Types Of End-effectors Research Articles

Key Technologies for Autonomous Fruit- and Vegetable-Picking Robots: A Review

With the rapid pace of urbanization, a significant number of rural laborers are migrating to cities, leading to a severe shortage of agricultural labor. Consequently, the modernization of agriculture has become a priority. Autonomous picking robots represent a crucial component of agricultural technological innovation, and their development drives progress across the entire agricultural sector. This paper reviews the current state of research on fruit- and vegetable-picking robots, focusing on key aspects such as the vision system sensors, target detection, localization, and the design of end-effectors. Commonly used target recognition algorithms, including image segmentation and deep learning-based neural networks, are introduced. The challenges of target recognition and localization in complex environments, such as those caused by branch and leaf obstruction, fruit overlap, and oscillation in natural settings, are analyzed. Additionally, the characteristics of the three main types of end-effectors—clamping, suction, and cutting—are discussed, along with an analysis of the advantages and disadvantages of each design. The limitations of current agricultural picking robots are summarized, taking into account the complexity of operation, research and development costs, as well as the efficiency and speed of picking. Finally, the paper offers a perspective on the future of picking robots, addressing aspects such as environmental adaptability, functional diversity, innovation and technological convergence, as well as policy and farm management.

Memory Efficient Deep Learning-Based Grasping Point Detection of Nontrivial Objects for Robotic Bin Picking

Picking up non-trivial objects from a bin with a robotic arm is a common task of modern industrial processes. Here, an efficient data-driven method of grasping point detection, based on an attention squeeze parallel U-shaped neural network (ASP U-Net) for the bin picking task, is proposed. The method directly provides all necessary information about the feasible grasping points of objects, which are randomly or regularly arranged in a bin with side walls. Moreover, the method is able to evaluate and select the optimal grasping point among the feasible ones for two types of end effectors, i.e., a vacuum cup and a parallel gripper. The key element of the utilized ASP U-Net neural network is the transformation of a single RGB-Depth image of the bin containing nontrivial objects into a schematic grey-scale frame, where the positions and poses of the grasping points are coded into gradient geometric shapes. The experiments carried out in this study include a comprehensive set of scenes with randomly scattered, ordered, and semi-ordered objects arranged in impeccable or deformed bins. The results indicate outstanding accuracy with more than acceptable computational requirements. Additionally, the scaling possibilities of the method can offer extremely lightweight implementations, applicable, for example, to battery-powered edge-computing devices with low RAM capacity.

Responsive Hydrogel-Based Modular Microrobots for Multi-Functional Micromanipulation.

Microrobots show great potential in biomedical applications such as drug delivery and cell manipulations. However, current microrobots are mostly fabricated as a single entity and type and the tasks they can perform are limited. In this paper, modular microrobots, with an overall size of 120 µm × 200 µm, are proposed with responsive mating components, made from stimuli-responsive hydrogels, and application specific end-effectors for microassembly tasks. The modular microrobots are fabricated based on photolithography and two-photon polymerization together or separately. Two types of modular microrobots are created based on the location of the responsive mating component. The first type of modular microrobot has a mating component that can shrink upon stimulation, while the second type has a double bilayer structure that can realize an open and close motion. The exchange of end-effectors with an identical actuation base is demonstrated for both types of microrobots. Finally, different manipulation tasks are performed with different types ofend-effectors.

Review of current mechanical design in agricultural end effector

Agricultural robots have become increasingly crucial in precise agriculture. This paper reviews recent developments in end-effectors applied in the robotic harvesting of fruits and vegetables. The control and harvest function of the end-effector is the focus. Different structures are categorized based on their properties. Advantages and limitations in each category are introduced. For the collection method, the hard-grab method is very popularly for low difficulties and the soft one can protect the fruits adequately and can harvest different fruits of similar size; double-finger type is used widely with the advantages of low cost, while the multi-finger type has the much higher stability. The collection method is divided into the cutting and twisting methods. The former is applied for low difficulties but may spread diseases among plants; therefore, thermal cutting, namely using high temperature to separate stem and crop, and the twisting method is used. Overall, different types of end-effectors show various advantages. With consideration of the target crop physical properties, a proper decision for the harvester can be made.

