Bilateral Control System Research Articles

Attack detection method for encrypted wave‐variable‐based bilateral control systems

AbstractThis study presents an energy‐based attack detection method involving an encrypted bilateral control system using wave variables. In the considered bilateral control system, the leader and follower receive the follower's force information and the leader's velocity information, respectively, through the wave variables. The considered attack model multiplies the wave variables by an attack parameter, which is possible due to the malleability of the encryption scheme. The bilateral control system will be destabilized if the attacker chooses a relatively large parameter value. This motivates in developing a passivity observer for each leader and follower side to compute the total energy and constructing an energy‐based detection method that can be incorporated into the encrypted bilateral control system and is summarized in the presented theorem. Furthermore, this study provides a specific design for reasonable threshold parameters concerning the control system energy. The theorem and the experimental validation confirm that the developed encrypted wave‐variable‐based bilateral control system with the proposed attack detector is secure and effective as a countermeasure against malleability‐based attacks.

Robust passivity-based nonlinear controller design for bilateral teleoperation system under variable time delay and variable load disturbance

Abstract This research focuses on implementing a robust passivity-based nonlinear control method for bilateral/teleoperation systems. The key challenge is addressing communication pathways between the master and slave, control delays, and load disturbances, which can lead to instability and reduced transparency. To tackle these issues, the proposed controller incorporates a second-order super-twisting sliding-mode observer to counteract communication and control delays. A sliding mode assist disturbance observer compensates for load torque variations. The approach aims to ensure stability and transparency by handling time-varying delays. The system model comprises two interconnected direct-drive motors, simulating robotic configurations without a physical robot. The nonlinear controller framework simplifies the complex bilateral control problem, significantly improving stability and transparency performance. Computer simulations with step and sinusoidal inputs demonstrate the effectiveness of the approach, providing a satisfactory level of accuracy and transparency between estimated and actual slave positions, even with varying delays and load variations. The research contributes to control engineering by offering a robust method to enhance bilateral system performance, ensuring stable and transparent communication between the master and slave, particularly suitable for real-time internet-based bilateral control systems.

Force-Symmetric Type Two-Channel Bilateral Control System Based on Higher-Order Disturbance Observer

Force-Symmetric Type Two-Channel Bilateral Control System Based on Higher-Order Disturbance Observer

Sensorless Force Estimator for Bilateral Control Systems Using Adaptive Sliding-Mode-Assisted Disturbance Observer

Superior transparency, which includes precise force feedback and position tracking, is the main objective of bilateral operating systems. Therefore, force information estimation or measurement plays a critical role in improving the transparency of bilateral operating systems. This paper proposes a bilateral control scheme combined with an adaptive sliding-mode-assisted disturbance observer (ASMADO) for bilateral operating systems. First, ASMADO, comprising an adaptive disturbance observer and adaptive sliding mode-assisted control law, is used as a force detector to estimate the time-varying force in bilateral control systems. The adaptive disturbance observer with a fixed-time convergent auxiliary dynamic variable is designed without the prior knowledge of the upper bound of the force information derivative, which drives the force estimation error into a small bounded set. Then, the adaptive sliding mode-assisted control law is used to eliminate the estimated residuals of the adaptive disturbance observer in the inner loop of the force estimator. Stability analysis proves that the proposed ASMADO is practical finite-time stable. Subsequently, a bilateral control scheme based on the proposed ASMADO is developed to further improve the system transparency with force feedback and position tracking. Finally, comparative experimental studies are conducted to verify the superior performance of the proposed bilateral controller based on ASMADO.

