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First arcs version. (Arcs not working ok)

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This commit is contained in:
Erik van der Zalm 2011-11-06 12:39:00 +01:00
parent 2e8e8878e5
commit 0b82465168
4 changed files with 1784 additions and 1479 deletions
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3
Marlin/Configuration.h
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@ -3,6 +3,9 @@
//#define DEBUG_STEPS
#define MM_PER_ARC_SEGMENT 1
#define N_ARC_CORRECTION 25
// BASIC SETTINGS: select your board type, thermistor type, axis scaling, and endstop configuration
//// The following define selects which electronics board you have. Please choose the one that matches your setup

137
Marlin/Marlin.pde
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@ -35,6 +35,7 @@
#include "planner.h"
#include "stepper.h"
#include "temperature.h"
#include "motion_control.h"
#ifdef SIMPLE_LCD
#include "Simplelcd.h"
@ -113,6 +114,7 @@ float destination[NUM_AXIS] = {
0.0, 0.0, 0.0, 0.0};
float current_position[NUM_AXIS] = {
0.0, 0.0, 0.0, 0.0};
float offset[3] = {0.0, 0.0, 0.0};
bool home_all_axis = true;
float feedrate = 1500.0, next_feedrate, saved_feedrate;
long gcode_N, gcode_LastN;
@ -441,6 +443,8 @@ inline void get_command()
switch((int)((strtod(&cmdbuffer[bufindw][strchr_pointer - cmdbuffer[bufindw] + 1], NULL)))){
case 0:
case 1:
case 2:
case 3:
#ifdef SDSUPPORT
if(savetosd)
break;
@ -543,6 +547,16 @@ inline void process_commands()
//ClearToSend();
return;
//break;
case 2: // G2 - CW ARC
get_arc_coordinates();
prepare_arc_move(true);
previous_millis_cmd = millis();
return;
case 3: // G3 - CCW ARC
get_arc_coordinates();
prepare_arc_move(false);
previous_millis_cmd = millis();
return;
case 4: // G4 dwell
codenum = 0;
if(code_seen('P')) codenum = code_value(); // milliseconds to wait
@ -1139,6 +1153,13 @@ inline void get_coordinates()
}
}
inline void get_arc_coordinates()
{
get_coordinates();
if(code_seen("I")) offset[0] = code_value();
if(code_seen("J")) offset[1] = code_value();
}
void prepare_move()
{
plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], feedrate*feedmultiply/60.0/100.0);
@ -1147,7 +1168,122 @@ void prepare_move()
}
}
void prepare_arc_move(char isclockwise) {
#if 0
if (radius_mode) {
/*
We need to calculate the center of the circle that has the designated radius and passes
through both the current position and the target position. This method calculates the following
set of equations where [x,y] is the vector from current to target position, d == magnitude of
that vector, h == hypotenuse of the triangle formed by the radius of the circle, the distance to
the center of the travel vector. A vector perpendicular to the travel vector [-y,x] is scaled to the
length of h [-y/d*h, x/d*h] and added to the center of the travel vector [x/2,y/2] to form the new point
[i,j] at [x/2-y/d*h, y/2+x/d*h] which will be the center of our arc.
d^2 == x^2 + y^2
h^2 == r^2 - (d/2)^2
i == x/2 - y/d*h
j == y/2 + x/d*h
O <- [i,j]
- |
r - |
- |
- | h
- |
[0,0] -> C -----------------+--------------- T <- [x,y]
| <------ d/2 ---->|
C - Current position
T - Target position
O - center of circle that pass through both C and T
d - distance from C to T
r - designated radius
h - distance from center of CT to O
Expanding the equations:
d -> sqrt(x^2 + y^2)
h -> sqrt(4 * r^2 - x^2 - y^2)/2
i -> (x - (y * sqrt(4 * r^2 - x^2 - y^2)) / sqrt(x^2 + y^2)) / 2
j -> (y + (x * sqrt(4 * r^2 - x^2 - y^2)) / sqrt(x^2 + y^2)) / 2
Which can be written:
i -> (x - (y * sqrt(4 * r^2 - x^2 - y^2))/sqrt(x^2 + y^2))/2
j -> (y + (x * sqrt(4 * r^2 - x^2 - y^2))/sqrt(x^2 + y^2))/2
Which we for size and speed reasons optimize to:
h_x2_div_d = sqrt(4 * r^2 - x^2 - y^2)/sqrt(x^2 + y^2)
i = (x - (y * h_x2_div_d))/2
j = (y + (x * h_x2_div_d))/2
*/
// Calculate the change in position along each selected axis
double x = target[gc.plane_axis_0]-gc.position[gc.plane_axis_0];
double y = target[gc.plane_axis_1]-gc.position[gc.plane_axis_1];
clear_vector(offset);
double h_x2_div_d = -sqrt(4 * r*r - x*x - y*y)/hypot(x,y); // == -(h * 2 / d)
// If r is smaller than d, the arc is now traversing the complex plane beyond the reach of any
// real CNC, and thus - for practical reasons - we will terminate promptly:
if(isnan(h_x2_div_d)) { FAIL(STATUS_FLOATING_POINT_ERROR); return(gc.status_code); }
// Invert the sign of h_x2_div_d if the circle is counter clockwise (see sketch below)
if (gc.motion_mode == MOTION_MODE_CCW_ARC) { h_x2_div_d = -h_x2_div_d; }
/* The counter clockwise circle lies to the left of the target direction. When offset is positive,
the left hand circle will be generated - when it is negative the right hand circle is generated.
