Flexible End-effector Research Articles

Design and Optimization of Electromagnetically Driven End-Effector

The excellent flexibility and plasticity of a flexible robotic hand enable it to grip objects of various shapes and sizes. Currently, most of the flexible robotic hand fingers on the market use pneumatic drives. However, the unstable power of the pneumatic drive can cause the object gripped by the finger to slip. Additionally, the pneumatic pump can create noise pollution. To address these issues, a flexible end-effector is designed using an electromagnetic coil as the power source. The electromagnetic-driven end-effector has high precision and fast response, without the need for external devices. It only requires controlling the current to control the magnetic force of the electromagnet, thereby controlling the degree of end-effector bending. The finite element simulation is used to analyze the impact of the structural parameters of the end-effector on bending degree. And the optimal basic parameters of the end-effector are determined. Under the same intensity of the current, when the bottom layer thickness is 5 mm, end-effector knuckle spacing is 4 mm, the maximum angle of end-effector bending is reached.

An automatic robot for ultrasonic partial discharge detection of gas-insulated switchgear

PurposeGas-insulated switchgear (GIS) stands as a pivotal component in power systems, susceptible to partial discharge occurrences. Nevertheless, manual inspection proves labor-intensive, exhibits a low defect detection rate. Conventional inspection robots face limitations, unable to perform live line measurements or adapt effectively to diverse environmental conditions. This paper aims to introduce a novel solution: the GIS ultrasonic partial discharge detection robot (GBOT), designed to assume the role of substation personnel in inspection tasks.Design/methodology/approachGBOT is a mobile manipulator system divided into three subsystems: autonomous location and navigation, vision-guided and force-controlled manipulator and data detection and analysis. These subsystems collaborate, incorporating simultaneous localization and mapping, path planning, target recognition and signal processing, admittance control. This paper also introduces a path planning method designed to adapt to the substation environment. In addition, a flexible end effector is designed for full contact between the probe and the device.FindingsThe robot fulfills the requirements for substation GIS inspections. It can conduct efficient and low-cost path planning with narrow passages in the constructed substation map, realizes a sufficiently stable detection contact and perform high defect detection rate.Practical implicationsThe robot mitigates the labor intensity of grid maintenance personnel, enhances inspection efficiency and safety and advances the intelligence and digitization of power equipment maintenance and monitoring. This research also provides valuable insights for the broader application of mobile manipulators in diverse fields.Originality/valueThe robot is a mobile manipulator system used in GIS detection, offering a viable alternative to grid personnel for equipment inspections. Comparing with the previous robotic systems, this system can work in live electrical detection, demonstrating robust environmental adaptability and superior efficiency.

Development, integration, and field evaluation of an autonomous Agaricus bisporus picking robot

The disorganized and densely growing Agaricus bisporus remains challenging for robotic harvesting. Aiming at the lower efficiency, lower success rate, and higher breakage rate in the robotic harvesting process, we propose a fully integrated, autonomous, and innovative harvesting robot to overcome the challenges due to the dense growth characteristics of Agaricus bisporus. An overlapping target detection vision system based on the yolov5s deep learning network is developed to improve the detection accuracy of dense and hidden mushrooms. An intelligent picking planning strategy by fusing multiple algorithms is formulated to guide the robot to effectively pick mushroom clusters with different growth characteristics. A multi-stage telescopic flexible end-effector is designed to pick mushrooms in a narrow space and reduce the picking breakage rate. Finally, we successfully developed a fully autonomous picking robotic system and evaluated it in a mushroom cultivation factory. Experimental results show that the robot can pick Agaricus bisporus continuously with an overall success rate of 94.1 % and an average picking time of 4.23 s per mushroom. These efforts provide a solid foundation for future applications of Agaricus bisporus picking robots.

