Accepted Manuscripts

Hamidreza Kolbari, Soroush Sadeghnejad, Mohsen Bahrami and Ali Kamali
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040818
In a haptic teleoperation system, which interacts with unknown and hybrid environments, it is important to achieve stability and transparency. In medical usages, the utilization of knowledge on the tissues behavior in a controller design can improve the performance of the surgery in a robot-assisted telesurgery. Simultaneous interaction with hard and soft tissues makes it difficult to achieve stability and transparency. To deal with this difficulty, two controller schemes are designed. At first, a nonlinear mathematical model (inspired by the Hunt-Crossley model), which has the properties of soft and hard tissues, is combined with the slave side dynamic. In the second approach, the reaction force applied by hybrid tissues during the transition between tissues of different properties is modeled as an unknown force acting on the slave side. In a 4-channel (4-CH) architecture, nonlinear adaptive controllers are designed without any knowledge about the parameters of the master, the slave robot, and the environment. For both control schemes, Lyapunov candidate functions provide a way to ensure the stability and transparency in the presence of uncertainties. The testbed comprises two Novint Falcon robots functioning as master and slave robots. Moreover, the experiments are performed on various objects, including a soft cube, a hard cube, and a phantom tissue. This paper rigorously evaluates the performances of the proposed methods, comparing them with each other and other previous schemes. Experimental and numerical results demonstrate the effectiveness of the proposed control schemes.
TOPICS: Robots, Adaptive control, Biological tissues, Surgery, Stability, Control equipment, Transparency, Soft tissues, Biomedicine, Uncertainty, Phantoms, Design, Haptics
Mostafa Bagheri, Miroslav Krstić and Peiman Naseradinmousavi
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040752
In this paper, a novel analytical coupled trajectory optimization of a 7-DOF Baxter manipulator utilizing Extremum Seeking (ES) approach is presented. The robotic manipulators are used in network-based industrial units, and even homes, by expending a significant lumped amount of energy and therefore, optimal trajectories need to be generated to address efficiency issues. These robots are typically operated for thousands of cycles resulting in a considerable cost of operation. First, coupled dynamic equations are derived using the Lagrangian method and experimentally validated to examine the accuracy of the model. Then, global design sensitivity analysis is performed to investigate the effects of changes of optimization variables on the cost function leading to select the most effective ones. We examine a discrete-time multivariable gradient-based extremum seeking scheme enforcing operational time and torque saturation constraints in order to minimize the lumped amount of energy consumed in a path given; therefore, time-energy optimization would not be the immediate focus of this research effort. The results are compared with those of a global heuristic genetic algorithm to discuss the locality/globality of optimal solutions. Finally, the optimal trajectory is experimentally implemented to be thoroughly compared with the inefficient one. The results reveal that the proposed scheme yields the minimum energy consumption in addition to overcoming the robot's jerky motion observed in an inefficient path.
TOPICS: Robots, Trajectories (Physics), Optimization, Manipulators, Torque, Cycles, Energy consumption, Genetic algorithms, Design sensitivity analysis, Equations of motion
Joe Deese and Chris Vermillion
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040759
This paper presents a nested co-design (combined plant and controller design) formulation that uses optimal design of experiments techniques at the upper level to globally explore the plant design space, with continuous-time control parameter adaptation laws used at the lower level. The global design space exploration made possible through optimal design of experiments techniques makes the proposed methodology appealing for complex, non-convex optimization problems for which legacy approaches are not effective. Furthermore, the use of continuous-time adaptation laws for control parameter optimization allows for the extension of the proposed optimization framework to the experimental realm, where control parameters can be optimized during experiments. At each full iteration, optimal design of experiments are used to generate a batch of plant designs within a prescribed design space. Each plant design is tested in either a simulation or experiment, during which an adaptation law is used for control parameter optimization. Two techniques are proposed for control parameter optimization at each iteration: extremum seeking and continuous-time design of experiments. The design space is reduced at the end of each full iteration, based on a response surface characterization and quality of fit estimate. The effectiveness of the approach is demonstrated for an airborne wind energy system, where the plant parameters are the center of mass location and stabilizer area, and the control parameter is the trim pitch angle.
