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POST No. 2407432
Conveyor design
2019-06-03 03:56:06 JCarlos

Hi again!!


Well. We need a  robot on wheels capable of positioning quite accurately on the plane.


More important:

"Conveyor" design seems "easy", relatively simple,  and intuitive. it offers omnidirectional behaviour. Link


 However, any recomendation por very, very accurate positioning on the plane (indoor environments) ??


Now, we are trying to recreate the conveyor design. 


We already have 4 XM430-W350-R motors. We plan to use them for traction. Now we need 4 motors for direction.  We are studying which motors to acquire for the direction. 


Our first idea is to avoid the use of external gears. Therefore, we depend on the precision that the motor gives us. So we need very precise motors and with enough force to guide the wheels.


Our budget is 300$ approx for each motor:


I am considering the next options:


1) 4 XM430-W350-R 

2) 4 XH430-W350-R (more reliable but slower and less torque... a problem??)

3) Another option??


Any recommendation or suggestion or help??


JC


PS: does that "conveyor design"  get other names? The only reference for this design we have found is the -Robotis design-.

2019-06-03 03:56:06
JCarlos
2019-07-12 10:16:18 Will Son

Hi,


If you are directly controlling DYNAMIXEL from your PC/Laptop via U2D2, U2D2Power hub could be a good solution.

Please be aware of total current limit 10A of the U2D2 PHB, and if your application requires higher current consumption, please consider to directly supplying power to each DYNAMIXEL from power source rather than passing through U2D2 PHB.


1. Connecting multiple Li-Po batteries are not recommended as there can be voltage differences. If you need more capacity, it would be better to use bigger battery with compatible charger. Please consult with an expert when selecting power source.


2. If you are running all 8 XM430-W350-R at the same time, I'd recommend to have at least 15A peak current supply. Discharge rate of one LB-012 battery is 5C which is (1800mA x 5 = 9000mA)


3. U2D2 is also used in controlling adult size Humanoid THORMANG3. You'll be able to control 8 DYNAMIXELs without a problem.


4. Cables are assembled through a hollow back case so that harnessing would not disturb mechanical design.


5. LB-012 power connector is not compatible with U2D2. LB-012 is designed for OpenCR controller for OP3 and TurtleBot3. If you need to use the LB-012, you'll need to customize the connector.


6. Although eManual image shows an example of connecting multiple power source,  plugging the barrel jack into the DC port will disconnect other power sources for protection. However, it is not still recommended to plug in multiple power sources.


Thank you.

2019-07-12 10:16:18
willson
2019-06-04 09:36:33 Will Son

Hi,


Any types of locomotion inevitably introduces some error in position during the motion due to friction and slip.

In order to overcome this error and achieve very accurate positioning, you'll need to have a very accurate sensor that can measure and compensate the difference between desired pose and present pose(position + direction).


You might want to select DYNAMIXEL depending on the weight of the system, but if it were me, I'd probably try with the XM430 first to avoid possible failure due to the lack of torque.

However, please note that XM430 and XH430 have the exact same Axial / Radial Loads spec.


The best solution will be using PRO+ H42(600k+ resolution, 5.1Nm torque, 280N radial load), but I understand this won't be feasible with a limited budget.


The "conveyor" is borrowed from conveyor belt that delivers items, and the "conveyor robot" is not a general terminology.

Thank you.

2019-06-04 09:36:33
willson
2019-06-09 04:17:20 Jose Carlos

Thank you, willson, for your informative answer (again). 


We use a solution based on ultrasound for -indoor "GPS"- (marvelmind robotics).  We hope to achieve accurate positioning in real-time.


We have started the construction of a first module for a wheel (1 direction motor + 1 traction motor). We have 4 XM430, and so, we can "test" (partially at least) the performance. That should help us make a decision.


I hope to keep you informed by this thread within two weeks.


Thanks!!


JC

2019-06-09 04:17:20
JCarlos
2019-06-10 13:34:09 Will Son

Hi Carlos,


Thank you for the update.

Just in case if you don't want to expose details about your application, you can also inquire to support@robotis.com.

2019-06-10 13:34:09
willson
2019-07-01 23:02:35 Jose Carlos

Hi again!


Well. The tests with XM430-W350-R seem satisfactory. 

For our new platform, We are considering to buy:


4 XM430-W350-R 

1 U2D2 Power Hub Board

2 LIPO Battery 11.1V 1800mAh LB-012


Questions: 

1. Can two (or more) batteries be connected to the U2D2 Power Hub Board for greater autonomy (and reduce the number of recharge cycles)? How?

2. How many batteries is recommended to use to power 8 motors at the same time?  We will have 4 LIPO Battery 11.1V 1800mAh LB-012

3. A u2D2 unit can control (from a laptop) without problems (latency,...) 8 XM430-W350-R. Correct?

4. In the conveyor video (https://www.youtube.com/watch?v=uv2faO7GhXc) we are unable to see the cables. Where is the trick? 8-O


Thanks in advance!

JC
2019-07-01 23:02:35
JCarlos
2019-07-11 03:41:56 Jose Carlos

Hi again! 


More questions:


1. Could you confirm me that the LIPO Battery 11.1V 1800mAh LB-012 is compatible with the U2D2 Power Hub Board? I think so but...

2. We are concerned with the "Danger" warning in U2D2 Power Hub Board page (Robotis Manual):

        DANGER : Do NOT use both power inputs at the same time. Select ONLY one of the power source to connect. 


It seems too easy to connect (accidentally) two power connectors at same time. SMPS and batteries for example.  Why is there no selector that forces the connection of a single power source ? Besides, does not the image mislead (Robotis manual) ? We are confused...


Thanks in advance!

JCarlos

 







2019-07-11 03:41:56
JCarlos
2019-07-12 18:30:14 Jose Carlos

Thank you for your clear answers, willson!


I think that i have found the correct cable for battery.  An additional advantage of this solution is that it is impossible to connect batteries and SMPS simultaneously because there is only one barrel connector in U2D2 PHB. :-) And it is cheap!


JC 

2019-07-12 18:30:14
JCarlos
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