Snake Robot


In the past two decades it is estimated that disasters are responsible for about 3 million deaths worldwide, 800million people adversely affected, and property damage exceeding US$50 billion. The recent earthquake in Turkey in November of 1999 left 700 dead and 5000 injured. Many of these deaths were from structural collapse as buildings fell down onto people. Urban Search and Rescue involves the location, rescue (extrication), and initial medical stabilization of victims trapped in confined spaces. Voids formed when a buildings collapse is one instance of a confined space. Urban Search and Rescue may be needed for a variety of situations, including earthquakes, hurricanes, tornadoes floods, fires, terrorist activities, and hazardous materials (hazmat) accidents. Currently, a typical search and rescue team is composed of about ten people, including canine handlers and dogs, a paramedic, a structural engineer, and various specialists in handling special equipment to find and extract a victim. Current state of the art search equipment includes search cameras and listening devices. Search cameras are usually video cameras mounted on some device like a pole that can be inserted into gaps and holes to look for signs of people. Often a hole is bored into the obstructing walls if a void is suspected to exist on the other side. Thermal imaging is also used. This is especially useful in finding warm bodies that have been coated with dust and debris effectively camouflaging the victim. The listening devices are highly sensitive microphones that can listen for a person who may be moving or attempting to respond to rescuers calls. This hole process can take many hours to search one building. If a person is found extrication can take even longer. This paper presents the developments of a modular robot system towards USAR applications as well as the issues that would need to be addressed in order to make such a system practical.


Sensor-Based Online Path Planning

This section presents multisensor-based online path planning of a serpentine robot in the unstructured, changing environment of earthquake rubble during the search of living bodies. The robot presented in this section is composed of six identical segments joined together through a two-way, two degrees-of- freedom (DOF) joint enabling yaw and pitch rotation (Fig.), while our prototype mechanism (to be discussed later in this article) is made of ten joints with 1 DOF each.

Configuration of each segment

The robot configuration of this section results in 12 controllable DOF. An ultrasound sensor, used for detecting the obstacles, and a thermal camera are located in the first segment (head). The camera is in a dust free, anti shock casting and operates intermittently when needed

Modified distance transform

The modified distance transform (MDT) is the original distance transform method modified for snake robot such that the goal cell is turned in to a valley of zero values within which the serpentine robot can nest. Other modifications are also made to render the method on line

" Distance transform is first computed for the line of sight directed towards the intermediate goal, without taking into account sensorial data about obstacles and free space. This is the goal-oriented planning.
" The obstacle cells are superimposed on the cellular workspace. This modification to the original distance transform integrates IR data that represent the obstacles are assigned high values