Six Axis Platform Using Linear Actuators (Stewart Platform)

This year for the annual Progressive Automations' University Sponsorship, we worked alongside the University of British Columbia's Engineering Physics department. A team of 4th year engineering students designed and built a 6-Degrees of Freedom Stewart Platform.

Along with the custom graphical user interface (GUI), a Leap Motion Controller was integrated to allow users full motion control of the entire platform with the wave of their hand. This combination allows for an interesting and interactive experience where one can learn about linear motion control as well as the physics behind it.

1.1 Project Objectives

The objective of this project is to demonstrate the capabilities of linear actuators manufactured by Progressive Automations. This, once the platform is functional, requires the design and development of one or more demos. These demos must provide a creative and interesting motive in controlling the platform and be included as a part of the end product. The final implementation of the platform must be appropriate for presentation, and therefore needs to operate at a smooth, reasonable speed while being able to approximate the theoretical range of motion (enough to properly run the demos). For the maximal user experience, the platform should be responsive to external control via joystick or Leap Motion, which needs to be accurate to the motion of the platform and perform with near-zero latency. The control method should require minimal setup and explanation for the end user. Finally, any external platform components including electronics, controllers, and the power supply must fit in a portable enclosure in order for the platform to be mobile enough for transportation to/from trade shows. The enclosure should have easy access to the Arduino board for testing and modification, have plug-and-play connection capabilities to peripherals such as the actuator cables, and ideally fit within the platform base when active.

1.2 Scope and Limitations

This report outlines the work completed during the period of October 2017 to April 2018 in implementing the following major tasks:

• improving serial communication and responsiveness, through reworking existing Arduino code and researching micro-controller alternatives;
• reworking and testing Leap Motion code with the platform;
• creating a user interface for interaction with the platform and Leap Motion controller;
• designing and fabricating new circuit boards and wiring for the electronics;
• designing and fabricating an enclosure for all electronic components; and
• designing and fabricating a tilt maze demo.

The project uses the PA-14P Feedback Linear Actuators and MultiMoto Arduino Shield. Though there was the option of looking at different product options provided by Progressive Automations, there was little motivation as the current actuator model provided the best speed at its size. Alternatives to the included potentiometer such as an accelerometer or a Hall effect sensor were not tested; it is unknown if implementing those would have reduced noise in the feedback system, at the cost of a more complex control method.

Joysticks and game controllers were briefly investigated as additional user input devices; however,
due to time constraints and disparate control implementations they were ultimately not considered. The Leap Motion controller was also tested at an early stage of the project and found to be usable, which also relieved concerns that a back-up form of control would be necessary. Since the user interface was designed in Qt, the software will be released under the LGPL (GNU Lesser General Public License) and must be kept as an open-source project while without a commercial Qt license. This should not be a concern given that the project is not meant for sale or as private IP.

This project was documented and photographed to release to our customers and Maker community to build their own version of the Stewart Platform!

Visit the Progressive Automations' GitHub for SolidWorks model, AutoCAD drawings, schematics, programming code, Leap information, and more!