scholarly journals Quasi-Static Compliance Calibration of Serial Articulated Industrial Manipulators

2021 ◽  
Vol 15 (5) ◽  
pp. 590-598
Author(s):  
Nikolas Alexander Theissen ◽  
Monica Katherine Gonzalez ◽  
Asier Barrios ◽  
Andreas Archenti ◽  
◽  
...  
Keyword(s):  
Trajectory Optimization ◽  
Model Parameters ◽  
Static Stiffness ◽  
Static Compliance ◽  
Low Velocity ◽  
Double Ball Bar ◽  
Apparent Stiffness ◽  
Significant Difference ◽  
Industrial Manipulators ◽  
Ball Bar

This article presents a procedure for the quasi-static compliance calibration of serial articulated industrial manipulators. Quasi-static compliance refers to the apparent stiffness displayed by manipulators at low-velocity movements, i.e., from 50 to 250 mm/s. The novelty of the quasi-static compliance calibration procedure lies in the measurement phase, in which the quasi-static deflections of the manipulator’s end effector are measured under movement along a circular trajectory. The quasi-static stiffness might be a more applicable model parameter, i.e., representing the actual manipulator more accurately, for manipulators at low-velocity movements. This indicates that the quasi-static robot model may yield more accurate estimates for the trajectory optimization compared with static stiffness in the implementation phase. This study compares the static and apparent quasi-static compliance. The static deflections were measured at discretized static configurations along circular trajectories, whereas the quasi-static deflections were measured under circular motion along the same trajectories. Loads of different magnitudes were induced using the Loaded Double Ball Bar. The static and quasi-static displacements were measured using a linear variable differential transformer embedded in the Loaded Double Ball Bar and a Leica AT901 laser tracker. These measurement procedures are implemented in a case study on a large serial articulated industrial manipulator in five different positions of its workspace. This study shows that the measured quasi-static deflections are bigger than the measured static deflections. This, in turn, indicates a significant difference between the static and apparent quasi-static compliance. Finally, the implementation of the model parameters to improve the accuracy of robots and the challenges in realizing cost-efficient compliance calibration are discussed.

scholarly journals Antifungal Activity of Propyl Disulfide from Neem (Azadirachta indica) in Vapor and Agar Diffusion Assays against Anthracnose Pathogens (Colletotrichum gloeosporioides and Colletotrichum acutatum) in Mango Fruit

2021 ◽  
Vol 9 (4) ◽  
pp. 839
Author(s):  
Muhammad Rafiullah Khan ◽  
Vanee Chonhenchob ◽  
Chongxing Huang ◽  
Panitee Suwanamornlert
Keyword(s):  
Antifungal Activity ◽  
Mycelial Growth ◽  
Colletotrichum Gloeosporioides ◽  
Colletotrichum Acutatum ◽  
Model Parameters ◽  
Pathogenicity Test ◽  
Agar Diffusion ◽  
Wide Range ◽  
Significant Difference ◽  
Diffusion Assay

Microorganisms causing anthracnose diseases have a medium to a high level of resistance to the existing fungicides. This study aimed to investigate neem plant extract (propyl disulfide, PD) as an alternative to the current fungicides against mango’s anthracnose. Microorganisms were isolated from decayed mango and identified as Colletotrichum gloeosporioides and Colletotrichum acutatum. Next, a pathogenicity test was conducted and after fulfilling Koch’s postulates, fungi were reisolated from these symptomatic fruits and we thus obtained pure cultures. Then, different concentrations of PD were used against these fungi in vapor and agar diffusion assays. Ethanol and distilled water were served as control treatments. PD significantly (p ≤ 0.05) inhibited more of the mycelial growth of these fungi than both controls. The antifungal activity of PD increased with increasing concentrations. The vapor diffusion assay was more effective in inhibiting the mycelial growth of these fungi than the agar diffusion assay. A good fit (R2, 0.950) of the experimental data in the Gompertz growth model and a significant difference in the model parameters, i.e., lag phase (λ), stationary phase (A) and mycelial growth rate, further showed the antifungal efficacy of PD. Therefore, PD could be the best antimicrobial compound against a wide range of microorganisms.

