Quote:
Originally Posted by BrianG
A little off-topic here, but I think the "ESC" should be programmed not to stop on a dime from the "catch up" time, but rather slow down over time. Same idea for the acceration part too IMO. In process controls, that is known as integrating. Regen voltage/current is a function of the amount of magnetic flux "stored" in the motor, the weight of the payload being forced to stop, and the stopping time. Since the first two aren't easily changed, that leaves the time factor.
As far as the NiMH issue; it's true they have higher resistance, but remember they simply cannot provide the current levels that any decent lipo can. I'm sure there are ripple currents with NiMH too, but since overall current is lower, so is the ripple. Of course, since NiMHs have a higher resistance, they heat up a lot more, which brings other issues, but that's not the point here. IIRC, a good NiMH can output 100A, but the voltage drops substantially. So, on takeoff, current peaks and voltage sags a lot. As the vehicle nears the v set speed, current dwindles and voltage climbs back up. The effect is a more gentle acceleration. Kind of like a forced punch control when you think about it.
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It is a little off topic, but it illustrates the point that the manufacturer knows about this and has a fix. Also only the RT3 (currently ver 2.13) is capable of such commands, which are stored in a databank and are run when preset conditions are met. it's kinda like ladder logic and at present we have been Beta testing it when time permits. The motor is more suited for pick and place not a conveyor, Although the manufacturer said that a conveyor would be way more easy than constant starting and stopping. but it's the only thing that we can send commands serially. I was hoping to work with Castle on a new setup, but.....
When I first got my MM/7700 combo I used Duratrax 4200's and they did pretty well for a while. I bought the eagle tree and I saw peaks of over 125amps and the pack voltage would drop to about 5.5V, so I bet a Good set of NimH would put out a little better. It also makes me think that since the MM was intended for high Kv motors this kind of problem hasn't come up as it has with the MMM on 6S, with a low Kv motor and a ton of weight.
Jeff
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