Continuum hyper-redundant manipulators (CHRMs) have been widely applied in aerospace, medical or other fields to complete tasks in narrow and multi-obstacles environments with its unique structural advantages. Due to the redundancy, the inverse kinematics of CHRMs is rather complex and the trajectory planning has always been the focal and challenging point in the research of CHRMs. To tackle this issue, the present study proposes an overall configuration planning method of CHRMs based on the improved artificial potential field (APF) method. The method avoids the complicated inverse kinematics and vastly reduces the computational complexity. First, a virtual guiding pipeline (VGP) with no obstacles inside is constructed based on a known target configuration and the minimum safe distance. The movement of the CHRM is restricted to the pipe by the APF method. Then, we propose a method to construct a guided potential field in the VGP to solve the local minimum problem of the traditional artificial potential field method. Further, to address the issue of contradictory forces in the overall configuration planning, the maximum-work planning strategy is proposed. Finally, simulations are conducted and the results demonstrate the high performance of the method in terms of planning efficiency, environmental adaptability.

Continuum space manipulators have wide application prospect in the complex space environment with small space. Efficient and accurate static models are very important for continuum manipulators. However, the existing static models of cable-driven continuum manipulators, which are based on theories of elasticity, are often very complex and not conducive to efficient computing. In this work, the cable- driven continuum manipulator is equivalent to the traditional rigid one by the pseudorigid-body 3R model. We establish the static equation of the continuum manipulator, which takes into account the effects of friction, multi-segment coupling and external loads. The calculation speed of the static equation obtained by the proposed method is 16.52 times that of obtained by the traditional integration method. Then, the effects of the magnitude and direction of the friction on the curvature and configuration of the manipulator are discussed, respectively. The influences of the configuration and stiffness of the manipulator on the coupling between the segments are also studied. Through the coupling analysis of different stiffness, we give some advice to the design of multi-segment continuum manipulators. Finally, experiments are made through a two-segment continuum manipulator to validate the proposed static model. The maximum position error between simulation and experimental results is 5.57%.

Cable-Constrained Synchronous Rotating Mechanism (CCSRM) has an important application prospect in the field of cable-driven robots, which can greatly reduce the number of driving motors while ensuring the light and slender body. However, there are obvious cable friction effect and elastic deformation in CCSRM. These nonlinear characteristics have a significant impact on synchronous motion performance. In this letter, a model of CCSRM considering cable friction is proposed, which integrates the effects of cable pretension, elastic deformation, and friction between cable and pulley on system characteristics. The distribution law of cable tension under the influence of friction force and the phenomenon of motion hysteresis caused in reverse rotation are emphatically discussed. Then, an improved LuGre friction model is proposed to solve the problem of line contact friction between cables and pulleys. Further a dynamic model of CCSRM is established to simulate the motion characteristics of the whole process, including the discontinuous friction phenomenon in reverse rotation. Finally, an experimental prototype of two-axis synchronous rotating system is built, and the friction coefficient is identified. The experimental results show that the dynamic model can well simulate the motion characteristics of CCSRM.