End-effector Research Articles

Influence of pore structure on steam disinfection heat and mass transfer in Yunnan red loam

The obstacles to the continuous cropping of Chinese herbs in Yunnan have become increasingly prominent. Many soil-borne diseases can infect the roots of crops, affect the growth of crops, and eventually lead to quality and yield reduction. Soil steam disinfection can still be used as one of the first methods to solve the problem of continuous cropping obstacles of Chinese herbs such as Panax notoginseng. However, the steam will condense into a large amount of liquid water when it is cold, which will cause soil pore blockage and seriously affect the steam diffusion efficiency. Therefore, it is necessary to study the influence mechanism of the pore structure of Yunnan red loam on heat and mass transfer of steam disinfection. The experimental research was conducted on steam disinfection's heat and mass transfer patterns under different soil pore structure conditions. Image processing technology was used to collect accurate soil profiles and to establish real soil pore structure analysis. Then, fluid simulation technology was used to simulate the heat and mass transfer process and trend of steam distribution within the soil profile under different soil pore structures. The results showed that the steam heat flow of <2 mm, 2–4 mm and 4–6 mm treatments were uniformly diffused in the form of matrix flow in a 1/4 ellipse, and the effective disinfection range was 18 cm horizontal distance and 20 cm vertical distance, in which the highest temperature could reach more than 90 °C. The steam heat flow of the 6–8 mm and >8 mm treatment groups diffused irregularly in large pore steam flow. Therefore, some devices for breaking soil and rotary tillage need to finely rotate the soil in the future. The end effector's disinfection pipe spacing can refer to the effective disinfection range.

High-Order Derivatives of Serial Manipulator Jacobians Using Multidual Differentiation Transform

Abstract The use of robots is continuously growing, from heavy-duty industries to nanotechnology. Exact multilink robot end effector control is required to withstand this tendency in modern robotics. Mapping between joint variables in joint-space coordinate and end effector configuration in task-space coordinate are provided by serial manipulator kinematics. A computation of higher-order Jacobian matrix derivatives is required for accurate trajectory tracking. With conventional numerical derivation, only approximate results can be obtained. Still, the computation of high-order derivatives of multi-DoF manipulators with high accuracy requires long time intervals and it is difficult. This paper investigates a novel derivation method for a multilink robot Jacobian. According to this method, an exact value of higher-order acceleration can be obtained using a multidual differentiation transform. Multidual functions for sine and cosine will be used to get the exact value of acceleration, jerk, and hyper-jerk (jounce) expressions, commonly used for accurate trajectory-tracking.

A versatile interaction framework for robot programming based on hand gestures and poses

This paper proposes a framework for industrial and collaborative robot programming based on the integration of hand gestures and poses. The framework allows operators to control the robot via both End-Effector (EE) and joint movements and to transfer compound shapes accurately to the robot. Seventeen hand gestures, which cover the position and orientation controls of the robotic EE and other auxiliary operations, are designed according to cognitive psychology. Gestures are classified by a deep neural network, which is pre-trained for two-hand pose estimation and fine-tuned on a custom dataset, achieving a test accuracy of 99%. The index finger’s pointing direction and the hand’s orientation are extracted via 3D hand pose estimation to indicate the robotic EE’s moving direction and orientation, respectively. The number of stretched fingers is detected via two-hand pose estimation to represent decimal digits for selecting robot joints and inputting numbers. Finally, we integrate these three manners seamlessly to form a programming framework. We conducted two interaction experiments. The reaction time of the proposed hand gestures in indicating randomly given instructions is significantly less than that of other gesture sets, such as American Sign Language (ASL). The accuracy of our method in compound shape reconstruction is much better than that of hand movement trajectory-based methods, and the operating time is comparable with that of teach pendants.

