Hybrid Kinematics Research Articles

Construction and forward kinematics of a novel reconfigurable parallel mechanism

In this paper, a kind of hybrid kinematics chain with variable constraints is constructed by using a 6R spatial bifurcated chain and 4-DOF serial limbs, by using them, a 3-DOF Reconfigurable Parallel Mechanisms (RPM) was constructed, which has four motion modes: 3T, 2T1R, 2R1T, and 3R motion modes. Using screw theory, the change of wrench system in the hybrid kinematics chain caused by the reconfiguration of the 6R bifurcated chain is analyzed, which affects the wrench system of the moving platform (MP), and thus causes the reconfiguration of the parallel mechanism (PM). The triangular pyramid fixed to the MP was found as auxiliary geometry and used to intuitively describe the constraint relationship between joint axes in limbs. The latter was used to establish a unified forward kinematics model of the RPM in four motion modes. The general forward kinematics solution procedure for this type of RPM is given. The overall Jacobian matrix was obtained by screw theory for singularity analysis. The condition number of the Jacobian matrix measures the degree to which the mechanism is close to the singular configuration. Based on the Monte Carlo simulation, point cloud images representing the workspace of RPM were obtained.

Vehicle State and Bias Estimation Based on Unscented Kalman Filter with Vehicle Hybrid Kinematics and Dynamics Models

Vehicle State and Bias Estimation Based on Unscented Kalman Filter with Vehicle Hybrid Kinematics and Dynamics Models

Workspace Characterization for Hybrid Tendon and Ball Chain Continuum Robots.

Continuum robots have attracted considerable attention for applications in minimally invasive diagnostics and therapeutics over the past decade [1]. The primary reason is their ability to navigate narrow and tortuous anatomical passageways, while guaranteeing safe inter- action with the anatomy. In designing such robots, an important goal is create a robot with a workspace appropriate for the clinical task. A significant limitation of many continuum designs re- lates to the minimum radius of curvature that a particular design can achieve. While multiple bending sections can be concatenated to provide more degrees of freedom, the orientations by which a point in the workspace can be approached are often limited. To overcome this limitation, this paper investigates a hybrid design that combines the advantages of tendon- actuated [2] and magnetic ball chain robots [3] as shown in Fig. 1. In this hybrid design, a proximal tendon- actuated section positions the robot with respect to the goal tip location while a distal ball chain section orients the robot tip with respect to the goal location. This abstract describes how the hybrid kinematics can be modeled and illustrates how the hybrid design possesses a dextrous workspace of finite extent.

A unified modeling and trajectory planning method based on system manipulability for the operation process of the legged locomotion manipulation system

AbstractFlexibility is one of the most significant advantages of legged robots in unstructured environments. However, quadruped robots cannot interact with environments to complete some manipulation tasks. One effective way is to load a manipulation arm. In this paper, we exhibit a quadruped locomotion manipulation system (LMS) named HITPhanT. This system comprises a quadruped locomotion platform and a six-degree-of-freedom manipulation arm. Besides, when the LMS moves to a designated position for operation, it is necessary to constrain the foot contact points to avoid sliding. Therefore, the foot contact point is regarded as a spherical hinge. So the locomotion platform can be considered as a parallel mechanism. A hybrid kinematics model is established by considering the serial robotic arms connecting this parallel mechanism. Besides, the trajectory planning method, which improves the system’s manipulability in evaluating the system balance, is also proposed. Finally, corresponding experiments verify the overall system’s stabilization and algorithm’s effectiveness.

Towards fluid force estimation of a water‐jetting aerial robot with hybrid kinematics‐force model

AbstractIn this paper, a three‐dimensional hybrid kinematics‐force (HKF) model for fluid force estimation coupled with position optimization of an aerial robot capable of high‐pressure fluid ejection is presented. Motivated by the archerfish's unique (water‐jetting) hunting mechanics, the HKF model comprises of two sub‐models (hybrid kinematics and fluid force estimation) to maintain a specific fluid force at the point‐of‐contact (POC) during high altitude fluid jetting for high‐risk maintenance (cleaning) scenarios. Industries with high‐risk cleaning applications seek to employ robots to assist cleaners in routine operations on infrastructures or equipment at a height such as photovoltaic e‐glasses, impact‐sensitive objects, and many others. For a fluid jet, the stand‐off distance represents the length of the fluid trajectory between the nozzle orifice and POC, and is also a vital variable in fluid force control. If the stand‐off distance between the ejection source and the target is large, the fluid stream loses energy along the trajectory and the force at the POC is weakened thus losing some of the jet pressure at the target surface. The HKF model exploits this by estimating and maintaining a specific force at the POC through position optimization of the onboard nozzle coupled with the knowledge of the fluid parameters. To innovate high structure cleaning, the HKF model can be employed on an aerial robot with fluid ejection capabilities for accurate fluid force control at the POC. For high‐pressure fluid ejection (on horizontal and vertical structures), the HKF model is able to predict the (high pressure) fluid force at the POC with less than 10% error. The proposed HKF model is tested and verified through simulations and the experimentation results are validated by flying the physical prototypes in actual deployment scenarios.

