Actuator Arm Research Articles

Development of Dual-Arm Human Companion Robots That Can Dance.

As gestures play an important role in human communication, there have been a number of service robots equipped with a pair of human-like arms for gesture-based human-robot interactions. However, the arms of most human companion robots are limited to slow and simple gestures due to the low maximum velocity of the arm actuators. In this work, we present the JF-2 robot, a mobile home service robot equipped with a pair of torque-controlled anthropomorphic arms. Thanks to the low inertia design of the arm, responsive Quasi-Direct Drive (QDD) actuators, and active compliant control of the joints, the robot can replicate fast human dance motions while being safe in the environment. In addition to the JF-2 robot, we also present the JF-mini robot, a scaled-down, low-cost version of the JF-2 robot mainly targeted for commercial use at kindergarten and childcare facilities. The suggested system is validated by performing three experiments, a safety test, teaching children how to dance along to the music, and bringing a requested item to a human subject.

Design and fabrication of bioinspired pattern driven magnetic actuators

Additive manufacturing (AM) has drawn significant attention in the fabrication of soft actuators due to its unique capability of printing geometrically complex parts. This research presents the design and development of an AM process for bioinspired, deformable, and magnetic stimuli-responsive actuator arms. The actuator arms were fabricated via the material extrusion-based AM process with magnetic particle-polymer composite filaments. Inspired by the rhombus cellular structure found in nature, different design parameters, such as the line width of the interior rhombus sides, and 3D printing parameters were studied and optimized to fabricate actuator arms that exhibit enhanced flexibility while being magnetically actuated. The trigger distance and deformation experiments revealed that the width of the rhomboids’ sides played a critical role in magnetic and bending properties. It was found that the sample with a line width of 550 µm and printing layer thickness of 0.05 mm had the maximum deflection with a measured bending angle of 34 degrees. The magnetic property measurement exhibited that the sample with a line width of 550 µm showed the maximum magnetic flux density of 3.2 mT. The trigger distance results also supported this result. A maximum trigger distance of 8.25 mm was measured for the arm with a line width of 550 µm. Additionally, tensile tests showed that the sample exhibited a 17.7 MPa tensile strength, 1.8 GPa elastic modulus, and 1.3% elongation. Based on these results, we successfully fabricated a 3D printed magnetic gripper with two rhombus cellular structured arms which showed grasping and extensive load lifting capability (up to ∼140 times its weight).

Measuring diameters and velocities of artificial raindrops with a neuromorphic event camera

Abstract. Hydrometers that measure size and velocity distributions of precipitation are needed for research and corrections of rainfall estimates from weather radars and microwave links. Existing optical disdrometers measure droplet size distributions, but underestimate small raindrops and are impractical for widespread always-on IoT deployment. We study the feasibility of measuring droplet size and velocity using a neuromorphic event camera. These dynamic vision sensors asynchronously output a sparse stream of pixel brightness changes. Droplets falling through the plane of focus of a steeply down-looking camera create events generated by the motion of the droplet across the field of view. Droplet size and speed are inferred from the hourglass-shaped stream of events. Using an improved hard disk arm actuator to reliably generate artificial raindrops with a range of small sizes, our experiments show maximum errors of 7 % (mean absolute percentage error) for droplet sizes from 0.3 to 2.5 mm and speeds from 1.3 to 8.0 m s−1. Measurements with the same setup from a commercial PARSIVEL disdrometer show similar results. Both devices slightly overestimate the small droplet volume with a volume overestimation of 25 % from the event camera measurements and 50 % from the PARSIVEL instrument. Each droplet requires processing of 5000 to 50 000 brightness change events, potentially enabling low-power always-on disdrometers that consume power proportional to the rainfall rate. Data and code are available at the paper website https://sites.google.com/view/dvs-disdrometer/home (Micev et al., 2023).

