Design Of End-effector Research Articles

Effect of Soil Moisture Content and End-Effector Speed on Pick-up Force and Lump Damage for Seedling Transplanting

Efficient transplanting has been identified as one of the essential steps towards achieving an increased yield in the farm. However, many factors are affecting these processes such as soil moisture content and the speed of pickup. This study was carried out to investigate the effect of different soil moisture content and pickup speeds on pickup force, balance, resistance, and lump damage during transplanting of seedlings. The results showed that penetration resistance was inversely proportional to the speed and soil moisture content. The highest penetration resistance (38 N) values were recorded under the lowest speed (0.5 mm/s) at the low moisture content; whereas, the lowest penetration resistance was obtained at highest speed (10 mm/s) under high moisture content. The highest pick-up force resistance values were recorded under the lowest speed (0.5 mm/s) at low moisture content than the lowest pick-up force resistance of 1.4 N at (10 mm/s) under the high moisture content. On the other hand, an increase of pick-up force led to a decrease in the pick-up force resistance. The pick-up damage and the pick-up speed are directly proportional—nevertheless, the former increased with a decreasing soil moisture content. The highest pick-up damage values (82%) were observed under the top-most speed (10 mm/s) at high moisture content. It can be concluded that for successful auto-transplanting of seedling the soil condition, the force applied and speed should be taken into consideration. This work will implement an effective seedling-picking performance and basis for the optimal design of end-effectors.

De-electroadhesion of Flexible and Lightweight Materials: An Experimental Study

Electroadhesion (EA) is an emerging prehension method with wide application in robotics, including object handling, component assembly, and robotic locomotion. A major challenge with EA is the development of novel solutions for speeding up the release process, where residual charges inhibit release. In this work, a comprehensive study on the effects of EA base substrate and object material types on de-electroadhesion time is presented. Experimental results show that the de-electroadhesion speed is highly dependent on the base substrate and object material type. There is a strong inverse correlation between dielectric constant and de-electroadhesion rate, while a higher molecular weight demonstrates slower dielectric relaxation and hence release time. These findings will enable the design of cost-effective EA-based robotic end effectors with rapid release capabilities. EA grippers with quicker de-adhesion abilities could significantly improve the overall throughput of assembly lines where material pick-and-place tasks are involved. In addition, more efficient and faster locomotion speeds could be achieved for crawling or climbing robots where EA is employed as their active adhesion and de-adhesion feet.

An anthropometric study for the anthropomorphic design of tomato-harvesting robots

To explore how humans can dexterously pick fruits of various sizes from a tomato plant from different positions and postures, some anthropometric dimensions related to the hand-harvesting of the fruits were determined within 261 volunteers, and their correlations were investigated using a bivariate correlation analysis method. The heights of the body (stature), shoulder tip, waist and knee of participants ranged from 111.2 to 193.6, 87.5 to 163.0, 62.1 to 117.3, and 31.0 to 56.0 cm, respectively; the ratios of the knee height, waist height, and shoulder tip height to the stature were 0.25–0.33, 0.52–0.65, and 0.76–0.87, respectively; the shoulder tip breadth, upper limb length and foot length of participants ranged from 26.0 to 48.5, 45.4 to 85.6, and 19.5 to 28.0 cm, respectively; and the length ratios of the hand, forearm, and upper arm to the upper limb were 0.23–0.31, 0.29–0.38, and 0.35–0.45, respectively. There were high linear correlations among the stature, waist height and knee height, between the forearm and hand lengths, and among the stature, hand length and arm length and moderate linear correlations between most hand dimensions. These human body dimensions determine the upper limb workspace, body balance, working comfort and lower limb movement frequency during picking, and this information will be useful for the bionic dimensional synthesis design of a harvesting robotic arm, walking mechanism and body. The results of multiple comparisons in ANOVA showed that there were significant differences between some of the finger dimensions and between some of the hand-scaling dimensions, which is one of the main features enabling the human hand to pick various sizes of fruits. This study can provide guidance and inspiration for the anthropomorphic design of robotic tomato-harvesting end-effectors.

