Modeling and Validation of a Passive Truss-Link Mechanism for Deployable Structures Considering Friction Compensation with Response Surface Methods

In this study, a passive truss-link mechanism applicable to large-scale deployable structures was designed to achieve successful deployment in space. First, we simplified the selected truss-link mechanisms to the two-dimensional geometry and calculated the degrees of freedom (DOF) to determine whether a kinematic over-constraint occurs. The dimensions of the truss-link structure were determined through a deployment kinematic analysis. Second, a deployment simulation with the truss-link was conducted using multibody dynamics (MBD) software. Finally, a deployment test was performed considering gravity compensation, and the results were compared with those of MBD simulation. The results of the deployment simulations were confirmed to be slightly faster than those of the deployment test due to friction effects existing in the joints and gravity compensation devices. To address this issue, inverse identification of the equivalent frictional torque (EFT) at the revolute joints in the deployment test was conducted through response surface methods (RSM) combined with the central composite design technique. As a result, we confirmed that the deployment angle history of the deployment simulation was similar to that of the deployment test.

A Versatile Aerial Manipulator Design and Realization of UAV Take-Off from a Rocking Unstable Surface

UAVs are one of the fastest types of robots that can be deployed in a remote environment. Unfortunately, they have a limited flight time and therefore may need to stop occasionally in an unknown, uncontrolled area. However, conventional UAVs require flat and stationary surfaces for a safe landing and take-off. Some studies on adaptive landing approach for UAVs can be found in the past, but adaptive take-off from non-flat surfaces has not been discussed for the most part, yet. In this work, we discuss the problems associated with a conventional UAV take-off from non-flat surfaces and provide a novel approach for UAV take-off from a sloped or rocking surface. We also discuss the design of a novel multitasking three-arm aerial manipulator system with parallel link mechanism and achieve the above-mentioned task. With experiments, we show that the system can provide stability for a UAV landing on a rocking surface that allows for a safe take-off.

Numerical optimization and experimental validation of a five-link mechanism, potato planter

Covering with plastic film in fall and planting through the film in spring is an effective drought-resistance, potato-cultivation method. To achieve proper under-plastic-film, hill-drop potato seeding, the geometry of an existing five-link planter mechanism that is driven synchronously by two cranks rotating in the same direction has been refined through bivariate plots and numerical optimization. For this purpose, novel quantitative measures of the geometry of the crunode portion of the dibber-tip path have been introduced. The prototype planter mechanism described in detail elsewhere has then been configured according to the three optimum kinematic solutions obtained, and field tests have been carried out. All three configurations satisfied the imposed agronomic requirements of potato planting through the plastic film, with one setup performing better than the other two, and then a previously reported solution obtained through manually conducted optimization.

Experimental investigations of the dynamic responses of a multi-link mechanism with revolute clearance joints

Joint clearance is unavoidable in the revolute joint of multi-link mechanism. Excessive value of joint clearance generally leads to the noise, vibration, and fatigue failure. In this paper, a multi-link articulated mechanism system with three revolute clearance joints is selected as the study object. At first, its ideal motion equations and dynamic responses without joint clearance are outlined. Then an experimental rig is set up, and the acceleration responses of the mechanism in different scenarios are investigated. Comparative analysis indicates that in the presence of joints clearance, clear periodic transient impacts appear in the acceleration outputs while this mechanism moves to specific positions, and the impacts amplitude increases along with the clearance size and driving speed. Also, certain sequence among three motion states of clearance joint, named free flight, penetration and continuous-contact is observed twice in one circle movement of the mechanism. Besides, the clearance joint at the end of the transmission chain has greater effects on the mechanism system than the other joints. Finally, flexible rubber sleeves are set into the clearance joints, and the obtained experimental results indicate that the undesired transient impact by clearance joints on the mechanical system can be suppressed by flexible sleeves.

ЗАСТОСУВАННЯ МЕХАНІЗМУ ЧЕТВЕРТОГО КЛАСУ ДЛЯ ПРИВОДУ ВУШКОВИХ ГОЛОК ОСНОВОВ’ЯЗАЛЬНОЇ МАШИНИ

Development and research of functionally-adequate target mechanisms of technological machines of light industry with application of applied CAE-programs. Used the apparatus of vector algebra; analytical and numerical methods for determining the position functions of planar mechanisms containing a structural group of the fourth class of the second order, based on the vector transformation of coordinates; random search method for metric synthesis of flat mechanisms; methods of computer visualization and animation of kinematic schemes of flat mechanisms of higher classes. Mathematical models describing the position functions of the mechanism of eyelets of a warp knitting machine containing a structural group of the fourth class of the second order with rotating kinematic pairs in the form of angles of moving links, free vectors constructed on these links and radius vectors of characteristic points of the mechanism as a function of the angle of rotation of the master crank. The geometrical parameters of the flat six-link mechanism of eyelets for the warp knitting machine containing the structural group of the fourth class of the second order with rotating kinematic pairs as a result of metric synthesis of the mechanism by random search in CAE-program are determined; computer circuit modeling of the obtained mechanism is performed; graphs of visualization and animation of the kinematic scheme of the received mechanism are constructed; identification of the kinematic scheme of the obtained mechanism for compliance with the accepted structure; the received graph of function of position of an auricular needle of the mechanism of the fourth class; the functions of the position of the eye needle of the new mechanism and the mechanism of the basic knitting machine OV-7 are compared. The structure of a flat six-link mechanism, containing structural groups of the fourth class of the second order with rotating kinematic pairs, is proposed for use as a drive in a warp knitting machine on the example of the mechanism of oscillating movement of eyelets. The geometric dimensions of the moving parts of the functionally adequate mechanism of the fourth class for the drive of the eye needles of the basic knitting machine are determined. Software blocks for automated computer metric synthesis and calculation of link angles and radius vectors of characteristic points of the mechanism in the CAE program have been created. Practical Value is to use the results for the design and construction of flat mechanisms of the fourth class with rotating kinematic pairs of warp knitting machines, in which the working bodies make stops during the work process.