Friday, July 18, 2008

The robot did his first walking moves controlled through the CompactRio-Device of National Instruments. The next step is to implement the actuators. Furthermore the robots movement is now only specified by position and we want to add the parameter velocity as well. So I still got some things to do...

Monday, July 14, 2008

Concepts presented @ CDR

Our basic concept is a team-based implementation of two tethered devices: a wheeled rover providing overview sight, power supply and a communication bridge and a legged climber that will fullfill the main tasks as descend into the crater, sample some soil specimen, climb up the slope and return the samples to the landing site.

A fully covered second prototype of the legged robot ALF will be constructed and manufactured soon. The higher torsional stiffness allows more accurate control for reliable walking abilities and the cover protects the interior against sand and dust.

As a sampling mechanism, we are suggesting a drilling device (Archimedes screw) to draw the granular specimen. It will be located at the front and the suction procedure will happen in an animal-like way.


From the 9th to 10th of July, two of our members (David and Andi) went to ESTEC in Noordwjik to participate in the Critical Design Review of the LRC. Many impressions about the LRC, the other Teams, their ideas and ESA itself turned the short trip to an exciting event. We're looking forward with enthusiasm to the TRR and the competition in fall on Tenerife.

Sunday, July 6, 2008

Visit Einar Nilsen

Last Friday, Einar Nilsen came to visit our project. He works at the school of applied science in Buchs and has ample experience in the design of robotic systems. We showed him the existing prototype and discussed the drawings and sketches for our new version. It was great to get his input on these issues and we’re hoping to continue a collaboration with him.

The Start

With the advantage of having an existing prototype at hand, our first task was the identification of its strength and weaknesses. We looked carefully at the mechanical design, the electronics, and the controller, thereby defining the alterations we want to make to the existing system.

Mechanical Design:
The design of the legs proved to be well done. They are robust, flexible, and still lightweight and compact. We will have to make some small adaptations to the sensor placement and the integration of the elasticities. The only thing that will be completely new are the feet. They will be specially designed for a sandy environment and equipped with some climbing aids. But apart from that the overall leg design will remain the same.

In contrast to that, the main body will undergo a complete redesign. We need to increase the torsional stiffness, make room for the specimen collector (which also has to be developed), and increase the robustness such that the robot will survive a fall or tipping over. Last but not least, we have to cover everything and protect the interior from sand.

Adapting electronics will mean mostly adding components: Camera systems, wireless communication, additional sensors, on-board control, and power supply. We will use the same actuators as in the existing prototype as they turned out to have a great balance of size, weight, and power. We will add simple footswitches to detect ground contact while the robot is upright (we first wanted to actually measure the forces, but considering that the robot will undergo various leg configurations, this seems just impossible), there will be inertial measurement, and some supervising sensors. And most importantly, we will focus on a tight integration of electronic components into the mechanical hardware.

The development of the controls is naturally one of the most important parts in such a project. Right now we’re working with predefined trajectories. I.e., a set of open loop joint angles that lead to walking, turning, etc. This collection will be extended to include tasks like standing up, or turning back into an upright position, crawling, crabbing, and the like. The long term goal is, of course, the generation of the motor inputs on line, to allow flexible navigation and at some point fast and dynamic locomotion.

Friday, July 4, 2008

The Roots

As you can see below, our project group is a true student team. Andi, Martin, and Oliver constitute the core. They all just finished their Bachelor’s degree and agreed to work full time on the LRC project until they will continue with their Master’s. They will get additional support from a number of PhDs from our lab, and other undergrad and graduate students who, over some duration of time, will extend the team and contribute to specific subtasks.
Our LRC platform is based on the undergrad design project of Andi, Martin, and Atilla Yilmaz. During the last semester, they were developing a quadrupedal robot with series elastic actuation on the main joints of the legs. The goal was to develop a walking machine that is able to passively adapt to irregular terrain while walking statically, and can additionally use its elasticities to store energy during dynamic locomotion. Without knowing of the Lunar Robotics Challenge, they had named the robot ALF, already foreseeing that its future will not be limited to earth.
The project was a great success and we are certain, that a similar robot will perform well in the Lunar Robotics challenge. However, it is evident that we’re not even half way there yet. Major adaptations, improvements, and extensions have to be made to the original design, to get ALF space ready. This task will occupy us over the next couple of months.

Wednesday, July 2, 2008

Fabian (Teammember)

My name is Fabian Seitz and my part is the implementation of communication tasks and assisting Oliver in software programming. This means to develop a framework in order to initialize and control the robot comfortable.
I'm studying mechanical engineering at ETH and focusing in my graduate program on robotics and autonomous systems.

Oliver (Teammember)

Hi there! My name is Oliver Baur and my job is connecting Martins and Andis work. Which means programming the software so that the trajetories of the stable walking gaits actually move the legs of our robot in the manner we want them to move.
I'm studying mechanical engineering at ETH Zurich with the focus on mecatronics an robotics.

Martin (Teammember)

I'm Martin Latta and responsible for controling tasks at the Lunar Robottics Challenge. I'm studying mechanical engineering at ETH Zurich, focussing on mecatronics an robotics in my undergraduate studies.
The main issues on my part will be to generat stable walking gaits (which can also mean crawling or other locomotion modes) an control them during the critical step phases, preventing the robot to tilt over.

Andreas (Teammember)

Hi, I'm Andreas Lauber. In this project, I work on the mechanical design and will take care of the manufacturing organization.
I'm an undergrad student in mechanical engineering with focus on robotics and mechatronics at the ETH Zurich. The main task I'm dealing with is to design an rigid body for the robot to ensure stable walking abilities.