Real Time Inverse Kinematics with Joint Limits and Spatial Constraints

3D spatially-adaptive canonical correlation analysis: Local and global methods

Bimanual robots have been studied for decades and regulation on internal force of the being held object by two manipulators becomes a research interest in recent years. In this paper, based on impedance model, a method to obtain the optimal target position for bimanual robots to hold an object is proposed. We introduce a cost function combining the errors of the force and the position and manage to minimize its value to gain the optimal coordinates for the robot end effectors (EE). To implement this method, two necessary algorithms are presented, which are the closed-loop inverse kinematics (CLIK) method to work out joint positions from desired EE pose and the generalized-momentum-based external force observer to measure the subjected force acting on the EE so as to properly compensate for the joint torques. To verify the effectiveness, practicality, and adaptivity of the proposed scheme, in the simulation, a bimanual robot system with three degrees of freedom (DOF) in every manipulator was constructed and employed to hold an object, where the results are satisfactory.

This paper deals with the development of a special 3+1 Degrees of Freedom (DOFs) end effector used to control the standard laparoscopic instrumentation’s positioning and actuation during laparoscopic surgery. Nowadays, the robotic system da Vinci is the most used robot in the laparoscopic surgery field. The cost of this robot is very high, which limits its spread in hospitals. Moreover, this robot can use only customized tools, called endoWrist, to perform the laparoscopic surgery. This instruments are, however, very expensive and can be used only for few operations, increasing the required economical efforts. The aim of our research is to create an end effector, supported by a navigator arm, able to manipulate standard laparoscopic instruments in order to reduce the cost of the robotic surgery, while keeping most of the advantages introduced by the other robotic systems. The particular structure of the end effector proposed here makes it possible to create a virtual spherical wrist at the insertion point. This solution allows to have the mobility needed to perform the surgery and to avoid excessive stress to the patient skin. The main disadvantage is represented by the DOFs of the standard laparoscopic tools that are less than in the endoWrists. However, the proposed end effector allows to manipulate standard laparoscopic tools smaller than customized robotic instruments, which is a fundamental feature in neonatal and paediatric surgery.

In this paper, a learning control algorithm for the motion and force of a direct-drive robot, which has a variable table and six degrees of freedom (d. o. f.), is proposed for a task in constrained work space. The five-d. o. f. relative motion of an end effector attached to the wrist of the robot arm and the internal force between the end effector and the table through an object are achieved by utilizing the redundancy to avoid interference with the object. A hybrid controller for an end effector and a position controller for a robot arm are used. Under the over-constrained conditions, which are imposed by the two tasks stated above, a learning control algorithm using neural networks (NN's)is employed to control an end effector with higher priority than the robot arm. The proposed control algorithm is applied to an experiment on the control of both the position of an end effector and the contact force on the surface of the object while avoiding interference with the object. As a result, it has been shown that the trajectories of robot joints can be generated in real-time computation and a high accuracy of the end effector is obtained after the completion of learning. The effectiveness of the proposed control algorithm is demonstrated by the experiment.

An Optoelectronic System for Force-Torque Sensing and Feedback Algorithms Processing

Teleoperation of robotic proxies can extend human control to spaces, tasks and constraints that would otherwise be intractable or unattainable. The robustness to harsh environments, scalability, precision and repeatability of robots make them ideal for dangerous or difficult missions, and their use oftentimes reduces monetary and human cost. Maneuverable robot devices can provide more flexibility and articulation, but come at the cost of kinematic complexity. The kinematics and workspace of the remote device is oftentimes dissimilar to the input device, leading to potential confusion and frustration of the human operator. One solution is to constrain the input device motion to a scaled version of remote device joint ranges. This paper presents a method for doing so with 3 degree of freedom (DOF) manipulators and input devices with kinematic dissimilarities. The approach utilizes a simple tree structure, whereby a local Cartesian workspace limit is sampled and indexed by joint. This generates a locally sampled joint limit surface, represented as a point cloud. This local point cloud is then used to provide 3DOF haptic feedback to the operator as an indication that a joint limit has been reached, and provides kinesthetic force feedback to efficiently remove the operator from that joint limit. This work can improve usability of human-robot interfaces for teleoperation by allowing users to naturally intuit remote device joint limits and avoid confusion.

