What redundancy options do manufacturers have?

[RooEUC]

I see talk of redundancy in newer EUC designs and this is something that really interests me.  I don't like the feeling that I could lose my front teeth and break my nose and arms at any moment if the power cuts out.  But as these are single wheel self-balancing devices, just what are the options manufacturers have with current technology for keeping us upright in a system failure scenario?  The motors themselves are pretty robust and have a very low chance of failing, so the controllers, batteries and wiring are where most of the failures happen.  I wonder if one day we will have parallel controllers that can handle the load individually and switch over rapidly in the event of one failing.  Wiring is easy to make safe with good construction and pre-sale testing procedures.  Batteries can fail but wouldn't it be great to have a much smaller secondary high discharge battery or super capacitor that takes over in the event of a main battery failure and that will allow 20 seconds of balancing time so you can come to a safe stop? 

[Chris Westland]

57 minutes ago, RooMiniPro said:

I see talk of redundancy in newer EUC designs and this is something that really interests me.  I don't like the feeling that I could lose my front teeth and break my nose and arms at any moment if the power cuts out.  But as these are single wheel self-balancing devices, just what are the options manufacturers have with current technology for keeping us upright in a system failure scenario?  The motors themselves are pretty robust and have a very low chance of failing, so the controllers, batteries and wiring are where most of the failures happen.  I wonder if one day we will have parallel controllers that can handle the load individually and switch over rapidly in the event of one failing.  Wiring is easy to make safe with good construction and pre-sale testing procedures.  Batteries can fail but wouldn't it be great to have a much smaller secondary high discharge battery or super capacitor that takes over in the event of a main battery failure and that will allow 20 seconds of balancing time so you can come to a safe stop? 

... all great ideas ... especially alarms + limiters + supercapacitors to make sure that you have the power you need on tap ...

[Gimlet]

It's a bit like a helicopter, they are totally reliant on one rotor and we are totally reliant on one wheel.

Helicopter redundancy is achieved by have two motors both capable of driving the rotor independently. This is the only solution I can see ever working on a euc, but the weight penalty would be huge, double all the heavy parts, motor, battery plus a second controler and whatever would be needed to get it all to work both together and independantly.

So not totally impossible but not possible with the hardware we are limited to at the moment.

[RooEUC]

12 hours ago, Gimlet said:

It's a bit like a helicopter, they are totally reliant on one rotor and we are totally reliant on one wheel.

Helicopter redundancy is achieved by have two motors both capable of driving the rotor independently. This is the only solution I can see ever working on a euc, but the weight penalty would be huge, double all the heavy parts, motor, battery plus a second controler and whatever would be needed to get it all to work both together and independantly.

So not totally impossible but not possible with the hardware we are limited to at the moment.

The helicopter analogy is a very good one.  The funny thing is, in the hands of skilled pilots, even helicopters can auto-rotate down to the ground safely in the event of an engine failure, whereas we can do no such thing when our motor controllers shut off - we just fall instantly.  I do not agree that having two motors is the only way and that redundancy is impossible at the moment.  Good brushless electric motors are very reliable now.  When EUCs (and electric personal transporters in general) fail, it's usually other electrical components that fail, rarely the motor.  Controllers, batteries, wiring and software are the main parts that need redundancy.  A second controller would add barely any weight and a small backup battery/super-capacitor would add very little weight at the gain of protecting us from bodily harm.

[OliverH]

A quick overview on possibilities;

• There're motors available with dual stator so one stator needs to be driven from each motor driver.
• 6 phase motor with 2x 3 phases
• double layer winding with 2x 3 phases (shouldn't work properly)

In general will give us the new models with tubeless tires and wider tires/ rims more possibilities to create redundant concepts. Motor, motor driver, control board, Gyro, battery - all can be build redundant.

 

[DaveThomasPilot]

EUC power redundancy doesn't need super-caps.   Just use parallel cells for the redundancy.  The connectors may be less reliable than the battery, but you have that issue with a super cap too.

Yes, our situation is much worse than a helicopter.  Learning to do an auto-rotation is basic training for a helicopter pilot.

A 6 phase motor with 2x3 phases with each set of three phases being driven separately would make me feel a lot better.  But, it might be pretty tough to get the control loop fast enough to respond to a failure of one side to prevent a face-plant while not being too responsive to maintain stability when both sides are active.   It seems that development of the control loop dynamics is an empirical process, based on the issues that surfaced when the first 84v wheels came out.

Real redundancy would probably approach 2x, but I'd pay for it if it could be demonstrated that a large fraction of single point failures wouldn't cause a face plant.