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Rotwang
Experienced Roboteer
Joined: 15 Jun 2004
Posts: 1589
Location: Vic
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Wooh! What a weekend.
It’s going to take me a little while to mentally digest all that input.
Lots of designs and strategies bubbling around in my mind and I have to try and work today, Dentist yesterday so I got most of the gear out of the van and did a few autopsy’s between eating ice-cream and sleeping.
Bane coped the most battel scars of our fleet, brand new it got to fight Jolt for its first fight; I opened with a box rush, Jolt managed to move sideways far enough so I just hit the wall where he was, then the announcer/judge started saying something and in my befuddled state I thought he was saying something about red lighting as I was in my old dragracer mode and had watched the tree come down and cut as good a light as possible.
Once I worked out what he was on about I lined Jolt up and set about ramming him into the wall trying to break or flip him, problem was Bane had almost no drive on one side.
I have a lot of old red wheels and a new pair for Bane was on the list but it didn’t happen, probably a combination of the overvolted drill revving fairly quick and the high polar moment of inertia with the long heavy pick and the dried out rubber tyre but the wheel was spinning in the tyre making it hard to drive and very slow to get the pick up to speed.
Still I really enjoyed the fight. Especially the last move when Nick counted my sit and spin by the old sit and spin, I figured he knew he was ahead and had nothing to loose by waiting me out so I came out of the spin, wedged him into the wall and the clock ran out with Jolt perched on top of Bane.
Matt drove it next as we forfeited our fight with Bender.
George has a history of getting the better of Matt and in a fight that I thought otherwise would have been fairly even Bane had another problem.
Rather than stick a self-taper through the wheel I outsmarted myself by pumping the cavity between tyre and rim full of urethane.
Bad move, not enough time to go off, the urethane oozed out making a clown wheel effect and bane lost all traction and vibrated and generally looked like it had square wheels.
Got to go part 2 tomorrow. _________________ Satisfaction is proportional to effort and results.
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Tue Jan 16, 2007 3:41 pm |
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Rotwang
Experienced Roboteer
Joined: 15 Jun 2004
Posts: 1589
Location: Vic
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Following up on Aaron’s hint about the Roboteq I found this thread in the FRA forum
http://www.fightingrobots.co.uk/forum.htm
This sounds exactly like the problem I was having with Bane version 1 with the overvolted rarer earth scooter motors.
At least I know the name of my pain now and it is “REGEN current surge”
Ian Mc Donald Advanced RoboteerUsername: Team_irelandPost Number: 434Registered: 11-2003 Posted on Friday, September 24, 2004 - 8:53 pm:
Hi Having heard a few stories about Perm motors "Technobot Power Drive motors" buring out Roboteq's due to them causing huge voltage spikes when sudden reverse is used. I was reading through the vantec website purely by chance and found this: " In this situation the batteries act as a voltage clamp protecting the controller. The battery chemistry must be healthy for this to occur. Don't add a series diode in line in the battery line because it will block the clamping action and the controller will fail. Some users place a large 100,000 ufd "computer" electolytic capacitor across the power going into the controller, a good idea, to further smooth the input voltage and clamping action." Could this work with the roboteq's and possibly stop the problem? Any idea's? Regards Ian
Mike Lambert Intermediate RoboteerUsername: GrafixPost Number: 225Registered: 10-2003 Posted on Friday, September 24, 2004 - 10:15 pm:
no.
Stefan Member RoboteerUsername: BugsPost Number: 99Registered: 10-2003 Posted on Saturday, September 25, 2004 - 2:55 am:
No, as in: it won't stop the problem.
Paul Cooper Intermediate RoboteerUsername: _m2Post Number: 175Registered: 10-2003 Posted on Saturday, September 25, 2004 - 3:10 pm:
Roboteq and Technobots are still working to find a robust solution to this problem, a problem which we now understand. The voltage spike aspect has been resolved but the curent spike is being worked on. To give you some idea, we estimate a current spike in excess of 2200A being generated by the Power Drive motor in regen. Two solutions exist, either cope with this current or reduce the current. Once we have a proven solution, the Roboteq will take some beating in the world of DC speed controllers. Paul
Mike Lambert Intermediate RoboteerUsername: GrafixPost Number: 231Registered: 10-2003 Posted on Sunday, September 26, 2004 - 9:49 pm:
See, ask a question and you shall get a good and honest answer from the man himself. Mike.
Kane Aston Member RoboteerUsername: KanePost Number: 58Registered: 10-2003 Posted on Monday, September 27, 2004 - 9:59 am:
The Roboteq already takes some beating in the world of DC speed controllers!
Stefan Intermediate RoboteerUsername: BugsPost Number: 101Registered: 10-2003 Posted on Monday, September 27, 2004 - 10:41 am:
Every pice of technoligy has it's quirks. There's no perfect speed controller, there probably never will be. At least not yet, mine is still on the drawingboard
Craig Danby Intermediate RoboteerUsername: Craig_antoPost Number: 244Registered: 10-2003 Posted on Monday, September 27, 2004 - 12:12 pm:
Tanto can run the power drives
james baker Advanced RoboteerUsername: JamesbPost Number: 495Registered: 10-2003 Posted on Wednesday, September 29, 2004 - 1:17 pm:
just a suggestion, could a 1 farad power cap from something like a monster car stereo install be used to absorb the backwash of current. These regularly see over 2000A in top installs. not looked into this, just askin
Kane Aston Member RoboteerUsername: KanePost Number: 66Registered: 10-2003 Posted on Thursday, September 30, 2004 - 4:27 pm:
No, well it could. But that wouldn't really fix the problem.
