ManuelW/grbl-LPC-CoreXY
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Deceleration to zero speed improvements. Update defaults.

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- A minor issue with deceleration ramps when close to zero velocity.
Should be virtually unnoticeable for most CNC systems, but fixed in
this push and accurate to physics.

- Updated some of the junction deviation defaults. Because the new
stepper algorithm can easily maximize a CNC machine’s capabilities or
simply go much faster, this means the speed in which it enters
junctions has to be a little more constrained. Meaning that, we have to
slow a little bit down more so that we don’t exceed the acceleration
limits of the stepper motors.
This commit is contained in:
Sonny Jeon 2013-12-07 20:08:24 -07:00
parent a87f25773c
commit b562845d9d
2 changed files with 51 additions and 38 deletions
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14
defaults.h
View File

@ -45,7 +45,7 @@
#define DEFAULT_FEEDRATE 250.0 // mm/min #define DEFAULT_FEEDRATE 250.0 // mm/min
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled) #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm #define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3 #define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 0 // false #define DEFAULT_REPORT_INCHES 0 // false
@ -83,7 +83,7 @@
#define DEFAULT_FEEDRATE 254.0 // mm/min (10 ipm) #define DEFAULT_FEEDRATE 254.0 // mm/min (10 ipm)
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled) #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm #define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3 #define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 1 // true #define DEFAULT_REPORT_INCHES 1 // true
@ -153,17 +153,17 @@
#define DEFAULT_X_MAX_RATE 7000.0 // mm/min #define DEFAULT_X_MAX_RATE 7000.0 // mm/min
#define DEFAULT_Y_MAX_RATE 7000.0 // mm/min #define DEFAULT_Y_MAX_RATE 7000.0 // mm/min
#define DEFAULT_Z_MAX_RATE 7000.0 // mm/min #define DEFAULT_Z_MAX_RATE 7000.0 // mm/min
#define DEFAULT_X_ACCELERATION (500.0*60*60) // 10 mm/min^2 #define DEFAULT_X_ACCELERATION (600.0*60*60) // 10 mm/min^2
#define DEFAULT_Y_ACCELERATION (500.0*60*60) // 10 mm/min^2 #define DEFAULT_Y_ACCELERATION (600.0*60*60) // 10 mm/min^2
#define DEFAULT_Z_ACCELERATION (500.0*60*60) // 10 mm/min^2 #define DEFAULT_Z_ACCELERATION (600.0*60*60) // 10 mm/min^2
#define DEFAULT_X_MAX_TRAVEL 200.0 // mm #define DEFAULT_X_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Y_MAX_TRAVEL 200.0 // mm #define DEFAULT_Y_MAX_TRAVEL 200.0 // mm
#define DEFAULT_Z_MAX_TRAVEL 200.0 // mm #define DEFAULT_Z_MAX_TRAVEL 200.0 // mm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10 #define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_FEEDRATE 1000.0 // mm/min #define DEFAULT_FEEDRATE 1000.0 // mm/min
#define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT)|(1<<Z_DIRECTION_BIT)) #define DEFAULT_STEPPING_INVERT_MASK ((1<<Y_DIRECTION_BIT))
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled) #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_JUNCTION_DEVIATION 0.05 // mm #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
#define DEFAULT_ARC_TOLERANCE 0.005 // mm #define DEFAULT_ARC_TOLERANCE 0.005 // mm
#define DEFAULT_DECIMAL_PLACES 3 #define DEFAULT_DECIMAL_PLACES 3
#define DEFAULT_REPORT_INCHES 0 // false #define DEFAULT_REPORT_INCHES 0 // false

