Sunday, July 6, 2008

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.

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