Paul Cooper Intermediate RoboteerUsername: _m2Post Number: 176Registered: 10-2003 Posted on Thursday, September 30, 2004 - 5:10 pm:
James The 2200A current is between the motor and the FETs, putting a cap like this across the motors would just be seen as a short circuit to the controller. Putting it across the battery would not resolve this particular issue. Paul
Craig Danby Intermediate RoboteerUsername: Craig_antoPost Number: 250Registered: 10-2003 Posted on Thursday, September 30, 2004 - 7:53 pm:
Paul if u willing to replace the controller if you blow it up (not that they should) I'm willing to let you try the 48330esc on power drives email me if u interested
Kane Aston Member RoboteerUsername: KanePost Number: 68Registered: 10-2003 Posted on Friday, October 01, 2004 - 8:57 am:
6.3lbs weight!!! 1 channel http://www.teamwhyachi.com/motor.htm That's 5.7Kg of speed controller for drive!
Craig Danby Advanced RoboteerUsername: Craig_antoPost Number: 257Registered: 10-2003 Posted on Friday, October 01, 2004 - 12:48 pm:
yea and? call it an insentive to loose weight
james baker Advanced RoboteerUsername: JamesbPost Number: 499Registered: 10-2003 Posted on Friday, October 01, 2004 - 4:12 pm:
thanks kane/paul, as I said, didn't look into it, just something from the old boyracer days
Knightrous Oxide Advanced RoboteerUsername: TeamvertexPost Number: 543Registered: 01-2004 Posted on Saturday, October 02, 2004 - 1:03 pm:
Maybe a small device that monitors the voltage on the motor wires what will switch the motor leads to a something that will burn up this voltage spike when braking until the voltage drops back to a level that the fets will take and then connects the motor back to the controller? I'm sure it could be done with a picaxe chip and some smart thinking. Just a brainstorm and I'm sure someone will pick holes in the idea.
Stefan Intermediate RoboteerUsername: BugsPost Number: 102Registered: 10-2003 Posted on Saturday, October 02, 2004 - 1:48 pm:
Euhmm.. hey you've got it all figured out I'm sure they'd have a solution if it where an easy fix. I'd try to use a higher switching frequency and a lower duty-cycle on regenerative breaking. But I'm sure they've tried all the easy fixes. Maybe they can't upgrade the cpld contents with the normal firmware upgrade software.
Kane Aston Member RoboteerUsername: KanePost Number: 73Registered: 10-2003 Posted on Saturday, October 02, 2004 - 5:17 pm:
You guys do realise that the maker of the Roboteq is working on this problem to produce a more refined fix!
Paul Cooper Intermediate RoboteerUsername: _m2Post Number: 178Registered: 10-2003 Posted on Saturday, October 02, 2004 - 6:45 pm:
Knightrous, the problem is current spikes rather than voltage. The Roboteq has built in hardware suppression against 'normal' voltage spikes and additional means of isolating the motor from the output stages built into the software. Some spikes from low impedance motors like the LEM and Power Drive have so much energy and are of such short duration that even this protection is not adequate. Fortunately this issue has recently been resolved and works well. The method of dumping regen energy into some switched load has been considered not just by myself but by other speedo designers I could mention and it is far from being a desirable solution. Stefan, it is all about the duty cycle but a lower duty cycle is what is causing the problem at the moment. You need to be able to detect when in regen and also measure the regen curent in the bridge but very few bridge designs appear to allow for this. You are also quite right that the firmware upgrades cannot alter all functions, some are embedded as you suggest in the PLD which includes how the bridge is controlled. We remain optimistic that a solution exists and I certainly do not mind suggestions, you never know it may just prompt a new thought process. Thank you to those who have emailed direct with suggestions. Paul
Paul Cooper Intermediate RoboteerUsername: _m2Post Number: 235Registered: 10-2003 Posted on Friday, January 21, 2005 - 3:31 pm:
Following both successful bench and field trials (thanks to Dantomkia Mike), a new version of the Roboteq is now available - AX2550HR. The development has also led to improvements on the standard version. A new version of the software will be available next week (waiting for me to upload) which will amongst a number of continual developments now feature regen current monitoring. What this means is that the controller will send a minimum of 25% of the regen current back to the batteries until it falls below a fixed threshold. Once it falls below this threshold, the controller will bring the motor to a halt. Effectively this means the deceleration ramps may be paused during periods of high regen current. This is very unlikley to be even noticed with motors such as the Bosch 750W, it's there for LEM's and Perm Power Drives etc. There is also a small hardware mod of 4 diodes to cope with spikes during regen. All motors generate these spikes and the standard Roboteq can cope with these for motors except the disc type LEM's etc. There is a risk that a faulty motor could also generate these spikes. These diodes are fitted to all units shipping from 1 Jan 2005 but can be retro-fitted to previous controllers. Even with these changes, the disc motors (especially the Power Drive) still generate enormous regen currents so a new version is available that has twice the number of output FET's which means is can cope with twice the regen current as well as running cooler. Existing standard controllers can also be upgraded to the HR version. It would be unrealistic to say that the Roboteq is now unbreakable, but surely it must be close. See here for further details. Paul
Kane Aston Intermediate RoboteerUsername: KanePost Number: 123Registered: 10-2003 Posted on Tuesday, January 25, 2005 - 1:26 pm:
Yipee!!!
Mr Stu ModeratorUsername: StuPost Number: 721Registered: 10-2003 Posted on Tuesday, January 25, 2005 - 4:24 pm:
Yeah - go get a Roboteq in Behemoth now Kane, learn how to drive with a good accurate control speed controller - no excuses now - you can't blame the 4QD's for your driving now, hehe. Mr Stu _________________ Satisfaction is proportional to effort and results.
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Sun May 06, 2007 9:14 am |
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