The local force control loop approach in bilateral control of master-slave systems

Radio frequency (rf) control loops are vital components for the optimal operation of rf systems in synchrotron particle accelerators. Modeling these systems in macroparticle tracking simulations provides improved understanding of the complex interaction between the control loops, the beam-induced voltages in the rf cavities, and the circulating beam. This paper details an implementation of local and global rf control loops in the beam longitudinal dynamics (on) simulation suite, which allow for the coupling of the two systems in a macroparticle tracking code for the first time. First, benchmarks of the local control loops in the CERN Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC) are given. The implementation coupling the local and global loops is then tested in the SPS with momentum shifts at constant magnetic field and through the damping of phase offsets at injection into the LHC. Both test cases show the expected behavior and validate the model in on. Finally, the SPS simulation model, which now is able to combine beam-induced voltages, global control loops and local ones, is benchmarked against measurements at the bunch-to-bucket transfer into the real accelerator. The simulations, using the coupled implementation of the loops, are able to reproduce bunch-by-bunch beam parameters at flat bottom as well as uncaptured beam generated at injection.

In teleoperation tasks, communication delays between master and slave sides negatively affect the stability and transparency of closed loop system, and make it difficult to maintain a desired contact force. In order to improve the performance of contact force control in teleoperation under large time delays, a shared compliant control method is proposed in this paper. On the master side, the operator issues a desired contact force command according to the feedback of the contact stiffness identified on line besides motion commands. And on the slave side, a local contact force controller is designed using an adaptive Smith predictor, so as to shares control load with the operator. Experimental results show that this method can improve the force control performance, lower the difficulty of operation, and help the operator complete contact tasks with proper forces.In teleoperation tasks, communication delays between master and slave sides negatively affect the stability and transparency of closed loop system, and make it difficult to maintain a desired contact force. In order to improve the performance of contact force control in teleoperation under large time delays, a shared compliant control method is proposed in this paper. On the master side, the operator issues a desired contact force command according to the feedback of the contact stiffness identified on line besides motion commands. And on the slave side, a local contact force controller is designed using an adaptive Smith predictor, so as to shares control load with the operator. Experimental results show that this method can improve the force control performance, lower the difficulty of operation, and help the operator complete contact tasks with proper forces.

We consider the problem of stabilization with respect to a prescribed position for the translational motion of a rigid body with interior material points connected with each other and with the exterior body by linear viscoelastic constraints. The motion occurs under the action of a constant exterior perturbation and a bang-bang control force that are directed along the line of motion. We assume that the bang-bang force control channel has a fixed delay, so that arbitrarily frequent switchings are impossible. We suggest a positional control ensuring the solution of this problem. We estimate the amplitude of the rigid body vibrations about the center of mass of the entire structure and the accuracy of stabilization of the prescribed position of the rigid body depending on the mechanical characteristics of the system and the control force magnitude. We also consider the problem of maximizing the stabilization accuracy depending on the control parameters. By way of example, we consider the controlled motion of a two-mass oscillatory system. This work is closely related to [1–3] and continues the studies of the guaranteed optimal bang-bang controllers with delay in the control channel [4–9]. The dynamics of a rigid body with elastic and dissipative elements was studied in [10] under the assumption that the period of natural vibrations and their decay time are small compared with the characteristic time of motion.

In this paper, a new robust adaptive nonlinear teleoperation system using an improved extended active observer (IEAOB), adaptive Smith predictor (ASP) and sliding mode control is developed to address the time delay in the communication channels and the nonlinear robot model uncertainties. Firstly, an ASP based on Padé approximation and active observer is designed to compensate for the time delay effect. Specifically, the total network time delay is modelled by Padé approximation, and then an active observer is deployed to estimate the time delay. To ensure the time-varying delay effect is completely suppressed, a sliding mode control algorithm is further developed. The main added value of this teleoperation approach is that it requires neither specific mathematic delay-time model, nor strict assumptions on time delay from a practical point of view. Finally, the stability of the designed teleoperation system is theoretically studied and the system effectiveness is demonstrated by applying it to a pair of Phantom Omni haptic devices connected via a communication channel with time-varying delays.

Constrained motion of a planar rigid-flexible manipulator is considered in this study. a dynamic model with zero tip deformation constraint of constrained rigid-flexible 608

Resilient load frequency control design: DoS attacks against additional control loop

The increasing complexity of energy systems leads to a growing interest in energy management that is actively studied using modelling methods and simulation tools capable to represent the re system’s behavior. In this study, a functional energetic modelling method is proposed to design the control architecture for the management of the energy flow. This method relies on local control loops, a decision manager (DM) and basic equations. When the functional level of abstraction is used to model a complex system, the evaluation of the model accuracy (from an energetic point of view) and the validation of energy management strategies are simplified by fast simulations due to low model complexity. Even if the functional model allows a first-stage validation of the energy allocation within the system, the energy management strategies have to be tested using a more precise model, which is the multi-physical model of the system. The multi-physical modelling level has its own local controllers and global resource manager (GRM) to handle the energy allocation between the different components. The second-stage in the validation is completed by adapting the functional model in order to obtain the high-level controller (i.e. the GRM) for the multi-physical level. The development of the control architecture of the multi-physical model based on the functional model requires two steps: (i) adjusting the functional elements’ parameters and (ii) proposing a method to interconnect the models at both levels of representation (functional and multi-physical levels). The modelling and the parametrization of the functional elements are demonstrated on a hybrid electric vehicle (HEV). The GRM design is detailed and the simulation results of the HEV system at multi-physical level are illustrated to validate the system architecture, the component sizing and the energy management strategy. The fuel consumption is evaluated in comparison to the HEV’s design specifications.