TOPICS: Design, Control equipment, Wind energy systems, Optimization, Experimental design, Plant design, Simulation, Center of mass, Response surface methodology
Xia Liu and Mahdi Tavakoli
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040666
Dead-zone is one of the most common hard nonlinearities ubiquitous in master-slave teleoperation systems, particularly in the slave robot joints. However, adaptive control techniques applied in teleoperation systems usually deal with dynamic uncertainty but ignore the presence of dead-zone. Dead-zone has the potential to remarkably deteriorate the transparency of a teleoperation system in the sense of position and force tracking performance or even destabilizing the system if not compensated for in the control scheme. In this paper, an adaptive bilateral control scheme is proposed for nonlinear teleoperation systems in the presence of both uncertain dynamics and dead-zone. An adaptive controller is designed for the master robot with dynamic uncertainties and another is developed for the slave robot with both dynamic uncertainties and unknown dead-zone. The two controllers are incorporated into the 4-channel bilateral teleoperation control framework to achieve transparency. The transparency and stability of the closed-loop teleoperation system is studied via a Lyapunov function analysis. Comparisons with the conventional adaptive control which merely deal with dynamic uncertainties in the simulations demonstrate the validity of the proposed approach.
TOPICS: Dynamics (Mechanics), Adaptive control, Uncertainty, Transparency, Robots, Control equipment, Stability, Simulation, Engineering simulation
Fateme Bakhshande and Dirk Soeffker
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040662
This paper focuses on the design of an observer-based backstepping controller (BC) for a nonlinear hydraulic differential cylinder system. The system is affected by some uncertainties including modeling errors, external disturbances, and measurement noise. An observer-based control approach is proposed to assure suitable tracking performance and to increase robustness against unknown inputs. The task to estimate system states as well as unknown inputs is performed by a linear Proportional-Integral-Observer (PIO). Input-output linearization is used to linearize the nonlinear system model to be used for the PIO structure. On the other hand, BC is utilized based on nonlinear system model to construct the Lyapunov function and to design the control input simultaneously. Stability or negativeness of the derivative of every-step Lyapunov function is fulfilled. Structural improvement regarding the combination of BC and PIO is the main aim of this contribution. This is supported by a novel stability proof and new conditions for the whole control loop with integrated PIO. Furthermore, parameter selection of BC is elaborately considered by defining a performance/energy criteria. A complete robustness evaluation considering different levels of additional measurement noise, modeling errors, and external disturbances is presented for the first time in this contribution. Experimental results validate the advantages of proposed observer-based approach compared to PIO-based sliding mode control (PIO-SMC) and industrial standard P-Controller.
TOPICS: Cylinders, Position control, Uncertainty, Robustness, Errors, Stability, Control equipment, Noise (Sound), Sliding mode control, Design, Modeling, Nonlinear systems
Rathinasamy Sakthivel, K Raajananthini, P Selvaraj and Yong Ren
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040663
In this paper, the periodic tracking problem is considered for a class of continuous system with uncertainty, time-varying delay and unknown bounded external disturbances. To be precise, in order to attenuate the unknown disturbance effectively, the equivalent-input-disturbance (EID) approach is incorporated into the developed algorithm. Then, the sufficient conditions that guarantee the asymptotic tracking performance of the system understudy are established based on the Lyapunov stability theorem. More precisely, Schur complement and free-weighting matrix approach are utilized to derive the main results. Moreover, the proposed EID-based modified repetitive controller not only reject the unknown external disturbance but also deal with the dead zone effect. Finally, two simulation examples are presented to verify the superiority of the proposed EID based repetitive controller over the conventional repetitive controller.
