Boom Movements Research Articles

MODELLING AND 3D PRINTING OF JCB ARM

The Hydraulic excavator machines are heavy duty earth movers consisting of a boom, arm and bucket. It works on principle of hydraulic fluid with hydraulic cylinder and hydraulic motors. The Hydraulic excavator arm operation require coordinated movement of boom, arm and bucket. The important criteria for the design to be safe is that, the digging forces developed by actuators must be greater than that of the resistive forces offered by the surface to be excavated. The main objective of this paper is to perform design and analysis Excavator Arm for the calculated Force. The CATIA software is used for making the 3D model of the excavator arm linkage. By using ANSYS workbench software analysis of the excavator arm is done at existing digging force and lifting force. Excavator bucket is very crucial element of hydraulic excavator. The whole loads of excavated materials have been carried out by this element. As the present mechanism used in excavator arm is subjected to deformation and bending stresses during lifting and digging operation respectively, because of which failure occurs frequently at the bucket end of the arm. Keywords: Excavator arm, Digging force, CATIA, ANSYS 16.0.

A REVIEW PAPER ON MODELLING AND 3D PRINTING OF JCB ARM

The Hydraulic excavator machines are heavy duty earth movers consisting of a boom, arm and bucket. It works on principle of hydraulic fluid with hydraulic cylinder and hydraulic motors. The Hydraulic excavator arm operation require coordinated movement of boom, arm and bucket. The important criteria for the design to be safe is that, the digging forces developed by actuators must be greater than that of the resistive forces offered by the surface to be excavated. The main objective of this paper is to perform design and analysis Excavator Arm for the calculated Force. The CATIA software is used for making the 3D model of the excavator arm linkage. By using ANSYS workbench software analysis of the excavator arm is done at existing digging force and lifting force. Excavator bucket is very crucial element of hydraulic excavator. The whole loads of excavated materials have been carried out by this element. As the present mechanism used in excavator arm is subjected to deformation and bending stresses during lifting and digging operation respectively, because of which failure occurs frequently at the bucket end of the arm. Keywords: Excavator arm, Digging force, CATIA, ANSYS 16.0.

Assembly-Oriented Finite-Time Coordinated Control of Underactuated Dual Rotary Cranes for Payload Position and Attitude Regulation

With strong load capacity and high maneuverability of payload attitude regulation, dual rotary cranes (DRCs) are widely applied for transportation and assembly tasks in infrastructure construction. For DRCs, to achieve safe and accurate control of the payload position and attitude, it is necessary to enhance the motion synchronization of two cranes, under the premise of controlling more state variables with fewer control inputs based on nonlinear coupling dynamics; moreover, the finite-time convergence of positioning errors is also expected to be guaranteed for high efficiency. To this end, this paper proposes an assembly-oriented finite-time coordinated controller <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any linearization to the nonlinear crane dynamics, which realizes accurate and stable regulation of the payload position and attitude through coordinated boom motions. To our knowledge, the proposed controller provides the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> closed-loop control solution to realize both horizontal and non-horizontal payload hoisting for DRCs based on practical assembly demands. Theoretically, through elaborate design of the synchronization error and coupling errors, the real-time information exchange between the two cranes is realized for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> time, which enhances the boom motion synchronization while suppressing payload swings. Furthermore, by introducing continuous terminal sliding mode surfaces with a multi-layer nested structure, the finite-time convergence of the boom positioning errors and the synchronization error is ensured with chattering reduction. Additionally, rigorous closed-loop stability analysis is provided based on Lyapunov techniques and Barbalat’s Lemma. Finally, the effectiveness and robustness of the proposed controller are verified by hardware experimental results. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This paper is motivated by the coordinated motion control problem of dual rotary cranes (DRCs), which aims to achieve safe and accurate control of the payload position and attitude oriented on practical assembly demands. At present, most control methods for DRCs only realize horizontal payload transportation, which not only ignores the requirements of payload attitude regulation in assembly tasks, but also lacks the guarantee for boom motion coordination and the finite-time convergence of state variables. To address these issues, based on the nonlinear crane dynamics <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any linearization, this paper proposes an assembly-oriented finite-time coordinated controller for DRCs, which achieves precise and stable regulation of the payload position and attitude through coordinated boom motions, and simultaneously enhances the system rapidity by ensuring the finite-time convergence of boom positioning errors. Furthermore, the detailed controller design and stability analysis process is provided, and the effectiveness of the proposed method is verified by hardware experiments. In the future research, we will try to apply the proposed method to practical operations of DRCs for complex assembly tasks of large heavy objects.

