Saturday, July 20, 2013

Robot out for a spin for the first time

Sunday, July 7, 2013

Robot Building

Finally all the pieces are in place and I took the robot for a wireless ride around the house. The original VSI controller have been officially hacked.  The robot still retains all the functionality of the original VSI and also can be switch to Radio Control at the drop of a hat!
I needed to build a low pass filter for the PWM output from the arduino  and it worked out pretty well.
The fillers smooth out the PWM pulses as explained in this article

There is a noticeable delay when I move the stick on the RC transmitter, kinda  frightening when the see the robot takes off and does not respond to the stop command immediately!
I will play around with different values of resistors and capacitors in the coming weeks to increase the responsiveness.

I also had to re-write the code for the arduino that I posted some time ago, pretty simple indeed but It will get very much more complex when I  add bump, and ultrasonic sensors. These will be autonomic sensors to prevent the robot from bumping into things and falling off edges. etc. Ideally a visual sensor system  would be the navigation system of choice to prevent bumping  into thing and falling off steps and overhangs.

Next  on the list of  things to be done
1. I will tidy thing up a bit by using a arduino shield for the filters and a project box to host all the electronics.
2. Add support to the code for the horn and speed selector ( why do I need the horn working?)
3. Add bump sensors and supporting code
3. Add ultrasonic sensors and supporting code

Monday, February 4, 2013

Robot building

Wow! could not have imagine that 4 years has past since I started this project. Actually, I had started it with the hopes that one of my three sons would have jumped in and completed it. tsk...tsk...oh well here we go. Just to summarize: In 2009 I acquired a broken electric wheelchair to be used as a base for robotic projects. I stripped it down got it working and planned to tap into the factory controller. Today, I hacked the controller, extended the internal ribbon cabling with additional FCI 6 pin Headers and a 8 way rotary switch. Here is the initial plan
The Splice
From the controller's documentation they are 2 wires that control the forward and reverse motion and two that controls the left and right steering. Other wires are ground, 2.5 v reference voltage and 5 volts power. Time to check is the hack to see if the controller works, and it did! with a little bit of fiddling. (I did not pay much attention to the way the FCI connectors were originally oriented.) The FCI Headers were source from part number 89361-708LF The rotary switch is a generic one from ebay. The rotary switch is to be used for switching the forward/reverse & left/right input between other signal sources, for example RC receiver/ARDUPILOT or on board computer.