Feedback control of an encountered-type haptic interface using MR fluid and servomotors for displaying cutting and restoring force of soft tissue

Most haptic devices used in surgical simulators cannot display the force of multiple types of surgical instruments. To achieve this, an encountered-type haptic interface using magnetorheological (MR) fluid has been developed. This study aims to propose a scheme for displaying cutting force and elastic restoring force of soft biological tissue by the encountered-type haptic interface. The cutting force and elastic restoring force of soft biological tissue by a knife consist of two-directional forces: in the cutting direction and perpendicular to the cutting direction. Previous research has mainly focused on the cutting direction. Therefore, a scheme for displaying the two-directional forces is discussed in this paper. The proposed scheme controls the force perpendicular to the cutting direction by using servomotors that move a container of MR fluid. While displaying the force history when cutting a porcine liver, the error of the reference force in the direction perpendicular to the cutting direction was reduced without affecting the force in the cutting direction.