T <-- Target position
^
Clockwise circles with this center | Clockwise circles with this center will have
will have > 180 deg of angular travel | < 180 deg of angular travel, which is a good thing!
\ | /
center of arc when h_x2_div_d is positive -> x <----- | -----> x <- center of arc when h_x2_div_d is negative
|
|
C <-- Current position */
// Negative R is g-code-alese for "I want a circle with more than 180 degrees of travel" (go figure!),
// even though it is advised against ever generating such circles in a single line of g-code. By
// inverting the sign of h_x2_div_d the center of the circles is placed on the opposite side of the line of
// travel and thus we get the unadvisably long arcs as prescribed.
if (r < 0) {
h_x2_div_d = -h_x2_div_d;
r = -r; // Finished with r. Set to positive for mc_arc
}
// Complete the operation by calculating the actual center of the arc
offset[gc.plane_axis_0] = 0.5*(x-(y*h_x2_div_d));
offset[gc.plane_axis_1] = 0.5*(y+(x*h_x2_div_d));
} else { // Offset mode specific computations
#endif
float r = hypot(offset[X_AXIS], offset[Y_AXIS]); // Compute arc radius for mc_arc
// }
// Set clockwise/counter-clockwise sign for mc_arc computations
// uint8_t isclockwise = false;
// if (gc.motion_mode == MOTION_MODE_CW_ARC) { isclockwise = true; }
// Trace the arc
mc_arc(current_position, destination, offset, X_AXIS, Y_AXIS, Z_AXIS, feedrate*feedmultiply/60.0/100.0, r, isclockwise);
// }
// As far as the parser is concerned, the position is now == target. In reality the
// motion control system might still be processing the action and the real tool position
// in any intermediate location.
for(int ii=0; ii < NUM_AXIS; ii++) {
current_position[ii] = destination[ii];
}
}
#ifdef USE_WATCHDOG
@ -1233,3 +1369,4 @@ void manage_inactivity(byte debug) {
}
check_axes_activity();
}

133
Marlin/motion_control.cpp Normal file
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@ -0,0 +1,133 @@
/*
motion_control.c - high level interface for issuing motion commands
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Copyright (c) 2011 Sungeun K. 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/>.
*/
//#include "motion_control.h"
#include "Configuration.h"
#include "Marlin.h"
//#include <util/delay.h>
//#include <math.h>
//#include <stdlib.h>
#include "stepper.h"
#include "planner.h"
// The arc is approximated by generating a huge number of tiny, linear segments. The length of each
// segment is configured in settings.mm_per_arc_segment.
void mc_arc(float *position, float *target, float *offset, uint8_t axis_0, uint8_t axis_1,
uint8_t axis_linear, float feed_rate, float radius, uint8_t isclockwise)
{
// int acceleration_manager_was_enabled = plan_is_acceleration_manager_enabled();
// plan_set_acceleration_manager_enabled(false); // disable acceleration management for the duration of the arc
Serial.println("mc_arc");
float center_axis0 = position[axis_0] + offset[axis_0];
float center_axis1 = position[axis_1] + offset[axis_1];
float linear_travel = target[axis_linear] - position[axis_linear];
float r_axis0 = -offset[axis_0]; // Radius vector from center to current location
float r_axis1 = -offset[axis_1];
float rt_axis0 = target[axis_0] - center_axis0;
float rt_axis1 = target[axis_1] - center_axis1;
// CCW angle between position and target from circle center. Only one atan2() trig computation required.
