Darathian
Resolved by Dunning-Kruger!
Since I know some of you have used the Sabertooth and Kangaroo I figured I would ask opinions.
I have decided on the Parralax Arlo base for my next robot chassis. I will use the caster's from parralax.
I will most likely be using the Sabertooth and kangaroo combination for motor controller/PID but I am not decided on this and open to suggestions.
I also find myself in a heated mental debate between the wheel/motor combination from parralax or the Zagros Rex motors and wheels combined with the Sabertooth/Kangaroo.
Item 1:
One of the key items for me is how well the encoders between the two different motor/wheel sets works with the Sabertooth and kangaroo.
Item 2:
The other item floating in my mind is the ground clearance between the two motor/wheel sets. It seems at least to me that the Zagros wheels would provide more ground clearing but since the base plate of the chassis provides stability to the base platform I am not really sure if using the Zagros motors are feasible.
Item 3:
Since I am going to build a body, arms and head on top of the base the torque and weight carrying ability is important.
Item 4:
I need to be able to control both the position and speed of the motors at the same time. For example example I should be able to have to robot move lets say 1 feet at a certain speed.
I know this is kind of an open ended questions but if anyone have used any of these wheel/motor combinations please provide your 2 cents as it relates to the items listed above.
I appreciate any comments or insights you guys can provide.
I have no experience with the Rex motors. The robot base I have is the Max 99 with the 25rpm basic motors.... However a few guys on here have said positive things about the Rex motors, especially about the high resolution encoders...
I'm using the Rex motor with the high resolution encoder to turn the waist on my B9. The motor is strong, smooth and quiet. The encoder is amazingly precise and the Kangaroo X2 matches with is nicely when it's set to Independent Mode. This is how I'm running it as it's controlling two different motors speeds and position. However Tony (Toymaker) has had trouble using these encoders when Kangaroo is set to Mixed Mode. That's the mode needed when turning two motors at the same time like on a wheeled base like you want to do. Because of the super high resolution of the encoder the Kangaroo would only run the motors at half speed. Tony was working with Dimension Engineering to resolve this issue but I don't know if they did. You could try to contact DE's support or Tony and find out. Other then that I would highly recommend the Rex motor/encoder combo.
EDIT: Also the rex motor comes in two speeds. The slower one has more torque but I got the faster one and it has plenty of power for my needs.
Hope this helps.
Thank you for everyone's input. I will contact DE or Tony and go from there.
@Darathian, The Kangaroo/Sabertooth combo is an excellent PID motor controller, look at my earlier posts on this where I show coding the Kangaroo from EZ-Script it covers pretty much all you need to know about fully controlling motors and analysing feedback from the encoders etc.
The problem I have had with the Kangaroo is that it cannot use the high resolution encoders (of the type I use) in mixed mode (dual motor locomotion), I am having to design a circuit that divides the encoders outputs to get it all to work. With a single motor with high res encoder (independent mode) you should be ok, its just when the Kangaroo has to deal with 2 motors simultaneously it cannot keep up with the counts.
The Kangaroo max pulse input is 80000 for one motor, meaning that its 40000 for two motors and in mixed mode it has to read two encoders simultaneously. So the fix is a divide by two (say 4013 D type flip flop) circuit, this reduces the 63500 pulses (per motor per revolution) down to 31750, the loss in accuracy is negligible. Dave's faster (less torque) motors have lower pulse counts so may well be ok without this mod, but I am driving a 4 foot robot around on these motors so I need the extra torque.
Let me know if you need any more help.
Tony
Whats this about the "indoor navigation system" that DJ is working on?
Sounds interesting and exciting too
@mgodsell1973... You know as much as we do about it... We're all going to have to wait until DJ releases it and/or chooses to tell us more about it...
@Toymaker
Do you have any idea what would be a good substitute encoder that should work the best with the Kangaroo?
I ask because I know nothing about them and I, as I'm sure many others here value your opinion.
Herr Ball
@Herr Ball, In my opinion the encoders on the REX motors (HEDS-5545) are the best and already fitted, its just the problem with the MR300 motors that they have 63500 pulses per revolution and the Kangaroo can only handle 40000 in mixed mode (2 motor drive locomotion). The divide by two circuit on each encoder line fixes this by reducing the pulse count down to 31750 so the motors are now within the Kangaroo specification.
Tony