Zero-power balancing a two-link robot manipulator for a predefined point-to-point task

Journal of Mechanical Science and Technology - In this paper, a new balancing approach called “zero-power balancing” (ZPB) method is presented for a two-link robot manipulator (TLRM)...     

Maximum payload path planning for redundant manipulator using indirect solution of optimal control problem

This paper introduces a new method to detect for solder paste defects on printed circuit board. This method not only recognizes volumetric defect but also shape deformity. It involves the use of the region-based classification technique. The 3D profile of solder paste block is first reconstructed using phase shift profilometry. The reconstructed 3D profile is then divided into several regions by geometric segmentation. The resulted regions include edges and top surface. Several features which represent their regions most are extracted and analyzed from the solder paste blocks. Regional classifiers are applied to process these feature spaces. The classifier outputs are then combined to form final detection result for each solder paste block. The performance of the region-based defect detection method is evaluated using 150 and 200 μm solder paste blocks.     

Maximum allowable dynamic load of flexible mobile manipulators using finite element approach

In this paper a general formulation for finding the maximum allowable dynamic load (MADL) of flexible link mobile manipulators is presented. The main constraints used for the proposed algorithm are the actuator torque capacity and the limited error bound for the end-effector during motion on a given trajectory. The accuracy constraint is taken into account with two boundary lines which are equally offset due to the given end-effector trajectory, while a speed-torque characteristics curve of a typical DC motor is used for applying the actuator torque constraint. The finite element method (FEM), which is able to consider the full nonlinear dynamics of mobile manipulators, is applied to derive the kinematic and dynamic equations. In order to verify the effectiveness of the presented algorithm, two simulation studies considering a flexible two-link planar manipulator mounted on a mobile base are presented and the results are discussed.     

Maximum load-carrying capacity of autonomous mobile manipulator in an environment with obstacle considering tip over stability

In order to increase the efficiency of wheeled mobile manipulators (WMM), it is preferred to carry the maximum payload, but in the case of a small-sized platform, which is desirable in applications, it may cause dangerous tip over, especially in the presence of obstacles. So, it is necessary to consider stability constraint in the determination of robot motion planning. This paper presents a novel approach for the determination of the maximum payload-carrying capacity of a coordinated mobile manipulator in an environment with presence of obstacle, based on stability. The proposed method considers the tip over stability on zero moment point criterion, which must be considered when the path of the end-effector is predefined but the position of the mobile platform is free, because tipping over in this condition is probable. Hence, the full dynamic model of WMM (including the coordinating vehicle and manipulator) is used, the obstacle avoidance scheme is implied based on potential functions, and the maximum payload path for a specified payload is generated using the optimal control approach. Then, an iterative method based on the stability criterion and motor restriction, including torque and jerk, was implied to calculate the maximum payload capacity. To the best of our knowledge, this is the first paper reporting on some simulation results as well as successful experiments of implementing the algorithm. The proposed approach has been implemented and tested on a nonholonomic WMM consisting of a differential-drive mobile base and a robotic arm to demonstrate the efficiency and effectiveness of the proposed approach.     

Lyapunov-Based Nonlinear Disturbance Observer for Serial n-Link Robot Manipulators

In this paper we extend the work done by Chen et al. (IEEE Trans Ind Electron 47(4):932–938, 2000) which proposed a nonlinear disturbance observer for two-link robot manipulators to n-link robot manipulators. A general form of dynamic equations of serial n-link robot manipulator is considered, and the stability analysis of the proposed observer is performed by using Lyapunov’s direct method. Although it seems that the formulation of disturbance observer is easy to derive, choosing the disturbance observer gain to guarantee stability is really hard. In this paper it is shown that the design parameter can be selected depends on the maximum velocity and physical parameters of robot manipulator to guarantee the global asymptotic stability of the disturbance observer. Using this nonlinear disturbance observer, no accurate dynamic model is required to achieve high precision motion control, because it makes the system robust against internal disturbances such as unmodeled dynamics and external disturbances such as friction in joints. The effectiveness of the proposed observer is investigated by numerical simulation for three-Dofs robot manipulator. In fact, controller with disturbance observer has more superior tracking performance, with a wide range of payloads and in the presence of friction in joints. It is also found that, although the proposed observer is designed for slow varying disturbances, it can estimate rapid time varying disturbances very well.     

Maximum allowable dynamic load of flexible mobile manipulators using finite element approach

In this paper a general formula for finding the maximum allowable dynamic load (MADL) of flexible link mobile manipulators is presented. The main constraints used for the proposed algorithm are the actuator torque capacity and the limited error bound for the end-effector during motion on a given trajectory. The accuracy constraint is taken into account with two boundary lines which are equally offset due to the given end-effector trajectory, while a speed-torque characteristics curve of a typical DC motor, is used for applying the actuator torque constraint. Finite element method (FEM), which is able to consider the full nonlinear dynamic of mobile manipulator is applied to derive the kinematic and dynamic equations. In order to verify the effectiveness of the presented algorithm, two simulation studies considering a flexible two-link planar manipulator mounted on a mobile base are presented and the results are discussed.