Under the guidance of high-resolution Magnetic Resonance Imaging (MRI), robotic devices offer a great advantage for prostate intervention. This paper presents an MR-safe robot, where a needle is attached to the needle guide to obtain prostate biopsies during surgeries. The robot is powered by three actuators, two of them are customized to function as a work plane that allows the needle to move horizontally and vertically, and the third actuator controls the rotation of the work plane, allowing the needle to be inserted into the prostate from different directions. All the actuators are pneumatically actuated to allow them to work in a Magnetic Resonance (MR) environment. The kinematics and mechanism of the robot are analyzed. A user interface developed using LabView is created to calculate the target position and generate a control signal for the valves. In the open-air test, the needle can reach the target with an accuracy of 1.3 mm. The signal-to-noise ratio (SNR) variation was measured below 5% under a 3T MR scanner.

Magnetic resonance (MR) imaging has been widely used in the diagnostics and treatment of soft tissues due to its ability to acquire high-resolution images with outstanding contrast. Therefore, MR-guided therapy and its supporting equipment, including MR-conditional sensors and actuators, have been developed rapidly. In this article, a nonmagnetic pneumatic stepper motor was developed. The working principle was analyzed, and the theoretical static output torque was expressed mathematically. The driven part of the proposed design is a polygon rotor derived from the Wankel engine. Besides, the outline of the inner wall of the housing was investigated. Experiments were conducted with the motor functioning at different speeds under different air pressures; by controlling the air in each chamber sequentially, the rotor can rotate continuously in dual directions with a torque of up to 38 mN·m and a maximum speed of 400 r/min. The MR test showed that no image artifact was found.

Analytical models for energy dissipation and temperature rise in a silicone oil torsional damper are developed to investigate its thermal characteristics. An experimental test platform is established to measure the surface temperature rise in the damper, and experimental results are used to validate the proposed analytical model. Good agreement between the analytical predictions and experimental measurements demonstrates the reliability of the analytical model. The results show that the maximum temperature rise in the damper is influenced not only by the engine speed but also by the output torque. Increasing the thickness of the silicone oil layer leads to higher total energy dissipation and temperature rise, whereas increasing the kinematic viscosity of the silicone oil reduces both energy dissipation and temperature rise. In addition, decreasing either the width or the radius of the inertia ring effectively lowers the surface temperature rise in the damper. Under steady-state operating conditions, the surface temperature can be considered as the temperature of the silicone oil. It is also found that the peak temperature rise is exhibited at 2300 rpm (revolutions per minute) for the silicon oil damper used in the paper. These findings provide theoretical insight into the thermal characteristics of silicone oil dampers and offer useful guidance for designing structures with lower temperature rise.

This paper studies the relationship between the various vibration modes of the magnetoelectric composite structure and the biased magnetic field. Matlab is used to calculate three nonlinear parameters of Terfenol-D, then the nonlinear relation between the characteristic frequencies of the four vibration modes of the magnetoelectric composite structure and the external magnetic field is obtained by finite element method (FEM). Finally, the magnetoelectric composite structure specimen is prepared, and the correctness of the finite element method is verified by the experimental method. In addition, the vibration frequency of the magnetoelectric composite structure specimen in the magnetic field is measured by the laser vibrometer. The experimental data agree well with the results of FEM, which provides a new method for magnetic field measure.