This page (revision-54) was last changed on 2021-10-02 05:56 by Murray Altheim

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Mars Rover
MarsRover

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[{Image src='attach/MarsRover/Open_Source_Rover_Patch.jpg' link='attach/MarsRover/Open_Source_Rover_Patch.jpg' caption='Open Source Rover Patch (click to enlarge)' width='200' align='right' class='imgFloatRight'}]
I've been collecting ideas for building a __[Mars Rover]__. This can easily cost a few thousand dollars and I'm not quite sure yet that I'm willing to fund such a venture, but it's fun to dream (and plan).
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I've been collecting ideas for building a Mars Rover. This can easily cost a few thousand dollars and I'm not quite sure yet
that I'm willing to fund such a venture, but it's fun to dream (and plan).
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I recently came upon a JPL paper that goes into quite a lot of detail about the Mars Exploration Rovers (MER), Spirit and Opportunity*. These were the two rovers that landed on Mars in 2004 and ran until 2010 and 2018, resp., a very long time past their planned mission of 90 days. This is probably the most detailed description I've found of a NASA rover's software.
I recently came upon a JPL paper that goes into quite a lot of detail about the software controllign the Mars Exploration Rovers (MER), Spirit and Opportunity*. These were the two rovers that landed on Mars in 2004 and ran until 2010 and 2018 (resp.), a very long time past their planned mission of 90 days. This is probably the most detailed description I've found of a NASA rover's software.
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! Contents
__ Contents __
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If one were to use a stereo camera like the [RealSense T265|RealSenseT265] (rather than motor encoders) for odometry, here's a paper by, again, some of the same authors:
* ''[Two Years of Visual Odometry on the Mars Exploration Rovers|https://onlinelibrary.wiley.com/doi/pdf/10.1002/rob.20184]'' \\ Mark Maimone, Yang Cheng, and Larry Matthies, Field Report, \\ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
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Admittedly, that one is way over my head, but interesting.
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An easier read is:
* [The Mars Robot Making Decisions on Its Own|https://www.theatlantic.com/technology/archive/2017/06/mars-curiosity-rover/531339/] \\ Thanks to artificial-intelligence software, the Curiosity rover can target rocks without human input. \\
[Marina Koren|https://www.theatlantic.com/author/marina-koren/], ''The Atlantic'', 24 June 2017
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[{Image src='attach/MarsRover/Open_Source_Rover_Patch.jpg' link='attach/MarsRover/Open_Source_Rover_Patch.jpg' caption='Open Source Rover Patch (click to enlarge)' width='120' align='right' class='imgFloatRight'}]
%%information
One thing that __almost__ goes without saying: the vast majority of the hobbyist Mars Rovers I've found are, despite being very complicated and often expensive mechanisms, they are almost without fail toys, [remote-controlled vehicles|RemoteControlledVehicle], and only rarely qualify as __[Telerobotics]__. Very few have operational sensors, and so far (I'm trying to think...) none of them I've seen are __autonomous robots__, or even semi-autonomous. Put it this way, if you've built an autonomous Mars rover, contact me and I'll put a link or a description or a page up about it.
%%
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There's a huge impact on ground clearance if your motors are down there banging into rocks and such. The difficulty seems to be locating some suitably deep wheels. I can't imagine simply 3D printing them, as plastic wheels wouldn't last very long on rocks or concrete. I want a robot that can ''actually roam outdoors''. Also, unless the motors have durable ball bearings protecting the shafts, there needs to be some significant insulation between the motor shaft and the shocks that the wheels will create as they go over rough surfaces. Unless the robot is only going to run indoors, and then what's the point?!
I'm likely to try to build a rover a bit smaller than some I've seen on the Web — but not toy size — something using the same motor controllers I've used on my other robots, maybe 22mm or 25mm diameter motors with stall currents around 5 amps. The next step up from there and we're talking much larger motors, beefier controllers, larger batteries, etc. ''Too large'', especially for my budget.
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[{Image src='attach/MarsRover/km01-design.png' link='attach/MarsRover/km01-design.png' caption='Preliminary Desing (click to enlarge)' width='300' align='right' class='imgFloatRight'}]
[{Image src='attach/MarsRover/km01-design.png' link='attach/MarsRover/km01-design.png' caption='Preliminary Desing (click to enlarge)' width='300' align='left' class='imgFloatLeft'}]
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There's a huge impact on ground clearance if your motors are down there banging into rocks and such. The difficulty seems to be locating some suitably deep wheels. I can't imagine simply 3D printing them, as plastic wheels wouldn't last very long on rocks or concrete. I want a robot that can ''actually roam outdoors''. Also, unless the motors have durable ball bearings protecting the shafts, there needs to be some significant insulation between the motor shaft and the shocks that the wheels will create as they go over rough surfaces. Unless the robot is only going to run indoors, and then what's the point?!
