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rotary_delta: Initial support for rotary delta kinematics

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Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor
2019-10-19 21:04:42 -04:00
parent a56484c98b
commit ac863a95b6
7 changed files with 546 additions and 2 deletions
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klippy/chelper/kin_rotary_delta.c Normal file
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// Rotary delta kinematics stepper pulse time generation
//
// Copyright (C) 2019 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <math.h> // sqrt
#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" // move_get_coord
// The arm angle calculation is based on the following two formulas:
// elbow_x**2 + elbow_y**2 = upper_arm**2
// (effector_x - elbow_x)**2 + (effector_y - elbow_y)**2 = lower_arm**2
// Calculate upper arm angle given xy position of effector joint
// (relative to shoulder joint), upper arm length, and lower arm length.
static inline double
rotary_two_arm_calc(double dx, double dy, double upper_arm2, double lower_arm2)
{
// Determine constants such that: elbow_y = c1 - c2*elbow_x
double inv_dy = 1. / dy;
double c1 = .5 * inv_dy * (dx*dx + dy*dy + upper_arm2 - lower_arm2);
double c2 = dx * inv_dy;
// Calculate scaled elbow coordinates via quadratic equation.
double scale = c2*c2 + 1.0;
double scaled_elbow_x = c1*c2 + sqrt(scale*upper_arm2 - c1*c1);
double scaled_elbow_y = c1*scale - c2*scaled_elbow_x;
// Calculate angle in radians
return atan2(scaled_elbow_y, scaled_elbow_x);
}
struct rotary_stepper {
struct stepper_kinematics sk;
double cos, sin, shoulder_radius, shoulder_height;
double upper_arm2, lower_arm2;
};
static double
rotary_stepper_calc_position(struct stepper_kinematics *sk, struct move *m
, double move_time)
{
struct rotary_stepper *rs = container_of(sk, struct rotary_stepper, sk);
struct coord c = move_get_coord(m, move_time);
// Rotate and shift axes to an origin at shoulder joint with upper
// arm constrained to xy plane and x aligned to shoulder platform.
double sjz = c.y * rs->cos - c.x * rs->sin;
double sjx = c.x * rs->cos + c.y * rs->sin - rs->shoulder_radius;
double sjy = c.z - rs->shoulder_height;
// Calculate angle in radians
return rotary_two_arm_calc(sjx, sjy, rs->upper_arm2
, rs->lower_arm2 - sjz*sjz);
}
struct stepper_kinematics * __visible
rotary_delta_stepper_alloc(double shoulder_radius, double shoulder_height
, double angle, double upper_arm, double lower_arm)
{
struct rotary_stepper *rs = malloc(sizeof(*rs));
memset(rs, 0, sizeof(*rs));
rs->cos = cos(angle);
rs->sin = sin(angle);
rs->shoulder_radius = shoulder_radius;
rs->shoulder_height = shoulder_height;
rs->upper_arm2 = upper_arm * upper_arm;
rs->lower_arm2 = lower_arm * lower_arm;
rs->sk.calc_position_cb = rotary_stepper_calc_position;
rs->sk.active_flags = AF_X | AF_Y | AF_Z;
return &rs->sk;
}