Inverse kinematics of a heavy duty manipulator with 6-DOF based on dual quaternion

An iterative method is introduced successfully to solve the inverse kinematics of a 6-DOF manipulator of a tunnel drilling rig based on dual quaternion, which is difficult to get the solution by Denavit-Hartenberg(D-H) based methods. By the intuitive expression of dual quaternion to the orientation of rigid body, the coordinate frames assigned to each joint are established all in the same orientation, which does not need to use the D-H procedure. The compact and simple form of kinematic equations, consisting of position equations and orientation equations, is also the consequence of dual quaternion calculations. The iterative process is basically of two steps which are related to solving the position equations and orientation equations correspondingly. First, assume an initial value of the iterative variable; then, the position equations can be solved because of the reduced number of unknown variables in the position equations and the orientation equations can be solved by applying the solution from the position equations, which obtains an updated value for the iterative variable; finally, repeat the procedure by using the updated iterative variable to the position equations till the prescribed accuracy is obtained. The method proposed has a clear geometric meaning, and the algorithm is simple and direct. Simulation for 100 poses of the end frame shows that the average running time of inverse kinematics calculation for each demanded pose of end-effector is 7.2 ms on an ordinary laptop, which is good enough for practical use. The iteration counts 2-4 cycles generally, which is a quick convergence. The method proposed here has been successfully used in the project of automating a hydraulic rig.

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.

Robot inverse kinematics based on FCM and fuzzy-neural network

Presents a fast and effective method proposed by combining the fuzzy C means (FCM) and the fuzzy neural network for solving robot inverse kinematics, and its successful application to the robot inverse kinematics and concludes from simulation results that this new method not only has high efficiency and accuracy, but also good generalization, and it also overcomes the "dimension disaster" of fuzzy set in a fuzzy neural network fairly well.

Design,fabrication and kinematics of a bio-inspired robotic bat wing

The current work is oriented toward the development of a novel biologically inspired bat aerial robot with morphing wings. Based on the flight characteristics data of natural bats(Eptesicus fuscus), a novel four degrees of freedom robotic bat wing was developed to emulate the movements of bat wing. The design, fabrication, programing and wind tunnel experiments of the robot bat wing are described in this paper. Based on this robotic wing, the influence of flap amplitude, wind speed, flight frequency, downstroke ratio and stroke plane angle as well as the contributions of flap, elbow, sweep and wrist motions on the aerodynamic force and mechanical power were studied and analyzed. Results of wind tunnel experiments validated that higher lift would bring greater power consumption, and the flap motion would generate the most force and need more energy expenditure compared with other motions of bat. The experimental results suggest that the flap and fold motions are indispensable to make a robotic bat wing that has a better flight performance. This study provides some implications and a better understanding for the future robotic bat.

Using a 3D Interval Type-2 Fuzzy Interpolation System to Improve Modeless Robots Measurement and Calibration Accuracy

This paper is an extended research for a novel technique used in the pose error compensations of the robot and manipulator calibration process based on an IT2FEI （interval type-2 fuzzy error interpolation） method. Robot calibrations can be classified into model-based and modeless methods. A model-based calibration method normally requires that the practitioners understand the kinematics of the robot therefore may pose a challenger for field engineers. An alternative yet effective means for robot calibration is to use a modeless method; however with such a method there is a conflict between the calibration accuracy of the robot and the number of grid points used in the calibration task. In this paper, an interval type-2 fuzzy interpolation system is applied to improve the compensation accuracy of the robot in its 3D workspace. An on-line type-2 fuzzy inference system is implemented to meet the needs of on-line robot trajectory planning and control. The simulated results given in this paper show that not only robot compensation accuracy can be greatly improved, but also the calibration process can be significantly simplified, and it is more suitable for practical applications.

Structural Synthesis of 2T3R Hybrid Kinematic Mechanism Based on G_F Set

The structural synthesis of mechanisms is a prerequisite of mechanical design. Thereby, it is necessary to address special attention to the structural synthesis of mechanisms,especially for the structural synthesis of hybrid kinematic mechanisms( HKMs). This paper presents a very simple yet very effective method of structural synthesis for HKM based on the set theory. The basic concept and mathematical operation of Generalized Function Set( G_F set) are firstly introduced. Based on G_F set,a type synthesis principle for serial mechanisms,parallel mechanisms and HKMs is presented,respectively. 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 G_F setand rotation axis transfer theorem. In order to demonstrate the applicability of the type synthesis principle presented in the paper,structure synthesis of 2T3 R HKMs are accomplished,where T and R denote translational and rotational degree-of-freedom( DoF),respectively. And further research shows that the structures of 2T3 R HKMs can be categorized into two types,i. e.,G(_F~Ⅰ) and G(_F~Ⅱ).

A Geometric Approach to the Design of Serial and Parallel Manipulators with Passive Joints

The use of robotic manipulators in remote and sensitive areas calls for more robust solutions when handling joint failure, and the industry demands mathematically robust approaches to handle even the worst case scenarios. For both serial and parallel manipulators torque failure is indeed a worst case scenario. Thus, a systematic analysis of the effects of external forces on manipulators with passive joints is presented. For serial manipulators we find under what conditions the robot is conditionally equilibrated, that is, equilibrated with respect to a specific external force. These conditions are, as expected, very restrictive. The serial, or subchain, case serves as a good platform for analyzing parallel manipulators. In parallel manipulators passive joints can appear as a design choice or as a result of torque failure. In both cases a good understanding of the effects that passive joints have on the mobility and motion of the parallel manipulator is crucial. We first look at the effects that passive joints have on the mobility of the mechanism. Then, if the mobility considering passive joints only is not zero we find a condition similar to the serial case for which the parallel manipulator is conditionally equilibrated with respect to a specific external force.

