No abstract

In this paper, the chaotic characteristics of air traffic flow are studied, ADS-B data easily available to ground aviation users are selected as the basic data of traffic flow, and a high-dimensional prediction model of air traffic flow time series based on the noniterative PSR-ELM algorithm is established. The prediction results of the proposed algorithm are then compared with those of the SVR algorithm, which requires iteration. Moreover, airspace operation data before and after the outbreak of the COVID-19 epidemic are selected as the experimental scene, and the prediction effects of time series with different degrees of chaos are comparatively analyzed. The experimental results reveal that the PSR-ELM algorithm achieves fast and accurate results, and, when the traffic flow state is sparse, the degree of chaos is reduced and the prediction effect is improved. The findings of this research provide a reference for air traffic flow theory.

Presented in this paper is a method for analysis and control of an actuation-redundant parallel mechanism requiring synchronization. The said mechanism is made up of two branches that are connected to drive a common end-effector with only one degree-of-freedom of motion. The two actuators must share the load exerted on the common end-effector during motion. The underlying problem is to synchronize the motion of the two actuators while balancing the forces on them so that the entire mechanism can move smoothly under the applied load on the end-effector. Due to the space limitation, the two branches are geometrically different leading to opposite force profiles for the two actuators. The proposed method combines the mechanism kinematics with force analysis. First, a closed-form solution is derived that relates the actuator strokes to the rotation angle of the end-effector. Second, a velocity relationship is obtained to relate the actuator velocities to the angular velocity of the end-effector. Third, a force relationship is established relating the actuator loads to the external load. Fourth, a control strategy is designed to synchronize the motion of the two actuators while maintaining the force balance between them to avoid the problem of motion mismatching and force fighting that could lead to the failure of the mechanism. A prototype was built and tested with the proposed method, which is also presented in this paper.

No abstract

No abstract

In this paper, a new design is presented for shape morphing using parameterized curves. Inspired by minimal actuation effort, a multiloop linkage is designed with a single input, allowing a morphing curve to take on three distinct shapes. The underlying design is based on a network of four-bar linkages connected together to form a multiloop linkage, referred to as the curve adaptive linkage array (CALA). A three-step method is developed and presented here to find the geometric dimensions of the CALA. The proposed solution is based on the simultaneous recursive solving of the traditional single-loop dyad equations for multiple loops. The key in obtaining a feasible solution is through parameterization of the curves that the linkage is required to morph. To show the effectiveness of the method, an airfoil morphing application is presented, solved using the proposed method, and validated by a prototype. The presented synthesis method provides an effective means for designing a multiloop linkage with a single input.

No abstract

No abstract