Recent Progress

Motor Control

  • 11/7/14 Selecting a FET for the Commutation Driver
    The main concern with using a FET for the high-low configuration required for the brushless commutation is the gate capacitance of the transistor.  In order to limit this, one of the primary specs that we looked at when choosing a FET was the total gate charge QT.  Another key attribute of FETs are their RDS(on) value, which is a key component for the power consumption the transistor utilizes.  After a few weeks of research,  we came to the conclusion that the IRLB8748PbF transistor would be best sutied for our application.  Here are the key specs for that transistor:
    RDS max=4.8 m
    VDS max=30 V
    ID max= 44 A
    QG max= 23nC

  • 10/27/14 Choosing A BLDC Motor Controller
    After about over a week worth of research, team OBSCENE came to the conclusion that the BLDC motor controller we will be using is the Allegra A4690.  The T4690 is a sensorless communtation pre-driver with is controlled via a SPI bus and a inputted PWM signal.  The motor controller also outputs a rotational speed sensing signal that allows feedback into an external MCU that will be used for direct communication between the motor control configuration and the CPU.
  • 10/16/14 Decision On A Motor And Configuration
    After some research and premilinary testing of in-house built trusters, Nick Schmidt came to the conclusion that we will have to purchase new motors for our system moving forward.  Through research into thrusters that could generate enough thrust with optimal cost and size, Team OBSCENE came to the conclusion that the T100 by blue robics(URL below) would be ideal for the ASV boat design.  The T100 thrusters provide about 5.2 lbf forward thrust while operating at 130 watts and only weigh 0.65 lbs in air.  The main benefit of using the T100 thrusters versus other thrusters of equal magnitude is the cost.  Each individual T100 thruster cost $109, while some competitors prices are $800 and higher.  Also using these small and lightweight motors would allow for the ASV to utilize a four motor square configuration where each motor is set at a 45 degree angle allowing for the vehicle to travel in any 2D direction.  However, the T100 are brushless motors, which means they have a three phase configuration that requires precise timing and accuracy.  Instead of design an entire control system for each individual phase, we decided to research prebuilt BLDC motor control systems that would save our team hundreds of hours of work for a minimal cost.

    T100 Link:

RC Controller

  • 10/28/14 Setting Up The RC Signal
    Team OBSCENE has been working on an RC to serial converter to be able to control the boat from a remote location, at this moment the team is able to read in the RC signals through the receiver to an Atmega168, and then output the pulse widths to a terminal window over a TTL serial to an RS-232 serial using a MAX3232.


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Image Processing

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Central Processing Unit

  • 10/09/2014 Installing the OS
    Using the inherited I7 processor, and the x86 mini-ITX motherboard, Team OBSCENE installed UBUNTU 14.10 for the CPU operating system.