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Post by tronicgr on Aug 27, 2014 23:19:15 GMT
Will place info here
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Post by Trip Rodriguez on Sept 9, 2014 23:48:44 GMT
Thanos, on the X-sim forums I was advised against using DC motors (but I don't know why) so as you know I've more or less decided to buy three (eventually four) Teknic CPM-MCVC-3441S-RLN for my project. The down side of this is the cost, three of these with wiring harnesses and shipping will cost almost $1,500 for just the motors. Even worse I really want four instead of three so I can add yaw. I'm ok with going forward with this but the DC motor option caught my attention once more and I want to ask some questions before I invest in the expensive servo motors. Tino's post is the one that caught my eye. I can buy the 180W version of these motors www.aliexpress.com/item/Golf-Trolley-Motor-dc-motor-with-carbon-brush-with-CE-12VDC-150W-ratio-26-1/293841828.html (Tino plans to use these) , and the H-bridges you suggested to Tino for them www.pololu.com/product/758 including shipping for about $150 per motor. This makes three of these $450 vs. $1,500 for the servo motors. For $600 I can get four of them for 4DOF! In addition to this I know I'll need to add $100 to my Thanos board order. Do I need some kind of Arduino as well or just your boards? Also this option gets me worm drives so the motors don't really have to do any work to simply hold the platform still. The platform I'm building is a slightly modified version of the Built For Fun "Mini Motion Platform 3" design . I will be using a 7.2:1 chain drive reduction if I buy the Teknic servo motors, or a 1.3:1 chain drive reduction if I use these DC motors. According to my very rough calculations final torque and speed will be very similar between the servo motors and the golf car motors with those external ratios. I'm planning to add yaw to this setup by articulating the "yaw constraint link" at the rear of the platform with a fourth motor. This seems like a pretty tempting option, what do you think? What are the disadvantages of going with DC motors? I have the power supplies covered so we can ignore that part. My one remaining concern is the accuracy of the specs on these DC motors. They list the 150W and 180W versions of this motor as having exactly the same specs! Clearly that can't be accurate so it leaves me wondering how inaccurate the specs might be!
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Post by Trip Rodriguez on Sept 10, 2014 8:30:34 GMT
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Post by tronicgr on Sept 10, 2014 17:47:59 GMT
They are cheap themselves, yes, but to power them and have decent performance... It might cost you more than VFD inverters. Lots of Amps involved and regenerative voltages, that you will need expensive DC drives and Car Batteries in parallel to the power supply to absorb excessive current... Why do you think the Clearpath power supply alone costs $200? E3PS12-75 Output: 75 VDC, 3A cont., 12A peak Weight, lbs (kg): 12.4 (5.6)
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Post by Trip Rodriguez on Sept 10, 2014 20:26:00 GMT
Thanks Thanos. The DC drives you mention are in addition to the H-bridges I guess? Sounds like I'll stick with the ClearPath option =) The rig is coming along, I posted it in the projects section =)
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Post by Trip Rodriguez on Sept 10, 2014 20:46:29 GMT
Thanos should I take a good look at the AC motor option before I order the ClearPath servos? It seems like AC motors will give more power and would be much better if I want to upgrade to a 6DOF later. How much do you think it would cost me total with everything included to use AC motors vs. ClearPath?
I dismissed AC motors initially because of the cost but now that I'm planning to spend much more than my original plans I figure I should check before I buy. The section on inverters makes this look complicated. That scares me off a bit, ClearPath sounds much easier.
After this I probably won't have many questions for a while so you should get a break for a bit =) Sorry I've been asking so many.
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Post by tronicgr on Sept 10, 2014 21:51:09 GMT
Thanks Thanos. The DC drives you mention are in addition to the H-bridges I guess? Sounds like I'll stick with the ClearPath option =) The rig is coming along, I posted it in the projects section =) The DC drive is the same a h-bridge. They called drives as they are a little more inteligent than just a bunch of mosfets that you have to switch on-off your self. The Pololu drive for example, uses a chip do handle the timings for on off of the PWM: www.pololu.com/product/758Another example of motor driver is the Sabertooth, that its chip can accept RC servo signals, PWM and Analog signals for direction and speed: www.dimensionengineering.com/products/sabertooth2x25The clearPath motors, are not simple DC motors... they are BLDC motors (3phase) with integrated servo driver that is far more intelligent that all DC motor drives and VFD inverters.
