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Post by 5natural5 on Sept 17, 2015 16:18:03 GMT
For my 6dof rig (top platform 150 kg total weight and motor arms of 0,1meter) I'm planning on using 6x 90:1 DC gear motors with a nominal torque of 55Nm at 43 RPM and 29Amps at 24 Volts each (according to the the datasheet).
In the RPM range that I will be using the platform (14-30 RPM) the motors kan deliver 236 Nm (at 14 RPM while drawing 106 Amp) and 138 Nm (at 30 RPM while draing 60 Amps); again according to the datasheet.
Since six motors will work simultaneously and the top platform (with one person) is relatively light, I think it will not use the available torque or draw the required amps at the given RPM's.
However, I have absolutely no clue at which power supplies I should get. I'm planning on driving the motors with 3x 2x60 Sabertooth motor controllers.
Do I need 3x power supply with 240 amps each (allowing for current spikes to 120 amps) or will much smaller power supplies suffice because the platform is much lighter and won't require the available torque and therfore draw the required amps.
Do you guys have any ideas on this topic? Any help is much appreciated.
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Post by clyevo on Sept 17, 2015 16:56:23 GMT
even power supply has continuous and peak rated, so that counts. But the peak value is not far off from the continuous rated power. Maybe you need power supply that can peak (106 x 6)amps. Sharing power supply is better because not all motor will be at highest power consumption at the same time.
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Post by hexpod on Sept 17, 2015 19:11:03 GMT
For my 6dof rig (top platform 150 kg total weight and motor arms of 0,1meter) I'm planning on using 6x 90:1 DC gear motors with a nominal torque of 55Nm at 43 RPM and 29Amps at 24 Volts each (according to the the datasheet). In the RPM range that I will be using the platform (14-30 RPM) the motors kan deliver 236 Nm (at 14 RPM while drawing 106 Amp) and 138 Nm (at 30 RPM while draing 60 Amps); again according to the datasheet. Since six motors will work simultaneously and the top platform (with one person) is relatively light, I think it will not use the available torque or draw the required amps at the given RPM's. However, I have absolutely no clue at which power supplies I should get. I'm planning on driving the motors with 3x 2x60 Sabertooth motor controllers. Do I need 3x power supply with 240 amps each (allowing for current spikes to 120 amps) or will much smaller power supplies suffice because the platform is much lighter and won't require the available torque and therfore draw the required amps. Do you guys have any ideas on this topic? Any help is much appreciated. "150 kg, 0,1meter, 90:1 DC, 55Nm"
human = 70kg+ Playseat + wheel = 50kg upper platform metal parts = 20 -30kg
I am afraid you are on the edge. I would advise a bigger margin. I would go slower with more torque (around 25-30 rpm)
cheers.
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Post by 5natural5 on Sept 18, 2015 7:49:06 GMT
Thanks for your suggestions guys! I will take them to heart. So... I'm going to need some pretty hefty power supplies from the looks of it. Do you have any ideas as to where I might buy these?
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Post by paulg100 on Sept 18, 2015 12:03:38 GMT
do you have the motors for this already?
I was close to going with a DC build and tbh once you start adding up the costs inc High amp PSU's there wasnt an awful lot of difference in cost compared to AC route, at least for a 6 dof.
24v high amp psu's are going to be big $$$$
Maybe car batteries will be the way to go or i think you can link 12v psu's.
second hand 12v server HP psu's will get you to about 80amps, IBM do some blade server ones that pop up that are way over 100 amps like 160 amps, but only 12v i think. There are hacks to combine 12v's psu;s together but not sure how safe that is.
i did get a quote from alibaba for some 24v psus some time back and they came in about $100 plus shipping, duty and taxes. That was less than 100amps though.
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Post by clyevo on Sept 21, 2015 0:29:44 GMT
I wonder if MIG welding machine can give continuous output at that amps, cause that the easiest to find at any hardware store, probably need some modifications though. Edit : such as this, it is rated 60% duty cycle at 630amps and 100% duty cycle at 400amps, 630amps welding machine
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Post by clyevo on Sept 21, 2015 1:30:28 GMT
come to think of it why is your dc gearmotor at 24v x 106 amps = 2.54kw, that is very high power draw, but can only produce 236nm at 14rpm?? I am not sure about dc motor but i know my ac motor 1.5kw with 60:1 produce 417nm at 23rpm at power draw of 1.5kw. and dc motor that high power is sure to be expensive and the power supply also expensive, maybe you should consider other options. I think ac motor with inverter can achieve as good response and yet better power/cost compare to dc motor with DIY servo control. But take that with a grain of salt; it is your choice.
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Post by tronicgr on Sept 21, 2015 3:02:38 GMT
I agree. Power consumption of DC motors gets ridiculous near stall state. Check the stall currents on AC motors from any datasheet for comparison. And the VFD inverters are considered energy efficient compared to using step down (PSU 120v-220v down to 24v or 12v ) ; just the losses from that conversion...
Thanos
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Post by 5natural5 on Sept 23, 2015 12:16:20 GMT
Thanks for your thoughts guys! I really appreciate it and I am going to rethink/recalculate my plans! I'll post back with an update as soon as possible.
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Post by tronicgr on Sept 23, 2015 14:13:52 GMT
Thanks for your thoughts guys! I really appreciate it and I am going to rethink/recalculate my plans! I'll post back with an update as soon as possible. If you don't want to deal with the higher voltages required for AC motors and VFD inverters, there is an alternative to use DC powered servomotors (75v): CPM-MCVC-3421S-RLN $299 each www.teknic.com/model-info/CPM-MCVC-3421S-RLN/GR34 Gearboxes Ratio 30:1 $395 each base on 6 Items Please find the link on www.motiontek.ca/pdf/GR-3410H.pdfSeiman Najib Global Motion Technology Inc T (416) 731-8187 F (647) 317-1183 Email sales@motiontek.ca www.motiontek.caWith 1:30 reduction, and 1400rpm in full speed of the motors, you will have 43rpm output All six motors will be powered by two 10amp power supplies than can be found in the teknic site. This solution is already being used, check the last video here: motionsim.blogspot.com/2015/08/bigger-better-stronger-6dof-platforms.html?m=1These servomotors have integrated motor driver, so no need for sabertooth to drive them! Connect them directly to the Amc1280usb with PWM mode. Thanks Thanos
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