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Mechatronics Learning Studio


Self-Balancing Platform

Alex Pittman, Vincent Kertesz, and Lucas West, Dept of Mech Engineering, University of Ottawa




Goal: Construct a platform capable of remaining level in the two axes parallel to the ground using digital sensors, various electronic components and actuators.

 Major Components:

·         Two linear actuators

·         Four tilt switches

·         Double H-bridge integrated circuit

·         Breadboard & DC power supply


Design Process:

            When we began the design process we planned to have a simply constructed platform and base connected by a ball and socket joint to allow the necessary freedom of movement for the platform. This was changed to a universal join because it allows the platform to tilt with much less resistance. This universal join was fitted to the upper platform and then screwed onto the aluminum support protruding from the base. This allowed us to move the join up and down along the support in order to fine tune its position relative to the linear actuators. The actuators were placed 25mm away from the central support, which allowed their 20mm stroke length to be translated into ±45° tilt. This device was constructed from inexpensive materials found at any hardware store, with a few parts purchased at a hobby store (such as the universal join). A power switch was installed to ensure the device can be shut down without the need to disconnect the power source.

            Initially we planned to use an accelerometer to measure the platforms inclination; this would involve using an Arduino board to take those sensor signals and a program to control the motors based on this data. We ended up choosing a much more direct, while slightly less accurate method of orientation sensing based on tilt switches. These switches contain a ball that can move to either end of a metal channel. When the ball rolls to one end it will complete the electrical connection, if it rolls to the other, this connection will be broken. To fully define an axis, two tilt switches are required, one for each of the possible orientation of tilt.

            The H-bridge circuit used in this project was originally meant to be built from basic electronics components, but using individual transistors and an optical isolator chip proved ineffective. The transistors would overhead and the optical isolator was unfortunately burnt out by excessive current. We ended up using an H-bridge integrated circuit which significantly simplified our overall electrical design. The platform was connected to the breadboard using 10 individual wires, two for each motor, and two for each sensor. The motors were run on a single 11V DC power supply while the H-bridge and sensors ran at 5V DC. The DC power supply could easily be replaced with batteries, but this an unnecessary expense in our case.

            When ordering parts online we chose mercury based tilt switches, but ended up being ball tilt switches when we received the order. The signals generated by the two opposing sensors are processed by an H-Bridge circuit which regulates the movement of the linear actuator. When the tilt switch adjacent to the actuator is activated, a positive voltage is run through the actuator, causing it to extend. When the opposite sensor is triggered the voltage across the actuator is reversed, causing it to retract. This system allows the platform to react to tilt, and keep the platform level in each axis.         

                        The linear actuators were the most expensive part used in the platform, but they were very necessary to its overall functionality. Due to another error in our order we received actuators that ran at two different voltages, one at 6V and one at 12V. This is apparent in their movements. The 12V motor moved much more slowly than its 6V counterpart at the voltage we used. But this minor complication didn’t have any major repercussions on the overall functioning of the platform.


Possible Improvements:

            The tilt sensors that were purchased are not especially sensitive and cause the platform to react sluggishly, if at all. These could be replaced by either a different ball tilt switch or a more expensive mercury tilt switch.

            The actuators used were an expensive option that simplified the design of the platform. These could be replaced by a system using two servo motors and a micro-controller. This change would lower the overall cost while increasing the complexity of the project.

            The actuators are connected using a pin type connector that tends to be stressed when the other actuator tilts the platform to either of its extreme positions. The connection is loose enough to allow movement, but would be susceptible to fatigue over a long period of time. This could be fixed by either using a different type of connector, or by simply making the connection lose enough to ensure no stress is induced.