Combining Position and Velocity in PSO: How to Handle Different Units?

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Discussion Overview

The discussion revolves around the integration of position and velocity in the Particle Swarm Optimization (PSO) algorithm, particularly focusing on the challenges posed by differing units of measurement for these quantities. Participants explore how to conceptually and mathematically combine these components within the algorithm.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how to "add" position and velocity when they are measured in different units, indicating confusion about the integration process in PSO.
  • Another participant seeks clarification on what is meant by "units" and the specifics of the position and velocity being discussed.
  • A participant notes that while the units for position and velocity are not typically specified in PSO equations, they still need to be combined, likening it to adding kilograms and kilometers.
  • One suggestion involves calculating the new position by multiplying the velocity (in meters/second) by a small time increment, indicating a method to reconcile the units.
  • A later reply implies that the delta time in the position update equation is assumed to be 1 second, although this assumption is not universally accepted.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and implications of unit specifications in PSO. There is no consensus on how to handle the addition of position and velocity when they are in different units, and the discussion remains unresolved.

Contextual Notes

Limitations include the lack of explicit unit definitions in the PSO equations and the assumption regarding delta time, which may not be universally applicable across different implementations of the algorithm.

Mke
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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?
 
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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) ?
 
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.
 
the units of velocity and position in the PSo are normally specified but they are still added together.
 
What are the units for position?

What are the units for velocity?
 
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
 
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:

NewPositionmeters = OldPositionmeters + Velocitymeters/sec * delta-timeseconds
 
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?
 
  • #10
The delta time is implied in your equation to be 1 second.
 

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