Parameters Of Robot Research Articles

Robustness and efficiency insights from a mechanical coupling metric for ankle-actuated biped robots

This paper presents results pertaining to the coupling between the actuated and unactuated degrees of freedom for biped robots. It is focused on revealing the qualitative relationship between a mechanical coupling metric and gait characteristics for an ankle-actuated biped robot. By considering robot models with varying masses, leg lengths and positions of the center of mass of the legs, it validates the universality of prior results based on a single robot model. The development of a method for designing ankle-actuated biped gaits is given in detail, and numerical computation is utilized to find the initial conditions needed to generate the ankle-actuated candidate gait regions. The correlation between the coupling metric and the maximum magnitude of disturbance that can be rejected is significant, regardless of the robot parameters. It indicates that robust gaits tend to have small coupling under zero disturbance so that the “reserve” coupling may be utilized to reject the disturbance. Furthermore, for the same walking speed, gaits with smaller cost of transport under zero disturbances have smaller coupling and therefore should be more robust, which highlights the value of gait optimization for biped walking. The coupling metric for hip actuation is also briefly discussed as a contrast.

SCALAR: Simultaneous Calibration of 2-D Laser and Robot Kinematic Parameters Using Planarity and Distance Constraints

In this paper, we propose SCALAR, a calibration method to simultaneously calibrate the kinematic parameters of a 6-DoF robot and the extrinsic parameters of a 2D Laser Range Finder (LRF) attached to the robot's flange. The calibration setup requires only a flat plate with two small holes carved on it at a known distance from each other, and a sharp tool-tip attached to the robot's flange. The calibration is formulated as a nonlinear optimization problem where the laser and the tool-tip are used to provide planar and distance constraints, and the optimization problem is solved using Levenberg-Marquardt algorithm. We demonstrate through experiments that SCALAR can reduce the mean and the maximum tool position error from 0.44 mm to 0.19 mm and from 1.41 mm to 0.50 mm, respectively.

Концепція синтезу крокуючих роботів довільної орієнтації

Robots of arbitrary orientation (Climber Robot) are a new modification of mobile robots. These robots are equipped with means of holding the robot on a surface of arbitrary orientation relative to the horizon of the technological space. The creation of this type of robotics is at the initial stage and is dictated by the need to perform technological operations for monitoring industrial facilities, installation and dismantling of building structures, repair and preventive maintenance of their components. The article proposed three basic principles for the synthesis of walking mobile robots: the accumulation and transformation of energy, the integration of motion drives and the use of a generator of reactive pneumatic thrust. The implementation of these principles helps to reduce the total power of the drives and to increase the reliability of the holding robots on the surface of an arbitrary orientation in the technological space. The results of mathematical modeling of constructive and technological parameters of mobile robots are described. Ref. 18, pic. 7

Status evaluation of mobile welding robot driven by fuel cell hybrid power system based on cloud model

The comprehensive evaluation of the performance parameters of the mobile welding robot driven by the fuel cell hybrid power system is beneficial to optimizing the energy efficiency and control performance of the system. However, few studies have paid attention to this aspect. Rough analytic hierarchy process and entropy weight method are used to calculate the weight of the evaluation index. Cloud model is used to synthesize all evaluation indicators to determine the status level. First, the golden section method is used to determine the evaluation criteria, and through cloud model, the evaluation criteria and measured parameters of the single evaluation index are transformed into corresponding evaluation reference clouds and evaluation clouds. Second, the weight of the evaluation index is determined by the method of the rough analytic hierarchy process, and the method of the entropy weight is used to revise the method of the rough analytic hierarchy process. The single evaluation reference cloud and evaluation cloud are aggregated to get the comprehensive evaluation reference cloud, and the comprehensive evaluation of the reference cloud is carried out. The evaluation cloud for each evaluation cycle. Finally, according to the correlation between the comprehensive evaluation cloud and the comprehensive evaluation standard cloud, the performance level of each evaluation cycle is determined. In this paper, the randomness and fuzziness of the qualitative concepts are solved by using the characteristics of the cloud model. Combined with rough analytic hierarchy process, the objectivity of the data is maintained and the advantages of the expert evaluation are enhanced. The validity of the model is verified by comparing the existing methods. These studies evaluate and classify the real-time status of the fuel cell robot, and provide a basis for the performance optimization and energy optimization of the hybrid power system controllers.

