Search Results (2)

Remote center-of-motion mechanisms are essential in minimally invasive surgery because they allow surgical instruments or an endoscopic camera to pivot around a trocar entry point while eliminating lateral motion at the incision. This paper presents the design, kinematic modeling, prototype implementation and preliminary evaluation under laboratory conditions of a compact, spherical, remote center-of-motion robot for minimally invasive surgical orientation tasks. The proposed mechanism uses a spherical kinematic architecture actuated by a contra-rotating differential gearbox. This gearbox generates two coaxial output rotations of equal magnitude and opposite direction from a single input, mechanically synchronizing the opposed motion of the two base links and eliminating the need for cable-pulley transmission or dual electronically synchronized motors. A second actuator chain rotates the gearbox assembly around the base axis, thereby decoupling the extension–retraction motion from base-axis rotation. Forward and inverse kinematic formulations were derived for teleoperation of the robot using a 7 degrees of freedom haptic device and for remote center-of-motion orientation control using a 3-axis joystick. A proof-of-concept prototype was developed and integrated with a custom embedded controller, closed-loop motor control, a master-console interface and video feedback loop. The system was evaluated in a phantom-torso setup using a custom endoscopic camera, internal visual markers and an OptiTrack-based measurement of the remote center-of-motion accuracy. The qualitative experiment confirmed functional integration of the mechanical, electronic and software subsystems, while the optical-tracking measurement showed that the pivot constraint was maintained with a mean deviation of 1.69 mm and a root-mean-square deviation of 2.13 mm over the analyzed orientation sweep. The main limitations remain the 1:1 gearbox ratio, limited actuator torque, additively manufactured gearing and the absence of repeated-trial repeatability and full workspace characterization. Full article

The single HST (Hydro Static Transmission) mechanical differential transmission gearbox of crawler combine harvester is subjected to the impact of alternating loads in the field operation, resulting in its fatigue failure. The traditional durability fatigue test can improve the fault-free working time of machinery, but it is not suitable for agricultural machinery with time-varying load frequency bandwidth and stress amplitude. Therefore, in this paper, a fault diagnosis method based on order analysis was proposed considering the comprehensive influence of load amplitude and frequency on the fatigue life of gearbox. The location and the corresponding type of fault were found by comparing the spectral line peak changed before and after. Then, the test verification was carried out on the gearbox assembly fatigue test bench according to the compiled load spectrum. The results show that the analysis results of the fault diagnosis method based on order analysis were consistent with the unpacking inspection, which had reference significance for the research on the fault diagnosis method of the crawler combined harvester gearbox. Full article