查看更多>>摘要：The general five-axis toolpath, which consists of lines (or G01 commands) and arcs (or G02/G03 commands), is discontinuous in tangency or curvature at the transition points. The discontinuities will result in deteriorated machining efficiency and quality for the hybrid robot in high-speed machining. Therefore, toolpath smoothing techniques should be implemented. This paper proposes a semi-analytical C2 continuous corner smoothing method. Three types of tool position transitions are addressed considering the error tolerances, and tool orientation smoothing is addressed as a special case of spatial arc-arc smoothing on the unit sphere surface. Based on the analytical smoothing error expressions, the inserted B-splines are generated by numerical algorithms. In addition, the remaining path segments are converted into specially designed quintic B-splines for parameter synchronization, and a unified expression is derived to evaluate their margins. Finally, a feedrate scheduling and interpolation algorithm is proposed for trajectory generation. Simulations and experiments are performed on the TriMule-800 hybrid robot to verify the effectiveness of the proposed method for generating smooth motion in the operational space or joint space.
查看更多>>摘要：The control moment gyroscope (CMG) can provide large roll restoring moment for unmanned motorcycles or bicycles to improve their stability and mobility. However, in most previous CMG-based studies, the balance controllers are on the basis of the inverted pendulum model of the motorcycle or bicycle, i.e., the steering mechanism is locked. As the steering mechanism is a necessary component for the motorcycle and it can also provide a restoring moment for the vehicle, the combined control for balance between CMG and steering is necessary and meaningful. Noting this, this paper studies the dynamic modeling of a motorcycle and proposes a combined balance control method with both steering and double CMGs. A multibody model is presented for dynamic simulation based on Lagrange equations of the first kind. A simplified model is proposed for controller design, based on which a combined balance controller with both steering and double CMGs is developed. The numerical examples are presented to demonstrate the rationality of the simplified model and the effectiveness of the combined balance controller. The simulation results show that the proposed combined controller performs better than the steering controller and the inverted-pendulum-based controller.
Fabio Mazzariol SanticiolliAquila Chagas de CarvalhoFranco Giuseppe DediniJony Javorski Eckert...
22页
查看更多>>摘要：Internal combustion engine vehicles (ICEVs) still represent a major fraction of the global vehicle market and enhancements of conventional vehicle powertrain design have been considered a viable large-scale alternative to reach short-term sustainable goals focused on the reduction of air pollutant emissions and fuel consumption. Thus, the purpose of this paper is to employ a multi-objective optimization for the ICEV drivetrain design and gear shifting control aiming at the minimization of fuel consumption, exhaust emissions and gearbox power losses. The optimization problem is solved by the Interactive Adaptive-Weight Genetic Algorithm (i-AWGA) and comprises different design variables of the multi-speed transmission and differential system, considering constructive constraints. The i-AWGA procedure also optimizes the fuzzy logic shifting controller by defining its input and output membership functions, fuzzy rules and respective weights. The vehicle model is evaluated under a combined driving cycle, therefore robust powertrain configurations can be obtained by the optimization process. The best trade-off solution results in the reduction of gas emissions in 2.32% HC, 3.44% CO and 23.78% NOx, along with the 15.6% fuel savings, facing the standard vehicle.
查看更多>>摘要：Variable Stiffness Actuators (VSAs) have been developed to address the safety and limited adaptability in interactions with uncertainties and energy efficiency issues which exist in traditional "stiff" robots. When desired performance of a VSA is given for a certain application, the question is how this desired performance can be achieved with minimum energy consumption and maximum robustness against uncertainties. This will lead to more compact, lighter but more powerful VSAs. This work develops an understanding of how to optimally design the parameters of the stiffness adjustment mechanisms by developing a framework that can robustly maximize the output performance of VSAs. Five VSA examples, each representing a different design set of stiffness adjustment mechanism, are being considered and evaluated based on the proposed optimization framework to perform a given periodic motion. The resultant optimal design of each set is then compared with the original design in terms of output performance and robustness. The proposed framework shows improvement of the output performance for the given periodic motion up to 546%, with robustness of up to 2.1% perturbation of the optimal design values.
查看更多>>摘要：Wheeled parallel robots combine the advantages of wheeled mobile robots and traditional parallel robots. In this paper, we have introduced wheels in parallel robots as kinematic pairs for the first time. Moreover, a new definition of the incidence matrix of the spatial branched chain is proposed and extended, and the incidence matrix of the wheel is given. Furthermore, we present an automatic type synthesis method for parallel robots with wheels. We synthesized 80 types of open-loop spatial chains with wheels. For the first time, we synthesized two kinds of wheeled parallel robots having six degrees of freedom (6-DOF) with new kinematic characteristics. In addition, a prototype of this 6-DOF wheeled parallel robot was successfully developed with a rated load up to 5 tons. These wheeled parallel robots can be widely used in the field of heavy equipment manufacturing, such as parts processing, transportation, orientation adjustment, automatic assembly, and other industrial operations.
