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Rocker + Differential | 4 | Each side of the 4-wheel drivetrain is mounted on a "rocker", which connects to the chassis on a pivot joint PROS CONS Has to lift more of the rover's weight at a time Requires a lot traction to scale tall obstacles More bounce to chassis Higher potential to tip over sideways from climbing tall obstacles
| ITU Rover Team, 2020 Tied for #3 overall ranking for SAR 2020 Use of aluminum tubes, assembled by custom hubs and rivets(?) Apepars to traverse terrain moderately slow and very carefully Appears to have minimal issues with turning 1m in width x 1.1m in length
Queen's Space Engineering Team Tied for #12 overall ranking for SAR 2020 Trapezoidal rocker design to improve the members' ground clearance Constructed using aluminum boxtube, gussets, and rivets Minimal footage of it traversing terrain, but appears to move carefully Appears to have minimal issues with turning. Has a small turning radius
UW 2020/2021 Drivetrain |
Rocker-Bogie + Differential | 6 | The front part of the rocker has the first set of wheels, while the back of the rocker implements a bogie system that hosts the other two sets Idea is that all six wheels passively contact the surface at all times NOTES: The lengths of the rocker and bogies and the position of each joint should be defined such that the front pair of wheels experience the lowest normal force Appears that some URC teams are doing rocker-bogie but backwards? The front wheels should be the ones mounted at the end of the rocker arm
PROS Less forward thrust required for climbing obstacles, since the rover is only lifting 1/3 of its weight at a time Provides more traction while scaling obstacles. This is because it has four wheels pushing the front wheels over Equal wheel pressure with the ground at all times
CONS More calculations and simulation required to design effectively Heavier, complex design Requires one actuator per wheel, as a gearbox and chain rigging would be hard to implement while still maintaining ground clearance Rover is optimized to traverse obstacles in one direction Unstable at high speeds, as it risks damage to the suspension arms due to the suspension speed
Resources... | Team Anveshak, 2020
Tied for #5 overall ranking for SAR 2020 Constructed using carbon fibre box tube + aluminum gussets + fasteners Modeled their drivetrain angles in MATLAB to increase its performance through bumpy terrain Appears to have a smooth ride → chassis stays rather level throughout the rover's traversal through uneven terrain Appears to have minimal issues with turning. Has a small turn radius
UW 2019 Drivetrain
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Two Bogie Suspension + Differential | 6 | Has front and rear bogies that pivot off of the middle wheel and are constrained by the V-shaped linkage mounted to the chassis Like the rocker-bogie design, idea is that all six wheels passively contact the surface at all times PROS Easier to design for low CoG while maintaining similar flexibility to a rocker-bogie Easier to mount dampeners to increase stability at high speeds Less forward thrust required for climbing obstacles, since the rover is only lifting 1/3 of its weight at a time Provides more traction while scaling obstacles. This is because it has four wheels pushing the front wheels over Equal wheel pressure with the ground at all times Can scale obstacles in either direction
CONS Few resources available More calculations and simulation required to design effectively Heavier, complex design Requires one actuator per wheel, as a gearbox and chain rigging would be hard to implement while still maintaining ground clearance
| Nova Rover 2019/2020/2021 Members composed of aluminum tubes that are welded together Smooth ride over short obstacles (~15 cm, so what is required). No footage of it climbing over large obstacles) Appears to have minimal issues with turning
Missouri S&T Mars Rover Design Team, 2020 Mars Rover Manipal, 2020 + 2021
Tied for #3 overall ranking for SAR 2020 W-frame pivots at the middle wheel and is constrained by two linkages at front and back mounting points on the chassis Linkages are constrained by torsional springs Construction is composed of aluminum boxtube Design was simulated in Solidworks? Performed both a kinematic and a dynamic simulation of it traversing vertical drops
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Three Bogie Suspension | 6 | Front wheels on bogies with a 4-bar mechanism between the wheels to divide the load Intention is to have all wheels passively contact the ground and be able to traverse tall obstacles with more stability PROS Rear rocker increases stability and reduces chances of tipping over Can climb over very tall obstacles Simpler to design? Don't have to optimize for member angles Less forward thrust required for climbing obstacles, since the rover is only lifting 1/3 of its weight at a time Provides more traction while scaling obstacles. This is because it has four wheels pushing the front wheels over Equal wheel pressure with the ground at all times
CONS Increase pivoting joints and mounting locations off of the chassis Requires one actuator per wheel, as a gearbox and chain rigging would be hard to implement while still maintaining ground clearance Rover is optimized to traverse obstacles in one direction Unstable at high speeds, as it risks damage to the suspension arms due to the suspension speed
| Space Concordia, 2019-2020
OSURC Mars Rover 2020
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Independent Wheel Suspension | 4 or 6 | Idea is that each wheel can move independently to allow for passive contact with the ground Keeps the wheel perpendicular to the ground by using a 4-bar linkage No differential bar used – held up exclusively by its suspension system PROS Individual drive systems → can easily repair with a replacement Suspension provides force on the wheels into the ground, therefore increase traction Stable at high speeds
CONS Chassis jostles around more, nothing attempting to balance it between the suspended wheels Higher potential to tip over sideways from climbing tall obstacles Requires a separate mounting point for each wheel (heavy, makes the frame larger) Complex design, not easy to maintain Requires one actuator per wheel
| RUDRA, 2020
Tied for #11 overall ranking for SAR 2020 Uses double-wishbone suspension on each wheel Front wheels pivot off of the rectangular face of the frame, while the rear wheels pivot off of the chamfered face Appears to have minimal issues turning
IMPULS Team, 2020 Tied for #10 overall ranking for SAR 2020 Uses double-wishbone suspension on each wheel Front and rear wheel pivot of the front faces of the rover Composed of custom acrylic(?) members Minimal footage of it turning, but appears to face little resistance (though, is moving slowly)
Nova Rover 2018 Score of 32/100 for Extreme Retrieval at the 2018 competition Uses double-wishbone suspension on each wheel Each wheel has the same pivot style, i.e. off of the same side face Wide wheel base. Appears to have minimal issues turning
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2-Point Pivot + Differential | 4 | Idea is to have the front wheels with an individual, spring-loaded suspension system and to have the rear wheels roll over the already conquered obstacles PROS Simplified version of the Independent Wheel Suspension type of drives → only the front requires spring-loaded suspension Suspension provides force on the wheels into the ground, therefore increase traction Rear, rocker wheels allow for the use of a differential bar that keeps the chassis more stable
CONS Optimized for traversal in one direction Requires springs Higher potential to tip over sideways from climbing tall obstacles Additional mounting points for each wheel
| Michigan Mars Rover Team, 2020 #1 overall ranking for SAR 2020 Designed to absorb frontal impacts Composed of carbon fibre boxtube Chassis has structural inserts implemented at high-stress locations Appears to have minimal issues turning
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