Pressure-Stabilized Flexible End-Effector for Selective Picking of Agaricus bisporus

Agaricus bisporus is widely cultivated worldwide due to its considerable economic benefits. The increasingly prominent contradiction between production and labor shortage necessitates the urgent replacement of human workers with intelligent picking technology and equipment. Therefore, a pressure-stabilized flexible end-effector was designed to achieve the rapid and low-loss picking of Agaricus bisporus. The dimensions of the end-effector were determined by measuring the external parameters of Agaricus bisporus. A mechanics model of the end-effector was constructed to analyze the picking process theoretically, and the pre-experiments identified the key performance factors of the end-effector: the thickness of the flexible membrane, the particle filler material, and the pressure stability. A series of experiments were conducted to investigate the factors mentioned above concerning the performance of the end-effector. The results show that the adsorption effect is best when the thickness of the flexible membrane is 0.9 mm, and the particle diameter is 200 mesh quartz. To control the adsorption force of the end-effector accurately during the picking process, a low-cost adsorption force-adjustment system was designed, and the stability of the system was verified. The experimental results showed that the device improved the stability of the adsorption force during the operation of the picking system by 84.71%. An experiment was conducted on the picking of Agaricus bisporus using the designed end-effector. The success rate of picking with the end-effector was 98.50%, and the picking damage rate was 2.50%.

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.

Optimal Design of a Cable Driven Parallel Robot for Upper Limb Rehabilitations

A novel cable driven parallel robot is introduced to assist upper limb in rehabilitation treatments in this paper, which has a lightweight structure. This robot is characterized by a novel and flexible end-effector that is easy to change assembly for different therapies. And it is designed for desktop usage, so its size is not too large. After presenting the structure, the kinematic model is presented for optimal design. Then, the minimal singular value is considered as the velocity transmission index. For upper limb rehabilitation, a new optimal design problem with the transmission index and the robot size is formulated. Last, the optimization presents a design with satisfying performances in velocity transmission capability and robot size.

Modeling and Force Analysis of a Harvesting Robot for Button Mushrooms

With the improvement of the quality of life, the demands on button mushroom (Agaricus Bisporus) increase significantly. But traditional farming methods mainly rely on costly human picking, which is currently facing the time-consuming and labor-intensive problem. As machine vision technology becomes more mature, harvesting robot with flexible picking end-effector is an alternative method to address this issue. Though the conventional harvesting robot is capable of mushrooms picking, but the damage rate is relatively high for the improper picking force and motion. Thus, a novel picking end-effector for button mushrooms is designed based on vacuum negative pressure picking in this paper. The harvesting robot with flexible end-effector is proposed to solve the problem: 1) to avoid the injury when the end-effector touch the mushroom; 2) to increase the picking efficiency without damage rate increase. The structure of robotic mushroom picking end-effector is described in detail, and then the kinematic modeling and picking force analysis of this robot are presented. Lastly, the numerical simulation via the MATLAB is carried out to study the influence of the robot parameters. The bruise tests indicated that the maximal allowable stress is 0.196 MPa and mean allowable pressure is 13.82 N. Preliminary results demonstrate that the robot achieved 88.2% success rate and 2.9% damage rate in the factory environment, and there is potential for the automatic mushroom harvesting with the proposed harvesting robot.