float angular_travel = atan2(r_axis0*rt_axis1-r_axis1*rt_axis0, r_axis0*rt_axis0+r_axis1*rt_axis1);
if (angular_travel < 0) { angular_travel += 2*M_PI; }
if (isclockwise) { angular_travel -= 2*M_PI; }
float millimeters_of_travel = hypot(angular_travel*radius, fabs(linear_travel));
if (millimeters_of_travel == 0.0) { return; }
uint16_t segments = floor(millimeters_of_travel/MM_PER_ARC_SEGMENT);
/*
// Multiply inverse feed_rate to compensate for the fact that this movement is approximated
// by a number of discrete segments. The inverse feed_rate should be correct for the sum of
// all segments.
if (invert_feed_rate) { feed_rate *= segments; }
*/
float theta_per_segment = angular_travel/segments;
float linear_per_segment = linear_travel/segments;
/* Vector rotation by transformation matrix: r is the original vector, r_T is the rotated vector,
and phi is the angle of rotation. Based on the solution approach by Jens Geisler.
r_T = [cos(phi) -sin(phi);
sin(phi) cos(phi] * r ;
For arc generation, the center of the circle is the axis of rotation and the radius vector is
defined from the circle center to the initial position. Each line segment is formed by successive
vector rotations. This requires only two cos() and sin() computations to form the rotation
matrix for the duration of the entire arc. Error may accumulate from numerical round-off, since
all double numbers are single precision on the Arduino. (True double precision will not have
round off issues for CNC applications.) Single precision error can accumulate to be greater than
tool precision in some cases. Therefore, arc path correction is implemented.
Small angle approximation may be used to reduce computation overhead further. This approximation
holds for everything, but very small circles and large mm_per_arc_segment values. In other words,
theta_per_segment would need to be greater than 0.1 rad and N_ARC_CORRECTION would need to be large
to cause an appreciable drift error. N_ARC_CORRECTION~=25 is more than small enough to correct for
numerical drift error. N_ARC_CORRECTION may be on the order a hundred(s) before error becomes an
issue for CNC machines with the single precision Arduino calculations.
This approximation also allows mc_arc to immediately insert a line segment into the planner
without the initial overhead of computing cos() or sin(). By the time the arc needs to be applied
a correction, the planner should have caught up to the lag caused by the initial mc_arc overhead.
This is important when there are successive arc motions.
*/
// Vector rotation matrix values
float cos_T = 1-0.5*theta_per_segment*theta_per_segment; // Small angle approximation
float sin_T = theta_per_segment;
float arc_target[3];
float sin_Ti;
float cos_Ti;
float r_axisi;
uint16_t i;
int8_t count = 0;
// Initialize the linear axis
arc_target[axis_linear] = position[axis_linear];
for (i = 1; i<segments; i++) { // Increment (segments-1)
if (count < N_ARC_CORRECTION) {
// Apply vector rotation matrix
r_axisi = r_axis0*sin_T + r_axis1*cos_T;
r_axis0 = r_axis0*cos_T - r_axis1*sin_T;
r_axis1 = r_axisi;
count++;
} else {
// Arc correction to radius vector. Computed only every N_ARC_CORRECTION increments.
// Compute exact location by applying transformation matrix from initial radius vector(=-offset).
cos_Ti = cos(i*theta_per_segment);
sin_Ti = sin(i*theta_per_segment);
r_axis0 = -offset[axis_0]*cos_Ti + offset[axis_1]*sin_Ti;
r_axis1 = -offset[axis_0]*sin_Ti - offset[axis_1]*cos_Ti;
count = 0;
}
// Update arc_target location
arc_target[axis_0] = center_axis0 + r_axis0;
arc_target[axis_1] = center_axis1 + r_axis1;
arc_target[axis_linear] += linear_per_segment;
plan_buffer_line(arc_target[X_AXIS], arc_target[Y_AXIS], arc_target[Z_AXIS], target[E_AXIS], feed_rate);
}
// Ensure last segment arrives at target location.
plan_buffer_line(target[X_AXIS], target[Y_AXIS], target[Z_AXIS], target[E_AXIS], feed_rate);
// plan_set_acceleration_manager_enabled(acceleration_manager_was_enabled);
}

32
Marlin/motion_control.h Normal file
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@ -0,0 +1,32 @@
/*
motion_control.h - high level interface for issuing motion commands
Part of Grbl
Copyright (c) 2009-2011 Simen Svale Skogsrud
Copyright (c) 2011 Sungeun K. 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/>.
*/
#ifndef motion_control_h
#define motion_control_h
// Execute an arc in offset mode format. position == current xyz, target == target xyz,
// offset == offset from current xyz, axis_XXX defines circle plane in tool space, axis_linear is
// the direction of helical travel, radius == circle radius, isclockwise boolean. Used
// for vector transformation direction.
void mc_arc(float *position, float *target, float *offset, unsigned char axis_0, unsigned char axis_1,
unsigned char axis_linear, float feed_rate, float radius, unsigned char isclockwise);
#endif