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Robotics
Published in Gregory S. Chirikjian, Alexander B. Kyatkin, Engineering Applications of Noncommutative Harmonic Analysis, 2021
Gregory S. Chirikjian, Alexander B. Kyatkin
A manipulator is a robot arm and/or hand that is usually fixed to some kind of base. A manipulator can have a serial chain topology in which there are no loops formed by the links of the arm. It is also possible to have a parallel or platform architecture in which one or more loops exist. A third possibility is a tree-like topology such as a hand or cooperating serial manipulators. In any of these topologies, the actuators which drive the movement of the arm can be revolute (rotational) such as an electric motor, prismatic (translational) such as a hydraulic cylinder, or some combination of the two (e.g., a screw). The key computational issues in the use of manipulator arms in industrial or service environments all depend on the fast calculation of joint angles1 which will place the functional end of the arm (called the end effector) at the desired position and/or orientation relative to its base. The set of all positions and orientations that an arm can reach is called its workspace. The determination of the joint angles that result in the desired end-effector state is called the inverse kinematics problem. The forward kinematics problem is the problem of finding the position and/or orientation of the end effector when the value of the joint angles is given. As a rule, the forward kinematics problem is very easy to solve for serial manipulators, and the inverse problem is more difficult. However, for parallel manipulators, the opposite is true. And in a sense, hybrid manipulators (in which two or more parallel structures are stacked) inherit the difficult aspects of both serial and parallel manipulators. The workspace generation problem is that of determining all positions and/or orientations reachable by a robotic arm (see, for example, [1, 7, 33, 34, 49, 50]).
Introduction to Robotic Manipulators
Published in Kevin Russell, Qiong Shen, Raj S. Sodhi, Kinematics and Dynamics of Mechanical Systems Implementation in MATLAB® and Simmechanics®, 2018
Kevin Russell, Qiong Shen, Raj S. Sodhi
In forward kinematics, the link dimensions and joint motion of a robotic manipulator are known and the corresponding output motion of the links (usually the end effector) is calculated [3]. By formulating an equation system for a robotic manipulator (an equation system to calculate the motion of specific link points) and prescribing the link dimensions and joint motions, the resulting link motion is calculated. The most common application for forward kinematics is for determining end effector motion (e.g., tool paths and orientations).
Example 15: Unity and Kinematics
Published in Ata Jahangir Moshayedi, Amin Kolahdooz, Liefa Liao, Unity in Embedded System Design and Robotics, 2023
Ata Jahangir Moshayedi, Amin Kolahdooz, Liefa Liao
Kinematics is the division of procedure that studies the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it. Robot Kinematics refers to the analytical study of the motion of a robot manipulator. For Kinematics, we interfere with two words of Inverse Kinematics as well as forward Kinematics. The problem with Inverse Kinematics is that it can be seen as the one of finding the joint values corresponding to some specific position and/or orientation of a given body element (generally the end effector). In contrast, Forward Kinematics refers to the process of obtaining the position and velocity of the end effector, given the known joint angles and angular velocities. Formulating suitable kinematics models for a robot mechanism is crucial for analysing industrial manipulators' behaviour. More generally, it is a transformation from the task space coordinates into the joint space coordinates. In Unity, you can also consider the Inverse Kinematics for your character, because animation needs to work with the rotation of Angles of joints. In this chapter, we'll briefly look into how Inverse Kinematics is implemented in Unity. A Unity asset is an item that you can use in your game or project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file, an image, or other file types that Unity supports. The main reason for using assets is to speed up development and ease of access. Assets are like templates. It can be a ready-made component that's downloaded and used or plug and play. It also provides users with a new and experienced introduction to new functions that are not readily available out of the box in Unity. The main goal of this example guide is to show how the concept of Inverse Kinematics can be applied in Unity with ready-made assets from the assets store of Unity. Users can learn how Inverse Kinematics can be implemented or at least get started in the direction of applying Inverse Kinematics in their game/project development.
Towards the development of an intuitive teleoperation system for human support robot using a VR device
Published in Advanced Robotics, 2020
Jun Nakanishi, Shunki Itadera, Tadayoshi Aoyama, Yasuhisa Hasegawa
Our control software is implemented on ROS using C++ on the Linux PC (see Figure 1). This software receives the current information of the VR devices and the robot states such as joint angles, position of the mobile base and the wrist force measurement as ROS messages. Given these pieces of information, we compute the desired position of the arm and head joints, the base velocity and the gripper command of HSR, and send them to the robot as ROS messages. We implement the necessary computations such as forward kinematics and the Jacobian by ourselves. In addition, to achieve whole-body control of the robot, we implement our own inverse kinematics robust to kinematic singularities based on the numerical algorithm in [37] (Section 3.2) suited for safe teleoperation of the robot. Using this framework, we also attempt to implement a whole-body admittance controller (Section 3.5). In addition, with the contact force information measured with the wrist force sensor on the robot, we send the vibration command to the Oculus Touch device to provide haptic feedback. The amplitude of the vibration is set to be proportional to the magnitude of the measured contact force (Section 3.7). As we have multiple subscribers in our control software, we employ multi-threaded spinning to process callbacks in parallel, i.e. non-blocking callbacks, using ros::MultiThreadedSpinner. The frequency of the control loop is 80 Hz. In our implementation, all these processes can be computed sufficiently fast within this control loop.
Design of a single motor, tendon driven redundant manipulator with reduced driving joint torques
Published in Mechanics Based Design of Structures and Machines, 2018
Malaka Miyuranga Kaluarachchi, Jee-Hou Ho, Samer Yahya
The forward kinematics of the proposed manipulator is presented in this section. Forward kinematics is defined as joint space to Cartesian space transformation. Forward kinematics is used for the identification of position of the end effector for a given set of joint angles and link parameters with respect to a reference frame (Castelli et al., 2008; Spiers et al., 2016). For the computation of forward kinematics DH parameters of the manipulator have to be identified. The frames assigned for the proposed manipulator is shown in Figure 7. Furthermore, the corresponding DH parameters are shown in Table 1. The links lengths of the manipulator links 1–3 are represented by 11, 12, and 13, respectively.
Design and control of a 7 DOF redundant manipulator arm
Published in Australian Journal of Mechanical Engineering, 2021
Priyadarshi Biplab Kumar, Navneet Kumar Verma, Dayal R. Parhi, Deepayan Priyadarshi
Study of the forward kinematics relates individual robot manipulator joints and end effector’s orientation and position. In simple words, the forward kinematics is used to find the end effector’s orientation and position with the help of given value of the joint variable of the robot. In case of revolute joint, angles between the link are joint variables and in case of prismatic or sliding joints extension of links is joint variable. Figure 1 represents the forward kinematics model of a manipulator as an example.