DIY: Percevarence grass cutter
Introduction
Make a mower that resembles Percevarence: Six wheels with rocker-boogie suspension.
Designed for slow motion (10 cm/s).
Theory
Naming conventions
- 4WD or 4x4: Four wheel drive.
- AWD: All wheed drive
- 6x4: three axles, two of which provide torque to two axle ends each.
- 6WD or 6x6. H-drive.
https://en.wikipedia.org/wiki/Steering; see eg Ackermann steering.
Differential steering. Turning radius. Differential wheeled robots. Kinematics of differential drive robots. https://rossum.sourceforge.net/papers/DiffSteer/DiffSteer.html
https://thef1clan.com/2020/09/21/vehicle-dynamics-the-kinematic-bicycle-model/
The kinematics of mobile robots is clearly described in Robotics.SE article https://robotics.stackexchange.com/questions/8911/how-to-find-kinematics-of-differential-drive-caster-robot
Mathworks www site contains a good and simple reference for mobile robot kinematics equations, see https://www.mathworks.com/help/robotics/ug/mobile-robot-kinematics-equations.html
Skid steer dynamics is considered in the following paper https://www.joydeepb.com/Publications/icra2019_skid_steer.pdf
A detailed description of six wheeled robots made using Arduino on Instructables https://www.instructables.com/Remote-Controlled-6WD-All-Terrain-Robot/
Rocker-bogie
https://en.wikipedia.org/wiki/Rocker-bogie
The tension, forces on the single joint?
Differential Joint
The two rockers connect to each other and to the body through a differential. It keeps the body level. When one rocker goes up, the other rocker goes down, and the body angle is halfway between the angles of the two rockers.
Differential gearbox
Differential bar (linkage)
http://alicesastroinfo.com/2012/07/mars-rover-rocker-bogie-differential/
"Dynamic Rocker-Boogie"
Stress and tension (different parameters)
Approximate the stress and forces on the different parts of the rocker--boogie joints.
Wheel motors
https://zjmy-lu.en.made-in-china.com/
https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=10inch+300W+36V+Brushless+Motor+&selectedTab=product_en and https://www.alibaba.com/product-detail/DC-brushless-10-Inch-single-shaft_1600164251056.html?spm=a2700.galleryofferlist.normal_offer.d_image.a61d69d3yQtzhj&s=p
No axle motors.
Wattage. 500W?
References
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=rocker+bogie+mechanism+working+principle&btnG= First three (3) pages 2022.05.13.
https://studylib.net/doc/25318418/irjet-design-and-fabrication-of-rocker-bogie-mechanism-us... Design and Fabrication of Rocker Bogie Mechanism using Solar Energy. Rajat Murambikar, Vinay Omase, Vivek Nayak, Karan Patil, Prof. Yogesh Mahulkar.
Design Optimization of a Mars Rover’s Rocker-Bogie Mechanism using Genetic Algorithms. Franziska Ullrich, Ali Haydar Gokto ¨ gan, Salah Sukkarieh
ANALYSIS AND SIMULATION OF A ROCKER-BOGIE EXPLORATION ROVER Hervé Hacot, Steven Dubowsky, Philippe Bidaud2. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.33.9327&rep=rep1&type=pdf
Instrumented Rocker-Bogie Chassis Design and Net Traction Estimation. Timothy P. Setterfield. https://curve.carleton.ca/system/files/etd/e6ba9694-33ac-4a8d-8db1-ac548cce2220/etd_pdf/f176d20fd9fd9de537fea2656f5a39da/setterfield-instrumentedrockerbogiechassisdesignandnet.pdf
