Design of a vibration damping robot and force evaluation in intraoperative robotic-assisted femoral shaft repair using a modified soft damper.

BACKGROUND: Closed intra-medullary nailing fixation is a method for treating fractured femurs with minimal invasiveness. However, this method lacks safety and precision. To avert prevailing problems such as extended cracks in the already broken bone, the design of a vibration damping robot and force evaluation system is essential. METHODS: This paper presents a sensor-based clamping robot system embedded with a regulated pressurised air balloon. Drilling forces were monitored by a force sensor attached to the end robot effector, while the reduced vibration result was measured by a non-contact laser displacement sensor. A 2 degree-of-freedom (2DOF) model was developed. RESULTS: Force and vibration data were obtained using a data acquisition module (EMS 309) and analysed using MATLAB software (Version R2015b). The results obtained show that both the frequencies and amplitudes of the vibration is reduced at 6 bar with effector's spindle speed of 1500 rpm. CONCLUSIONS: This proposed concept shows that drilling force and vibration can be reduced simultaneously using a robot effector coupled with a damper.

Comparative Analysis of Cutting Forces, Torques, and Vibration in Drilling of Bovine, Porcine, and Artificial Femur Bone with Considerations for Robot Effector Stiffness.

Bone drilling is known as one of the most sensitive milling processes in biomedical engineering field. Fracture behavior of this cortical bone during drilling has attracted the attention of many researchers; however, there are still impending concerns such as necrosis, tool breakage, and microcracks due to high cutting forces, torques, and high vibration while drilling. This paper presents a comparative analysis of the cutting forces, torques, and vibration resulted on different bone samples (bovine, porcine, and artificial femur) using a 6dof Robot arm effector with considerations of its stiffness effects. Experiments were conducted on two spindle speeds of 1000 and 1500 rpm with a drill bit diameter of 2.5 mm and 6 mm depth of cut. The results obtained from the specimens were processed and analyzed using MATLAB R2015b and Visio 2000 software; these results were then compared with a prior test using manual and conventional drilling methods. The results obtained show that there is a significant drop in the average values of maximum drilling force for all the bone specimens when the spindle speed changes from 1000 rev/min to 1500 rev/min, with a drop from (20.07 to 12.34 N), approximately 23.85% for bovine, (11.25 to 8.14 N) with 16.03% for porcine, and (5.62 to 3.86 N) with 33.99% for artificial femur. The maximum average values of torque also decrease from 41.2 to 24.2 N·mm (bovine), 37.0 to 21.6 N·mm (porcine), and 13.6 to 6.7 N·mm (artificial femur), respectively. At an increase in the spindle speed, the vibration amplitude on all the bone samples also increases considerably. The variation in drilling force, torque, and vibration in our result also confirm that the stiffness of the robot effector joint has negative effect on the bone precision during drilling process.