Automated robotic grinding by low-powered manipulator

A new robotic grinding process has been developed for a low-powered robot system using a spring balancer as a suspension system. To manipulate a robot-arm in the vertical plane, a large actuator torque is required due to the tool weight and enormous gravity effect. But the actuators of the robot system always exhibit a limited torque capacity. This paper presents a cheap and available system for precise grinding tasks by a low-powered robot system using a suspension system. For grinding operations, to achieve position and force-tracking simultaneously, this paper presents an algorithm of the hybrid position/force-tracking scheme with respect to the dynamic behavior of a spring balancer. Material Removal Rate (MRR) is developed for materials SS400 and SUS304. Simulations and experiments have been carried out to demonstrate the feasibility of the proposed system.

The Octahedral Hexarot - a novel 6-DOF parallel manipulator

A novel 6-DOF parallel kinematic manipulator named the Octahedral Hexarot is presented and analyzed. It is shown that this manipulator has the important benefits of combining a large positional workspace in relation to its footprint with a sizable range of platform rotations. These features are obtained by combining a rotation-symmetric actuating arm system with links in an octahedral-like configuration. Thus the manipulator consists of a central cylindrical column with six actuated rotating upper arms that can rotate indefinitely around the central column. Each upper arm is connected to a manipulated platform by one 5-DOF lower arm link. The link arrangement of the Octahedral Hexarot is inspired by the original Gough platform. The manipulated platform is an equilateral triangle and the joint positions on the upper arms approximately form an equilateral triangle. A task dependent optimization procedure for the structural parameters is proposed and the workspace of the resulting manipulator is analyzed in depth.

Embedded vision-based autonomous move-to-grasp approach for a mobile manipulator

This paper proposes a vision‐based autonomous move‐to‐grasp approach for a compact mobile manipulator under some low and small environments. The visual information of specified object with a radial symbol and an overhead colour block is extracted from two CMOS cameras in an embedded way. Furthermore, the mobile platform and the postures of the manipulator are adjusted continuously by vision‐based control, which drives the mobile manipulator approaching the object. When the mobile manipulator is sufficiently close to the object, only the manipulator moves to grasp the object based on the incremental movement with its head end centre of the end‐effector conforming to a Bezier curve. The effectiveness of the proposed approach is verified by experiments.

Automation of a complex transfer operation using a polar manipulator

Purpose – The objective of this paper included developing a polar robot (SPBot) for rotating and transferring car engine block (CEB) around and along two different axes in a confined workspace envelope.

Design/methodology/approach – The complex transfer operations of the CEB requires sweeping complete surface of the half sphere, and thus a polar robot is best suited to such a task in a confined space. Considering the limited space for this operation, a specially designed manipulator is built comprising 2 degrees of freedom driven by electrical servo motors. Also due to the special form of CEB, an especially designed pneumatic gripper is developed. Kinematics models, static and dynamic equations, together with trajectory planning for such a manipulator are described.

Findings – The high-speed complex transfer in a limited environment is successfully implemented.

Originality/value – The developed polar robot provides for complex transfer operations that significantly increases the speed of the product line and thus reducing the cycle time from 60?s using manpower to just 20?s using the robot.

Kinematic analysis and workspace determination of hexarot-a novel 6-DOF parallel manipulator with a rotation-symmetric arm system

Parallel mechanisms possess several advantages such as the possibilities for high acceleration and high accuracy positioning of the end effector. However, most of the proposed parallel manipulators suffer from a limited workspace. In this paper, a novel 6-DOF parallel manipulator with coaxial actuated arms is introduced. Since parallel mechanisms have more workspace limitations compared to that of serial mechanisms, determination of the workspace in parallel manipulators is of the utmost importance. For finding position, angular velocity, and acceleration, in this paper, inverse and forward kinematics of the mechanism are studied and after presenting the workspace limitations, workspace analysis of the hexarot manipulator is performed by using MATLAB software. Next, using the obtained cloud of points from simulation, the overall borders of the workspace are illustrated. Finally, it is shown that this manipulator has the important benefits of combining a large positional workspace in relation to its footprint with a sizable range of platform rotations.

An experimental study on the failure tolerant control of a redundant planar serial manipulator via pseudo-inverse approach

In this paper, fault-tolerant control of redundant planar serial manipulators has been investigated experimentally via an offline method called psuedo-inverse reconfiguration method. Minimizing the end-effector's velocity jump via an optimal mapping of joint failures into healthy joints velocity space can be regarded as the main contribution of this reconfiguration approach. This algorithm has been simulated and implemented on a four-link serial manipulator named as TaArm. It should be mentioned that for simulation and practical tests, C++ programming language in QtCreator environment has been used which provided high computational speed. Two scenarios has been selected for simulation and implementation studies and results shows that the algorithm considerably removes the velocity jump of the end-effector in both simulation and experimetal studies.

An introduction to utilising the redundancy of a kinematically redundant parallel manipulator to operate a gripper

Although parallel manipulators provide several benefits compared to similar-sized serial manipulators, they typically exhibit a limited rotational workspace. One approach to designing a parallel manipulator with infinite range of tool rotation around one axis is to introduce kinematic redundancy. This is typically achieved by extending a non-redundant mechanism with an additional actuator and a supplemental degree of freedom, while the degrees of freedom of the tool platform remain the same. The main drawback of this approach is the cost of the additional actuator. In this paper, we discuss the possibility of harvesting the motion in the additional degree of freedom to operate a gripper. The benefits of the proposed idea include saving the cost of a gripper actuator and reducing the mass of the manipulated platform. Additionally, the requirement to provide the manipulated platform with compressed air or electric power is removed. Several variants of a kinematically redundant manipulated platform with five degrees of freedom are introduced along with conceptual mechanical designs for transforming the redundant platform motion into the opening and closing of a gripper.

A comparison of the yaw constraining performance of SCARA-tau parallel manipulator variants via screw theory

The SCARA-Tau parallel manipulator was derived with the objective to overcome the limited workspace-to-footprint ratio of the DELTA parallel manipulator while maintaining its many benefits. The SCARA-Tau family has later been extended and a large number of variants have been proposed. In this paper, we analyse four of these variants, which together encompass the main differences between all the proposed SCARA-Tau manipulators. The analysed manipulator variants utilise an identical arrangement of five of the six linkages connecting the actuated arms and the manipulated platform and exhibit the same input-output Jacobian. The normalised reciprocal product between the wrench of the sixth linkage and the twist of the platform occurring without this linkage provides a measure on how effectively the sixth linkage constrains the manipulated platform. A comparison of the manipulator variants with respect to this measure demonstrates each variants suitability for specific applications.

Increased functionality of an underwater robotic manipulator

Research into underwater robotic applications is currently a growing field. There are many challenges involved in underwater robotics that are not present in other mediums, such as how the harsh environmental conditions that this environment invokes onto the robot and any equipment that is attached to the robot. In this paper an attachment to an underwater gripper is proposed that adds another Degree Of Freedom to the system, thus allowing the gripper to move along the belly of the robot. Adding this functionality to the gripper has many advantages, some of which involve the robot being able to easily pass a collected object to another robot with minimal interference. This attachment is constructed using 3D printed parts, a waterproofed servomotor and a leadscrew to provide linear motion to a commercial gripper.