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// Kinematic input shapers to minimize motion vibrations in XY plane
//
// Copyright (C) 2019-2020 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2020 Dmitry Butyugin <dmbutyugin@google.com>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <math.h> // sqrt, exp
#include <stddef.h> // offsetof
#include <stdlib.h> // malloc
#include <string.h> // memset
#include "compiler.h" // __visible
#include "itersolve.h" // struct stepper_kinematics
#include "trapq.h" // struct move
/****************************************************************
* Shaper initialization
****************************************************************/
struct shaper_pulses {
int num_pulses;
struct {
double t, a;
} pulses[5];
};
// Shift pulses around 'mid-point' t=0 so that the input shaper is an identity
// transformation for constant-speed motion (i.e. input_shaper(v * T) = v * T)
static void
shift_pulses(struct shaper_pulses *sp)
{
int i;
double ts = 0.;
for (i = 0; i < sp->num_pulses; ++i)
ts += sp->pulses[i].a * sp->pulses[i].t;
for (i = 0; i < sp->num_pulses; ++i)
sp->pulses[i].t -= ts;
}
static int
init_shaper(int n, double a[], double t[], struct shaper_pulses *sp)
{
if (n < 0 || n > ARRAY_SIZE(sp->pulses)) {
sp->num_pulses = 0;
return -1;
}
int i;
double sum_a = 0.;
for (i = 0; i < n; ++i)
sum_a += a[i];
double inv_a = 1. / sum_a;
// Reverse pulses vs their traditional definition
for (i = 0; i < n; ++i) {
sp->pulses[n-i-1].a = a[i] * inv_a;
sp->pulses[n-i-1].t = -t[i];
}
sp->num_pulses = n;
shift_pulses(sp);
return 0;
}
/****************************************************************
* Generic position calculation via shaper convolution
****************************************************************/
static inline double
get_axis_position(struct move *m, int axis, double move_time)
{
double axis_r = m->axes_r.axis[axis - 'x'];
double start_pos = m->start_pos.axis[axis - 'x'];
double move_dist = move_get_distance(m, move_time);
return start_pos + axis_r * move_dist;
}
static inline double
get_axis_position_across_moves(struct move *m, int axis, double time)
{
while (likely(time < 0.)) {
m = list_prev_entry(m, node);
time += m->move_t;
}
while (likely(time > m->move_t)) {
time -= m->move_t;
m = list_next_entry(m, node);
}
return get_axis_position(m, axis, time);
}
// Calculate the position from the convolution of the shaper with input signal
static inline double
calc_position(struct move *m, int axis, double move_time
, struct shaper_pulses *sp)
{
double res = 0.;
int num_pulses = sp->num_pulses, i;
for (i = 0; i < num_pulses; ++i) {
double t = sp->pulses[i].t, a = sp->pulses[i].a;
res += a * get_axis_position_across_moves(m, axis, move_time + t);
}
return res;
}
/****************************************************************
* Kinematics-related shaper code
****************************************************************/
#define DUMMY_T 500.0
struct input_shaper {
struct stepper_kinematics sk;
struct stepper_kinematics *orig_sk;
struct move m;
struct shaper_pulses sx, sy;
};
// Optimized calc_position when only x axis is needed
static double
shaper_x_calc_position(struct stepper_kinematics *sk, struct move *m
, double move_time)
{
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
if (!is->sx.num_pulses)
return is->orig_sk->calc_position_cb(is->orig_sk, m, move_time);
is->m.start_pos.x = calc_position(m, 'x', move_time, &is->sx);
return is->orig_sk->calc_position_cb(is->orig_sk, &is->m, DUMMY_T);
}
// Optimized calc_position when only y axis is needed
static double
shaper_y_calc_position(struct stepper_kinematics *sk, struct move *m
, double move_time)
{
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
if (!is->sy.num_pulses)
return is->orig_sk->calc_position_cb(is->orig_sk, m, move_time);
is->m.start_pos.y = calc_position(m, 'y', move_time, &is->sy);
return is->orig_sk->calc_position_cb(is->orig_sk, &is->m, DUMMY_T);
}
// General calc_position for both x and y axes
static double
shaper_xy_calc_position(struct stepper_kinematics *sk, struct move *m
, double move_time)
{
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
if (!is->sx.num_pulses && !is->sy.num_pulses)
return is->orig_sk->calc_position_cb(is->orig_sk, m, move_time);
is->m.start_pos = move_get_coord(m, move_time);
if (is->sx.num_pulses)
is->m.start_pos.x = calc_position(m, 'x', move_time, &is->sx);
if (is->sy.num_pulses)
is->m.start_pos.y = calc_position(m, 'y', move_time, &is->sy);
return is->orig_sk->calc_position_cb(is->orig_sk, &is->m, DUMMY_T);
}
int __visible
input_shaper_set_sk(struct stepper_kinematics *sk
, struct stepper_kinematics *orig_sk)
{
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
if (orig_sk->active_flags == AF_X)
is->sk.calc_position_cb = shaper_x_calc_position;
else if (orig_sk->active_flags == AF_Y)
is->sk.calc_position_cb = shaper_y_calc_position;
else if (orig_sk->active_flags & (AF_X | AF_Y))
is->sk.calc_position_cb = shaper_xy_calc_position;
else
return -1;
is->sk.active_flags = orig_sk->active_flags;
is->orig_sk = orig_sk;
is->sk.commanded_pos = orig_sk->commanded_pos;
is->sk.last_flush_time = orig_sk->last_flush_time;
is->sk.last_move_time = orig_sk->last_move_time;
return 0;
}
static void
shaper_note_generation_time(struct input_shaper *is)
{
double pre_active = 0., post_active = 0.;
if ((is->sk.active_flags & AF_X) && is->sx.num_pulses) {
pre_active = is->sx.pulses[is->sx.num_pulses-1].t;
post_active = -is->sx.pulses[0].t;
}
if ((is->sk.active_flags & AF_Y) && is->sy.num_pulses) {
pre_active = is->sy.pulses[is->sy.num_pulses-1].t > pre_active
? is->sy.pulses[is->sy.num_pulses-1].t : pre_active;
post_active = -is->sy.pulses[0].t > post_active
? -is->sy.pulses[0].t : post_active;
}
is->sk.gen_steps_pre_active = pre_active;
is->sk.gen_steps_post_active = post_active;
}
int __visible
input_shaper_set_shaper_params(struct stepper_kinematics *sk, char axis
, int n, double a[], double t[])
{
if (axis != 'x' && axis != 'y')
return -1;
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
struct shaper_pulses *sp = axis == 'x' ? &is->sx : &is->sy;
int status = 0;
// Ignore input shaper update if the axis is not active
if (is->orig_sk->active_flags & (axis == 'x' ? AF_X : AF_Y)) {
status = init_shaper(n, a, t, sp);
shaper_note_generation_time(is);
}
return status;
}
double __visible
input_shaper_get_step_generation_window(struct stepper_kinematics *sk)
{
struct input_shaper *is = container_of(sk, struct input_shaper, sk);
return is->sk.gen_steps_pre_active > is->sk.gen_steps_post_active
? is->sk.gen_steps_pre_active : is->sk.gen_steps_post_active;
}
struct stepper_kinematics * __visible
input_shaper_alloc(void)
{
struct input_shaper *is = malloc(sizeof(*is));
memset(is, 0, sizeof(*is));
is->m.move_t = 2. * DUMMY_T;
return &is->sk;
}
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