Design Of End-effector Research Articles

End-effector design optimisation and multi-robot motion planning for handling compliant parts

The deformation of compliant parts during material handling is a critical issue that can significantly affect the productivity and the parts’ dimensional quality. There are multiple relevant aspects to consider when designing end-effectors to handle compliant parts, e.g. motion planning, holding force, part deformations, collisions, etc. This paper focuses on multi-robot material handling systems where the end-effector designs influence the coordination of the robots to prevent that these collide in the shared workspace. A multi-disciplinary methodology for end-effector design optimisation and multi-robot motion planning for material handling of compliant parts is proposed. The novelty is the co-adaptive optimisation of the end-effectors’ structure with the robot motion planning to obtain the highest productivity and to avoid excessive part deformations. Based on FEA, the dynamic deformations of the parts are modelled in order to consider these during the collision avoidance between the handled parts and obstacles. The proposed methodology is evaluated for a case study that considers the multi-robot material handling of sheet metal parts in a multi-stage tandem press line. The results show that a substantial improvement in productivity can be achieved (up to 1.9%). These also demonstrate the need and contribution of the proposed methodology.

A bio-inspired approach for the design of a multifunctional robotic end-effector customized for automated maintenance of a reconfigurable vibrating screen

The development of a robotic-driven maintenance solution capable of automatically maintaining reconfigurable vibrating screen (RVS) machine when utilized in dangerous and hazardous underground mining environment has called for the design of a multifunctional robotic end-effector capable of carrying out all the maintenance tasks on the RVS machine. In view of this, the paper presents a bio-inspired approach which unfolds the design of a novel multifunctional robotic end-effector embedded with mechanical and control mechanisms capable of automatically maintaining the RVS machine. To achieve this, therblig and morphological methodologies (which classifies the motions as well as the actions required by the robotic end-effector in carrying out RVS machine maintenance tasks), obtained from a detailed analogy of how human being (i.e. a machine maintenance manager) will carry out different maintenance tasks on the RVS machine, were used to obtain the maintenance objective functions or goals of the multifunctional robotic end-effector as well as the maintenance activity constraints of the RVS machine that must be adhered to by the multifunctional robotic end-effector during the machine maintenance. The results of the therblig and morphological analyses of five (5) different maintenance tasks capture and classify one hundred and thirty-four (134) repetitive motions and fifty-four (54) functions required in automating the maintenance tasks of the RVS machine. Based on these findings, a worm–gear mechanism embedded with fingers extruded with a hexagonal shaped heads capable of carrying out the “gripping and ungrasping” and “loosening and bolting” functions of the robotic end-effector and an electric cylinder actuator module capable of carrying out “unpinning and hammering” functions of the robotic end-effector were integrated together to produce the customized multifunctional robotic end-effector capable of automatically maintaining the RVS machine. The axial forces (F_{{1{text{t}}}} and F_{{2{text{t}}}}), normal forces (F_{text{n}}) and total load (F_{text{d}} ) acting on the teeth of the worm–gear module of the multifunctional robotic end-effector during the gripping of worn-out or new RVS machine subsystems, which are 978.547, 1245.06 and 1016.406 N, respectively, were satisfactory. The nominal bending and torsional stresses acting on the shoulder of the socket module of the multifunctional robotic end-effector during the loosing and tightening of bolts, which are 1450.72 and 179.523 MPa, respectively, were satisfactory. The hammering and unpinning forces utilized by the electric cylinder actuator module of the multifunctional robotic end-effector during the unpinning and hammering of screen panel pins out of and into the screen panels were satisfactory.

Design and force analysis of end-effector for plug seedling transplanter.