TOPICS: Theorems (Mathematics), Stability, Control systems, Control equipment, Simulation, Algorithms, Design, Delays, Uncertainty
Jeremy W ven der Buhs and Travis Wiens
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040667
This paper examines modelling the laminar dynamic fluid responses within hydraulic transmission lines that have a tapered shape between the inlet to outlet. There are excellent models available for fast simulation of pressure and flow dynamics within uniform lines, however, the established models for tapered lines either cannot be implemented in the time domain, are complex to implement, or have long simulation times. The enhanced transmission line method (TLM) structure is applied in this paper since it can be computed quickly in the time domain and has shown to accurately model the effects of frequency-dependent friction. This paper presents a method of optimizing the TLM weighting functions, minimizing the error between the TLM transmission matrix terms and a numerical ordinary differential equation (ODE) solution calculated using a boundary value solver. Optimizations have shown that using the TLM to model tapered lines can provide a fair approximation when compared in the frequency domain. Two-dimensional interpolation of a look-up table is possible allowing for quick selection of the optimized parameters. Further investigation into the effects of pipe wall elasticity and its inclusion into the TLM is also performed. Also, an experiment was performed to validate high frequency harmonic peaks present in the frequency response, which yielded acceptable results when compared to the theory, and the proposed tapered TLM. This model can be used in numerous applications where line dynamic effects must be accounted for, especially with digital hydraulic switched inertance converters where high frequencies are present.
TOPICS: Fluids, Modeling, Dynamic response, Transmission lines, Simulation, Differential equations, Pipes, Approximation, Pressure, Flow (Dynamics), Elasticity, Friction, Errors, Frequency response, Interpolation, Shapes
Grzegorz Cieplok
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040668
The solution of the system exciting wire vibrations of the wire sensor allowing to perform time variable measurements, including rapidly changing and of a chaotic nature, are presented in the hereby paper. The system is based on the typical two-coil solution, in which one of the coils is responsible for exciting wire vibrations while the other one for recording these vibrations. The task of maintaining not fading-away natural vibrations of the wire, was solved by the excitation of self-exciting vibrations by means of the impulse system synchronized by the wire motion velocity. The mathematical analysis of the wire motion in the system with the impulse generator, in which the existence of the limiting cycle of the wire natural frequency was proved, is shown in this paper. The computer simulation results, illustrating metrological possibilities of the solution as well as the example of the physical implementation, are also presented.
TOPICS: Wire, Transducers, Strain measurement, Vibration, Impulse (Physics), Sensors, Computer simulation, Cycles, Generators, Mathematical analysis, Excitation
Technical Brief  
Jang-Hyun Park, Seong-Hwan Kim and Tae-Sik Park
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040664
A novel output-feedback controller for uncertain SISO nonaffine nonlinear systems is proposed using high-order sliding mode (HOSM) observer which is a robust exact finite-time convergent differentiator. The proposed controller utilizes (n+1)th-order HOSM observer to cancel the uncertainty and disturbance where $n$ is the relative degree of the controlled system. As a result, the control law has an extremely simple form of linear in the differentiator states. It is required no separate sliding-mode controller or universal approximators such as neural networks or fuzzy logic systems that are adaptively tuned online. The proposed controller guarantees finite time (FT) stability of the output tracking error.
