Hardware Overview

I have yet to explain exactly what our robot is attempting to accomplish. However, a quick synopsis is at the top of my blog. Let me divulge a more in-depth discussion of this information to my readers.

The robot is intended to be used as a military-operated vehicle that employs multiple sensors to detect potential bomb threats by collecting radiological and chemical data. Hundreds of men and women die every year in combat due to un-detected bombs and chemical exposure. The Bomb-Sniffing Robot is a proposed solution to this problem. This project’s goal is to save future men and women from dying preventable deaths in combat. As a result, the robot’s design targets military customers as well as civilian bomb squads.


As a side-note, look at this compelling data on the deaths from bombs within Bagdad, Iraq. The number of deaths just keeps rising (information found from http://news.bbc.co.uk/2/shared/spl/hi/in_depth/baghdad_navigator/). 

Now that I hopefully have your attention, lets go over our hardware. The figure below shows the overall hardware diagram. This figure describes the system as it pulls in data and transmits important sensor data.





















The basic operation goes as follows, a user wants to see if there is a bomb or other chemical hazards in an area, but this person does not want to get blown up--so use our Bomb-Sniffing Robot. The user can use the PlayStation controller (hooked up by USB) to control the on board camera's pan/tilt/zoom and robot's direction/speed. From that a GUI sends out the controller commands (via wi-fi) to the robot. Meanwhile, the robot is collecting all sensor data (camera, gps, LPG, propane, carbon monoxide, methane, and radiation). Then the robot transmits to the GUI the sensor information at a constant rate through the wi-fi connection.  The GUI allows the user to see the data in a convenient graphical and numerical format (via graphs).

I will later post an in-depth discussion on our beginning software overview between our two main submodules-- robot and GUI. There you can learn about what is going on in the background and what special features each has to offer. Note that our design is very unique, because you don't need a large amount of on-board memory on the robot, due to the constant transmission of data. Just enough to hold the data for awhile until another transmission can be made.

Potential design for track wheels

Yesterday I was looking @ Linxmotion.com . I found some good tracks (3" wide x 21 links ~ 23") for our robot (found here http://www.lynxmotion.com/c-94-tracks.aspx). I like the overall design of the chassis, but I want to make some personal modifications on the body. Linxmotion does sell the entire chassis kit (without electronics; found here-- http://www.lynxmotion.com/p-577-tri-track-chassis-kit-no-electronics.aspx) for a whopping $220.95. I would like to attempt to make my own version of the chassis in a metal shop.

The three potential modifications are as follows. First, our robot needs room for a camera to turn and motherboard's motor control wires need to have a quick line-of-sight to the cameras pan/tilt servo motor.
Second, I am considering placing two servo motors per track to multiply the speed for the wheels to turn. I am not sure if this is a good idea, but hey where is the fun in that... I'll eventually test this hypothesis (faster speed = more servos per track). Third, does our robot really need the triangle track-wheel shape? I need to consider other track shapes and placements for the servos. I'll attempt to post those trials.

The information below is how to construct the Linxmotion chassis without electronics (website can be found here: http://www.lynxmotion.com/images/html/build115.htm).

