On the mechanical design of a Stewart platform-based robotic end-effector

The article provides mathematical modeling of the output signal from the acoustic path of magnetostrictive linear or angular displacement transducers. Some issues of engineering design of the channel for generating a pulse signal of a magnetostrictive linear displacement converter, using spectral representations of an analog playback signal, are also considered and analyzed. An easy-to-implement method for generating a pulse measurement signal is to compare an analog signal with a constant threshold level. However, an analog signal is influenced by a significant number of destabilizing factors that affect the process of converting an analog signal into a pulse signal. The analysis showed that for analog-pulse conversion, it would be more effective to use the conversion method for some characteristic points associated with the analog signal, to which the comparison level is attached. In the course of research, it was found that the curve of the first derivative of the playback signal has several points associated with the intersection of the derivative and the zero line. The coordinate of one of the points corresponds to the middle of the region of the sound wave moving along the waveguide, which is weakly sensitive to signal distortions and can be used to form a pulse measuring signal using extreme detection methods known in the theory of magnetic recording on a magnetic medium. The article deals with the use of spectral representations of an analog signal depending on the waveguide length when selecting parameters of the pulse signal generation channel for the measuring path.

With the rapid development of automation and intelligence industries, the performance of robot end effectors directly affects the operational efficiency and application range of robot systems, so its research and optimization are particularly crucial. This study first identified the performance bottlenecks and limitations of existing robot end effector designs in different application scenarios through systematic analysis. Then, a new type of actuator prototype was developed using modular design methods, combined with the latest materials science research and mechatronics integration technology. In the experimental verification stage, the effectiveness of the new design was confirmed by comparing and testing the performance of new and old actuators in key performance indicators such as precision, response speed, and load capacity. The average deviation was generally low, mostly between 0.05 and 0.09 millimeters, indicating that the actuator can accurately locate the preset target position in most cases. The value of this study lies in the fact that the proposed end effector design scheme not only improves the operational performance of robots, but also has good universality and adaptability, laying a solid foundation for the future development of robotics technology. These achievements are expected to greatly promote the widespread application of robotics technology in industries such as manufacturing, healthcare, and services, and improve the automation level of the entire industry.

This paper describes a novel robotic end-effector and a method for grasping deformable objects with undefined shapes and geometry, such as sacks and bags. The first prototype end-effector, designed for applications in the U.S. Postal Service, is comprised of two parallel rollers with gripping surfaces in which the rollers are pushed toward each other. When the end-effector comes into contact with any portion of the deformable object, the rollers turn inwardly so that a graspable portion of the object is dragged between the rollers. The rollers stop rotating when a graspable portion of the material/object is caught in between, allowing the object to be maneuvered by the robot. The object is released when the rollers turn outwardly. The end-effector described in this article can grab and hold filled sacks from any point on the sack, regardless of the sack's orientation. Experimental evaluation of the end-effector has proven the design and implementation remarkably effective. This article describes the hardware, control method, and design issues associated with the end-effector. Note to Practitioners - Delivery and postal services around the world currently use sacks to hold letters, magazines, and small boxes. The considerable weight of these sacks, their lack of handles, eyelets, or other operator interfaces, and the unpredictable shape and size of the packages within create awkward and uncomfortable handling predicaments for mail handlers at all U.S. Postal Service distribution centers. Currently, no robotic hand or end-effector is commercially available to grab and hold sacks effectively, so sacks must be handled manually by postal employees in distribution centers. This paper describes the design of a novel robotic end-effector for manipulating deformable objects with undefined shapes, such as sacks and bags. This device, which does not mimic human hand architecture, is simple and practical; it makes use of the friction between two rotating rollers to grab sack material when it is in close proximity of the end-effector. The rollers cease rotation when sufficient sack material is collected between the rollers to support the sack. They reverse their rotation, and turn outwardly to release the sack again. This end-effector is able to grab a sack at any point, does not require the edge of the sack to be gathered and flattened prior to grasp, does not require the sack to be placed on its bottom, needs no operator intervention, does not use the weight of the sack to lock and secure the sack in the end-effector, and does not damage the sack contents.