Real-time target point identification and automated log grasping by a forwarder, using a single stereo camera for both object detection and boom-tip control

The forest industry is constantly striving to increase productivity and cut costs, and many research and innovation projects are currently focusing on semi-automated or autonomous systems. A key element, with several possible solutions, is automated log grasping, where researchers and manufacturers are looking for efficient and sturdy ways to solve the task in real-time forwarding operations. This study presents a simple method for automated log grasping using only a single stereo camera for object detection (log and grapple) and a simple controller moving the boom, with feedback from the camera as boom-tip control. The accuracy, precision, and repeatability of the method was tested on a full-scale forwarder. Boom movements were examined from two different start positions in relation to the target position, with the log placed at three different angles. The overall log-grasping success was also evaluated. The tests were performed in a full-scale, real-time operation, without hand-eye calibration or other sensor data from the machine. The method was precise, with high repeatability, but the grasping point showed a minor systematic offset, depending on log angle. However, the deviation in accuracy was too small to affect the success rate. In practice, the most difficult log angles can be avoided by moving the machine slightly. The log grasping method may become part of an autonomous forwarding system or could provide operator support in semi-automated systems.

Влияние податливости гидропривода на динамическую нагруженность механизмов лесного манипулятора

The article analyzes the research into the dynamics of the hydraulic drive of technological machines and equipment. It has been established that insufficient attention has been paid to the issues of the influence of hydraulic drive compliance on the dynamic loading of individual mechanisms. The purpose of the work is to assess the effect of hydraulic drive compliance on the dynamic loading of forest manipulator mechanisms when improving the layout of hydraulic cylinders based on mathematical modeling. A mathematical model of the movement of the manipulator boom is presented, taking into account the forces of inertia and the flow rate of the working fluid. A model estimate of the dynamics of the hydraulic drive and the pressure of the working fluid was made when the boom of the forest manipulator is turned. The problem was solved as part of the work on a software package for studying the pressure jumps of the working fluid in hydraulic cylinders. The evaluation results showed that the optimal points of attachment of the hydraulic cylinder to the boom and to the rotary column depend on the compliance coefficient. In a computational experiment to determine the optimal layout of the hydraulic cylinder of the lifting mechanism of the manipulator boom, according to the criterion of minimizing the pressure surges of the working fluid, the optimal points of attachment of the hydraulic cylinder to the boom b1 = 0.9 m and to the rotary column OB = 0.7 m were obtained, and when taking into account the compliance coefficient were new optimal hydraulic cylinder attachment points were obtained: b1 = 1 m, OB = 0.85 m. To interpret the model and clarify the effect of hydraulic drive compliance on the dynamic loading of forest manipulator mechanisms, it is necessary to conduct bench tests.

Lyapunov-Based Model Predictive Control for Shipboard Boom Cranes Under Input Saturation

A Lyapunov-based model predictive control (MPC) scheme is firstly developed for shipboard boom cranes with ship rolling, while considering optimization and input saturation. By integrating the ship rolling into original state variables, the shipboard boom crane model is transformed to facilitate the successive controller design. A Lyapunov-based MPC framework is then constructed for the new dynamical model, while respecting actuator capability. To ensure the recursive feasibility and stability of the established framework, a contractive constraint with a bounded energy-based controller is further introduced, for which the bounds are intrinsical with the utilization of the arctan function. Stability analysis for the bounded controller is also discussed based on Lyapunov theory and LaSalle&#x2019;s invariance principle. Compared with the bounded controller, optimization is taken into account by the Lyapunov-based MPC. Suboptimal solutions are also accepted to ease the computational burden. Moreover, the conservation existing in the bounded controller can be entirely circumvented by the Lyapunov-based MPC, so the capacity of actuators can be fully exploited while obeying the input saturation. Finally, numerical simulations are elaborately devised and implemented to show the effectiveness of the bounded controller and superiority of the Lyapunov-based MPC controller. <i>Note to Practitioners</i>&#x2014;Shipboard crane is an important industrial equipment in ocean transportation and offshore engineering. Cranes are installed on ship deck, so the movements of ship, such as rolling, and pitching, may introduce difficulties, inefficiency, and unsafety to the manual operation. The conditions mentioned above motivate the study of automation control for shipboard cranes. A Lyapunov-based model predictive control (MPC) framework is constructed in this paper. Based on this framework, the payload can be conveyed to the desired location accurately and eliminate the swing quickly. Simultaneously, optimization is considered, thus, better control performance can be achieved by consuming less energy. Moreover, the physical limits of the actuators can be satisfied all the time. The present research only considers 3 degrees of freedom (DOF) shipboard boom cranes, for which the slew movement of boom and payload tangential swing are not involved. In the future research, the 5-DOF shipboard boom cranes will be studied to promote the application of the method proposed in this paper.