Fluid–structure interaction on vibrating square prisms considering interference effects

Existing research on interference effects predominantly focuses on rigid structures. However, studies based on rigid models tend to overlook the feedback of structural motions on the flow field, thus failing to capture the intrinsic dynamics of the interference effect induced by wind-induced structural vibrations. This paper provides a comprehensive analysis of the fluid–structure interaction mechanisms considering interference effects involving two parallel square prisms, employing large-eddy simulation (LES). Various factors, including wind speed, arrangement, and vibration amplitude, are meticulously considered in the analysis. The study utilized three-dimensional LES simulations, incorporating the narrowband synthesis random flow generator method for inlet turbulence generation and adjusted through the “feedback” approach to ensure accuracy and efficiency. The research highlighted different structural arrangements exhibited distinct interference effects, and the end effect of the structure could substantially modify the flow pattern at various heights. In the tandem arrangements, the study observed several flow phenomena, including early reattachment, attenuation of the end effect, premature formation of roll structures, increased turbulence in the flow field due to vibration, resulting in wider second leading-edge separation, and a fragmented wake flow on the downstream structure. For side-by-side arrangements, the “acceleration effect” was identified and found to be further intensified by structural vibrations. The vibration of the interfering structure was noted to cause changes in vortex shedding frequencies and alterations in the wake flow pattern. In addition, vibration would enhance the interference effect but increasing amplitude and wind speed might diminish the interference effect. Overall, this study offers valuable insight into the intricate interplay of factors influencing the aerodynamics of parallel structures across diverse arrangements and under varying conditions.

Empirical modeling of profile roughness parameters during end milling of aluminium alloy 5052/tungsten carbide/graphite hybrid composite

AbstractThis study presents an empirical modeling approach to reveal the effect of end milling parameters on the profile roughness parameters. Aluminium hybrid composite was melt‐stir die cast into the required work material, setting a predetermined weight fraction of reinforcements. The experimental design was adopted using the Taguchi meta‐heuristic algorithm for the selection of the levels of the end milling parameters. The profile roughness parameters namely arithmetic average roughness (Ra), root mean square roughness (Rq), and mean roughness depth (Rz) were considered as output responses, which were measured using stylus type surface roughness tester. Non‐linear second‐order empirical models were formulated and from them, the profile response parameters were predicted with 95 % accuracy. The results revealed that the depth of cut and spindle speed are contributing 54.22 % and 38.6 % respectively among the selected input parameters on the cumulative output.

Adaptive hierarchical positioning error compensation for long-term service of industrial robots based on incremental learning with fixed-length memory window and incremental model reconstruction

Industrial robots have been extensively used in industry, however, geometric errors mainly caused by connecting rod parameter error and non-geometric errors caused by deflection and friction, etc., limit its application in high-accuracy machining. Aiming at addressing these two types of errors, parametric methods for error compensation based on the kinematic model and non-parametric methods of directly establishing the mapping relationship between the actual and target poses of the robot end-effector are investigated and proposed. Currently both types of methods are mainly offline and will be no longer applicable when the pose of the end-effector in the workspace changes dramatically or the working performance of the robot degrades. Thus, to compensate the positioning error of an industrial robot during long-term operation, this research proposes an adaptive hierarchical compensation method based on fixed-length memory window incremental learning and incremental model reconstruction. Firstly, the correlation between positioning errors and robot poses is studied, a calibration sample library is created, and thus the actively evaluating mechanism of the pose mapping model is established to overcome the problem of the robot’ workspace having a differential distribution of error levels. Then, an incremental learning algorithm with fixed-length memory window and an incremental model reconstruction algorithm are designed to optimize the pose mapping model in terms of its parameters and architecture and overcome the problem that the performance degradation of the robot exacerbates the positioning error and affects the applicability of the pose mapping model, ensuring that the pose mapping model runs stably above the target accuracy level. Finally, the proposed method is applied to the long-term compensation case of a Stäubli industrial robot and a UR robot, and compared to state-of-art methods. Verification results show the proposed method reduces the position error of the Stäubli robot from 0.85mm to 0.13mm and orientation error from 0.68° to 0.07°, as well as reduces the position error of the UR robot from 2.11mm to 0.17mm, demonstrating that the proposed method works in real world scenarios and outperforms similar methods.

