In this paper, the torque tracking control problem for a class of series elastic actuators(SEAs) in the presence of unknown payload parameters and external disturbances is investigated. The uncertainties/disturbances ...
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In this paper, the torque tracking control problem for a class of series elastic actuators(SEAs) in the presence of unknown payload parameters and external disturbances is investigated. The uncertainties/disturbances rejection problem for SEAs is addressed from the view of a continuous nonlinear robust control development. Specifically, based on the analysis of a nonlinear SEA, the generic dynamics of SEA systems is described and a novel nonlinear control framework for SEAs is constructed. Then a RISE(robust integral of the sign of the error)-based second-order filter is introduced to synthesize the control law. Moreover, the control performance is theoretically ensured by Lyapunov analysis. Finally, some experimental results are included to demonstrate the superior performance of the proposed control method, in terms of transient response and robustness.
The essential requirements of the end-effector of large space manipulator are capabilities of misalignment tolerance and soft *** to these requirements,an end-effector prototype combining the tendon-sheath transmissio...
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The essential requirements of the end-effector of large space manipulator are capabilities of misalignment tolerance and soft *** to these requirements,an end-effector prototype combining the tendon-sheath transmission system with steel cable snaring mechanism was *** analysis method based on the coordinate transformation and the projection of key points of the mechanical interface was proposed,and it was a guideline of the end-effector ***,the tendon-sheath transmission system was employed in the capture subassembly to reduce the inertia of the capture mechanism and enlarge the capture *** capabilities of misalignment tolerance and soft capture were validated through the dynamic simulation in ADAMS *** results of the capture simulation and experiment show that the end-effector has outstanding capabilities of misalignment tolerance and soft *** translation misalignments in radial directions are±100 mm,and angular misalignments about pitch and yaw are±15°.
A wall-climbing robot that can continuously work on many types of wall surfaces has been developed. This robot based on low-vacuum adsorption principle consists of a locomotion mecha- nism, a sealing device, a fluid m...
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A wall-climbing robot that can continuously work on many types of wall surfaces has been developed. This robot based on low-vacuum adsorption principle consists of a locomotion mecha- nism, a sealing device, a fluid machine and a detecting system. The adsorption force is analyzed in details and its influencing factors are given. The robot prototype, which has the features of high ad- hesion efficiency, light body in weight, small size in structure and good capability in payload, is test- ed in outdoor and indoor environments. Through the experiments, the influences of the impeller slit and the seal clearance are discussed. In addition, the robot functions such as adsorption perform- ance, locomotion performance and wall adaptability are tested by experiments. The experiments have verified that the robot not only can climb on many types of wall surfaces, but also has outstand- ing locomotion ability and payload capacity.
An optimal measurement pose number searching method was designed to improve the pose selection *** optimal robot measurement configurations were added to an initial pre-selected optimal configuration set to establish ...
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An optimal measurement pose number searching method was designed to improve the pose selection *** optimal robot measurement configurations were added to an initial pre-selected optimal configuration set to establish a new configuration set for robot calibration one by *** root mean squares (RMS) of the errors of each end-effector poses after being calibrated by these configuration sets were *** optimal number of the configuration set corresponding to the least RMS of pose error was then *** based on those poses selected by this algorithm can get higher end-effector accuracy,meanwhile consumes less *** optimal pose set including optimal 25 measurement configurations is found during the *** errors after calibration by using these poses are 1.54,1.61 and 0.86 mm,and better than those before calibration which are 7.79,7.62 and 8.29 mm,even better than those calibrated by the random method which are 2.22,2.35 and 1.69 mm in directions X,Y and Z,respectively.
Dielectric elastomer actuators (DEAs) require high energy density to simultaneously achieve high mechanical output while enabling compact and lightweight actuator design. However, the realization of high energy densit...
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In this paper,a method combining perspective-n-point(PnP) and novel iteration algorithm is developed to measure the pose of a target in high precision for Tele-LightSaber *** PnP algorithm is used to obtain a rough po...
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In this paper,a method combining perspective-n-point(PnP) and novel iteration algorithm is developed to measure the pose of a target in high precision for Tele-LightSaber *** PnP algorithm is used to obtain a rough pose,which is taken as the initial value of the iteration *** iteration algorithm utilizes the unit quaternions to represent the *** the result is optimized with Kalman *** the real-time and accuracy of the pose measurement,a fast feature extraction algorithm including object location,edge detection and corner detection is adopted to get the corners in high *** experiments and results verify the effectiveness of the proposed method.