A Complete, Continuous, and Minimal Product of Exponentials-Based Model for Five-Axis Machine Tools Calibration With a Single Laser Tracker, an R-Test, or a Double Ball-Bar

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Peng Xu ◽  
Benny C. F. Cheung ◽  
Bing Li
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Rigid Bodies ◽  
Error Model ◽  
Laser Tracker ◽  
Calibration Model ◽  
Transformation Matrices ◽  
Double Ball Bar ◽  
Ball Bar ◽  
Five Axis

Calibration is an important way to improve and guarantee the accuracy of machine tools. This paper presents a systematic approach for position independent geometric errors (PIGEs) calibration of five-axis machine tools based on the product of exponentials (POE) formula. Instead of using 4 × 4 homogeneous transformation matrices (HTMs), it establishes the error model by transforming the 6 × 1 error vectors of rigid bodies between different frames resorting to 6 × 6 adjoint transformation matrices. A stable and efficient error model for the iterative identification of PIGEs should satisfy the requirements of completeness, continuity, and minimality. Since the POE-based error models for five-axis machine tools calibration are naturally complete and continuous, the key issue is to ensure the minimality by eliminating the redundant parameters. Three kinds of redundant parameters, which are caused by joint symmetry information, tool-workpiece metrology, and incomplete measuring data, are illustrated and explained in a geometrically intuitive way. Hence, a straightforward process is presented to select the complete and minimal set of PIGEs for five-axis machine tools. Based on the established unified and compact error Jacobian matrices, observability analyses which quantitatively describe the identification efficiency are conducted and compared for different kinds of tool tip deviations obtained from several commonly used measuring devices, including the laser tracker, R-test, and double ball-bar. Simulations are conducted on a five-axis machine tool to illustrate the application of the calibration model. The effectiveness of the model is also verified by experiments on a five-axis machine tool by using a double ball-bar.

scholarly journals Non-whiplash soft tissue injuries following low-velocity impact collisions: A retrospective analysis

2019 ◽  
Vol 88 (1) ◽  
pp. 31-36
Author(s):  
Holly Morris ◽  
David Ensor ◽  
Chika Uzoigwe ◽  
Farzad Shabani ◽  
Harish Kurup
Keyword(s):  
Soft Tissue ◽  
Road Traffic ◽  
Psychological Symptoms ◽  
Spinal Injury ◽  
Soft Tissue Injuries ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
Significant Difference ◽  
Tissue Injuries

Whiplash is the most common injury reported in low-velocity impact road traffic accidents, but claimants report a range of other soft tissue injuries and we looked at the prevalence of these and any patterns. We retrospectively reviewed reports from the medico-legal practice of an orthopaedic surgeon. We collected data on 609 claimants. Sixty-two per cent were women (p < 0.0001). Majority (90.3%) reported an injury to at least one other area than neck, and 48% of claimants reported shoulder pain. Hand/wrist injuries were almost exclusive to drivers (p = 0.0013). Those with knee injuries were older than those without (p = 0.001). There was a significant difference in the age of patients with different spinal injury patterns (p < 0.0001). Occupational status did not appear to influence the pattern of injuries (p = 0.06). Psychological symptoms were associated with a greater number of body parts injured (p < 0.01). Our data confirm a strong association between these soft tissue injuries and psychological symptoms.