Automatic transplanters have been very important in greenhouses since the popularization of seedling nurseries. End-effector development is a key technology for transplanting plug seedlings. Most existing end-effectors have problems with holding root plugs or releasing plugs. An efficient end-effector driven by a linear pneumatic cylinder was designed in this study, which could hold root plugs firmly and release plugs easily. This end-effector with four needles could clamp the plug simultaneously while the needles penetrate into the substrate. The depth and verticality of the needles could be adjusted conveniently for different seedling trays. The effectiveness of this end-effector was tested by a combinational trial examining three seedling nursery factors (the moisture content of the substrate, substrate bulk density and the volume proportion of substrate ingredients). Results showed that the total transplanting success rate for the end-effector was 100%, and the root plug harm rate was below 17%. A force measure system with tension and pressure transducers was installed on the designed end-effector. The adhesive force FL between the root plug and the cell of seedling trays and the extrusion force FK on the root plug were measured and analyzed. The results showed that all three variable factors and their interactions had significant effects on the extrusion force. Each factor had a significant effect on adhesive force. Additionally, it was found that the end-effector did not perform very well when the value of FK/FL was beyond the range of 5.99~8.67. This could provide a scientific basis for end-effector application in transplanting.

Estimating anatomical wrist joint motion with a robotic exoskeleton.

Robotic exoskeletons can provide the high intensity, long duration targeted therapeutic interventions required for regaining motor function lost as a result of neurological injury. Quantitative measurements by exoskeletons have been proposed as measures of rehabilitative outcomes. Exoskeletons, in contrast to end effector designs, have the potential to provide a direct mapping between human and robot joints. This mapping rests on the assumption that anatomical axes and robot axes are aligned well, and that movement within the exoskeleton is negligible. These assumptions hold well for simple one degree-of-freedom joints, but may not be valid for multi-articular joints with unique musculoskeletal properties such as the wrist. This paper presents an experiment comparing robot joint kinematic measurements from an exoskeleton to anatomical joint angles measured with a motion capture system. Joint-space position measurements and task-space smoothness metrics were compared between the two measurement modalities. The experimental results quantify the error between joint-level position measurements, and show that exoskeleton kinematic measurements preserve smoothness characteristics found in anatomical measures of wrist movements.

Design of a force-controlled end-effector with low-inertia effect for robotic polishing using macro-mini robot approach

In this paper, the novel design of a force-controlled end-effector for automated polishing processes is presented. The proposed end-effector is to be integrated into a macro-mini robot polishing cell. The macro robot (in this study, it is a six-axis industrial robot) is used to position the mini robot (the proposed end-effector) according to the workpiece profile while the mini robot controls the polishing force. Th end-effector has a polishing head that can be extended and retracted by a linear hollow voice coil actuator to provide tool compliance. The main advantage of the proposed design is that it allows this motion without extending or retracting the polishing motor nor spindle, which reduces the inertial effects that may results in undesired vibrations. By integrating a force sensor, the polishing force is measured and fed back to the controller to regulate it according to the polishing pre-planned requirements. The effectiveness of the proposed device to track a certain desired force with step changes under different feed rates has been examined through polishing experiments. The results demonstrate the effectiveness of the presented device to reduce the vibration and achieve remarkable force tracking.

Virtual and Rapid Prototyping of an Underactuated Space end Effector

A fast and reliable verification of an initial concept is an important need in the field of mechatronics. Usually, the steps for a successful design require multiple iterations involving a sequence of design phases-the initial one and several improvements-and the tests of the resulting prototypes, in a trial and error scheme. Now a day’s software and hardware tools allow for a faster approach, in which the iterations between design and prototyping are by far reduced, even to just one in favorable situation. This work presents the design, manufacturing and testing of a robotic end effector for space applications, realized through virtual prototyping, followed by rapid prototyping realization.

Autonomous Sweet Pepper Harvesting for Protected Cropping Systems

In this letter, we present a new robotic harvester (Harvey) that can autonomously harvest sweet pepper in protected cropping environments. Our approach combines effective vision algorithms with a novel end-effector design to enable successful harvesting of sweet peppers. Initial field trials in protected cropping environments, with two cultivar, demonstrate the efficacy of this approach achieving a 46% success rate for unmodified crop, and 58% for modified crop. Furthermore, for the more favourable cultivar we were also able to detach 90% of sweet peppers, indicating that improvements in the grasping success rate would result in greatly improved harvesting performance.

