Design of a Light-Weight, Low-Cost Three-Finger End Effector

HighlightsA critical torque of 0.257 N-m is required to detach 95% of apples, when the preferred twist picking mode is used.New silicone-based end effectors performed much better than the original, non-conformable end effector.The straight end effector had the best overall picking performance with 87% picking success rate.The new vacuum-based harvesting robot looks promising for automated harvesting of apples.Abstract. The end effector plays a critical role in fruit picking by a robotic fruit harvesting system. A newly developed vacuum-based robotic apple harvesting system, using the twist-and-pull fruit picking method, has shown promise in picking fruit from clusters and navigating through the tree canopies. The robot’s original thin foam end effector failed to achieve acceptable picking performance because it was unable to conform to fruit of different sizes and thus could not generate sufficient suction forces needed to detach fruit. This research was therefore aimed at developing new end effectors to greatly enhance the robot’s fruit picking performance. Field manual pulling and twisting experiments for three varieties of apples were conducted, and the critical pulling or suction force and twisting torque needed to detach 95% of apples were determined to be 28.3 N and 0.257 N-m (equivalent to a pulling force of 21.0 N for the current robot’s configuration), respectively. Three new silicone-based end effectors of different geometries (denoted as “Straight”, “Bellow” and “Curved”) were designed and fabricated, and they were evaluated in lab and field experiments. Results showed that the three new end effectors performed significantly better than the original, unconformable end effector based on multiple performance metrics, including vacuum pressure, overall picking success rate, picking rate by the rotation mechanism, and fruit attachment orientation. The “Straight” end effector performed consistently better than the other two new end effectors; it had 87% overall picking success rate, 65% success rate by the rotation mechanism alone, and 89% success rate when the middle section or cheek of fruit attached to the end effector. With further improvements, the “Straight” end effector should meet the apple picking performance requirement for the new vacuum-based robotic harvesting system. Keywords: Apple, End Effector, Fruit, Harvest, Robotics, Vacuum.

A new resonant technique for accurate and reliable rneasurement of end and gap effects in microstripline has been developed. An investigation of the frequency dependence of end and gap effects in microstrip was performed. There is no apparent frequency variation for the end effects for w/h =0.5, 1.0, and 2.0 lines on alumina substrate (epsilon'/sub r/ /spl equiv/ 9.8), between 7.0 and 18.0 GHz. A small dependence on resonator mode number of these effects has been observed.

Formulas are derived for calculating the steady state saturation profile and pressure profile resulting from the end effect. A numerical integration is required to obtain the results. Two dimensionless numbers containing various parameters of the system are introduced, which, along with the viscosity ratio and the fractional flow of one component, characterize the system. It is suggested that the magnitude of the end effect can be estimated just knowing these numbers. Sample calculations are carried out showing the influence of the various parameters on the end effect. A discussion is given to show that in the measurement of relative permeability curves by the dynamic method, the end effect has a large influence on the preferentially nonwetting phase relative permeability curve if the pressure drop is measured in the wetting phase. If the pressure drop is measured in the nonwetting phase, the largest error appears in the wetting phase curve. If the pressures are measured in both phases, the errors tend to be self-correcting for each relative permeability curve. End effects were measured experimentally on a Boise core for water-oil and gas-oil systems. Three different rates were used in each series. There was satisfactory agreement between the theory and experimental results. Introduction The so-called capillary end effect or the holdup of the preferentially wetting phase at the outlet of a porous medium during the simultaneous flow of two or more fluids has received considerable attention from time to time in the oil industry. In particular, there has been interest in how much influence the end effect has on the production from oil reservoirs and how much laboratory measurements of relative permeability are dependent on the end effect. Even though there has been quite a bit of qualitative discussion of these matters, there has been very little quantitative theoretical or laboratory work performed. The present investigation gives a fairly complete theoretical treatment of the capillary end effect within the bounds of Darcy's law and the capillary pressure relation. Experimental results on end effects are also presented for water-oil and gas-oil systems. The end effect comes about at the efflux face of a core or around the wellbore in a reservoir because of the discontinuity in capillary pressure when the flowing fluids leave the porous medium and abruptly enter a region where there is no capillary pressure.

Low-pass filter without the end effect for estimating transmission characteristics—Simultaneous attaining of the end effect problem and guarantee of the transmission characteristics

Accurate estimation of rock strength is one of the most important tasks in rock engineering design. We analyzed the mechanical and failure properties of rock specimens affected by the end and shape effects under uniaxial compression through experimental and numerical studies. It was found that the end effect could change the failure mode of rock specimens from splitting failure to shear failure, as the coefficient of friction at the rock specimen-loading platens contacts increased. When the coefficient of friction was increasing, the contour distribution of the equivalent plastic strain of specimen also changed, which simultaneously influenced by the shape of specimen. It can be observed that an increase in the slenderness of specimen caused a decrease in end frictional effect on the uniaxial compressive strength of rock specimen. The numerical results also revealed that the shape effect originated from the end frictional effect as the rock material was homogeneous. The relationship between the uniaxial compressive strength and the aspect ratio of specimen was obtained and fitted by incorporating the end effect, which indicated that the uniaxial compression test should mitigate the coefficient of friction and increase the aspect ratio of specimens to make the observed strength of specimen more meaningful.