Razvoj sistema za programiranje i simulaciju 4-osnog robota sa hibridnom kinematikom

This paper presents an approach for developing the programming and offline simulation systems for low-cost industrial robots in the MatLab/Simulink environment. The approach is presented in the example of a virtual model of a 4-axis robot with hybrid kinematics intended for manipulation tasks. The industrial robot with hybrid kinematics consists of the well-known 5R planar parallel mechanism to which two serial axes have been added. The programming system developed in a MatLab environment involves generating G-code programs based on given pick and place points. The virtual model included in the simulation system is configured in the Simulink environment based on the CAD model of the robot and its kinematic structure. The kinematic model and the inverse kinematic problem have to be included in the virtual model to realize the motion of the virtual robot. The system of programming and simulation has been verified through several examples that include object manipulation to perform various tasks.

Konfigurisanje nove edukacione mašine alatke na bazi mehanizma sa hibridnom kinematikom

The paper shows the configuration of a new educational machine based on hybrid kinematics mechanism. The concept of a three-axis O-X hybrid mechanism is described, consisting of a single serial translational axis and a two-axis parallel mechanism that can operate in two variants, with extended form O and crossed form X-joints of the parallel mechanism. The virtual prototype of the machine was configured in a CAD/CAM environment, where simulations of the mechanism's operation were performed. A programming system for machine has been prepared that also enables program verification. An open architecture control system based on the LinuxCNC platform has been configured for control of the machine. The trial work of the machine was performed in order to verify the realized prototype and control.

A Model-Based Online Reference Prediction Strategy for Model Predictive Motion Cueing Algorithms

Interactive driving simulation has become a key technology to support the development and optimization process of modern vehicle components and driver assistance systems both in academic research and in the automotive industry. However, the validity of the results obtained within the virtual environment depends essentially on the adequate reproduction of the simulated vehicle movements and the corresponding immersion of the driver. For that reason, specific motion platform control strategies, so-called Motion Cueing Algorithms (MCA), are used to replicate the simulated accelerations and angular velocities within the physical limitations of the driving simulator best possible. In this paper, we present a novel model-based approach to predict oncoming vehicle motion at runtime. For that purpose, a virtual driver model as well as a simplified vehicle dynamics model are introduced to estimate the future driver inputs and the resulting vehicle trajectories according to the current driving situation. This additional system knowledge enables control algorithms designed on the idea of Model Predictive Control (MPC) to exploit their potential more efficiently. The performance of the proposed prediction strategy is evaluated on the basis of measurement data from a real test run in comparison to an ideal prediction and a constant reference, using a hybrid kinematics motion system as an application example.

External Kinematic Calibration of Hybrid Kinematics Machine Utilizing Lower-DOF Planar Parallel Kinematics Mechanisms

This paper presents the implementation of nonlinear least squares and iterative linear least squares algorithms for external kinematic calibration of a hybrid kinematics machine composed of two 3PRR planar parallel kinematics mechanisms by utilizing a laser tracker. First the hand-eye and robot-world transformations were obtained by a separable closed-form solution and refined by the nonlinear least squares. Subsequently, the geometric parameters of the machine’s mechanisms were estimated using the two algorithms. Due to the rank deficiency, we implemented the nonlinear least squares algorithm through a subset selection approach in which we performed the estimation in two steps. We iterated the closed-form solution of the linear least squares until the solution converges to the actual values. We have shown that the nonlinear least squares algorithm successfully refined the hand-eye and robot-world transformations and outperformed the iterative linear squares algorithm in the estimation of the geometric parameters of the mechanisms.

Genetic and hybrid algorithms for optimization of non-singular 3PRR planar parallel kinematics mechanism for machining application

SUMMARYThis paper proposes a special non-symmetric topology of a 3PRR planar parallel kinematics mechanism, which naturally avoids singularity within the workspace and can be utilized for hybrid kinematics machine tools. Subsequently, single-objective and multi-objective optimizations are conducted to improve the performance. The workspace area and minimum eigenvalue, as well as the condition number of the homogenized Cartesian stiffness matrix across the workspace, have been chosen as the objectives in the optimization based on their relevance to the machining application. The single-objective optimization is conducted by using a single-objective genetic algorithm and a hybrid algorithm, whereas the multi-objective optimization is conducted by using a multi-objective genetic algorithm, a weighted sum single-objective genetic algorithm, and a weighted sum hybrid algorithm. It is shown that the single-objective optimization gives superior value in the optimized objective, while sacrificing the other objectives, whereas the multi-objective optimization compromises the improvement of all objectives by providing non-dominated values. In terms of the algorithms, it is shown that a hybrid algorithm can either verify or refine the optimal value obtained by a genetic algorithm.