External Force Self-Sensing Based on Cable-Tension Disturbance Observer for Surgical Robot End-Effector

The external force sensing ability of the end-effector plays a significant role in restricting the refine operation of a surgical robot. This paper proposes an external force self-sensing method based on the cable-tension disturbance observer for a four-degree-of-freedom (4-DoF) surgical robot end-effector, which is actuated by three backdrivable cable-driven series elastic actuators (BCDSEAs). First, the design of the surgical robot end-effector is introduced with the experimental prototype of a 1-DoF flexible finger joint. Second, four kinds of dynamic models of the flexible finger joint are established and experimentally identified. A joint angle estimator is proposed based on a simplified dynamic model. Then, a closed-loop motion control method for the flexible finger joint is proposed. Third, a driving cable-tension estimator is constructed as the benchmark for the cable-tension disturbance observer under free motion. Meanwhile, an external force self-sensing estimator is proposed based on the motion control strategy and the cable-tension disturbance observer. Finally, the experimental results of joint tracking control present a good performance. The compensation algorithm for the external force under free motion is studied to reduce the system error. The experimental results of the external force self-sensing show an overall estimation accuracy of 85.97% with a range of 0.10–2.00 N.

Angle estimation between plant parts for grasp optimisation in harvest robots

For many robotic harvesting applications, position and angle between plant parts is required to optimally position the end-effector before attempting to approach, grasp and cut the product. A method for estimating the angle between plant parts, e.g. stem and fruit, is presented to support the optimisation of grasp pose for harvest robots. The hypothesis is that from colour images, this angle in the horizontal plane can be accurately derived under unmodified greenhouse conditions. It was hypothesised that the location of a fruit and stem could be inferred in the image plane from sparse semantic segmentations. The paper focussed on 4 sub-tasks for a sweet-pepper harvesting robot. Each task was evaluated under 3 conditions: laboratory, simplified greenhouse and unmodified greenhouse. The requirements for each task were based on the end-effector design that required a 25° positioning accuracy. In Task I, colour image segmentation for classes back-ground, fruit and stem plus wire was performed, meeting the requirement of an intersection-over-union > 0.58. In Task II, the stem pose was estimated from the segmentations. In Task III, centres of the fruit and stem were estimated from the output of previous tasks. Both centre estimations In Tasks II and III met the requirement of 25 pixel accuracy on average. In Task IV, the centres were used to estimate the angle between the fruit and stem, meeting the accuracy requirement of 25° for 73% of the cases. The work impacted on the harvest performance by increasing its success rate from 14% theoretically to 52% in practice under unmodified conditions.

CUBE, a Cable-driven Device for Limb Rehabilitation

In this paper, a novel cable-driven parallel robot, CUBE, is introduced for the assistance of patients in rehabilitation exercising of both upper and lower limbs. The system is characterized by a lightweight structure that is easy to set-up and operate, for both clinical and home usage for both pre-determined and customized exercises, with control over the position of the end-effector while locking its rotation around the horizontal axes. Its cable-driven design makes it inherently safe in human/robot interactions also due to the extremely low inertia. While a novel end-effector design makes the device wearable both on the upper and lower limbs without having to disassemble any part of the structure. The design is presented with its kinematic analysis. Then, the manufacturing through 3D-printing and commercial components of a first prototype is reported. Finally, the system is validated through motion tests along simple trajectories and two different spatial exercises.