查看更多>>摘要：This paper presents an adaptive robust control method based on a dual extended state observer for a multi-DOF hydraulic manipulator with unknown uncertainties and disturbances. First, the mathematical model of the manipulator is derived considering the hydraulic actuator dynamics. Then, A dual extended stated observer is explored to estimate the matched and unmatched disturbances in the dynamic model simultaneously. Meanwhile, a composite adaptive law using historical data is designed to handle the parameter uncertainties and guarantee that the estimated parameters converge with time. A dynamic surface controller is employed to stabilize the closed-loop system without velocity feedback. Afterward, comparative experiments of the position tracking are performed with two cases, and the results demonstrate the effectiveness of the proposed control method.
查看更多>>摘要：Pulleys used in cable-driven parallel robots (CDPRs) introduce a time-varying geometry that adds significant complexity to the CDPR's kinematic model. The proximal point-to-point method brings significant model error and makes it difficult to achieve high accuracy for CDPRs, especially when the CDPR's scale is small. To solve this problem, this paper establishes the kinematics of CDPRs considering pulley mechanisms and further develops the error model as well as the kinematic calibration method for CDPRs. Firstly, the kinematic characteristics of the pulley mechanisms are analyzed, and the complete kinematic model of CDPRs is established. Then, the error modeling method considering pulley kinematics is established, and the error identification matrix is derived. Based on these results, the kinematic calibration method for CDPRs considering the pulley kinematics is established, including the calibration process and measurement pose selection. Finally, the proposed methods are verified via both simulations and experiments by taking the translational TBot CDPR as an example. The terminal accuracy of the TBot-600 CDPR is improved by 30% with the proposed methods considering the kinematics of pulleys.
查看更多>>摘要：The numerical simulation of flexible multibody systems (FMBSs) with contact is important. Meanwhile, the contact problem is always a key and difficult point for FMBSs; and when impact and friction affect FMBSs, the computational efficiency will dramatically decline. In this work, the nonsmooth contact method (NSCM) for FMBSs is briefly introduced. Moreover, in order to save the computational costs of a contact FMBS, a novel hybrid model order reduction (MOR) strategy based on the idea of data-driven method is proposed. For the hybrid MOR strategy, the reduced-order models (ROMs) based on the NSCM in smooth force part and nonsmooth force part are derived using proper symplectic decomposition and proper orthogonal decomposition, respectively. In addition, in order to adapt the ROMs to parameter variation, the parameter interpolation method on the tangent space of Grassmann manifold is studied. Finally, several numerical examples are tested using the proposed methodology, the results show that compared with the original model, the ROM can save 65.89% of the computing time, and the root-mean-square error between the ROM and original model can reach the order of 10~(-12).
查看更多>>摘要：As a series of tessellation origami patterns consisting of more than one type of polygons, Resch patterns are generally rigid foldable but with a large number of degrees of freedom (DOFs). The patterns are not flat foldable, instead the fully folded configuration is a sandwich style in flat profile. In order to achieve one-DOF forms of triangular Resch pattern units, the thick-panel technique is employed at vertices to replace spherical linkages with spatial linkages. The compatibility among all the vertices is studied by a systematic kinematic analysis of the thick-panel Resch pattern. Finally, two design schemes are obtained to form a one-DOF origami structure between the initial planar structure and the fully folded 3D sandwich structure with dome-curved intermediate folded configurations. The one-DOF Resch pattern structure can be used to generate reliable shape transformation.
查看更多>>摘要：In this paper, a novel multi-mode mobile robot based on the Schatz linkage is proposed. The robot consists of four Schatz linkages, which are distributed at the four corners of the robot. According to the kinematics of the Schatz linkage, the center of mass (CM) of the robot is compensated by designing the profile curve of the touchdown link to reduce the influence of the CM fluctuation on the moving stability of the robot, and the profile curve of the touchdown link makes the robot possess three locomotion modes, including the wheel-like rolling mode, the arm-like climbing mode and the snake-like crawling mode. The performance of the robot on three typical terrains, including the stair, the slope and the ice land, is discussed. In the end, a prototype is fabricated, and the experiment has verified that the robot possesses enough maneuverability to traverse rough terrains in its three locomotion modes.
NSTL
Elsevier