Structural synthesis of five-degree-of-freedom hybrid kinematics mechanism

ABSTRACTThe structural synthesis of mechanisms is the prerequisite of mechanical design, thereby, it is necessary to formulate special care to be taken to the structural synthesis of mechanisms, especially for the type synthesis of hybrid kinematics mechanism (HKM). This paper presents a very simple and effective method of structural synthesis for HKM based on set theory. The basic concept and mathematical operation of GF set are first introduced. Based on a GF set, the principle of type synthesis for serial mechanisms, parallel mechanisms and HKM is presented, especially, a detailed algorithm of type synthesis for HKM is proposed as well. It is shown that type synthesis of HKM can be developed by the combination of elements of GF set and rotation axis movement theorem. In order to demonstrate the applicability of the type synthesis principle, the structural synthesis of five-degree-of-freedom HKM is given in detail. A further investigation shows that the structure of three-translational and two-rotational HKM only have one type , whereas, two-translational and three-rotational HKM can be categorised into two types, i.e. and .

Development of multifunctional reconfigurable desktop machine tool with hybrid kinematics

This paper presents a desktop reconfigurable machine tool with hybrid kinematics for four types machine tools, with a description of the applied mechanism and established a modular system for their configuring. The postprocessor for five-axis machining presented in this paper is applied to the kinematic structures with table-tilting with two rotations (B,C). Also are shown solving the position of actuators p1 and p2 when the machine works with hybrid kinematics. Verification of postprocessor is realized on virtual prototype in CAD/CAM environment and experimentally on an available 3-axis machine tool. Experimental results confirmed the configured postprocessor which can be used for programming machine tools.

Numerical controlled robot crawler: new resource for industries with large scale products

This paper introduces a novel mobile automation resource for industries with large scale products. The inherent challenges of large structures for an automation system are discussed and requirements for a mobile machine are derivated. Based on the kinematic investigation, a hybrid kinematic mechanical structure is developed to fulfill the requirements. The characteristics of hybrid kinematics especially for the kinematic transformation and the resulting advantages are introduced. The necessary adhesion system to enable a safe and reliable movement on different surfaces is described. Additionally, the control concept is presented and the intrinsic challenges of using an industrial machine tool control for a mobile robot are shown. Finally, first results of the experimental application are presented.

Hybrid undulatory kinematics of a robotic Mackerel (Scomber scombrus): Theoretical modeling and experimental investigation

Fishes that use undulatory locomotion occasionally change their inherent kinematics in terms of some natural behavior. This special locomotion pattern was vividly dubbed “hybrid kinematics” by biologists recently. In this paper, we employed a physical model with body shape of a Mackerel (Scomber scombrus), to use the three most typical undulatory kinematics: anguillform, carangiform and thunniform, to investigate the hydrodynamic performance of the so-called “hybrid kinematics” biological issue. Theoretical models of both kinematics and hydrodynamics of the physical model swimming were developed. Base on this model, the instantaneous force produced by fish undulatory body and flapping tail were calculated separately. We also quantitatively measured the hydrodynamic variables of the robotic model swimming with the three undulatory kinematics on an experimental apparatus. The results of both theoretical model and experiment showed that the robot with thunniform kinematics not only reaches a higher speed but also is more efficient during steady swimming mode. However, anguilliform kinematics won the speed race during the initial acceleration. Additionally, the digital particle image velocimetry (DPIV) results showed some difference of the wake flow generated by the robotic swimmer among the three undulatory kinematics. Our findings may possibly shed light on the motion control of a biomimetic robotic fish and provide certain evidence of why the “hybrid kinematics” exists within the typical undulatory locomotion patterns.

Quotient Kinematics Machines: Concept, Analysis, and Synthesis

Abstract This paper presents a geometric analysis and synthesis theory for quotient kinematics machines (QKMs). Given a desired motion type described by a subgroup G of the special Euclidean group SE(3), QKM refers to a left-and-right hand system that realizes G through the coordinated motion of two mechanism modules, one synthesizing a subgroup H of G, and the other a complement of H in G, denoted by G/H. In the past, QKMs were often categorized into hybrid kinematics machines (HKMs) and were treated on a case-by-case basis. We show that QKMs do have a unique and well-defined kinematic structure that permits a unified and systematic treatment of their synthesis and design. We also study the properties of G/H as a novel motion type for parallel kinematics machine (PKM) synthesis. Another contribution of the paper is to model five-axis machines by SE(3)/R(o,z) (where R(o,z) represents the spindle symmetry) and give a complete classification of five-axis QKMs using the same geometric framework.

