Sub and System Requirements

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By Chau To and Elaine Doan

Design:

  1. To maximize the speed of the Hexapod in order to match Rover speed at 0.2002 m/s:
    1. The weight and the size of Hexapod will be determined using Solid works model and stress test simulation will be performed. https://www.arxterra.com/how-to-perform-a-stress-test/
  1. The length of Femur and Tibia of the leg will be calculated to maximize the ideal step size of the Hexapod, which is 4 inches.( Ideally, Hexapod will take 2 steps in 1 sec and in order to match 0.2002m/s or 7.8in/s, each step needs to be 4 inches).
  2. A prototype will be built to verify that the model can match the speed with Rover.

Servos:

  1. In order to maneuver over obstacles and travel in the forest like settings, Hexapod will require 3 servos for each leg. Eighteen servos will be needed for 6 legs of the Hexapod. Servo type is https://www.arxterra.com/current-draw/.
    1. Based on the weight and size of the design, the torque will be calculated for the Hexapod speed and determine servo type. https://www.arxterra.com/current-draw/
    2. Verification of servo study is here: https://www.arxterra.com/a-better-servo-powerhd-1501mg-analysis/.
  2. To observe the environment via Android phone’s camera, one servo controlling the phone holder will be used, which help the user to scan the area with the Android phone mounted onto Hexapod.
    1. The angle sweep for the phone “turn-servo” is ( https://www.arxterra.com/current-draw/). The phone holder prototype will be built and test to verify the total view from the Android phone’s camera.

Microcontroller and Servo Controller:

  1. For the communication between microcontroller and the Arxterra Control Panel, the Hexapod will use the Arduino ADK microcontroller, which has a USB host interface to connect with an Android phone. ADK board will have more memory (Flash Memory, SRAM, EEROM) than the standard UNO to perform the complex programming for Hexapod movement such as racing with the Rover and maneuver through objects. ADK board also had enough digital output pins to support for 19 servos required for the Hexapod.
    1. Verify specs of the Arduino ADK at:  http://arduino.cc/en/Main/ArduinoBoardADK#.UyZ2EvldUz0

 Communication:

  1. The wireless control of the Hexapod is through using an Android phone app called ArxRobot.
    1. Verify the Android phone’s compatibility to the ArxRobot app by contacting Arxterra.

Link to Arxterra compatibility (https://www.arxterra.com/android-phone-complications-with-arxterra-robot-application/)

Power:

  1. The battery will be using is LiPo 5A pack.
    1. Trade-off study will be conducted to determine the type of battery and safety purposes.
    2. Maximum current test will be performed on one servo to determine the total power of the battery.
    3. 12 servos will need to be run simultaneously to verify that the battery can handle the performance of the Hexapod.

Current testing is available at https://www.arxterra.com/current-draw/.

  1. For safety purposes, Hexapod will use a voltage regulator to prevent damaging the Arduino ADK, and burning twenty servos. It will maintain 6V input as well as a steady current supply to the boards and servos. 
    1. Use oscilloscope and Multimeter to look at the output voltage and current of the voltage regulator in order to test and verify the stability output from the voltage regulator. Link to Voltage Regulator is here https://www.arxterra.com/voltage-regulator/.

Link to Mission Objective is here https://www.arxterra.com/mission-objective/