Robust model predictive tracking control for the wheeled mobile robot with boundary uncertain based on linear matrix inequalities

In this study,a robust model predictive controller is designed for the trajectory tracking problem of non-holonomic constrained wheeled mobile robot based on an elliptic invariant set approach.The controller is based on a time-varying error model of robot kinematics and uses linear matrix inequalities to solve the robust tracking problem taking uncertainties into account.The uncertainties are modelled by linear fractional transform form to contain both parameter perturbations and external disturbances.The control strategy consists of a feedforward term that drives the centre of the ellipse to the reference point and a feedback term that converges the uncertain system state error to the equilibrium point.The strategy stabilises the nominal system and ensures that all states of the uncertain system remain within the ellipsoid at each step,thus achieving robust stability of the uncertain system.Finally,the robustness of the algorithm and its resistance to disturbances are verified by simulation and experiment.

Optimization of Grasping Efficiency of a Robot Used for Sorting Construction and Demolition Waste

The recycling of construction and demolition waste(CDW)remains an urgent problem to be solved.In the industry,raw CDW needs to be manually sorted.To achieve high efficiency and avoid the risks of manual sorting,a sorting robot can be designed to grasp and sort CDW on a conveyor belt.But dynamic grasping on the conveyor belt is a challenge.We collected location information with a three-dimensional camera and then evaluated the method of dynamic robotic grasping.This paper discusses the grasping strategy of rough processed CDW on the conveyor belt,and implements the function of grasping and sorting on the recycling line.Furthermore,two new mathematical models for a robotic locating system are established,the accuracy of the model is tested with Matlab,and the selected model is applied to actual working conditions to verify the sorting accuracy.Finally,the robot kinematics parameters are optimized to improve the sorting efficiency through experiments in a real system,and it was concluded that when the conveyor speed was kept at around 0.25 m/s,better sorting results could be achieved.Increasing the speed and shortening the acceleration/deceleration time would reach the maximum efficiency when the load would allow it.Currently,the sorting efficiency reached approximately 2000 pieces per hour,showing a high accuracy.

Application of Parallel Mechanism in Varistructured Quadruped/Biped Human-carrying Walking Chair Robot

For the existing problems of walking chair robot such as simple function,lower bearing capacity and not walking in complex environment,a novel varistructured quadruped / biped human-carrying walking chair robot is proposed.The proposed robot could be used as biped and quadruped walking chair robots.Considering the conversion of the walking chair robot from the quadruped to the biped or vice versa,6-UPS and 2-UPS＋UP（U,P and S are universal joint,the prismatic pair,and sphere joint,respectively） parallel mechanisms are selected as the leg mechanism of the biped walking robot and quadruped walking robot,respectively.Combining the screw theory and theory of mechanism,the degrees of freedom of the leg mechanism and the body mechanism in diferent motion states are computed so as to meet the requirements of mechanism design.The motion characteristics of the 2-UPS＋UP parallel mechanism which is the key part of the walking chair robot are analyzed.Then,the workspace of the moving platform is drawn and the efect of the structural parameters on the workspace volume is studied.Finally,it is found that the volume of the workspace of the moving platform is bigger when the side length ratio and the vertex angle ratio of the fxed platform and the moving platform which are isosceles triangles are close to 1.This study provides a theoretical foundation for the prototype development.

Development of Wheel-less Snake Robot with Two Distinct Gaits and Gait Transition Capability

Snake robots are mostly designed based on single mode locomotion. However, single mode gait most likely could not work effectively when the robot is subject to an unstructured working environment with different measures of terrain complexity. As a solution, mixed mode locomotion is proposed in this paper by synchronizing two types of gaits known as serpentine and wriggler gaits used for non-constricted and narrow space environments, respectively, but for straight line locomotion only. A gait transition algorithm is developed to efficiently change the gait from one to another. This study includes the investigation on kinematics analysis followed by dynamics analysis while considering related structural constraints for both gaits. The approach utilizes the speed of the serpentine gait for open area locomotion and exploits the narrow space access capability of the wriggler gait. Hence, it can increase motion flexibility in view of the fact that the robot is able to change its mode of locomotion according to the working environment.

Reference Trajectory Generation for 3-Dimensional Walking of a Humanoid Robot

Humanoid walking planning is a complicated task because of the high number of degrees of freedom （DOFs） and the variable mechanical structure during walking. In this paper, a planning method for 3- dimensional （3-D） walking movements was developed based on a model of a typical humanoid robot with 12 DOFs on the lower body. The planning process includes trajectory generation for the hip, ankle, and knee joints in the Cartesian space. The balance of the robot was ensured by adjusting the hip motion. The angles for each DOF were obtained from 3-D kinematics calculation. The calculation gave reference trajectories of all the DOFs on the humanoid robot which were used to control the real robot. The simulation results show that the method is effective.