I am working on an ROV project and looking at the M200 thrusters. My objective is to leverage some of the hardware and software I use for robotics and use them to build an ROV with your M200’s.
I use NI Labview, MyRio and a control system designed for First Tech FRC robotics competitions found here, http://www.ctr-electronics.com/control-system.html?p=1. My sensors wouldn’t be useful for an ROV but LabView, MyRio and the PDP, modules and Talon SRX speed controllers with the M200’s (quantity 6) may work for me. Any advice would be greatly appreciated. Thank you - Steven
A motor is a motor is a motor. I don’t know if the M200’s are going to supply the high torque that you might be looking for. In my opinion, this are more of a high RPM motor than high torque. The other thing is there is no positional feedback with them. Do you plan on using your own encoder system?
I program with LabVIEW also but haven’t done much along the lines of robotic control for a while. I deal mainly with test equipment and doing editor / librarian functions and controlling test equipment / executing / data logging test.
My first question would be, how do you plan on using the motors, what type of feedback system are you planning on using etc.?
The Talon SRX speed controllers are for brushed motors only, but the T200/M200 are brushless. I would recommend using a brushless speed controllers (like the BR Basic ESC or BlueESC) and then sending the appropriate PWM control signals from your electronics. You can probably find servo control libraries that would make that very easy.
The MyRIO device has three PWM output lines with a maximum frequency of 100 kHz. More than enough to create the PWM signals for the ESC’s using a simple VI to drive it with. LabVIEW is really simple stupid when you have to generate signals like that. Works great!
The problem will be the amount of available PWM signals. Since the device is ran off of a USB interface, you can just tag team a couple of them.
There are two blocks of 8 bit DIO for the MXP ports and one byte available on the MSP port. The issue that might exist is the voltage output level is 3.3 volts. The other thing that I don’t care for with a lot of National Instruments DAQ style boards that are the cheaper ones … they can’t drive anything worth a crap off of the ports. The good thing is the ESC’s can accept 3.3V signals and it is at least worth a try. Worse case scenario would be to have to put a line driver buffer in line with the signal to make sure it can supply enough rear to do the job.
From what I can tell in the documentation you have three PWM lines between the MXP ports and two on the MSP port. The one thing I see is the PWM lines between the two different ports have the same name … so I get the feeling it is only assigned to the secondary I/O function of a PWM port once for each signal name.
You should be able to setup a timer routine to use a regular DIO line to toggle on and off to create a PWM signal … considering how slow of an update rate you are dealing with. The “speed” control would basically feed the timer which is going to toggle the signal. Pretty simple to do.
The other thing is … this unit has an FPGA that is doing the I/O so I am not sure exactly how the software will function with this. From the little bit that I have been readings on ni.com … this thing is a school based learning system and frankly not much more than a fancy toy. Life would be better with a real DAQ and using LabVIEW to run your code.
Thank you for your comments. I’m a high school junior and trying to use some of the control systems available to us in robotics competitions. While MyRio/RoboRio is an educational device it has been used to build some sophisticated robots and rov’s at the high school & collegiate competition level. However, what Rusty pointed out is that bluerobotics thrusters are brushless and all of our current motor controllers are for DC brushed motors. I’m thinking that to use the bluewater thrusters with the MyRio platform I could start researching servo based control to power the thrusters. From the FPGA I should be able to output the correct PWM signal. I’m going to test it with some spare ESC and brushless motors.
On my SeaPerch I keep working on potting the motors with electrical tape and wax - brushless would be nice!
I really appreciated everyone’s advice and I’ll update the post once I work through some testing.