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

A novel bioreactor platform to apply dynamic load to neonatal lamb living myocardial slices for the study of the regenerative properties of the heart

Abstract Background The inability of the myocardium to regenerate is a determining factor in heart failure (HF).Platforms that model cardiac disease require to approximate the in vivo environment and related factors.One such factor is mechanical load, and in vitro, application of this has been by static, isometric systems that mimic preload only.Application of both preload and afterload, however, better recapitulates the cardiac cycle.Mechanical load is relevant in neonatal tissue, where the perinatal period sees changes to the haemodynamics, and a loss to the CM's regenerative capacity.MyoLoop is a novel bioreactor that can apply dynamic loading conditions upon living myocardial slices (LMS) by using a 3-element Windkessel model, producing dynamically changing afterload, simulating pressure-volume (P/V) loops.Here we apply physiologically relevant pre- and afterload to neonatal lamb tissue and establish an in vitro method studying the effects of changing load on the regenerative properties of the heart. Hypothesis The aim of this study is to investigate the feasibility of the MyoLoop system to modulate contractility in neonatal LMS, in comparison to LMS under isometric preload. Methods 300 µm-thick LMS were obtained from the left ventricle of neonatal lambs (12-17hrs after birth). Mechanical load was applied isometrically by stretching LMS by 117.5% of their slack length, to recapitulate physiological preload. To reproduce dynamic afterload, LMS were placed in the MyoLoop and stretched at physiological preload (117.5%) but exposed to a dynamic physiological afterload, achieved by shortening of a linear actuator arm attached to the LMS. After 48 hours culture, maximum force produced by the slices under static preload was assessed using a force transducer and compared to the force production and P/V loop measurements recorded from the MyoLoop. Results Isometrically loaded slices at 0hrs demonstrated large force amplitude of 41±5.7mN/mm2(mean± SEM, n=6),compared to a lower range of force at 24 hrs(10.9±5.07mN/mm2; mean±SEM, n=5) and even weaker forces at 48hrs(2.42±0.84mN/mm2; n=8).There was a gradual decrease in time-to-peak (TTP) after 48hrs,from 264±0.01ms (mean±SEM, n=6) to 240±0.03ms (mean±SEM, n=8),with an shortening also seen in the relaxation parameters TT50% and TT90%. In contrast, LMS cultured in MyoLoop demonstrated an increase in force amplitude of 25.2% from 0-48hrs,and an increase in TTP and TT50% and TT90% decay(n=2).Additionally, LMS cultured within the MyoLoop system demonstrated viability at 72hrs, producing P/V loops and maintaining contractility at 12.6% above 0 hrs contraction. Conclusions The dynamic loading of neonatal LMS through the MyoLoop maintained LMS contractility over 48hrs, compared with isometrically loaded LMS. This highlights the importance of modelling both physiological pre-and afterload in vitro. Further work will elucidate the effects of changing dynamic mechanical load on the regenerative properties of the neonatal heart.

An intelligent fuzzy-particle swarm optimization supervisory-based control of robot manipulator for industrial welding applications

The propensity of manufacturers to produce goods at affordable cost, with more accuracy, and at a faster rate force them to search for novel solutions, such as deploying robots in place of people in a sector that can accommodate their needs. Welding is one of the most crucial processes in the automotive industry. This process is time-consuming, subject to error, and demands skilled professionals. The robotic application can improve this area of production and quality. Other industries, such as painting and material handling, can also profit from the use of robots. This work describes the fuzzy DC linear servo controller, which functions as a robotic arm actuator. Robots have been widely employed in most productive sectors in recent years, including assembly plates, welding, tasks at higher temperatures, etc. Controlling a robot accurately is a difficult undertaking as a robot is very nonlinear with many joints that are often organized and unstructured. To carry out the effective task, an effective PID control based on fuzzy logic has been employed together with the method of Particle Swarm Optimization (PSO) approach for the estimate of the parameter. This offline technique determines the lowest number of optimal robotic arm control parameters. To verify the controller design with computer simulation, a comparative assessment of controllers is given by means of a fuzzy surveillance controller with PSO which improves the parameter gain to provide a rapid climb, a smaller overflow, no steady condition error signal, and effective torque control of the robot arm.

