I have wanted to create a kind of mini project plan and people are also asking for more details so here is a first pass. I am going to break it down into the two main subsystems of the rover: mechanical and electrical.
For all of those mechanical engineers out there keep in mind that I am an EE that mostly programs right now . Here is grossly simplistic drawing(side profile).
One of the questions is what material do we use and how do we put together the frame. The two main methods and materials are aluminum and steel and bending or welding the angles. We could create machined joints but I figure that would be cost prohibitive. All of the red dots signify angles that would need to be bent or welded. The blue dot is the hinge that connects the two main piece that constitute the suspension. This will need to be as strong as possible. Since this is a side profile this will be mirrored on the other side of the rover. The two green dots are the crossbar(s) that are the lateral support and will hold the cargo hold. This will also need to be very rugged. I have a very specific idea for implementing this but I am trying to figure out the best way to communicate it to the mechanically minded out there. One important feature is that I would like for the system to be broken down into components fairly quickly so it can be shipped and transported as easily as possible. If you disconnect the crossbar(s) and the hinges we have 5 main pieces of the frame. Also some sort of mounting bracket/plate will need to be welded to attach the each wheel. Another design consideration is all of the supports need to be hollow. This would allow cable routing that will protect the wiring for the motors. The cargo hold must be designed and how it attaches to the crossbar.
The electrical system is fairly straight forward but I am worried about the cost and feasibility. To minimize cost and complexity the front and back wheels will not have stepper motors at least not in the first implementation. I hope that having the ability to control each motor will allow turning similar to that of a vehicle with treads. My target for the wheels are 10″ tall and 3-4″ wide. Each wheel will be powered by a 500 watt brushless dc motor each with a controller located in the cargo hold. The ideal situation would be to have hub motors. I have been doing some research on Alibaba.com and have found some good candidates but nothing that matches exactly what I am looking for. I envision building a testbed frame out of plywood to verify power and mobility of the motors. My main concern is the viability of the battery system. How many batteries are need to power the motors(weight concerns) and what is their runtime?
Any feedback is would be great.
So it took me a while to get the video done. I look so ridiculous on camera. Here is the link for the Open Rover Kickstarter Project. As one of the rewards, I have created t-shirts with the Open Rover Logo on them. A poll of my friends and family unanimously voted the black T as the best one. Here is a rendering.
Look forward to all of your support. Hopefully we can build some awesome robots.
I cleaned up the logo in Gimp and added the .com. I think it looks really good. We will see how it looks on stickers and T-shirts.
It has been a busy two months but progress is being made. I have finished the model. It should give a good idea of the size and scope of the project. I have also been doing researching on potential motors and controllers. The cost and complexity of the motor and power system is my biggest concern. Here are some pictures of the model. I have also created a video with the rover next to my push mower. I hope to include it in the kickstarter video. That is the next stage of the project.
As a part of the rewards for the kickstarter project, I wanted to create a logo that could be used for stickers or T-shirts. Here is the latest version, I need to clean it up but I think it looks really good.
Having seen how easily robotics projects are done with an iCreate, I have wanted to develop a similar platform for outdoor use. I was hoping that iRobot would release a cheaper less durable version of the Packbot or one of its smaller siblings but that doesn’t look like it will be happening any time soon.
My initial plans were to design the platform in the same vein as the Packbot with treads and flippers, if not flippers, a versatile tread configuration for climbing objects. But making a cheaper platform with treads looks to be cost and complexity prohibitive. So with all of the MSL-Curiosity rover pictures flying around the web, I have decided to look into a platform based off of the rocker-bogie suspension.
It has been difficult to find detailed specifications of the Curiosity rover but I have come up with a basic design scaling down the platform to about the size of a push lawnmower(a little bit bigger). I have cut out some PVC and will be building a proof of concept just to see if I like the scale.
The end goals are:
- Create a 6 wheel rover.
- Each wheel will have its own motor and controller.
- The Rover will use the rocker-bogie suspension.
- The frame will be made of Aluminum.
- All documentation will be freely available upon completion of the prototype.
- Release kit and assembled unit similar to Makerbot Industries and Willow Garage if prototype is viable.
Optional elements would be to package a controller(Arduino Mega) that would have some sort of API to provide a basic interface with the motors. Once the platform is finished I can see using a Kinect and ROS to control it.
I would like to start a Kickstarter project to fund the prototype but I am having difficulty coming up with rewards to the various levels of funding. I plan on having 3 levels of rewards for funding $20-50, $50-100 and > $100. I am open for ideas on what would be appropriate rewards for those levels. The funding target would be $2,500.
Any additional thoughts would be great as well.
Open Rover is a project that will explore the potentional for a standardized outdoor robotics platform. The goal is to create an outdoor version of the iCreate™ from iRobot™. I hope to launch a Kickstarter project that will help fund the creation of a prototype. Header Image Credit: NASA/JPL-Caltech