SIGMO is a

humanoid robot A humanoid robot is a robot resembling the human body in shape. The design may be for functional purposes, such as interacting with human tools and environments, for experimental purposes, such as the study of bipedal locomotion, or for other pu ...

designed to demonstrate the applications of

passive dynamics Passive dynamics refers to the dynamical behavior of actuators, robots, or organisms when not drawing energy from a supply (e.g., batteries, fuel, ATP). Depending on the application, considering or altering the passive dynamics of a powered syste ...

technologies. SIGMO stands for Synthetic, IntelliGent, MObility, and was developed by a team of high school students to demonstrate the capabilities of passive-dynamic actuation techniques. The technology used to enable SIGMO to walk is being applied to advanced prosthetic devices. Current prosthetic devices are nearing the limitations of the available technologies and require advancements such as customized motion, lower cost, and the development of light-weight materials. Existing humanoid robot systems such as ASIMO and QRIO use many motors to achieve

locomotion Locomotion means the act or ability of something to transport or move itself from place to place. Locomotion may refer to: Motion * Motion (physics) * Robot locomotion, of man-made devices By environment * Aquatic locomotion * Flight * Locomo ...

. These motors reduce efficiency and add unnecessary weight and cost to the robot. SIGMO attempts to alleviate these symptoms by providing a system which uses no motors for locomotion, instead employing passive-dynamic technology. Passive-dynamic systems cite low power consumption, high durability, and low cost. The design is based on the skeletal structure of the human body, consisting of two legs with hip, knee, and ankle joints, each representing 1

degree of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...

(DOF). Movement is accomplished with the aid of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

(walking down a slope) or by minimal actuation to enable the machine to walk on level ground. SIGMO was developed using proven methods of gravity-driven passive dynamic bipeds. Small actuators were added to the legs to provide walking capability on level ground. This method of locomotion is very energy efficient because it uses no motors for walking. The omission of motors also cites a drastic weight reduction, further enhancing the locomotive efficiency. This also frees up room inside the torso for the circuitry that controls SIGMO's movements, unlike other robots that require a "backpack" like attachment. SIGMO has an upper torso which mimics the movements of actual humans. The arms are motorized with small

servo motors A servomotor (or servo motor) is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also ...

which enable SIGMO to manipulate objects within its grasp. The main chassis is fabricated of

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

sheet metal, which has a high strength and light weight. The knee sockets are fabricated out of steel and

. While the steel weighs more than the

, this helps to transfer the weight load from the torso (contains heavy

servo Servo may refer to: Mechanisms * Servomechanism, or servo, a device used to provide control of a desired operation through the use of feedback ** AI servo, an autofocus mode ** Electrohydraulic servo valve, an electrically operated valve that c ...

components) to the legs and feet which rest on the ground. An updated model of SIGMO, currently in the research and development stage, will incorporate more precise control over limb movement and directional stability. To add more functionality SIGMO will have more motors, but use each more efficiently than previous designs. Knowledge of actuation techniques gained from previous experiments will be applied to reduce complexity and maintain an efficient method of locomotion. A framework is in development to allow multiple configurations of the robot to lower production costs over time and increase flexibility of design during testing. The robust internal skeleton will be modifiable to serve as a platform for future designs. Intelligent maneuvering will also be tested with the new prototype to develop efficient

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

s and control models for both simple and complex environments.

External links

SIGMO Robotic Developments

Cornell Research Lab
{{DEFAULTSORT:Sigmo Bipedal humanoid robots 2005 robots Robots of the United States