This project was a research collaboration between Carleton University and Defence Research and Development Canada that focused on the derivation and laboratory validation of ship-based human postural stability models. The modelling objectives were focused on modelling human interaction with unsteady loads on board ships at sea. The models were experimentally validated at full scale using purpose-built physical apparatus installed on a six-degree-of-freedom motion platform.

An image of a portion of the experimental apparatus is shown on the right. The object in the middle is an inverted pendulum that has two degrees of freedom relative to the motion platform: it can pitch and roll at its base. A custom universal joint was specially designed by a student and its motion was controlled with two geared electric servo motors. Options were available for connecting the inverted pendulum to a pendulating load or a cart load that could rotated and/or translate.

My responsibilities in this project included the following tasks.

  • Interface between ship motion simulation and the motion platform using Windows messaging in C++.
  • Feedback control of the inverted pendulum in LabView based on current platform position. This task also involved UDP network communication between a C++ program and LabView.
  • Coordinated data acquisition from all of the sensors including:
    • forces and torques measured by a six-axis load cell located between the inverted pendulum and motion platform;
    • motion platform orientations;
    • motor output torques;
    • forces measured by a one-axis load cell placed in the rod that connected the inverted pendulum to another unsteady load; and
    • measurements made by a position encoder installed in the cart load.

Here are two videos which show that the inverted pendulum controller is operating as expected: the inverted pendulum remains vertical while the platform moves.