Rule 6.3 The Link

[m2xt]

Rule 6.3 The Link

This is indeed a complex issue because of the variety of control systems employed on our bots. I would argue that all arenas running heavyweights must be able to cope with a runaway bot (the same could not be said just 2 short years ago!). However, I believe we must not only consider what happens in combat but also at home and during testing. The FRA as a competent body should at the very least make this an advisory rule for now while further research is made.

I for one feel the FRA should be congratulated on trying to make our sport as safe as practicable even if it has not fully understood the impact on existing bots of rule changes like this.

Paul

[blazerbotics]

Rule 6.3 The Link

so are you basiclly saying that all Rxs must have a power switch, no matter how they are powered? if you run off a BEC why would you want the main power on but the Rx off?

[m2xt]

Rule 6.3 The Link

Im not saying that, I agree that it makes sense that a robot should come to a halt if it loses receiver supply. Whether it should be part of a tech check is questionable as long as the arena is of suitable class. Appropriate design should infer the correct functionality. This is a personal view I should add

Paul

[Guest]

Rule 6.3 The Link

Alan, if I have been reading this correctly the switch on the rx is there to test the failsafe system so the roboteer can prove during tech. check that a power loss to the rx will fail safe. Any means of powering the rx - BEC, battery, elbow-grease - can come unplugged, leaving the main power live but the rx dead.

In an arena it will make no difference, these days, but during testing at home and possibly during power-up something like this could prevent accidents. Of course, Im afraid many roboteers will only think about their failsafe system the day before they are due to get tech. checked...

[team_ireland]

Rule 6.3 The Link

Would it be satasfactory if my pneumatic weapon was stuck in the closed position (it is locked in a simular way to DanTomKia and Bigger Brother).

At the moment my robot is set to bring the flipper down if failsafe pops in (due to the fact that if someone is in there and i turn on failsafe i dont want the flipper to fly up and hit someone). But it is failsafed by a FS-1 and will stay in the last position if I lose battery power. Is this legal? If not how can i get around this?

Regards
Ian

[blazerbotics]

Rule 6.3 The Link

sorry paul it wasnt aimed at you, i agree with you. Ian i think as long as your flipper remains in one posistion your ok, i think it just to stop your flipper going mad!

[fluppet]

Rule 6.3 The Link

Richard - Im a bit wary of the assertion that a modern arena should be able to contain any rogue robots.

Gary may only have been able to damage a side panel in Mentorns arena, not the frame supporting it, but that might not stop a low profile spinner which has decided to stick in drive from being able to get through. 8645T was making a credible attempt to burrow under the arena wall in Debenham. To drive through deliberately would require effort, but its still something which could happen if a robot gets stuck in drive.

If thats not likely enough, theres always the old chestnut of a flipper throwing a spinner into the wall. If Atomic had got T2 over the wall and the impact had caused T2 to do what happened to Behemoth after Mute hit it, bad things could have happened - Makrolon shrapnel at least, and possibly a completely rogue machine.

A modern arena should take any single hit thrown at it (with the possible exception of a big spinner thrown at the outer wall) with an acceptable level of safety, but extending that to an arbitrary number of hits is asking a lot.

It would be very unfortunate for circumstances to combine to endanger the crowd, but the first time it happens (ignoring the idiots running without a screen wherever it was in the US) would be catastrophic for the sport. This is always going to be a somewhat dangerous sport, especially for the roboteers, but lets not take it for granted that the arena will contain everything?

--
Fluppet

[Guest]

Rule 6.3 The Link

Um. Yes, good points there Andrew.

[the__kraken]

Rule 6.3 The Link

Drags a big spanner over to the works and gets ready to throw it in.

Just been going through the forum to see where I stand with the FRA regards my weapon control for my Hydraulic Jaw. At the moment, and how we ran it in Series 7, is by the good old fashion way of a servo and Micro switches controlling relays to operate the weapon. A FS1 failsafe was used in between the servo and receiver. (fine for the old Mentorn way)
However, reading this thread, and looking at the FRA rules again, I had failed to full appreciate that the robot must failsafe not only with loss of signal, but also loss of power to the receiver. To me this means that No servo/micro switch set up can be used to control weapons or drive systems as servos depend entirely on power to work.

Plus on my understanding, won€™t this also rule out failsafes like the FS1?

However, what grabbed my attention more, and got me questioning my whole system was something Paul mentioned,
Quote,

€˜Sam, this requirement for the robot to place your robot in failsafe status when the Rx is off is a departure form the Mentorn rules. This will in effect mean that 4QD DCI boards and some PCM only systems no longer meet the FRA rules.€™

So some built in failsafes may also not operate with loss of power?
Help!
What can you do to systems that don€™t failsafe on loss of Rx power so they do?
Do the Team Delta RC Switches failsafe with loss of power for example?