Bedside safety rails: assessment of strength requirements and the appropriateness of current designs

The design and construction of a 1:12 scale prestressed concrete spine beam model of an elevated highway intersection is described. The model represents a four-lane carriageway bifurcating into three-and two-lane spans, and is of typical single and double box girder construction, incorporating large side cantilevers. The bridge, highly curved in plan, is continuous over three central supports and torsionally restrained at three outer supports. The strain history during prestressing and the accuracy of the data are discussed. A total of over 1000 electical resistance strain gauges, linear displacement transducers and dial gauges were used to provide details of the state of strain, reactions and prestress force at all stages. (Author/TRRL)

Mechanical coupling between the ribs and sternum in the dog

The physical quantities involved in a triaxial testing device have mostly been monitored with electric sensors. These sensors are currently subject to short circuit when submerged under water and electromagnetic interference (EMI). Waterproofing and EMI noise filtration have often been a challenge to the triaxial test set-up. These drawbacks can be substantially minimized when using optic fiber sensors. The optic fiber Bragg grating (FBG) sensors have the additional advantage of being partially distributive where multiple sensors can share the same signal transmission line. Taking advantage of these unique capabilities, the authors explored the possibility of converting all pressure/force and linear displacement transducers in a triaxial testing device into FBG based sensors. A series of shearing tests on unsaturated and saturated soil specimens were carried out using the new FBG sensored triaxial testing device. In most cases, the measurement of physical quantities was paired with electric sensors so that the results can be compared. This paper describes the principles of the individual FBG sensor designs and demonstrates their applications in triaxial testing.

Since a significant number of implant failures have been reported in association with the procedure of open wedge valgus high tibial osteotomy, the initial biomechanical stability of different fixation devices was investigated in this study. Fifteen third generation Sawbones composite tibiae were used as a model. Four different plates were tested: a short spacer plate (OWO) (n = 4), a short spacer plate with multi-directional locking bolts (MSO) (n = 5), a prototype version of a long spacer plate with multi-directional locking bolts (MSOnew) (n = 2), and a long medial tibia plate fixator with locking bolts (MPF) (n = 4). All opening wedge osteotomies were performed by the same surgeon (PL) in a standardized fashion. Axial compression of the tibiae was performed using a materials testing machine under standardized alignment of the loading axis. Single load to failure tests as well as load-controlled cyclical failure tests were performed. The required force and cycles to failure were recorded. Osteotomy gap motion was measured using linear displacement transducers. Residual stability after failure of the opposite lateral cortex was analysed. Failure occurred at the lateral cortex bone-bride in all tested implants. The rigid long plate fixator (MPF) resisted the greatest amount of force (2,881 N) in the single load to failure tests. In the cyclical load-to-failure tests, the constructs with MPF resisted more than twice the amount of loading cycles when compared to the short spacer plates. The osteotomy gap motion was smallest in the MPF, with a reduction of the displacements of up to 65, 66 and 88%, when compared to OWO, MSO and MSOnew, respectively. The highest residual stability after failure of the lateral cortex was observed in MPF as well. The results suggest that the implant design strongly influences the primary stability of medial opening wedge tibial osteotomy. A rigid long plate fixator with angle-stable locking bolts yields the best results.

The authors describe a circuit synthesis program called FIESTA and its use is a teaching tool in both undergraduate and graduate courses. The program is very easy to use, is highly interactive, and contains graphics capabilities to give the student insights in active RC-filter design. FIESTA makes easier and faster the solution of the filter approximation problem, which traditionally involves use of tables and nomographs for a selected number of specifications. It is especially practical when a set of design specifications is not included in the tables. Highlights include Butterworth, Chebyshev, and Cauer approximations, and an arbitrary group-delay approximation. Circuit implementation is done using for illustration the Tow-Thomas biquadratic active RC-filter as the main basic block. Several computer exercises are suggested to complement classroom lectures and traditional 'paper and pencil design'. Addition of code is easy to implement in FIESTA. >

The subject is treated from the point of view of the design engineer who, being presented with a set of design specifications, is called upon to develop the equipment. The design specifications will contain all the relevant information on operational requirements from accuracy through sensitivity, reliability, maintainability, dependability, etc. His requirements as to manpower and facilities are discussed as well as considerations during the various development phases, followed by a more detailed treatment of criteria which make an instrument acceptable. Practical considerations in the design of meteorological instruments, mainly of the simpler and widely used types, are illustrated by examples in which some design concepts and new materials have been used with an aim to further the state of the art. Special emphasis is given on how to design for reliability and maintainability of measuring equipment. Problems encountered due to exposure and the influence of the environment on the performance of instruments are discussed as well as ways to meet or evade them by suitable design features. The equipment used as examples include instrument shelters and a thermo-hygrograph.

