© 2014 carnegie robotics llc. use or disclosure of document data is subject to the restrictions on...
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© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 1
Lessons Learned
• The most important lessons learned.® Budgets should always be closely monitored and even then they tend to be
adjusted and changed® Be quick to react to changing requirements® The best engineers never get attached to designs, they can scrap and finish a
project no matter the issues and set back are part of the norm® The problem is never fully finished
– I constantly wanted to fix problems but had to limit myself to getting the project to a stable point, there is always an issue that can be better but sometimes you have to cut your losses
® Even if you are not the sole lead of a project it is never a bad idea to push other to achieve the set goals, it’s a team project
® It pays to ask other for help, suspension systems are not easy finding individuals to help you with ideas pay off ten fold
® Trust your gut, people may tell you what the “norm” is for a certain application, but do research, why is that the “norm”. In some situations (like mine) it didn’t make sense so I questioned it and formulated a new set of ideas
® Have good problem solving skills, I came in with exceptional mechanical skills, from welding to rebuilding small electronics, and you never know when those will come in handy
® Always stay curious, sometimes the best ideas come from just looking at old ideas
® Lastly, don’t ever rule out a possibility till its been tried, sometimes the ‘dumbest” ideas can pay off
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 2
M.A.R.S.U.P.I.A.L. Mechanical Improvements
• Problems® Leading Incline is too steep® Overall height may be too high
– Raised CG® Self Leveling issues® Horizontal spring to stiff® Air shocks cant handle the cold® Reverse direction of tensioning® Track friction
– Too high inside– Too low outside
® Size of lower idler wheels
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 3
Leading Incline/Overall Height
~67 Deg
• Remedies® Lower leading wheels® Lower overall height
• Benefits® Aids climbing over objects
– Allows for ease of the first idler wheel to travel up and over
® Greater speed when traversing obstacles
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 4
Self Leveling
• Cause® Air spring are constant force meaning they are always in equilibrium
• Remedies to existing® First try was to add a spring between rod end and shock
– Springs were not strong enough and were fully compressed® Next try is applying large coil spring over entire shock® Increased spring constant and added spring compressive length
• Benefits® Maintains parallel plane to ground
• Remedies for new system® Added motor inside main Christie
– Ability to actively move CG
• Benefits® Actively adjust vehicle baseline® Actively adjust CG when needed
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 5
Air Spring Problems
• Lower tension in horizontal spring
• Potentially revert from tension springs to compression
• Manage environmental concerns® Encase the air shock in sealed container
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 6
Direction of Tensioning
• W-style active tensioners currently
• Two up force tensioners on the outside® Reduces wrap on motors® Using torsion for upforce
– If too much slack in belt can cause tensioners to flip forwards
• Remedies® M-Style with vertical forces applied
– Gives more wrap on the drive wheels– Removes possible over rotation of clock springs
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 7
Track Friction
• Full PVC track, steel banded® Double sided with guiding feature
– Thought was to be able to dig into the ground and stair ledges ® PVC had largest friction constant, however this is inside and outside,
requiring more than necessary torque to drive
• Possible Remedies® Add nylon facing on inside® Rethink double sided and instead use higher coeff backing® Can have machining done to the backing easily for custom profiles
© 2014 Carnegie Robotics LLC. Use or disclosure of document data is subject to the restrictions on the title page Page 8
Possible Backings
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