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Question Stewart platform forward kinematics

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Aerosmith, Mar 15, 2025 at 11:29.

  1. Aerosmith

    Aerosmith Active Member

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    My Motion Simulator:
    3DOF, AC motor
    Unlike for robot arms where the forward kinematics (calculating t he position of the gripper from the joint angles) is easy to solve and the reverse is difficult (calculating the angles from a desired position) for Stewart platform it's the opposite. Calculating the inverse kinematics (what FlyPT Mover does) is easy. Just rotate and translate the rig to the desired position and calculate the length of the actuators (= distance of the end points in 3D space). That's straight forward and has only one solution that can be calculated by an explicit formula.

    But how can the forward kinematics be solved? There are always at least two different solutions, one with the rig above and one below the base plane. If there are singularities there may be even more solutions. And AFAIKS, a system of non-linear equations has to be solved to find them.

    Does anybody know a solution for this, hopefully a code snippet or Excel sheet? I need this to implement a collision avoidance system.
    Aerosmith, Mar 15, 2025 at 11:29
    #1