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Sojourner Mars Rover

Motorized Sojourner Mars rover model.

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My plan is to build all the Mars rovers and I thought I would start at the start and work my way up. I could find no Sojourner model that meets my needs; to be as accurate as possible, be 3D printable and automate the movement. The model is scaled such that the largest part can be printed on a standard 3D printer, i.e. 220mm or smaller. The largest part on this model is the top solar panel. This gives a 1/3 scale model. The rover will move via solenoids and geared motors. These will be controlled with an Arduino. Since I already have the Earth Rover that has all the sensors and a Raspberry Pi to wirelessly present a web page for rover control, the decision was made for this model to be controlled via a removable wired joystick and no sensors to keep the cost down. It would be easy to add a pair of cameras and laser range finders along with a Raspberry Pi if desired.

The real rover has six driven wheels.  For simplicity only the four corner wheels will be driven and the two middle wheels will rotate freely.  The steering is accomplished using four servos, one at each corner wheel.  The go to steering maneuver for this rover seems to be turn the four corner wheels in and rotate in place.  All of these motors will need motor drivers.  For this I chose the L298N motor controller modules requiring 4 digital output pins.  One of them can drive two DC motors.  Each stepper motor is driven by an A4988 stepper motor driver requiring 2 digital output pins.  The directional input is via a joystick requiring 2 analog inputs.  The total input/output count is 16 digital output pins and 2 analog input pins.  A single Arduino Uno should work for this project.  

The color of the 3D printed parts are chosen to be as accurate as possible.  Some of the parts are printed using filament changes to produce more accurate looking parts and keep the assembly to a minimum.  One example is the solar panel.  The base of the panel is white with a single height copper layer followed by black solar panel modules.  Most slicers should be able to perform this trick including Cura and the Prusa slicer I use.  

  • Build Progress

    wglasford6 hours ago 0 comments

    Most of the 3D parts have been created and are being verified versus available hardware parts.  Here is the rocker and bogie arms.  The real arms are hollow but when doing test prints the arms at this scale are too flimsy so the arms are solid with holes drilled through the appropriate sides.  The wires will be zip tied to the outside of the arms instead of being routed through hollow arms.  Still waiting for the small servos to steer the wheels.  Unfortunately the really small servos have an 18 degree step but this should be OK because the only real steering maneuver used on this rover is to angle the wheels in and rotate in place.  

    Here is a close up of a test print of the solar panel.  The base of the panel is white and 5mm high.  Copper filament is then used to print a 0.15mm high layer followed by black 0.15mm high solar panel elements.

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