Looks like a very interesting project coming along nicely.

That’s a good question regarding the torque. I actually haven’t done any measurements to more precisely determine the forces at play with actuating the leg joints and also keeping them rigid while dealing with the weight of the rest of the body.

What I can tell you though is that I’m using a wiper motor which has two different power input levels (determined by a single ground connector and two different positive connectors). The high input setup facilitates faster motor speed but lower torque levels and a decreased ability to handle higher loads while the low input provides much better torque capabilities. So I opt to run the power into the low-side input. I believe that this is the nature of many wiper motors.

I’ve been using mainly a 12 volt power supply but one with ample amperage output. I wrote moree about the batteries here: http://www.openexo.com/2011/09/new-batterie/. And when I use the device on my body applying load, the amperage draw can go up to 20-25 amps.

I am currently controlling the position of the motors during walking by way of a rotary encoder that’s fixed around the shaft of the motor. The value of this is then translated by a board within the motor housing and then output as an analog signal to an Arduino. The analog signal represents what angle/position the motor shaft is in. There is also an analog input on the wiper motor board where I can send a PWM signal to control what speed and in what direction I want the motor shaft to spin in. I then use fuzzy logic to make the shaft do what I want to do (initiate walking movements or standing say) by managing this input and output on the motor board with the Arduino. I have the code for this (not commented very well right now but it’s on my todo list) up on GitHub here if you’re interested:

https://github.com/eliotk/OpenExo

I’ve been looking at remotely operated vehicles (under water robotics) and there is an Open ROV project. Several University teams are involved in competitions to. It may seem that these projects are radically different from yours but they do tie into the open exo project because these other projects have experience and recommendations for keeping electronics protected from water and dealing with motors under water as well. (The two projects could share ideas on dealing with a wet environment. The exoskeleton project would be somewhat easier because the ROV projects typically go deeper in water, where pressure is greater. Some of the more advanced ROV projects/competitions have task that are very similar to your goals in that they call for fairly high torque tasks such as opening a hatch or transfering a weighted object from location to another.)

Do you have a resources page where links or articles that may relate to your project could be posted by visitors? If so, I could share links, videos, and articles as I come across them.

Thanks for your comment. What great goals for an open source exo. I like the way you think!

I’m going to work on a new post with detailed photos of the hip joint and my thoughts on constructing it from scratch. I’ll post it here as soon as possible.

You hip/leg part of the project is a key step in achieving my personal ultimate goal for an open source exo.

Modifying an existing hip brace is a good way to go. Unfortunately, they are not always available used or available a low cost. Do you have suggestions for creating your own hip joint from other materials? Can you provide detailed photos of your existing hip brace joint so I could make one with other materials? Do you have suggestions for modifications that would make a hip joint better suited for an exo project? (such as attachments or supports for electronics or motors?)