Modal Space Control of Bilateral System with Elasticity for Stable Contact Motion

Bilateral control realizes position synchronization and the “law of action and reaction” between two points. To advance applications of bilateral control, it is necessary to emphasize environmental adaptability, safety, and task execution. Accordingly, the bilateral system is required to consider contact with unknown environments and realize stable contact to avoid harm to the operator or the object. Thus, a bilateral control system using elastic manipulators is proposed in this paper. Moreover, the integration of mechanical and control designs for stable interaction with the operator and the environment is discussed. The proposed bilateral system with elasticity is modeled as a pair of two-mass resonant systems. Accordingly, a modal space control (MSC) is introduced with the aim of realizing the control goals, vibration suppression, and good operationality. Modal transformation independently configures the force and position controllers of each other in virtual common and differential spaces. MSC comprises reaction torque feedback loops in the modal space and modal space load-side disturbance observer (MLOB). MLOB compensates for load-side disturbance, including the interference between the common and the differential modes. It realizes disturbance suppression, decoupling control, and nominalization of parameters in the form suitable for each force and position control system.

Safe operation of scaling bilateral control system under application of excessive force by operator

Physical interaction between humans and robots in a remote environment can be realized safely with bilateral teleoperation. The acceleration-based scaling bilateral controller and the reaction force estimator implemented with the disturbance observer facilitate robust control and vivid touch sensation between different structures. This paper introduces a replica-side security enhancement method when the operator applies excessive force on the master during scaling bilateral motion. Initially, the system follows four-channel acceleration-based scaling bilateral control. It switches to the master side virtual impedance controller and replica side force controller as the bearable force limit is reached on the replica. As a result, the operator-applied excessive force is not transmitted to the remote end, and the master maneuvers freely following the operator's intention. This method supports the operator's freedom while protecting the replica object. This study derives the value of virtual impedance aiming at high reproducibility. As a result, the operator receives replica side object impedance throughout the operation even when controllers are switched. This study analyzes the stability considering pole placement with system parameter variations. Experiments verified the proposed method. The results demonstrate that the proposed method ensures the safety of remote objects while the operator freely applies excessive force. The operator was able to successfully sense object impedance irrespective of whether the system followed scaling bilateral control or constrained scaling motion control.

Dynamics of a guanaco–sheep competitive system with unilateral and bilateral control

In this paper, based on a guanaco–sheep competitive system, we develop and analyze mathematical models with unilateral and bilateral control for the management of overgrazing. We first analyze the dynamics of the uncontrolled system. It then follows the analysis of the system with impulsive control by differential equation geometry theory. We mainly prove the existence and stability of order-1 periodic solution for unilateral control system and order-2 periodic solution for bilateral control system. Some numerical simulations including the bifurcation diagrams of periodic solution are carried out, which not only verify the validity of the theoretical results, but also reveal some special dynamic phenomena, such as the appearance of higher-order periodic solutions and the existence of parameter intervals with the order change of periodic solution. Comparing the unilateral and bilateral control strategy, we encourage bilateral control rather than unilateral control for the management of sheep species.

Bilateral control system of the space robot with large delays

The main obstacle of the construction of efficient remote-control systems for space robots is a significant delay in transmissions of control signals to robots from the earth-based control center and receiving feedback signals. This significantly complicates the solution of control problem, especially if robot’s manipulators move objects that have mechanical constraints. Our work describes a method for bilateral control of a space robot with large delays. The uniqueness of this method lies in the special structure of the control algorithm. Bilateral control implies force feedback necessary for the interaction of a space robot with objects that have holonomic connections. We present a new mathematical model of the elements of the bilateral control system and their computer implementation using specific examples.

Improved Haptic Transparency of Bilateral Control Using Torque-Measured Magnetic Coupling

The integrity and transparency of a haptic feedback in a bilateral control is crucial for precise and accurate operators’ sensation during human–machine interactions. Conventional master and slave bilateral control systems are often subject to unknown or unwanted disturbances and dynamics in the actuators and powertrain linkages that hamper the haptic feedback integrity and transparency. Force sensor torque sensing and feedback control are required to mitigate these effects. In contrast to the conventional approach of introducing torque sensing using a mechanical spring, this paper introduces a magnetic coupling as a torque sensor to detect reaction torque between the human input and the master actuator. Disturbance observer-based torque feedback control is designed to suppress the disturbances and tailor the haptic transparency dynamics. Experimental results on a virtual reality interaction system, which involves the steering wheel bilateral control in a cyber-physical driving simulator system, demonstrate the feasibility and effectiveness of the proposed method with improved haptic integrity and transparency.

