Internal Force Control Research Articles

Study on internal force optimization and control of a Levy cable dome

This study introduces active control into a Levy cable dome structure, designing and fabricating a model with active struts and length-adjustable cable. The research investigates the structure's capacity for internal force optimization and control under various load conditions through experiments and simulations. Initially, internal forces are optimized using the intelligent algorithms, from which the optimal actuation plans are determined through comparison. Experiments verify the feasibility and the correctness of these plans. Results show that, after assembly and tensioning, the prestress distribution of the refined test model aligns closely with theoretical values, with a maximum error of only 5.06%. Under symmetric and asymmetric overload conditions, average internal force reductions from experiments and simulations are about 40.00% and 50.00%, respectively. However, a notable increase in total actuation lengths is observed in asymmetric overload conditions compared to symmetrical one, highlighting the necessity for higher actuation quantity under asymmetric loads to achieve equivalent internal force optimization and control.

Adaptive Fuzzy Integral Sliding Mode Cooperative Control Based on Time-Delay Estimation for Free-Floating Close-Chain Manipulators.

Space manipulators are expected to perform more challenging missions in on-orbit service (OOS) systems, but there are some unique characteristics that are not found on ground-based robots, such as dynamic coupling between space bases and manipulators, limited fuel supply, and working with unfixed bases. This paper focuses on trajectory-tracking control and internal force control for free-floating close-chain manipulators. First, the kinematics and dynamics of free-floating close-chain manipulators are given using the momentum conservation and spatial operator algebra (SOA) methodologies, respectively. Furthermore, an adaptive fuzzy integral sliding mode controller (AFISMC) based on time delay estimation (TDE) was designed for trajectory-tracking control, and a proportional-integral (PI) control strategy was adopted for internal force control. The global asymptotic stability of the proposed controller was proven by using the Lyapunov methodology. Three cases were conducted to verify the efficiency of the controller by using numerical simulations on two six-link manipulators with a free-floating base. The controller presents the desired tracking capability.

Concept of combined strain-stress state control of long span structures

Purpose: Argumentation of necessity of special protective system design to protect structures in seismic zones and remote areas from specific loads. Such protective system combines seismic isolation and internal force control systems.Research findings: Restrictions of long-span structures construction are reviewed. Such restrictions are caused by building conditions embodied in National Building Codes and Standards. Combined and separate use of seismic isolation and internal force control systems is a critical specific load protection. Present inventions and experience in the field of seismic isolation and internal force control systems are reviewed.Value: The article determines problems of protective system design based on the control for combined strain-stress state.

Locomotion as manipulation with ReachBot.

Caves and lava tubes on the Moon and Mars are sites of geological and astrobiological interest but consist of terrain that is inaccessible with traditional robot locomotion. To support the exploration of these sites, we present ReachBot, a robot that uses extendable booms as appendages to manipulate itself with respect to irregular rock surfaces. The booms terminate in grippers equipped with microspines and provide ReachBot with a large workspace, allowing it to achieve force closure in enclosed spaces, such as the walls of a lava tube. To propel ReachBot, we present a contact-before-motion planner for nongaited legged locomotion that uses internal force control, similar to a multifingered hand, to keep its long, slender booms in tension. Motion planning also depends on finding and executing secure grips on rock features. We used a Monte Carlo simulation to inform gripper design and predict grasp strength and variability. In addition, we used a two-step perception system to identify possible grasp locations. To validate our approach and mechanisms under realistic conditions, we deployed a single ReachBot arm and gripper in a lava tube in the Mojave Desert. The field test confirmed that ReachBot will find many targets for secure grasps with the proposed kinematic design.

Member control efficiency and shape control capability of a loaded cable dome

In this paper, the control efficiency of the members and shape control ability of a loaded adaptive cable dome consisting of 16 cables and 4 struts are investigated. The structure uses specially designed cables and electric telescopic struts integrated with an actuation control system, and all members of the structure are length-adjustable. Initially, an intelligent algorithm is employed to solve the structural shape optimization control model, thereby determining the optimal adjustment amounts. Subsequently, active adjustment and active control tests are conducted to evaluate the control efficiency of the members and the shape control capabilities of the cable dome. The results indicate that the ridge and diagonal cables exhibit the most effective control, followed by the upper and lower hoop cables, while the struts show the lowest control efficiency, primarily influencing the displacement of the joints at their two ends. Moreover, the cables' internal force control efficiency is 3–4 times higher than that of the struts. The ridge and diagonal cables' internal force and displacement control efficiency is about 1.5 times higher than that of the upper and lower hoop cables. The loaded test model exhibits the ability to restore the vertical coordinates of upper joints to their target coordinates, while reducing the internal forces of the components by at least 15 %, and the shape control capability of the structure can be enhanced by incorporating various types of active units. The measured values correlate well with the simulation results, validating the accuracy of the simulations.

