Rover Subsystem - Texas Tech 2/16/96 Progress Report

From: Richard Eddings

 Past Deliverables:
                Complete a short list of materials
                Complete frame design
                Price & determine availability of material
For the material selection, the rover was broken into four separate subsystems: Wheels, legs, Body structure and electronics enclosure. The material choices are as follows:

Subsystem Density Yield Strength Thermal Conductivity
(gm/cm3) (Mpa) (W/m k)
Cast Aluminum Alloy 355.0 TS 2.71 172 180
Wrought Aluminum Alloy 7075 2.8 503 180
Body Structure
Thermoplastic Carbon Nylon 6/6 (30% fiber) 1.37 241 N/A
Thermoset Graphite Epoxy (48% fiber) 1.48 140 N/A
Electronics Enclosure
Thermoplastic Glass PPS (30% fiber) 1.56 138 N/A
Thermoplastic Carbon PPS (30% fiber) 1.56 186 N/A

Also, preliminary drawings were made on the structure and electronics enclosure.

       Continue thermal revisions
       Begin preparations for construction
       Assist in structural revisions

The thermal revisions are now 1 week behind schedule, but should be completed on 
schedule.  The drive motors and steering motors for the prototype are ready to be 
ordered, pending availability of funds.  

       Complete communications system design
       Complete research on obstacle detection
       Complete block diagram of sensor system
Camera information has not been received. Preliminary selections have been made for the communications system. Currently, the light stripping detection system from used by the JPL Pathfinder rover is what we are considering for obstacle detection.

This afternoon after I talked with Mark, I talked to Motorola and they said that they would not be able to increase the data rate on the radio modem. I had been looking at that and saw that it would require a complete rework of the modems design (i.e. the bandwidth would have to be changed on the radio and the logic board would have to be faster). I then called JPL and dicussed the matter with them and they said that they were limited to that data rate because of the mission specs. I then found some info on the Deep Space Network (DSN) and found that it is not set up to handle large bandwidths, like that of a video signal.

So, as for the design of the comm. system on the rover. I will design it around the Motorola Radio Packet Modem using it as the means by which images are transmitted. As the design continues a video transmitter can easily be added to the system if power and mass allow. I have choosen to do it this way for now because the obstacle detection system is going to require a great deal of time to design. However, I do feel that having a video transmitter would be a really big plus but until more details are known about the lander earth link this design will allow us to complete the mission.


      Complete listing of possible computers
      Complete power calculations

A short list of CPU possibilities has been constructed.  A preliminary 
power mode chart has been started.  It will outline the power requirements
for various modes of operation. 

Next: Future Deliverables:

       Continue thermal revisions
       Continue preparations for construction
       Begin ordering of prototype parts

       Complete stress calculations
       Order material for prototype
       Compose a weight list for all components

       Complete block diagram of sensor system
       Begin detailed design of sensor system

       Complete operational modes requirements
       Complete power flow diagrams

Mass: 7 kg
Power: 30 W