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A double-ring truss deployable antenna mechanism, which is used as the support and deployment mechanism for large-diameter space-borne antenna, is proposed to improve the stiffness of the single-ring truss deployable antenna with large diameter. The structural decomposition of double-ring truss deployable antenna mechanism is conducted, the screw constraint topology graph of the closed-loop deployable mechanism unit is drawn, and the degree of freedom (DOF) of the mechanism is analyzed. The analyzed result shows that the double-ring truss deployable mechanism has only one DOF. The screw velocity of each component in the mechanism is analyzed based on screw theory, the angular velocity and centroid linear velocity of each component are obtained through vector operation, and the Jacobian matrixes are also obtained. Furthermore, the screw accelerations of the components in the mechanism are derived based on the screw derivative, and the angular acceleration and centroid linear acceleration of each component in the double-ring truss mechanism are obtained. A dynamic model of the double-ring truss mechanism is established based on Newton-Euler equation and virtual work principle, and the numerical calculation and simulation verification are carried out. The research results show that the theoretical analysis is correct. The proposed double-ring truss deployable antenna mechanism has a simple structure, and can be smoothly deployed with only one input drive, the kinematic and dynamic analysis method based on screw theory used in this paper has a clear physical meaning, the analysis process is relatively stylized and is easy to program. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mechanical & Electrical Engineering is the property of Mechanical & Electrical Engineering Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent years, with the development of various types of intelligent robots, new agricultural robots have become frontier technology in the field of international agricultural machinery. And as the complexity and diversity of the agricultural production and operation, the characteristics of advancement and practicability are needed to add to the agricultural robots. In this paper, in order to increase the automation level of agricultural operations and improve the ability of adapting to different working environments, a novel kinematically redundant planar parallel mechanism (PM) with continuous rotational axis and fewer joints is proposed, which has one rotational degree of freedom (DOF) and 2 translational DOFs (2T1R). For the rotational DOF, the rotational axes of the moving platform are mutually parallel at any position of the whole workspace; for the translational DOFs, the directions are simple horizontal and vertical. This robot has a quite simple structure. As we all know, simple structures of the robot can reduce the manufacturing cost to a great extent. This kinematically redundant planar PM is a metamorphic mechanism. For instant, when the moving platform and the intermediate link are locked, the PM becomes an actuation redundant PM. So this PM can be used to research not only the kinematically redundant property but also the actuation redundant property. Actually, this new type PM can be used in the field of food packaging, seed selection, fruit classification, transport, picking, and so on. For the purpose of improving the robot properties, 15 5-DOF hybrid serial-parallel manipulators are constructed on the basis of this type of planar PM. One of these manipulators is selected to do some analysis in this paper, which is more likely to be applied in agriculture. Firstly, the kinematic model of the 5-DOF hybrid manipulator is established. Especially, the forward and inverse kinematics models show the briefness of this robot. What is worth mentioning is that a simple kinematics model is conducive to realize the control of the robot. And this matches the strategy of robot intelligence. The velocity Jacobian matrix is deduced, the singularity analysis of the PM is done according to the Jacobian matrix, and the conditions for reducing singularity are listed. The concept of singularity degree is defined, which can be used to keep away from mechanism singularity. Then based on the flexibility performance index, the optimal design of the 2T1R planar PM is investigated and the performance atlas is drawn. From the performance atlas, we can choose the physical dimensions of the PM. The 3-dimentional model based on a set of optimal physical dimensions is established. After that, in order to reduce weight without the loss of stiffness, the structural topology optimization is accomplished by means of the finite element software. The analysis and comparison of the whole structure are also carried out. This novel hybrid manipulator has the characteristics of simple structure, simple kinematic model, high stiffness, and high degree of modularity, which provides a very variety of application prospects in the field of agricultural machinery. [ABSTRACT FROM AUTHOR]

Agricultural engineering operations are often conducted in complex ground conditions such as fields on a hill, forest land, and hilly land. Compared with 6 degrees of freedom (DOFs) parallel robot, lower-mobility parallel robot is especially suitable for picking, planting and transporting crops in complex ground conditions with the advantages of fewer actuators, fewer components, easy control, easy fabrication, low cost, and so on. One translational and two rotational DOFs parallel mechanism is a representative of lower-mobility parallel robot. In order to expand the application of lower-mobility parallel robot in agriculture, this paper presented a novel 2PRC-PRS parallel mechanism, which has one translational DOF and two rotational DOFs. The motion characteristics of the mechanism and its number of DOFs were analyzed based on the theory of reciprocal screw, and through establishing the moving coordinate system and the fixed coordinate system of the parallel platform, the kinematic screw system of each branch and the corresponding constraint wrenches were calculated, the reciprocal kinematic screws of the constraint wrenches of each branch were solved, and then the DOF nature of the moving platform was analyzed based on the kinematic screws of the moving platform. It concluded that the moving platform had 3 DOFs, which were respectively the movement along the vertical direction and the rotations along the two directions which are perpendicular in the horizontal plane. After analyzing the number of DOFs and the motion characteristics of the 2PRC-PRS parallel mechanism, whether the DOF of the moving platform was instantaneous or not was checked. The results showed that the DOF of the 2PRC-PRS parallel mechanism was not instantaneous, and it was continuous. By adopting Z-X-Y Euler angle to describe posture and position of the parallel platform, the inverse position of the parallel platform was calculated. The model machine of the 2PRC-PRS parallel platform was designed and manufactured; combined with the servo motion controller produced by the Bernecker&Rainer industrial automation company, add the appropriate peripherals, design and set up a network motion control system based on Powerlinks bus for the 2PRC-PRS parallel platform, and assemble the electric control cabinet, the control system included human-computer interaction module, master display module, servo-driven module, sensing module and security module. Adopt modularization approach, and based on the ST programming language, develop the 2PRC-PRS parallel platform control software on Automation Studio 3.0 software development platform. It included interactive interface, security alarm, calibration by returning to zero, uniaxial control, multi-axis control, I/O control, spindle control, and so on, which satisfied the basic demands of the experiment. Then the relevant experiments were carried out based on parallel platform, cabinet and control software. Through the regulation of the speed loop and the position loop of the servo motor, the servo motor parameters tuning was completed, and the electronic gear test was completed by writing electronic gear control program under the position control mode. When the electronic gear ratio was 4:1, and the driving shaft speed was set to 2000, the actual value of the driven shaft speed was 500, and the displacement change of the driving shaft and the driven shaft were also in line with expectations, so the electronic gear experiment was successful, and the control system of high precision met the design requirements. The trajectory planning of the moving platform was carried out and the inverse data were calculated, then the interpolation calculation was conducted. And the interpolation moving data point was carried out by inputting the parallel platform inverse data into the control software. The moving platform moved in accordance with the moving data point after it came back to the initial position and it achieved the expected effect. Finally, combined with the network communication technology, the wireless network remote control experiment was performed separately on IOS mobile terminal under the intranet and PC (personal computer) under extranet, which basically achieved the expected target, and also found the signal transmission delay phenomenon, especially under the condition of wide-area the internet image delay was more obvious. This issue will be further researched. This paper is aimed to provide the theoretical and experimental foundation for the agricultural lower-mobility parallel robot and provide the reference for the researching of this mechatronics equipment. [ABSTRACT FROM AUTHOR]