AirArm

Year

2008

The idea

This arm module is based on the natural model of the grasshopper’s and lobster’s legs.

The objective

AirArm is an exoskeleton with fluidic muscles; it is able to catch drops of water.

Technical data

• Upper arm length: 38.9 cm
• Upper arm diameter: 12.3 cm
• Upper arm weight: 1022 g
• Forearm length: 31.1 cm
• Forearm diameter: 10.4 cm
• Forearm weight: 763 g
• Scope of movement: 75 cm
• Fluidic muscles: 12
• Pressure sensors: 3

The grasshopper as a model

Some species of grasshopper can jump with an acceleration a thousand times their own body weight by means of their flexor and extensor muscles. Based on this model, AirArm comprises an outer skeleton with pneumatic muscles in the interior.

The lobster as a model

The angularly offset joint axes of the lobster leg served as a further model. AirArm is thus designed as a three-part arm module with specially matched segment lengths and special rotation joints.

Kinematics

With its four-axis kinematics and twelve pneumatic muscles, AirArm can move flexibly and yieldingly within a hemispherical space. It emulates the movement pattern of a human’s pointing gesture.

Control

In view of its non-linear mechanics, the arm module is provided with intelligent control and regulation technology: once the target pressure curve for the pneumatic muscles is calculated, the real values at the valve outlet are compared against it. If the data are identical, no action is required; in case of deviation, the pressure curve is modified. AirArm operates quickly and reacts dynamically even to the smallest of changes. It is able to catch individual drops of water.

Material

AirArm