An insulin infusion device includes a processor architecture, and a memory element that stores executable instructions to perform a method of controlling delivery of insulin to a user. The method operates the device in a closed-loop mode to deliver insulin, obtains patient-specific parameters for a current time sample, and estimates a plasma insulin value and a blood glucose value for the user based on at least some of the patient-specific parameters. The estimating is also based on a previously estimated plasma insulin value obtained for a previous time sample, and a previously estimated blood glucose value obtained for the previous time sample. A predicted sensor glucose value is generated for the current time sample, and the closed-loop mode or a safe basal mode is selected for controlling operation of the insulin infusion device in accordance with the selected mode.