Model-Based Adaptive Collaboration of Multi-Terminal Internal Force Tracking

This paper proposes a multi-terminal adaptive collaborative operation method for solving the problem of unstable internal force tracking in the clamping and handling of unknown objects by multi-terminal robots. In the proposed method, the internal command force changes the complex internal force control problem into an internal force tracking problem from multi-slave to master. Moreover, we develop an algorithm for multi-slave setups to estimate the object stiffness and motion uncertainty in the direction of the internal command force according to Lyapunov theory. Finally, the impedance control generates a reference trajectory for the multi-slave to maintain the desired internal force and track the master’s motion. Several experiments were conducted on a self-made robot. The experimental results show that the oscillation amplitude of each slave end is less than 1 mm and the directional oscillation amplitude is less than 1 degree during the tracking of the desired commanded internal force. For objects with a low stiffness, the error of the commanded internal force is less than 1 N (6%) per slave. The error in tracking the commanded internal force for objects with a high stiffness is less than 2 N (8%). The results prove the feasibility and effectiveness of the proposed method.

An adaptive impedance control for dual-arm manipulators incorporated with the virtual decomposition control

The interaction force control problem for the object manipulated by the dual-arm manipulator with the unknown environment is addressed in this paper. An adaptive dual-loop impedance control scheme is designed to meet the three control targets, including the trajectory tracking control of the object, the internal force control of the object with the two arms, and the interaction force control of the object with the unknown environment. Firstly, an adaptive variable impedance control method is proposed in the outer loop to copy with the unknown stiffness and position of the environment. Secondly, an impedance control scheme based on the internal force is designed in the inner loop to plan the internal force and the modified position supplied with the outer-loop control. Thirdly, to realize the reference trajectory supplied with the inner-loop control, the virtual decomposition control (VDC) method is incorporated, which is a recursive adaptive control progress, so that the unknown dynamics of the manipulators is acceptable and the computation complexity is also very low to satisfy the real-time control requirement. The stability verifications of the inner-loop impedance control and the VDC method are given based on the Lyapunov method, and the stability analysis of the outer-loop impedance control is obtained using the Routh criterion. Finally, a plane dual-arm robotic manipulator with three degrees of freedom is used to verify the effectiveness of the proposed control scheme.

Explaining Types of Military Defections during Major Anti-authoritarian Protests

Abstract Military defections during major anti-authoritarian protests have received significant attention. Yet instances of military disloyalty, commonly termed defections, often actually involve different parts of the military organization. Middle- and high-ranking officers may unite to defect, or they may fragment, with some defecting and others remaining loyal. In this article, I draw on the existing scholarship’s insights to argue that a dictator that uses control of internal security forces marginalizes all officers and increases the likelihood of united defections, whereas a dictator that uses military politicization marginalizes only some officers and increases the likelihood of fragmented defections. I assess and find support for these relationships statistically, using data on types of defections across a large N sample of all major anti-authoritarian protests from 1960 to 2011. I also illustrate the relationships using two brief comparative cases, Chile (1988) and El Salvador (1979).

Prescribed time tracking control without velocity measurement for dual-arm robots

This paper studies the prescribed time control of dual-arm robots without velocity measurement. Firstly, according to the position/force constraint relationship between the dual arms and the grasped object, the comprehensive dynamic model is established with the object position in Cartesian space, then the system motion model independent of the internal force is obtained. Secondly, a settling-time regulator related to convergence time and tracking accuracy is constructed, then the prescribed time tracking problem boils down to the output error constraint problem. Furthermore, a new constraint transformation function is introduced to change the output error constraints to ensure the boundedness of the new error variables. Finally, combined with the velocity observer and backstepping technique, the position controller and hybrid position/internal force controller are designed respectively. The remarkable features include: (1) Both position control and internal force control are considered, which is helpful to realize the coordinated movement of the dual-arm system and the stable grasping of the object; (2) There is no requirement to measure the velocity of the object, which avoids the expensive velocity sensor and its interference; (3) Compared with the existing control methods, the convergence time and tracking accuracy in the position control can be preset manually.