The small modular reactor (SMR) class core design concept of once-through SuperCritical light Water-cooled Reactor (SCWR) with fast neutron spectrum (Super FR) is being developed at Waseda University. The preceding studies revealed that SMR class Super FR core can be designed, whose performance is compatible to large Super FR core with respect to average power density and average coolant outlet temperature with small core pressure drop, which is favorable from the viewpoint of achieving natural circulation cooling after reactor shutdown. However, consequences of severe accident of such SMR class Super FR has never been considered. Two major issues need to be addressed. The first issue is the fundamental issue for a water-cooled reactor, which is the possibility of the whole core meltdown as the coolant boils off at low temperature under depressurized condition. Second issue is the fundamental issue for a fast spectrum core, which is to avoid re-criticality of molten core as the reactivity increases with core compaction. With the above described background, this study proposes In-Vessel Retention (IVR) of SMR class Super FR, which can avoid re-criticality even if the whole core relocates to the lower plenum of the Reactor Pressure Vessel (RPV). The debris coolability may be a subject for the future study. The core characteristics with a given set of design specifications and criteria are evaluated based on fully coupled neutronics and thermal-hydraulics core burnup calculations. The neutronics calculations are based on interpolation of macroscopic cross sections with neutron diffusion approximation (SRAC and COREBN codes with JENDL-4.0 nuclear data library). The thermal-hydraulics calculations are based on in-house code that adopts single channel model with Watts’ correlation for evaluating supercritical water heat transfer. The batch fuel shuffling pattern is considered to evaluate the equilibrium core characteristics. The debris criticality is evaluated based on Monte-Carlo based method (MVP) to consider the RPV lower plenum and debris configurations. The fuel debris are assumed to be homogeneous. Firstly, for a given discharge burnup, quantitative relationship between the core criticality and the debris criticality is evaluated. The results show that downsizing the core increases the debris criticality when relocated to the RPV lower plenum, because the Pu enrichment needs to be raised to attain the same discharge burnup with larger neutron leakage. The results also show that some measures are necessary to prevent re-criticality of the debris if the whole core is assumed to relocate to the lower plenum. Then, the new “debris dispersion IVR” concept is proposed. In this concept, heat resistant structure (tentatively ZrO2), which contains some neutron absorbing material (tentatively, B4C) is placed at the center of the lower plenum to disperse the debris and gain neutron leakage and absorption. Then, the trade-off relationships between the core discharge burnup and the size of the debris dispersion structure are evaluated with considerations of core design specifications such as average Pu enrichment, operation cycle length, and fuel shuffling patterns.

The existence of multi-dimensional tradeoffs among performance metrics is an impediment to the development of reliable Electronic Design Automation (EDA) tools for the design of analog circuits. To overcome this limitation, soft computing techniques that have functionality similar to the human brain are being explored. This work proposes a methodology for the development of a fast and accurate Artificial Neural Network (ANN) model for analog circuits, to achieve optimization of its design, considering a 2-stage op-amp for illustration. In order to map complex and multiple input-output relationships of analog circuits, an ANN architecture of a single hidden layer with its neuron count selected to be between the number of neurons in the input and output layers is proposed. The ANN model is developed in the MATLAB environment, and trained using SPICE-generated performance dataset. For a given set of performance metrics, the ANN model generated designs are validated against SPICE simulations. It is demonstrated that trained ANN models substitute the circuit simulator, to achieve design optimization, in a single iteration, for a new set of design specifications.

One of the tenets of Quality-by-Design (QbD) initiatives is the determination of a set of input parameters, called a design space, that ensures that the system outputs lie within a set of design specifications. Existing methods for the construction of design spaces for nonlinear systems are described by box constraints on the input parameters, which greatly limit the size of the design space specifications. This observation motivates the definition of the skewed spherical structured singular value, which is a generalization of both the skewed structured singular value and the spherical structured singular value. The scaled main loop theorem for the skewed spherical structured singular value is proved, which involves somewhat different steps due to the presence of the Frobenius norm. This theorem is used to derive a numerical algorithm that characterizes the ellipsoidal set of allowable real parametric uncertainties that achieve the output specifications for linear fractional systems.

Robots are expected to perform a variety of household tasks. Tasks such as bed making and tucking textile layers during seat manufacture represent a particular challenge, as they require both sensitive manipulation and strong pushing capabilities. In this paper, we present a robotic solution for automated bed making with a force-sensing robot arm and an end effector for textile manipulation, which can manipulate textiles, as well as apply high forces to tuck a textile into a small space. The system can also use its fingertips to confirm grasp success by detecting the grasped material. The end effector design is available open source. We experimentally confirm the proposal’s effectiveness in the last part of the bed making task.

The influence of shade on the growth and sink activity of young flower heads and peduncles of white clover (Trifolium repens L.) plants was measured in controlled environments. Measurement of the peduncle elongation rate using a linear voltage displacement transducer showed that when the inflorescence alone was shaded, peduncle elongation was higher than in the light. Translocation studies using nC-labelling techniques showed that shading the inflorescence alone had little effect on translocation of assimilates into the inflorescence but induced a major change in partitioning of assimilates within it. Peduncle elongation induced by shade accompanied an increase in partitioning of photoassimilates to the peduncle, at the expense of the flower head.