Nystagmus characteristics of healthy controls

2020 ◽  
Vol 30 (6) ◽  
pp. 345-352
Author(s):  
Allison S. Young ◽  
Sally M. Rosengren ◽  
Mario D’Souza ◽  
Andrew P. Bradshaw ◽  
Miriam S. Welgampola
Keyword(s):  
Upright Position ◽  
Community Dwelling ◽  
Spontaneous Nystagmus ◽  
Slow Phase ◽  
Healthy Controls ◽  
Positional Nystagmus ◽  
Low Velocity ◽  
Video Oculography ◽  
Significant Difference ◽  
Horizontal Nystagmus

BACKGROUND: Healthy controls exhibit spontaneous and positional nystagmus which needs to be distinguished from pathological nystagmus. OBJECTIVE: Define nystagmus characteristics of healthy controls using portable video-oculography. METHODS: One-hundred and one asymptomatic community-dwelling adults were prospectively recruited. Participants answered questions regarding their audio-vestibular and headache history and were sub-categorized into migraine/non-migraine groups. Portable video-oculography was conducted in the upright, supine, left- and right-lateral positions, using miniature take-home video glasses. RESULTS: Upright position spontaneous nystagmus was found in 30.7% of subjects (slow-phase velocity (SPV)), mean 1.1±2.2 degrees per second (°/s) (range 0.0 – 9.3). Upright position spontaneous nystagmus was horizontal, up-beating or down-beating in 16.7, 7.9 and 5.9% of subjects. Nystagmus in at least one lying position was found in 70.3% of subjects with 56.4% showing nystagmus while supine, and 63.4% in at least one lateral position. While supine, 20.8% of subjects showed up-beating nystagmus, 8.9% showed down-beating, and 26.7% had horizontal nystagmus. In the lateral positions combined, 37.1% displayed horizontal nystagmus on at least one side, while 6.4% showed up-beating, 6.4% showed down-beating. Mean nystagmus SPVs in the supine, right and left lateral positions were 2.2±2.8, 2.7±3.4, and 2.1±3.2°/s. No significant difference was found between migraine and non-migraine groups for nystagmus SPVs, prevalence, vertical vs horizontal fast-phase, or low- vs high-velocity nystagmus (<5 vs > 5°/s). CONCLUSIONS: Healthy controls without a history of spontaneous vertigo show low velocity spontaneous and positional nystagmus, highlighting the importance of interictal nystagmus measures when assessing the acutely symptomatic patient.

Seismic detection of overpressuring and fracturing: An example from the Qaidam Basin, People’s Republic of China

Geophysics ◽  
1993 ◽  
Vol 58 (10) ◽  
pp. 1532-1543 ◽  
Author(s):  
Robert J. Paul
Keyword(s):  
Oil And Gas ◽  
Qaidam Basin ◽  
High Amplitude ◽  
Seismic Survey ◽  
Low Velocity ◽  
Velocity Anomaly ◽  
Deep Well ◽  
Significant Difference ◽  
Seismic Amplitudes ◽  
Definition Of

Shallow hydrocarbon reserves were discovered in 1959 in the Nan Yi Shan structure located near the western corner of the Qaidam Basin. The first successful deep well encountered an overpressured zone at 3000 m that resulted in a well blowout. To improve the structural definition of the field and delineate the overpressured layer a 3-D seismic survey was conducted. A region of anomalous seismic time sag associated with fracturing and small quantities of oil and gas was identified on the northwest plunging nose of the Nan Yi Shan anticline. The distribution of stacking (NMO) velocities in this region was regarded as abnormal; stacking velocities derived on the steeply dipping flanks adjacent to the sag anomaly were found to be slower than those on the shallower crest. Ray‐trace modeling of a buried low‐velocity anomaly provided a possible geometric solution to explain both the time variant nature of the sag and the unusual stacking velocity signature associated with it. A significant difference in seismic and sonic traveltimes was also observed for wells that penetrated the sag region and was attributed to localized fracturing. In a deeper interval, seismic amplitudes were used to identify gas‐saturated fracture porosity and to describe the spatial limits of overpressuring within a thin‐bed reservoir. Wells drilled through high‐amplitude anomalies encountered overpressuring, those drilled in a region of moderate seismic amplitude tested significant quantities of gas, and wells located outside the region of good coherent signal encountered poor or no hydrocarbon shows. These results demonstrate that with good quality seismic data and sufficient lateral and vertical resolution, thin fractured hydrocarbon‐bearing reservoirs can be delineated and overpressure zones identified.

Sign in / Sign up

Export Citation Format

Share Document