In this paper, a stability-guaranteed Cartesian free-space motion control for the redundant articulated hydraulic construction crane is addressed in order to increase system safety and productivity. ...To cope with the nonlinearities of coupled mechanical linkage dynamics of articulated systems and the inherently strong nonlinearities of hydraulic actuator dynamics, the proposed controller is designed based on the recently introduced Virtual Decomposition Control (VDC) approach. The VDC approach, which was developed especially for the control of complex robotic systems, allows the conversion of the control problem of the entire system to a control problem of individual subsystems, while rigorously guaranteeing the stability of the entire hydraulic system. In the experiments it is demonstrated that, the proposed controller is able to extensively cope with the highly nonlinear nature of the articulated hydraulic system, and an improved control performance is achieved compared to the current state-of-the-art studies in the category of the hydraulic robot manipulators.
•State-of-the-art control performance is achieved for the studied system.•Results are achieved with the low-tech hydraulic construction crane.•Stability of the highly nonlinear articulated hydraulic crane is guaranteed.•The proposed method can be easily retrofitted into existing systems.
•We match core OR-problems with construction industry-specific models.•The literature is categorized; problems and applied techniques are briefly described.•Shortcomings regarding descriptions, ...techniques, computational tests are identified.•Future research topics including both models and solution techniques are suggested.
Quantitative methods and techniques from operations research (OR) are well-accepted in many industries, e.g. the manufacturing industry or the transportation industry. Similarly, numerous applications in the field of construction can be found in the academic literature. This paper gives an extensive overview on a number of popular fields where OR methods are applied in the construction industry. These fields comprise layout and location planning for construction facilities, scheduling of construction projects and problems related to construction cranes. While the first two topics relate to traditional problems in the field of OR, the latter one is motivated mainly by the construction industry. In either case, this review presents a survey of papers in the scientific literature. Each paper is categorized and problem setting as well as techniques applied are briefly described.
Existing methods of assessing the influence of factors allow to determine this influence indirectly without taking into account the speed (intensity) of their influence and the relationship between ...them. The article proposes a method of assessing the complex impact of significant factors on the failures of cranes, the relationship between which is presented in the form of a kinetic system, changing over time depending on the change of any active factor. The accumulated statistical material of accidents on cranes of different kinds are the initial data in the conduct of studies to assess the cumulative effect of various factors on the performance of crane equipment. The proposed methodology will take into account the intensity of the changes in factors associated with their change. This takes into account the kinematic state of the current factors, which is determined by the speed of change of each external factor, depending on the related factors acting on it. The results of the evaluation of crane failures under the proposed methodology do not contradict the studies of other authors and allow to assess the intensity of mutual influence of factors on each other.
An infinite sequence (Y
1, Y
2,…) of independent Bernoulli random variables with P(Y
i
= 1) = a / (a + b + i - 1), i = 1, 2,…, where a > 0 and b ≥ 0, will be called a Bern(a, b) sequence. Consider ...the counts Z
1, Z
2, Z
3,… of occurrences of patterns or strings of the form {11}, {101}, {1001},…, respectively, in this sequence. The joint distribution of the counts Z
1, Z
2,… in the infinite Bern(a, b) sequence has been studied extensively. The counts from the initial finite sequence (Y
1, Y
2,…, Y
n
) have been studied by Holst (2007), (2008b), who obtained the joint factorial moments for Bern(a, 0) and the factorial moments of Z
1, the count of the string {1, 1}, for a general Bern(a, b). We consider stopping the Bernoulli sequence at a random time and describe the joint distribution of counts, which extends Holst's results. We show that the joint distribution of counts from a class of randomly stopped Bernoulli sequences possesses the mixture of independent Poissons property: there is a random vector conditioned on which the counts are independent Poissons. To obtain these results, we extend the conditional marked Poisson process technique introduced in Huffer, Sethuraman and Sethuraman (2009). Our results avoid previous combinatorial and induction methods which generally only yield factorial moments.
This paper describes the conversion of an existing full-scale 5-ton payload crane into a semi-automatic “Handling Robot”. By its size, degrees of freedom, and mode of operation this crane resembles ...typical construction cranes, which can be enhanced in the same manner. The new control system allows operation of the crane in either a manual or a semi-automatic mode, and it can be taught to memorize up to 50 different benchmarks, i.e. particular points at the construction site, as well as safe routes among them. The major components of the system include: a programmable controller, three speed regulators, three encoders, several limit switches, a wireless remote control set, and a user-friendly M.M.I. (Man-Machine-Interface). Most of the components can be installed
externally in the vicinity of the crane's joints and inside the cabin, with minimal intervention in the original wiring. Following the physical retrofitting of the crane, a series of tests examined performance, accuracy, repeatability, and safety aspects. They demonstrated a 15–50% shortening of typical work cycles, high accuracy and repeatability, and a generally safer operation due to pre-tested paths and smoother movements with less sway and swing of the load.
It was spring in East Oakland, California. The annual Digital Storytelling Contest’s theme had just been announced—Coming to California—and a mounting stir accumulated between Rooms 107 and 108, the ...ninth-grade social studies and English classrooms. Over the course of two months, the stir filled the hallways of the building and ultimately the rest of the high school grounds, newly split into three small schools. The contest’s theme provided a unique opportunity for students to write, produce, edit, and share biographical stories about their family’s journey to California. It was part of a multicultural studies curriculum. Ms. Gantry, a
IN 1970, A TRAVEL EDITOR at theLos Angeles Timesasked me to go to Sauk Centre, Minnesota, Sinclair Lewis’s boyhood home, and write an article about the town believed to be the model for Gopher ...Prairie in the novelMain Street. Main Streetwas first published in 1920, and my piece would tie in with the fiftieth anniversary of the book’s release.
Ben Dubois was the last person alive in Sauk Centre who was born the same year as Lewis—1885—and who grew up with him. He affirmed that life in Sauk Centre was often painful for Harry
This essay examines the Proceedings of the Black State Conventions of the 1840s as political documents central to our understanding of early African American print culture and the role of print ...circulation, as metaphor and as medium, for defining participatory politics more generally in the early United States.¹ Just as the struggle against slavery and kidnapping generated the national conventions of the 1830s, activism for political rights, especially the suffrage, fueled the state conventions in the 1840s. The very acts of organizing and holding conventions to petition for voting and other rights created a public black civic presence, demonstrating that
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