The Mars Rotacaster Rover – Part II

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Lookout NASA, you have Rover competition. And it uses the amazing Rotacaster Omni-wheels for unsurpassed manoeuvrability in confined spaces. The Mars Rotacaster Rover is based on the current NASA Mars Rovers with their unique suspension set-up.

The Mars NASA Rover Rocker Bogie Suspension

The NASA Roker-Bogie System

The Rocker-Bogie design has no axles or springs and allows the rover to climb over obstacles, such as rocks, that are up to twice the wheel’s diameter in size while keeping all six wheels on the ground. As with any suspension system, the tilt stability is limited by the height of the center of gravity. Systems using springs tend to tip more easily as the loaded side yields. The system is designed to be used at slow speeds of around 10 cm/s, so as to minimize dynamic shocks and consequential damage to the vehicle when surmounting sizable obstacles.

Construction of the Mars NASA Rover Rocker-Bogie System

JPL states that this rocker bogie system reduces the motion of the main MER vehicle body by half compared to other suspension systems.

Each of the rover’s six wheels has an independent motor. The two front and two rear wheels have individual steering motors which allow the vehicle to turn in place. Each wheel also has cleats, providing grip for climbing in soft sand and scrambling over rocks. The maximum speed of the robots operated in this way is limited to eliminate as many dynamic effects as possible so that the motors can be geared down, thus enabling each wheel to individually lift a large portion of the entire vehicle’s mass.

In order to go over a vertical obstacle face, the front wheels are forced against the obstacle by the center and rear wheels. The rotation of the front wheel then lifts the front of the vehicle up and over the obstacle. The middle wheel is then pressed against the obstacle by the rear wheels and pulled against the obstacle by the front until it is lifted up and over. Finally, the rear wheel is pulled over the obstacle by the front two wheels. During each wheel’s traversal of the obstacle, forward progress of the vehicle is slowed or completely halted. This is not an issue for the operational speeds at which these vehicles have been operated to date.

SOURCE: Wikipedia

 

After the proof of concept version shown in the previous video I have refined the chassis and added object detection. The Rover is now completely Autonomous, using 6x Rotacaster Omni-wheels with each corner wheel driven via a small LEGO Power Functions Motor. The Left and Right Motors are paralleled together and connected to the NXT Motor Ports via a pair of Power Functions adapter cables.

The Mars Rotacaster Rover Demonstration – Part II

As can be seen from the video, the Mars Rotacaster Rover works brilliantly. Having the ability to turn in its own length without the need for normal mechanical steering. This is achieved, thanks to the unique design of the Rotacaster Omni-wheels. The LEGO Rocker-Bogie design work well, imitating how the NASA Mars Rover’s Bogie System works. The whole Rocker-Bogie mechanism allows the wheels to easily flow over an obstacle. I do like it when a plan finally comes together!

The following images show the progression of the Mars Rotacaster Rover’s Rocker-Bogie as it negotiates a small hill in the form of a open DVD case raised in the middle by a 6x Stud LEGO Riser.

The Mars Rotacaster Rover Rocker Bogie Suspension
The Mars Rotacaster Rover Roker Bogie Demonstration – Part 1
The Mars Rotacaster Rover Rocker Bogie Suspension
The Mars Rotacaster Rover Roker Bogie Demonstration – Part 2
The Mars Rotacaster Rover Rocker Bogie Suspension
The Mars Rotacaster Rover Roker Bogie Demonstration – Part 3
The Mars Rotacaster Rover Rocker Bogie Suspension
The Mars Rotacaster Rover Roker Bogie Demonstration – Part 4

Stay tuned for further developments…..

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The Mars Rotacaster Rover

Part I Lookout NASA, you have Rover competition. And it uses the amazing Rotacaster Omni-wheels for unsurpassed maneuverability in confined spaces. There is no need of a steering mechanism to ... Read more

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