Study on Key Technology of Assembling Installation of Long-Span Composite Girder Cable-Stayed Bridge

PDF HTML XML Export Cite reminder Study on Key Technology of Assembling Installation of Long-Span Composite Girder Cable-Stayed Bridge DOI: 10.59238/j.pt.2023.01.007 Author: Affiliation: (Sichuan Highway Planning, Survey, Design and Research Institute Ltd. , Chengdu 610041, China) Clc Number: Fund Project: Article | Figures | Metrics | Reference | Related | Cited by | Materials | Comments Abstract:The Nanxi (Xianyuan) Yangtze River Bridge in Yibin is a composite beam cable-stayed bridge with twin towers and double cable planes and a main span of 572 m. The superstructure is erected by the assembly method. In order to ensure the precise installation and control of internal forces for steel girders and bridge deck slabs of composite beams while also considering the construction efficiency of composite beams, a control method for the installation and erection of the superstructure has been proposed. This method is based on optimizing the internal force and geometric states of segments throughout the entire process, achieved by establishing finite element calculation models for both the full bridge and segmented sections and combining these with comparative studies of on-site monitoring data. With the installation stress and precision of composite beams properly controlled, construction efficiency has been enhanced through the optimization of the pouring process for wet joints between steel girders and concrete bridge deck slabs, as well as the tensioning process for stay cables. The equivalent tension method is applied to the tension process of the stay cable, thus ensuring the uniformity of the cable force of the steel strand. The relevant conclusions are applicable to the same type of composite girder cable-stayed bridge erection construction. Reference Related Cited by

Coordinated hierarchical control of space robotic safe manipulation with load sharing

This research explores an integrated control technique for a dual-armed space robot that has captured a tumbling satellite. The compliant behavior for safe manipulation in-orbit is achieved using the external impedance at the target level. First, considering the control moment constraints imposed on the target body, a fast detumbling strategy is proposed using dynamic movement primitives method with normalized time. Following the capturing of a non-cooperative target, a coordinated hierarchical control scheme is developed with multi-arm space robotic dynamics modeling to direct the space robot in carrying out the pre-planned detumbling strategy. The proposed control scheme incorporates external impedance, internal force control and load sharing. Finally, numerical simulation with a sample case of two collaborative seven-degree-of-freedom space robotic arms capturing a tumbling target satellite verifies the viability and efficacy of the presented control strategy.

Tactile Feedback Enabling In-Hand Pivoting and Internal Force Control for Dual-Arm Cooperative Object Carrying

Collaborative robots (cobots) are machines designed to work safely alongside people in human-centric environments. Providing cobots with the ability to quickly infer the inertial parameters of manipulated objects will improve their flexibility and enable greater usage in manufacturing and other areas. To ensure safety, cobots are subject to kinematic limits that result in low signal-to-noise ratios (SNR) for velocity, acceleration, and force-torque data. This renders existing inertial parameter identification algorithms prohibitively slow and inaccurate. Motivated by the desire for faster model acquisition, we investigate the use of an approximation of rigid body dynamics to improve the SNR. Additionally, we introduce a mass discretization method that can make use of shape information to quickly identify plausible inertial parameters for a manipulated object. We present extensive simulation studies and real-world experiments demonstrating that our approach complements existing inertial parameter identification methods by specifically targeting the typical cobot operating regime.

Self-Control, Parental Monitoring, and Adolescent Problematic Mobile Phone Use: Testing the Interactive Effect and Its Gender Differences.

