ik-geo

IK-Geo

This implementation of the core IK-Geo algorithms was adapted from IK-Geo. For details on the algorithms used, refer to the original source or to the paper "IK-Geo: Unified Robot Inverse Kinematics Using Subproblem Decomposition".

To install

This can be installed from pypi with:

pip install ik_geo

To install the package from this repository locally, use:

pip install .

To Use

Refer to examples/sample.py for a full code example. To compute the IK solutions for a specific robot, you can either select one of the hardcoded robots available or provide your own kinematics. If you provide your own kinematics, you must do so as a Product of Exponentials (POE). This is either with 6 or 7 h vectors (rotation axes) and 7 or 8 p vectors (displacements), respectively. Note that 7-joint bots are not yet supported, so the user must choose one joint to fix to give 6 h vectors and 7 p vectors

Once you have your kinematics, you need to choose the correct decomposition strategy from: { "spherical_two_parallel", "spherical_two_intersecting", "spherical", "three_parallel_two_intersecting", "three_parallel", "two_parallel", "two_intersecting", "gen_six_dof" } to use. If you choose the wrong one, you will get wrong answers.

Once you have configured your IK solver, you can get a list of IK solutions by calling the desired ik function:

from ik_geo import Robot

h # 6x3 array
p # 7x3 array

robot = Robot.spherical_two_intersecting(h,p)

R = [[0, 0, 1], [0, 1, 0], [-1, 0, 0]]
t = [-1, 3, 0]

# For all possible solutions, as well as whether or not they are least squares
solutions = robot.get_ik(R, t)

# For all possible IK solutions sorted by error
solutions = robot.get_ik_sorted(R, t)

Performance

While this implementation can be used on a wide range of manipulators, it performs much better on when the solution can be found entirely analytically. The following table shows which method is used for each type of kinematics:

Solution Type	Robot Kinematic Family	Example
Closed-form	Spherical joint	Franka Production 3, fixed $q_5$
	and two intersecting axes	KUKA LBR iiwa 7 R800 , fixed $q_3$
	and two parallel axes	ABB IRB 6640
	Three parallel axes	N/A
	and two intersecting axes	Universal Robots UR5
	and two parallel axes	N/A
1D search	Two intersecting axes	Kassow Robots KR810, fixed $q_7$
	and two intersecting axes	FANUC CRX-10iA/L
	and two parallel axes	Kawasaki KJ125
	Two parallel axes	N/A
	and two parallel axes	N/A
	Two intersecting axes $k, k+2$	ABB YuMi, fixed $q_3$
	and two intersecting axes	RRC K-1207i, fixed $q_6$
	and two parallel axes	N/A
2D search	General 6R	Kassow Robots KR810, fixed $q_6$