Medical robotics simulation framework for application-specific optimal kinematics

Abstract Most kinematic structures in robot architectures for medical tasks are not optimal. Further, the workspace and payloads are often oversized which results in high product prices that are not suitable for a clinical technology transfer. To investigate optimal kinematic structures and configurations, we have developed an adaptive simulation framework with an associated workflow for requirement analyses, modelling and simulation of specific robot kinematics. The framework is used to build simple and cost effective medical robot designs and was evaluated in a tool manipulation task where medical instruments had to be positioned precisely and oriented on the patient's body. The model quality is measured based on the maximum workspace coverage according to a configurable scoring metric. The metric generalizes among different human body shapes that are based on anthropometric data from UMTRI Human Shape. This dexterity measure is used to analyze different kinematic structures in simulations using the open source simulation tool V-REP. Therefor we developed simulation and visualization procedures for medical tasks based on a patchwork of size-variant anatomical target regions that can be configured and selectively activated in a motion planning controller. In our evaluations we compared the dexterity scores of a commercial lightweight robot arm with 7 joints to optimized kinematic structures with 6, 7 and 8 joints. Compared to the commercial hardware, we achieved improvements of 59% when using an optimized 6- dimensional robot arm, 64% with the 7-dimensional arm and 96% with an 8-dimensional robot arm. Our results show that simpler robot designs can outperform the typically used commercial robot arms in medical applications where the maximum workspace coverage is essential. Our framework provides the basis for a fully automatic optimization tool of the robot parameters that can be applied to a large variety of problems.

Parameter estimation survey for multi-joint robot dynamic calibration case study

Accurate model parameters are the basis of robot dynamics. Many linear and nonlinear models have been proposed to calibrate the inertial parameters and friction parameters of multi-joint robots. However, methods of choosing a model and calculating its parameters still have few summaries. This paper reviews typical linear/nonlinear models and different calculation methods for robot dynamic calibration. Through simulations, the features of different methods are analyzed, including torque error, parameter error, model adaptability, solution time, and anti-interference ability of the calibration results. Finally, an experiment performed on a six-degree-of-freedom industrial manipulator is used as an example to illustrate how to select the model for a specified robot. These comparisons and experiments provide references for the parameter calibration of multi-joint robots.

Advanced robotics analysis toolbox for kinematic and dynamic design and analysis of high‐DOF redundant serial manipulators

AbstractThis study aimed to develop a toolbox for kinematic and dynamic modeling and analysis of the high degree‐of‐freedom (DOF), redundant serial robots used widely in cooperative and space applications. With the Advanced Robotics Analysis Toolbox (ARAT), kinematic and dynamic modeling and analysis of the complex, high DOF, serial robots which may have universal, spherical, prismatic, or rotational joints with more than one DOF and a mobile or stationary base can be easily accomplished. The ARAT was used to design and analyze different complex structures of serial robots for robotic education students and robotics researchers who design and build exceptional new robots. The robot's kinematic and dynamic parameters including link lengths, directions, masses and inertias can be entered into the ARAT using a user‐friendly interface. Solid models of the robots can be created in a three dimensional (3D) environment for virtual reality simulations. In the ARAT, forward and inverse kinematic models, Jacobian matrix, trajectory planning, forward and inverse dynamic models can be produced in a computationally efficient way. All of the physical robot parameters such as angular and linear velocities, accelerations, forces, and torques at the joints, link origins and the center of mass of the links can be computed in 3D. The ARAT includes support for the most commonly used trajectory algorithms in serial robots, including polynomial, trigonometric (harmonic, cycloidal, elliptic), exponential, Gaussian, and Fourier‐based (Gutman, Freudenstein). These trajectories can be applied easily to each joint of the robots. To compare the kinematic and dynamic results obtained from ARAT and MATLAB‐Simscape Multibody simulation program, different structures of the serial robots were simulated in both programs. The results that produced from ARAT and MATLAB‐Simscape were similar. The ARAT is much better from the serial robot simulation toolboxes existing in literature in terms of computation capability, visual ability, and easy usage.

