Original Workspace Research Articles

Structural optimization method of 6-DOF manipulator based on genetic algorithm

Most of the manipulator is designed under the constraint of motion reversibility, and the optimization of the manipulator structure is often carried out through the study of kinematics. In order to solve the structural optimization problem of a 6-Dof manipulator, this paper proposes a structural optimization method based on a 6-Dof manipulator with comprehensive indexes combining kinematics performance and dynamics performance. On the premise of satisfying the original workspace and taking dynamic performance as evaluation function, genetic algorithm was used to optimize the structural parameters of the manipulator, so that the optimized manipulator not only has the characteristics of the original workspace, but also consumes the least energy. The kinematic equation of the manipulator was derived, the dynamics model was established by Lagrange method, and then the fitness function and the structural optimization algorithm of the manipulator based on genetic algorithm were given.

An Evolutionary-Optimized Surgical Path Planner for a Programmable Bevel-Tip Needle

Path planning algorithms for steerable needles in medical applications must guarantee the anatomical obstacle avoidance, reduce the insertion length, and ensure the compliance with the needle kinematics. The majority of the solutions from the literature focus either on fast computation or on path optimality, the former at the expense of suboptimal paths, the latter by making unbearable the computation in case of a high-dimensional workspace. In this article, we implement a three-dimensional path planner for neurosurgical applications, which keeps the computational cost consistent with standard preoperative planning algorithms and fine-tunes the estimated pathways in accordance to multiple optimization objectives. From a user-defined entry point, our method confines a sample-based path search within a subsection of the original workspace considering the degree of curvature admitted by the needle. An evolutionary optimization procedure is used to maximize the obstacle avoidance and reduce the insertion length. The pool of optimized solutions is examined through a cost function to determine the best path. Simulations on one dataset showed the ability of the planner to save time and overcome the state of the art in terms of obstacle avoidance, insertion length, and probability of failure, proving this algorithm as a valid planning method for complex environments.

IoT-Enabled Dual-Arm Motion Capture and Mapping for Telerobotics in Home Care.

With the paradigm shift from hospital-centric healthcare to home-centric healthcare in Healthcare 4.0, healthcare robotics has become one of the fastest growing fields of robotics. The combination of robot capabilities with human intelligence, for example, telerobotics for home care, is gradually showing promising potentials. In this paper, the Home-TeleBot system, a generalized IoT-enabled telerobotic architecture designed to support home-centric healthcare system, is proposed. In particular, the implementation of it is realized by integrating human-motion-capture subsystem with robot-control subsystem. The dual-arm cooperative robot, YuMi, imitates human motion captured by a set of wearable inertial motion capture devices to complete tasks. The proposed approach using workspace mapping and path planning of robot manipulators, facilitates telerobot to execute tasks in a natural and human-like way. Based on the constant of proportionality calculated by comparing the human original workspace with the robot original workspace, the workspace mapping is achieved by making assumptions of the distance between end-effectors (human hands, robot's grippers) and shoulders. Additionally, robot manipulators' path is planned by setting virtual obstacles to constrain robot motion, which aims to improve the performance of robot's human-like motion. As a specific example of application, we apply the proposed architecture to a fetching task based on dual-arm motion capture and mapping for telerobotics in home care.

Geometrical/analytical approach for reciprocal screw-based singularity analysis of a novel dexterous minimally invasive manipulator

This paper is concerned with the singularity analysis of a novel 4-DOF endoscopic surgical parallel manipulator (2-PUU_2-PUS). This parallel manipulator has larger bending angles compared to previously existing surgical parallel manipulators. It is easy to imagine the singular configurations inside the workspace of a manipulator with a zero pitch and infinity pitch reciprocal screws. On the other hand, the (2-PUU_2-PUS) surgical manipulator has two reciprocal screws of h-pitch. Hence, the singular configurations of this manipulator could not be provided by the known reciprocal screw-based geometrical approach. Therefore, the geometrical/analytical approach for reciprocal screw-based singularity analysis of 2-PUU_2-PUS is proposed in this work. The results illustrate the feasibility of the proposed algorithm to find all singular configurations of the 2-PUU_2-PUS manipulator. The discovered singularity configurations greatly shrink the singularity-free workspace to be one-fourth of the original workspace. In order to be able to work through the entire workspace, we suggest changing the topology structure of the manipulator.