Design and Validation of a Reconfigurable Robotic End-Effector Based on Shape Memory Alloys

Thermal shape memory alloy (SMA) actuators are known for their superior energy density (force–volume ratio) compared to other actuation principles, allowing the construction of lightweight and compact systems. Furthermore, SMA actuators can be used as sensors, as their electrical resistance changes during activation. Using this multifunctionality, this work aims at presenting the development, fabrication, and validation of an SMA-driven robotic end-effector. The end-effector prototype is designed in a modular concept and consists of four independent arms with two degrees of freedom (DOF). Each arm can rotate in-plane and also tilt out-of-plane to allow gripping of various workpiece geometries. Both DOF actuator components consist of an SMA wire working against a tension spring. The tilting joint has an additional mechanism that creates two energy-free rest positions to improve energy efficiency. The end-effector is designed to carry a maximum load of 10 kg. In a test bench for the validation of the SMA-driven end-effector joints, hall sensors are used to measure the gripping arm displacement. In addition, the resistance of the SMA wires is monitored during activation. The dynamic system performance is analyzed using different activation current levels. Finally, a proportional integral (PI) control with Hall sensor feedback is implemented to position the first DOF at arbitrary angles within its 90° rotation radius.

PEMODELAN DAN ANALISA STRUKTUR MEKANIKA PADA KONTROL SISTEM ADAPTIF END EFFECTOR DENGAN DYNAMIXEL AX-18A MOTOR SERVO

<p>The main objective of this project is to make a descriptive contribution to the understanding of adaptive end-effector design combined with servo motors. The simulation and design of this tool is located at the end of the robotic arm, which is one of the most researched topics in the world of robotics and the automation industry. End-effector is a design system in an automation process that must take into account the many possibilities of statics and mechanical responses in the development of facing intense competition in the industrial world. To determine the enhancements on a robot, the end-effector will be designed taking into account the various possibilities that occur in various variations on the workpiece response, so that it can simulate various levels of friction and pressure as well as the effects of end-effector contacts with various objects. This thesis introduces an integrated design process for the design of two-finger Gripper using simulation. To facilitate the integrated design of the Gripper, the author uses Matlab R2015a software<br />/ Simulink (SimMechanics) and Inventor as a 3D Cad Model. The Servo motor that will be used here is a type of Dynamixel AX-18A servo motor which has a speed of 97RPM and Torque of 1.8 N.m with a 12Volt voltage. To deal with the industrial revolution 4.0, design and design such as this tool will help in the process of improvisation as technology is growing rapidly in the hope of minimizing excessive costs when making improvements. From this thesis can be seen the power response, torque, speed, power in, power out, efficiency and current. When a case requires certain specifications, then with this calculation it can easily solve the problem simply by replacing the motors that are in accordance with the desired specifications.</p>

Design and Analysis of a Soft Finger end Effector for Industrial Purpose

Design and Analysis of a Soft Finger end Effector for Industrial Purpose

Design and Field Evaluation of a Robotic Apple Harvesting System with a 3D-Printed Soft-Robotic End-Effector

Abstract. Fresh market apple harvesting is a difficult task that relies entirely on manual labor. Much research has been done on the development of mechanical harvesting techniques. Several selective harvesting robots have been developed for research studies, but there are no commercially available robotic systems. This article discusses the design and development of a novel pneumatic 3D-printed soft-robotic end-effector to facilitate apple separation. The end-effector was integrated into a robotic system with five degrees of freedom that was designed to simplify the picking sequence and reduce costs compared to previous versions. Apples were successfully harvested using the low-cost robotic system in a commercial orchard during the fall 2017 harvest. A detachment success rate on attempted apples of 67% was achieved, with an average time of 7.3 s per fruit from separation to storage bin. By conducting this study in an orchard where problematic apples were not removed to increase the detachment success rate, current pruning and thinning practices were assessed to help lay the foundation for future studies and develop strategies for successfully harvesting apples that are difficult to detach. Keywords: Apple catching, Apples, Automated harvesting, Field experimentation, Harvesting robot, Soft-robotic gripper.