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Post by tronicgr on Sept 10, 2014 22:03:13 GMT
Thanos should I take a good look at the AC motor option before I order the ClearPath servos? It seems like AC motors will give more power and would be much better if I want to upgrade to a 6DOF later. How much do you think it would cost me total with everything included to use AC motors vs. ClearPath? I dismissed AC motors initially because of the cost but now that I'm planning to spend much more than my original plans I figure I should check before I buy. The section on inverters makes this look complicated. That scares me off a bit, ClearPath sounds much easier. After this I probably won't have many questions for a while so you should get a break for a bit =) Sorry I've been asking so many. One big difference between VFD inverters and the Clearpath motors is how easy is to parameter the motor. -Most VFD inverters need manual input from their panel, or some via RS485 to computer GUI software. -Clearpath motors have a USB interface on them that allows to perform any parameters on the motor, even when its enabled and running (even override test the motor from the GUI software). The parameters are in human language and easy to understand what they mean. -You will need 220v power for the VFD inverters -110v are enough for the power supply of the clearpath motors. -AC motors do not have brake, when you issue stop command, they may keep rotating during inertia, if the gearbox allows free wheeling. (Maybe will need external DC brake system installed) -Clearpath motors, handle the actual speed accurately during the internal encoder tracking system. This means if you issue a stop command IT WILL stop and MAINTAIN its position (switches the motor control to position hold automatically!) I can point out many other differences, Its just different technology. About the cost of each solution, I'm not sure which one would be better. They are both close regarding the cost. Thanos
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Post by carbon on Jan 20, 2016 7:18:54 GMT
Unfortunately decent AC motors/gearboxes and VFDs are not cheap in Australia - would have cost me way more then what I have seen quoted on this site. So I built a 6DOF with 12V DC motors as shown here link ($100 each) Although what turned up was rated at 48amps and measured at 5400rpm - I used Led power supplies - not that expensive ($70 each) and they work great. What is although the weak point of most of these low cost motors/gearbox setups is the standard worm gear. So I purchase the motor without a gearbox and just connected it to a Ball screw ($80 each). Ball screws have a high efficiency of around 90% compared to your average worm gear - around 50%. As long as you don't want to lift something too heavy the setup works great. My motors don't even get warm in operation, although I did modify them to add some convection cooling.
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Post by tronicgr on Jan 20, 2016 11:29:48 GMT
Unfortunately decent AC motors/gearboxes and VFDs are not cheap in Australia - would have cost me way more then what I have seen quoted on this site. So I built a 6DOF with 12V DC motors as shown here link ($100 each) Although what turned up was rated at 48amps and measured at 5400rpm - I used Led power supplies - not that expensive ($70 each) and they work great. What is although the weak point of most of these low cost motors/gearbox setups is the standard worm gear. So I purchase the motor without a gearbox and just connected it to a Ball screw ($80 each). Ball screws have a high efficiency of around 90% compared to your average worm gear - around 50%. As long as you don't want to lift something too heavy the setup works great. My motors don't even get warm in operation, although I did modify them to add some convection cooling. The hardest part using ball screw is that is not easy to find such parts in a way to easy fit them all together (not without too much modification). Your solution is great! I would love to see your project presented here in the user area with a little more details. Perhaps it will help others as well that do not want to go with such heavy duty solution like the VFDs with AC motors! Thanks Thanos
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Post by carbon on Jan 22, 2016 4:37:22 GMT
Unfortunately decent AC motors/gearboxes and VFDs are not cheap in Australia - would have cost me way more then what I have seen quoted on this site. So I built a 6DOF with 12V DC motors as shown here link ($100 each) Although what turned up was rated at 48amps and measured at 5400rpm - I used Led power supplies - not that expensive ($70 each) and they work great. What is although the weak point of most of these low cost motors/gearbox setups is the standard worm gear. So I purchase the motor without a gearbox and just connected it to a Ball screw ($80 each). Ball screws have a high efficiency of around 90% compared to your average worm gear - around 50%. As long as you don't want to lift something too heavy the setup works great. My motors don't even get warm in operation, although I did modify them to add some convection cooling. The hardest part using ball screw is that is not easy to find such parts in a way to easy fit them all together (not without too much modification). Your solution is great! I would love to see your project presented here in the user area with a little more details. Perhaps it will help others as well that do not want to go with such heavy duty solution like the VFDs with AC motors! Thanks Thanos From looking at the projects on this site it seems that AC motors are very much in the Majority, they cost more, but are simpler to put together with off the shelf parts than building your own gearbox, which is what you're doing with a DIY ballscrew actuator. Obviously only for someone really looking for a challenge like myself . Note the majority of the parts on my actuators are hand made with carbon fibre. Details of my build are available on-line, so I will leave it at that.
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Post by GA-Dawg on Feb 20, 2016 21:26:18 GMT
Carbon,
Really like your build. For someone like me I might have attempted it but I am not sure on the dimensions. It was my understanding (I am a novice so pardon my ignorance) that you need to know the angles to properly configure the system. Or is there another way. Please advise.
Thanks in advance -GA Dawg
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