Robot dynamics: A recursive algorithm for efficient calculation of Christoffel symbols

Christoffel symbols of the first kind are very important in robot dynamics. They are used for tuning various proposed robot controllers, for determining the bounds on Coriolis/Centrifugal matrix, for mathematical formulation of optimal trajectory calculation, among others. In the literature of robot dynamics, Christoffel symbols of the first kind are calculated from Lagrangian dynamics using an off-line generated symbolic formula. In this study we present a novel and efficient recursive, non-symbolic, method where Christoffel symbols of the first kind are calculated on-the-fly based on the inertial parameters of robot’s links and their transformation matrices. The proposed method was analyzed in terms of execution time, computational complexity and numerical error. Results show that the proposed algorithm compares favorably with existing methods.

Prediction Algorithm of Parameters of Toe Clearance in the Swing Phase.

The adaptive control of gait training robots is aimed at improving the gait performance by assisting motion. In conventional robotics, it has not been possible to adjust the robotic parameters by predicting the toe motion, which is considered a tripping risk indicator. The prediction of toe clearance during walking can decrease the risk of tripping. In this paper, we propose a novel method of predicting toe clearance that uses a radial basis function network. The input data were the angles, angular velocities, and angular accelerations of the hip, knee, and ankle joints in the sagittal plane at the beginning of the swing phase. In the experiments, seven subjects walked on a treadmill for 360 s. The radial basis function network was trained with gait data ranging from 20 to 200 data points and tested with 100 data points. The root mean square error between the true and predicted values was 3.28 mm for the maximum toe clearance in the earlier swing phase and 2.30 mm for the minimum toe clearance in the later swing phase. Moreover, using gait data of other five subjects, the root mean square error between the true and predicted values was 4.04 mm for the maximum toe clearance and 2.88 mm for the minimum toe clearance when the walking velocity changed. This provided higher prediction accuracy compared with existing methods. The proposed algorithm used the information of joint movements at the start of the swing phase and could predict both the future maximum and minimum toe clearances within the same swing phase.

АППРОКСИМАЦИЯ РАБОЧЕЙ ОБЛАСТИ МАНИПУЛЯТОРОВ ПАРАЛЛЕЛЬНОЙ И ПОСЛЕДОВАТЕЛЬНОЙ СТРУКТУРЫ В СОСТАВЕ МУЛЬТИРОБОТИЗИРОВАННОЙ СИСТЕМЫ

The article describes the application of optimization algorithms for solving the problem of determining the workspace of robots as a serial and parallel structure based on the tripod. The method of approximating the set of solutions of nonlinear inequalities system describing constraints on the geometric parameters of the robot and based on the concept of non-uniform coverings is considered. The internal approximations defined as a set of parallelepipeds are obtained on the basis of the method. The influence of various geometric parameters on the volume of the workspace of the robot is analyzed. To approximate the workspace, the developed algorithm and its modifications with different dimensions of parallelepipeds and approaches to the transfer of constraints from the space of input to the space of output coordinates due to the complexity of the computational problem are used. A software package in the C ++ language is developed to implement the algorithms. The results of mathematical modeling are presented. Various dimensions of the grid to calculate the functions, as well as the accuracy of the approximation are experimentally conducted. The obtained results can be used in the selection of geometric parameters of robots, which determine their limitations when moving as part of a multi-robotic system.

The use of the NX mechatronic module to simulate of a simple machine work

Mechatronic is combination of three main disciplines like mechanic, electronic and theory of control. CAD/CAM systems is part of them. The aim of this article is to describe how to use CAD system (NX Siemens) with mechatronic module to designee simulation process. That module allows to resolve problems from mechanical, electrical and automation discipline. As an example author creates simple machine using this module. That aim was established in that form has been obtained. The created simulation is working and allowing to resolve mechanical robot’s problems. The simulation was based on kinematics parameters of robot. The article is the introduction to further work on the use of the Mechatronics module to perform the most real simulation of the Fanuc ARC Mate 100iB industrial robot.

Robust Regressor-Free Control of Rigid Robots Using Function Approximations

This paper develops a novel regressor-free robust controller for rigid robots whose dynamics can be described using the Euler–Lagrange equations of motion. The function approximation technique (FAT) is used to represent the robot’s inertia matrix, the Coriolis matrix, and the gravity vector as finite linear combinations of orthonormal basis functions. The proposed controller establishes a robust FAT control framework that uses a fixed control structure. The control objectives are to track reference trajectories in worst case scenarios where the robot dynamics are too costly to develop or otherwise unavailable. Detailed stability analysis via Lyapunov functions, the passivity property, and continuous switching laws shows uniform ultimate boundedness of the closed-loop dynamics. The simulation results of a three-degree-of-freedom (DOF) robot when the robot parameters are perturbed from their nominal values show good robustness of the proposed controller when compared with some well-established control methods. We also demonstrate success in the real-time experimental implementation of the proposed controller, which validates practicality for real-world robotic applications.

Modeling and Mechanical Analysis of Snake Robots on Cylinders

Abstract The narrow and redundant body of the snake robot makes it suitable for the inspection of complex bar structures, such as truss or tree structures. One of the key issues affecting the efficient motion of snake robots in complex bar structures is the development of mechanical models of snake robots on cylinders. In other words, the relationship between the payload and structural and performance parameters of the snake robot is still difficult to clarify. In this paper, the problem is approached with the Newton–Euler equations and the convex optimal method. Firstly, from the kinematic point of view, the optimal attitude of the snake robot wrapped around the cylinder is found. Next, the snake robot is modeled on the cylinder and transformed into a convex optimization problem. Then, the relationship between the payload of the snake robot on the cylinder and the geometric and attitude parameters of the body of snake robots is analyzed. Finally, the discussion for the optimal winding attitude and some advices for the design of the snake robot are proposed. This study is helpful toward the optimal design of snake robots, including geometry parameters and motor determination.

Wearable Sensors for Human–Robot Walking Together

Thanks to recent technological improvements that enable novel applications beyond the industrial context, there is growing interest in the use of robots in everyday life situations. To improve the acceptability of personal service robots, they should seamlessly interact with the users, understand their social signals and cues and respond appropriately. In this context, a few proposals were presented to make robots and humans navigate together naturally without explicit user control, but no final solution has been achieved yet. To make an advance toward this end, this paper proposes the use of wearable Inertial Measurement Units to improve the interaction between human and robot while walking together without physical links and with no restriction on the relative position between the human and the robot. We built a prototype system, experimented with 19 human participants in two different tasks, to provide real-time evaluation of gait parameters for a mobile robot moving together with a human, and studied the feasibility and the perceived usability by the participants. The results show the feasibility of the system, which obtained positive feedback from the users, giving valuable information for the development of a natural interaction system where the robot perceives human movements by means of wearable sensors.

Adaptive fault‐tolerant control of mobile robots with actuator faults and unknown parameters

This study deals with the fault-tolerant control problem for a class of two independent wheeled mobile robot systems with actuator faults and unknown robot parameters. Partial loss of control effectiveness and bias-actuator faults are addressed without knowing eventually faulty information of actuators. Adaptive schemes are developed to estimate unknown faulty parameters of actuator faults and unknown robot parameters of viscous friction factor and driving gain. Then, the backstepping control technique is utilised to construct the state feed-back control strategy based on the adaptive estimations. By using the Lyapunov stability theory, it is shown that the forward speed and azimuthal angle of wheeled mobile robots can track the given trajectory asymptotically in the case of actuator faults and unknown parameters. The effectiveness of the proposed designs is illustrated via a mobile robot system.

Optimum Utilization of Energy Consumption in Arm Robot

This paper introduced on how to minimize the energy and performance of arm robot. The objective is to design the optima; performance of the arm robot movement in performing certain tasks. There are three process involved in minimize the energy which are hardware assembly selection, Denavit Haternberg (D-H) parameters and optimization process of robot movements. A 3 degree of freedom ROB0036 robot arm is use as hardware selection. Then determine the Denavit Haternberg (D-H) parameters for robot through theoretical, simulation and practical forward and inverse kinematics. The optimization process involved how to control parameters know as position angle and the speed of motor of three main axes of arm robot. The performance is measured respect to the two movement, which are reference and optimized. The energy efficiency analysis is performs to reduce this energy consumed. The simulation resulted show that the minimum motor’s movement of joint, the less time taken to achieve of to complete the pick and place task. Directly, it results on less energy used and increase the robot arm performance.