The Optimal Design and Simulation of End-effector of Working Robot

One designation of end effector was raised in order to make robot grasp spherical target effective and cut the conjunction off the matrix. The end effector consists of clamp module and cutting module. The clamp module clamps a spherical target with leadscrew motivated linkage system driven by motor. And cutting module cuts the target with extended blade under the control of steering gear. A kinematic model and static balance model was established and a double targets optimal function and constraint condition is obtained according to the geometry and load-bearing relations. The best composition of key parameters of the end effector was obtained with an optimal design to the size of linkages and power output of the link mechanism of the end effector with MATLAB. A kinematical simulation of clamp module and cutting module of the end effector were done with ADAMS. By means of analyzation, cutting characteristic curve of cutting module and kinematic relation curve of key structures in clamp module are acquired. With these methods, the reasonability in structural design of this scheme was turned out. Also, a robot end effector satisfied various performance requirements were achieved eventually.

A robotic system for automated bed-making using a gripper specialized for textile manipulation

Robots are expected to perform a variety of household tasks. Tasks such as bed making and tucking textile layers during seat manufacture represent a particular challenge, as they require both sensitive manipulation and strong pushing capabilities. In this paper, we present a robotic solution for automated bed making with a force-sensing robot arm and an end effector for textile manipulation, which can manipulate textiles, as well as apply high forces to tuck a textile into a small space. The system can also use its fingertips to confirm grasp success by detecting the grasped material. The end effector design is available open source. We experimentally confirm the proposal’s effectiveness in the last part of the bed making task.

The Study of Design Method for Robotic Drill End Effector

The drill end effector is a key sub-system to flexible robotic drilling system, which performance will have an effect on drilling quality and efficiency. As a highly-integrated small electro-mechanical system, the design of drill end effector should be based on the robot and the process. The effect of the stiffness, the payload and the accuracy of the robot, the mounted configuration of the end effector, the technological process, and the orbital drilling technique were analyzed. And according to the analysis results, the design method of the drill end effector is established.

Field test of different end-effectors for robotic harvesting of sweet-pepper

This paper focusses on field experiments with two different types of endeffectors for robotic harvesting of sweet-pepper fruits. One of the major issues is to reach, grasp and detach the fruit efficiently, without damaging it, while avoiding obstacles in the environment. End-effectors for harvesting fruit must be able to adapt to different fruit sizes and geometries. Two types of end-effectors were designed and realized. The first one had four fingers which utilized the Ray effect to grip the fruit. A scissor-like cut mechanism on top of the fingers was used to cut through the fruit peduncle. The second, a lip-type end-effector first stabilized the fruit using a suction cup after which two rings enclosed and cut the peduncle with a circular blade integrated in the upper lip. Both end-effectors had integrated miniature cameras with a LED illumination system: one Time of Flight camera and the other a colour camera. To study the performance of the end-effectors a number of harvesting experiments were performed in commercial sweet-pepper greenhouses. Special attention was paid to the following aspects: positioning at the target fruit, separation of the fruit from the plant, fruit damage, leaf damage and plant stem damage. Both end-effector designs had their strengths and weaknesses. The Fin ray type end-effector harvested a maximum of 80% of the fruits on the plant, the lip-type end-effector a maximum of 76% of the fruits. In none of the experiments more than 64% of the fruit could be harvested without fruit damage.

Design of a Novel End-Effector for Kinematic Support in Incremental Sheet Forming

The formability and geometrical accuracy in incremental sheet forming can be increased using a force-controlled support tool. The main problems in using such a kinematic support tool is the positioning of forming and support tools, while maintaining force magnitude and alignment. A new tool for this was developed systematically using a morphological box. It uses a spring controlled rotation of the tool tip to maintain the force. Since the rotation axis is not in line with the tool tip axis and the tool tip can freely rotate around its axis, roll friction conditions can be achieved. The center of gravity of the rotating part of the tool is placed in the rotating axis and the force is therefore independent from the alignment of the tool in space. It has a mechanical stop with locking option in the vertical position and is therefore also fully usable as a forming tool. While the prototype is manually controlled, concepts for a fully automated version have been designed, as well. First tests are in line with results described in literature, showing that direction and magnitude of force have an influence on the formability.