Sensing and Automation in Pruning of Apple Trees: A Review

Pruning is one of the most important tree fruit production activities, which is highly dependent on human labor. Skilled labor is in short supply, and the increasing cost of labor is becoming a big issue for the tree fruit industry. Meanwhile, worker safety is another issue in the manual pruning. Growers are motivated to seek mechanical or robotic solutions for reducing the amount of hand labor required for pruning. Identifying tree branches/canopies with sensors as well as automated operating pruning activity are the important components in the automated pruning system. This paper reviews the research and development of sensing and automated systems for branch pruning in apple production. Tree training systems, pruning strategies, 3D structure reconstruction of tree branches, and practice mechanisms or robotics are some of the developments that need to be addressed for an effective tree branch pruning system. Our study summarizes the potential opportunities for automatic pruning with machine-friendly modern tree architectures, previous studies on sensor development, and efforts to develop and deploy mechanical/robotic systems for automated branch pruning. We also describe two examples of qualified pruning strategies that could potentially simplify the automated pruning decision and pruning end-effector design. Finally, the limitations of current pruning technologies and other challenges for automated branch pruning are described, and possible solutions are discussed.

Synergistic integrated design of an electrochemical mechanical polishing end-effector for robotic polishing applications

Abstract In this paper, we present a novel design of a robotic electrochemical mechanical polishing (ECMP) process. Firstly, the process is presented to replace the conventional ECMP process by a robotic-based one. The advantage of using industrial robots lies in their flexibility, reconfigurability, large workspace and low prices compared to the conventional systems. Secondly, a novel design of a force-controlled end-effector for this purpose is presented. The end-effector is integrated into a macro-mini robot polishing cell. The macro robot (an industrial robotic manipulator) is used to position the mini robot (the proposed end-effector) according to the workpiece profile while the mini robot controls the polishing force. The effectiveness of the proposed device to polish un-milled and milled surfaces has been examined through polishing experiments. The results demonstrate the effectiveness of the presented device to reduce the surface roughness and improve the reflectability and appearance.

Miniaturized Robotic End-Effector with Piezoelectric Actuation and Fiber Optic Sensing for Minimally Invasive Cardiac Procedures.

Each year 35,000 cardiac ablation procedures are performed to treat atrial fibrillation through the use of catheter systems. The success rate of this treatment is highly dependent on the force which the catheter applies on the heart wall. If the magnitude of the applied force is much higher than a certain threshold the tissue perforates, whereas if the force is lower than this threshold the lesion size may be too large and is inconsistent. Furthermore, studies have shown large variability in the applied force from trained physicians during treatment, suggesting that physicians are unable to manually regulate the levels of the force at the site of treatment. Current catheter systems do not provide the physicians with active means for contact force control and are only at most aided by visual feedback of the forces measured in situ. This paper discusses a novel design of a robotic end-effector that integrates mechanisms of sensing and actively controlling of the applied forces into a miniaturized compact form. The required specifications for design and integration were derived from the current application under investigation. An off-the-shelf miniature piezoelectric motor was chosen for actuation, and a force sensing solution was developed to meet the specifications. Experimental characterization of the actuator and the force sensor within the integrated setup show compliance with the specifications and pave the way for future experimentation where closed-loop control of the system can be implemented according to the contact force control strategies for the application.

Design of an Apple-Picking End Effector

Design of an Apple-Picking End Effector

Design and optimization of a novel rescue end-effector

This paper describes the design of a novel multi-functional rescue end-effector with tonging, shearing and grasping capabilities to meet the demands of urban catastrophe rescue applications. The tonging and shearing form and the grasping form of the end-effector are analysed. The two forms are determined using the transformations of their grasping mechanisms. Four objectives (to maximize shearing space, minimize mass, minimize the equivalent stress and minimize deformation) are proposed for selection of the optimal grasping mechanism structure. Additional objectives also involve the end-effector’s structural strength and kinematic characteristics. A nested optimization structure that is composed of the non-dominated sorting genetic algorithm II (NSGA-II) and finite element analysis is proposed to perform multi-domain and multi-objective optimization of the end-effector. To improve the optimization efficiency, a traditional synthesis technique and a sensitivity analysis are applied to reduce the outer and inner numbers of the design variables. Simulation results indicate that the values of the four target objectives are superior to those before optimization and two referenced objectives, and the end-effector mass in particular, can evidently be reduced.

