Master Document

Automating the Bedroom Window

Concepts:

• Gilles' working concept as of 2-13-21 (follow link)
• Using a linear actuator - see below
• hybrid concept

Using a linear actuator:

This is an attempt to use a linear actuator (self-contained unit) to solve the problem. While these can be expensive, the tradeoff will potentially be in time spent engineering, proving, and troubleshooting a custom solution. Therefore, this can also be thought of as an "easy-button" to solve the problem, which is not inherently an easy problem.

Considerations:

Drive type:

• • Ball-screws vs. lead screws
    • Ball screws  ~90% efficient - > can backdrive
    • lead screws ~ 40% efficient - > usually can't backdrive do to inefficiencies
    • Ball screws are more precise and expensive
    • lead screws sometimes use a plastic carriage rather than a steel
  • Belt drive seems more oriented towards horizontal applications, whereas ours is vertical
  • Ball screw is most likely the most appropriate for our application

Lubrication:

• • Screw drives and linear bearings usually require periodic lubrication
  • Lubricate using grease rather than oil for vertical applications
  • Some ball screws will advertise that they are maintenance and lubrication free (internally lubricated)
    • These products have a finite lifespan. Once the internal lubrication runs out, the product may fail.
    • Depending on our intended # of cycles and lifetime, such a product may still be appropriate.
  • Some lead screws advertise lubrication free
    • plastic on metal
    • Likely not suitable for our heavy-lift application

Linear guides:

• • will help align the window pane and resist the overhanging moment loads
  • therefore, these must be robust due to the high pitch and yaw moments (366 Nm)
  • a counterweighted system would be unable to counterbalance these moments, so we need robust guide rails to do so.

Travel life:

• • Travel life seems to be an important factor:
  • Assumptions for travel life. Raised/lowered once per day, everyday for 100 years
  • 605 mm of travel (1300 mm per open/close)
  • 48 KM traveled in 100 years worst case - on the very low side for these sorts of applications

Electronic Brake:

• • Some systems allow electronic emergency brakes. These are electric open (24 V) - spring close
  • In other words, these are energized during actuation of the window, and normally stay closed
  • This can alleviate the need for a counterweight and/or other safety systems

Selecting a linear actuator: