Kinematics Of Parallel Robot Research Articles

Accuracy of a hexapod parallel robot kinematics based external fixator.

Different hexapod-based external fixators are increasingly used to treat bone deformities and fractures. Accuracy has not been measured sufficiently for all models. An infrared tracking system was applied to measure positioning maneuvers with a motorized Precision Hexapod® fixator, detecting three-dimensional positions of reflective balls mounted in an L-arrangement on the fixator, simulating bone directions. By omitting one dimension of the coordinates, projections were simulated as if measured on standard radiographs. Accuracy was calculated as the absolute difference between targeted and measured positioning values. In 149 positioning maneuvers, the median values for positioning accuracy of translations and rotations (torsions/angulations) were below 0.3 mm and 0.2° with quartiles ranging from -0.5 mm to 0.5 mm and -1.0° to 0.9°, respectively. The experimental setup was found to be precise and reliable. It can be applied to compare different hexapod-based fixators. Accuracy of the investigated hexapod system was high.

Estimation-based ILC applied to a parallel kinematic robot

Estimation-based iterative learning control (ILC) is applied to a parallel kinematic manipulator known as the Gantry–Tau parallel robot. The system represents a control problem where measurements of the controlled variables are not available. The main idea is to use estimates of the controlled variables in the ILC algorithm, and in the paper this approach is evaluated experimentally on the Gantry–Tau robot. The experimental results show that an ILC algorithm using estimates of the tool position gives a considerable improvement of the control performance. The tool position estimate is obtained by fusing measurements of the actuator angular positions with measurements of the tool path acceleration using a complementary filter.

Kinematic Analysis of 5-UPS Parallel Machine Tool Based on Adams

In this paper, the kinematics of 5-UPS parallel machine tool is analyzed, and a kinematic analysis method combining kinematic analysis and computer kinematics software is proposed. Under the premise that the parallel machine tool sector parameters is known, firstly we use the vector method to establish a mathematical model of inverse kinematics, and in accordance with a U-shaped processing trajectory the inverse solution is calculated; Secondly, three-dimensional model of the parallel machine tool is modeled in Adams, and kinematic constraints are set correctly; Finally, the inverse kinematics solution of the mathematical model is used as the Adams drive input, then the positive solutions is carried out. Compared through the Adams simulation results with U-machining path, it is verified that the inverse solution of the mathematical model and parallel machine tool bodies both are correct, it has certain significance for Parallel machine tools and other parallel robot kinematics analysis.

Forward Kinematics of Parallel Robot Based on Neuro-Fuzzy System

As the structure of parallel robot is special in general mechanical and electrical systems, its forward kinematics needs to be solved by nonlinear equations. In this paper, for the issue that numerical iterative method requires complex mathematical derivation and programming, and is sensitive to the initial value, a Neuro-fuzzy system is proposed for solving forward kinematics model of parallel robot. Meanwhile, inverse kinematics is used for training database, knowledge representation ability of fuzzy theory and self-learning ability of neural network are combined to overcome the shortcomings that neural network cannot express human language and fuzzy system do not have self-learning ability. In addition, training and generation efficiency of the model can also be improved by reducing the input dimension reasonably. Simulation results have been showed that, in the premise of efficiency, accuracy of forward kinematics model using Neuro-fuzzy system is better than Newton-Raphson iterative method, and has better versatility.

산업용 소형 고속병렬로봇의 구조해석에 관한 연구

These days, the interests on the high speed handling robots are increasing because it is important to get down the unit cost of production to get the price competitiveness. The parallel kinematic mechanism is more suitable to implement the high speed robot system as well known. The moving parts of the high speed parallel robot have to be designed for light weight. But the vibration motion is induced by the light weight links because they drive in high acceleration and deceleration. In this reason, the structural analysis of the high speed parallel kinematic robot is very important in the design process. In this paper, the study on the structural analysis of a high speed parallel robot has been done and the research results will be introduced.

Forward Kinematics of Six-DOF Parallel Robot Based on Adaptive Differential Evolution

Parallel robot inverse kinematics solution is relatively easier to obtain than forward kinematics forward, this paper assumes that the forward kinematics of six-DOF parallel robot is given then using the kinematics inverse solution to approximate the forward solution. To improve efficiency and stability of the approximation, an adaptive parameters differential evolution algorithm is proposed and applied to the forward kinematics problem. The experimental results show that the modified algorithm can gain the forward kinematics of parallel robot efficiently.

Convenient Model Inversion by means of Object-Oriented Modeling for a Parallel Kinematic Robot

AbstractThe paper presents the capability of object-oriented modeling languages to obtain inverse plant models almost automatically by means of Modelica and the simulation tool Dymola. Based on an available plant model in Modelica the construction of its inverse model is shown with focus on new blocks from the free Modelica Standard Library (Version 3.2). This method is applied to a model of a six degrees of freedom (DOF) parallel kinematic robot that should be implemented in a so called inverse disturbance observer (IDOB) control architecture.

Towards Washout Filter Concepts for Motion Simulators on the Base of a Stewart Platform

AbstractIn this paper we present a pneumatically driven Stewart platform as a basis for motion simulators. Motion platforms, that simulate perceived situations in aeroplanes, cars or ships, have workspace constraints in every degree of freedom. Therefore it is necessary to adapt the accelerations and angular rates in order to stay within the physical restrictions.For realizing a flight or ride simulator on the basis of the Stewart platform, “ Washout Filters” are used to change the signals of the open source software FlightGearand to minimize the sensation error between simulator and aircraft. Different filter concepts are implemented and evaluated.The platform presented in this document is a parallel kinematic robot, driven by fluidic muscles. The pneumatically actuated muscles are only able to produce tensile forces. Therefore a spiral spring from a passenger car is used to apply the compressive forces and torques. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Error Comparison and Analysis of Parallel and Constraint Mechanism for 3-TPS Hybrid Machine Tool

This paper establishes position error model based on parallel robot kinematics theory, and analyses position error of the 3-TPS hybrid machine tool. Firstly, to calculate position error of the movable plate caused by the parallel mechanism links, through error model of the parallel mechanism which is established through inverse kinematics of the hybrid machine tool. Then, according to the error model of constraint mechanism established by transformation matrix method, the position error has been simulated and calculated. Finally, this paper compares the effects of both mechanisms. The analysis indicates the link error of constraint mechanism has more influence on movable plate posture than parallel mechanism, and provides help with motion error compensation and kinematic calibration.

APIS — A miniaturized robot for precision assembly with low-cost piezoelectric motors

This paper deals with the requirements for and the realization of a miniaturized parallel kinematic robot named APIS, which is driven by low-cost piezoelectric motors and thus designed for low-cost applications. After the need and potentials of this concept have been clarified, a detailed description of the development process is given. In doing so, kinematic aspects as well as the driving concept and the robot control, including the development of a suitable motor control with power stage, are described. In addition to the first functional prototype some performance measurements are presented, which show that the robot is able to obtain a repeatability of less than 34 μm. To provide better results, possibilities for future developments are identified, including optimized sensor feedback and motion control.

Observer-based ILC Applied to the Gantry-Tau Parallel Kinematic Robot

AbstractThree approaches of iterative learning control (ILC) applied to a Gantry-Tau parallel kinematic robot are studied; ILC algorithms using 1) measured motor angles, 2) tool-position estimates, and for evaluation purposes, 3) measured tool position. The approaches are compared experimentally, with the tool performance evaluated using external sensors. It is concluded that the tool performance can be improved using tool-position estimates in the ILC algorithm, compared to when using motor-angle measurements. Applying ILC algorithms to a system following trajectories with so-called lead-in/lead-out is also considered in the paper.

Closed-form forward kinematics solutions of a 4-DOF parallel robot

It is well known that the forward kinematics of parallel robots is a very difficult problem. Closed-form forward kinematics solutions have been reported only to a few special classes of parallel robots. This paper presents closed-form forward kinematics solutions of a 4-DOF parallel robot H4. A 16th order polynomial in a single variable is derived to solve the forward kinematics of the H4. The 16 roots of the polynomial lead to at most 16 different forward kinematics solutions. A numerical verification is also presented.

A new method to solve robot inverse kinematics using Assur virtual chains

SUMMARYThis paper describes a numerical algorithm to solve the inverse kinematics of parallel robots based on numerical integration. Inverse kinematics algorithms based on numerical integration involve the drift phenomena of the solution; as a consequence, errors are generated when the end-effector location differs from that desired. The proposed algorithm associates a novel method to describe the differential kinematics with a simple numerical integration method. The methodology is presented in this paper and its exponential stability is proved. A numerical example and a real application are presented to outline its advantages.

Present and future robot control development—An industrial perspective

Robot control is a key competence for robot manufacturers and a lot of development is made to increase robot performance, reduce robot cost and introduce new functionalities. Examples of development areas that get big attention today are multi robot control, safe control, force control, 3D vision, remote robot supervision and wireless communication. The application benefits from these developments are discussed as well as the technical challenges that the robot manufacturers meet. Model-based control is now a key technology for the control of industrial robots and models and control schemes are continuously refined to meet the requirements on higher performance even when the cost pressure leads to the design of robot mechanics that is more difficult to control. Driving forces for the future development of robots can be found in, for example, new robot applications in the automotive industry, especially for the final assembly, in small and medium size enterprises, in foundries, in food industry and in the processing and assembly of large structures. Some scenarios on future robot control development are proposed. One scenario is that light-weight robot concepts could have an impact on future car manufacturing and on future automation of small and medium size enterprises (SMEs). Such a development could result in modular robots and in control schemes using sensors in the robot arm structure, sensors that could also be used for the implementation of redundant safe control. Introducing highly modular robots will increase the need of robot installation support, making Plug and Play functionality even more important. One possibility to obtain a highly modular robot program could be to use a recently developed new type of parallel kinematic robot structure with large work space in relation to the robot foot print. For further efficient use of robots, the scenario of adaptive robot performance is introduced. This means that the robot control is optimised with respect to the thermal and fatigue load on the robot for the specific program that the robot performs. The main conclusion of the presentation is that industrial robot development is far away from its limits and that a lot of research and development is needed to obtain a more widely use of robot automation in industry.

Continuation method applied in kinematics of parallel robot

Continuation method applied in kinematics of parallel robot

CONTINUATION METHOD APPLIED IN KINEMATICS OF PARALLEL ROBOT

Continuation method solving forward kinematics problem of parallel robot was discussed. And through a coefficient-parameter continuation method the efficiency and feasibility of continuation method were improved. Using this method all forward solutions of a new parallel robot model which was put forward lately by Robot Open Laboratory of Science Institute of China were obtained. Therefore it provided the basis of mechanism analysis and real-time control for new model.

4546803 Relief means for the drive mechanisms of components alternatingly rocking between two end positions : Peter Dornier, Lindau, Federal Republic Of Germany assigned to Lindauer Dornier Gesellschaft mbH

A manipulator model for use in a design process of the mechanics is shown in this paper. The target is to minimize deformation and vibration in application and the focus is to model manipulator components and merge them in a manipulator model. This approach is applied to a six degree of freedom serial kinematic robot with rotational joints. Besides serial kinematic robots, this approach will also be applicable to parallel kinematic robots. The proposed model uses the Floating Frame of Reference approach for modeling the structural parts of the manipulator. The stiffness modeling of bearings is introduced. Electric drives generate the motion of the rotational joints, which is transported to the rotational joint via a drivetrain. In the first step, a simple drivetrain model is derived. The required electric power is transmitted by the cabling of the manipulator. Depending on the mounting of the cables, the stiffness of the cable contributes to the manipulator stiffness. For this case, a cable stiffness model is presented. All components of a manipulator must be fixed and held together. This is ensured by bolted joints and therefore the bolted joints also contribute to the system dynamics of the robot. An approach to consider the stiffness of bolted joints is presented. Finally, the component-oriented total manipulator model is validated with a static compliance measurement.