Robotic end effectors are needed for a variety of terrestrial and space-based tasks. End effectors are commonly inspired by the human hand, with a range of complexity, including varying number of fingers, joints and degrees of freedom. Hand and pincher-type grippers can require complicated actuation and/or a significant sensing and control system to ensure proper orientation of the gripper about the target prior to gripping as well as to avoid crushing the target. Universal grippers, most notably exemplified by the universal Jamming Gripper (Brown et al 2010 Proceedings of the National Academy of Science 107, 18809–18814), provide an alternative design that aims to simplify the actuation, sensing and control of robotic fixturing end-effectors. The universal Jamming Gripper is actuated pneumatically, by applying vacuum to granular media, thereby causing the grains to jam, when confined by an external bladder. We present the design and performance of a universal gripper that is actuated by applying a magnetic field, thereby eliminating the need to supply vacuum (and a reinflation source) to actuate the gripper. The magnetic field actuates a magnetorheological fluid composed of a bi-disperse mixture of carbonyl iron grains suspended in a silicone oil. The performance of this novel gripper design is characterized for a range of target sizes and shapes, and gripper design characteristics.

This paper proposes a control strategy for using a 2-Degree-of-Freedom (DOF) parallel robot as a camera stabilizer. To configure the stabilizer, a gyro sensor is mounted on the end-effector of the robot and the data is transmitted to a PC in order to permanently command two servo motors to the end of compensating the external disturbances. A novel adaptive approach is utilized to stabilize the end-effector of the 2-DOF Spherical Parallel Robot under study, where an adaptive parameter should be adjusted in order to damp disturbances, exponentially. To assess the method, first in SimMechanics, operation of the 2-DOF robot with the adaptive approach is simulated and examined. In addition, a well-known and robust decay algorithm is employed to show the superiority of the proposed method. Then, by implementing on the real structure, the performance of the adaptive controller is validated. The proposed method leads to better performance in compare with the decay algorithm, from view point of quantitative indices of tracking, stabilization and smoothness.

Composite robot end effector for manipulating large LCD glass panels

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.

The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips. Thus, accounting for axially varying burnup in criticality analyses is also referred to as accounting for the ''end effect'' reactivity. The magnitude of the reactivity change due to ''end effect'' is dependent on the initial assembly enrichment, the assembly average burnup, and the particular axial profile characterizing the burnup distribution. The set of bounding axial profiles should incorporate multiple BWR core designs and provide statistical confidence (95 percent confidence that 95 percent of the population is bound by the profile) that end nodes are conservatively represented. The profiles should also conserve the overall burnup of the fuel assembly. More background on BWR axial profiles is provided in Attachment I.

Transforming pneumococcal DNA is inactivated by treatment with restriction enzymes. For mutations belonging to the same locus (amiA locus), the extent of inactivation depends strongly upon the mutations and the enzymes. Two EcoRI and one BamHI restriction sites have been located within the amiA locus. After treatment of donor DNA with either one of these enzymes, the lowest transforming activity is observed for mutations that map near restriction sites. This effect of proximity to the nearest end of the DNA fragment extends over a distance of 1,400 nucleotides. The curve of transforming activity versus DNA size obtained with endonuclease-generated DNA fragments is very similar to that obtained previously with mechanically sheared DNA. Both curves show a striking slope change for donor DNA size around 2,700 base pairs, i.e. twice the length found for the extent of the 'end effect'. We suggest that for donor DNA fragments larger than 2,700 base pairs the transforming activity depends mainly upon the size of donor whereas for donor DNA fragments shorter than 2,700 base pairs both a size-dependent phenomenon and the 'end effect' contribute to reduce drastically the transforming activity.

