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Using high-power thruster on current system


(chengchang) #1

I want to do some hardware upgrades based on the current control system of BlueROV2.

One thing that i want to try is to use a high-power thruster.

The thruster i want to introduce is the TECNADYNE MODEL 560 DC BRUSHLESS THRUSTER.
Datasheet link: http://tecnadyne.com/wp-content/uploads/2017/06/Model-560-Brochure-1.pdf

In order to use the 560 Thruster, the ESC might needs to be replaced, in fact, i am not sure if there are such kind of ESCs in the market can support the 560 thruster.

To bring my plan into real, I need to collect some advises and ideas about the possibilities of my plan.

Thanks.


(Jacob) #2

Hi, It looks that these models include an ESC inside of the motor housing.

The obstacles I see with using these on the BlueROV2 are:

  1. Mounting them, and making them fit on the ROV
  2. Supplying power to them, you will need to upgrade the power supply and conductors
  3. The control signal - these use a +/- 5V analog control signal, the autopilot on the ROV can only output digital pwm control signals. You will need to find a way to translate these.

-Jacob


(chengchang) #3

Hi Jacob,

           Thanks for your reply. 
     
           I did some researches, it is possible to convert PWM digital signal to analog signal. 

           But i do not know what is the shape of the PWM signal that outputs from Pixhawk,  i will need this information  to determine if i can convert it to a +/- 5V analog control signal. 

           If you can provide some sources that will be helpful. 

Thanks again.


(Jacob) #4

Hello, the autopilot can produce two different kinds of PWM signals:

  1. An RC-style pwm signal with user-selectable frequency. The pulse widths range between 1100 and 1900 microseconds with 1500 microseconds being neutral (stopped), 1100 microseconds is full reverse and 1900 microseconds is full forward.
  2. A duty cycle with user-selectable frequency where 50% duty is neutral (stopped), 0% duty is full reverse and 100% duty is full forward.

(Etienne Demers) #5

Sounds like they are using a MC33033 BLDC motor controller IC or equivalent.

I’d need to see the schematics to be sure but this is good news. There will be a series of op-amps to process the control signal. Basically one set will detect the polarity and tell the controller if the bldc needs to turn CW or CCW and the other set will be to use 0-5vdc to control the speed or reverse the polarity if the control signal goes in negative.

You can use duty cycle hooked on resistor and capacitor to produce an average dc voltage.

Check this link: http://www.instructables.com/id/Analog-Output-Convert-PWM-to-Voltage/

In this case 50% duty cycle would be 2.5vdc since I’m guessing it’s running pwm off the 5vdc supply.

To be sure just measure the voltage when there are no commands.

Then all you need is to connect an op amp to offset the volts and amplify it.

Check this link: http://www.edaboard.com/thread348693.html?styleid=13

Since it’s going to high impedance input, you won’t need to drive the signal.

Should cost you less than 10 USD for all your thrusters but you’ll need to do some soldering. You might find some ready made bits for Arduino if you look around this is very common pracrice.