Monday, 20 January 2014

Voxel Project (Part 3)

During the Snowdonia hackademia retreat in November 2013 the voxel project made a massive evolutionary jump. Virtually the entire week was spent on the manufacturing and construction of a mega control cube. This cube would power 12 servo syringe modules, each of which would be connected to a voxel cube edge.

Each servo syringe module followed the same oil rig design first tested in the previous post 'Voxel Project (Part 2)', however the arm was extended to provide better power transfer and the Lego motors were replaced with high torque servo motors. To allow for easy wiring all of the twelve modules were attached together to form a 3 x 4 mega control cube. All of the servos were connected to an AdaFruit servo controller board and from there to an Arduino Mega control board. A huge huge thanks goes to Boris and Rollo for all their help with the sawing, screwing and fiddly nut fastening that went into making each module.

The control cube now allowed twelve hydraulic syringes to be powered simultaneously and with adjustment of the servo timing and rotation rate a smooth motion of all syringes could be maintained. One issue that did arise was if a servo got stuck or drew to much current then all other servos would behave erratically until the issue freed itself, the system also continually looked for the weakest point with screws, nuts and lego parts often working loose. 

Unfortunately most of the week was spent building the control cube and very little time was available to work on the actual robot cube itself. I did manage to put together codename: SpongeBot. This robot was constructed from the same dual syringe setup used in codename Squeaky (see Voxel Project part 1) but the corners were made from plumbing parts to give a more stable corner, the edges were made from car wash sponges to allow the edge to bend and flex as required. There was no time available for actual experiments but we were able to create Arduino scripts (many thanks to Chrisantha) to put both the control cube and SpongeBot through its paces. Video below shows the SpongeBot left, control cube centre and the laptop controlling the action on the right (video was kindly made by Rollo and is time lapsed as actual speed was a tad sedate.)

Overall I am extremely happy with the progress made over the retreat and the SpongeBot robot. There was a huge amount learnt during the construction and testing that will be applied to the next generation. 

-- update --
Main things learnt, that will need modifying: 
a) Construction and transport - Both the robot and control cube look amazing and in the case of the control cube, scary! However transport has been an issue and this should be taken into account and an effort made to either shrink the control cube or at least disassemble into smaller parts. 

b) Storage - On the same note as above the cubes are currently connected together by hydraulic tubes, this means the whole apparatus has to stay rigged up in one piece and takes up considerable space. 

c) Hydraulics - For the SpongeBot cube we needed to use hydraulics as air was simply to compressable to get nice fluid movement (if any) but this did mean that the syringes and pipes needed to be filled with water and then connected up to the control cube syringes. Inevitably air entered the system which in turn reduced the effectiveness of syringe system. It would be nice to have some form of reservoir system to remove trapped air. Again during storage and movement it meant there was a chance of water leaking out, so emptying and top up process would be nice.

d) SpongeBot components - The plumbing parts used to make SpongeBot made a considerable difference compared with the original squash ball setup, providing well needed stability. However these were also easily damaged during transport and storage. The other issue was once a syringe piston had been removed from the syringe it never had as good a seal as originally, so often leaked. It would be nice to have a setup where the syringes could be left intact during construction. Finally the sponges used for the edges provided a nice flexible edge but as can be seen in the video hamper any form of locomotion as they are deeper than the corners and the movement is simply centred around them. 

To do:
a) Create a new cube capable of locomotion
b) Enhancements to the control cube to rectify some of the problems above

Few pics:

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