A Novel Hybrid Control Strategy for an Underactuated 3-D Biped with Asymmetric Structure

In reality, due to the manufacturing error or the component loss in the service process, the structural parameters of bipedal robots may exhibit asymmetry. In this work, we consider the stable walking of an underactuated 3-D bipedal robot with asymmetric structure, and a novel hybrid control strategy is proposed. The control strategy consists of a continous heuristic motion controller, which asymptotically drive the state of the robot to the zero dynamics manifold, and an event-based feedback controller that renders the hybrid zero dynamics locally asymptotically stable. The heuristic motion controller uses heuristic state variables as controlled variables rather than simply the actuated variables, and the controller parameters of the event-based feedback controller are designed in an analytical method rather than relying on the left–right symmetry property. The effectiveness of the presented control strategy is illustrated by a numerical simulation example.

Kinematic calibration of serial robot using dual quaternions

Purpose The purpose of this paper is to propose an error model for serial robot kinematic calibration based on dual quaternions. Design/methodology/approach The dual quaternions are the combination of dual-number theory and quaternion algebra, which means that they can represent spatial transformation. The dual quaternions can represent the screw displacement in a compact and efficient way, so that they are used for the kinematic analysis of serial robot. The error model proposed in this paper is derived from the forward kinematic equations via using dual quaternion algebra. The full pose measurements are considered to apply the error model to the serial robot by using Leica Geosystems Absolute Tracker (AT960) and tracker machine control (T-MAC) probe. Findings Two kinematic-parameter identification algorithms are derived from the proposed error model based on dual quaternions, and they can be used for serial robot calibration. The error model uses Denavit–Hartenberg (DH) notation in the kinematic analysis, so that it gives the intuitive geometrical meaning of the kinematic parameters. The absolute tracker system can measure the position and orientation of the end-effector (EE) simultaneously via using T-MAC. Originality/value The error model formulated by dual quaternion algebra contains all the basic geometrical parameters of serial robot during the kinematic calibration process. The vector of dual quaternion error can be used as an indicator to represent the trend of error change of robot’s EE between the nominal value and the actual value. The accuracy of the EE is improved after nearly 20 measurements in the experiment conduct on robot SDA5F. The simulation and experiment verify the effectiveness of the error model and the calibration algorithms.

Biologically-Inspired Learning and Adaptation of Self-Evolving Control for Networked Mobile Robots

This paper presents a biologically-inspired learning and adaptation method for self-evolving control of networked mobile robots. A Kalman filter (KF) algorithm is employed to develop a self-learning RBFNN (Radial Basis Function Neural Network), called the KF-RBFNN. The structure of the KF-RBFNN is optimally initialized by means of a modified genetic algorithm (GA) in which a Lévy flight strategy is applied. By using the derived mathematical kinematic model of the mobile robots, the proposed GA-KF-RBFNN is utilized to design a self-evolving motion control law. The control parameters of the mobile robots are self-learned and adapted via the proposed GA-KF-RBFNN. This approach is extended to address the formation control problem of networked mobile robots by using a broadcast leader-follower control strategy. The proposed pragmatic approach circumvents the communication delay problem found in traditional networked mobile robot systems where consensus graph theory and directed topology are applied. The simulation results and numerical analysis are provided to demonstrate the merits and effectiveness of the developed GA-KF-RBFNN to achieve self-evolving formation control of networked mobile robots.

Calculation of the controlled parameters of the 6-coordinate robot in the process of additive forming of products

The article is devoted to the investigation of the surface layer formation accuracy of engineering products by additive methods. The analysis of advantages and disadvantages of layered products synthesis technologies was carried out. It was revealed that, in additive shaping, the exact characteristics of the surface layer differ significantly from the accuracy characteristics of the surface layer of products obtained by the traditional methods. The analysis of domestic and foreign works on the topic of research was carried out. It is revealed that to increase the accuracy characteristics of products obtained by additive methods, it is necessary to realize dynamically the spatial orientation of the working element of the additive installation in the process of shaping. To control the spatial orientation of the working organ of additive equipment, a method is proposed. According to the proposed method, the controlled parameters of the additive installation are calculated on the basis of a 6-coordinate robot. The proposed methodology will allow to calculate the controlled parameters of the process equipment, to provide the required orientation of the working element of the additive installation to reduce the error of shaping (approximation), using 6-axis positioning mechanisms.