TOPICS: Nonlinear systems, Approximation, Feedback, Control equipment, Fuzzy logic, Uncertainty, Artificial neural networks, Errors, Stability
Ali Hossain Alewai Daraji, Jack M. Hale and Ye Jianqiao
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040669
Doubly curved stiffened shells are essential parts of many large-scale engineering structures, such as aerospace, automotive and marine structures. Optimisation of active vibration reduction has not been properly investigated for this important group of structures. This study develops a placement methodology for such structures under motion base and external force excitations to optimise the locations of piezoelectric sensor/actuator pairs and feedback gain using genetic algorithms for active vibration control. An objective function is developed in the placement methodology based on the maximization of sensor output voltage to optimise the locations of sensor/actuator pairs to attenuate several vibrations modes. The optimal control feedback gain is determined then based on the minimization of the linear quadratic index. A doubly curved composite shell stiffened by beams and bonded with discrete piezoelectric sensor/actuator pairs is modelled in this paper by first-order shear deformation theory using finite element method and Hamilton's principle. The proposed methodology is implemented first to investigate a cantilever composite shell to optimise four sensor/actuator pairs to attenuate the first six modes of vibration. The placement methodology is applied next to study a complex stiffened composite shell to optimise four sensor/actuator pairs to test the methodology effectiveness. The results of optimal sensor/actuator distribution are validated by convergence study in genetic algorithm program, ANSYS package and vibration reduction using optimal linear quadratic control scheme.
TOPICS: Composite materials, Fibers, Sensors, Vibration control, Actuators, Shells, Vibration, Feedback, Genetic algorithms, Shear deformation, Cantilevers, Marine structures, Excitation, Structures, Aerospace industry, Optimal control, Optimization, Finite element methods, Hamilton's principle
Soovadeep Bakshi, Zeyu Yan, Dongmei Chen, Qiang Qian and Yinan Chen
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040665
Manufacturing automation, especially through implementation of autonomous ground vehicle (AGV) technology, has been under intensive study due to increased productivity and reduced variations. The objective of this paper is to present an algorithm on scheduling of an AGV that traverses desired locations on a manufacturing floor. Although many algorithms have been developed to achieve this objective, most of them rely on exhaustive search, which is time-consuming. A novel two-step algorithm that generates 'good', but not necessarily optimal, solutions for relatively large data sets (~1000 points) is proposed, taking into account time constraints. A trade-off analysis of computational expense versus algorithm performance is discussed. The algorithm enables the AGV to find a tour which is as good as possible within the time constraint, using which it can travel through all given coordinates before returning to the starting location or a specified end-point. Compared to exhaustive search methods, this algorithm generates results within a stipulated computation time of thirty seconds on a laptop PC.
TOPICS: Algorithms, Vehicles, Automated guided vehicles, Tradeoffs, Manufacturing, Computation, Laptop computers, Manufacturing automation
Jiguo Dai, Beibei Ren and Qing-Chang Zhong
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040590
This paper proposes an uncertainty and disturbance estimator (UDE)-based controller for nonlinear systems with mismatched uncertainties and disturbances, integrating the UDE-based control and the conventional backstepping scheme. The adoption of the backstepping scheme helps to relax the structural constraint of the UDE-based control. Moreover, the reference model design in the UDE-based control offers a solution to address the "complexity explosion" problem of the backstepping approach. Furthermore, the strict-feedback form condition in the conventional backstepping approach is also relaxed by using the UDE-based control to estimate and compensate "disturbance-like" terms including non-strict-feedback terms and intermediate system errors. The uniformly ultimate boundedness of the closed-loop system is analyzed. Both numerical and experimental studies are provided.
TOPICS: Nonlinear systems, Uncertainty, Feedback, Closed loop systems, Errors, Explosions, Control equipment, Design
A. Sener Kaya and Mehmet Zeki Bilgin
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040436
In this article, an output feedback sliding mode position controller/estimator scheme is proposed to control a SISO system subject to bounded nonlinearities and parametric uncertainties. Various works have been published addressing the theoretical effectiveness of the Third Order Sliding Mode Control (3-SMC) in terms of chattering alleviation and controller robustness. However, the application of 3-SMC with a feedback estimator to a flight actuators has not been treated explicitly. This is due to the fact that the accurate full state estimation is required since SMCs performance can be severely degraded by measurement or estimation noise. Aerodynamic control surface actuators in air vehicles mostly employ linear position controllers to achieve guidance and stability. The main focus of the paper is to experimentally demonstrate the stability and positioning performance of a third order SMC applied to a class of system with high relative degree and bounded parametric uncertainties. The performance of the closed loop system is also compared with a lower level SMC and classical controller to show the effectiveness of the algorithm. Realization of the proposed algorithm from an application perspective is the main target of this paper and it demonstrates that a shorter settling time and higher control action attenuation can be achieved with the proposed strategy.
