Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 6 Articles
A mechanism that allows a robotic arm to quickly grip various forms of objects at disaster sites will enhance the\nmobility of rescue robots by keeping their bodies stable and maintaining manipulability for target objects, such as\ndebris. Such a mechanism requires the ability to quickly and omnidirectionally change arm postures toward the target\nand hold it in a stable manner. Continuum robots are expected to provide this functionality. Conventional continuum\nrobots realize the function of changing arm postures and grasping objects by controlling pneumatic actuators with\nmultiple air chambers arranged in parallel. However, conventional robots cannot be applied to potential disaster\nsites filled with flammable gases, gasoline, or high radiation levels because they require electronic components (e.g.,\nsolenoid valves, and sensors) to control air pressures. This study proposes a unique approach to realize reflexive omnidirectional\nbending motion using only mechanical components without any electrical devices. The proposed system\nrealizes a reflexive motion to bend the arm in the targetââ?¬â?¢s direction by detecting a contact location using a mechanical\nreactive system. The proposed simple mechanism has the advantages of high durability and easy implementation.\nThis paper aims to confirm the proposed concept by prototyping a drive mechanism coupled with contact detection\nand bending motion using mechanical port valves. We report the design concept and development of this prototype.\nThe fundamental characteristics and feasibility of the proposed mechanism are experimentally confirmed. First, a\nprototype is developed using a mathematical model. Its performance in the bending and omnidirectional motions is\nevaluated. The results show that the model has a margin of âË?â??4.9% error in the bending angle and âË?â??7.4% error in the\ncentral curvature compared with the experimental values. We also confirm that using a higher pressure could realize a\nsmaller radius of curvature and reduce an unnecessary twisting motion. We also tested a second prototype to confirm\nthe grasping motion and force by changing the applied pressures. The influence of the bending direction was then\nevaluated. We confirm that a higher pressure generated a larger grasping force. The prototype can omnidirectionally\nproduce approximately the same forces although the generated forces depend on the number of air chambers\nexcited by the contact pads. Subsequently, we experimentally confirm the influence of gravity. The test shows\nthat the effect of own weight greatly influences the posture after the object is in contact. This effect should not be\nignored. Furthermore, the curve became sufficiently large when its contact pad is pressed. This result experimentally\nproved that self-holding is possible. The experimental results show the potential of the proposed mechanism....
To data, outside of the controlled environments, robots normally perform manipulation tasks operating with human.\nThis pattern requires the robot operators with high technical skills training for varied teach-pendant operating system.\nMotion sensing technology, which enables humanââ?¬â??machine interaction in a novel and natural interface using gestures,\nhas crucially inspired us to adopt this user-friendly and straightforward operation mode on robotic manipulation.\nThus, in this paper, we presented a motion sensing-based framework for robotic manipulation, which recognizes\ngesture commands captured from motion sensing input device and drives the action of robots. For compatibility, a\ngeneral hardware interface layer was also developed in the framework. Simulation and physical experiments have\nbeen conducted for preliminary validation. The results have shown that the proposed framework is an effective\napproach for general robotic manipulation with motion sensing control....
Robots play more important roles in daily life and bring us a lot of convenience. But when people work with robots,\nthere remain some significant differences in humanââ?¬â??human interactions and humanââ?¬â??robot interaction. It is our goal\nto make robots look even more human-like. We design a controller which can sense the force acting on any point\nof a robot and ensure the robot can move according to the force. First, a springââ?¬â??massââ?¬â??dashpot system was used to\ndescribe the physical model, and the second-order system is the kernel of the controller. Then, we can establish the\nstate space equations of the system. In addition, the particle swarm optimization algorithm had been used to obtain\nthe system parameters. In order to test the stability of system, the root-locus diagram had been shown in the paper.\nUltimately, some experiments had been carried out on the robotic spinal surgery system, which is developed by our\nteam, and the result shows that the new controller performs better during humanââ?¬â??robot interaction....
Compliant actuators are more advantageous than stiff actuators in some circumstances, for example, unstructured environment\nrobots and rehabilitation robots. Compliant actuators aremore adaptive and safe. Constant stiffness compliant actuators have some\nlimitations in impedance and bandwidth. Variable stiffness actuators improve their performance owing to introducing an extra\nmotor to tune the stiffness of the actuators. However, they also have some limitations such as the bulky structure and heavy weight.\nIt was also found that there are some waste functions existing in the current variable stiffness actuators and that the fully decoupled\nposition control and stiffness tune are not necessary, because there exist some regular phenomena during most circumstances of\nhuman interaction with the robots which are ââ?¬Å?low load, low stiffness and high load, high stiffnessââ?¬Â. In this paper, a design method\nfor nonlinear stiffness compliant actuator was proposed which performed the predefined deflection-torque trajectory of the regular\nphenomenon. A roller and a cantilever which has special curve profile constitute the basic mechanical structure of the nonlinear\nstiffness compliant actuators. An error compensation method was also proposed to analyze the stiffness of elastic structure. The\nsimulation results proved that the proposed method was effective in designing a predefined nonlinear stiffness compliant actuator....
To improve the operating performance of robots� end-effector, a humanoid robot hand based on coupling four-bar linkage\nwas designed. An improved transmission system was proposed for the base joint of the thumb. Thus, a far greater\nmotion range and more reasonable layout of the palm were obtained. Moreover, the mathematical model for kinematics\nsimulation was presented based on the Assur linkage group theory to verify and optimize the proposed structure. To\nresearch the motion relationships between the fingers and the object in the process of grasping object, the grasping analysis\nof multi-finger manipulation was presented based on contact kinematics. Finally, a prototype of the humanoid robot\nhand was produced by a three-dimensional printer, and a kinematics simulation example and the workspace solving of\nthe humanoid robot hand were carried out. The results showed that the velocities of finger joints approximately met\nthe proportion relationship 1:1:1, which accorded with the grasping law of the human hand. In addition, the large workspace,\nreasonable layout, and good manipulability of the humanoid robot hand were verified....
Due to the urgent need for high precision surgical equipment for minimally invasive spinal\nsurgery, a novel robot-assistant system was developed for the accurate placement of pedicle screws\nin lumbar spinal surgeries. The structure of the robot was based on a macro-micro mechanism,\nwhich includes a serial mechanism (macro part) and a bi-planar 5R parallel mechanism (micro part).\nThe macro part was used to achieve a large workspace, while the micro part was used to obtain\nhigh stiffness and accuracy. Based on the transfer function of dimension errors, the factors affecting\nthe accuracy of the end effectors were analyzed. Then the manufacturing errors and joint angle\nerror on the position-stance of the end effectors were investigated. Eventually, the mechanism of the\nstrain energy produced by the deformation of linkage via forced assembly and displacements of the\noutput point were calculated. The amount of the transfer errors was quantitatively analyzed by the\nsimulation. Experimental tests show that the error of the bi-planar 5R mechanism can be controlled\nno more than 1 mm for translation and 1ââ??¦ for rotation, which satisfies the required absolute position\naccuracy of the robot....
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