In-Situ Measurement of Multi-Axis Torques Applied by Wearable Soft Robots for Shoulder Assistance

While a number of wearable soft robotic devices have been proposed to assist the shoulder, limited efforts have been made to quantify the amount of torque they apply to the body. Most work to-date has assessed soft actuator performance with simple benchtop experiments that may not be representative of the boundary conditions on the human body. We propose a new methodology to measure torques directly in-situ on the body and then use this technique to make a detailed comparison of two versions of a soft wearable shoulder assistance robot. The impact of a number of factors are considered, such as actuator design, garment anchoring, material hysteresis, arm pose, and inflation pressure. Many of these factors are not present on the benchtop and are found to significantly affect torque production. We compare results obtained on a simple benchtop test fixture with two on-body settings: an idealized mannequin and actual human subjects. The mannequin and human results were similar, but differed significantly from the benchtop, further motivating the need for on-body testing. Moving forward, we believe that the ability to directly quantify device performance in-situ will be critical to develop new design, modeling, and control strategies for wearable robots.

An open-source LED array illumination system for automated multiwell plate cell culture photodynamic therapy experiments

Photodynamic therapy (PDT) research would benefit from an automated, low-cost, and easy-to-use cell culture light treatment setup capable of illuminating multiple well replicates within standard multiwell plate formats. We present an LED-array suitable for performing high-throughput cell culture PDT experiments. The setup features a water-cooling loop to keep the LED-array temperature nearly constant, thus stabilizing the output power and spectrum. The setup also features two custom-made actuator arms, in combination with a pulse-width-modulation (PWM) technique, to achieve programmable and automatic light exposures for PDT. The setup operates at ~ 690 nm (676–702 nm, spectral output full-width half-maximum) and the array module can be readily adapted to other LED wavelengths. This system provides an illumination field with adjustable irradiance up to 400 mW/cm2 with relatively high spectral and power stability comparing with previously reported LED-based setups. The light doses provided by the LED array were validated with comparison to traditional laser PDT. This open-source illumination platform (including the detailed technical description, fabrication protocols, and parts list provided here) helps to make custom light sources more accessible and of practical use for photomedicine research.

A novel servo-stabilized electromagnetic levitation formicro-EDM processing and its feasibility analysis

The purpose of this paper is to evaluate the feasibility of a novel gap-controlled strategy for micro-EDM process using magnetic levitation. The tool is levitated and positioned accurately using a unique actuator arm. The actuator arm attained the required positioning accuracy in the thrust (Z) direction to ensure a uniform and smooth discharge free of arcing and short circuits. Experiments were carried out using a copper tool and EDM oil on Nimonic superalloy (Grade C-263). Material removal rate (79.26 µg/min), tool wear rate (19.75 µg/min), and average surface roughness (Ra = 1.196 µm) all proved the efficacy of the developed technology. Furthermore, the machining stability and average specific energy (1.7350 J/μg) were examined and compared to the experimental results of traditional EDM, as well as literature data. Maglev μ-EDM is substantially more stable than traditional EDM, according to a comparison of the current-voltage (V-I) curve. Microholes, micropores, recast layer, and other surface topographical features are detected in a low amount using FESEM. The bidirectional material movement and elemental diffusion are shown by elemental characterization using EDX analysis.

Calculation of the force and kinematic parameters of the transfer mechanism based on a twisted arm chain

