AbstractRespiratory assistance is of significant importance for achieving pulmonary rehabilitation in individuals with weakened respiratory muscles. Soft actuators have great potential in rehabilitation application; yet, there is little research on soft respiratory rehabilitation robots. This article presents a novel bidirectional asymmetric accordion-type soft robot capable of generating chest expansion and contraction actions, designed for respiratory assistance training in patients with respiratory muscle weakness. The robot consists of two bidirectional asymmetric accordion-type pneumatic actuators (APA), each composed of a primary accordion-type pneumatic actuator (PAPA) and a subordinate accordion-type pneumatic actuator (SAPA), capable of providing torque to the human body to facilitate auxiliary expansion and contraction of the patient’s chest. A kinematic model is developed to couple the angular movements of the human arm with the actuator by analyzing their angular relationships. By modeling the airbags of actuators as compressed spheres and simplifying the contact areas, the effective angle can be calculated at the specified pressure and output torque, thereby selecting the optimal geometric parameters of PAPA and SAPA to ensure that the desired angle is achieved for lifting the arm. Experimental validation confirmed the accuracy of the proposed kinematic coupled model and output torque of PAPA. The robot’s efficacy in respiratory training was assessed by comparing volume flowrate (VFR) and moving air volume (MAV) between ten healthy participants with and without robot assistance. The experimental results show that the average improvement rates of exhalation VFR, inhalation VFR, and MAV of the 10 participants are 154%, 148%, and 155%, which demonstrated the robot’s capability to enhance respiratory function.

AbstractCam, a mechanism usually used to transform a rotary motion into the desired output motion, has been commonly used in the modern industry. In practice, various practical methods have been discussed to analyze and synthesize the cam mechanism. However, the mobility of the cam mechanism is seldom mathematically addressed. This article mathematically discusses the necessary and sufficient design conditions for four kinds of overconstrained cam mechanisms (the one with a translating flat-faced follower, a translating roller follower, an oscillating flat-faced follower, and an oscillating roller follower) to be mobile. For the first two overconstrained cam mechanisms, the relation between the design conditions and the mobility of the cam mechanism is derived by proving that the identical cam contour can be enveloped by the top and bottom follower faces. For the third overconstrained cam mechanism, the relation is derived by transforming the cam contour into a geometric layout associated with an orthoptic curve. For the fourth overconstrained cam mechanism, it is shown that the cam mechanism cannot be theoretically designed due to the variable length of the follower's arm, which does not obey the rigid body assumption. In conclusion, by means of these geometric methods, the first three kinds of cam mechanisms are proved to be mobile if and only if they satisfy the design conditions, and the last cam mechanism is proved to be theoretically infeasible.

AbstractThis article presents a comprehensive performance analysis of the step-climbing and passive rolling modes of a hexagon rolling mechanism with single-degree-of-freedom, based on its structural characteristics and the constraints of centroid stability. First, a step-climbing model, incorporating motion parameters and support distance parameters, is established by leveraging the symmetrical posture movement characteristics of the hexagon rolling mechanism. Building on this foundation, the impact of each parameter on the mechanism's step-climbing ability is thoroughly analyzed, and the maximum height achievable during step climbing is also examined. Subsequently, the existence and sufficient conditions for the hexagon rolling mechanism to achieve passive rolling are analyzed using the centroid fluctuation curve and its slope curves. The analysis results indicate that, due to its unique coupling structure design, the hexagon rolling mechanism possesses a passive rolling capability that is not available in conventional planar linkage mechanisms. Finally, the correctness of the theoretical model is validated through both simulation and prototype experiments.