Tracked Vehicle Assembly Instructions Ver. 1.Updated 07/16/2008. Safety first! Wear eye protection and never touch a powered robot! Note: Do not use Loctite or thread locks on the assembly. They are not necessary and may cause damage to the Lexan.	Image of the chassis.
Step 1.Attach four 3" aluminum bars to the inside pair of lexan panels as shown. Use 4-40 x .375" hex screws.   8 x 4 x	Figure 1.
Step 2.Attach 1.5" hex standoffs to the lexan panels as shown. Use 4-40 x .375" screws.   12 x 12 x	Figure 2.
Step 3.Attach the motors as shown, using four 3mm x 8mm screws. Make sure the motor shafts and the hex standoffs are on the same side of the lexan panels.   4 x	Figure 3.
Step 4.Install the hubs onto the motor shafts as shown. Align the hub to be flush with the end of the motor shaft. Tighten the set screw down firmly.	Figure 4.
Step 5.Install the sprockets onto the hubs as shown. Take care to make the teeth on the sprockets line up as shown! Use two 4-40 x .625" screws per side.   4 x Sprocket Alignment:	Figure 5.
Step 6.Prepare the idler sprockets. Install the two sprocket halves back-to-back on the long end of the idler hub. Take care to make the teeth on the sprockets line up as shown! Attach them with two 3mm x 8mm screws. Make four idler sprocket assemblies.  Figure 6-1.	Figure 6-2.
Step 7.Attach ball bearings to the idler sprockets as directed in either Figure 7-1A or Figure 7-1B, depending on which version of the idler hub you have. Install the idler sprockets into the side panel as shown in Figure 7-2. Slide twelve nylon bushings over the nylon standoffs.   Figure 7-1A. Figure 7-1B.	Figure 7-2.
Step 8.Install the outer lexan panels as shown to close up the assemblies. Use twelve 4-40 x .375" screws.   12 x	Figure 8.
Step 9.Wrap the 21-segment track assembly around the sprockets, push the axel in and secure with two nylon snap rivet fasteners. These parts are included with the track kit, not the chassis kit.   2 x 4 x	Figure 9.
Step 10.You should now have two assemblies that look something like this.	Figure 10.
Step 11.Attach 1.5" hex standoffs to the bottom panel as shown. Use 4-40 x .375" screws.   6 x 6 x	Figure 11.
Step 12.Attach the top panel as shown. Use six 4-40 x .375" screws.   6 x	Figure 12.
Step 15.Attach the track assemblies to the chassis as shown. Use eight 4-40 x .375" screws.   8 x	Figure 15.
Step 16.You can install the optional base rotate using the top screws from the standoffs.	Figure 16.
Step 17.Push the capacitor legs through the holes in the motor terminals. Bend the capacitor legs down onto the terminals as shown.	Figure 17.
Step 18.Push the motor wire connectors onto the motor terminals. Make sure to put the red wires on (+) and the yellow wires on (-).	Figure 18.
Step 19.Install the wiring harness as shown. This switch will be for the 7.2vdc battery that powers the Sabertooth motor controller. Additional mounting holes allow adding separate power switches for accessories you add to the mobile platform, such as an arm, Johnny 5 torso, etc.	Figure 19.
Step 20.Refer to Table 19 for Sabertooth connection information. We've included the switch settings we used for Johnny 5 - you may need to use different settings for your application. You can find which direction to flip the switches on the card included with the Sabertooth. Route the motor wires through the holes in the chassis as shown! When the Sabertooth is properly connected and set up, use some double-sided foam tape to secure it inside the chassis.   Sabertooth Connections Sabertooth Switch Settings M1A Robot's right motor, red wire 1 Independent Control M1B Robot's right motor, yellow wire 2 Disable Exponential M2A Robot's left motor, red wire 3 Non-lithium mode M2B Robot's left motor, yellow wire 4 R/C Flip Mode B+ Battery (+), red wire 5 Enable Auto-Calibrate B- Battery (-), black wire 6 Disable Timeout Table 19	Figure 20.
Step 21. The Sabertooth has a battery elimination feature (BEC). This is useful when connecting the Sabertooth to an R/C receiver as it provides 5vdc at 500mA. This BEC can power the receiver itself and a couple of servos in low power applications, such as a pan-and-tilt. However, when more powerful servos are connected to the R/C receiver, you must disable the BEC and provide a separate battery to the R/C receiver and its servos. It is also necessary to disable the BEC if you are connecting the Sabertooth to an SSC-32.To disable the BEC, pull the red wire out of the black housings of the CH1 and CH2 wires as shown in Figure 21. Be sure to cover the exposed wire with heat shrink to prevent accidental short circuits!	Figure 21.
Step 22.This wiring harness is not included in the Tri-Track Chassis kit. We are illustrating what is necessary to install an SSC-32 to control an arm, Johnny 5 torso, or other servo-based addition. This switch will be used for a 6vdc battery.	Figure 22.
Step 23. If you are using both an SSC-32 and a Bot Board, you will install them as shown in Figure 23. If you are only using the SSC-32, you will secure it with the four screws and standoffs.	Figure 23.