Design and Testing of Bionic-Feature-Based 3D-Printed Flexible End-Effectors for Picking Horn Peppers

To solve the problems of poor adaptability and large sizes of pepper harvesting machinery in facility agriculture to enhance the efficiency and quality of pepper harvesting and ultimately boost farmers’ income, several flexible end-effectors were designed. These end-effectors were tailored to the unique morphologies of horn peppers, drawing inspiration from biomimicry. Subsequently, we conducted experimental verification to validate their performance. Four biological features, namely, the outer contours of a Vicia faba L. fruit, an Abelmoschus esculentus fruit, the upper jaw of a Lucanidae, and a Procambarus clarkii claw, were selected and designed using 3D software. In order to ascertain the structural viability and establish the initial design framework for the test end-effector, a simulation analysis to evaluate the strength and deformation of the flexible end-effector under various pepper-picking conditions was conducted. PLA material and 3D printing technology were used to create the end-effector, and, together with the mobile robotic arm platform ROSMASTER X3 PLUS, they were used to build a test prototype; a pepper tensile test was performed to pre-determine the reasonableness of the picking program, and then a prototype was created for the actual picking of the peppers to compare the picking effectiveness of several types of flexible end-effectors. In six experiments, each flexible end was harvested for 120 horn peppers. The Vicia faba L. flexible end-effector had the lowest average breakage rate. The average breakage rate was 1.7%. At the same time, it had the lowest average drop rate. The average drop rate was 3.3%. The test results indicated that the flexible end-effector that emulated the outer contour characteristics of the Vicia faba L. fruit demonstrated the most favorable outcomes. This design exhibited high working efficiency and the lowest rates of fruit breakage and fruit drops, surpassing both the artificial and traditional machine picking methods and effectively fulfilling the requirements for pepper-picking operations in facility agriculture.

An Overview of End Effectors in Agricultural Robotic Harvesting Systems

In recent years, the agricultural sector has turned to robotic automation to deal with the growing demand for food. Harvesting fruits and vegetables is the most labor-intensive and time-consuming among the main agricultural tasks. However, seasonal labor shortage of experienced workers results in low efficiency of harvesting, food losses, and quality deterioration. Therefore, research efforts focus on the automation of manual harvesting operations. Robotic manipulation of delicate products in unstructured environments is challenging. The development of suitable end effectors that meet manipulation requirements is necessary. To that end, this work reviews the state-of-the-art robotic end effectors for harvesting applications. Detachment methods, types of end effectors, and additional sensors are discussed. Performance measures are included to evaluate technologies and determine optimal end effectors for specific crops. Challenges and potential future trends of end effectors in agricultural robotic systems are reported. Research has shown that contact-grasping grippers for fruit holding are the most common type of end effectors. Furthermore, most research is concerned with tomato, apple, and sweet pepper harvesting applications. This work can be used as a guide for up-to-date technology for the selection of suitable end effectors for harvesting robots.

Payload-adaptive iterative learning control for robotic manipulators

Abstract. The main purpose of the iterative learning control (ILC) method is to reduce the trajectory tracking error caused by an inaccurate model of the robot's dynamics. It estimates the tracking error and applies a learning operator to the output control signals to correct them. Today's ILC researchers are suggesting strategies for increasing the ILC's overall performance and minimizing the number of iterations required. When a payload (or a different end effector) is attached to a robotic manipulator, the dynamics of the robot change. When a new payload is added, even the most accurately approximated model of the dynamics will be altered. This will necessitate changes to the dynamics estimates, which may be avoided if the ILC process is used to control the system. When robotic manipulators are considered, this study analyses how the payload affects the dynamics and proposes ways to improve the ILC process. The study looks at the dynamics of a SCARA-type robot. Its inertia matrix is determined by the payload attached to it. The results show that the ILC method can correct for the estimated inertia matrix inaccuracy caused by the changing payload but at the cost of more iterations. Without any additional data of the payload's properties, the suggested technique may adjust and fine-tune the learning operator. On a preset reference trajectory, the payload adaptation process is empirically tested. When the same payload is mounted, the acquired adaptation improvements are then utilized for another desired trajectory. A computer simulation is also used to validate the suggested method. The suggested method increases the overall performance of ILC for industrial robotic manipulators with a set of similar trajectories but different types of end effectors or payloads.