Noncollocated Proprioceptive Sensing for Lightweight Flexible Robotic Manipulators

This article presents the design of a noncollocated feedback system for flexible serial manipulators. The device is a passive serial chain of encoders and lightweight links, mounted in parallel with the manipulator. This measuring arm effectively decouples the manipulator's proprioception from its actuators by providing information on the actual end effector pose, accounting for both joint and link flexibility. The kinematic redundancy of the measuring chain allows for safe operation in the context of human–robot interaction. A simple yet effective error model is introduced to assess the suitability of the proposed sensor system in the context of robotic control. The practicality of the device is first demonstrated by building a physical joint-encoder assembly and a simplified planar measuring arm prototype. With this additional feedback, a task-space position controller is devised and tested in simulation. Finally, the simulation results are validated with an experimental 3-DoF lightweight manipulator prototype equipped with a five-joint measuring arm.

Bilateral Teleoperation with a Shared Design of Master and Slave Devices for Robotic Excavators in Agricultural Applications

The main objective of this study is to develop a shared design of master and slave devices for bilateral teleoperation mechanisms used for robotic excavators in agricultural applications. In robot teleoperation research, many potential applications within controlled and hazardous environments come to light. Robots, with their capacity for remote control by human operators through master devices, often employ the master-slave teleoperation approach. This strategy finds frequent use across manufacturing, construction, and agriculture industries. The master-slave system necessitates two interdependent components that collaboratively steer the robot in real time. However, challenges arise when manipulating the robot arm proves challenging due to structural differences between the master device (such as a joystick) and the slave device (the robot arm). A stable operational framework must be established for the robot to function optimally. This teleoperation system employs a master device to govern the actions of the slave device, a dynamic that heavily influences the operational complexity. Hence, the focal point of this study is to enhance the master-slave algorithm for teleoperation applications that rely on controlling robot arm movements. Despite the differing dimensions of the master and slave devices, they both share a common structure. The kinematic model bridging these components must be intelligible to ensure user-friendliness, facilitating effortless robot control. Calculating the robot arm's end effector movement and positioning involves employing the forward kinematics of the arm, determined through Denavit-Hartenberg parameters and transformation matrices. By mitigating communication delays between the master and slave devices using a technique centered around the robot arm's end effector position, the effectiveness of teleoperation can be significantly improved. Our designed robot arm attains 80% to 100% precision across joints. In summary, streamlining the robot arm's structure and minimizing delays offers a route to bolstering both stability and efficiency in robotic movement.

Integrated L1 adaptive cartesian PD control for robotic loco-manipulation

This paper presents an integrated framework of L1 adaptive control and Cartesian PD control that overcomes the inherent limitations of the latter controller in tracking end effector position for loco-manipulation tasks. In a simplified system, this work represented the loco-manipulation problem with the Cartesian space dynamics of the end effector object, capturing the dominating parts of the dynamics in linear terms. The unmodeled nonlinear dynamics, along with other model uncertainties and external disturbances, are accounted for by the L1 adaptive controller, taking the Cartesian PD input as a component of the control law to resemble its behavior for the desired system dynamics modeled in the state predictor of the L1 adaptive controller. Through simulation results of various combinations of model perturbations and external disturbances, we show that this integrated framework can achieve similar tracking performances of the end effector and object without the need to re-tune controller parameters. This work demonstrated the mitigation of effects from system uncertainties with model perturbation of up to 100% higher than expected mass and up to 15N of sinusoidal external disturbances, with higher disturbance rejection possible through designing for more conservative estimates of unknown model parameters. Combined with the low computational cost of this framework, the improvement in state command tracking gives rise to potential implementation on robotic systems controlled with linear optimization formulations.

