| Speed Controllers and Power Of course none of this would have been possible
without losing our bulky 4QD speed controllers. Storm II with its weapon
needed 3 speed controllers, all capable of exceeding the performance of the
4QDs, yet they had to fit into the same space as just one of the 4QDs and that
included the interface to the RC kit and the mixing/failsafes. It was only
by swapping out the 4QD controllers that we were able to buy back enough space
inside the robot to fit the weapons system in. That and we kept breaking
the 4QDs - they simply weren't up to the job of running Storm II. We were
actually cracking the PCBs !
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CAD Modal of Power Stage
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We turned to the two
roboteers that we consider experts in the field of RC interfaces and speed
controllers. George Francis and Dave Gamble. We knew that Dave
was keen to see Storm II live up to its full potential, and that he felt
that the 4QD controllers were holding us back. He was also keen to
develop new ideas based on the very reliable 'Tornado' speed controllers
that had driven them to so many victories. Dave felt that the first
improvement would be to use a PIC for decoding the incoming signal from
the receiver - and for that we turned to George Francis. It may seem
hard to believe, but at the core of the Storm II speed controller there is
the control circuit of the H5
controller that he sells. This is coupled to Dave's analogue
section which looks after the FETs and the 'power' side of the system.
Team Storm then looked after the physical
design of the controller which you can see modeled in CAD to the
left. It fits 3 x 230amp speed controllers into a physical space of
around 90mm x 250mm x 50mm. The controller uses just 4 FETs per
channel, hooked up by thick watercut copper busbars. At either end,
held in Lexan holders are the capacitors that sit over the incoming power
feed to the board. The logic board which drives the FETs and is the
domain of Dave and George sits above this.
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| The FETs that are used in the
speed controller are 230amp 100v Fets - we could have used higher current
FETs however we had concerns that although they are 'rated' for higher
currents, that they were limitied by the performance of the packaging that
the FET came in. For this reason we chose to be conservative.
The previous controllers - the 4QDs were current limited to 200amps, and
the new controllers with their improved ramps, and slightly more current
should perform better without the need to vastly up the current.
There was also the problem of heat.
The controller fits 12 of these FETs into a physically small space (250mm
x 50mm x 90mm roughly) and we weren't sure just how much heat would be
dissipated into the 8mm thick Aluminium base plate when running in combat. |
The completed Controller
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Additional model of power stage |
The power stage during development
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