A Smart robotic arm for harvesting olive fruits

This work introduces a smart robotic arm for harvesting olive fruits. The work started by planning the main steps. After deciding on the robot concept design, a kinematic and dynamic analysis is conducted. Based on the results of the analysis, a simulation is performed to determine the required specifications of the main components. Based on these results, an experimental model of the robot arm is designed, built, configured, and tested, where the model yielded good results. The next step is to configure and test different types of end effectors. In order to make the harvesting process effective for olive trees, picking a single fruit each time is not practical. Therefore, the procedure adopted in this work focuses on picking a group of fruit in each stroke. The harvesting system consists of a robotic arm guided by a stereovision camera to enable 3-D vision. Once the fruits location is detected, a reverse kinematics algorithm is initiated, yielding 3-points coordinates. These coordinates are commanded to the manipulator to move to the location and performs the picking process. Further developments will include building a larger manipulator that can reach out to all parts of a regular tree.

Design of robotic manipulator for space applications

The paper illustrates the various design parameters implemented on our robotic manipulator that enables its usage in an alien environment and for space exploration. The robotic manipulator features a light weight variable configuration arm design, high precision actuating parts, a customized power distribution grids, tele-motion control system and an unorthodox approach for obtaining inverse kinematic values. The high configurability of this arm enables it to perform different tasks efficiently under a single platform. The 6 DOF freedom arm is custom designed to specific configurations in order to provide considerable advantage over conventional manipulators used in space applications. The arm is equipped with 2 types of end effectors in an adaptive manner such that it can be utilized in grasping both symmetric to asymmetric objects.

Automated planning for robotic layup of composite prepreg

Hand layup is a commonly used process for making composite structures from several plies of carbon-fiber prepreg. The process involves multiple human operators manipulating and conforming layers of prepreg to a mold. The manual layup process is ergonomically challenging, tedious, and limits throughput. Moreover, different operators may perform the process differently, and hence introduce inconsistency. We have developed a multi-robot cell to automate the layup process. A human expert provides a sequence to conform to the ply and types of end-effectors to be used as input to the system. The system automatically generates trajectories for the robots that can achieve the specified layup. Using the cell requires the automated generation of different types of plans. This paper addresses two main planning problems: (a) generating plans to grasp and manipulate the ply and (b) generating feasible robot trajectories. We use a hybrid-physics based simulator coupled with a state space search to find grasp plans. The system employs a strategy that applies constraints successively in a non-linear optimization formulation to identify suitable placements of the robots around the mold so that feasible trajectories can be generated. Our system can generate plans in a computationally efficient manner, and it can handle a wide variety of complex parts. We demonstrate the automated layup by conducting physical experiments on an industry-inspired mold using the generated plans.

Analysis of the interaction between end-effectors, soil and asparagus during a harvesting process based on discrete element method

To meet the high-efficiency and low-damage harvesting requirements for white asparagus, two novel types of end-effectors were designed to selectively harvest white asparagus. One is the transverse-cut end-effector (TCEE), while the other is the clip-cut end-effector (CCEE). To select the best harvesting scheme and achieve a suitable range in driving forces, we propose a discrete element method (DEM)-based model of the end-effectors, soil and white asparagus for the comparative analysis of a harvesting process using two end-effectors. The biomechanical properties of white asparagus were measured to determine the constraints of non-damaging harvesting, after which we derived the theoretical driving forces of the two end-effectors. Combined with an analysis of DEM simulation, the driving forces of end-effectors are quantitatively described in this paper. A test bench was built to carry out field harvesting tests. Finally, after considering the comprehensive results of the simulations and field tests, we determined TCEE to be the final harvesting component. The validated experiment showed that the relative errors between the field test and the simulation, given the driving forces of penetration, shearing and clamping, were 6%, 11.9% and 18.2%, respectively. This proves that the DEM model is capable of simulating the biomechanical properties of white asparagus, and can be used to simulate the harvesting process. The optimum combination of driving force parameters for TCEE is penetration force 200N, shearing force 4.2N and clamping force 11N. Under this scheme, the harvesting process met the requirements for high efficiency and low damage, which demonstrates the effectiveness of the white asparagus robotic harvester.

EVALUATION OF POSSIBILITIES TO IMPROVE RIGID BODIES

Manipulators are used for various purposes in order to simplify tasks or reduce the risk of tasks that are considered impossible, dangerous or difficult for humans. The robotic arm can be equipped with various types of end effectors to perform a variety of tasks. Grips are one of the most commonly used tools for manipulators. This article discusses the analysis of modeling new robotic gripping fingers, based on models of gripping gross rigid bodies of manipulators. A literature review was conducted in the relevant branches of scientific research. The ability to minimize dimensions and masses, as well as the final cost of the product, using available materials and electromechanical devices, various sensors, is evaluated. The external characteristics that make the previously developed analogues ineffective are analyzed. Modeling was released using the SolidWorks software package.

