It's Aliiiiive!!! (and has a lengthy story)

 For the past 3 weeks I have been scrambling to get Inspiration operational again in time to present at the Girls in Aviation Day at the St. Paul airport last weekend (9/26/2015). Working 9 hour days means I usually only get about 4 hours to work on the rover each night. It's not entirely flight ready, but the bulk of it is done, now, and that is a very exciting feeling! I can now focus more on code and sensors rather than design-test-redesign.   

 To catch up with the past month or so, let's begin somewhere after my last blog post. I think the last post explained how much better Shapeways was at 3D printing than our Zeepro 3D printer. So we ordered the rest of the suspension parts from Shapeways and waited; it takes about 2 weeks from ordering parts to get them in. Unfortunately, I made a mistake several months ago while saving a servo bracket design and ended up sending Shapeways a file that was no longer useful. So when all of the parts came in, I had 2 parts that didn't work with the steering servos. A rush to order the correct part ensued since the weekend of the Girls in Aviation Day was coming up in just a few weeks. While I waited, I used the 2 bad parts as a stand in so I could work on the rest of the suspension.

 The new suspension required a longer shoulder mounting shaft to be cut to length and grooves to be machined in for the locking 'C' clips. I spent a few days going to different hardware and auto parts stores looking for the type of aluminum pipe from which I had made the previous shoulder mounting shaft, but didn't have any luck finding it. 5/16'' aluminum tubing is apparently hard to find. On a hunch, I stopped in at Ax-Man Surplus to see what they might have for aluminum tubing. After about 20 minutes of scrutinizing everything that might work, I found fiberglass tent polls. I asked for calipers to measure one and sure enough, an exact match! So now the shaft is cool-looking black fiberglass.

 After mounting the servos and servo brackets to the shoulder joint, I had to put the body on. I then piled in batteries and electronics to see if the suspension could hold the weight... it couldn't. The spring inside of the shoulder wasn't strong enough anymore to hold the new electronics I wanted to add. So Cristin and I sat down one day to bounce ideas back and forth and came up with the idea of putting a "locking" latch on each shoulder. Now, with the latches, when the rover is in flight mode, the shoulder arms will be spread out. After landing, we can command the front wheels to drive backwards which will raise the body and bring the shoulder arms together where the latch would then catch and keep the arms from spreading apart again. This latch can be seen in this picture:

Some days during my lunch break, I squeeze in a couple of pages of Sojourner: An Insider's View of the Mars Pathfinder Mission by Andrew Mishkin. (yes, I've been working on reading this for a couple of years now during down-time. You can actually see a picture of it in a much earlier post.) Oddly enough, in my own way, I've been on a parallel path with Inspiration and Mr. Mishkin's book. I come across an issue with the rover and then read about a very similar issue on Sojourner. This was the case with the shoulder latch. I thought for sure this problem was unique to Inspiration because of the inexpensive and easy way I designed the shoulder. So to my surprise, after coming up with a latching idea, I read about a very similar latch that they had to put on Sojourner. So I must be doing something right if I'm unwittingly following in JPL engineers' footsteps.  

Here is the suspension waiting for the electronics to drive it and the correct parts to come in the mail.

 After getting the suspension together, it was time to give Inspiration a whole new electrical system. 

 Over the winter, I programmed a way for the Arduino to sense battery voltage for 2 lipo batteries and switch between the two as one would drain and the other would charge from the solar panel. Making these changes between 3 power sources required 3 relays and a 4th for main power on and off. It also needed 2 more relays to turn the power to the camera and metal detector on and off. To feed these relays, I needed a board for the batteries to plug into and a couple of power rails on that board to supply power to the different systems.

 This new power distribution panel was also designed to eliminate the jumble of wires piled inside the rover's body which made access to the battery and components almost impossible. 

Here's an older photo kind of showing this pile of  wires:

Here is the new more organized wiring. Battery removal is MUCH easier, now, and access to the Arduino's USB port is possible if I need to upload a new sketch. 

  About a week before our presentation, Cristin came home and found me outside with this new power panel, 2 lipo batteries, and safety glasses on. She asked me why I was testing the power panel outside and I said that I didn't want the batteries to explode in the house in case I screwed up on the wiring. After some thought on how volatile lipo batteries can be, we decided that it was probably in everyone's best interest to not have the rover go up in flames during our presentation. (This was a mistake that could have ended our dreams of doing anything space related... or anything at all, really... had a battery exploded while pushing temperature limits) 

 We decided to fix this before it became a problem. I did some research on batteries and found these  7.4 volt 2600mAh Lithium Ion batteries and a nice little charger for them. They have a maximum temperature rating of around 450 degrees Fahrenheit which is way better than the 114 degree limit of the lithium polymers. These also have twice the power capacity so drive times are now around 2 hours per battery. The down side is that they are a little bigger and heavier... and needed to be in the rover within the next 4 days. We checked many websites and finally found one that had 2-day shipping on these batteries. 

 While we waited for batteries and parts, I started the programming for all 9 suspension servos. Getting the angles of the steerable wheels proved be a bit of trial and error. The Maestro controller didn't really work with degrees. Instead it worked with numbers from 5000 to 7000. 6000 being center but my brackets weren't mounted exactly straight so each corner servo had to have a different number for straight. One would be 6015 and another would be 5998. And then turning them inwards at around a 40 degree angle took even more tweaking. After a few hours, I finally got the lines of code correct.

Here is a video of the first time the electronics and suspension were integrated together and tested with the correct code.

 Once I got the suspension operational, it was time to install the XBEE wireless receiver, replace the desktop power supply with a battery, and stuff it all into the rover body. Once I got everything back together and driving around on the floor, I couldn't help but set up a ramp to see how it climbs.

Here, I found that the slow speed setting was not providing enough power to the servos to get the front wheels to climb over the front of the ramp. Going at it in reverse worked out, though.

And then I felt daring:

 Inspiration was now a capable rover. By Thursday of that week, the parts and batteries came in and I could finally take a breath. With Friday available for extra work, I decided to get the camera arm and metal detector arm programmed and operational. It's always impressive to see the camera rotate up from its stowed position over the solar panel and then pan back and forth. 

 Saturday came and we arrived at Holman Field in St. Paul at 8am. We set up our display complete with red sand, rocks, and information about Sojourner and Donna Shirley who managed the Pathfinder project for JPL. We had fun talking about how Sojourner *inspired* our little rover, and that's why we named it Inspiration.  

 Inspiration was a hit at the Girls in Aviation Day event. Kids and adults would hang out with us for long periods of time asking questions about Inspiration and engaging in some great conversation about NASA and all of the other space programs around the world that are currently working on robotic missions to the Moon, Mars, and asteroids. 

 Photo credit: ©2015 Larry Grace Photography

 So now that we have some down time, I can focus on getting other systems working. Next up for Inspiration will be to get the 2-battery system fully functional, design and build a new metal detector that will reach the ground with this new higher suspension, improve the camera arm, get the ultra sonic range finder on the front working, and then work on the GPS autonomy and graphical interface. 

Lots to do yet so stay tuned and remember to chase the challenge!