Magnetic Field Synthesis of Electromagnetic Navigation Systems in Current Limits

Electromagnetic navigation systems (eMNS) for medical applications, such as cardiovascular diseases, employ stationary coils and soft magnetic cores. Electrical currents in the coils synthesize magnetic fields to wirelessly control millimeter-sized microrobots, such as magnetic guidewires. Previous control methods of calculating the current references for the eMNS focus on either low conduction loss with pseudoinverse or wide magnetic-feasible workspace (MFW) with a linear combination of pseudoinverse and minimum infinity-norm. However, with the merits of both wide MFW and low conduction loss, this article proposes an iterative control method that modifies the initial pseudoinverse iteratively, while ensuring that the current limits of the coils are not exceeded. A detailed description of the control method, accompanied by a comprehensive analysis, is provided. The prototype of eMNS with eight coils is used for the experimental verification. It is shown that, in the current limits, MFW is increased by more than 45% compared with the pseudoinverse method, and the conduction loss is reduced by more than 2 kW compared with the linear combination method.