Learning from demonstration(LfD)is an appealing method of helping robots learn new *** papers have presented methods of LfD with good performance in ***,complicated robot tasks that need to carefully regulate path pla...
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Learning from demonstration(LfD)is an appealing method of helping robots learn new *** papers have presented methods of LfD with good performance in ***,complicated robot tasks that need to carefully regulate path planning strategies remain *** or non-contact constraints in specific robot tasks make the path planning problem more difficult,as the interaction between the robot and the environment is *** this paper,we focus on the path planning of complex robot tasks in the domain of LfD and give a novel perspective for classifying imitation learning and inverse reinforcement *** classification is based on constraints and obstacle ***,we summarize these methods and present promising directions for robot application and LfD theory.
In order to obtain direct solutions of parallel manipulator without divergence in real time,a modified global Newton-Raphson(MGNR) algorithm was proposed for forward kinematics analysis of six-degree-of-freedom(DOF) p...
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In order to obtain direct solutions of parallel manipulator without divergence in real time,a modified global Newton-Raphson(MGNR) algorithm was proposed for forward kinematics analysis of six-degree-of-freedom(DOF) parallel *** on geometrical frame of parallel manipulator,the highly nonlinear equations of kinematics were derived using analytical *** MGNR algorithm was developed for the nonlinear equations based on Tailor expansion and Newton-Raphson *** procedure of MGNR algorithm was programmed in Matlab/Simulink and compiled to a real-time computer with Microsoft visual *** for *** performance of the MGNR algorithms for 6-DOF parallel manipulator was analyzed and *** the MGNR algorithm,the real generalized pose of moving platform is solved by using the set of given positions of *** theoretical analysis and numerical results indicate that the presented method can achieve the numerical convergent solution in less than 1 ms with high accuracy(1×10-9 m in linear motion and 1×10-9 rad in angular motion),even the initial guess value is far from the root.
The hydrodynamics of batoid swimming motions is investigated using the three-dimensional simulation of a self-propelled body in still water. The kinematics of batoid swimming is characterized by large amplitude undula...
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The hydrodynamics of batoid swimming motions is investigated using the three-dimensional simulation of a self-propelled body in still water. The kinematics of batoid swimming is characterized by large amplitude undulations of the pectoral fins while the middle part of the body remains straight. The majority of the thrust is generated by pectoral fins. Linear and quadratic amplitude variations are used for the pectoral fins in analyzing the locomotion of the batoid. Navier-Stokes equations are used to solve the unsteady fluid flow. A user defined function and a dynamic mesh method are applied to track the batoid locomotion. The mean swimming velocities of 1.6 BL/s and 1.3 BL/s are achieved, respectively, with thrust coefficients of 0.13 in and 0.095 in the dynamical simulation, where BL/s is the body length per second. The maximum propulsive efficiency 19% is achieved when the frequency of the undulation is 2.2 Hz in both amplitude variations.
In this paper,a visual servoing approach is developed to capture the docking rings of tumbling non-cooperative satellites with a space *** primary challenge addressed is the potential for the docking ring to leave the...
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In this paper,a visual servoing approach is developed to capture the docking rings of tumbling non-cooperative satellites with a space *** primary challenge addressed is the potential for the docking ring to leave the monocular camera’s field-of-view as the manipulator approaches the target,due to the ring’s large *** solve this issue,a two-phase visual servoing scheme combining a monocular camera and a three-line structured light vision system is *** an effort to augment the success rate and safety of capture operations,several constraints are formulated,encompassing manipulator’s kinematics,monocular camera’s field-of-view,obstacle avoidance,structured light’s breakpoints and smooth ***,a nonlinear model predictive controller is proposed to manage these constraints in real-time and regulate the *** models are established based on image moments and pose for each phase,selecting these features as visual feedback to simplify the formulation of servo constraints and avoid the complex circle-based pose ***,to ensure unbiased predictions,the model disturbances arising from the imprecise estimation of target motion parameter are observed using an extended Kalman filter,which are then incorporated into the predictive control *** simulation results demonstrate the effectiveness of this scheme.
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