Introduction. The paper presents a brief kinematic analysis, as well as the application of D'Alembert's principle to finding the relationship between the force parameters in the transmission mechanism of a robotic manipulator constructed from a twisted arm chain. The use of this transfer mechanism can enhance the life of the arm actuator, the accuracy of its positioning, and increase the workload compared to the flexible linkage actuators (twisted strings). The work aimed at obtaining dependences between the displacements of circuit elements, as well as their force parameters required to monitor the control system operation of these devices.Materials and Methods. In the course of solving the problem, an elementary segment (element) of the transmission chain was considered. To find the relationship between the loads in the element, the virtual displacement principle was used. When finding kinematic connections between displacements, a brief geometric analysis of the transmission chain element was carried out. To conduct a comparative analysis of the analytical dependences obtained, a simulation technique implemented on a graphical link model using the NX software package was applied.Results. In the course of the study, we obtained dependences for determining the magnitude of the moment developed on the input link, depending on the external workload and its rotation angle, as well as for defining the linear displacement of the output link. A simulation model of the actuator was constructed, which can be applied in the dynamic study of the actuator mechanism, taking into account the inertia of the links.Discussion and Conclusions. From the obtained analytical dependences, we determined the value of the angle of rotation of the input link of the mechanism element, at which the maximum torque value for a fixed workload on the output element was achieved, as well as the maximum linear displacement of the output link. The calculated values were in good agreement with similar values obtained from the results of the simulation experiment, which gave us the possibility of using analytical dependences in the formation of a robot control system. In addition, these dependences made it possible to provide the selection of actuators with the required force indicators.

An Efficient Design Procedure for MEMS Electrothermal Microgripper

Abstract With the development of miniaturization technology, micro-electromechanical system (MEMS) electrothermal microgrippers have been widely used owing to their compact size, ease of manufacturing, and low production cost. Since most of these systems are governed by partial differential equations (PDEs), modeling of microgrippers poses a significant challenge for designers. To reduce the overall computational complexity, it is a common practice to model the microgripper system using the finite element method (FEM). During the design process, the geometric and analytical properties of the microgripper influence the system dynamics to a great extent, and this work focuses on studying the effects of such parameter changes. In low-voltage applications, the performance of the microgripper is influenced by the geometrical variations, and the air gap. Hence, for the modeling of the microgripper, actuator arm lengths, and the gap between the arms are chosen as the two main geometric design parameters, while the input current density is considered as the analytical design parameter. In this work, the optimized design parameter values for maximum possible displacement are obtained with the use of sine cosine algorithm (SCA). Furthermore, an averaging operation is proposed for efficiently designing the MEMS electrothermal microgripper, and the efficacy of the proposed design methodology is demonstrated through simulation studies.

Higher order sliding mode based lateral guidance and control of finless airship

This paper addresses a non-unified super twisting sliding mode based guidance and control framework for the lateral path following of finless airship. Two loops strategy: outer guidance and inner control, is opted here. A nonlinear sliding surface based guidance law is designed that generates reference heading angle commands for the inner loop. The inner control loop that generates commands for propulsion arm actuators is designed using linear sliding mode control theory. Stability of the closed-loop control system is shown by employing the Lyapunov theory. The performance and robustness of the proposed framework is validated through nonlinear high fidelity simulation platform with actuators dynamics, sensor models including measurement noises, and external disturbances like wind/gust. The proposed framework is benchmarked against classical methods in the literature.

Wrist-driven passive grasping: interaction-based trajectory adaption with a compliant anthropomorphic hand

The structure of the human musculo-skeletal systems shows complex passive dynamic properties, critical for adaptive grasping and motions. Through wrist and arm actuation, these passive dynamic properties can be exploited to achieve nuanced and diverse environment interactions. We have developed a passive anthropomorphic robot hand that shows complex passive dynamics. We require arm/wrist control with the ability to exploit these. Due to the soft hand structures and high degrees of freedom during passive-object interactions, bespoke generation of wrist trajectories is challenging. We propose a new approach, which takes existing wrist trajectories and adapts them to changes in the environment, through analysis and classification of the interactions. By analysing the interactions between the passive hand and object, the required wrist motions to achieve them can be mapped back to control of the hand. This allows the creation of trajectories which are parameterized by object size or task. This approach shows up to 86% improvement in grasping success rate with a passive hand for object size changes up to ±50%.

