Mediating Between Contact Feasibility and Robustness of Trajectory Optimization Through Chance Complementarity Constraints

As robots move from the laboratory into the real world, motion planning will need to account for model uncertainty and risk. For robot motions involving intermittent contact, planning for uncertainty in contact is especially important, as failure to successfully make and maintain contact can be catastrophic. Here, we model uncertainty in terrain geometry and friction characteristics, and combine a risk-sensitive objective with chance constraints to provide a trade-off between robustness to uncertainty and constraint satisfaction with an arbitrarily high feasibility guarantee. We evaluate our approach in two simple examples: a push-block system for benchmarking and a single-legged hopper. We demonstrate that chance constraints alone produce trajectories similar to those produced using strict complementarity constraints; however, when equipped with a robust objective, we show the chance constraints can mediate a trade-off between robustness to uncertainty and strict constraint satisfaction. Thus, our study may represent an important step towards reasoning about contact uncertainty in motion planning.

Bath for Underwater Horizontal Polysegmental Kinesitraction Treatment of the Spine and Lower Extremities Lesions, Methods of Its Use

Introduction. Traction in dynamic mode (kinesitraction) is a new direction protected by patents of Ukraine, which combines the procedure of traction and motor activity. Traction treatment of the spine in a dynamic mode plays an important role in the treatment of the musculoskeletal system, so it is important to understand the structure, mechanisms and features of the structures involved in these processes, including the bath developed by us. The aim of the study. To acquaint with a design of a bath for underwater horizontal polysegmental kinesitraction treatment of the spine and lower extremities lesions, methods of its use. Materials and methods. Content analysis, method of system and comparative analysis, bibliosemantic method of studying the actual scientific researches on baths’ designs for underwater horizontal polysegmental kinesitraction treatment of the spine and lower extremities lesions, methods of its use are used. Sources are searched in scientometric databases: PubMed, Medline, Springer, Google Scholar, Research Gate by tags: kinesitraction, musculoskeletal system, underwater horizontal treatment of the spine, traction, traction system. 22 English and Ukrainian literary sources which describe this problem were selected and analyzed. The description of the bath for underwater horizontal segmental traction treatment of the spine and lower extremities lesions in the dynamic mode was used (Certificate of copyright registration for a scientific work N 99985, 25.10.2020). Results. The designed by us bath for underwater polysegmental kinesitraction treatment of lesions of the spine and lower extremities (Certificate of registration of copyright to a scientific work N 99985, 2020) is intended for the treatment of diseases of the musculoskeletal system, internal organs, disorders of vital systems in the aquatic environment by exposure to dosed motor and traction loads. The design includes a water bath, armrests, handles, footrest, racks, cervical block system, chest block system, lumbar block system, head restraint belt, chest strap, pelvic girdle, shin strap, cable, load. Using a bath it is possible to carry out tractions of the cervical, thoracic, lumbar spine, their combinations, lower extremities, or total provide the traction. Conclusions. Traction treatment of the spine in a dynamic mode plays an important role in the treatment of the musculoskeletal system, being more effective than static. The understanding of the structure, methods and features of the structures involved in these processes, including our developed baths for underwater horizontal polysegmental hydrokinesitraction treatment of lesions of the spine and lower extremities, based on the correction of disorders of the nervous, musculoskeletal systems caused by morphological, biochemical, physiological mechanisms of stimulation of the functions of vital systems, regeneration processes, and the proposed methods of their use is an important component of effective treatment of diseases of the musculoskeletal system. Keywords: kinesitraction, musculoskeletal system, underwater horizontal treatment of the spine, traction, traction system.

3D stability analysis method for toppling failure on rock slopes

In this paper, an optimized solution method is proposed for the 3D stability analysis of rock slopes subject to toppling failure based on their geometric and mechanical properties. It was verified by a 3D block system that focused on the geometric properties of toppling slopes as a research object, considering the force and its action point on the interface of the block system as unknown variables, as well as introducing the definition of a safety factor considering both tension and shear strength reduction. The proposed method implied setting constraints, such as the balance equation corresponding to block force and moment, as well as non-violation of the yield criterion, considering the minimum value of the safety factor as the objective function. It was applied to the analysis of two typical 3D models simulating toppling failure on slopes. The example of a 3D spherical toppling slope was reconstructed and corroborated by calculations. The experimental results demonstrated that the proposed method could appropriately reflect the mechanical properties and stability behavior of a 3D toppling slope, thereby facilitating the analysis of the stability of 3D toppling rock slope model.

Reproduction Method of Rockfall Geologic Hazards Based on Oblique Photography and Three-Dimensional Discontinuous Deformation Analysis

