Leg Cart Progress

Well, we just wrapped up our second class session. We kept lecture time pretty short – we only did a brief introductory presentation on steel weldments (which you can check out here) and reviewed a couple of homework assignments from the first class – and then spent most of the class on (a) prepping the controls team to work with the upcoming Leg Cart simulation and (b) coordinating the mechanical team’s build progress. James or Dan will post some simulation videos soon, but in the meantime I thought I’d show off some of the mechanical work.

To get started, let’s review the hardware we bought before class, starting with…

Our "new", 135 HP Toyota 2F engine
The pump and driveshaft that match the engine

One of the sets of decisions we made as instructors early on was deciding on the powerplant. We needed something that provided sufficient power to provide hydraulic fluid for a 1-2 ton robot, that was (a) robust, (b) relatively affordable, and (c) as off-the-shelf as possible. We decided to rip the hydraulic powerplant out of a forklift (specifically, a Toyota FGC-45 from 1991) and repurpose it. The net result is that we have a 135 horsepower, propane-powered powerplant that produces upwards of 35 gallons per minute of hydraulic fluid at 2,500 psi. The fact that it’s propane fired means the robot can operate for brief periods indoors, and also means that we can swap industrial-grade fuel tanks good for 6 hours of runtime without having to custom build or fill any of the fuel system components.

So that’s what we have – what we’re working on now is making the Leg Cart, our prototype hydraulics platform. The idea here is to make a platform on “rails” (i.e., only able to move in one dimension) that has a single leg and a hydraulic powerplant on board (we’re borrowing the pump from our full system and running it off of a giant electric motor). This will be the students’ introduction to hydraulic systems, so we’re building something small (relative to the final system – the cart will still be 600 pounds…) at first so we can screw up and figure out what we’re doing. Without further ado, here’s the progress we made on the cart chassis in the past week:

The Leg Cart chassis as of 4/26/2012

Spark and Mac have been working hard at it for the past week or two – good work guys! Next up, we have the base weldment for the arm pivot:

Base weldment progress as of 4/26/2012

Adam and Andy teamed up to work on this over the past week. Unfortunately, some material was backordered, but we’ll be resolving that shortly.

Joel, Joe, Mike and Jona are all working on parts that are heavy on machining and low on welding, so we’ll see updates from them a bit later on in the process.

That’s it for now. Keep an eye out for an update on simulations!


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Gui Cavalcanti received a General Engineering degree with a Robotics concentration from the Olin College of Engineering. He worked as a robotics engineer and systems integrator at Boston Dynamics, working on cutting edge mechanical design and systems integration for highly dynamic legged robots like BigDog, AlphaDog, and PETMAN. He was the Systems Integrator for the LS3 project, coordinating the joint engineering and development of multiple subcontractors and engineers. Over the course of his career he has also developed the mechanical systems for a robotic tuna, several robotic snakes, an ornithopter, and several other robotic animals. In his spare time he builds ridiculous things with ridiculous people, like a flotilla of SUV-sized rubber duck boats to take on the water on the 4th of July.

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