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\\
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I've analysed the various options but am not convinced of a suitable set of components, so I've ordered
the parts for __1/6th of the drive system__: i.e., one motor, several wheel/tire options, a steering servo with mount, a bearing assembly for a rocker arm, and an assortment of possible structural hardware to put it all together. The shipping charge fo rth order was US$120. Ouch. I'll probably blog about things when the parts come in and I've had some time to play.
I've analysed the various options but am not convinced of a suitable set of components, so I've ordered the parts for __1/6th of the drive system__: i.e., one motor, several wheel/tire options, a __ServoBlock__ (a steering servo with mounting brackets), a bearing assembly for a rocker arm, and an assortment of possible structural hardware to put it all together. The ''shipping charge'' for the order was US$120. Ouch. I'll probably blog about things when the parts come in and I've had some time to play.
[{Image src='attach/MarsRover/servoblock_on_servo.jpg' link='attach/MarsRover/servoblock_on_servo.jpg' caption='ServoBlock (click to enlarge)' width='200' align='left' class='imgFloatLeft'}]
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[{Image src='attach/MarsRover/osepp-tank-wheel.jpg' link='attach/MarsRover/osepp-tank-wheel.jpg' caption='A "Tank Wheel" (click to enlarge)' width='300' align='right' class='imgFloatRight'}]
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[{Image src='attach/MarsRover/osepp-tank-wheel.jpg' link='attach/MarsRover/osepp-tank-wheel.jpg' caption='A "Tank Wheel" (click to enlarge)' width='300' align='right' class='imgFloatRight'}]
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* [Replica Mars Rover Curiosity outside the lab... exploring the real world...|https://youtu.be/rZESgtjL0B0] YouTube video of scale model of NASA Mars Rover using ServoCity Actobotics parts, Pololu motors, etc. Built by [Carlos Sicilia Til|https://www.youtube.com/channel/UCIgnjQmL78DlHMuank2THLg] who indicates his servos as: 4kg.cm wheel servo. Arm servos: 25kg.cm at shoulder, 4kg.cm at elbow and 1.5kg.cm at tool holder.
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| 2 | 12V max CXT® Power Source w/ USB port (YL000000003) | $95.00 | $190.00 | | Toolshed Petone | [https://www.makitatools.com/products/details/YL00000003]
| 2 | 12V max CXT® Power Source w/ USB port (YL00000003) | $95.00 | $190.00 | | Toolshed Petone | [https://www.makitatools.com/products/details/YL00000003]
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* [Mars Exploration Rover|https://en.wikipedia.org/wiki/Mars_Exploration_Rover] on Wikipedia
* [Sojourner Project Home Page|https://mars.nasa.gov/MPF/rover/sojourner.html] (~1996, JPL)
** [A Description of the Rover Sojourner|https://mars.nasa.gov/MPF/rover/descrip.html]
** [Rover Telecommunications Photo Gallery|https://mars.nasa.gov/MPF/rovercom/pix.html]
** [Mars Pathfinder Microrover Publications|https://mars.nasa.gov/MPF/roverctrlnav/publications.html]
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* [In-situ Exploration and Sample Return: \\ Autonomous Planetary Mobility|https://mars.nasa.gov/mer/mission/technology/autonomous-planetary-mobility/], NASA
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[{Image src='https://raw.githubusercontent.com/jakkra/Mars-Rover/master/.github/driving.gif' link='https://github.com/jakkra/Mars-Rover/blob/master/.github/driving.gif' caption='Mars Rover by Jakob Krantz' width='300' align='right' class='imgFloatRight'}]
* [Replica Mars Rover Curiosity outside the lab... exploring the real world...|https://youtu.be/rZESgtjL0B0] YouTube video of scale model of NASA Mars Rover using ServoCity Actobotics parts, Pololu motors, etc. Built by [Carlos Sicilia Til|https://www.youtube.com/channel/UCIgnjQmL78DlHMuank2THLg] who indicates his servos as: 4kg.cm wheel servo. Arm servos: 25kg.cm at shoulder, 4kg.cm at elbow and 1.5kg.cm at tool holder.
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* [The Open Source Mars Rover, One Year Later|https://hackaday.com/2020/07/02/the-open-source-mars-rover-one-year-later/] by Jakob Krantz (on Hackaday), uses LoRa to communicate with the (human) controller, with [open source code|https://github.com/jakkra/Mars-Rover] on github; he uses a separate 12v-5v switching voltage regulator for each servo (!) and outlines the hardware in more detail on the github page
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For not only a Mars Rover but other designs, a bit old (circa 2013) but interesting, see the [Actobot Blog|https://beatty-robotics.com/actobot/] from __[Beatty Robotics|https://beatty-robotics.com/]__. Their gallery alone is worth the visit.
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This page (revision-54) was last changed on 2021-10-02 05:56 by Murray AltheimTop