Optimal Collaborative Motion Planning of Dual Boom Cranes for Transporting Payloads to Desired Positions and Attitudes

With the increasing demands of high-precision hoisting, a growing number of to-be-hoisted large-scale heavy payloads <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">not only</i> need accurate positioning transportation, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">but also</i> require specific attitude adjustments, which mostly relies on dual boom cranes (DBCs) in practice due to their powerful capability. To achieve effective non-horizontal payload hoisting, the two booms of DBCs should reach different positions while guaranteeing safety, high efficiency, and energy conservation, which makes coordinated boom motions particularly difficult. To this end, an optimal collaborative motion planning method for DBCs is proposed in this paper <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any linearization, which realizes fast, accurate, and energy-saving payload transportation with swing suppression. To the best of our knowledge, the proposed method provides the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> solution for DBCs to transport payloads to the desired non-horizontal attitudes, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">simultaneously</i> achieves comprehensive optimization of multiple performance indicators, including transportation time, energy consumption, etc., on the premise of safety. On the theoretical side, novel collaborative auxiliary signal construction and parametric design guarantee the coordination of boom motions, and the solving process of optimal trajectories is simplified through elaborate convex optimization problem reformulation and analysis. At last, the effectiveness and adaptability of the proposed method are verified by hardware experiments under different working requirements.

Simulation and experiment on obstacle avoidance control of concrete pump truck boom based on improved danger field and gradient projection method

Aiming at the shortcomings of the traditional robot obstacle avoidance algorithm applied directly to the leader–follower task transformation of concrete pump truck boom, an algorithm combined with improved danger field and improved gradient projection method for obstacle avoidance control of the boom is proposed. In the method, a joint limit avoidance function is used to avoid the angle overrun of the boom joints. And the danger field expression is modified to improve its engineering suitability. Moreover, a smoothing adjustment factor is introduced to improve the smoothness of the leader–follower task transformation of the boom. The influence of key control parameters on the safety and accuracy of boom movement is discussed through the simulation, and the reasonable ranges of the parameters are given. Furthermore, experiments are carried out to verify the effectiveness of the algorithm. The method provides a solution for obstacle avoidance control of construction machinery with multijoint series boom.

Research on Dynamic Performance of Independent Metering Valves Controlling Concrete-Placing Booms Based on Fuzzy-LADRC Controller

Motion control of truck-mounted concrete pump booms is an important part of concrete construction work. The quality of the boom movement will affect the efficiency and safety of construction operations. To make the boom move quickly and steadily, its hydraulic control system needs to be improved. In this article, we firstly combine independent metering control (IMC) and active disturbance rejection control (ADRC). The hydraulic system that controls the boom is meliorated by replacing the traditional proportional directional spool valve with four cartridge flow control valves to realize IMC. Meanwhile, a fuzzy linear ADRC algorithm is proposed for a new IMC hydraulic system where ADRC is linearized and combined with fuzzy logic to achieve better motion control performance of boom sections. According to the results of experiments conducted using all six boom sections, compared with the PID control algorithm, the fuzzy linear active disturbance rejection control (FLADRC) proposed in this article can improve the stability and rapidity of valves controlled by hydraulic cylinders by 10.0% to 66.7% in different working conditions.

Experimental Investigations of Partially Valve-, Partially Displacement-Controlled Electrified Telehandler Implements

The next generation of electrified heavy-duty mobile machines (HDMMs) requires more efficient hydraulic systems—to save energy and to compensate for the limited capacities of available mobile electric energy sources. This study is experimentally demonstrating the functionality, dynamic performance, and efficiency of such a more efficient but also cost-effective system. The demonstrator is a conventional nine-tonne telehandler that has been transformed by replacing the diesel engine with an electric machine (EM) and changing the boom function from valve to displacement control. Since the system control and the resulting dynamics are not trivial, key aspects of it are explained in the paper. With the functional system, achievable consumption reductions could be obtained by measuring five different representative work cycles repeatedly and comparing the average consumption values to the consumption of a purely valve-controlled but also electrified reference version. In four of five cycles, an average reduction of 21–31% was achieved, which confirms the simulation results from previous studies and the effectiveness of the concept. However, one cycle—characterized by serial movements and longer breaks of the boom movement—showed a reduction of only 3% and that the effectiveness of the concept can also be lower in certain cases that depend mainly on the operator.

