Rover Design Idea 2

roverid2The principle behind this design is that the rover is a micro-rover, similar to the Sojourner.

>Has 6 wheels

>Is a very small and compact size but everything is housed within the body

>Camera is in fixed position

>Could also have a simulated ‘base unit’ on the terrain that users can drive onto and find out about

>However ground clearance would be comparatively low

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Rover Design Idea 1

roverid1This design is supposed to replicate the Nasa rovers and be a scaled-down version of the Spirit and Opportunity rovers.

>It has 6 wheels on long ‘legs’

>It has a camera mounted on a ‘neck’ that has the potential to be moveable

>It features a layer of solar panels on the top to cover the electronics from view

Research – The Look of the Rover

There are several possibilities for replicating existing rover designs that are already on the surface of planets or that plan to go there.

Google Lunar XPrize

The teams competing in this competition to get a lunar rover to the moon and to send back a broadcast to Earth have employed many different designs for their proposed rovers.

This design is like a buggy or car in that it uses four wheels. It seems quite compact and could house the

necessary electronics and equipment within the conical body.

This design has wheels in a loose sense of the word, but instead of tires there are flexible feet on spokes that are designed to cope with rough or uneven terrain. The chassis is flatter and provides a large area for solar power cells.


 This rover design is comprised of two large wheels that encompass the body to give it a decent ground clearance. It has two smaller wheels for stability support at the back, but several teams seem to have gone for a design where there are two large wheels with the main body between them. It doesn’t leave room for many scientific instruments, but it is perhaps an effective way of traversing large distances across the surface.

Nasa’s Mars Rovers

Nasa’s Opportunity Rover (and its twin Spirit which is no longer contactable) was launched in 2003 and landed on Mars in January 2004. It has six wheels on long stabilising legs, which ensures that it has as many wheels on firm ground at one time as possible. It has a long, movable ‘neck’ on which its main camera is situated, and many scientific instruments including scoops and collectors for analysing surface samples. It has large photovoltaic cells to harness as much solar energy as possible due to the planet’s further distance from the Sun. It’s primary function is to travel and explore as much of the surface as possible while performing experiments along the way.

Nasa’s Curiosity Rover (also known as the Mars Science Laboratory) is a much larger rover, approximately the size of a car. Although is looks quite similar to Opportinity, there are many more scientific instruments on it. A major difference is the lack of solar cells. Curiosity has a radioisotope thermoelectric generator power source that means that it does not require sunlight to function. The earlier static Mars landers Viking 1 and 2 used this method.

A much smaller rover was launched aboard the pathfinder mission to Mars in 1997. Sojourner is only a micro rover, but it still has the same six-wheeled design. There are less scientific experiments done using this rover, and it had to remain close to its base lander unit.

This image (right) shows the comparative size of the wheels of these three Nasa Mars Rovers. When designing my rover, I need to think about the size and whether I want to scale a larger design of rover down, or make it on a 1:1 scale.


roverI also need to decide whether I choose to base it on an existing rover, or look to the future of rovers and what they might look like, or create a design that I think might represent the future of rovers. This image (left) is the proposed design for Nasa’s 2020 mission to Mars. It is very similar to Curiosity, but has more and better instruments designed to inform us of the possibility of human travel to the planet.


Idea Development – Researching Rover Parts

I first looked at existing rovers that have been created using the Raspberry Pi, and what electronic parts they used.

These two projects seemed to offer the most information:

Curiostiy Pi

Raspberry Rover

It seems that I can either wire through a motor driver board, or simply use a breadboard and resistors.

Here is a diagram of the Raspberry Rover which uses a motor driver board (click to enlarge):


The board takes the signal from the GPIOs and controls the voltage directly so that there is no need for resistors. Both wheels on the same side are linked to the same set of 2 outputs. It is probable that this rover uses tank controls (to turn, wheels on one side reverse while on the other they continue forwards) as there is no servo to control the steering.

This is a diagram of the wiring on the Curiosity Pi (click to enlarge):

Instead of motors and a motor driver, this rover uses 16kohm and 180ohm resistors which are connected to servos. This controls steering, camera motion and the drive of a single front wheel. This method may be more complicated when more wheels need to be controlled.

Testing Technology – Raspberry Pi and Battery Pack

DSC_0039

In order to test the feesability of certain aspects of the project I decided that I needed to run some tests.

  1. Streaming the Pi Camera module to another device. I used MJPEG Streamer which sends a JPEG image every frame. The result is a Java, Javascript or HTML stream. This is useful as it can be accessed on all devices on the network that have an internet browser. The stream has a fairly low frame rate, and there is no sound, but this might replicate the real video feed being sent from Mars. There are other options however but this was simple to set up and easy to run.
  2. I purchased a 12000mAh rechargable battery pack that has an output of 5V via a USB connector. This is one of the largest capacities of such packs that are readily available. I tested the total running time of the pack when using just the camera module and wireless adaptor on the Pi to run MJPEG Streamer, and the pack’s battery lasted >6 Hours. This means that it would potentially be feasible to use this in an actual museum exhibit or installation – allowing for power consumed to control the rover this may then require only one or no battery changes within a day.

Idea Development – Technology

I will need to combine multiple technologies to realise the project successfully.

The rover will require a chassis with wheels and motors to drive the wheels. These can be acquired in kits, or I can put one together myself. If I am replicating the current Mars rovers then I will need one with six wheels that are on elongated struts.

A touchscreen tablet device could be used to both control the rover, to view the video feed or both.

The Raspberry Pi will need an extraneous wireless power source that can be fitted to the rover with it. A rechargeable battery pack with a 5v output will work well for this.

The Pi will also need a webcam or the compatible camera module.

A wireless connection between the Pi and another device is necessary for control and to relay the video feed.

If the video feed and controls are to be on the same interface, HTML or JavaScript may be needed to create a useable interface that can be connected to on the control device.

Alternate control devices:

  • PC keyboard
  • Joystick

Alternate video viewing devices

  • TV Monitor
  • Laptop screen

Chroma Keying ( sometimes known as greenscreen or bluescreen) could be used to show images or videos to the user through the same video feed as the camera. A narrative or other information about space or rovers or telepresence could be then implemented easily.

Research – Telepresence Art

Rara Avis

This work by Eduardo Kac featured a telerobotic parrot that could be controlled by users via the internet. Situated inside an aviary with living birds, the speakers and movement of the parrot coud be used to change the birds’ behaviour or the camera feed used to give a literal ‘bird’s eye view’.

Telegarden

In this work, users could control a telerobotic arm to tend to plants via the internet. As multiple users could interact and would return to care for the plants, this created a social network of people around the garden.

The Robospatium

The Robospatium is an online work by Norbert Heinz in which he has created several different robots that can be controlled by telepresence. He has used the theme of space, and calls one of them a lander, as it gives an overview of the space, and the others are rovers that can be driven around.bild01