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Inverse Kinematics of PX100 Arm: Python Code Example

For 2024Fall EE211 Course Project

Last Update: 2024-11-13


What is Inverse Kinematics?

Inverse Kinematics (IK) is a method to determine the joint angles of a robot arm given the desired end-effector position and orientation.

While Forward Kinematics (FK) is to determine the end-effector position and orientation given the joint angles.


For PX100 arm, the end-effector is the gripper.


Questions:

  1. How many solutions does a FK problem have?
  2. How many soluttons does a IK problem have for a PX100 arm?
  3. How many solutions does a IK problem have?
  4. How many solutions does a IK problem have for a PX100 arm?


Now, you can connect to your robot, then run ros2 launch interbotix_xsarm_descriptions xsarm_description.launch.py robot_model:=px100 use_joint_pub_gui:=true to visualize the arm in rviz2， which will show you the detailed robot model description.

px100


Python Code Example – Utilizing robotics toolbox package

Install robotics toolbox for python

pip install roboticstoolbox-python
pip install spatialmath-python

roboticstoolbox-python has the px100 model built-in, so we can directly use it.

Code Example

import roboticstoolbox as rtb
from spatialmath import SE3
import numpy as np

robot = rtb.models.px100()

tx = 0.2486
ty = 0.0
tz = 0.193
tpos = SE3(tx, ty, tz)

# robot[11] is the index of ee_gripper_link in the urdf
ik_sol = robot.ikine_LM(tpos, end=robot[11])

if ik_sol.success:
    print("Valid Solution: {}".format(ik_sol.q))
    # Uncomment the following lines to validate the solution
    # print("FK Validation:")
    # fk_val = robot.fkine(np.array( [0, 0, 0, 0] ), end=robot[11], start=robot[0])
    # print(fk_val.t)
else:
    print("Invalid Input!!!")

Now you can play the code yourself, and integrate it with the arm hardware python script.



Reference