Optimization of manipulator's motion mode on elastic base according to the criteria of the minimum central square value of drive torque

The results of studies of optimizing the mode of movement of the manipulator boom, mounted on an elastic base with a known stiffness the paper presents. The purpose of this scientific research is to reduce the oscillations of the manipulator turnout system, which will increase the overall efficiency of the manipulator, durability and reliability of the metal structure elements. The implementation of this goal have achieved by applying a controlled mode of operation of the drive with dynamic balancing of the drive mechanism. Using the Lagrange equation of the second kind, the equation of motion of the manipulator boom was compile and the expression for the generalized driving moment of the drive mechanism of the manipulator boom system was determined. This study considers only the angular displacement of the manipulator boom. The unbalanced drive driving moment of the manipulator boom had estimated by the component of the total inertial moment of the moving mass of the boom and load and the static load from the mass of the boom and load on the drive mechanism. The elastic base of the manipulator was present in the form of a linear spring with a given coefficient of elasticity. Since the main external factor of oscillation, perturbation in the metal structure of the manipulator is the driving moment of the drive, so we used the target optimization function, which estimates the root mean square value of the driving moment of the drive mechanism. The main criterion for optimizing the mode of motion was present in the form of an integral functional, and the search for its minimum value is carried out using the methods of calculus of variations.&#x0D; The results of this work can used by the drive control system at the design stage of the manipulator and during its operation. The dynamics of oscillations of such structural elements of boom systems of cranes is also estimated. The implementation of the obtained optimal modes of movement can be carried out using a hydraulic drive.

Collaborative Antiswing Hoisting Control for Dual Rotary Cranes With Motion Constraints

With large load capacity and flexible payload attitude adjustment capability, dual rotary cranes (DRCs) play crucial roles in infrastructure construction with heavy hoisting demands. However, as a kind of collaborative control systems, DRCs have complex collaborative constraints, and large-scale payloads cannot be simply regarded as mass points; moreover, due to the lack of control inputs, some state variables can only be indirectly controlled through complicated nonlinear coupling relationships, which make the controller design and corresponding analysis particularly difficult. Additionally, in practical applications of DRCs, many factors (such as boom motion overshoots, inaccurate gravity (torque) compensation, etc.) are prone to result in unexpected steady errors, large payload swing, and boom collisions, which may result in inaccurate assembly, and even lead to safety accidents. To this end, this article proposes an adaptive nonlinear proportional-integral-derivative-like collaborative control method for DRCs, which can realize accurate and efficient antiswing hoisting. To our knowledge, this is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first</i> controller embedded with integral terms <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">without</i> any linearization during the controller design or stability analysis, which can effectively reduce steady errors, and keep boom motions within safety ranges by adaptive gravity (torque) compensation and elaborately designed constraint terms. Theoretically, the closed-loop stability and convergence are proven through strict mathematical analysis by using Lyapunov techniques and LaSalle’s invariance theorem. Finally, several groups of hardware experimental results are presented for effectiveness and robustness verification.

Proof of concept study for in-situ burn application using conventional containment booms – Design of Burning Tongue

In situ burning (ISB) hasn’t been widely used for offshore oil spill response for various reasons. We present a feasibility study for a new ISB method – the Burning Tongue (BT) concept. We conducted scaled experiments in the Ohmsett wave tank to demonstrate its feasibility. We produced a 35-m long “tongue” of burnable oil (average oil thickness 4.2 mm – above the thickness needed for ISB) by towing a conventional boom (with a 12″ (0.3 m) deep skirt) partially filled with crude oil and then released the oil through a 6″ (0.15 m) wide opening at the apex. We found that the boom movement produced a convergence zone just downstream that kept released oil thick and also pulled oil that entrained under the boom skirt into the thick “tongue” of oil. CFD modeling was performed to explain the flow hydrodynamics and the formation of the convergence zone, which indicates the phenomenon is universal. We used small harbor boom only partially filled with oil for this study and believe that a full-scale marine boom filled with oil would achieve an even thicker “burning tongue.” The BT concept could make ISB more widely used for oil spill response in offshore areas.