61
stepper.c
View File

@ -107,7 +107,7 @@ typedef struct {
float steps_remaining; float steps_remaining;
uint8_t ramp_type; // Current segment ramp state uint8_t ramp_type; // Current segment ramp state
float mm_eob; float mm_complete;
float current_speed; // Current speed at the end of the segment buffer (mm/min) float current_speed; // Current speed at the end of the segment buffer (mm/min)
float maximum_speed; // Maximum speed of executing block. Not always nominal speed. (mm/min) float maximum_speed; // Maximum speed of executing block. Not always nominal speed. (mm/min)
float exit_speed; // Exit speed of executing block (mm/min) float exit_speed; // Exit speed of executing block (mm/min)
@ -491,8 +491,13 @@ void st_prep_buffer()
else { prep.current_speed = sqrt(pl_block->entry_speed_sqr); } else { prep.current_speed = sqrt(pl_block->entry_speed_sqr); }
} }
prep.mm_eob = 0.0; /* ---------------------------------------------------------------------------------
Compute the velocity profile of a new planner block based on its entry and exit
speeds, or recompute the profile of a partially-completed planner block if the
planner has updated it. For a commanded forced-deceleration, such as from a feed
hold, override the planner velocities and decelerate to the target exit speed.
*/
prep.mm_complete = 0.0;
float inv_2_accel = 0.5/pl_block->acceleration; float inv_2_accel = 0.5/pl_block->acceleration;
if (sys.state == STATE_HOLD) { if (sys.state == STATE_HOLD) {
// Compute velocity profile parameters for a feed hold in-progress. This profile overrides // Compute velocity profile parameters for a feed hold in-progress. This profile overrides
@ -501,12 +506,12 @@ void st_prep_buffer()
float decel_dist = inv_2_accel*pl_block->entry_speed_sqr; float decel_dist = inv_2_accel*pl_block->entry_speed_sqr;
if (decel_dist < pl_block->millimeters) { if (decel_dist < pl_block->millimeters) {
prep.exit_speed = 0.0; prep.exit_speed = 0.0;
prep.mm_eob = pl_block->millimeters-decel_dist; prep.mm_complete = pl_block->millimeters-decel_dist;
} else { } else {
prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*pl_block->millimeters); prep.exit_speed = sqrt(pl_block->entry_speed_sqr-2*pl_block->acceleration*pl_block->millimeters);
} }
} else { } else {
// Compute velocity profile parameters of the prepped planner block. // Compute or recompute velocity profile parameters of the prepped planner block.
prep.ramp_type = RAMP_ACCEL; // Initialize as acceleration ramp. prep.ramp_type = RAMP_ACCEL; // Initialize as acceleration ramp.
prep.accelerate_until = pl_block->millimeters; prep.accelerate_until = pl_block->millimeters;
prep.exit_speed = plan_get_exec_block_exit_speed(); prep.exit_speed = plan_get_exec_block_exit_speed();
@ -550,24 +555,31 @@ void st_prep_buffer()
// Set new segment to point to the current segment data block. // Set new segment to point to the current segment data block.
prep_segment->st_block_index = prep.st_block_index; prep_segment->st_block_index = prep.st_block_index;
/* ----------------------------------------------------------------------------------- /*------------------------------------------------------------------------------------
Compute the average velocity of this new segment by determining the total distance Compute the average velocity of this new segment by determining the total distance
traveled over the segment time DT_SEGMENT. The following code first attempts to create traveled over the segment time DT_SEGMENT. The following code first attempts to create
a full segment based on the current ramp conditions. If the segment time is incomplete a full segment based on the current ramp conditions. If the segment time is incomplete
when terminating at a ramp state change, the code will continue to loop through the when terminating at a ramp state change, the code will continue to loop through the
progressing ramp states to fill the remaining segment execution time. However, if progressing ramp states to fill the remaining segment execution time. However, if
an incomplete segment terminates at the end of the planner block, the segment is an incomplete segment terminates at the end of the velocity profile, the segment is
considered completed despite having a truncated execution time less than DT_SEGMENT. considered completed despite having a truncated execution time less than DT_SEGMENT.
The velocity profile is always assumed to progress through the ramp sequence:
acceleration ramp, cruising state, and deceleration ramp. Each ramp's travel distance
may range from zero to the length of the block. Velocity profiles can end either at
the end of planner block (typical) or mid-block at the end of a forced deceleration,
such as from a feed hold.
*/ */
float dt = 0.0; float dt = 0.0;
float mm_remaining = pl_block->millimeters; float mm_remaining = pl_block->millimeters;
float time_var = DT_SEGMENT; // Time worker variable float time_var = DT_SEGMENT; // Time worker variable
float mm_var; // mm distance worker variable float mm_var; // mm-Distance worker variable
float speed_var; // Speed work variable.
do { do {
switch (prep.ramp_type) { switch (prep.ramp_type) {
