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Review Article

J. Dyn. Sys., Meas., Control. 2018;140(10):100801-100801-5. doi:10.1115/1.4039716.

In this paper, a new robust terminal synergetic control scheme is proposed to regulate blood glucose level in diabetic patients (type I diabetes), based on recently developed synergetic control and a terminal attractor technique. The technique presented has the advantage of using a continuous control law. Moreover, the proposed control scheme, besides being chattering free, has the characteristics of finite time convergence. Lyapunov synthesis is adopted to ensure controlled system stability. Simulation results of terminal synergetic control are compared to classic synergetic and second-order sliding mode control (SMC) performance, demonstrating that the proposed control method allows for rapidly achieving normoglycemia in type I diabetes patients.

Commentary by Dr. Valentin Fuster

Research Papers

J. Dyn. Sys., Meas., Control. 2018;140(10):101001-101001-8. doi:10.1115/1.4039663.

Electro-hydraulic load simulator (EHLS) is a typical closed-loop torque control system. It is used to simulate the load of aircraft actuator on ground hardware-in-the-loop simulation and experiments. In general, EHLS is fixed with actuator shaft together. Thus, the movement of actuator has interference torque named the surplus torque on the EHLS. The surplus torque is not only related to the velocity of the actuator movement, but also related to the frequency of actuator movement. Especially when the model of the actuator and EHLS is dissimilar, the surplus torque is obviously different on different frequencies. In order to eliminate the surplus torque for accurate load simulation, the actuator velocity input feedforword compensating method (AVIFC) is proposed in this paper. In this strategy, the actuator velocity synchronous signals are used for compensation of different frequency actuator movement to eliminate surplus torque on different frequencies. First, the mathematical model of EHLS and the actuator system is established. Based on the models, the AVIFC method is proposed. It reveals the reason that generates surplus torque on different frequencies of actuator. For verification, simulations and experiments are conducted to prove that the new strategy performs well against low, medium, and high frequency movement interference. The results show that this method can effectively suppress the surplus torque with different frequencies and improve precision of EHLS with actuator movement.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101002-101002-14. doi:10.1115/1.4039687.

Hybrid tracked vehicles are common in construction, agriculture, and military applications. Most use a series hybrid powertrain with large motors and operate at a relatively low efficiency. Although some researchers have proposed power-split powertrains, most of these would require an additional mechanism to achieve skid steering. To solve this problem and enhance drivability, a single-mode power-split hybrid powertrain for tracked vehicles with two outputs connected to the left and right tracks is proposed. The powertrain with three planetary gears (PGs) would then be able to control the torque on the two tracks independently and achieve skid steering. This powertrain has three degrees-of-freedom (DOF), allowing for control of the output torques and the engine speed independently from the vehicle running speed. All design candidates with three PGs are exhaustively searched by analyzing the dynamic characteristics and control to obtain the optimal design. Efficient topology design selection with parameter sizing and component sizing is accomplished using the enhanced progressive iteration approach to achieve better fuel economy using downsized components.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101003-101003-7. doi:10.1115/1.4039667.

This paper investigates the issue of finite time stability analysis of time-delayed neural networks by introducing a new Lyapunov functional which uses the information on the delay sufficiently and an augmented Lyapunov functional which contains some triple integral terms. Some improved delay-dependent stability criteria are derived using Jensen's inequality, reciprocally convex combination methods. Then, the finite-time stability conditions are solved by the linear matrix inequalities (LMIs). Numerical examples are finally presented to verify the effectiveness of the obtained results.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101004-101004-9. doi:10.1115/1.4039786.

This paper presents an optimized input-shaped model reference control (OIS-MRC) for limiting oscillation of multimode flexible systems. The controller is analyzed by using it to control an uncertain, time-varying double pendulum using a linear single-pendulum reference model. Single- and double-pendulum dynamics are presented, and the significant natural frequency ranges of the double pendulum are calculated. A Lyapunov control law using only the first mode states of the plant is obtained. An optimization technique is used to obtain the OIS-MRC controller parameters that realizes the shortest time duration, while meeting a set of design constraints. The oscillation suppression, control effort reduction, and disturbance rejection performances of the proposed OIS-MRC controller are tested via numerical simulations and experiments. The OIS-MRC achieves a robust oscillation suppression performance, while reducing the rise time.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101005-101005-9. doi:10.1115/1.4039668.

Input shaping is widely used in the control of flexible systems due to its effectiveness and ease of implementation. Due to its open-loop nature, it is often overlooked as a control method in systems where parametric uncertainty or force disturbances are present. However, if the disturbances are known and finite in duration, their effect on the flexible mode can be approximated by formulating an initial condition control problem. With this knowledge, an input shaper can be designed, which cancels the initial oscillation, resulting in minimal residual vibration. By incorporating Specified Insensitivity robustness constraints, such shapers can be designed to ensure good performance in the presence of modeling uncertainty. This input shaping method is demonstrated through computer and experimental methods to eliminate vibration in actuator bandwidth-limited systems.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101006-101006-20. doi:10.1115/1.4039785.