Analysis of Dynamic Behavior of Spray Boom under Step Excitation

Dynamic behavior modeling and parameter optimization of the spray boom based on multi-body vibration were developed to study the influence of the boom sprayer’s motion in a complex working environment on the dynamic behavior of the spray boom. First, a geometric continuous model of spray boom vibration was established considering the influence of the boom sprayer body and boom suspension. Then, the dynamic behavior of the spray boom under step excitation was studied on a SWAN3WP-500 self-propelled boom spray experimental platform. The time-domain response of spray boom movement was characterized using a multi-channel dynamic test system, and the simulation results of the geometric continuous model were verified. The correlation coefficient between the simulated and experimental results is 0.917, and the maximum relative error is 12.16%. Finally, the effects of boom sprayer speed, spray boom length, and spray boom cross-section shape on spray boom vibration were analyzed through the geometric continuous model. (1) The amplitude and period of vibration at the extremity of the spray boom gradually decline with a rise in boom sprayer speed. (2) The amplitude and period of vibration at the extremity of the spray boom gradually increase when the unilateral spray boom is shorter than 5 m but slowly decrease when it is longer than 5 m. To avoid excessive static elastic deformation of the spray boom, the length of the unilateral spray boom should be controlled within 6 m. (3) A reasonable cross-sectional shape can improve the spray boom vibration, and the spray boom with a type B cross-section can better inhibit the vertical vibration of the spray boom under the same cross-sectional area.

Fusion of 4D Point Clouds From a 2D Profilometer and a 3D Lidar on an Excavator

The research aimed to integrate a solid-state 2D-pulsed time-of-flight (TOF) flash Lidar profilometer and a mechanically scanning 3D Lidar in order to monitor the 4D (3D + signal intensity) environment at a construction site from an excavator. Utilizing the excavator's GNSS and IMU sensor data enables to fuse the profilometer and 3D Lidar point clouds into the same coordinate system. Both measurement devices have quite a narrow field of view, but the overall viewing angle is expanded due to the movement of the excavator boom and rotation of the excavator cab. The major advantage of this combination method is that the profilometer provides centimetre-accurate details of the worksite within a range of approximately 1-10 m, while the commercial 3D Lidar scanner provides a larger scale (roughly 1-64 m) description of the worksite with an accuracy of ±6 cm. Additionally, the profilometer's intensity information can be used to identify people on the basis of varying reflective vest patterns. The experimental results indicate that our combination system can accurately build a quality 4D point cloud map better than either individual device on its own. The combination of Lidars could prove to be an interesting tool, with the potential to improve construction site management processes.

Opresión y resistencia en Miami: un acercamiento interseccional a través de la crónica cubana del New Latino Boom

Este ensayo explora las experiencias de opresión de las minorías étnicas en la Miami de los 80 y principios de los 90, así como las herramientas de resistencia a las mismas. Lo propio se realiza a través de un análisis interseccional intracategorial, es decir, del estudio de un grupo social concreto a través de experiencias individuales, teniendo en cuenta las conexiones entre categorías sociales (raza, género, clase social, etc.) y sus dimensiones (negro, mujer, clase media, etc.). Las fuentes primarias analizadas son las crónicas Body Wrap City (2016) de Grettel J. Singer y Memorias del Downtown (2016) de Luis de la Paz, ambos escritores cubanos pertenecientes al New Latino Boom. Los resultados presentan una realidad diversa, compleja y conflictiva marcada por la segregación y la discriminación entre minorías, donde la no interpretación de las realidades sociales desde enfoques interseccionales se presenta como un factor explicativo fundamental en la persistencia de las opresiones y los privilegios.

Experimental studies of the motion modes of the main boom and jib of loader crane

In order to increase the productivity and reliability of a hydraulic-powered loader crane, according to the normative-technical documentation regulating the safe operation of multi-link cranes, it is allowed to combine movements with the simultaneous movement of several links of the boom system. As a result, the paper considers a technique for conducting experimental studies in the plane of changing the boom system of a loader crane with a load. Experimental studies were carried out under the condition of simultaneous angular movement of the main boom and jib. To carry out experimental studies, an experimental installation of a hydraulic-driven loader crane was designed and manufactured. Measuring and recording equipment has been selected and adjusted. In the framework of experimental studies of the dynamics of movement of the boom system of a loader crane with a load, a control system for drive mechanisms has been developed, which makes it possible to realize the optimal modes of movement of the links of the boom system. As a result, experimental studies were carried out under the condition of simultaneous movement of the main boom and jib with a load at the end of the boom system. A package of data on real and optimal modes of movement of the links of the boom system of the loader crane was received. The processed data are presented in graphical form and a comparative analysis with real and optimal modes of movement is carried out. The developed method of experimental research has made it possible to determine the effect of the simultaneous movement of the boom and jib on the oscillations of the load, and the effect of the oscillations of the load on the dynamic loads arising in the boom system and the drive mechanisms of the loader crane.