Rockfall geologic hazards are widely distributed. Due to their concealed nature, rockfalls are difficult to investigate using traditional contact survey methods, and the hazards they pose affect major projects and people’s safety. Reproducing methods, including scene survey and movement process analysis, are primary tasks used to prevent these hazards; however, few reconstruction methods can directly apply the parameters of the rockfall geologic hazards obtained by the scene survey to evaluate the movement process. To address this problem, a method of reproduction based on oblique photography and three-dimensional discontinuous deformation analysis (3D-DDA) is proposed; the method consists of three key techniques (oblique photography, 3D rock block system modeling, and 3D rock block system analysis). First, geometric characteristic parameters of the terrain, rockfall, and discontinuities are extracted based on oblique photography using an unmanned aerial vehicle (UAV). Second, the block system model of rockfall is reconstructed by using 3D computational geometry theory and taking these geometric characteristic parameters as an input. Finally, the whole evolution process of rockfall geologic hazard, including initiation, movement, and accumulation, is simulated by the 3D-DDA method. To verify the practicability of this reproduction method, a typical rockfall geologic hazard, located in the K8 + 050 section of the Gaohai expressway, Yunnan, China, is studied. In addition, the characteristics of 19 dangerous rock masses in the survey area are clarified, and the geometric features of the discontinuities in the rock masses are extracted based on oblique photography using an UAV. The block system model of a potential rockfall is reconstructed, the movement trajectory is simulated by the 3D-DDA method, and the evolution process of velocity and kinetic energy of the rockfall verifies that the spatial layout of the current three-level passive protective nets system is reasonable. The case study indicates that the proposed method provides a geological and mechanical model for the risk assessment of rockfall geologic hazards.

Study on the influence of stress wave disturbance on ultra-low friction effect of broken blocks

With the increase of mine mining depth, deep rock mass tends to be broken into block medium. The roof-rock layer-floor can be regarded as block system fractured rock mass. Under the condition of high ground stress and mining disturbance, the ultra-low friction effect of block system fractured rock mass is easy to occur, and then induce rock burst and other disasters. Taking the block rock mass as the research object, the self-developed ultra-low friction test system is used to carry out the experimental research on the ultra-low friction effect of the broken block under the condition of stress wave disturbance. Taking the horizontal displacement of the working block as the characteristic parameter reflecting the ultra-low friction effect, by changing the stress wave disturbance frequency and amplitude, the characteristic law of the horizontal displacement, acceleration and energy of the working block during the occurrence of the ultra-low friction effect is analyzed. The research results show that the stress wave disturbance frequency is related to the generation of ultra-low friction of the broken block. The disturbance frequency of the stress wave is within 1 ~ 3Hz, and the maximum acceleration and horizontal displacement of different broken degree blocks increase significantly. This frequency range is prone to ultra-low friction effect. The greater the intensity of the stress wave disturbance, the higher the degree of block fragmentation, and the more likely to have ultra-low friction effects between the blocks. The greater the intensity of the horizontal impact load, the higher the degree of rock mass fragmentation, the easier it is for ultra-low friction effects to occur. Stress wave disturbance and horizontal impact are the main reasons for the sliding instability of broken blocks. When the dominant frequency of the kinetic energy of the broken block is within 20 Hz, the ultra-low friction effect is more likely to occur.

Jointed Tubing Injector Snubbing on Extended Reach Wells

OBJECTIVE / SCOPE An injector has been developed that is able to continuously move conventional jointed tubing in and out of wells that may be underbalanced. It is an advantage to use the jointed tubing injector rather than coiled tubing or conventional hydraulic snubbing due to cost, speed of operation, transportation, effectiveness, and safety. The paper will describe the function and application of the jointed pipe injector. METHODS, PROCEDURES, PROCESS An injector has been designed with retractable gripping segments integral to the gripper blocks that are able to function on conventional jointed tubing, over interconnecting couplings and with the advantages of continuously operating injector movement. The description is to include how the geometry of the retractable gripper block system works and how the technical and safety risks of a conventional snubbing system or coiled tubing are overcome. Configurations whereby the jointed tubing injector can be used to provide methods of completing wells that are safer and more efficient than coiled tubing or a conventional hydraulic snubbing jack will be presented. RESULTS, OBSERVATIONS, CONCLUSIONS The biggest limitation of coiled tubing is due to its size and residual bend, it is not capable of reaching the end of the well before the wellbore friction causes helical buckling. The OD of the coiled tubing is limited by the available reel sizes and the difficulty transporting the large reels due to road dimensional and weight limitations. Coiled tubing is not able to be rotated at any time in the well. The use of jointed tubing eliminates those limitations. When a well is being completed with a conventional hydraulic snubbing jack, the length of the stroke that the jack can take is limited by the allowable unsupported length of the tubing to ensure that it will not buckle. It is also forced to stop workstring movement each time the jack is reset therefore the static friction of the workstring must be overcome during each movement of the jacks. The design of the jointed tubing injector minimizes the unsupported length of the tubing and allows the continuous movement of the tubing. The operation is less labor intensive, and the controls can be moved to a position that is less exposed to danger. NOVEL / ADDITIVE INFORMATION The Jointed Tubing Injector can continuously move jointed tubulars in and out of a well. There is no other piece of equipment that will address as many of the problems that have been experienced in the completion of extended reach wells. The paper will describe the injector and control system and how it can be applied to solve the challenges.

Proposal for Modernisation of Large Block System Buildings (Lbs) - Facades – Lublin University of Technology

The over 40-years-old housing stock from the industrialized mass housing era is today functionally deficient and does not meet the current needs of residents. In particular, there are numerous architectural barriers, the systems are worn and obsolete, and the number of housing types is very limited. Examples of the modernization of multi-story residential buildings (the article presents those from Russia and Ukraine) confirm that this problem is universal, and a significant improvement of the building’s. utility value can be achieved through a relatively small modification of the building fabric: precast concrete structures of the buildings prove to be flexible enough to accommodate deep changes. The authors present a concept of modernization of a building erected in a “large block” system, typical for the Polish housing of the 1970s in many cities. The case study concerns a particular building located in Lublin in one of the large housing estates – the concept of its modernization is compatible with the local spatial development plan, the proposed solutions are architecturally coherent and technically feasible.