Sliding Mode/ Time Proportioning Control Algorithms

I need to control an electric heater with a SSR and to cycle it between two temperature setpoints. I tried simple Bang-Bang control but, as usual, it isn't as stable as I would like/ need.

I searched on the above two topics and they have been discussed at length on this forum in the past. The links that looked the most promising to provide additional info came up with 404s.

How does one calculate how much on time is required over a given period, say 10 seconds, to allow the heater to be cycled?

Is there a website that has general info on this topic? Is there a textbook you could recommend on this subject that has this type of info?

I'll be programming it in a function block at this time but would like the theory/ algorithm so I can reapply it in the future if another programming platform/ language is used.

TIA

Lots of information

I moved a lot of my files to our ftp site.

ftp://ftp.deltacompsys.com/public

I hate to reference specific files because I add or delta files from time to time and I don't want to add to the number of broken links.

Go to the SMC directory.

In general the switching rate must be much higher than the fastest time constant in the system. 10 second updates is probably not fast enough. I like to use 1 second updates for temperature as it is move than fast enough and the calculations are easier.

I do not know if this will help BUT Allen Bradley had a nice Time Proportioning Control example in their Instruction set manual

go here http://literature.rockwellautomation.com/idc/groups/public/documents/webassets/browse_category.hcst

AB Litature libray and search Publication Number 1747-RM001D-EN-P

SLC 500 Instruction Set Page 9-31

GO JETS

Thanks for the responses, Peter's ftp site is what I was trying to locate. I had seen this item a while back and was hoping they were still available.