A Computational Framework for Designing Skilled Legged-Wheeled Robots

Legged-wheeled robots promise versatile, fast and efficient mobile capabilities. To unleash their full potential, however, such hybrid robots need to be designed in a way that promotes the complex, full-body motions required for novel locomotion modes. This letter discusses the computational framework we have used to create a new type of legged robot which, when equipped with different types of end effectors, is capable of an array of interesting locomotory behaviors, including walking, roll-walking, roller-blading, and ice-skating. We show that this computational framework, which builds on a design system we recently introduced in the computer graphics community [1] , can accurately predict the way in which different design decisions affect the robot's ability to move, thus serving as an important tool in engineering new types of mobile robots. We also propose a novel warm-starting method which leverages ideas from numerical continuation to drastically improve convergence rates for the trajectory optimization routine we employ to generate optimal motions.

Double-arm optical tweezer system for precise and dexterous handling of micro-objects in 3D workspace

Double-arm manipulators are unfamiliar as equipment used in microscopic work in biomedical laboratories, whereas they are prevalent in factory automation and humanoids. For non-contact micromanipulation in three-dimensional (3D) workspaces, we propose and design a double-arm optical tweezer system that can easily exchange two types of end-effectors (i.e., optical landscapes for laser trapping) with a focus tunable lens and a microlens array. With a time-shared scanning approach under interactive personal computer (PC) mouse controls, the system can perform the precise and dexterous handling of micro-objects in a 3D workspace. As a proof of concept, we demonstrate the two-dimensional (2D) and 3D dexterous handling of microbeads in the motions of solving puzzle rings. We also demonstrate the precise and periodic patterning of microbeads for massive dynamic arrays. This double-arm system can be applied with versatile tools used for various non-contact micromanipulations in the biomedical field and for dynamic arrays in single cell and 3D biology.

General Construction and Classification of Manipulators for Underwater Vehicles

Abstract The article presents the general construction of an underwater vehicle manipulator along with a discussion of the materials used in their construction. The types of drive systems used by the manipulator have been characterised, distinguishing their advantages and disadvantages. The functions of the manipulator are specified in relation to the activities performed by it. Moreover, the paper discusses the manipulator's degrees of freedom with the specification of the formula for their calculation. The basic types of end effectors are presented as well as an outline of the classification of manipulators in relation to the tasks carried out.

Performance Evaluation of a Harvesting Robot for Sweet Pepper

This paper evaluates a robot developed for autonomous harvesting of sweet peppers in a commercial greenhouse. Objectives were to assess robot performance under unmodified and simplified crop conditions, using two types of end effectors (Fin Ray; Lip type), and to evaluate the performance contribution of stem‐dependent determination of the grasp pose. We describe and discuss the performance of hardware and software components developed for fruit harvesting in a complex environment that includes lighting variation, occlusions, and densely spaced obstacles. After simplifying the crop, harvest success significantly improved from 6% to 26% (Fin Ray) and from 2% to 33% (Lip type). We observed a decrease in stem damage and an increase in grasp success after enabling stem‐dependent determination of the grasp pose. Generally, the robot had difficulty in successfully picking sweet peppers and we discuss possible causes. The robot's novel capability of perceiving the stem of a plant may serve as useful functionality for future robots.

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.

Nanoscale Manipulators: Review of Conceptual Designs Through Recent Patents.

