Measurement System for Animal’s Ground Reaction Forces and Preliminary Study of Kinematic Mechanics

Abstract

Locomotion is the basis of predation, escape, reproduction for animals. Geckos, spiders and insects run and climb with exceptional speed, strength and agility for their size, representing in many respects an ideal model system for the study of terrestrial locomotion. Biologists make comparative biology study with animals to develop a deeper understanding of the foundmental biomechanical design rules common to all legged organisms. Engineers look to animals’ locomotion for design principles to improve the performance of legged robots including wall-climbing robots and other complex systems. By measuring the ground reaction forces generated by animals when walking upright, climbing vertically or walking on an inverted surface, we can understand adhesion mechanism and locomotion dynamics.

Sticky animal’s kinematic mechanics measurement system was created to measure the ground reaction forces produced by animals in different legs at the same time. With this system and the high speed camera, the cooperative adhesive mechanics among all legs of insects when locomotion can be acquired. The sensor array of the system were composed of 16 3-dimensional sensors in smaller range on 4×4 pattern. A mechanical device was installed in sensors array to achieve over-load protection. National Instruments Company’s SCXI signal conditioning modules were used in this system to compose 48 channels signal amplification, data acquisition and processing device. The software of data acquisition and analysis was compiled in LabVIEW environment.

The ground reaction forces produced by single leg of animals were measured by single force sensor at first. After these experiments,we will use measurement system with sensors array to measure the measure the ground reaction forces produced by animals in different legs at the same time. A 3-dimensional force sensor was used to measure the ground reaction forces generated by geckos when walking upright and climbing vertically. By measuring the different target surface reaction force, we understood gecko’s adhesion mechanism and locomotion. The study sheds light on the study of animal’s locomotion and the design of bio-inspired robot. Legs of stinkbug Erthesina fullo performance during walking was examined with a model. A 3 dimensional force sensor in smaller range was used to measure the ground reaction forces created by
individual legs of the stinkbug when moving on the level and vertical surfaces. The legs of insect generate adhesive forces to avoid overturning when climbing vertically.

The force of free swimming water striders was measured about 0.3-0.4 mN/cm. The error calculated by comparing force and geometrical derived data, was estimated as 13%. Females in average were stronger than males, however the ratio force / weight was not significantly different. Compared to other lighter species' data available in literature, water strider Aguarium paludum seems to be stronger, but the ratio force / weight is actually lower.