SYNOPSIS

DESCRIPTION

SEE ALSO

kins − kinematics definitions for LinuxCNC

**loadrt
trivkins (use for most cartesian machines)**

**loadrt
corexykins**

**loadrt
genhexkins**

**loadrt
genserkins**

**loadrt
lineardeltakins (see separate manpage)**

**loadrt
maxkins**

**loadrt
pentakins**

**loadrt
pumakins**

**loadrt
rosekins**

**loadrt
rotarydeltakins**

**loadrt
rotatekins**

**loadrt
scarakins**

**loadrt
tripodkins**

**loadrt
xyzac−trt−kins**

**loadrt
xyzbc−trt−kins**

**loadrt
5axiskins**

Rather than exporting HAL pins and functions, these components provide the forward and inverse kinematics definitions for LinuxCNC.

**trivkins
− generalized trivial kinematics**

Joint numbers are assigned sequentialy according to the axis
letters specified with the **coordinates=**
parameter.

If the
coordinates= parameter is omitted, joint numbers are
assigned **sequentially** to every known axis letter
("xyzabcuvw").

Example: loadrt **trivkins**

Assigns all axis letters to joint numbers in sequence:

x==joint0,
y==joint1, z==joint2

a==joint3, b==joint4, c==joint5

u==joint6, v==joint7, w==joint8

Example: loadrt **trivkins coordinates=xyz**

Assigns: x==joint0, y==joint1, z==joint2

Example: loadrt **trivkins coordinates=xz**

Assigns: x==joint0, z==joint1

Example: loadrt **trivkins coordinates=xyzy**

Assigns: x==joint0, y0==joint1, z==joint2, y1==joint3

The default
kinematics type is **KINEMATICS_IDENTITY**. Guis may
provide special features for configurations using this
default kinematics type. For instance, the axis gui
automatically handles joint and world mode operations so
that the distinctions between joints and axes are not
visible to the operator. This is feasible since there is an
exact correspondence between a joint number and its matching
axis letter.

The kinematics type can be set with the **kinstype=**
parameter:

kinstype=**1** for KINEMATICS_IDENTITY (default if
kinstype= omitted)

kinstype=[**b**|**B**] for KINEMATICS_BOTH

kinstype=[**f**|**F**] for KINEMATICS_FORWARD_ONLY

kinstype=[**i**|**I**] for KINEMATICS_INVERSE_ONLY

Example: loadrt **trivkins coordinates=xyz
kinstype=b**

Use
kinstype=**B** (KINEMATICS_BOTH) for configurations that
need to move joints independently (joint mode) or as
coordinated (teleop) movements in world coordinates.

When using the
axis gui with KINEMATICS_BOTH, the ’**$**’
key is used to toggle between joint and teleop (world)
modes.

An axis letter
may be used more than once (**duplicated**) to assign
multiple joints to a single axis coordinate letter.

Example: coordinates=**xyyzw** kinstype=**B**

Assigns: x==joint0, y==joint1 **AND** joint2, z==joint3,
w==joint4

The above
example illustrates a gantry configuration that uses
**duplicated** coordinate letters to indicate that two
joints (joint1 and joint2) move a single axis (y). Using
kinstype=**B** allows the configuration to be toggled
between joint and world modes of operation. Homing
configuration options are available to synchronize the final
homing move for selected joints -- see the documentation for
**Homing Configuration**.

**NOTES**
for **duplicated** coordinates:

When
**duplicated** coordinate letters are used, specifying
KINEMATICS_BOTH (kinstype=**B**) allows a gui to support
jogging of each individual joint in **joint mode**.
**Caution** is required for machines where the movement
of a single joint (in a set specified by a **duplicated**
coordinate letter) can lead to gantry racking or other
unwanted outcomes. When the kinstype= parameter is omitted,
operation defaults to KINEMATICS_IDENTITY
(kinstype=**1**) and a gui may allow jogging based upon a
selected axis coordinate letter (or by a keyboard key)
before homing is completed and the machine is still in
**joint mode**. The joint selected will depend upon the
gui implementation but typically only one of the multiple
joints in the set will jog. Consequently, specifying
KINEMATICS_BOTH is recommended as it enables support for
unambiguous, independent jogging of each individual joint.
Machines that implement homing for all joints (including the
provisions for synchronizing the final homing move for
multiple joints) may be homed at machine startup and
automatically switch to **world** mode where
per-coordinate jogging is available.

**corexykins
− CoreXY Kinematics**

X = 0.5*(JOINT_0 + JOINT_1)

Y = 0.5*(JOINT_0 − JOINT_1)

Z = JOINT_2

[KINS]JOINTS= must specify 3 or more joints (maximum 9)

If enabled by the number of [KINS]JOINTS= specified,
JOINT_3,4,5,6,7,8

correspond to coordinates A,B,C,U,V,W respectively.

**genhexkins
− Hexapod Kinematics**

Gives six degrees of freedom in position and orientation
(XYZABC). The location of base and platform joints is
defined by hal parameters. The forward kinematics iteration
is controlled by hal pins.

genhexkins.base.*N***.x
genhexkins.base.**

genhexkins.base.

genhexkins.platform.

genhexkins.platform.

genhexkins.platform.

Parameters describing the
*N*th joint’s coordinates.

**genhexkins.spindle−offset**

Added to all joints Z coordinates to change the machine origin. Facilitates adjusting spindle position.