In this study a five Degrees of Freedom (DOF) serial robot manipulator was designed and implemented. The inverse kinematics problem, which has not exact analytical solution (only one inverse kinematic solution for a predefined end effector position in three dimensional space), of the robot mechanism was solved by using the combination of the analytical method and a simple search method. In order to use the proposed method in real-time applications, the method is designed so that it can be used to solve the inverse kinematics problem for the next point of the end-effector while the mechanism is working. Moreover, so that to control the implemented mechanism, a user interface program was written by using Visual Basic programming language. Finally, the proposed inverse kinematic solution method was tested on two different trajectories, an arc shaped trajectory that composed of 58 points and a linear trajectory divided into 29 points. The obtained results revealed that the proposed method can be used successfully in solving the inverse kinematic problem of the designed mechanism.

An assessment of industrial robots: Capabilities, economics, and impacts

The aim of this paper is to present the design and development of a safe and reliable autonomous cat toy for the purposes of entertaining pet cats when human interaction is not feasible. The proposed Autonomous Feline Entertainment Robot (AFER), an autonomous cat toy, is comprised of a table-mounted base, and a robotic arm with two linkages. The AFER Version 1(vl) has a cat-toy affixed to the end of a linkage as the end effector, while the AFER Version 2 (v2) has a passive joint with a string to which a cat toy end effector is attached. The AFER v1 has 2 Degrees of Freedom (DOF), while the AFER v2 has 3DOF, and both are actuated by servomotors interfaced with an Arduino microcontroller. In order to enable maximum functionality, the AFER is designed with multiple movement patterns or modes for play, as well as the ability to change the specific end effector of the toy. Position control was used for the motion and trajectory planning when developing the movement patterns. The interaction between AFER and two kittens has been evaluated in an experimental scenario, and the results show satisfactory and safe interactions. The AFER can be used as a model for studying effective animal-robot interactions and pet entertainment.

The paper presents the structure of a precise parallel tri-axle manipulator with the functionality of progressing-tilting table. The end effector of the device is a platform, for which three coordinates of position are defined. The manipulator has three degrees of freedom: movement perpendicular to the base and rotation in two mutually perpendicular axes contained in the surface parallel to the base.The concept of the positioning mechanism is based on parallel tripod kinematics where the end effector – the platform – is seated on three active limbs – actuators. The use of parallel kinematics allowed modular construction of the positioning mechanism. The developed modular functional mechanism with minimal number of elements in kinematic chain ensures high positioning resolution. The concept of application of eccentric mechanism for platform positioning is an original idea in this solution. The compact construction allows applying the manipulator in medical devices that require meeting of the hygienic conditions in the medical test and research laboratories. The possibility of the utilisation of the precise manipulator covers wide areas of science and technology where precise positioning of the object is required, e.g. sample positioning for microscopes, scanning systems.

Calcul de la matrice Jacobienne nécessaire à la commande coordonnée d'un manipulateur

