List of requirements for the connector used in Self-reconfiguring modular robotics, SRCMR

Last edit (19 Mar 2012):

Added Requirement 49. Totally quiet

The connector is one of the biggest challenges in SRCMR,
so I have compiled a list of all requirements that I think
are in any way relevant when designing a SRCMR connector.

I do not say that we need, or should even try, to satisfy all
these requirements in one particular connector.
On the contrary, I feel that choosing which of these requirements
to include and exclude when we design a connector might be
one of the most important and difficult choices in developing a
SRCMR system. I think that the list should serve as a reference
point and that we need to relate to the requirements on it when
we design a particular connector.

I will write more about the individual requirements and the selection
process later. As usual any comments are highly appreciated.

The requirements are not sorted in any particular order, or grouped,
that is something I will try to do in an update. So here is the list:

1. Reliable connect, and disconnect
2. Small (thin, low volume, compact)
3. Fast
4. Light
5. Robust (relates to requirement 1, 9 & 10)
6. Strong
7. Scalable (able to attach to copies of itself in different sizes so that we can connect modules of different sizes efficiently)
8. Easily producible in different scale (otherwise it cannot scale)
9. Degrade gracefully and predictably (if it is violently disconnected it shall be able to reconnect, if power is low it shall connect/disconnect, albeit slower)
10. Hard to foul/ easy de-fouling/ self de-fouling
11. High tolerance to alignment errors, when connecting
12. Solid state (no/as few moving parts as possible)
13. Easily powered mechanically from the outside
14. Transfer communications signals
15. Transfer electric power
16. Transfer torque (Thor robot)
17. Genderless, any connector should be able to connect to any other
18. One sided release (to be able to release a defective module)
19. Two sided release (requires both modules to release to decouple, makes it possible to hold onto a misbehaving module)
20. Able to connect on different approach vectors, and to do so simultaneously, this is useful when inserting a module in a tight lattice
21. Straight connect vector (no turning to fit X degree symmetry 90,180 etc)
22. Low internal forces (reduces the structural demands and actuator power)
23. Boolean, connected or disconnected and nothing in between
24. Reliable status indication on whether is is connected or not
25. Zero approach movement of the module to connect (connector can move but module shall not have to)
26. Common force center for all angels (is this more about how the connector us used when more than one is used in the same module)
27. Adjustable angle of attachment to keep force lines and angles under control, (useful in tensegrity systems)
28. Cheap to make
29. Easy to make in large numbers
30. Low tolerance requirements
31. Some requirements should be configurable in software when a solution is developed:, e.g. 18 One sided release, 19 two sided release and 9 Degrade gracefully
32. Consume power only at state change
33. Service and maintenance free
34. Disconnect gracefully when in use and force is applied to it and it is ordered to disconnect (not the same as 9)
35. Connect from one face and release from any other if used in a multi connector module
36. Zero backlash, rigid connection
37. Self centering of alignment errors
38. Rotational symmetry in inertia tensor, the connector mass should be balanced
39. Gripping force provided by both sides of the connector equally
40. Non blocking, when used in a multi connector module all connectors must be usable
41. An arbitrary number of Simultaneous Connect/Disconnect when used in a multi connector module
42. An arbitrary number of connectors must be usable in a module, so that the module designer can implement cubes, dodecahedrons etc)
43. Arbitrary arrangements in space of connectors on modules, so that the module designer can implement cubes, dodecahedrons etc
44. Not use excessive heat, current, voltages and pressures
45. Not use toxic or excessively reactive chemicals
46. Not use fluids or other small parts that can leek, break off and cause fouling)
47. Wide environmental operating conditions (temperature, humidity, vibrations etc)
48. Stable over time, for instance expected wear and tear shall not affect its behaviour and it should not use degrading materials
49. Totally quiet

Thanks for your feedback Christina, Mårten, Tom Larkworthy, Neil Desmond and Jonas Neubert