ABSTRACT
Crawling movement as a motive mode seen in nature of some animals such as snakes possesses a specific syntactic and dynamic analysis. Serpentine robot designed by inspiration from nature and snake’s crawling motion, is regarded as a crawling robot. In this article, a serpentine robot with spiral motion model will be analyzed. The purpose of this analysis is to calculate the vertical and tangential forces along snake’s body and to determine the parameters affecting on these forces. The different types and functions of snake robots are listed. Biological snakes are pervasive across the planet; their diverse locomotion modes and Physiology make them supremely adapted for the wide variety of terrains, environments and climates that they inhabit. A snake-like device that could slide, glide and slither could open up many applications in exploration, hazardous environments inspection and medical interventions. One of the fundamental issues is understanding their locomotion. A wheel turns; the vehicle moves. A leg pushes; the vehicle moves. How a snake moves is not so evident. A worthwhile snake robot has the ability to wriggle into confined areas and traverse terrain that would pose problems for traditional wheeled or legged robots
INTRODUCTION
Biological snakes are pervasive across the planet; their diverse locomotion modes and Physiology make them supremely adapted for the wide variety of terrains, environments and climates that they inhabit. A snake-like device that could slide, glide and slither could open up many applications in exploration, hazardous environments, inspection and medical interventions.
One of the fundamental issues is understanding their locomotion. A wheel turns; the vehicle moves. A leg pushes; the vehicle moves. How a snake moves is not so evident. A worthwhile snake robot has the ability to wriggle into confined areas and traverse terrain that would pose problems for traditional wheeled or legged robots.. The design and implementation of a snake robot is the confluence of several technologies: actuation, form and structure, electronics, control, sensing, etcetera.
Why Serpentine Locomotion?
For centuries, people have created a menagerie of machines whose appearance and movement have mirrored animals to an astonishing degree. The general motivations for serpentine locomotors are environments where traditional machines are precluded due to size or shape. Example environments include tight spaces, long narrow interior traverses, and travel over loose materials and terrains. Wheels offer smooth and efficient locomotion but often require modifications to terrains for best use.
Integration is complicated, even intractable, if individual areas are not thought of in the whole.
FIG. design flowchart
Configuration and Design 1.4.0.1
The challenge of configuration is determining the form of a robot. The challenge of actuation is determining the technology that drives the mechanism. The questions are sometimes mundane but essential to answer: How long should segments be? What angle should they subtend? Are there actuation techniques that can provide smoother curves? Determining both the result and implications of each decision is a challenge.
Infrastructure and Electronics 1.4.0.2
Supplying and routing power and signals in complex robots is often underestimated as a design task. Serpentine robots must be compact and small to accrue the advantages shown in the previous section. Small size burdens the tasks of wire routing and actuation support.
Control and sensing 1.4.0.3
Finally, the greatest challenge: how to learn to control such a device? A larger issue is determining the process, method and framework to achieve this.
ADVANTAGES OF SERPENTINE ROBOTS
• Stability: Unless a serpentine robot purposefully slithers off a cliff, it can’t fall over. In contrast, stability is of great concern to wheeled and legged machines in rough terrain; they can fall over. Terrain contacts in vehicles form a constellation of points on the terrain; if the center of gravity moves beyond the bounds of the convex polygon formed by these points, it tips over. In a serpentine robot, the potential energy remains low in most situations; therefore there are few concerns for stability and no need for the support
polygons formed by wheel or leg contact points.
• Terrainability: Terrainability is the ability of a vehicle to traverse rough terrain. Terrain roughness is often measured by scale of features, power spectral density, distribution of obstacles such as rocks and geographic forms or even its fractal dimension A serpentine mechanism holds the promise of climbing heights many times its own girth; this feature can enable passage through terrain that would encumber or defeat similarly scaled wheeled and legged machines.
• Traction: Traction is the force that can be applied to propel a vehicle. Traction is usually limited to the product of the vehicle weight and the coefficient of friction. The distribution of the snake mass over such a large area, in comparison to mass equivalent legged or wheeled vehicles, results in forces that can be below the thresholds of the plastic deformation of the soil. In comparison, load concentration resulting from most wheels or leg designs results in soil work. Because of the large contact area, serpentine vehicles may result in little or no soil work. Limbless locomotion may prove superior in marginal or soft terrains where plowing and shearing actions restrict wheel mobility.
• Efficiency: Snakes achieve efficiencies and performance equivalent to biomechanisms of similar scale and mass. Reasons include reduced costs associated with less lifting of the center of gravity as compared to legged animals, elimination of the acceleration
or deceleration of limbs, and low cost for body support. The answer is that energy losses in snakes include greater frictional losses into the ground, lateral accelerations of the body that do not contribute to forward motion, and the cost of body
support for partial body elevations during movement.
• Size: Depending on the mechanism design, the small frontal area of snake mechanisms allows penetration of smaller cross-sectional areas than mass-equivalent legged or wheeled vehicles. If the volume of a snake, a cylindrical form, is kept the same and the diameter is reduced by half, the length becomes four times greater. Cross-sectional area for mechanisms of similar density and mass may result in very long vehicles.
• Redundancy: Candidate configurations for serpentine robots may employ many simple motion actuators in sequence. During operation, the loss of short segments would still permit mobility and maneuverability