In the last twenty years genetic algorithms (GAs) were applied in a plethora of fields such as: control, system identification, robotics, planning and scheduling, image processing, and pattern and speech recognition (Back et al., 1997). In robotics the problems of trajectory planning, collision avoidance and manipulator structure design considering a single criteria has been solved using several techniques (Alander, 2003). Most engineering applications require the optimization of several criteria simultaneously. Often the problems are complex, include discrete and continuous variables and there is no prior knowledge about the search space. These kind of problems are very more complex, since they consider multiple design criteria simultaneously within the optimization procedure. This is known as a multi-criteria (or multiobjective) optimization, that has been addressed successfully through GAs (Deb, 2001). The overall aim of multi-criteria evolutionary algorithms is to achieve a set of non-dominated optimal solutions known as Pareto front. At the end of the optimization procedure, instead of a single optimal (or near optimal) solution, the decision maker can select a solution from the Pareto front. Some of the key issues in multi-criteria GAs are: i) the number of objectives, ii) to obtain a Pareto front as wide as possible and iii) to achieve a Pareto front uniformly spread. Indeed, multi-objective techniques using GAs have been increasing in relevance as a research area. In 1989, Goldberg suggested the use of a GA to solve multi-objective problems and since then other researchers have been developing new methods, such as the multi-objective genetic algorithm (MOGA) (Fonseca & Fleming, 1995), the non-dominated sorted genetic algorithm (NSGA) (Deb, 2001), and the niched Pareto genetic algorithm (NPGA) (Horn et al., 1994), among several other variants (Coello, 1998). In this work the trajectory planning problem considers: i) robots with 2 and 3 degrees of freedom (dof ), ii) the inclusion of obstacles in the workspace and iii) up to five criteria that are used to qualify the evolving trajectory, namely the: joint traveling distance, joint velocity, end effector / Cartesian distance, end effector / Cartesian velocity and energy involved. These criteria are used to minimize the joint 27

This paper presents a generalised framework of an image based visual servoing of an articulated arm which has to be deployed inside a simulated Tokamak vessel environment. First wall tiles of the vessel idealised as rectangular grids on a surface are inspected and an attempt is made to replace the damaged tiles with a tile-screwing gripper mechanism. The mechanism of gripper provides compactness and high torque capacity in gripping with pitch and roll as degrees of freedom. The gripper is considered as a class of unknown nonlinear discrete-time system. The gripper mechanism is implemented for unscrewing a square headed screw on the first wall tiles of the vessel. Various stages of tile handling task are explained in detail with theoretical modeling. The vision sensing methodology of the proposed arm is explained. The arm has a camera located at the wrist (end effector) and the control action has to be taken in place at joint level. The kinematics of the manipulator, vision system employed are explained. The preliminary results are illustrated. The camera attached to the end effector and the captured image processing for prediction of type of fault and the gripper tactile sensing issues as well the faulty tile removal are explained.

Intelligent manufacturing systems rely heavily on industrial robots. An industrial robot manipulator moves its end effector from an initial position and orientation to the desired final position and orientation in its workspace with less error. However, the generally used approaches are not capable to solve the complicated inverse kinematics problems of industrial robotic manipulators with more degrees of freedom. Nowadays, various neural network methods such as artificial neural network (ANN) and convolution neural network (CNN) are being used to overcome such complications. In this paper, 6 degree of freedom (DOF) robot manipulator is modeled, and its kinematics parameters are analyzed. A CNN is based on the shared weight architecture of kernels that extract input features and provide equivalent responses called feature maps. Following the generation of a data set, the training, validation, and testing of the neural network model are done using the input data set, and various plots such as performance plot, training state, and regression plot are studied. The data were divided randomly, where 70% data are provided to the training set, 15% data to the validation set, and 15% data to the testing set. As a result, the error obtained was within the acceptable limits.Keywords6-DOF robotInverse kinematicsD–H parametersMATLABConvolution neural network (CNN)

A suffcient set of constraint equations to carry out kinematic analysis is detailed in the context of 4 degree of freedom (dof) fully parallel 4-legged Schonflies manipulators. The set inevitably contains data pertaining to joint variables, end effector (EE) and fixed frame (FF) space design parameters. Therefore the equations are sometimes readily adaptable to direct kinematics (DK), inverse kinematics (IK), design problems or some combination by choosing any set of equation parameters to be unknowns, as many as there are equations. Numerical examples are presented. These serve to caution the reader regarding the pitfalls in one-size-fits-all methodology. It is observed that limited angular displacement workspace plagues many designs.