PSU ME CRAWLER
PROJECT




 
Ryan
Irwin
  
Jake
Brandspigel
  
Chris
Colasanti
  
Robert
Mulfinger
  
Scott
Holand
  
Students in ME 462 often create electro-mechanical vehicles for their final project. Often times, they spend most of the time trying to create the mechanical aspects, and do not concentrate enough on the more interesting control aspects of the project. The professors of this course would like students to use an already made platform to perform some more interesting tasks with using the tools they developed in the course. Our main objective is to deliver an electro-mechanical rover to the PSU ME Department.
   
Original
Rover

This is a picture of the original Tracked Rover. The reasons that it will not be used are:

--It can not climb stairs
Since the center of gravity is not low enough, the rover tips backwards when attempting to climb over anything.

--The Track is bulky
The track was too large and heavy and that it took a lot of power to run.

--Battery accessibility
The Entire Rover has to be taken apart to access the Battery. The terminal block that it is connected to is very difficult to connect any charger to. So when the Battery is drained the rover has to be dismantled

--Poor Mounting Surface
The rover has a very limited space for mounting any components. The space may be only wide enough for two components.




Original Rover

Deliverables

-Robust electro-mechanical crawler platform

Robust: This rover must last for at least 5 years
Flexible Compatibility: End user can interface the system with a Basic Stamp, HC11, or other microprocessor
Moderate Terrain: It must be able to handle outdoor terrain such as grass/dirt, gravel, curbs, etc.
Moderate Conditions: It must be able to drive over light snow and damp conditions
Minimum 30 minute run time: Our goal is to reach an hour.

-Manual: All parts information, Building Instructions, User's Guide

The manual will include a comprehensive parts information list, which will be used for spare and replacement parts. Along with the purchased parts information there will be schematics with material and dimension information as well as a cost breakdown. The purpose of this is to allow other universities to duplicate our crawler if desired. Also, in order for students to understand the operation and control of the vehicle, a user guide and information sheets will be provided in the manual.

--Scott Holland  EMAIL

Body

 

 

 


 




 

 

 

 

Drive Train

 

 

 

 

 

 

 

 

Made entirely of aluminum, the crawler is corrosion resistant, lightweight, and strong. All assembly is through bolts so that future modifications are easily accomplished. The triangular track design is ideal for mounting various terrain. The track assemblies are modular and may be removed with four bolts. Access to the batteries is via a hinged door that doubles as a skid plate. The door can be opened with the removal of two bolts. Behind the batteries are the motors followed by the electronic components. The heaviest components are toward the front of the crawler for center-of-gravity considerations. A wooden sheet will be mounted on the crawler for the attachment of various electronic components.

--Chris Colasanti  EMAIL

(Hardware/ Metal)
http://www.mcmaster.com/


Belt design
From our size specifications to give a low center of mass, and from the necessity of a riser to climb stairs, we came up with a belt length of around 85". We chose a 3" wide- double sided timing belt to give us positive drive characteristics, and a grippy outer surface. The choice of 1/2" pitch was arbitrary.

Pulleys
We needed pulleys that were 3" wide and 1/2" pitch. Flanges are necessary to make the belt track straight. Cast Iron pulleys are heavy, but very strong, and aid in keeping the center of gravity close to the ground.

Shaft
1/2" shaft is large enough to carry the weight of the crawler, and is a standard bore size available in pulleys and chain drive gear. The shaft through the pulleys is unhardened steel shaft with a 1/8" keyway to provide torque transfer in the drive pulleys. The Road wheels are supported by 1/2" aluminum shaft.

Chain Drive
The chain drive will carry power from the motors in the center of the unit to the rear pulley, which will drive the belt. Using a chain drive allows the motors to be located farther forward, which adds to stair climbing center of gravity concerns. We are using 3/8" pitch chain and a 2:1 ratio. The chain length is around 4 feet per track.

Road Wheels
The road wheels are plastic lawnmower deck wheels ~5" diameter with a 1/2" bore. There are two road wheel axles with two road wheels per axle on each track frame. The wheels will be held in the center of the shafts by shaft collars. The purpose of these wheels is to distribute the weight of the vehicle and improve maneuverability by shortening the ground contact length.

--Jake Brandspigel   EMAIL

(Belts)
http://www.beltcorp.com/

(Belts/Pulleys)
http://www.gates.com/


Crawler Body


Crawler Body


Crawler Body


Frame Support


Frame Support


Pulley


Motors


The introduction of the new, high current, speed controllers has helped to resolve our motor problems. Our sponsor also took the liberty of providing us with a pair of 24 volt wheel chair motors that will work well with the new speed controllers. While both pieces of equipment are rated at 24 volts, they will work nicely at 12 volts. The motors have dual shafts and built in gear reduction that has turned out to be the correct amount of reduction to provide a top speed of around 3 mph for the crawler. Also, the motor has a built-in mounting base for easy mounting to the crawler body. The stall current of the motors, which was 80 amps, was found by reading the specifications sheet provided by the distributor that sold them on the internet. The speed controllers are rated for running constantly at 60 amps, so we think that an occasional spike to 80 amps will be absorbed easily by the controllers.

--Robert Mulfinger  EMAIL

(Motors)
http://www.npcrobotics.com/


Motors

Circuitry The ME462 Students will have the capability of controlling the crawler by means of a processor that is capable of a pulse width modulated signal. The signal will be sent to a speed control through a 9pin parallel connection mounted to a box that contains the speed controllers.

The 9pin connection was originaly intended for a Vantec Dual forward/reverse Speed Controller (seen in schematic on page 2). The Vantec used a bit input that controled the duty cycle. Since the Vantec speed controller that we had could not handle the current, and due to a high demand of the sale and back order of this device, we decided to change the controller. The controller that we will use will be a Victor 883 Speed controler.

The Victor 883 Speed Controller can handle up to 30 Volts and a maximum 30 continous amps. Two controllers will be used on for the right and one for the left side of the crawler. Two fuses will be inline with the 12v power input of the controller. A kill switch will be added to disable the power if loss of control of the device.

In the schematic it also shows two switches, one for each controler. These switches have indicator lights to let the user know if the device has power. We are still debating wether or not we will put them in.

--Ryan Irwin  EMAIL

(Motor Controllers)
http://www.ifirobotics.com/


New Circuit Schematic for Crawler

Progress:

The mechanical and electrical fabrication and assembly are nearing completion and will be finished in order to present the entire product to our sponsor during the project showcase on Friday, May 2nd, 2003. A preliminary assembly and test drive of the rover allowed us to determine areas of adjustment in our design such as trimming the track frames and lengthening the tensioning slots in the upper section of the track assembly. As we near the completion of the project, the manual will be constructed and a report will be provided which details recommendations for future improvement on our design.




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