup a method to handle zero junction speeds when starting from rest.
if (block_buffer_head == block_buffer_tail) {
block->max_entry_speed_sqr = MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED;
} else {
// NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
float sin_theta_d2 = sqrt(0.5*(1.0-junction_cos_theta)); // Trig half angle identity. Always positive.
block->max_entry_speed_sqr = (block->acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2);
}
// Compute the acceleration and distance traveled per step event for the stepper algorithm.
block->rate_delta = ceil(block->acceleration*
((RANADE_MULTIPLIER/(60.0*60.0))/(ISR_TICKS_PER_SECOND*ACCELERATION_TICKS_PER_SECOND))); // (mult*mm/isr_tic/accel_tic)
block->d_next = ceil((block->millimeters*RANADE_MULTIPLIER)/block->step_event_count); // (mult*mm/step)
// Compute direction bits. Bit enabled always means direction is negative.
block->direction_bits = 0;
if (unit_vec[X_AXIS] < 0) { block->direction_bits |= (1<<X_DIRECTION_BIT); }
if (unit_vec[Y_AXIS] < 0) { block->direction_bits |= (1<<Y_DIRECTION_BIT); }
if (unit_vec[Z_AXIS] < 0) { block->direction_bits |= (1<<Z_DIRECTION_BIT); }
// Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
// 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. This approach does not actually deviate
// from path, but used as a robust way to compute cornering speeds, as it takes into account the
// nonlinearities of both the junction angle and junction velocity.
// NOTE: If the junction deviation value is finite, Grbl executes the motions in an exact path
// mode (G61). If the junction deviation value is zero, Grbl will execute the motion in an exact
// stop mode (G61.1) manner. In the future, if continuous mode (G64) is desired, the math here
// is exactly the same. Instead of motioning all the way to junction point, the machine will
// just follow the arc circle defined here. The Arduino doesn't have the CPU cycles to perform
// a continuous mode path, but ARM-based microcontrollers most certainly do.
// Skip first block or when previous_nominal_speed is used as a flag for homing and offset cycles.
block->max_entry_speed_sqr = MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED;
if ((block_buffer_head != block_buffer_tail) && (pl.previous_nominal_speed_sqr > 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.
float cos_theta = - pl.previous_unit_vec[X_AXIS] * unit_vec[X_AXIS]
- pl.previous_unit_vec[Y_AXIS] * unit_vec[Y_AXIS]
- pl.previous_unit_vec[Z_AXIS] * unit_vec[Z_AXIS] ;
// Skip and use default max junction speed for 0 degree acute junction.
if (cos_theta < 0.95) {
block->max_entry_speed_sqr = min(block->nominal_speed_sqr,pl.previous_nominal_speed_sqr);
// Skip and avoid divide by zero for straight junctions at 180 degrees. Limit to min() of nominal speeds.
if (cos_theta > -0.95) {
// Compute maximum junction velocity based on maximum acceleration and junction deviation
float sin_theta_d2 = sqrt(0.5*(1.0-cos_theta)); // Trig half angle identity. Always positive.
block->max_entry_speed_sqr = min(block->max_entry_speed_sqr,
block->acceleration * settings.junction_deviation * sin_theta_d2/(1.0-sin_theta_d2));
}
}
}
// Initialize block entry speed. Compute block entry velocity backwards from user-defined MINIMUM_PLANNER_SPEED.
// TODO: This could be moved to the planner recalculate function.
block->entry_speed_sqr = min( block->max_entry_speed_sqr,
MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED + 2*block->acceleration*block->millimeters);
// Set new block to be recalculated for conversion to stepper data.
block->recalculate_flag = true;
// Store block nominal speed and rate
block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min). Always > 0
// block->nominal_rate = ceil(feed_rate*(INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))); // (mult*mm/isr_tic)
//
// // Compute and store acceleration and distance traveled per step event.
// block->rate_delta = ceil(block->acceleration*
// ((INV_TIME_MULTIPLIER/(60.0*60.0))/(ISR_TICKS_PER_SECOND*ACCELERATION_TICKS_PER_SECOND))); // (mult*mm/isr_tic/accel_tic)
// block->d_next = ceil((block->millimeters*INV_TIME_MULTIPLIER)/block->step_event_count); // (mult*mm/step)
// Update previous path unit_vector and nominal speed (squared)
memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
// Update planner position
memcpy(pl.position, target, sizeof(target)); // pl.position[] = target[]
pl.last_x = x;
pl.last_y = y;
pl.last_z = z;
// Update buffer head and next buffer head indices
block_buffer_head = next_buffer_head;
next_buffer_head = next_block_index(block_buffer_head);
memcpy(pl.position, target_steps, sizeof(target_steps)); // pl.position[] = target_steps[]
planner_recalculate();
// Update buffer head and next buffer head indices.
