Master/slave hard start up suffers "stutter" problem#Solved

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parrotspain
Posts: 4
Joined: 04 May 2017, 15:38
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Master/slave hard start up suffers "stutter" problem#Solved

Postby parrotspain » 04 May 2017, 15:50

Hi,

We using pairs of 200kv outrunners as master and slave, non-sensored on 12s lipo. This is part of a fast responding robotic platform (100kg+).

When on the bench and separated mechanically, they synchronise perfectly and with some adjustments to Duty Ramp and Current Boost (reducing both), they start up, crawl, rev and reverse in nearly perfect sync. Battery current is amazingly low and the whole set up is stable in every way. Great torque too.

The reason we reduced those specific settings is that otherwise, sudden heavy transmitter stick movements resulted in stuttering and sort of hunting of the motors. This only appear on 12s lipo, it's completely absent at lower voltages. These adjusted settings cured the problem on the bench. 12s voltage is a requirement by the way.

When mechanically linking the motors a problem occurs. In slow movements from the transmitter all is well, but sudden demand once again creates this kind of stuttering. Current draw is still low, except at the moment the problem occurs, then motor current demand is high. When driven gently, there is no problem, only sudden heavy demand causes this and it occurs whether the system is inertially loaded or not. There is very little mechanical resistance in the gearboxes.

So, two questions. First any ideas anyone? Second, is there anywhere, we can find a full description of the Advanced functions on BLDC Tool? We are familiar with all of the basic controls, we know about the current ramp bug, we have used VESCs successfully in many other applications.

All help very much appreciated.
Last edited by parrotspain on 04 May 2017, 23:57, edited 1 time in total.

parrotspain
Posts: 4
Joined: 04 May 2017, 15:38
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Re: Master/slave hard start up suffers "stutter" problem #Solved

Postby parrotspain » 04 May 2017, 21:28

Further to the previous post, using sensored mode now, which we couldn't make work initially, we have good stable behaviour on one pair of motors, but the second pair occasionally glitches out. Guessing loss of sensor data might be to blame. So we're nearly there, all suggestions are welcome.

parrotspain
Posts: 4
Joined: 04 May 2017, 15:38
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Re: Master/slave hard start up suffers "stutter" problem#Solved

Postby parrotspain » 04 May 2017, 23:57

Footnote to previous two posts. Fixed a hall sensor connection, now working beautifully, from a crawl to a scream.

Leon
Posts: 3
Joined: 24 Apr 2017, 11:15
Location: Gothenburg
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Re: Master/slave hard start up suffers "stutter" problem#Solved

Postby Leon » 05 May 2017, 12:42

Video? :-)

parrotspain
Posts: 4
Joined: 04 May 2017, 15:38
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Re: Master/slave hard start up suffers "stutter" problem#Solved

Postby parrotspain » 07 May 2017, 10:46

Will do, we're on a steep hill-climb to complete the project, but will post something here when we can.


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