Previous studies have revealed that self-control was one of the critical factors of adolescent problematic mobile phone use. Few studies, however, have explored the interaction of internal control force (i.e., self-control) and external control force such as parental monitoring. The present study tested the interactive effect of self-control and parental monitoring on adolescent problematic mobile phone use and its gender differences. A sample of 926 adolescents completed our anonymous self-report survey. Results showed that self-control and parental monitoring negatively predicted problematic mobile phone use, while gender positively predicted problematic mobile phone use. Self-control and parental monitoring had an interactive effect on problematic mobile phone use, with the effect of self-control on problematic mobile phone use being stronger for adolescents with low levels of parental monitoring than for those with high levels of parental monitoring. Self-control and gender had an interactive effect on problematic mobile phone use, with the effect of self-control on adolescent problematic mobile phone use being stronger in girls than in boys. Moreover, there were significant gender differences in the interaction of self-control and parental monitoring, in that the interactive effect of self-control and parental monitoring on problematic mobile phone use was more potent in girls than in boys. The findings reveal how the internal control force (i.e., self-control) and external control force (i.e., parental monitoring) work together in explaining adolescent problematic mobile phone use and uncover the potential gender differences in exploring adolescent problematic mobile phone use from the individual-environment perspective. Limitations and implications are discussed.

Complementary Stability of Markovian Systems: Series Elastic Actuators and Human-Robot Interaction

Abstract This paper presents an extension of the complementary stability analysis for discrete-time Markovian systems applied in interaction control. The control strategy considers an internal loop force control for Series Elastic Actuators based on the Robust Regulator for Discrete-time Markov Jump Linear systems and extern loop impedance control to regulate the interaction between the human and robot. Two examples show the complementary stability analysis of the human-robot interaction system, where is regarded as different values of the virtual impedances, different levels for the robustness of the force control, uncertainties, and abrupt changes for human parameters. Simulation results show the capacity of control strategy to deal with active interaction models, where the Mean Square Stability guarantees safe for the user. Additionally, from results it is understood the transmissibility of impedance achieved is a consequence of the robust performance given by the force controller.

Time-varying Reliability Analysis of Long-span Continuous Rigid Frame bridge under Cantilever Construction Stage based on the Monitored Strain Data

Abstract: In general, the material properties, loads, resistance of the prestressed concrete continuous rigid frame bridge in different construction stages are time-varying. So, it is essential to monitor the internal force state when the bridge is in construction. Among them, how to assess the safety is one of the challenges. As the continuous monitoring over a long-term period can increase the reliability of the assessment, so, based on a large number of monitored strain data collected from the structural health monitoring system (SHMS) during construction, a calculation method of the punctiform time-varying reliability is proposed in this paper to evaluate the stress state of this type bridge in cantilever construction stage by using the basic reliability theory. At the same time, the optimal stress distribution function in the bridge mid-span base plate is determined when the bridge is closed. This method can provide basis and direction for the internal force control of this type bridge in construction process. So, it can reduce the bridge safety and quality accidents in construction stages.

Dual feedforward neural networks based synchronized sliding mode controller for cooperative manipulator system under variable load and uncertainties

The problem of simultaneous position and internal force control is discussed with cooperative manipulators system under variable load and dynamic uncertainties in this study. A position synchronized sliding mode controller is proposed in the presence of variable load, as well as modeling uncertainties, joint friction, and external disturbances. To deal with the complex situation brought by variable load, virtual synchronization coupled errors are introduced for internal force tracking control and joint synchronization in the meantime. Dual feedforward neural networks are adopted, where a radial basis function-neural network based dynamic compensator and a radial basis function-neural network based internal force estimator are established, respectively, so that precise dynamic knowledge and force measurement are out of demand through their cooperation. Together with simulation studies and analysis, the position and internal force errors are shown to converge asymptotically to zero. Using Lyapunov stability approach, the proposed controller is proven to be robust in face of variable external load and the aforementioned uncertainties.

Professional Self-efficacy and Job Satisfaction: The Mediator Role of Work Design

The purpose of this study is to investigate the mediating role of work design characteristics (task, knowledge, social, and contextual characteristics) in the relationship between professional self-efficacy and job satisfaction. Research has shown how motivational job design has positive consequences for individuals, increasing control and perception of internal forces (such as self-efficacy) and affects positively job satisfaction. However, little is known about how self-efficacy affects job satisfaction through job enrichment. In this study, 353 Chilean workers answered a self-reported survey. Regression analyses confirmed partially the hypotheses, showing a complete mediation of task and social characteristics of work design in the relationship between professional self-efficacy and job satisfaction. These results show how professionalself-efficacy relates to work design and highlight the importance of social and task characteristics to improve job satisfaction, contributing to a better understanding of how self-efficacy improves job satisfaction through work design.