// NOTE: The buffer head update is atomic since it's one byte. Performed after the new plan
// calculations to help prevent overwriting scenarios with adding a new block to a low buffer.
block_buffer_head = next_buffer_head;
next_buffer_head = next_block_index(block_buffer_head);
}
// Reset the planner position vectors. Called by the system abort/initialization routine.
void plan_set_current_position(int32_t x, int32_t y, int32_t z)
void plan_sync_position()
{
pl.position[X_AXIS] = x;
pl.position[Y_AXIS] = y;
pl.position[Z_AXIS] = z;
pl.last_x = x/settings.steps_per_mm[X_AXIS];
pl.last_y = y/settings.steps_per_mm[Y_AXIS];
pl.last_z = z/settings.steps_per_mm[Z_AXIS];
uint8_t idx;
for (idx=0; idx<N_AXIS; idx++) {
pl.position[idx] = sys.position[idx];
}
}
/* STEPPER VELOCITY PROFILE DEFINITION
less than nominal rate-> +
+--------+ <- nominal_rate /|\
/ \ / | \
initial_rate -> + \ / | + <- next->initial_rate
| + <- next->initial_rate / | |
+-------------+ initial_rate -> +----+--+
time --> ^ ^ ^ ^
| | | |
decelerate distance decelerate distance
Calculates trapezoid parameters for stepper algorithm. Each block velocity profiles can be
described as either a trapezoidal or a triangular shape. The trapezoid occurs when the block
reaches the nominal speed of the block and cruises for a period of time. A triangle occurs
when the nominal speed is not reached within the block. Some other special cases exist,
such as pure ac/de-celeration velocity profiles from beginning to end or a trapezoid that
has no deceleration period when the next block resumes acceleration.
The following function determines the type of velocity profile and stores the minimum required
information for the stepper algorithm to execute the calculated profiles. In this case, only
the new initial rate and n_steps until deceleration are computed, since the stepper algorithm
already handles acceleration and cruising and just needs to know when to start decelerating.
*/
int32_t calculate_trapezoid_for_block(uint8_t block_index)
{
plan_block_t *current_block = &block_buffer[block_index];
// Determine current block exit speed
float exit_speed_sqr;
uint8_t next_index = next_block_index(block_index);
plan_block_t *next_block = plan_get_block_by_index(next_index);
if (next_block == NULL) { exit_speed_sqr = 0; } // End of planner buffer. Zero speed.
else { exit_speed_sqr = next_block->entry_speed_sqr; } // Entry speed of next block
// First determine intersection distance (in steps) from the exit point for a triangular profile.
// Computes: steps_intersect = steps/mm * ( distance/2 + (v_entry^2-v_exit^2)/(4*acceleration) )
float intersect_distance = 0.5*( current_block->millimeters + (current_block->entry_speed_sqr-exit_speed_sqr)/(2*current_block->acceleration) );
// Check if this is a pure acceleration block by a intersection distance less than zero. Also
// prevents signed and unsigned integer conversion errors.
if (intersect_distance > 0 ) {
float decelerate_distance;
// Determine deceleration distance (in steps) from nominal speed to exit speed for a trapezoidal profile.
// Value is never negative. Nominal speed is always greater than or equal to the exit speed.
// Computes: steps_decelerate = steps/mm * ( (v_nominal^2 - v_exit^2)/(2*acceleration) )
decelerate_distance = (current_block->nominal_speed_sqr - exit_speed_sqr)/(2*current_block->acceleration);
// The lesser of the two triangle and trapezoid distances always defines the velocity profile.
if (decelerate_distance > intersect_distance) { decelerate_distance = intersect_distance; }
// Finally, check if this is a pure deceleration block.
if (decelerate_distance > current_block->millimeters) { decelerate_distance = current_block->millimeters; }
return(ceil(((current_block->millimeters-decelerate_distance)*current_block->step_event_count)/ current_block->millimeters));
}
return(0);
}
// Re-initialize buffer plan with a partially completed block, assumed to exist at the buffer tail.
// Called after a steppers have come to a complete stop for a feed hold and the cycle is stopped.
void plan_cycle_reinitialize(int32_t step_events_remaining)
{
block_t *block = &block_buffer[block_buffer_tail]; // Point to partially completed block
plan_block_t *block = &block_buffer[block_buffer_tail]; // Point to partially completed block
// Only remaining millimeters and step_event_count need to be updated for planner recalculate.
// Other variables (step_x, step_y, step_z, rate_delta, etc.) all need to remain the same to
@@ -540,9 +479,9 @@ void plan_cycle_reinitialize(int32_t step_events_remaining)
block->millimeters = (block->millimeters*step_events_remaining)/block->step_event_count;
block->step_event_count = step_events_remaining;
// Re-plan from a complete stop. Reset planner entry speeds and flags.
// Re-plan from a complete stop. Reset planner entry speeds and buffer planned pointer.
block->entry_speed_sqr = 0.0;
block->max_entry_speed_sqr = 0.0;
block->recalculate_flag = true;
block->max_entry_speed_sqr = MINIMUM_PLANNER_SPEED*MINIMUM_PLANNER_SPEED;
block_buffer_planned = block_buffer_tail;
planner_recalculate();
}