Initial results in the adaptive control of ultrafiltration in hemodialysis

This paper presents a simplified transfer function model of ultrafiltration in hemodialysis, i.e., the process of removing excess water from the blood via a tubular filtering membrane. The excess water diffuses into a dialysate whose flow rate is controlled by a variable displacement pump whose displacement angle is governed by a PID controller. The parameters of the PID controller are adaptively tuned to a prescribed 2nd order (critically damped) response based on a least squares estimate of two critical modeling parameters that depend on the filtering membrane characteristics over the course of the dialysis. Initial simulation studies have indicated very successful results.