Robust design and analysis of 4PUS–1RPU parallel mechanism for a 5-degree-of-freedom hybrid kinematics machine

Based on a proposed 4 degree-of-freedom (DOF) T2R2 parallel mechanism with the structural configuration of 4PUS–1RPU (4-prismatic–universal–spherical and 1-revolute–prismatic–universal), a 5-axis hybrid kinematics machine (HKM) can be developed with an additional linear motion being combined. The kinematic and dynamic performance indices for the 4-DOF parallel mechanism are developed. A novel improved RSM (response surface methodology)-based LKN (Latin hypercube design, Kriging interpolation, and neural network training) method, which is a generic robust design method for dealing with the computation-intensive engineering optimization problem, is developed in this paper. The robust design for the 4PUS–1RPU parallel mechanism by using both traditional RSM and the presented LKN method is carried out, where the first-order natural frequency is regarded as the single response objective, and the design results show that the LKN method is more effective than the traditional RSM. Based on the proposed LKN method the robust design for the 4PUS–1RPU parallel mechanism with consideration of both kinematic and dynamic performance indices is carried out. The characteristics of the robust optimal scheme are analysed in detail. The prototype of the HKM with the parameters obtained from the robust design scheme is developed, and the machining experiments show that the proposed HKM can implement the 5-axis machining with the structural and cross-sectional parameters that are much more robust and optimal.

Inverse Dynamic Model and a Control Application of a Novel 6-DOF Hybrid Kinematics Manipulator

Kinematics with six degrees of freedom can be of several types. This paper describes the inverse dynamic model of a novel hybrid kinematics manipulator. The so-called Epizactor consists of two planar disk systems that together move a connecting element in 6 DOF. To do so each of the disk systems has a linkage point equipped with a homokinetic joint. Each disk system can be described as a serial 3-link planar manipulator with unlimited angles of rotation. To compensate singularities, a kinematic redundancy is introduced via a fourth link. The kinematic concept leads to several technical advantages for compact 6-DOF-manipulators when compared to established parallel kinematics: The ratio of workspace volume and installation space is beneficial, the number of kinematic elements is smaller, and rotating drives are used exclusively. For a singularity-robust control-approach, the inverse dynamic model is derived using the iterative Newton---Euler-method. Feasibility is shown by the application of the model to an example where excessive actuator velocities and torques are avoided.

Stiffness of 5-axis machines with serial, parallel, and hybrid kinematics: Evaluation and comparison

Introduction of parallel kinematics mechanisms in structures of modern machine tools results in resumed development and investigation of stiffness performance indexes. In this paper, a new stiffness-related engineering index – minimum collinear stiffness value (CSV) – is applied for stiffness evaluation of machine tools with different kinematics types. The evaluation embraces both local stiffness values in a given configuration and global stiffness features over all workspace. A dimensionless form is entered as the ratio of the CSV to the stiffness value of a single actuator. Stiffness features of 5-axis machines with serial, parallel, and tripod-based hybrid kinematics are simulated using the developed approach.

Hybrid kinematics machine tool for drilling applications: precision prediction using advanced software tools

We present a new approach for precision prediction of parallel kinematics machine tools by virtual prototyping (VP) using advanced software tools. VP modelling and kinematics simulation using MSC/ADAMS was carried out for the proposed parallel drilling module mounted on a serial milling machine base, to perform a 3-PRS-PP hybrid-mechanism-based machine tool. The related kinematic analysis, such as the displacement and velocity analysis of the drilling tool end, the rotation angle analysis of the ball joints, the linear movements of the prismatic joints, is obtained. Kinematics analyses and simulations were carried out with and without manufacturing and assembly deviations. The effects of deviations on machine performances were analysed using two-dimensional probability distribution analysis. We present the application of a virtual prototype simulation approach in the parametric design process, structural design and error budget determination for new types of machine tools.

Fast reacting maintenance of forming tools with a transportable machining unit

In sheet metal forming damages of the free formed tool surfaces occur due to wear or foreign bodies. Fast reacting maintenance is necessary to avoid bottlenecks in workpiece supply of subsequent production steps. A transportable hybrid kinematics machining unit has been developed for repair processing of metal forming tools near the production line. This paper describes strategies to improve the positioning accuracy of the machining unit and methods for optimised surface digitising with an integrated touch probe. Calibration of the hybrid kinematics is based on an enhanced kinematics model which allows the description of geometric errors, compliance and thermal effects.