Six Sigma Implementation in Production Process in Electronic Company Malaysia

The electronics industry is one of the growing industrial sectors because of the need for electronics industry products continuously increases. This situation of development is driving the fast pace of electronics industry companies in Malaysia to be better prepared to face competition in the era of free trade. The study was carried in an electronic company in Malaysia that produce hard disk components. In this company, the number of defective products is very high which is the average defect (they call it u-loss) in the brushing room for arm body actuator products reaches 0.454% and one type of actuator arm body has reached 0.982% of defect units which means the company loses 65,000.88 RM per year. This study only focused on actuator arm body production in brushing room and aim to determine the dominant product which have the biggest percentage of defect, determine types of defects in the production of selected product, determine the root cause of the biggest defects in the production of selected product in brushing area, and recommend improvements in order to minimize the occurrence of defects in the production of selected product. This research uses Six Sigma in solving problems in the company. This study did not evaluate the results of the Six Sigma implementation directly. Therefore, as an alternative, quality improvement is done through Monte Carlo simulation with several scenarios. If zero defect in actuator arm body production is reached, company can save 65,000.88 RM per year.

Failure analysis of inlet guide vane (IGV) actuator and bellcrank assembly used on J85 turbojet engines

This study presents the metallurgical analysis results of fracture failure occurred on the arm of Inlet Guide Vane (IGV) actuator and bellcrank assembly that used on J85-GE-5 turbojet engine. The broken arm material is determined to be AMS4134 Aluminum Alloy Forging. Material composition of Aluminum alloy consists of 93.35%-Al, 4.5%-Cu, 0.85%-Si, 0.8%-Mn and 0.5%-Mg. The average hardness value of the material is measured to be 75 HRB. The metallurgical analysis results indicate that the corrosion assisted fatigue under the influence of repeated loading and corrosion started the micro fractures and cracks on the IGV actuator and bellcrank assembly arm surface, then residual cross-section surface were completely sheared off because the residual cross-section surface did not endure the over load effects overcoming on it. The fatigue area of the arm covers approximately 1/3 of the total cross-sectional area.

Performance enhancement of hybrid hydraulic excavator using multiple hydro-pneumatic accumulators

In this article, the heavy earth moving machinery like hydraulic excavator used in the construction and mining industries has been taken into consideration. Most of the heavy earth moving machineries used in these industries are mobile with engine as the main source of power. The work deals with two different hydraulic circuits: first the proposed one and second the conventional one, and both are studied at laboratory scale, which resembles the circuit of the hydraulic excavator. In the hydraulic circuit, out of the three hydraulic linear actuators, two are connected with hydro-pneumatic accumulators and one hydro-motor is also taken into consideration, which resembles the boom, arm, bucket and swing motor, respectively. The idea behind the proposed circuit is to store substantial potential energy during downward movement of the two linear actuators in the accumulators, which resembles the boom and arm cylinder of the excavator. The stored energy is used for upward motion of the two actuators without utilizing any energy from the main pump. For the devised strategy, MATLAB/Simulink environment has been utilized for developing the simulation model and the same has been validated with the experimental data with reasonable accuracy. The effect of accumulator volume and pre-charge pressure has been studied for optimization of the accumulator size on the validated simulation model. This concept helps in saving 14.06% energy than its conventional counterpart which does not have the energy storage elements. The linear position control of the boom and the arm actuator in the proposed circuit have been accomplished using proportional–integral–derivative control and pressure-compensated proportional flow control valve and have been achieved with reasonably accuracy.

Geometric Gait Design for a Starfish‐Inspired Robot Using a Planar Discrete Elastic Rod Model

A starfish‐inspired robotic platform consisting of multiple soft fluidic bending actuator arms arranged with radial symmetry about a rigid hub is described. Intrinsic properties of the soft actuators are estimated via computer vision for varying input fluid pressures. The dynamic motion of individual arms and the full robot are modeled using the planar discrete elastic rod (PDER) theory. Locomotion gaits (periodic shape changes) that result in translation in the plane, separately considering fixed or rotating anchors at the end of each arm, are derived. Gait efficiency is defined as the displacement magnitude divided by a measure of the input control effort over each gait cycle, including a cost for anchor attachment. Through numerical computation, optimally efficient gaits are found and the desired motion with a pneumatic hardware prototype is demonstrated.