Relative Impedance-Based Internal Force Control for Bimanual Robot Teleoperation With Varying Time Delay

For a bimanual robot teleoperation system, the internal forces affecting the common deformable manipulation object are determined by both robot arms' actions. F/T sensorless, uncertain dynamics, and varying time delays increase dramatically the control difficulty for system stability and transparency. To address these problems, an internal force control method based on relative impedance is proposed in this paper. First, we deduce the desired positions to decrease internal force tracking errors and abstract the internal force from the product of the relative distance and impedance. Second, two strategies are adopted for reducing internal force tracking errors and motion synchronization. One is designing an adaptive factor to switch authorities for position control and internal force control. The other is proposing a force estimating method to the coupled item of uncertain dynamics, disturbance, and internal forces. Different parts of the coupled item are divided and solved separately by nonlinear characters. An integral sliding surface based on the relative impedance item is designed to minimize the force tracking errors. Finally, the effectiveness of the method is verified by linear matrix inequalities based on Lyapunov-Krasovskii functional synthesis, and an experiment based on a physical robot system is implemented to validate the proposed method.

Study on motion analysis and force/position hydraulic control of a parallel cylinder transmission system of heavy-duty quadruped robot

In the article, a heavy-duty quadruped robot was designed. A parallel cylinder transmission scheme for the heavy load torque of the hip joint of heavy-duty hydraulic quadruped robot is proposed, the mathematical model of the parallel cylinder system is derived, the model characteristics of the parallel cylinder system are analyzed, the characteristics of internal force and joint control of parallel cylinders are considered, the force/position hybrid control of parallel cylinder is proposed to eliminate the internal forces and realize the requirement of joint control and the force/position control is decoupled by the design of the force and position signal. According to the characteristics of the servo cylinder force control model, the flow compensation and speed compensation are introduced, the minimum control synthesis controller is used to control the servo cylinder force and the proportional integral controller is applied to control the position of servo cylinder. The compound control strategy is analyzed on the table of parallel cylinder, and the experimental results show that the amplitude attenuation and phase lag of position and force are less than 10% and 18°, respectively, and the efficiency of the proposed control strategy is verified. The research results of this article will be widely used in many fields of robot control in the future.

Deployment and Shape Change of a Tensegrity Structure Using Path-Planning and Feedback Control

Tensegrity structures are pin-jointed assemblies of struts and cables that are held together in a stable state of stress. Shape control is a combination of control-commands with measurements to achieve a desired form. Applying shape control to a near-full-scale deployable tensegrity structure presents a rare opportunity to analytically and experimentally study and control the effects of large shape changes on a closely coupled multi-element system. Simulated cable-length changes provide an initial activation plan to reach an effective sequence for self-stress. Controlling internal forces is more sensitive than controlling movements through cable-length changes; internal force-control is thus a better objective than movement-control for small adjustments to the structure. The deployment of a tensegrity structure in previous work was carried out using predetermined commands. In this paper, two deployment methods and a method for self-stress are presented. The first method uses feedback cycles to increase speed of deployment compared with implementation of empirically predetermined control-commands. The second method consists of three parts starting with a path-planning algorithm that generates search trees at the initial point and the target point using a greedy algorithm to create a deployment trajectory. Collision and overstress avoidance for the deployment trajectory involve checks of boundaries defined by positions of struts and cables. Even actuator deployment followed by commands obtained from a search algorithm results in the successful connection of the structure at midspan. Once deployment at midspan is achieved by either method, a self-stress algorithm is implemented to correct the position and element forces in the structure to the design configuration prior to in-service loading. Modification of deployment control-commands using the feedback method (with twenty cycles) compared with empirically predetermined control-commands successfully provides a more efficient deployment trajectory prior to midspan connection with up to 50% reduction in deployment time. The path-planning method successfully enables deployment and connection at midspan with a further time reduction of 68% compared with the feedback method (with twenty cycles). The feedback control, the path-planning method and the soft-constraint algorithm successfully lead to efficient deployment and preparation for service loading. Advanced computing algorithms have potential to improve the efficiency of complex deployment.