Numerical analysis of transient performance of grounding systems considering soil ionization by coupling moment method with circuit theory

Soil ionization has a great effect on the performance of grounding electrodes fed by currents of high magnitude. In this paper, a numerical method is proposed to analyze the transient performance of grounding system, which takes account of the dynamic and nonlinear effects of soil ionization. The method couples moment method with circuit theory and Fourier transform. The transient performance of grounding system considering the soil ionization effect is compared with that not considering soil ionization effect.     

Acceleration estimator for low-velocity and low-accelerationregions based on encoder position data

Acceleration computation based on simple numerical differentiation from an optical encoder signal may be very erroneous, especially in the low-velocity and low-acceleration regions. To overcome this problem, a novel approach to estimating acceleration in these regions is proposed in this paper. This low-acceleration estimator, which is a computer algorithm, is based on the fact that the displacement signal from the encoder is accurate. Since the bandwidth of this estimator is rather limited, it can be used in combination with the traditional numerical differentiation approach in order to cover a wide velocity range. It was shown in various simulations and experiments that this combined acceleration estimator can yield accurate acceleration estimates over a wide range of velocities. Furthermore, when this estimator is applied to a friction compensation system, the effect of low-velocity friction can be reduced significantly by its capability to detect small changes in acceleration caused by friction     

Atomic scale effects of alloying,partitioning, solute drag and austempering on the mechanical properties of high-carbon bainitic–austenitic TRIP steels

Understanding alloying and thermal processing at an atomic scale is essential for the optimal design of high-carbon (0.71 wt.%) bainitic–austenitic transformation-induced plasticity (TRIP) steels. We investigate the influence of the austempering temperature, chemical composition (especially the Si:Al ratio) and partitioning on the nanostructure and mechanical behavior of these steels by atom probe tomography. The effects of the austempering temperature and of Si and Al on the compositional gradients across the phase boundaries between retained austenite and bainitic ferrite are studied. We observe that controlling these parameters (i.e. Si, Al content and austempering temperature) can be used to tune the stability of the retained austenite and hence the mechanical behavior of these steels. We also study the atomic scale redistribution of Mn and Si at the bainitic ferrite/austenite interface. The observations suggest that either para-equilibrium or local equilibrium-negligible partitioning conditions prevail depending on the Si:Al ratio during bainite transformation.     

Global Localization Using Low-frequency Image-based Descriptor and Range Data-based Validation

International Journal of Control, Automation and Systems - In image-based global localization, a robot pose is estimated through image association when the robot revisits a previously visited...     

Equilibrium point control of a robot manipulator using biologically-inspired redundant actuation system

Unlike their robotic counterparts, humans excel at various contact tasks even in unknown environments by utilizing their ability to adaptively modulate the arm impedance. As one of many theories in human motor control, the equilibrium point control hypothesis suggests that multi-joint limb movements can be achieved by shifting the equilibrium positions defined by the central nervous system and utilizing the spring-like property of the peripheral neuromuscular system. To generate human arm-like compliant motion, this study implements the equilibrium point control on a robot manipulator using redundant actuation: two actuators are installed on each joint: one to control the joint position and the other to control the joint stiffness, respectively. With the double-actuator unit, the equilibrium position and stiffness (or impedance) can be independently programmed. Also, it is possible to estimate the contact force based on angle measurement with a user-specified stiffness. These features enable the robot manipulator to execute stable and safe movement in contact tasks. A two-link manipulator equipped with the double-actuator units was developed, and experimental results from teleoperated contact tasks show the potential of the proposed approach.     

Efficient autonomous global localization for service robots using dual laser scanners and rotational motion

This study presents an alternative global localization scheme that uses dual laser scanners and the pure rotational motion of a mobile robot. The proposed method extracts the initial state of the robot’s surroundings to select robot pose candidates, and determines the sample distribution based on the given area map. Localization success is determined by calculating the similarity of the robot’s sensor state compared to that which would be expected at the estimated pose on the given map. In both simulations and experiments, the proposed method shows sufficient efficiency and speed to be considered robust to real-world conditions and applications.

     

Collision detection algorithm robust to model uncertainty

With the widespread use of service robots, safety issues regarding human-robot collisions have received increasing attention. The collision detection algorithm, which allows a robot to effectively detect and react against a collision, is considered as one of the most practical solutions for ensuring collision safety. However, these algorithms are often model-based, so it cannot ensure collision safety under payload variations or model uncertainty. In this paper, a novel collision detection algorithm based on torque filtering is proposed to cope with this problem. The torque due to the motion of the robot can be effectively removed using the Butterworth 2nd-order BPF (band pass filter) so that only the torque due to a collision is used for collision detection. This improves the robustness of the algorithm against model uncertainties. The proposed algorithm does not require the use of acceleration data. The performance of the algorithm was experimentally verified.     

Steering control algorithm for efficient drive of a mobile robot with steerable omni-directional wheels

Omnidirectional mobile robots are capable of arbitrary motion in an arbitrary direction without changing the direction of wheels because they can perform 3-DOF motions on a plane. This paper presents a novel mobile robot design with steerable omnidirectional wheels. This robot can operate in either omnidirectional or differential drive modes, depending on the drive conditions. In the omnidirectional mode, the robot has 3 DOF in motion and 1 DOF in steering, which can function as a continuously variable transmission (CVT). The CVT function can be used to enhance the efficiency of the robot operation by increasing the range of the velocity ratio of the robot velocity to wheel velocity. The structure and kinematics of this robot are presented in detail. In the proposed steering control algorithm, the steering angle is controlled such that the motors may operate in the region of high velocity and low torque, thus operating with maximum efficiency. Various tests demonstrate that the motion control of the proposed robot works satisfactorily and the proposed steering control algorithm for CVT can provide a higher efficiency than the algorithm using a fixed steering angle. In addition, it is shown that the differential drive mode can give better efficiency than the omnidirectionaldrive mode.     

Image Preprocessing-based Generalization and Transfer of Learning for Grasping in Cluttered Environments

International Journal of Control, Automation and Systems - In a cluttered environment in which objects are lying very closely to each other, the arranging motion is required before the robot...