Inverse Kinematics for 3-DOF and 6-DOF Motion Control

A platform pose is described by translation along X, Y and Z and rotation about those axes. For a Stewart platform, inverse kinematics calculates the six actuator lengths required to produce a requested pose.

Calculation Outline

1. Define the six upper and lower joint coordinates in their local frames.
2. Build the rotation matrix and translation vector for the requested pose.
3. Transform each upper joint into the base coordinate frame.
4. Calculate the distance from each transformed upper joint to its corresponding lower joint.
5. Check actuator stroke, velocity, acceleration, joint angle and workspace limits.

Inverse kinematics is used for real-time command generation. Forward kinematics estimates pose from measured actuator lengths and normally requires iterative numerical calculation. Both algorithms depend on accurate geometry, coordinate conventions and calibration.