Optimized Configurations of Kinematically Redundant Planar Parallel Manipulator following a Desired Trajectory

Abstract This paper presents an optimization methodology for achieving minimum actuation torques of a kinematically redundant planar parallel mechanism following a desired trajectory using binary coded Genetic Algorithms (GA). A user interactive computer program developed in present work helps for obtaining inverse kinematic solution and Jacobian matrices at a given Cartesian coordinate location of the end-effector. Furthermore, the joint torques are obtained from the end-effector forces (wrench) using Jacobian matrix at every location. The resultant joint torque vector can be used to describe the objective function. The variables of the optimization problem are redundant base prismatic joint displacements and the constraints include the variable bounds and the pre-defined trajectory lying within the original workspace. The outputs of the kinematically-redundant 3-PRRR manipulator are compared against the results for a non-redundant 3-RRR manipulator. The results show that the redundant manipulator gives relatively lower input torques. Also, it is observed that while passing through singular configurations on the trajectory, finite values of torques are achieved. Results are shown for a straight-line trajectory.

Simulation of obstacles’ effect on industrial robots’ working space using genetic algorithm

The study of robot workspace is an interesting problem since its applications are directly related to industry. However, it involves several mathematical complications; Thus, many of the arising questions are left without a definite answer. With the motivation of industrial demand, the need for finding better answers than the existing ones lasts. The workspace (WS) determination of a robot with general structural parameters is a complex problem, which cannot be solved in an explicit way. Closed form solutions are only available in some particular cases. Otherwise, computational algorithms and numerical techniques are used. The task becomes even much more complicated by the presence of obstacles in the robot accessible region. Obstacle presence does not only exclude points from the original WS but it affects the whole robot workspace’s shape and size to the extent that it sometimes divides the working space in two or more separate regions that cannot be linked by the same robot. Much research work in the literature is directed toward path planning in the presence of obstacles without having to determine the robot WS. However, a real situation in industry occurs when the knowledge of the WS is of importance in facility layout. This paper presents an approach for the estimation of a generic open-chain robot in the presence of obstacles with any desired number of prismatic and/or revolute joints of any order. Joints’ axes may have any orientation relative to each other. The robot can be placed in free space or in a work cell consisting of a set of Computer Numerically Controlled (CNC) machines and some obstacles.

A simulation and training environment for robotic radiosurgery

To provide a software environment for simulation of robotic radiosurgery, particularly to study the effective robot workspace with respect to the treatment plan quality, and to illustrate the concepts of robotic radiosurgery. A simulation environment for a robotic radiosurgery system was developed using Java and Java3D. The kinematics and the beam characteristics were modeled and linked to a treatment planning module. Simulations of different robot workspace parameters for two example radiosurgical patient cases were performed using the novel software tool. The first case was an intracranial lesion near the left inner ear, the second case was a spinal lesion. The planning parameters for both cases were visualized with the novel simulation environment. An incremental extension of the robot workspace had limited effect for the intracranial case, where the original workspace already covered the left side of the patient. For the spinal case, a larger workspace resulted in a noticeable improvement in plan quality and a large portion of the beams being delivered from the extended workspace. The new software environment is useful to simulate and analyze parameters and configurations for robotic radiosurgery. An enlarged robot workspace may result in improved plan quality depending on the location of the target region.

Implicit instead of the explicit copy command

If one prefers to include all required programs together in one workspace, the necessary programs could, as usual, be retrieved from other workspaces by the explicit copy command and stored together in the same workspace. However, there are a number of reasons why one would like to have some necessary programs or variables residing in their original workspace. Therefore a useful enhancement in order to use those objects in their original position would be the implicit copy where a qualified name is used in the header. This qualified name is the pure name preceded by its workspace library reference. The result should be the creation of a temporary local environment, followed by a copy of that object from the referred workspace.