Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
This work proposes a new positioning method based on multiple ultrasonic sensors for\nthe autonomous mobile robot. Unlike the conventional ultrasonic positioning methods, this new\nmethod can realize higher accuracy ultrasonic positioning without additional temperature\ninformation. Three ultrasonic sensors are used for positioning. A generalized measurement model\nis established for general sensor configuration. A simplified measurement model, which considers\nthe computational complexity, is also established for linear/simplified sensor configuration. Three\ntime-of-flight signals are obtained from the three ultrasonic sensors. The coordinates of the target\nare calculated by the ratios of time-of-flights. Positioning experiments were carried out to verify the\nfeasibility and effectiveness of the proposed method. Experimental results show that the new\nultrasonic positioning method is effective, both the two established models can implement\npositioning successfully, and the positioning accuracy is satisfactory. Compared with the\nconventional ultrasonic positioning method with the default ultrasonic velocity, the positioning\naccuracy is greatly improved by the proposed method. Compared with the ultrasonic positioning\nmethod with additional temperature compensation, the results obtained by the proposed method\nare comparable....
In this study, the configuration of a bionic horse robot for equine-assisted therapy is presented. A single-leg system with two degrees\nof freedom (DOFs) is driven by a cam-linkage mechanism, and it can adjust the span and height of the leg end-point trajectory.\nAfter a brief introduction on the quadruped bionic horse robot, the structure and working principle of a single-leg system are\ndiscussed in detail. Kinematic analysis of a single-leg system is conducted, and the relationships between the structural\nparameters and leg trajectory are obtained. On this basis, the pressure angle characteristics of the cam-linkage mechanism are\nstudied, and the leg end-point trajectories of the robot are obtained for several inclination angles controlled by the rotation of\nthe motor for the stride length adjusting. The closed-loop vector method is used for the kinematic analysis, and the motion\nanalysis system is developed in MATLAB software. The motion analysis results are verified by a three-dimensional simulation\nmodel developed in Solidworks software. The presented research on the configuration, kinematic modeling, and pressure angle\ncharacteristics of the bionic horse robot lays the foundation for subsequent research on the practical application of the proposed\nbionic horse robot....
In order to shorten the research and development cycle of quadruped robot, it is significant to solve the problem of single leg\nweight-bearing and obtain a smooth gait switching. Firstly, a leg structure with an antiparallelogram is proposed, which greatly\nenhances the strength and stiffness of the leg in this paper. Secondly, the Simulink-ADAMS cosimulation platform is built and the\nimproved Hopf oscillator is used in the control of robot. This control mode based on CPG realizes the walk and trot gait of\nquadruped robot. Thirdly, in order to solve the problems of breakpoints, phase-locked, and stopping of gait curve in the process of\ngait switching by directly replacing the gait matrix, the functional relationship between the right hind leg and duty cycle is\nintroduced to realize the smooth transition of gait curve. The simulation results show that the proposed algorithm can achieve a\nsmooth gait transformation within 4-6 second, which preliminarily proves the feasibility of the algorithm. Finally, the experimental\nplatform is built and the control algorithm is written into the controller to realize the specific gait of the robot, which\nproves the effectiveness of the proposed method....
Although the kinematics and dynamics of spherical robots (SRs) on flat horizontal and inclined 2D surfaces are thoroughly\ninvestigated, their rolling behavior on generic 3D terrains has remained unexplored. This paper derives the kinematics equations\nof the most common SR configurations rolling over 3D surfaces. First, the kinematics equations for a geometrical sphere rolling\nover a 3D surface are derived along with the characterization of the modeling method. Next, a brief review of current mechanical\nconfigurations of SRs is presented as well as a novel classification for SRs based on their kinematics. Then, considering the\nmechanical constraints of each category, the kinematics equations for each group of SRs are derived. Afterward, a path-tracking\nmethod is utilized for a desired 3D trajectory. Finally, simulations are carried out to validate the developed models and the\neffectiveness of the proposed control scheme....
A deep analysis of ankle mechanical properties is a fundamental step in the design of\nan exoskeleton, especially if it is to be suitable for both adults and children. This study aims\nat assessing age-related differences of ankle properties using pediAnklebot. To achieve this aim,\nwe enrolled 16 young adults and 10 children in an experimental protocol that consisted of the\nevaluation of ankle mechanical impedance and kinematic performance. Ankle impedance was\nmeasured by imposing stochastic torque perturbations in dorsi-plantarflexion and inversion-eversion\ndirections. Kinematic performance was assessed by asking participants to perform a goal-directed task.\nMagnitude and anisotropy of impedance were computed using a multiple-input multiple-output\nsystem. Kinematic performance was quantified by computing indices of accuracy, smoothness,\nand timing. Adults showed greater magnitude of ankle impedance in both directions and for all\nfrequencies, while the anisotropy was higher in children. By analyzing kinematics, children performed\nmovements with lower accuracy and higher smoothness, while no differences were found for the\nduration of the movement. In addition, adults showed a greater ability to stop the movement when\nhitting the target. These findings can be useful to a proper development of robotic devices, as well as\nfor implementation of specific training programs....
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