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Magnetic Gap Robot Pair

Project Description

Project Description

This project is the continuation of the work of Andrew Marchese and others - see "Controlling the Locomotion of a Separated Inner Robot from an Outer Robot using Electropermanent Magnets" by Andrew Marchese, Harry Asada, and Daniela Rus published in the Proceedings of ICRA- which describes a robot that uses electro-permanent magnets in order to attract a inner robot and an outer robot across a gap. This project was funded by boeing with the potential application of using robots of this type to help perform machining operations on the skin of aircraft. Airplanes are too large and have too many difficult to access spaces to economically use existing CNC factory automation robots for much of the assembly work. There is interest in using electro-mechanical clamp-based robots that can drive over the complex 3d-surfaces of the airplane that could potentially be guided by precise indoor positing systems in order to drill holes and instal rivets into the airplanes.

My part of the project was to redesign the robots so that they had improved functionality. The goal was to give the the outer robot the ability to perform milling operations, and to give the inner robot the ability to climb over obstacles. In order to outfit the outer robot for milling, I designed a single axis ball-screw actuated gantry, and applied many of the elements of what I learned in the MIT class 2.72 in its construction. The actual milling spindle was simply a battery-powered dermal tool. This off-the shelf capability greatly simplified the cost, the usability and the design complexity of the system while providing decent performance. After designing the unit in Solidworks based on the previous version - I made one more set that can be seen below. The robot was mostly made out of water-jet 3/8 inch aluminum and 3d-printed parts in order to make the design cheap and quick to manufacture. Using pre-existing elements in the design was followed in order to make it as simple as possible. For example the drilling/milling is simply a cordless dermal tool riding on linear bearings.

This is a design rendering of one of the pair of robots. This one specifically is the inside robot that does not have wheels, but is dragged by the outer robot. It can however climb over obstacles (such as the struts in a wing of an airplane perhaps).

This image shows the outer robot. In our set-up this robot is outfitted with a drilling/milling unit that it can retract on the Z direction with a ball-screw that allows the robot to act as a mobile router or drill press on the outside of the surface.

This shows the Inner robot. This robots goal is to climb over truss segments while forming the magnetic circuit with the inner robot that holds both robots together. The large gears are powered by servos that go through a 1:10 gear reduction in order to lift the estimated 15 nm of torque.

This shows the front of the outer robot. Notice the really big coils - these are what connect the two robots - in order to learn more about these you are encouraged to look up the paper referenced in the first paragraph

Previous Work

This project was originally build build by Andrew Marchese of the MIT Distributed Robotics Laboratory. These are the CAD models of this original robots, which were improved upon as part of my work. While these robots showed the function of the magnet system - they did not have features such as the pivoting hinges and the milling unit which were added in my designs.

This is a computer design model of the original version of the robot for comparison.

This is a computer design model of the original version of the robot for comparison.

While the robot is covered with electronics - the size of the capacitor can be seen which is necessary for activating the magnet coils by comparing it with the quarter that is visible resting onto of the capacator.

Videos and 3D Models

This video shows the two robots driving connected by the electro-permanant magnets across a 3mm sheet of aluminum. The only force holding the roughly 10 kg robot on the bottom from falling is from the activated magnets.

This 3d pdf (must have 3d view enabled) shows the outer robot which contains the drive electronics and the tooling.

This 3d pdf (must have 3d view enabled) shows the the robot which is designed to climb over trusses inside of the airplane.