Роботоздатність рукавів стикування системи термостатування ракети «Циклон-4» в екстремальних умовах

This article contains the analysis of the performance of interface hoses for the thermal conditioning system of a Cyclone-4 space rocket in extreme operating conditions. thermal conditioning system interfaces with rubber hoses must ensure a tightness of a hose at a rocket’s inlet with easy detachment, involving little to no force impact on the rocket during its start on its one end, and rigid connection with a pipeline of the thermal conditioning system ground part, ensuring the hose tightness and retaining after the launch of a rocket on its other end, under any abnormal operating conditions. As it is shown in the article, this goal is attained by inducing contact stresses on surfaces adjacent to the rubber hose, originating from a designed radial compressive stress and coarseness of the contact surfaces. At the same time, the detachable part is subjected to lower radial deformation than the fixed one. To prevent any operating pressure excess in the thermal conditioning system ground part that might lead to extreme operating conditions, the retaining and release mechanism has been designed in such a way that under the operating conditions of pressing the hose’s sealing part, a proper stable gap would be ensured between the external radius of the rocket’s inlet protrusion and the internal diameter of its rim, so that the hose's sealing part could act as a safety valve. In such case, upon an excess of the permissible operating pressure, the hose’s sealing part would protrude through the gap mentioned by expanding and getting thinner, thus leading to detachment of the hose from the rocket’s inlet in the course of its launch or launch abort. In case of the retaining and release mechanism’s pin failure, the thermal conditioning system interface design would ensure the guaranteed failsafe detachment of the thermal conditioning system hoses with minimum stress on both the rocket and the thermal conditioning system ground part. As in a case of a critical pressure excess in the thermal conditioning system, the hose’s sealing part would act as a safety valve thanks to its axial extension under stresses from the rocket’s launch, the transportation and erection installation’s boom movement, or both factors at the same time. The hose’s sealing part, having a smaller cross-section in the area of the groove for retaining and release mechanism, would shrink in thickness during stretching and expand through the gap between the outer diameter of the rocket’s inlet protrusion and the internal diameter of the retaining and release mechanism’s rim, which was proven experimentally on a special test bench simulating operating conditions close to the real ones. At the same time, the stresses of the hose detachment from the rocket’s inlet are less than the hose’s rupture stresses in the axial direction by several orders during stretching.

Sensor-Fault-Tolerant Operation for the Independent Metering Control System

Due to the complex control software based on electronic sensors, an independent metering control system (IMCS) has a higher risk of failures than a traditional electrohydraulic system. Considering the tough requirements of safety and reliability in mobile applications, this article innovatively proposes an active sensor-fault-tolerant controller (SFTC) for IMCSs. It is a model-free controller without any additional sensors. All the faults of the inlet, outlet, and supply pressure sensors are tolerated via analytical redundancy rather than hardware redundancy. The core of the analytical redundancy is to reconfigure the control loops of the normal controller by utilizing the cross-couplings among multivariables. To guarantee the switching stability from the normal controller to the SFTC, in this article, a bumpless transfer strategy based on latent tracking is designed, such that the abrupt output jump of the SFTC is suppressed and a smooth switching is obtained when the fault occurs. The feasibility of the SFTC system was evaluated by implementing the system on the two-ton excavator. The experimental results of boom motions verify the effectiveness of the controller under abrupt and random sensor faults.

Aggregated Hierarchical Sliding Mode Control for Vibration Suppression of an Excavator on an Elastic Foundation

Crawler excavators are important, utilitarian machines in construction industries. Special features of the chain and chassis allow them to operate and move on unstable ground. The shock motions of the links, which coincide with the changes of the forces impacting the foundation, create vibrations within the entire system. The highest level of vibrations appears when the boom moves, as it holds the robotic excavator's entire actuator with large mass and moment of inertia. These undesired fluctuations cause system instability, driver discomfort, reduced operating efficiency, and increased energy consumption. In this study, a hierarchical sliding mode control focusing on boom movement is designed based on the system dynamic model. This controller allows the boom to move precisely with a slight fluctuation angle of the main body, even while the other links are moving using a parameter estimator. Maintaining stable boom movements significantly simplifies arm and bucket control. The effectiveness of the entire work is investigated by numerical simulation and implementation results on a small-scale hydraulic excavator.