The potential field method is widely used for autonomous mobile robot path planning due to its elegant mathematical analysis and simplicity. However, most researches have been focused on solving the motion planning problem in a stationary environment where both targets and obstacles are stationary. This paper proposes a new potential field method for motion planning of mobile robots in a dynamic environment where the target and the obstacles are moving. Firstly, the new potential function and the corresponding virtual force are defined. Then, the problem of local minima is discussed. Finally, extensive computer simulations and hardware experiments are carried out to demonstrate the effectiveness of the dynamic motion planning schemes based on the new potential field method.

Dynamic Motion Planning for Mobile Robots Using Potential Field Method

The paper first describes the problem of goals unreachable with obstacles nearby when using potential field methods for mobile robot path planning. Then, new repulsive potential functions are presented by taking the relative distance between the robot and the goal into consideration, which ensures that the goal position is the global minimum of the total potential.

New potential functions for mobile robot path planning

http://www1.cs.columbia.edu/~hgs/teaching/security/hw/keystroke.pdf

Keystroke dynamics as a biometric for authentication

In an effort to confront the challenges brought forward by the networking revolution of the past few years, we present improved techniques for authorized access to computer system resources and data. More than ever before, the Internet is changing computing as we know it. The possibilities of this global network seem limitless; unfortunately, with this global access comes increased chances of malicious attack and intrusion. Alternatives to traditional access control measures are in high demand. In what follows we present one such alternative: computer access via keystroke dynamics. A database of 42 profiles was constructed based on keystroke patterns gathered from various users performing structured and unstructured tasks. We study the performance of a system for recognition of these users, and present a toolkit for analyzing system performance under varying criteria.

Authentication via keystroke dynamics

An approach to securing access to computer systems is described. By performing real-time measurements of the time durations between the keystrokes when a password is entered and using pattern-recognition algorithms, three online recognition systems were devised and tested. Two types of passwords were considered: phrases and individual names. A fixed phrase was used in the identification system. Individual names were used as a password in the verification system and in the overall recognition system. All three systems were tested and evaluated. The identification system used 10 volunteers and gave an indecision error of 1.2%. The verification system used 26 volunteers and gave an error of 8.1% in rejecting valid users and an error of 2.8% in accepting invalid users. The overall recognition system used 32 volunteers and gave an error of 3.1% in rejecting valid users and an error of 0.5% in accepting invalid users. >

Computer-access security systems using keystroke dynamics

An application of fuzzy algorithms in a computer access security system

An important problem in robotics is to determine an obstacle avoidance control which transfers the system along a collision-free path among obstacles in the work space. Most algorithms which have been developed to solve this problem are based on a mapping of the given problem into a finite state space which always resulted in a problem which can be solved by a computer but have a high computational complexity.
Certain previously developed algorithms worked directly with continuous problem space and are called continuum algorithms. These algorithms were relatively unsophisticated when compared to the continuous algorithms.
This observation served as a motivation for the research reported here, in which it was sought to provide continuum algorithms with a more rigorous theoretical base. The main result of this work is the development of a real-valued function which is denoted by the symbol $\Omega$ and called Omega, which characterizes the proximal relationship of two non-point convex bodies. This function is different from similar functions reported previously in that it also provides useful information when the sets under consideration intersect.
In this thesis, the need for such a function is established, and certain computationally useful properties of the developed function are proven. These result are subsequently used in a path-planning algorithm based on the use of the $\Omega$ function and the Potential Function approach. Results of this algorithm are presented and compared with those of previously developed algorithms.

Robot path planning and obstacle avoidance by means of potential function method

Real-time robot path planning using the potential function method

This paper deals with the use of the Potential Field Approach as a means of collision avoidance and path planning for the "Generalized Mover's Problem" in the presence of obstacles. Although an important and fundamental problem, relatively little has been done using this approach over the last several years. It can also be seen that only a few path planning algorithms developed work directly with continuous state-spaces. The potential field approach was developed by Khatib in 1980. There is, however, considerable room for improvement and expansion of Khatib's algorithm. Khatib's potential functions were not defined for interaction between two general objects, but only for interaction between a certain subclass of objects and a point. Thus in this paper the following goal will be sought: * Extend Khatib's potential function method to the case of the interaction between two general objects, rather than just between a point and an object.

Bassam Hussien

Papers

An application of fuzzy algorithms in a computer access security system

Robot path planning and obstacle avoidance by means of potential function method

Real-time robot path planning using the potential function method

Path Planning And Collision Avoidance Among Objects By Means Of Potential Fields

Obstacle avoidance in path planning using intersection constraint search