Design of a flexible end-effector based on characteristics of tomatoes

The end-effector is the last executing part of the interaction between robots and fruits. In this paper, the physical characteristics of tomatoes and the tomato end-effector of the fluidic elastomer actuator type were studied. There was no correlation between the test point, the mass, the size and the rupture force of tomatoes. The non-destructive clamping force of tomatoes was 11.13 N. There were statistically significant correlations between the number of finger chambers, the transverse diameter of tomatoes, the inflation pressure and the clamping force. The inflation pressure and the size of tomatoes were directly proportional to the clamping force. Since fingers with more chambers had higher flexibility, the number of chambers was inversely proportional to the slope of the horizontal force-pressure curve, and the number of chambers was directly proportional to the angle between the total clamping force and the horizontal direction. A flexible end-effector was designed by genetic algorithm according to the physical characteristics of tomatoes and the simulation results of the finger of the end-effector. The test results of the end-effector showed that the tomatoes would be successfully clamped by the end-effector composed of three four-chamber fingers in a static situation with the inflation pressure less than the optimized inflation pressure (28.293 kPa). When in a dynamic situation, the success rate of tomatoes being clamped by the end-effector with an inflation pressure of 29 kPa was 97%. The tomatoes in the static clamping test and the dynamic clamping test were not damaged. Keywords: end-effector, fluid elastomer actuator, non-destructive, flexible, Genetic Algorithm, characteristics of tomatoes DOI: 10.25165/j.ijabe.20221502.6672 Citation: Zhou K H, Xia L R, Liu J, Qian M Y, Pi J. Design of a flexible end-effector based on characteristics of tomatoes. Int J Agric & Biol Eng, 2022; 15(2): 13–24.

Design and Simulation of an End Effector for a Wheel Handling Manipulator

Background:: As the realization of the flexibility of the wheel handling manipulator, the key technical problem that needs to be overcome is the design of a flexible end effector. Objective:: The purpose of this study is to design a flexible manipulator end effector to complete the handling of wheels of different sizes on the flexible production line of wheels. Methods:: According to the size range and mass range of the wheel to be grasped, the preliminary design plan of the cylinder drive and the gripping wheel hub is determined. Afterwards, the end effector is subjected to a force analysis. The safety, stability and rationality of the design structure is tested through simulation. Results:: The simulation results indicate that the strength of the key parts of the end effector fully meets the design requirements. Strength check provides a basis for institutional optimization. Conclusion:: This paper completes the design of the end effector of the flexible manipulator. The size diversity of the wheel requires the end effector to have better flexibility. For further development, the structure of the clamping device and the force control device should be further studied. In this article, patents have been discussed.

Dynamic Response of Spatial Flexible Structures Subjected to Controllable Force Based on Cable-Driven Parallel Robots

Certain satellites with ultralong wings play a crucial role in many fields. However, external disturbance and self-rotation could result in the vibration of flexible wings, which affects the normal operation of the satellites. In severe cases, the satellites will be damaged. Therefore, the vibration of these spatial flexible structures should be suppressed. With the benefits of large workspace, low energy consumption, and small inertia, a cable-driven parallel robot (CDPR) is proposed for vibration suppression of ultralong spatial flexible structures. A controller based on the open-loop control is proposed in this article to rapidly suppress the vibration of flexible structures with quite small controllable force. To enhance the contrast, two sets of passive pretightening schemes (wire ropes and elastic strings with small elastic coefficients) are tested. In view of the small value of the cable force, the influence of friction on the experiment cannot be neglected. Therefore, a friction measurement experiment is also carried out to ensure the accuracy of the experimental data. First, the dynamic model of the CDPR, which is comprised of four cables and a flexible end-effector is established. Furthermore, controller design is detailed. The dynamic response of the scale model under output force of the control low is compared with free vibration, which validates the scheme's ability and effectiveness in vibration suppression. Finally, simulations and experiments are conducted to evaluate the control scheme, and the results are satisfactory.

Impact Force Identification of the Variable Pressure Flexible Impact End-Effector in Space Debris Active Detumbling

The security of the space environment is under serious threat due to the increase in space debris in orbit. The active removal of space debris could ensure the sustainable use of the space environment; this removal relies on detumbling technology. According to the characteristics of the mechanical impact-type active detumbling method, this paper discusses a method to accurately identify the impact force using a pressure sensor. In this work, the impact force between a flexible impact end-effector and the space debris was analyzed theoretically and experimentally considering the pressure change during impact. Firstly, a nonlinear impact force model was established for the impact between a flexible end-effector and space debris. Secondly, impact experiments were performed and the friction model was modified. Finally, the effect of detumbling was verified through simulation experiments. The results showed that the identification error of normal impact force was less than 6.7% and the identification error of tangential friction force was less than 6.9%. Therefore, this identification method of impact force met the requirements of space debris detumbling, which has important guiding significance for the active removal technology of space debris.