This paper is concerned with the investigation of the effect of material inhomogeneity on the decay of Saint–Venant end effects in functionally graded linear piezoelectric materials. Saint–Venant's principle and related results for elasticity theory have received considerable attention in the literature but it is only recently that analogous issues in piezoelectricity have been investigated. The current rapidly developing smart–structures technology provides motivation for the investigation of such problems. We examine the decay of Saint–Venant end effects in the context of anti–plane shear deformations for linear inhomogeneous piezoelectric solids. For a rather general class of anisotropic piezoelectric materials, the governing partial differential equations (PDEs) of equilibrium are shown to be a coupled system of second–order PDEs with variable coefficients for the mechanical displacement u and electric potential φ . The traction boundary–value problem with prescribed surface charge is formulated as an oblique derivative boundary–value problem for this elliptic system. The axial decay of solutions on a semi–infinite strip subjected to non–zero boundary conditions only at the near end is investigated. This analysis is carried out for a subclass of special graded materials, namely, laterally inhomogeneous solids. Two specific piezoceramics that have received widespread application are considered. For the first (corresponding to the hexagonal 6 mm crystal–symmetry class), it is shown that the mechanical and electrical problems essentially decouple, and that the decay rates for mechanical and electrical Saint–Venant end effects coincide and are equal to that of linear inhomogeneous isotropic anti–plane elasticity, for which results on the decay rate have been obtained previously. For the second class of materials (corresponding to the cubic 4∼3m symmetry) the situation is quite different. The boundary–value problem involves a full coupling of mechanical and electrical effects. Energy decay estimates using differential–inequality methods are used to obtain an explicit estimated decay rate (a lower bound for the actual decay rate) in terms of a single dimensionless piezoelectric coupling constant d and the decay rate for an associated linear inhomogeneous isotropic anti–plane shear elasticity problem. For fixed material inhomogeneity, the decay rate is shown to be monotone decreasing with increasing values of d In the limit as d→0 we recover the purely mechanical case. Thus, for this class of functionally graded materials, piezoelectric end effects are predicted to penetrate further into the strip than their functionally graded isotropic elastic counterparts , confirming recent results obtained in other contexts in linear piezoelectricity. For both classes of materials, the influence of material inhomogeneity on the decay rate is reflected solely by the shear modulus of an associated inhomogeneous isotropic anti–plane shear elasticity problem. It is shown that, for both material classes, material inhomogeneity has a significant influence on the decay of end effects.

During tissue retraction with a laparoscopic grasper, tissue-damaging pressures can occur. Past research suggests that peak pressures can be considerably reduced by rounding the edges or covering the tip of the end effector with a silicon sleeve. To identify grasping methods that limit tissue damage, the effects of (a) Young's modulus of the end effector, (b) curvature of the end effector, and (c) angle with which the tissue is pulled relative to the plane of the end effector, on the pressure generated on the tissue were investigated. Artificial skin was placed between two non-serrated jaws, a pressure-sensitive film was interposed between the skin and upper jaw, and the end effector was loaded with 13 N. End effectors with Young's moduli of 0.09, 0.67, 1.49 MPa, and 69 GPa, and with non-rounded and 5 mm rounded edges were tested under pulling angles of 25°, 50°, and 75°. For non-rounded end effectors, the maximum pressure and the area across which pressure exceeded the safety threshold for tissue damage increased with Young's modulus and pulling angle. For rounded end effectors, maximum pressure did not increase monotonically with Young's modulus. Instead, the end effector with the second lowest Young's modulus yielded significantly lower maximum pressure than the end effector with the lowest Young's modulus. For rounded end effectors, pressures were below the safety threshold for all Young's moduli. This indicates that to prevent tissue damage, soft graspers may not be needed; rounding the edges of metal graspers could suffice for preventing tissue damage.

—Robotic operations of surgical instruments have greatly improved the workability of surgical operations. Even though they have high abilities, robotic surgery systems demand high cost and a large room space. As a solution to those problems, a number of instrument systems (Mid systems) have been proposed. Those systems are located at the middle position between conventional manual instrument systems and robotic surgery systems. This paper proposes some forceps that belong to the Mid systems. First, this paper discusses and sets up the conditions that should be considered when designing the Mid system instrument. This authors think it important to enable the forceps' jaws to rotate about its axis smoothly, to give the end effector with multi-d.o.f. motion (MDFM) the abilities of fine motion like that required for fine suturing work. Under the conditions of the Mid system, we discuss how we order the many motions of the instrument with MDFM by means of only one hand (Motion order). This paper tried forceps 'A' that has some electric switches for the Motion order for minimizing the end effector's tremble that may be transferred from the hand ordering the MDFM motions. The trial operations show that the fine touches of the switches cause little trembling on the end effector of forceps 'A'. However, they also show that it seems difficult for the end effector to take the required pose speedily. To respond to another demand that the end effector's pose has to change speedily, this paper proposes forceps 'B' that has a new mechanism that can give the pose of the end effector by taking the hand pose as the required one for the end effector separately from the jaws' rotational motion. The trial operations show that the new mechanism enables us to easily change the pose of the end effector. Even so, they also show that, in rapid pose change, the operator felt it difficult to follow the procedure after the pose change of the end effector. This paper clarifies, to a certain extent, the relationships of the Motion order method by the hand and the abilities of the end effector of the forceps.

The end effect in air pollution: The role of perceived difference