In this paper, the free vibration behavior of functionally graded (FG) thin annular sector plates in thermal environment is studied using the differential quadrature method (DQM). The material properties of the FG plate are assumed to be temperature dependent and vary continuously through the thickness, according to the power-law distribution of the volume fraction of the constituents. The nonlinear temperature distribution along the thickness direction of the plate is considered. Based on the classical plate theory, the governing differential equations of motion of the plate are derived and solved numerically using DQM. The natural frequencies of thin FG annular sector plates in thermal environment under various combinations of clamped, free, and simply supported boundary conditions (BCs) are presented for the first time. To ensure the accuracy of the method, the natural frequencies of a pure metallic plate are calculated and compared with those existing in the literature for the homogeneous plate where the results are in good agreement. The effects of temperature field, BCs, volume fraction exponent, radius ratio, and the sector angle on the free vibrations of the FG-plate are examined.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101007-101007-14. doi:10.1115/1.4039859.

This paper introduces a generic function for automated modeling and feedforward control of planetary gears (PGs). Given the information on configuration, namely, the internal connection relationship between each PG, location of external torques, location and locking state of each clutch, this function outputs a ready-to-use kinetic model. The derived model can then be converted into numeric form by substituting the symbols in the matrix with real values and used for simulation, analysis or controller design. Since the output of the function is in symbolic form, it provides the theoretically most accurate results. Furthermore, compared to other kinds of automated modeling techniques for PG, the proposed function is: (a) more “straightforward” in a sense that it relies solely on direct matrix formulation and no other methods such as system identification are needed and therefore can be implemented in a single environment such as matlab; (b) more “generic” since it is capable of deriving both full-degrees-of-freedom (DOF) and reduced-DOF models for virtually any configuration regardless of the number, connection, and location of input/output shafts or clutches. By exchanging certain variables in the list of unknowns and knowns, the function can also be used to facilitate the design of feedforward controllers.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101009-101009-14. doi:10.1115/1.4039185.

In this paper, a hierarchical control logic for two-channel hydraulic active roll control (ARC) system, which includes vehicle level control and actuator level control is proposed. Vehicle level control consists of antiroll torque controller and antiroll torque distributor. The antiroll torque controller is designed with “PID + feedforward” algorithm to calculate the total antiroll moment. The antiroll torque distributor is devised based on fuzzy control method to implement an antiroll moment allocation between the front and rear stabilizer bar. Actuator level control is designed based on pressure and displacement, respectively. The contrastive analysis of the two proposed actuator control method is presented. The hardware-in-the-loop (HIL) test platform is proposed to evaluate the performance of the devised control algorithm. The HIL simulation result illustrates that actuator displacement control could generate a relatively accurate antiroll moment, and the vehicle roll stability, yaw stability can be enhanced by the proposed ARC control method.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101010-101010-10. doi:10.1115/1.4039787.

The unconventional down-hole resources such as shale oil and gas have gradually become a critical form of energy supply thanks to the recent petroleum technology advancement. Its economically viable and reliable production highly depends on the proper operation and control of the down-hole drilling system. The trend of deeper drilling in a complex environment requires a more effective and reliable control optimization scheme, either for predrilling planning or for online optimal control. Given the nonlinear nature of the drilling system, such an optimal control is not trivial. In this paper, we present a method based on dynamic programming (DP) that can lead to a computationally efficient drilling control optimization. A drilling dynamics model that can enable this method is first constructed, and the DP algorithm is customized so that much improved computational efficiency can be achieved compared with using standard DP. A higher-order dynamics model is then used to validate the effectiveness of the optimized control, and the control robustness is also evaluated by adding perturbations to the model. The results verify that the proposed approach is effective and efficient to solve the down-hole drilling control optimization problem.

Commentary by Dr. Valentin Fuster
J. Dyn. Sys., Meas., Control. 2018;140(10):101011-101011-14. doi:10.1115/1.4040072.

An adjoint sensitivity-based approach to determine the gradient and Hessian of cost functions for system identification of dynamical systems is presented. The motivation is the development of a computationally efficient approach relative to the direct differentiation (DD) technique and which overcomes the challenges of the step-size selection in finite difference (FD) approaches. An optimization framework is used to determine the parameters of a dynamical system which minimizes a summation of a scalar cost function evaluated at the discrete measurement instants. The discrete time measurements result in discontinuities in the Lagrange multipliers. Two approaches labeled as the Adjoint and the Hybrid are developed for the calculation of the gradient and Hessian for gradient-based optimization algorithms. The proposed approach is illustrated on the Lorenz 63 model where part of the initial conditions and model parameters are estimated using synthetic data. Examples of identifying model parameters of light curves of type 1a supernovae and a two-tank dynamic model using publicly available data are also included.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Dyn. Sys., Meas., Control. 2018;140(10):104501-104501-10. doi:10.1115/1.4039562.

Nonlinear dynamics in the transmission and drive shafts of automotive powertrains, such as backlash, induce significant torque fluctuations at the wheels during tip-in and tip-out transients, deteriorating drivability. Several strategies are currently present in production vehicles to mitigate those effects. However, most of them are based on open-loop filtering of the driver torque demand, leading to sluggish acceleration performance. To improve the torque management algorithms for drivability and customer acceptability, the powertrain controller must be able to compensate for the wheel torque fluctuations without penalizing the vehicle response. This paper presents a novel backlash compensator for automotive drivetrain, realized via real-time model predictive control (MPC). Starting from a high-fidelity driveline model, the MPC-based compensator is designed to mitigate the drive shaft torque fluctuations by modifying the nominal spark timing during a backlash traverse event. Experimental tests were conducted with the compensator integrated into the engine electronic control unit (ECU) of a production passenger vehicle. Tip-in transients at low-gear conditions were considered to verify the ability of the compensator to reduce the torque overshoot when backlash crossing occurs.

Commentary by Dr. Valentin Fuster

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