Neurobehavioral assessment of force feedback simulation in industrial robotic teleoperation

Telerobotic operation, i.e., a human operator to manipulate remote robotic systems at a distance, has started to gain its popularity in the construction industry. It is expected to help tackle operational challenges in dynamic construction workplaces. The success of telerobotic operation builds on the effective design of the human-robot interface to provide human operators with necessary senses about the remote workplaces, involving multimodal sensory cues, such as visual, audio and haptic feedback. Especially the force feedback design in telerobotic control interface is of central interest and is becoming the main feature of the bilateral control system for teleoperation, as it helps provide feedback about heavy physical interactions and processes in typical construction operations. Nonetheless, how force feedback simulation solutions affect the human operator's perceptional and behavioral reactions is less understood. This paper investigates the neurobehavioral performance of operators with a bilateral control system in a typical industrial valve operation experiment (n = 21). The experiment tested two force feedback conditions: Realistic (the system replicates the exact same feeling of the torque in valve manipulation operations) and Mediated (the simulation reduces the force on the human operator end by 50% to enable more flexible controls). The performance of the participants was evaluated via various metrics, including task performance, human performance and operational velocity uniformity. Data was collected with eye-tracking, neuroimaging (functional near-infrared spectroscopy, fNIRS), motion analysis, and NASA TLX surveys. The results indicated that the mediated force feedback in bilateral telerobotic operation helped more accurate operation, increased dual tasking, reduced cognitive load and more efficient neural functions; yet it encouraged participants to engage in more irregular actions, showing as dramatic changes in valve rotating speeds. The findings suggest that the force feedback design of telerobotic systems should be more carefully thought through to balance the advantages and disadvantages.

Dynamics of bilateral control system with state feedback for price adjustment strategy

The price fluctuation of commodities affects their demand, and it strongly influences the development of industry and the stability of the international economy. A price-output model with two price-dependent impulses is presented in this paper to describe their mutual restrictions and the price adjustment strategies. The equilibria and dynamic properties of the impulsive-free price-output model are qualitatively analyzed, and the results show the hazard of free price fluctuation. For the price-output model with two price-dependent impulses, conditions for the existence of the order-2 periodic solution are obtained, and the orbital asymptotic stability is proved. Those results reveal the positive role of price adjustment strategies. Finally, some numerical simulations are carried out to verify the theoretical results.

Haptic Data Prediction and Extrapolation for Communication Traffic Reduction of Four-Channel Bilateral Control System

Robotic teleoperation with a bilateral control system has attracted attention owing to its haptic transmission performance. However, conventional bilateral control systems require broadband communication to transmit the vivid haptic sensation. This problem limits the application range of the bilateral control systems. The communication traffic can be reduced by predicting and extrapolating the incoming data. However, in the conventional prediction-based methods, only one type (e.g., position, velocity, or force) of data is transmitted per one direction because of the difficulty of predicting multiple independent data. The novelty of this article is the realization of the prediction-based traffic reduction in the four-channel bilateral control system that transmits accurate haptic sensation by communicating both position and force data. By equivalently transforming this control scheme in the structure of impedance control, the transmit data are summed up to one data, equilibrium force. The equilibrium force is not only transmitted but extrapolated on the receiver side. As a result, the communication frequency becomes low without degrading haptic transmission performance. The validity of the proposed method was confirmed through experiments and succeeded to reduce the communication data size to less than 3.0%. The proposed method helps to realize a high-performance bilateral control system on band-limited networks.