**genhexkins.base−n.***N***.x
genhexkins.base−n.**

genhexkins.base−n.

genhexkins.platform−n.

genhexkins.platform−n.

genhexkins.platform−n.

Parameters describing unit
vectors of *N*th joint’s axis. Used to calculate
strut length correction for cardanic joints and non-captive
actuators.

**genhexkins.screw−lead**

Lead of strut actuator screw, positive for the right-handed thread. Default is 0 (strut length correction disabled).

**genhexkins.correction.***N*

Current values of strut length
correction for non-captive actuators with cardanic joints.
**genhexkins.convergence−criterion** Minimum error
value that ends iterations with converged solution.

**genhexkins.limit−iterations**

Limit of iterations, if exceeded iterations stop with no convergence.

**genhexkins.max−error**

Maximum error value, if exceeded iterations stop with no convergence.

**genhexkins.last−iterations**

Number of iterations spent for the last forward kinematics solution.

**genhexkins.max−iterations**

Maximum number of iterations spent for a converged solution during current session.

**genhexkins.tool−offset**

TCP offset from platform origin along Z to implement RTCP function. To avoid joints jump change tool offset only when the platform is not tilted.

**genserkins
− generalized serial kinematics**

Kinematics that can model a general serial-link manipulator
with up to 6 angular joints.

The kinematics
use Denavit-Hartenberg definition for the joint and links.
The DH definitions are the ones used by John J Craig in
"Introduction to Robotics: Mechanics and Control"
The parameters for the manipulator are defined by hal pins.
Note that this uses a convention sometimes known as
"Modified DH Paremeters" and this must be borne in
mind when setting up the system.
https://en.wikipedia.org/wiki/Denavit%E2%80%93Hartenberg_parameters#Modified_DH_parameters

genserkins.A−*N*

genserkins.ALPHA−*N*

genserkins.D−*N*

Parameters describing the
*N*th joint’s geometry.

**maxkins
− 5-axis kinematics example**

Kinematics for Chris Radek’s tabletop 5 axis mill
named ’max’ with tilting head (B axis) and
horizintal rotary mounted to the table (C axis). Provides
UVW motion in the rotated coordinate system. The source
file, maxkins.c, may be a useful starting point for other
5-axis systems.

**pentakins
− Pentapod Kinematics**

Gives five degrees of freedom in position and orientation
(XYZAB). The location of base and effector joints is defined
by hal parameters. The forward kinematics iteration is
controlled by hal pins.

pentakins.base.*N***.x
pentakins.base.**

pentakins.base.

pentakins.effector.

pentakins.effector.

Parameters describing the
*N*th effector joint’s radius and axial
position.

**pentakins.convergence−criterion**

Minimum error value that ends iterations with converged solution.

**pentakins.limit−iterations**

Limit of iterations, if exceeded iterations stop with no convergence.

**pentakins.max−error**

Maximum error value, if exceeded iterations stop with no convergence.

**pentakins.last−iterations**

Number of iterations spent for the last forward kinematics solution.

**pentakins.max−iterations**

Maximum number of iterations spent for a converged solution during current session.

**pentakins.tool−offset**

TCP offset from effector origin along Z to implement RTCP function. To avoid joints jump change tool offset only when the platform is not tilted.

**pumakins
− kinematics for puma typed robots**

Kinematics for a puma-style robot with 6 joints

pumakins.A2

pumakins.A3

pumakins.D3

pumakins.D4

Describe the geometry of the robot

**rosekins
− kinematics for a rose engine using**

a transverse, longitudinal, and rotary joint (3 joints)

**rotarydeltakins
− kinematics for a rotary delta machine**

Rotary delta robot (3 Joints)

**rotatekins
− Rotated Kinematics**

The X and Y axes are rotated 45 degrees compared to the
joints 0 and 1.

**scarakins
− kinematics for SCARA-type robots
scarakins.D1**

Vertical distance from the ground plane to the center of the inner arm.

**scarakins.D2**

Horizontal distance between joint[0] axis and joint[1] axis, ie. the length of the inner arm.

**scarakins.D3**

Vertical distance from the center of the inner arm to the center of the outer arm. May be positive or negative depending on the structure of the robot.

**scarakins.D4**

Horizontal distance between joint[1] axis and joint[2] axis, ie. the length of the outer arm.

**scarakins.D5**

Vertical distance from the end effector to the tooltip. Positive means the tooltip is lower than the end effector, and is the normal case.

**scarakins.D6**

Horizontal distance from the centerline of the end effector (and the joints 2 and 3 axis) and the tooltip. Zero means the tooltip is on the centerline. Non-zero values should be positive, if negative they introduce a 180 degree offset on the value of joint[3].

**tripodkins
− Tripod Kinematics**

The joints represent the distance of the controlled point
from three predefined locations (the motors), giving three
degrees of freedom in position (XYZ)

tripodkins.Bx

tripodkins.Cx

tripodkins.Cy

The location of the three motors is (0,0), (Bx,0), and (Cx,Cy)

**xyzac−trt−kins
− 5 Axis mill (Table Rotary/Tilting)**

Tilting table (A) and horizontal rotary mounted tothe table
(C) (5 Joints)

**xyzbc−trt−kins
− 5 Axis mill (Table Rotary/Tilting)**

Tilting table (B) and horizontal rotary mounted to table (C
axis) (5 Joints)

**5axiskins
− 5 Axis bridge mill**

XYZBC (5 Joints)

*Kinematics*
section in the LinuxCNC documentation