[jim]

Rule 6.3 The Link

You can power the servos and failsafes from a separate power supply to the receiver. All thats required for them to function is common ground and signal wires with the receiver. Of course, if you lose power to the servos then your microswitches will stay in the same position forever.

I dont think powering the servos from a separate power source will increase safety, because its equally likely that the servos power will be cut as it is likely that the receivers power will be cut - but it would satisfy the failsafe on loss of RX power rule.

[mark_m]

Rule 6.3 The Link

Theres a couple of things you could do.
Servos can be fitted with return springs so that they move to the off position on loss of power. This is very difficult to get right though with standard servos as they have lots of friction, but if higher quality servos are used, like coreless ones, they are relatively easy to back-drive. Most serious nitro RC car drivers use them (throttle return springs).
The other way would be to have a main power contactor. this could be fed from a smaller relay that was powered by the reciever battery. That way if the reciever lost power, everything would loose power.
Admittedly these are all one more thing that can go wrong, but if you already had a main power contactor, as a remote off switch, like some people have, it wouldnt be that much more complicated to implement this idea.

Mark

[the__kraken]

Rule 6.3 The Link

Jim, I see what you€™re saying, but as you said, you could loose any power sources to the servo and end up having a micro switch stuck in the €˜on€™ position. As you say, it could get you around the tech check, but I feel there would be a false sense of security about doing this. It wouldn€™t make it safer.

Mark, again I see where you€™re coming from with the return spring, and I think we may have had this discussion on the old RW forum.

On your idea of one main power contactor, One Relay to cut all power to everything. This was how my Robot Victor worked way back in Series 2!
We had all Drive and Weapon power running through a Relay which was activated by a servo/ micro switch set-up. This servo was connected to a failsafe, a G M Services one back in those days, that would cut main power if signal was lost. And just to show how things have moved on, that was the one and only failsafe we had in the whole robot! We stopped using this set up when the removable links were brought in.
This idea could be updated, but my question would be, what would you replace the servo/ micro switch set up with to activate the Relay, which would work if the Rx lost power.

At the moment I have three types of failsafe in my robot, GWS FS-1 units, and the ones built into the Team Delta RCE210 Relay Switch, and the Delbots weapon interface. I€™ve dug out the instructions for all these and all say failsafe mode will activate with loss of signal, None mention anything about loss of Power.

Looking at it, I€™d imagine that the RCE210 would failsafe with loss of power. The FS-1 would fail to de-activate what ever it was connected to with loss of power, and I€™m not sure about the Delbots Board.

Any help, advice or comments would be greatly appreciated.

Guy

[jim]

Rule 6.3 The Link

With regards to the main power contactor, you could run the power for the contactors coil through a small 6V relay powered by the receiver power supply, then through the microswitch which the servo activates. Arrange for the 6V relay to be downstream of the receiver to minimise the chances of a cut wire leaving the relay powered while the receiver is not.

Regarding servo power - I wouldnt recommend any way of getting around tech checks, it was more to point out a possible flaw in the rule. There are also legitimate reasons for running your servos on a different power supply to the receiver.

[the__kraken]

Rule 6.3 The Link

Jim when I said getting around the tech check, I didnt mean it in as breaking rules. I was just trying to echo you point about and any power source standing the chance of being cut/lost.
I see where you coming from with the relay running off the receiver power. You could probably do something with out using the servo and micro switch. I still use a switch to switch on my Receiver. You could take a feed after this switch to power a small relay, which in turn powers up a larger relay, which would be inline with the link, which has all power running through it for drive and weapons. Loss of Rx power would shut the relays down, shutting down the Robot.
I guess keeping in the servo and micro switch would give you a remote kill option.

Next to this, any views on the built-in failsafes I mentioned?

Guy

[roger_plant]

Rule 6.3 The Link

If you use a relay, powered by the receiver power, to supply to the micro switches you will get the same effect as cutting the main power without having to use a heavy duty relay in line with the power link.
i.e. if the receiver power fails, the small relay drops out, no power to the micro switches, no power to whatever the micro switches were controlling, even when the servo operating them loses power and stops where it is.

If you are using interfaces that do not always failsafe by removing the drive to your speed controllers, then power them via the same small relay as well.
That will remove the drive to the speedos.

I have experimented with heavy duty relays to cut the main power and found two main problems with them.
1) Their contacts can bounce open with severe shock.
2) They are not cheap.

Using a 12 volt car starter relay via a resistor from 24 volts is hopeless, they over heat long before the end of a five minute bout.

Reliable 24 volt heavy current relays cost about £30.
They are not easy to find second hand either.