Project starting up · Mobile robotics
JPL Rover
We are building a six-wheeled rover like the ones on Mars, starting from the design JPL has published.
- 144 mm wheels, always in contact with the ground thanks to the rocker-bogie suspension
- 6
- motors: six drive the wheels, four steer them
- 10
- the stated top speed, roughly
- 1.6 m/s
- the cost of the parts as given by the project
- 1.600 $
For people who come from mechanical engineering, electronics and computer science, robotics
What it is
The JPL Open Source Rover is a small version of the six-wheeled rover that JPL, the NASA laboratory that builds the rovers for Mars, uses to explore the planet. The project dates from 2017 and has had several versions. Anyone can build one.
It is made only of off-the-shelf parts, mostly from the company goBILDA. The base version needs no metalworking. JPL has published the drawings, the parts list, the assembly guides and the software, and the project is certified as open hardware (OSHWA US002551).
The brain is a Raspberry Pi. To drive the rover, any connection a Raspberry Pi understands will do: Bluetooth, Wi-Fi, a USB joystick.
How it moves
On Mars the rovers have six wheels because a special suspension keeps all of them on the ground, even over rocks. The JPL design copies three ideas from it.
- 01
Rocker-bogie
Each side has an arm, the rocker, with the rear wheel. Halfway along there is a pivot holding a second arm, the bogie, with the front and middle wheels. This way one wheel can climb a rock without lifting the others.
- 02
Differential
A bar above the frame links the two sides. As the rover climbs, it shifts the weight from one side to the other.
- 03
Six-wheel steering
Four servos turn the corner wheels. The software decides where each wheel points and how fast it turns, so the rover can curve.
Inside a wheel motor
Each wheel has its own motor, a goBILDA Yellow Jacket 5203 series. An electric motor spins fast with little force. Moving the rover takes the opposite, and a planetary gearbox does it: it slows the motor down by a factor of 26.9 and the torque grows by about the same amount.
At the output the shaft turns at 223 rpm. With 144 mm wheels that is about 1.7 m/s, and that is where the top speed of about 1.6 m/s stated by JPL comes from. The gearbox can be swapped: a faster motor gives a quicker rover, but with less force.
- 01
Sun and planets
The motor shaft carries a small gear, the sun gear. Around it sit three planet gears, which rest on a ring gear with teeth on the inside, fixed in the housing. The planet gears roll inside the ring gear and carry the planet carrier along with them, which turns much slower than the sun gear.
- 02
Two stages
The planet carrier of the first stage turns the sun gear of the second. In the drawing the sun gear has 11 teeth and the ring gear 46: each stage slows things down by 5.18 times, and two stages make 26.9. goBILDA does not publish the tooth counts: the ratio is theirs, stages and teeth are our own reconstruction.
- 03
Encoder
On the back of the motor an encoder counts the turns. The software reads this number to know how far each wheel has really turned, and to correct the speed of each one when the rover turns.
The four corner wheels also have a steering servo, a goBILDA 2000 series with a 25-tooth output, mounted in a ServoBlock that passes the load to a bearing. It is the weak point of the rover: after a sharp impact the center shaft holding two of the servo's gears can break. The JPL guides explain how to open it and replace the gears without throwing it away.
The main parts
The project uses almost only parts from the goBILDA catalog. These are the main ones, from the official list.
| Part | Item | Qty |
|---|---|---|
| Wheels | goBILDA Wasteland, 144 mm in diameter and 52 mm wide | 6 |
| Wheel motors | goBILDA Yellow Jacket, 26.9 to 1 reduction, 223 rpm | 6 |
| Steering | goBILDA 2000 series servo with ServoBlock | 4 |
| Frame | square beams of 328 mm, 232 mm and 96 mm | 4, 5 and 8 |
| Suspension | goRAIL rails of 288 mm, 120 mm and 96 mm | 2, 2 and 6 |
| Computer | Raspberry Pi | 1 |
| Battery | 7.2 Ah LiPo, with at least 3 hours of driving on rocky ground | 1 |
The figures are those of the JPL list. Prices and versions change: before ordering, read the list again.
What you need to build it
- 01
Mechanics
Assemble the frame, the suspension and the wheels. The three parts are built in parallel. The frame plates are laser cut, also through an online service.
- 02
Electronics
Solder, wire, and check every wire with a multimeter before powering on. The boards and the motors have to be connected in order.
- 03
Software
The rover is driven by a Raspberry Pi: you need the basics of Linux, Python, Git and ROS. The code lives in a separate repository, osr-rover-code.
How we work
This is the work plan, not what we have already done.
- 1Read. All the documentation, guide by guide, and the parts list with today's prices.
- 2Order and assemble. Frame, suspension and wheels are built in parallel, each by one person.
- 3Wire. Boards, motors and servos, with a continuity test on every wire.
- 4The software. Install the JPL code and drive the rover with a joystick.
- 5Something of our own. The project includes expansions, like a mast with a head and a robotic arm. We choose with the team what to add.
Where we are
- November 2026The project starts. We read the JPL documentation and make the parts list.
- TodayWe are looking for people to form the team: mechanics, electronics, software, and anyone who wants to organize the work.
- Next stepOrder the parts and assemble the frame and the suspension.
Sources
- JPL, Open Source Rover, repository nasa-jpl/open-source-rover on GitHub: description, parts list and guides for mechanics, electronics and wiring.
- JPL, osr-rover-code, the rover software, on GitHub.
- OSHWA, open hardware certification US002551.
- jplopensourcerover.com, the project page.
- JPL, parts list: goBILDA 5203 Yellow Jacket motors at 26.9 to 1 and 223 rpm, goBILDA 2000 series servo; servo gear replacement guide.
Do you want to work on it?
You do not need experience and you do not need a CV. Write to us: we invite you to the next meeting, where you meet the team.