Flying watch: an attachable strength enhancement device for long-reach robotic arms

A long-reach robotic arm is useful for applications such as nuclear plant decommissioning, inspection, and firefighting. However, for such arms, a small external reaction force can result in large loads on proximal arm actuators because of long moment arms. This problem was previously solved by specialized arm designs that compensate external reaction forces. However, these arm designs are hard to be applied to other arms or customized to different missions. To overcome these difficulties, in this paper, we propose a modular thrust generating concept inspired by wristwatch designs, called flying watch, which can be attached to a robotic arm with mission-dependent attachment styles (attachment positions and orientations) and cooperate with actuators to enhance arm strength. We first introduce flying watch concept, design, and dynamics. Then we propose two levels of watch-actuator cooperation in quasistatic situations by introducing a problem called Watch Actuator Cooperation for Arm Enhancement (WACAE) and providing an example solution. The first level of cooperation is only watches adapt their thrusts to minimize actuator loads, which is generally applicable to varieties of arms. The second level cooperation is that not only do the watches adapt their thrusts but also the actuators cooperatively position the watches to optimal positions and orientations to counteract external reaction forces, which is suitable for redundant arms and can counteract external reaction forces more effectively. Finally, we present simulations to verify that flying watches can significantly reduce actuator loads using both levels of watch-actuator cooperation (the first level by 36.9% and the second level by 43.7%).

Motion of robot arm using bi-articular muscle hydraulic actuator

Humans have bi-articular muscles acting on two joints, and bi-articular muscles play a very important role in human action. For those reasons, the robot arms having a drive system based on the function of bi-articular muscles have been developed. In these robot, DOF for the control is lower than the DOF for the mechanism. Therefore, since that system depends on some kind of external force, it is necessary to know the characteristics for design the control. This study reports the mechanical characteristics of bi-articular muscle hydraulic actuator and robot arm using it. The hydraulic actuator consists of parallel connected master and slave cylinder. The slave cylinder is a differential mechanism with 3 ports. We examined the function as a bi-articular muscles actuator and confirmed the motion of the robot arm which depends on external force in the experiment.

Considerations for temperature sensor placement on rotary-wing unmanned aircraft systems

Abstract. Integrating sensors with a rotary-wing unmanned aircraft system (rwUAS) can introduce several sources of biases and uncertainties if not properly accounted for. To maximize the potential for rwUAS to provide reliable observations, it is imperative to have an understanding of their strengths and limitations under varying environmental conditions. This study focuses on the quality of measurements relative to sensor locations on board rwUAS. Typically, thermistors require aspiration and proper siting free of heat sources to make representative measurements of the atmosphere. In an effort to characterize ideal locations for sensor placement, a series of experiments were conducted in the homogeneous environment of an indoor chamber with a pedestal-mounted rwUAS. A suite of thermistors along with a wind probe were mounted inside of a solar shield, which was affixed to a linear actuator arm. The actuator arm was configured such that the sensors within the solar shield would travel underneath the platform into and out of the propeller wash. The actuator arm was displaced horizontally underneath the platform while the motors were throttled to 50 %, yielding a time series of temperature and wind speed that could be compared to temperatures being collected in the ambient environment. Results indicate that temperatures may be biased in the order of 0.5–1.0 ∘C and vary appreciably without aspiration, sensors placed close to the tips of the rotors may experience biases due to frictional and compressional heating as a result of turbulent fluctuations, and sensors in proximity to motors may experience biases approaching 1 ∘C. From these trials, it has been determined that sensor placement underneath a propeller on an rwUAS a distance of one quarter the length of the propeller from the tip is most likely to be minimally impacted from influences of turbulence and motor, compressional, and frictional heating while still maintaining adequate airflow. When opting to use rotor wash as a means for sensor aspiration, the user must be cognizant of these potential sources of platform-induced heating when determining sensor location.