2D of Robotic Arm Based on Inverse Kinematics Using Arduino

Abstract: The advancements and quick developments in the technology has made it possible to create a platform for the invention of new as well as great things. One of the concept that is being used lately to improve the technology is the concept of robotics. This project focuses on the implementation of inverse kinematics for a 2-DOF (two degrees of freedom) robot arm using an Arduino microcontroller. The inverse kinematics equations are derived and programmed to calculate the joint angles required to position the robot arm's end effector in a desired location within its workspace. The Arduino board is used to interface with the robot arm's actuators and control the movement of the arm. The Arduino programming aspect of the project involves developing a control algorithm that accepts target coordinates for the end effector and computes the necessary joint angles using inverse kinematics equations. Servo motors are manipulated through the Arduino Servo library to achieve the calculated angles, enabling the arm to reach the desired positions accurately and efficiently. To enhance the functionality and safety of the 2-DOF robotic arm, the project includes features such as calibration routines, testing procedures, and safety measures to avoid collisions and servo load. The project aims to demonstrate the application of inverse kinematics in controlling robotic manipulators for precise positioning tasks

Programming 2DoF Robot Arm Based on Forward Kinematics using Arduino

This project's main goal is to use Arduino to program a 2-degree-of-freedom (2Dof) robot arm based on forward kinematics. The suggested system is made to precisely regulate the robot arm's motion for a variety of activities, such as pickand-place duties and assembly procedures. The robot arm can be precisely positioned and controlled thanks to the forward kinematics model, which determines the end effector's position based on the joint angles. The system is put into practice and put through its paces in a real-world setting, and the results demonstrate its ability to conduct precise movements with decent accuracy. The 2DoF Robot Arm can be utilized to automate complex processes and boost productivity in a variety of industries, including manufacturing, healthcare, and robotics research.

Spatial mapping of ectonucleotidase gene expression in the murine urinary bladder.

Purinergic signaling is important for normal bladder function, as it is thought to initiate the voiding reflex and modulate smooth muscle tone. The availability of adenine nucleotides and nucleosides (aka purines) at receptor sites of various cell types in the bladder wall is regulated by ectonucleotidases (ENTDs). ENTDs hydrolyze purines such as adenosine 5'-triphosphate (ATP) and adenosine 5'-diphosphate (ADP) with varying preference for the individual substrate. Therefore, the end effect of extracellular purines may depend significantly on the type of ENTD that is expressed in close proximity to the target cells. ENTDs likely have distinct cellular associations, but the specific locations of individual enzymes in the bladder wall are poorly understood. We used RNAscope™, an RNA in situ hybridization (ISH) technology, to visualize the distribution and measure the levels of gene expression of the main recognized ectonucleotidases in large high-resolution images of murine bladder sections. The relative gene expression of ENTDs was Entpd3 > Alpl >> Enpp1 = Entpd2 >> Enpp3 > Entpd1 (very low to no signal) in the urothelium, Entpd1 ≥ Entpd2 >> Enpp3 > Enpp1 = Alpl ≥ Nt5e (very low to no signal) in the lamina propria, and Entpd1 >> Nt5e = Entpd2 >> Enpp1 > Alpl = Enpp3 in the detrusor. These layer-specific differences might be important in compartmentalized regulation of purine availability and subsequent functions in the bladder wall and may explain reported asymmetries in purine availability in the bladder lumen and suburothelium/lamina propria spaces.

Higher Efficient Fruit Robot with Improved End Effectors

Under the situation that the technology level is improving recent year and the labor cost is increasing rapidly. In this paper, an autonomous harvesting robot with high efficiency is presented. The robot needs a fruit harvesting process with high obstacle avoidance efficiency for picking in complex and unstructured environments. In this research, the end-effector of the robotic arm picking process is optimized to reduce the number of times the fruit is crushed and to obtain the nearest moving trajectory to improve the picking efficiency. Therefore, the research topic of this paper is to optimize the picking method of the picking robot when performing picking operations. The following describes this paper's research methodology: first, the mechanical part of this harvesting robot is modeled, and then the most efficient way of the robot arm is found by analyzing the data of this model and combining it with the existing research. In this paper, it was found that changing the robotic arm's end-effector to a cylinder with a cutting blade would not only maximize the efficiency of the arm, but also ensure that the fruit would not be scratched. From this study, it was concluded that the end-effector can be customized to ensure efficient fruit picking according to the type of fruit and the approximate growth of the orchard fruit.