Design Analysis for a Special Serial - Parallel Manipulator Transferring Billet for Hot Extrusion Forging Process

To reduce the downtime and optimize the use of energy and manpower, a serial - parallel manipulator is designed for transferring heavy billets for a specific hot extrusion forging process. To increase the structural rigidity and restrict the end-effector of the robot moving in direction parallel with the ground surface, parallel links are added in between serial links of the manipulator design. This modification of the structure must be considered in the modeling and analyzing. This paper addresses the kinematic modeling, the kinematic performance analysis and the strength analysis for the robot. With respect to the parallel links, the constraint equation is written and put together with the kinematic model. Based on the model formulated, the inverse kinematic, the transferring time, the reachable workspace, the dexterity, and the manipulability index of the robot are analyzed and discussed to demonstrate its kinematical performance. These results are important to assess the working capability and improve the parametric design for the robot. In addition, for verifying the end-effector design in terms of the strength and displacement, the stress distribution and the static deflection of the end-effector module are computed and analyzed by using the computer-aided finite element method (FEM).

Development of a compact continuum tubular robotic system for nasopharyngeal biopsy

Traditional posterior nasopharyngeal biopsy using a flexible nasal endoscope has the risks of abrasion and injury to the nasal mucosa and thus causing trauma to the patient. Recently, a new class of robots known as continuum tubular robots (CTRs) provide a novel solution to the challenge with miniaturized size, curvilinear maneuverability, and capability of avoiding collision within the nasal environment. This paper presents a compact CTR which is 35 cm in total length, 10 cm in diameter, 2.15 kg in weight, and easy to be integrated with a robotic arm to perform more complicated operations. Structural design, end-effector design, and workspace analysis are described in detail. In addition, teleoperation of the CTR using a haptic input device is developed for position control in 3D space. Moreover, by integrating the robot with three electromagnetic tracking sensors, a navigation system together with a shape reconstruction algorithm is developed. Comprehensive experiments are conducted to test the functionality of the proposed prototype; experiment results show that under teleoperation, the system has an accuracy of 2.20 mm in following a linear path, an accuracy of 2.01 mm in following a circular path, and a latency time of 0.1 s. It is also found that the proposed shape reconstruction algorithm has a mean error of around 1 mm along the length of the tubes. Besides, the feasibility and effectiveness of the proposed robotic system being applied to posterior nasopharyngeal biopsy are demonstrated by a cadaver experiment. The proposed robotic system holds promise to enhance clinical operation in transnasal procedures.

Design and experiment of a universal space-saving end-effector for multi-task operations

Purpose – The purpose of this paper is to present the design and experiment of a universal space-saving end-effector for multi-task operations. Design/methodology/approach – The universal end-effector is equipped with capture and actuation transmission capabilities with two corresponding subsystems, which are highly integrated systems of mechanics, electronics and sensors. A trefoil-shaped capture system is developed for closed envelop. The worm gear pair is adopted for self-locking and space-saving, and it is used in a unique manner for three grapple chains’ synchronous motion. The combination of optimal straight path linkage and pantograph mechanism is proposed in the transmission system. The electrical structure and the multi-sensory system provide the foundation for control strategy. Findings – Simulations and experiments demonstrated characteristics of the universal end-effector. The compliance of the manipulator guaranteed the achievement of “soft capture” by the end-effector. Due to the self-locking property, the end-effector and the grapple interface could keep rigid connection when powered off. Practical implications – The design process takes practical requirements into consideration. Through experiments, it is proved that the proposed end-effector can be used for the multi-task operations with corresponding tools. Originality/value – Among end-effectors with operation function, the misalignment tolerance (MT) is originally regarded as a key factor. The adoptions of the worm gear pair and the linkage make it space-saving compared to conventional designs.

Design of End-effector for Tomato Robotic Harvesting

Abstract: In order to improve automatic harvesting for fresh-eating tomato, a new picking end-effector was designed, which mainly consisted of three parts, such as fruit holding, stem holding, and fruit separating. In view of the convenience of stemless fruit for transport and package, the end-effector separated the tomato fruit from the plant at the abscission layer between the stem and fruit. A sleeve with three equispaced gasbags was used as the flexible fruit-holding part, so as to fit the fruit’s various size and keep the holding force constant. Besides, the holding and separating force parameters were calculated based on the measuring result of the fruit material characteristics, so that the holding operation is reliable and nondestructive. Finally, the end-effector’s performance was tested, and the result showed the successful picking rate was 86%.

