A circulation assist system measures impeller displacement for use in estimating a blood flow rate related parameter. A circulation assist system includes a blood pump and a controller. The blood pump includes an impeller magnetically supported within a blood flow channel. The blood pump includes one or more sensors configured to generate output indicative of displacement of the impeller along the blood flow channel induced by a blood-flow induced thrust load applied to the impeller. The controller is configured to process the output generated by the one or more sensors to determine the displacement of the impeller along the blood flow channel. The controller is configured to process the determined displacement of the impeller to estimate at least one of the thrust load applied to the impeller, a pressure differential of the blood impelled through the blood flow channel, and a flow rate of blood pumped by the blood pump.
