Flasher, which has been used in space engineering, is a class of origami patterns. After modifying and introducing cuts for the flasher pattern, we add nonzero thickness to the flasher and taper its panels. We find that, if appropriately driven, the modified flasher can be used as the deployable mechanism, and even envelop the curved surface in its unfolded configuration. We establish a geometric model and a kinematic model for the mechanism. Then we propose a designing approach including folding design and driving method. The folding design, which ensures that the mechanism can be folded in the folded configuration, is based on geometric constraints. The driving method, which enables the multi-degree-of-freedom (DOF) mechanism to deploy in sequence with only one actuator, is based on underactuation. A prototype is built to validate this approach.

Background Continuous curvilinear capsulorhexis (CCC) requires surgeons to manipulate fragile eye tissue at the microscale. The limited perceptual accuracy of surgeons makes it difficult to precisely position the forceps. Robot technology provides a feasible way to improve the performance of CCC. Methods To provide real‐time and high‐precision forceps position feedback to the robot, and extract the expert's operation trajectory for robotic autonomous or assisted capsulorhexis, this paper proposes a forceps tracking method based on Kalman filters to precisely position the forceps. By fusing the inertial sensor data and the visual observation data, the proposed method can obtain forceps depth information and decrease cumulative errors in the inertial sensor data. Results Experimental validation on an eye phantom is performed to verify the effectiveness of the proposed forceps tracking method. The experimental results show that the proposed method can track the forceps tip at an average processing speed of 62.8 frames per second, and locate the forceps tip with an acceptable accuracy (within 25 μm). Then, we use the proposed method to capture the operation trajectory of an expert for robot preoperative trajectory planning. Conclusions The evaluation experiments indicate that the proposed method can accurately locate the tool tip, and efficiently extract the expert's operation trajectory.

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Abstract. The remote center of motion (RCM) mechanism is an important part of a minimally invasive surgery (MIS) robot. As a practical type of RCM mechanisms, 2R1T RCM mechanisms are synthesized in this paper using a modified screw theory method. Differing from the conventional screw theory method, the modified method brings forward the assessment of different wrench systems, and proposes several general subchains to satisfy each geometrical condition of the wrench system, which can ensure the motion continuity to a great degree. First, the motion pattern and the twist system of 2R1T RCM mechanisms are presented. According to the reciprocal rules of screw theory, three corresponding wrench systems, along with the geometrical conditions for them, are enumerated. After assessing these wrench systems by the comparison of their geometrical conditions, the optimum wrench system is selected for synthesis, and then it is decomposed into sub-wrench-systems. To satisfy each condition of the subwrench-systems, several general subchains are proposed, and consequently some preferred general chains are constructed by the serial assembly of the corresponding subchains. These general chains are applied to the leg synthesis. Finally, practical examples of 2R1T RCM mechanisms are constructed by assembling the legs.

The radial folding ratio of single-vertex multicrease rigid origami, from the folded configuration to the unfolded configuration, is satisfactory. In this study, we apply two approaches to add nonzero thickness for this kind of origami and identify different geometrical characteristics. Then, the model of the secondary folding origami, which can help to further decrease the folding ratio, is constructed. We apply the method of constraining the edges of the panels on prescribed planes to geometrically obtain the kinematic model. Based on the kinematic model and the screw theory, the nonzero thickness origami is transformed into the deployable mechanism with one degree-of-freedom (1DOF). Other similar mechanisms can be derived based on this basic configuration. The computer-aided design examples are presented to indicate the feasibility.