Bilateral Control System with MR Fluid Based Haptic Interface for Endoscopic Surgery

Bilateral Control System with MR Fluid Based Haptic Interface for Endoscopic Surgery

Human interface design for semi-autonomous control of leader-follower excavator based on variable admittance and stagnation/trajectory bifurcation of nonlinear dynamics

Conventional remote operation of an excavator has low work efficiency comparing with on-site operations. This is because it is difficult for an operator to recognize the excavator status and surrounding environments. Moreover, there are restrictions such as a limitation on the amount of information that can be transmitted, delays in communication, and harsh environments that cause sensor failure. Therefore, we have developed a semi-autonomous control system that consists of autonomy and human manipulation. This paper proposes (1) a bilateral control system based on variable admittance and (2) an autonomous control using nonlinear dynamics that has attractors with stagnation and trajectory-bifurcation. (1) In the proposed method, the admittance parameters are changed based on the difference between the leader and follower position. We implement the proposed method into a prototype of excavator and verify the operation with two types of external environmental forces: free movement and contact with a rock. (2) The attractor’s stagnation is designed as a sink of vector field converging to an arbitrary point on the trajectory. A stagnation is placed at a trajectory’s bifurcation point, and the operator selects the next operation by adding a force to the leader system, which is measured through a force sensor. We design two types of bifurcating attractors and conduct an experimental verification of the proposed semi-autonomous control system.

The Implementation of Bilateral Control Symmetrical Position, Force Reflection and Feedback Force on the Haptic Manipulator

Humans often encounter obstacles in doing their work. Especially if the work is related to an emergency situation that concerns the safety of human life, it needs quick and appropriate handling. Telerobotic technology that has a haptic function is one solution to these problems. In this study a system of 1 DOF haptic manipulator with slave master configuration was developed using bilateral haptic manipulator control. In bilateral control the position and information are transmitted in two directions between two manipulators. Position information is obtained using a potentiometer and force information is obtained by representing the force with the current using the WCS2702 sensor. There are three control methods used, namely bilateral symmetrical position control, bilateral reflection force control and force feedback bilateral control. The best method of control is the bilateral feedback force control. In the force feedback bilateral control system, the slave can move following the master movement with a ± 2° position error. When the slave arm is held by a hard object, the master arm is also restrained with ± 11° position error. Whereas when the slave arm is held by a soft object, the reflection of the object is felt by the master arm with ± 10 position error. Movement of the master and slave arms is lighter than using bilateral control of symmetrical position.

An Approach to Architecture Design of Bilateral Control System based on a Layer Structure

An Approach to Architecture Design of Bilateral Control System based on a Layer Structure

Dynamics of Unilateral and Bilateral Control Systems with State Feedback for Renewable Resource Management

In this paper, mathematical models for the management of biological resources based on a given predator-prey relationship are proposed, and two types of control strategies, unilateral and bilateral control with impulsive state feedback, are studied. The existence of the order-1 homoclinic orbit, order-1 periodic solution, and bifurcation of homoclinic of the unilateral control system are obtained, and the attraction region of this system is also discussed. Besides, sufficient conditions for the existence and stability of the order-1 and order-2 periodic solutions of the bilateral control system are also gained. A series of numerical simulations including bifurcation diagrams of periodic solution are performed, which not only verify the theoretical results we get but also reveal some peculiar dynamical phenomena, such as the appearance of high-order periodic solutions and existence of parameter intervals with drastic order change of periodic solution. By comparing the two management strategies, our study encourages bilateral control rather than unilateral control for the risk of predator extinction.

Design of Adaptive Controller using Object Position for Bilateral Control System with Communication Delay

Design of Adaptive Controller using Object Position for Bilateral Control System with Communication Delay

PDS Based Bilateral Control System for Nonlinear Flexible Master-Slave Arms with Random Delay Considering Contact with Obstacle

PDS Based Bilateral Control System for Nonlinear Flexible Master-Slave Arms with Random Delay Considering Contact with Obstacle

Design fo Adaptive Contrroller for Bilateral Control System Including a Propeller Driven System

Design fo Adaptive Contrroller for Bilateral Control System Including a Propeller Driven System