Particle swarm optimisation

[Mke]

Main Question or Discussion Point

Hello everyone,


I have a short question about the PSO since I am a new comer to this field. how can we "add" position with velocity in the simple PSO algorithm, when they are of different units?

 

[jedishrfu]

Welcome to PF!

Can you elaborate more on your question?

What do you mean by units?

What do you mean by "add" position to velocity?

Is the posititon in inches and feet (ie english units) but the velocity is in meters/sec (metric units) ?

 

[Mke]

Hello thank you for your reply.
When the velocity is determined in the PSo algorithm, one needs to add the weighted velocity to the difference between the ( current positions and the best experience of that position ) . The former is velocity which is normally measured in different units than the position. In PSO it's not common to include units for the position and velocity that is what got me confused.

 

[jedishrfu]

What units?

 

[Mke]

the units of velocity and position in the PSo are normally specified but they are still added together.

 

[jedishrfu]

What are the units for position?

What are the units for velocity?

 

[Mke]

they are not normally specified in the equations that produce the PSO. However, this is not important since regardless of the units, we are adding two different components that have different units. its like adding Kg and Km

 

[jedishrfu]

The best I can say here is that you compute the new position by using a velocity vector in say m/s times a small time increment in seconds to a change in position in meters:

NewPosition_meters = OldPosition_meters + Velocity_meters/sec * delta-time_seconds

 

[Mke]

Thank you but where does this delta-time come in the original equation that produces the new NewPosition which is merely : NewPositionmeters = OldPositionmeters + Velocitymeters/sec . Could you please further explain this ?

Also, how the delta-time is normally represented when the PSO algorithm is coded?

 

[jedishrfu]

The delta time is implied in your equation to be 1 second.