A large component flexible manufacturing system provides more application scenarios for industrial robots, and, in turn, these robots exhibit competitive advantages in machining applications. However, the structural characteristic of low stiffness is the main obstacle for the industrial robot. Aiming at obtaining sufficient stiffness in the whole machining process, this paper focuses on robot placement optimization in the flexible manufacturing of large components. The geometric center of the machined feature is selected as, firstly, the base point, and the center-reachable placement space of the robot base is obtained by establishing the kinematic model considering a variety of motion constraints. Then, according to the reachability of the machining feature contour, the global placement space meeting all machining boundaries is further extracted. The mapping relationship between joint force and posture is established, and the most suitable robot placement is selected based on the criterion of global stiffness optimization. A series of numerical and finite element simulations verify the correctness and effectiveness of the proposed optimization strategy. The developed stiffness-oriented placement planning algorithm can provide beneficial references for robotic machining applications.

In order to adapt to complex and changeable mechanical conditions and make the deformable mechanisms perform well statically and dynamically, variable stiffness joints have been studied extensively. The variable stiffness actuator is the key driving component to adjust stiffness of the joint. By inserting flexible elements between the driving and driven ends of rigid motion, the variable stiffness actuator makes the joint move precisely and allows humans to interact with machines safely. At present, many kinds of variable stiffness actuators have been applied, among which the way of changing the length of the force arm of leaf springs has obvious advantages. However, overall configuration design, accurate stiffness model, mechanical characteristics and safety analysis have not been studied in depth. This paper investigates a variable stiffness actuator based on leaf spring by design, model and mechanical analysis. The composition and configuration of the actuator is analyzed and optimized. Using the deflection theory of the beam, a new rotational stiffness model of the actuator is established, and a safe position criterion is set up upon the deformation constraint conditions. The variation law of stiffness and the influence of parameters on mechanical characteristics are studied. The finite element analysis method verified the rotational stiffness model, and static test proved that the actuator could effectively work in the joint.

The overrunning clutch, or freewheel, is a kind of universal part with a one-way drive character, and is widely used in machinery. Typical roller overrunning clutches and sprag overrunning clutches have shortcomings such as low load bearing capacity, low torsional stiffness, and short life. For these reasons, studies on high-performance overrunning clutches have always been the focus of researchers. In this paper, a new type of double arc sprag overrunning clutch is proposed that overcomes the disadvantages of poor transmission capacity and low rigidity found in traditional overrunning clutches. The mechanical model of the double arc sprag overrunning clutch is established, the calculation formulas of the overrunning clutch engagement conditions and overrunning conditions are deduced, and the forces of the outer ring, roller, and inner star wheel of the overrunning clutch are also deduced. The contact stress and transmission torque of the overrunning clutch are compared with those of the roller overrunning clutch and the sprag overrunning clutch. The results show that the proposed overrunning clutch has the largest load capacity, which is 5.75 times that of the roller type overrunning clutch, and 2.1 times that of the sprag type overrunning clutch. The experiment shows that the proposed overrunning clutch has reliable bonding conditions in the oil-free and oil-immersed state, and the overrunning condition is sensitive, which indicates the effectiveness of the double arc sprag overrunning clutch. The roller overrunning clutch and double arc sprag overrunning clutch with the same geometric parameters are designed and manufactured, and the torsional stiffness test of the three types of overrunning clutches is carried out. The results show that the torsional stiffness of the double arc sprag overrunning clutch is the largest, which is 4.6 times of the roller overrunning clutch and 6.2 times of the sprag overrunning clutch.

A novel expandable wheel body assembly is designed in this paper. The wheel body assembly utilizes the elastic deformation of the hub to clamp the bearing assembly. The gaps between them are effectively eliminated by this structure, improving the rotational precision and operational stability of the momentum wheel. A finite element model of the momentum wheel was established, and stress analysis was conducted using finite element analysis (FEA) software ANSYS 2025R1 to validate its mechanical integrity. The results demonstrate that the designed momentum wheel meets the required strength specifications. Additionally, the random vibration characteristics of the momentum wheel in a space environment were analyzed using ANSYS simulations, and a corresponding random vibration test was conducted. The good agreement between simulation and experimental results validates the reliability of the finite element model. The results indicate that this new type of momentum wheel can work reliably in aerospace conditions.

A novel expandable wheel body assembly is designed in this paper. The wheel body assembly utilizes the elastic deformation of the hub clamp the bearing assembly. The gaps between them are effectively eliminated by this structure, improving the rotational precision and operational stability of the momentum wheel. A finite element model of the momentum wheel was established, and stress analysis was conducted under constant acceleration using finite element analysis software ANSYS. The results demonstrate that the designed momentum wheel meets the required strength specifications. Additionally, the random vibration characteristics of the momentum wheel in space environments were analyzed, and a random vibration test study was conducted. The results indicate that this new type of momentum wheel can work reliably in aerospace conditions.