Adaptive control of suspension force in a novel bearingless motor for a miniature axial flow blood pump

In this paper, an adaptive sliding mode controller (ASMC) is designed and analyzed for the suspension force control of a novel bearingless permanent magnet synchronous motor (BPMSM) for a miniaturized axial flow blood pump. Linear Hall Effect sensors are employed for measuring the rotor radial position and angular position. Two separate permanent magnets are utilized in the rotor for measuring radial position and to generate the bearing forces and motor torque, respectively. Therefore, the overall system has strong magnetic flux coupling and nonlinearity. A computational fluid dynamics (CFD) study is done in order to improve the design of the novel bearingless pump. An adaptive observer based on the radial basis function (RBF) approximation is constructed for the suspension force system in the radial direction. By utilizing this observer, an ASMC controller is constructed and analyzed for the system. The designed RBF observer is able to estimate the system states in the presence of uncertainties and nonlinearities. Stability analyses for the proposed observer and closed-loop control system are given. The performance of the ASMC controller is compared with the conventional control technique as well. Experimental tests are conducted at numerous operating conditions for validating the effectiveness of the proposed control approach.