Adaptive power control is an effective technique to deal with time delay and channel parameter uncertainty in codedivision multiple access (CDMA) wireless communication systems. However, almost all existing adaptive power control algorithms assume that the time delay is known and fixed. This paper investigates adaptive power control of CDMA systems with unknown and time varying transmission delay in communication channels. To compensate for the time-varying delay and reduce the effects of channel parameter uncertainty, a novel adaptive power control algorithm is presented based on time delay and channel parameter estimations. Simulation results are given to demonstrate the effectiveness of the proposed algorithm.

This paper presents a dynamic virtual environment tool for training operators and to prove different control schemes in telerobotic systems, and describes virtual reality environments used in teleoperated robotic systems. In the presented tool, the kinematic and dynamic model of the remote environment which is manipulating the operator is considered. The paper also describes how time delays in the communication channel can be easily added to the simulator, in order to analyze their effects in the teleoperated system. Finally, some experimental results achieved with this virtual teleoperated system are shown. With the presented dynamic simulator, different control schemes designed to overcome the time delay problem could be tested. © 2005 Wiley Periodicals, Inc.

Time delay compensation is very important in the teleoperation field because time delay deteriorates the system performance and stability. Therefore, a lot of research about time delay compensation have been proposed and developed. One of the effective methods, communication disturbance observer (CDOB) has realized the time delay compensation for the position tracking in bilateral teleoperation. Thanks to CDOB, the smooth operation has been achieved. However, the precise force matching has not been achieved yet by any methods. To solve this problem, the time delay compensation method for the force control system has been proposed. This method realizes the precise contact force control under time delay. Therefore, the time delay compensation method is extended to bilateral teleoperation in this paper. In other words, the time delay compensation for the force controller in the bilateral teleoperation system is proposed toward the precise force matching. The validity is confirmed by the experiments.

In this paper, adaptive controls are proposed for hybrid motion/force synchronization of master-slave tele-operation system with unsymmetric time-varying delays in communication channels. Using partial feedback linearization, the whole tele-operation system contained both master and slave manipulator dynamics is transformed into two subsystems: local master/slave motion/force control with unmodelled dynamics and delayed motion/force synchronization. Then, adaptive controls combing Linear Matrix Inequalities (LMIs) are proposed to deal with the dynamical uncertainties and robust against time delay. The proposed controls are robust against relative motion disturbances, parametric uncertainties and time delays, which are validated by extensive simulation studies.

Softness is an important source of information when interacting with real, remote, or virtual environments (VE) via a haptic human-machine-interface. Humans have no dedicated sense for perceiving softness; instead, inferring an object’s compliance haptically requires the combination of movement and force cues. A telepresence or VE system can alter an object’s mechanical impedance by artefacts such as time delay in the communication channel. Determining the limits for distortions caused by the technical system that do not affect the operator’s softness percept is crucial to ensure a realistic interaction experience. Characterising the perceptual system with a single performance measure such as the just noticeable difference (JND) neglects the role of active movement, which is known to influence perceptual performance. Overcoming this drawback, we propose the usage of dynamic models for haptic perception. On the example of an interaction with a soft virtual environment with time delay in the force feedback, we compare the prediction accuracy of different softness perception model candidates. Experimental data from three psychophysical experiments indicates that a dynamic state observer model captures the perceptual characteristics better than a time delay JND measure and an predictor base on an inverse model representation of the environment.

In this paper, adaptive control is proposed for hybrid position/force synchronization of master-slave teleoperation systems with time-varying delays in communication channels. Different from previous works on bilateral teleoperation systems, we investigate position/force control of bilateral teleoperation systems subject to time-varying delays and dynamical uncertainties. Using partial feedback linearization, the dynamics of both master and slave are transformed into two subsystems: local master/slave position/force control with unmodeled dynamics and delayed position/force synchronization. An adaptive control is proposed to deal with the dynamical uncertainties and robust against time delays, which guarantees the position/force synchronization trajectories converge to the desired manifolds with prescribed performance. The stability of the closed-loop system and the boundedness of synchronization tracking errors are proved using linear matrix inequalities based on Lyapunov stability synthesis. The position/force tracking error up to an ultimately bounded error is achieved. The proposed adaptive controls are robust against relative motion disturbances, parametric uncertainties, and time delays, and are validated by experimental studies.

Degree of freedom based set-point reset scheme for HVAC real-time optimization

This paper describes recent advances in structural quieting technology as applied to active truss structures intended for high precision space based optics applica tions. The active structure incorporates piezoelectric active members which exert control forces internal to the structure and thereby improve the structure's dimensional stability. The control architecture involves two layers of feedback control. The first utilizes col located measurements of force and velocity at the active member to achieve active damp ing, the second utilizes noncollocated measurements of acceleration at the location of a simulated optical component to achieve structural stabilization. The local control loops are based on the concept of impedance matching, the global control loops are designed using robust control methods. These two levels of control are intended to operate simulta neously; however, in this paper each approach is applied individually. The combined im plementation is left for future work.