Generative Attention Learning: a “GenerAL” framework for high-performance multi-fingered grasping in clutter

Generative Attention Learning (GenerAL) is a framework for high-DOF multi-fingered grasping that is not only robust to dense clutter and novel objects but also effective with a variety of different parallel-jaw and multi-fingered robot hands. This framework introduces a novel attention mechanism that substantially improves the grasp success rate in clutter. Its generative nature allows the learning of full-DOF grasps with flexible end-effector positions and orientations, as well as all finger joint angles of the hand. Trained purely in simulation, this framework skillfully closes the sim-to-real gap. To close the visual sim-to-real gap, this framework uses a single depth image as input. To close the dynamics sim-to-real gap, this framework circumvents continuous motor control with a direct mapping from pixel to Cartesian space inferred from the same depth image. Finally, this framework demonstrates inter-robot generality by achieving over $$92\%$$ real-world grasp success rates in cluttered scenes with novel objects using two multi-fingered robotic hand-arm systems with different degrees of freedom.

Metal hydride actuator for a rescue jack driven by hydrogen desorption

This paper presents a metal hydride (MH) actuator rescue jack that uses hydrogen-absorbing alloy as its pressure source. The MH actuator is attached to a thin and flexible fiber-reinforced rubber bag end effector, enabling it to pry open narrow and rough gaps. The proposed MH rescue jack was prepared with different amounts of alloy (6–15 g). The results showed that, with only 6 g of alloy, the rescue jack was able to jack up a 100 kg weight to a height of 10 mm within 1 min by heating the alloy container to 50 °C. Moreover, the jack-up speed increased as the amount of alloy increased. A mathematical model was derived from the jack-up operation tests to estimate the jack-up height, with the aim of designing appropriate amounts of hydrogen-absorbing alloys for rescue jack development. According to the experimental results, the response of the jack-up height was modeled as a first order system in time domain. The model was defined as a function of alloy amount, and its validity was assessed by comparing the experimental and simulation results. The results were in good agreement which confirmed the potential of the proposed model as a design tool for jacks from the viewpoint of time constant.

Design, Prototyping and Control of a Flexible Cystoscope for Biomedical Applications

Kidney stone and prostate hyperplasia are very common urogenital diseases all over the world. To treat these diseases, one of the ESWL (Extracorporeal Shock Wave Lithotripsy), PCNL (Percutaneous Nephrolithotomy), cystoscopes or open surgery techniques can be used. Cystoscopes named devices are used for in-vivo intervention. A flexible or rigid cystoscope device is inserted into human body and operates on interested area. In this study, a flexible cystoscope prototype has been developed. The prototype is able to bend up to ±40°in X and Y axes, has a hydrodynamic cavitation probe for rounding sharp edges of kidney stone or resection of the filled prostate with hydrodynamic cavitation method and contains a waterproof medical camera to give visual feedback to the operator. The operator steers the flexible end-effector via joystick toward target region. This paper presents design, manufacturing, control and experimental setup of the tendon driven flexible cystoscope prototype. The prototype is 10 mm in outer diameter, 70 mm in flexible part only and 120 mm in total length with flexible part and rigid tube. The experimental results show that the prototype bending mechanism, control system, manufactured prototype parts and experimental setup function properly. A small piece of real kidney stone was broken in targeted area.

