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Adaptive Robotics COM2110 Autumn Semester 2008 Lecturer: Amanda Sharkey. Researchers at Georgia Tech have built a biologically inspired robot to perform actions of service dogs Users issue verbal commands to robot, and indicate object with laser pointer.
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Autumn Semester 2008Lecturer: Amanda Sharkey
1. Identify the main characteristics of Behaviour-based robotics, and contrast the approach to that of “Good old-fashioned AI”.
2. To what extent did Grey Walter’s robots, Elsie and Elmer, differ from robots that preceded, or followed them.
3. Explain how the concepts of “emergence” and “embodiment” are related to recent developments in robotics and artificial intelligence.
Essay – Try to structure it with introduction, body and conclusion. Plan out an argument, like pseudo-code.
- in the text, either numerical , or by name, Cao et al (1997)
- In a Reference section at the end
 Cao, Fukunaga and Kahn (1997) Cooperative mobile robotics: antecedents and directions. Autonomous Robots, 4,1, 7-27.
Gordon, D. (1999) Ants at work: How an insect society is organised. W.W.Norton and Co.,London.
Sharkey, A.J.C. (1800) How to cite references, cited in Gordon, D. (1999) Ants at work: How an insect society is organised. W.W. Norton and Co. London.
Light sensor inputs
Fixed weights between collision layer and motor actions.
When collision occurs, and distance sensor active, Hebbian learning used to strengthen the weight between the two.
After learning – activating the distance sensor will result in the collision detector being activated.
The robot will learn to avoid objects.
New population created by selective reproduction.
Offspring are randomly paired, crossed over and mutated
One point crossover – for a pair of chromosomes select a random point to crossover material between two individuals.
Yao, X. (1999) Evolving artificial neural networks. Proceedings of the IEE 87, 9, 1423-1447
Possible to evolve:
Δv is the absolute value of the algebraic difference between the signed speed values of the wheels
i is the normalised activation value of the infrared sensor with the highest value
First component V is computed by summing the rotation speeds of the 2 wheels (direction of rotation given by sign of read value, and speed by its absolute value).
Second component encourages 2 wheels to rotate in same direction. The higher the difference in rotation the closer
will be to 1
e.g. if the left wheel rotates backwards at speed –0.4, and the right wheel rotates forward at speed 0.5
will be 0.9
The square root gives stronger weight to smaller differences. Since component is subtracted from 1, it is maximised by robots whose wheels move in the same direction, regardless of speed and overall direction.
Proximity sensors on Khepera emit a beam of infrared light – and measure quantity of reflected infrared light.
Closer a robot is to an object, the higher the measured value.
Value of i of most active sensor provides a measure of how close nearest object is.
Value subtracted from 1, so this component selects robots that stay away from objects.
Combined result of 3 components: selecting robots that move as straight as possible while avoiding obstacles in path.
Fixed network architecture
Weights between 8 proximity sensors and 2 motor units (also bias unit)
Recurrent connections at output layer
Synaptic connections (weights) encoded as floating point numbers on chromosome
Robots evolved to move onto target sites in pairsDeveloped signals: a) lone robot outside target b) single robot in target area c) robot in target with another robot d) robot approaching target, interacting with robot inside.
e.g.robot in target area hearing signal c would exit
e.g. robot outside target hearing b, would approach target and signal d.