case RAMP_ACCEL: case RAMP_ACCEL:
// NOTE: Acceleration ramp only computes during first do-while loop. // NOTE: Acceleration ramp only computes during first do-while loop.
mm_remaining -= DT_SEGMENT*(prep.current_speed + pl_block->acceleration*(0.5*DT_SEGMENT)); speed_var = pl_block->acceleration*DT_SEGMENT;
mm_remaining -= DT_SEGMENT*(prep.current_speed + 0.5*speed_var);
if (mm_remaining < prep.accelerate_until) { // End of acceleration ramp. if (mm_remaining < prep.accelerate_until) { // End of acceleration ramp.
// Acceleration-cruise, acceleration-deceleration ramp junction, or end of block. // Acceleration-cruise, acceleration-deceleration ramp junction, or end of block.
mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
@ -576,7 +588,7 @@ void st_prep_buffer()
else { prep.ramp_type = RAMP_CRUISE; } else { prep.ramp_type = RAMP_CRUISE; }
prep.current_speed = prep.maximum_speed; prep.current_speed = prep.maximum_speed;
} else { // Acceleration only. } else { // Acceleration only.
prep.current_speed += pl_block->acceleration*time_var; prep.current_speed += speed_var;
} }
break; break;
case RAMP_CRUISE: case RAMP_CRUISE:
@ -592,23 +604,24 @@ void st_prep_buffer()
} }
break; break;
default: // case RAMP_DECEL: default: // case RAMP_DECEL:
// NOTE: mm_var used to catch negative decelerate distance values near zero speed. // NOTE: mm_var used as a misc worker variable to prevent errors when near zero speed.
mm_var = time_var*(prep.current_speed - 0.5*pl_block->acceleration*time_var); speed_var = pl_block->acceleration*time_var; // Used as delta speed (mm/min)
if ((mm_var > prep.mm_eob) && (mm_var < mm_remaining)) { // Deceleration only. if (prep.current_speed > speed_var) { // Check if at or below zero speed.
prep.current_speed -= pl_block->acceleration*time_var; // Compute distance from end of segment to end of block.
// Check for near-zero speed and prevent divide by zero in rare scenarios. mm_var = mm_remaining - time_var*(prep.current_speed - 0.5*speed_var); // (mm)
if (prep.current_speed > prep.exit_speed) { mm_remaining -= mm_var; } if (mm_var > prep.mm_complete) { // Deceleration only.
else { mm_remaining = prep.mm_eob; } // NOTE: Force EOB for now. May or may not be needed. mm_remaining = mm_var;
} else { // End of block. prep.current_speed -= speed_var;
time_var = 2.0*(mm_remaining-prep.mm_eob)/(prep.current_speed+prep.exit_speed); break; // Segment complete. Exit switch-case statement.
mm_remaining = prep.mm_eob;
// prep.current_speed = prep.exit_speed; // !! May be needed for feed hold reinitialization.
} }
} // End of block or end of forced-deceleration.
time_var = 2.0*(mm_remaining-prep.mm_complete)/(prep.current_speed+prep.exit_speed);
mm_remaining = prep.mm_complete;
} }
dt += time_var; // Add computed ramp time to total segment time. dt += time_var; // Add computed ramp time to total segment time.
if (dt < DT_SEGMENT) { time_var = DT_SEGMENT - dt; } // **Incomplete** At ramp junction. if (dt < DT_SEGMENT) { time_var = DT_SEGMENT - dt; } // **Incomplete** At ramp junction.
else { break; } // **Complete** Exit loop. Segment execution time maxed. else { break; } // **Complete** Exit loop. Segment execution time maxed.
} while (mm_remaining > prep.mm_eob); // **Complete** Exit loop. End of planner block. } while (mm_remaining > prep.mm_complete); // **Complete** Exit loop. Profile complete.
/* ----------------------------------------------------------------------------------- /* -----------------------------------------------------------------------------------
Compute segment step rate, steps to execute, and step phase correction parameters. Compute segment step rate, steps to execute, and step phase correction parameters.
@ -622,7 +635,7 @@ void st_prep_buffer()
*/ */
// Use time_var to pre-compute dt inversion with integer multiplier. // Use time_var to pre-compute dt inversion with integer multiplier.
time_var = (INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))/dt; // (mult/isr_tic) time_var = (INV_TIME_MULTIPLIER/(60.0*ISR_TICKS_PER_SECOND))/dt; // (mult/isr_tic)
if (mm_remaining > 0.0) { if (mm_remaining > 0.0) { // Block still incomplete. Distance remaining to be executed.
float steps_remaining = prep.step_per_mm*mm_remaining; float steps_remaining = prep.step_per_mm*mm_remaining;
prep_segment->dist_per_tick = ceil( (prep.steps_remaining-steps_remaining)*time_var ); // (mult*step/isr_tic) prep_segment->dist_per_tick = ceil( (prep.steps_remaining-steps_remaining)*time_var ); // (mult*step/isr_tic)
@ -631,7 +644,7 @@ void st_prep_buffer()
prep_segment->n_step = ceil(prep.steps_remaining)-ceil(steps_remaining); prep_segment->n_step = ceil(prep.steps_remaining)-ceil(steps_remaining);
// Update step execution variables. // Update step execution variables.
if (mm_remaining == prep.mm_eob) { if (mm_remaining == prep.mm_complete) {
// NOTE: Currently only feed holds qualify for this scenario. May change with overrides. // NOTE: Currently only feed holds qualify for this scenario. May change with overrides.
prep.current_speed = 0.0; prep.current_speed = 0.0;
prep.steps_remaining = ceil(steps_remaining); prep.steps_remaining = ceil(steps_remaining);