Kinematics Analysis of Soft Gripper System during Material Handling of Non Rigid Materials

The grippers/end effctors are used to pick and place the products in automation industries. Major challenges in this are for handling and transfer of non rigid materials like paper and fabrics. On exclusion of coils from process, a uncharacteristic type of marks surface defect are materialize perpendicular to rolling direction on both inner and outer wraps soft coils At this juncture we developed a flexible end effector for handling soft rolled products. A new approach has been introduced and an end effector designed for meet out this purpose. The Kinematic analysis have been undergone for the gripper. In kinematic analysis we used various mechanisms for the actuation of the end effector to grasp the material. Analysis of velocity, position, acceleration and force in all the nodal points been done with the modern kinematics analysis soft ware. This paper presents a systematic approach of kinematic analysis and the results revealed were compared with analytical and experimental results.

高速ビジュアルフィードバックを用いた高速ロボットハンドによるねじ回し戦略

To develop a flexible end effector for industrial assembly task, there is a demand for a high-speed, dexterous, and general robot hand. This paper focuses on the manipulation of a screw or nut, which is necessary for assembly task in cell production process, and aims to screw off and catch it with robot hand. The high-speed camera detects the location and rotation of the screw, and this information is used to plan the operation of robot hand. Experiments showed that this system can screw off the nut and catch it. It was also confirmed that visual feedback successfully works through experiments of screwing off the nuts which were differently located.

Validation of the Expert System Used for Optimum Gripping Surfaces Identification for an Injection-Molded Part

This paper describes a validation method through experimental tests of the Expert System conceived for the identification of the optimum gripping surfaces for an injection-molded part, conceived by the authors. A number of experimental tests were conducted using a flexible vacuum end-effector. During experimental tests phases three different versions have been considered for experimenting in which different types of suction cup holders and different placements on the end-effector structure were analyzed. The part subjected to tests was a stove handle. The first version of the vacuum end-effector is composed of four rigid suction cup, their placement on the gripper being made on points randomly chosen. The second version of the end-effector is composed of four flexible suction cup holders equipped with spherical articulations; the axes adjustment on the gripped surfaces being made on four randomly chosen points. The third version is composed of four suction cup holders equipped with spherical articulations, the axes positions and points placement being offered by the Expert System.

Flexible end-effector based on flexible pneumatic actuator and its grasping model.

Taking into account the disadvantages of rigid grasping end-effectors for agricultural fruits,such as low complaisance and easy to hurt the grasping object,authors designed a type of flexible end-effector,which took three pneumatic flexible bending joints as its fingers and one flexible pneumatic torsion joint as its wrist.The mathematical models for fingers and wrist of the end-effector were presented.According to the shapes of grasping objects,the end-effector’s gripping model for grasping columniform objects and holding model for grasping spheroidal objects were analyzed in detail.Simulation and experiments were conducted to study the impact of weight and radius of the grasping object to the air pressure inside the end-effector.The results showed that the mathematical models can represent the essential characteristics of the end-effector.The flexible end-effector can be applied in agricultural fruits picking task.

Thin flexible end-effector using pneumatic balloon actuator

A pneumatic balloon is applied to actuate a thin flexible end-effector. The pneumatic balloon actuator (hereafter PBA) is fabricated on a cantilever for the flexible end-effector. The end-effector bends when the pneumatic balloon swells. Static and dynamic characterizations on PBA confirm that PBA provide large displacements, high forces, and flexible structures. In order to demonstrate cooperative performance of PBA, a ciliary motion conveyance system is composed of distributed end-effectors. A manipulation of a glass plate by the developed system is successfully operated. Increasing degrees of freedom of the end-effector is also tried to perform more complicated motion. In addition, a few trials aiming to implement micro PBA arrays have been estimated through prototyping.

Robot force control with an actively damped flexible end effector

Abstract This paper proposes a new method for the hybrid force/position control of an industrial robot, which is equipped with an internal, high bandwidth velocity controller and with a compliant end effector, during constrained motion. The method combines force control with results from active control of flexible robots. The contact dynamics of the partially constrained end effector are modelled by a MIMO system. This system is decoupled into a set of six unconstrained or constrained vibrational modes, which are easy to control. The paper contains simulation results of a constrained motion.