Development and Robustness Characterization of a Digital Material Assembly System

Digital material structures are lattices composed of discrete elements that are connected to create assemblies that can exhibit high performance mechanical characteristics. This paper presents the development and robustness characterization of a system, called Gantry Autonomous Robotic Integrator (GARI), which is designed to automatically assemble these structures. The relative positioning tolerance for connecting elements and methods to increase the reliability of automated assembly of these structures are specifically described. A compact end-effector design is presented, which shows high precision and adjustability, and calibration procedures for the build plate are defined. The bolting reliability for this end-effector is analyzed to identify tolerance requirements and establish performance benchmarks for component feed stations. Two extremal cases to test the bolting reliability of the end-effector are explored, one case with a well-constrained target voxel and the other case with a minimally constrained target voxel. The resulting bolting success tolerance maps are described, which indicate greater than 95% successful bolting probability within 0.254 mm in all directions from nominal target placement.

Design and Testing of a Kiwifruit Harvester End-Effector

Abstract. Mechanisms to aid fruit harvesting are undergoing constant development with increasing available technologies. However, fruits grown on vines, such as kiwifruit, have complex tree architectures and present difficulties in confirming design parameters. The objective of this research was to develop an end-effector for a kiwifruit harvester based on integrating the physical characteristics of the fruit, such as stem length, the space between mature fruits, and the growing environment provided by a trellised system into the design. These properties contribute to developing a mechanism that is lightweight, battery operated, and requires only one translational joint for positioning. Scissor cutting actuated by a linear solenoid is used to provide the required torque of 1.38 Nm to completely sever Hayward variety kiwifruit at the stem using a curved blade with a 20° relief angle. The cutting of the stem is actuated by a force sensor located on the device that enables cutting at less than 10 N, preventing premature detachment of the fruit and damage to the vine. The cutting time was measured to be 0.1 s ±0.03 s per cut. This end-effector design adds to the body of research aimed at developing a fully mechanized kiwifruit harvester. Keywords: Detachment force, End-effector, Fruit harvester, Kiwifruit, Linear solenoid.

Design of a Magnetic Resonance-Safe Haptic Wrist Manipulator for Movement Disorder Diagnostics

Tremor, characterized by involuntary and rhythmical movements, is the most common movement disorder. Tremor can have peripheral and central oscillatory components which properly assessed may improve diagnostics. A magnetic resonance (MR)-safe haptic wrist manipulator enables simultaneous measurement of proprioceptive reflexes (peripheral components) and brain activations (central components) through functional magnetic resonance imaging (fMRI). The presented design for an MR-safe haptic wrist manipulator has electrohydraulic closed-circuit actuation, optical position and force sensing, and consists of exclusively nonconductive and magnetically compatible materials inside the MR-environment (Zone IV). The MR-safe hydraulic actuator, a custom-made plastic vane motor, is connected to the magnetic parts and electronics located in the shielded control room (Zone III) via hydraulic hoses and optical fibers. Deliberate internal leakage provides backdriveability, damping, and circumvents friction. The manipulator is completely MR-safe and therefore operates safely in any MR-environment while ensuring fMRI imaging quality. Undesired external leakage in the actuator prevented the use of prepressure, limiting the control bandwidth. The compact end effector design fits in the MR-scanner, is easily setup, and can be clamped to the MR-scanner bed. This enables use of the manipulator with the subject at the optimal fMRI location and allows it to be setup quickly, saving costly MR-scanner time. The actuation and sensor solutions performed well inside the MR-environment and did not deteriorate image quality, which allows for various motor control experiments. Enabling prepressure by carrying out the recommendations on fabrication and sealing should improve the bandwidth and fulfill the requirements for proprioceptive reflex identification.

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.