Nanomanipulation techniques have gone through several phases to be used in scientific explorations not only to reveal more characteristics of nano, micro and mesoscopic phenomena but also to build functional nano-devices useful for specific applications. The nano-manipulator becomes a key instrument for technology bridging between sub-nano and mesoscale. The recent patents have exhibited integration of various functions in the nano-devices requiring sub-nanometer precision and highly stable manipulator with substantial pulling/pushing forces. This work reviews patents and works on conceptual designs of existing nanomanipulators with specific features. This includes design analysis leading to ultra-precision motion and stability with discussion of enabling technology. A novel integrated and numerically controlled instrument for nanomanipulation, visualization and inspection/characterization of materials at sub-nanoscale will be presented with a feature to keep the same datum for all operation and hence improve accuracy of samples. This paper has undertaken a review search in a structured examination of bibliographic databases for published and issued patents using a focused review keyword of nano-manipulation. The quality of selected patents was appraised using standard tools. The characteristics of screened patents were described, and a deductive qualitative content analysis methodology was applied to understand the modeling and testing of nanomachining process, the exact construction of nanostructure arrays and the inspection of devices with complex features. The paper encompassed forty patents. Fourteen patents exhibited the manipulation at the micro scale (MEMS manipulations), others outlined systems with sub-micron resolution and workspace range in mesoscale. Standard scale manipulation were described in 13 patents assuming only systems comprising positioning stages, arms and end-effectors where positioners are a few centimeters in size with workspace higher than one cm3. Finally, ten patents included in this review described the importance of end-effectors being extremely important in nanomanipulation as they do support the function defining the manipulation e.g. grippers, sprayers, Nano-tweezers. The findings of this patents review confirm the relevance of the nanomanipulation of objects in 3D system coupled with real time imaging having higher resolution in comparison with the standard manipulators including AFM, TEM, STM, SEM or NSOM. In terms of tooling, AFM cantilever tips, etched tungsten tips or tips with electron beam deposition can be used to manufacture or develop nanodevices e.g. nanowires in in-situ SEM. In handling and manipulating in ambient conditions, commercial microfabricated grippers although available, are less used compared to CNT nanotweezers. Nanomanipulation is currently enabled for nanoscale samples by on-chip operations using promising MEMS and NEMS devices to relatively large samples by the meso and standard scale nanomanipulators. Manipulation is comprehensive and requires multiple functions enabled by various types of end-effectors and probes actuated with high precision. Piezo actuators are at the moment of great performance. Nano and sub-nano samples require proper environment e.g, with electron microscopy to monitor and manipulate including testing, inspecting and fabricating and assembling.

Design of endoscopic micro-robotic end effectors: safety and performance evaluation based on physical intestinal tissue damage characteristics

During the last several years, legged locomotive mechanism has been considered as one of the main self-propelling mechanisms for future endoscopic microrobots due to its superior propulsion efficiency of an endoscopic microrobot inside the intestinal track. Nevertheless, its clinical application has been largely limited since the legged locomotive mechanism utilizes an end effector which has a sharp tip to generate sufficient traction by physically penetrating and interlocking with the intestinal tissue. This can cause excessive physical tissue damage or even complete perforation of the intestinal wall that can lead to abdominal inflammation. Hence, in this work two types of new end effectors, penetration-limited end effector (PLEE) and bi-material structured end effector (BMEE) were specially designed to acquire high medical safety as well as effective traction generation performance. The microscopic end effector specimens were fabricated with micro-wire electric discharge machining process. Traction generation performance of the end effectors was evaluated by direct measurement of resistance forces during contact-sliding tests using a custom-built contact-sliding tester. The safety of the end effector design was evaluated by examination of microscopic intestinal tissue damage using a scanning electron microscope (SEM). Physical damage characteristics of the intestinal tissue and related contact physics of the end effectors were discussed. From the results, the end effectors were evaluated with respect to their prospects in future medical applications as safe end effectors as well as micro-surgical tools.

Development of a Robotic System which Assists Unmanned Production Based on Cooperation between Off-Line Robots and On-line Robots. Part 3. 1 Development of an Off-Line Robot, Autonomous Navigation, and Detection of Faulty Workpieces in a Vibrating Parts Feeder

Remarkable advances in robotics and intelligent technology have made unmanned production realisable. Based on the off-line robot concept proposed in our first paper, an off-line robot and peripheral devices have been developed for the realisation of unmanned production. The developed robot has a power-wheeled steering (PWS) type mobile platform on which a double-arm manipulator is installed. In order to detect and recognise 3D objects, double CCD cameras are mounted on the top of the robot. Two types of robot end-effectors are developed to handle workpieces and conduct trouble shooting actions. A newly developed production trouble simulator is very useful in simulating and resolving production troubles. A virtual pilot plant for production composed of the off-line robot, two on-line robots, a vibrating bowl feeder, a belt conveyor and a production trouble simulator has been constructed and tests for production simulation have been undertaken. In this paper, autonomous navigation of the developed robot in the virtual pilot plant is investigated. Then a search for faulty parts in a parts feeder using the developed real-time image extraction method is carried out.