New design of a compact aero-robotic drilling end effector: An experimental analysis

This paper presents the development of a normal adjustment cell (NAC) in aero-robotic drilling to improve the quality of vertical drilling, by using an intelligent double-eccentric disk normal adjustment mechanism (2-EDNA), a spherical plain bearing and a floating compress module with sensors. After the surface normal vector is calculated based on the laser sensors’ feedback, the 2-EDNA concept is conceived specifically to address the deviation of the spindle from the surface normal at the drilling point. Following the angle calculation, depending on the actual initial position, two precise eccentric disks (PEDs) with an identical eccentric radius are used to rotate with the appropriate angles using two high-resolution DC servomotors. The two PEDs will carry the spindle to coincide with the surface normal, keeping the vertex of the drill bit still to avoid repeated adjustment and position compensation. A series of experiments was conducted on an aeronautical drilling robot platform with a precise NAC. The effect of normal adjustment on bore diameter, drilling force, burr size, drilling heat, and tool wear was analyzed. The results validate that using the NAC in robotic drilling results in greatly improved vertical drilling quality and is attainable in terms of intelligence and accuracy.

Preliminary Design of a Three-Finger Underactuated Adaptive End Effector with a Breakaway Clutch Mechanism

<div class=""abs_img""> <img src=""[disp_template_path]/JRM/abst-image/00270005/05.jpg"" width=""300"" /> A robotic end effector prototype</div> Commercially available robotic grippers are often expensive and not easy to modify for specific purposes of robotics research and education. To extend the choice of robotic end effectors available to researchers, this paper presents the preliminary work on prototype design and analysis of a three-finger underactuated robotic end effector with a breakaway clutch mechanism suitable for research in robot manipulation of objects for industrial and service applications. Kinematic models of the finger and the breakaway clutch mechanisms are analyzed aiming to define selection criteria of design parameters. Grasping performance of the end effector prototype manufactured with a 3D printing technology and off-the-shelf components is evaluated using simulation and experimental analyses. Comparison with widely applied available robotic end effectors shows the potential advantages of the proposed end effector design. </span>

Design, development and characterization of a modular end effector for MIS procedures.

The Minimally Invasive Surgery (MIS) paradigm is well established in modern surgical procedures. Although MIS is successful from the patient's viewpoint, the use of rigid instruments inserted through small skin incisions leads to dexterity constraints and loss of degree of motion. Robotics has been introduced as support for augmenting dexterity during interventions, restoring hand-eye coordination and providing tools with enhanced degrees of motion. However, surgical robots have high costs and large footprint, pushing the research towards the development of modular robots to be used in Naturally Orifice Trans-luminal Endoscopic Surgery (NOTES) procedures. The main need of having simple and cheap tools able to be interchanged during the surgical procedure became crucial. In this paper an innovative modular end-effector based on a compliant soft actuation system able to provide up to 5.78 N gripping forces is presented.

Development of novel magnetic grippers for use in unstructured robotic workspace

The workability of an industrial robotic system under non-coherent environment has attained commendable potential in recent era owing to the customized design of end-effectors. Magnetic gripping is one such domain that draws research interest, especially when used in unstructured robotic workspace. The present paper delineates the details of the design, modeling, analysis, fabrication paradigms and test results of representative magnetic grippers, including test-pieces and prototype, having provision for augmentation with industrial robot(s). The novelty of the present research lies with the design semantics of the various layouts of the magnetic gripper for a customized operation of lifting ferromagnetic work-pieces from an unstructured heap, made through Finite Element Analysis (FEA) as well as using contact mechanics-based grasp synthesis model. The test grippers were experimented using an indigenous laboratory set-up, working under both structured and unstructured environments. The prototype development of the sensor-instrumented magnetic gripper was made in-line with the test results and its workability under unstructured workspace was tested by deploying the robotic unit in an industrial shop floor.