Using Lie Derivatives with Dual Quaternions for Parallel Robots

We introduce the notion of the Lie derivative in the context of dual quaternions that represent rigid motions and twists. First we define the wrench in terms of dual quaternions. Then we show how the Lie derivative helps understand how actuators affect an end effector in parallel robots, and make it explicit in the two cases case of Stewart Platforms, and cable-driven parallel robots. We also show how to use Lie derivatives with the Newton-Raphson Method to solve the forward kinematic problem for over constrained parallel actuators. Finally, we derive the equations of motion of the end effector in dual quaternion form, which include the effect of inertia from the actuators.

A novel robotic system enabling multiple bilateral upper limb rehabilitation training via an admittance controller and force field

Patients with hemiplegia are usually restricted to performing general bilateral activities of daily life (gbADLs). Bilateral training has been verified to contribute to the rehabilitation of physical functions. Although robotic systems are gradually being employed in the field of rehabilitation, few studies have performed simulations with regards to gbADLs for training. Therefore, a novel end-effector bilateral rehabilitation robotic system (EBReRS) for the upper limb is developed in this article for the task rendering of gbADLs, in which the gbADL-corresponding workspace is obtained via modularly designed bilateral parallelogram mechanisms. In addition, the interaction rendering of multiple bimanual modes (uncoupled, trans-soft-coupled, trans-semi-coupled, and rotation-coupled) is achieved by implementing the admittance model, the inner force field between robotic end-effectors, and the outer force field distributed around. Experiments of the proposed four rehabilitation training modes were carried out on the healthy subject, with the results showing a feasible method of the EBReRS in the simulation of multiple bimanual coordinated rehabilitation training tasks. In the future, the constructed EBReRS is expected to be exploited for home rehabilitation as a coordinated training device.

MODELING AN INDUSTRIAL ROBOTIC MANIPULATOR IN THE ELECTROMECHANICAL DOMAIN

In this work, a prototype of a robotic manipulator is developed and its dynamic analysis is per- formed. The system under study was analyzed in a multi-domain environment using two MATLAB tool- boxes, that is, Simscape Multibody and Simscape Electrical. By doing so, an accurate electromechanical model was constructed in this paper. Subsequently, a nonlinear controller was designed for the trajectory tracking of the end effector of the robotic manipulator. The control architecture employed in this work is a Proportional-Derivative (PD) control scheme, which is widely used in industrial applications. The nu- merical results presented in the paper demonstrate the effectiveness of the methodology followed in this investigation.

Study on Mechanical Properties of Tomatoes for the End-Effector Design of the Harvesting Robot

Agricultural robotics has emerged as a research area within robotics, with a particular focus on designing end effectors that are adapted to the physical characteristics of the target fruits. Acquiring a comprehensive understanding of the physical and mechanical properties specific to tomato fruits not only minimizes mechanical damage during grasping processes but also serves as a foundation for the optimal design of gripping components. In this study, the Syngenta Sibede variety of tomatoes was used as the experimental material. The reversible viscoelastic behavior and deformation characteristics of tomato fruits were approximated using a four-element Burgers model through creep testing. The fitting coefficients for the model exceeded 0.99. The creep parameters for the four ripening stages of tomatoes were obtained, and the correlation between the ripening stage, deformation value, and creep parameters was analyzed. Correlation analysis was performed to examine the relationships between each parameter and creep deformation, revealing significant and highly significant correlations. Inter-parameter correlations were also found to be highly significant. Puncture tests were conducted on tomatoes. The exocarp rupture force of the green-ripening stage was 9.224 ± 0.901 N, which was 53.87%, 70.63%, and 104.01% higher than that of the semi-ripening stage, early firm-ripening stage, and mid-late firm-ripening stage, respectively. This study suggests that when harvesting tomatoes at the semi-ripening stage and beyond, attention should be paid to trimming the stem. Compression experiments were conducted on tomatoes, and it was discovered that under the same ripening stage, the axial compressive rupture force of tomatoes was greater than the radial rupture force. Tomatoes exhibited anisotropic behavior. The grasping direction is axial, which can be used as the new design direction of the end-effector.

Underactuated Humanoid Peeling Approach for Pickled Mustard Tuber Based on Metamorphic Constraints.

