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MP SCARA kinematic #645

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Feb 25, 2024
Merged

MP SCARA kinematic #645

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bf2e38b
MP SCARA kinematic
ademenev Feb 25, 2024
f9873b1
remove debug statement
ademenev Feb 25, 2024
ca912b2
clarify settings
ademenev Feb 25, 2024
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30 changes: 30 additions & 0 deletions uCNC/src/hal/kinematics/README.md
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Expand Up @@ -52,6 +52,36 @@ In addition to the standard configurations you need to set 5 extra settings:

For more information please head to the [µCNC wiki page](https://github.com/Paciente8159/uCNC/wiki)

### SCARA

SCARA kinematic is supported. µCNC supports 2 implementations of SCARA kinematic:
* standard serial SCARA. The shoulder motor is fixed to the base and rotates
the arm. The elbow motor is fixed to the arm and rotates the forearm. When the
shoulder motor rotates and the elbow motor is stopped, the angle between the
arm and the forearm is fixed, and the angle of the arm changes in relation
to the base.
* serial SCARA implementation with fixed motors, known as MP SCARA (mostly
printed SCARA). Both shoulder and elbow motors are fixed to the base. A
system of pulleys and closed belts is used to transfer motion from the elbow
motor to elbow joint. When the shoulder motor rotates and the elbow motor is
stopped, the angle of the arm changes in relation to the base, and the angle
between the forearm and the base is fixed.

To use MP SCARA kinematic, define MP_SCARA.

In addition to the standard configurations you need to set the following extra settings:

| Setting | Description |
| --- | --- |
| $28 | SCARA arm homing angle, degrees
| $29 | SCARA forearm homing angle, degrees
| $106 | SCARA arm length, mm
| $107 | SCARA forearm length, mm

Settings $100 and $101 have a different meaning, they
use revolution instead of mm.


## The kinematics HAL
This HAL is manages the way the linear actuators and the 3D Cartesian space axis relate to each other.
* Converts linear actuators (steppers) in to X,Y,Z,A,B,C coordinates and back.
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10 changes: 8 additions & 2 deletions uCNC/src/hal/kinematics/kinematic_scara.c
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Expand Up @@ -51,10 +51,14 @@ void kinematics_apply_inverse(float *axis, int32_t *steps)

float distance = (axis[AXIS_X] * axis[AXIS_X] + axis[AXIS_Y] * axis[AXIS_Y] - arm * arm - forearm * forearm) / (2.0f * arm * forearm);
float angle2 = acosf(distance);

steps[1] = (int32_t)roundf(angle2 * DOUBLE_PI_INV * g_settings.step_per_mm[1]);
float angle1 = atan2f(axis[AXIS_Y], axis[AXIS_X]) - atan2f(forearm * sin(angle2), (arm + forearm * distance));

#ifdef MP_SCARA
angle2 += angle1;
#endif

steps[0] = (int32_t)roundf(angle1 * DOUBLE_PI_INV * g_settings.step_per_mm[0]);
steps[1] = (int32_t)roundf(angle2 * DOUBLE_PI_INV * g_settings.step_per_mm[1]);

#if AXIS_COUNT > 2
for (uint8_t i = 2; i < AXIS_COUNT; i++)
Expand All @@ -72,7 +76,9 @@ void kinematics_apply_forward(int32_t *steps, float *axis)
float joint1 = steps[0] * scara_arm_angle_fact[0];
float joint2 = steps[1] * scara_arm_angle_fact[1];

#ifndef MP_SCARA
joint2 += joint1;
#endif

float arm = g_settings.scara_arm_length;
float forearm = g_settings.scara_forearm_length;
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