TOPICS: Control equipment, Feedback, Flight, Surface mount components, Sliding mode control, Actuators, Algorithms, Uncertainty, Stability, Vehicles, Closed loop systems, Robustness, State estimation, Noise (Sound)
Technical Brief  
Pritthi Chattopadhyay, Sudeepta Mondal, Asok Ray and Achintya Mukhopadhyay
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040210
A critical issue in design and operation of combustors in gas turbine engines is mitigation of thermoacoustic instabilities, because such instabilities may cause severe damage to the mechanical structure of the combustor. Hence, it is important to quantitatively assimilate the knowledge of the system conditions that would potentially lead to these instabilities. This technical brief proposes a dynamic data-driven technique for design of combustion systems by taking stability of pressure oscillations into consideration. Given appropriate experimental data at selected operating conditions, the proposed design methodology determines a mapping from a set of operating conditions to a set of quantified stability conditions for pressure oscillations. This mapping is then used as an extrapolation tool for predicting the system stability for other conditions for which experiments have not been conducted. Salient properties of the proposed design methodology are: 1. It is dynamic in the sense that no fixed model structure needs to be assumed; and a suboptimal model (under specified user-selected constraints) is identified for each operating condition. An information-theoretic measure is then used for performance comparison among different models of varying structures and/or parameters. 2. It quantifies a (statistical) confidence level in the estimate of system stability for an unobserved operating condition by using a Bayesian nonparametric technique. The proposed design methodology has been validated with experimental data of pressure time-series, acquired from a laboratory-scale lean-premixed swirl-stabilized combustor.
TOPICS: Combustion chambers, Design, Stability, Design methodology, Pressure, Oscillations, Combustion systems, Gas turbines, Time series, Mechanical structures, Damage
Mohammad Reza Amini, Mahdi Shahbakhti and Selina Pan
J. Dyn. Sys., Meas., Control   doi: 10.1115/1.4040208
Sliding mode control (SMC) is a robust and computationally efficient model-based controller design technique for highly nonlinear systems, in the presence of model and external uncertainties. However, the implementation of the conventional continuous-time SMC on digital computers is limited, due to the imprecisions caused by data sampling and quantization, and the chattering phenomena, which results in high frequency oscillations. One effective solution to minimize the effects of data sampling and quantization imprecisions is the use of higher order sliding modes. To this end, in this paper, a new formulation of an adaptive second order discrete sliding mode control (DSMC) is presented for a general class of multi-input multi-output (MIMO) uncertain nonlinear systems. Based on a Lyapunov stability argument and by invoking the new Invariance Principle, not only the asymptotic stability of the controller is guaranteed, but also the adaptation law is derived to remove the uncertainties within the nonlinear plant dynamics. The proposed adaptive tracking controller is designed and tested in real-time for a highly nonlinear control problem in spark ignition combustion engine during transient operating conditions. The simulation and real-time processor-in-the-loop (PIL) test results show that the second order single-input single-output (SISO) DSMC can improve the tracking performances up to 90%, compared to a first order SISO DSMC under sampling and quantization imprecisions, in the presence of modeling uncertainties. Moreover, it is observed that by converting the engine SISO controllers to a MIMO structure, the overall controller performance can be enhanced by 25%, compared to the SISO second order DSMC, because of the dynamics coupling consideration within the MIMO DSMC formulation.
TOPICS: Sliding mode control, Control equipment, Uncertainty, Nonlinear systems, Engines, Dynamics (Mechanics), Stability, Combustion, Engineering design processes, Modeling, Simulation, Transients (Dynamics), Computers, Ignition, Oscillations

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