Pickled mustard tuber (PMT), also known as Brassica juncea var. tumida, is a conical tuberous vegetable with a scaly upper part and a coarse fiber skin covering the lower part. Due to its highly distorted and complex heterogeneous fiber network structure, traditional manual labor is still used for peeling and removing fibers from pickled mustard tuber, as there is currently no effective, fully automated method or equipment available. In this study, we designed an underactuated humanoid pickled mustard tuber peeling robot based on variable configuration constraints that emulate the human "insert-clamp-tear" process via probabilistic statistical design. Based on actual pickled mustard tuber morphological cluster analysis and statistical features, we constructed three different types of pickled mustard tuber peeling tool spectral profiles and analyzed the modular mechanical properties of three different tool configurations to optimize the variable configuration constraint effect and improve the robot's end effector trajectory. Finally, an ADAMS virtual prototype model of the pickled mustard tuber peeling robot was established, and simulation analysis of the "insert-clamp-tear" process was performed based on the three pickled mustard tuber statistical classification selection. The results showed that the pickled mustard tuber peeling robot had a meat loss rate of no more than 15% for each corresponding category of pickled mustard tuber, a theoretical peeling rate of up to 15 pieces per minute, and an average residual rate of only about 2% for old fibers. Based on reasonable meat loss, the efficiency of peeling was greatly improved, which laid the theoretical foundation for fully automated pickled mustard tuber peeling.

Molecular insight into how the position of an abasic site modifies DNA duplex stability and dynamics

Local perturbations to DNA base-pairing stability from lesions and chemical modifications can alter the stability and dynamics of an entire oligonucleotide. End effects may cause the position of a disruption within a short duplex to influence duplex stability and structural dynamics, yet this aspect of nucleic acid modifications is often overlooked. We investigate how the position of an abasic site (AP site) impacts the stability and dynamics of short DNA duplexes. Using a combination of steady-state and time-resolved spectroscopy and molecular dynamics simulations, we unravel an interplay between AP-site position and nucleobase sequence that controls energetic and dynamic disruption to the duplex. The duplex is disrupted into two segments by an entropic barrier for base-pairing on each side of the AP site. The barrier induces fraying of the short segment when an AP site is near the termini. Shifting the AP site inward promotes a transition from short-segment fraying to fully encompassing the barrier into the thermodynamics of hybridization, leading to further destabilization of the duplex. Nucleobase sequence determines the length scale for this transition by tuning the barrier height and base-pair stability of the short segment, and certain sequences enable out-of-register base-pairing to minimize the barrier height.

Highly rarefied gas flows in rough channels of finite length

Highly rarefied gas flows through a rough channel of finite length with small bumps appended to its surfaces are investigated, by varying the accommodation coefficient alpha in Maxwell’s diffuse-specular boundary condition, the characteristic size and position of the bumps, and the channel length. First, we study the influence of the surface bumps and consider the rarefied gas flow in a unit channel with periodic boundary conditions to remove the end effect. It is found that the surface bumps have a significant impact on the flow permeability. When alpha is very small (i.e., nearly specular reflection of gas molecules at the channel surface), the apparent gas permeability is dramatically reduced, even in the presence of small bumps, to a value that is almost comparable to the one when fully diffuse gas-surface scattering is assumed. This impact can be taken into account through an effective accommodation coefficient, i.e., the permeability of the rough channel is taken equivalently as that of a smooth channel without bumps but having gas-surface scattering under the effective accommodation coefficient. Second, we study the end effect by connecting a smooth channel of length L_0 to two huge gas reservoirs. It is found that (i) the end correction length is large at small alpha. Consequently, the mass flow rate barely reduces with increasing L_0 rather than scales down by a factor of 1/L_0 as predicted by the classical Knudsen diffusion theory; and (ii) the end correction is related to the channel’s aspect ratio. Finally, based on the effective accommodation coefficient and end correction, we explain the exotic flow enhancement in graphene angstrom-scale channels observed by Geim’s research group (Keerthi et al, Nature 558:420–424, 2018).