Model predictive control of bidirectional isolated DC–DC converter for energy conversion system

Model predictive control (MPC) is a powerful and emerging control algorithm in the field of power converters and energy conversion systems. This paper proposes a model predictive algorithm to control the power flow between the high-voltage and low-voltage DC buses of a bidirectional isolated full-bridge DC–DC converter. The predictive control algorithm utilises the discrete nature of the power converters and predicts the future nature of the system, which are compared with the references to calculate the cost function. The switching state that minimises the cost function is selected for firing the converter in the next sampling time period. The proposed MPC bidirectional DC–DC converter is simulated with MATLAB/Simulink and further verified with a 2.5 kW experimental configuration. Both the simulation and experimental results confirm that the proposed MPC algorithm of the DC–DC converter reduces reactive power by avoiding the phase shift between primary and secondary sides of the high-frequency transformer and allow power transfer with unity power factor. Finally, an efficiency comparison is performed between the MPC and dual-phase-shift-based pulse-width modulation controlled DC–DC converter which ensures the effectiveness of the MPC controller.     

Modulated–demodulated control: Q control of an AFM microcantilever

We outline the application of modulated–demodulated control to the quality (Q) factor control of an atomic force microscope microcantilever. We review the modulated–demodulated control technique, emphasize its linear time invariant nature and develop state space representations of the controller for design and analysis. The modulated–demodulated controller can be configured as both positive position feedback (PPF) and resonant controllers, which are effective in the control of negative imaginary systems. Negative imaginary systems theory has important application in the control of collocated mechanical systems and we briefly summarize the key relevant results. A high-frequency, tunable modulated–demodulated controller, designed specifically for MHz operation, was developed for experimental validation. The modulated–demodulated controller enables the use of a low-bandwidth baseband controller in the configuration of a high-bandwidth controller, thus simplifying the implementation of high-bandwidth controllers. We outline the controller characterization and demonstrate closed-loop control of a Bruker DMASP microcantilever. We also present AFM images highlighting the improvements in scan speed and image quality achieved as a result of Q control. Modulated–demodulated control appears well suited to the control of high-frequency resonant dynamics. In addition to high-speed atomic force microscopy, we believe this control technique may find applications in high-frequency microelectromechanical systems (MEMS).     

Switching-type fuzzy sliding mode control of a cart–pole system

The theme for a switching-type fuzzy sliding mode controller for the cart–pole system is developed in this paper. The control strategy is to make a vertical pole straight up and regulate the position of cart simultaneously. This system is nonlinear, unstable and nonminimum phase in consideration of these two control purposes; the conventional control algorithms are difficult to solve such a problem because only one control input can be utilized. By taking the experience of balancing a pole by a finger, we divide the dynamic response of the cart–pole system into approaching and departure conditions. Then the cart can be directed to the desired location with a balanced pole by switching two types of fuzzy sliding mode controllers. The feasibility and robustness of the proposed algorithm are demonstrated by computer simulations and actual experimental results.     

Human–robot cooperation control based on a dynamic model of an upper limb exoskeleton for human power amplification

In this paper, we propose a human–robot cooperation controller for the motion of the upper limb exoskeleton. The system permits three degrees of freedom using an electrical actuator that is mainly controlled by force sensor signals. These signals are used to generate the torque required to drive the exoskeleton. However, singularities exist when the force signals in the Cartesian coordinate system are transformed into torques in the joint coordinate system. Therefore, we apply the damped least squares method. When handling a load, torque compensation is required about its mass. Therefore, we installed a force sensor at the point of the robot’s end-effector. It measures the forces between the exoskeleton and the load. Then, these forces are used to compensate within a static model for handling loads. We performed control stability and load handling experiments to verify the effectiveness of the controller. Via these, we confirmed the effectiveness of the proposed controller.     

Shared human–robot path following control of an unmanned ground vehicle

This paper considers the shared path following control of an unmanned ground vehicle by a single person. A passive measure of human intent is used to blend the human and machine inputs in a mixed initiative approach. The blending law is combined with saturated super-twisting sliding mode speed and heading controllers, so that exogenous disturbances can be counteracted via equivalent control. It is proven that when the proposed blending law is used, the combined control signals from both the human and automatic controller respect the actuator magnitude constraints of the machine. To demonstrate the approach, shared control experiments are performed using an unmanned ground vehicle, which follows a lawn mower pattern shaped path.     

Hysteresis modeling and tracking control for a dual pneumatic artificial muscle system using Prandtl–Ishlinskii model

This study investigated pressure/length hysteresis characteristics. Instead of the conventional force/length hysteresis model, a Prandtl–Ishlinskii (P–I) model of a dual pneumatic artificial muscle (PAM) system is presented. For the comparison, an alternative hysteresis model such as Bouc–Wen (B–W) model is also considered. All model parameters are identified by real code genetic algorithm (RCGA). Different feedback control strategies are combined with a feed-forward controller based on a P–I model for hysteresis compensation to reduce the tracking error of the dual PAM system. The experimental results validated the use of the proposed controller for trajectory tracking of PAM systems.     

A new integrated fuzzy bang–bang relay control system

In this paper, we propose a new fuzzy bang–bang relay controller (FBBRC). The bang–bang control systems use switching relays or hard limiter saturation functions with fixed parameters, and their input does not have the flexibility to control the non-linear system over its entire range of operation. The conventional fuzzy bang–bang controllers have an analog output and an external hard limiting device to convert the output to bang–bang action. The new integrated FBBRC proposed here directly output two-level state. The inputs to the FBBRC are configured on standard fuzzy sets on the basis Mamdani implications. The largest of maxima defuzzification method is used for two-level state output. The stability and optimality of the FBBRC can be established with the Lyapunov stability criterion and Pontrygin minimum principle, respectively. Non-linear bang–bang control action is inherently time-optimal and endows this property to the FBBRC. Because of its design simplicity and cost-effectiveness, the bang–bang control is desired for control applications such as spacecraft–satellite attitude, heating controls, and on/off valve controls. Comparison between the proposed FBBRC and the fuzzy bang–bang controller (FBBC) show that FBBRC gives a better response. Finally, we demonstrate a practical application of FBBRC by controlling the angular position of a single-axis pneumatic rotary actuator in real-time, using the Matlab-Simulink xPC target environment.     

Cascade position control of a single pneumatic artificial muscle–mass system with hysteresis compensation

The inherent hysteresis in a pneumatic artificial muscle (PAM) makes it difficult to control accurately the position of the PAM’s end effector. This hysteresis causes energy loss and the area of the hysteresis loop is dependent on the amplitude of the motion and on the underlying causes of the hysteresis phenomenon. This means that if the hysteresis energy loss is properly compensated, a more accurate positioning would be achieved. In this paper, the pressure/length hysteresis of a single PAM is modeled by using a Maxwell-slip model. The obtained model is used in the feedforward path of a cascade position control scheme, in which the inner loop is designed to cope with the nonlinearity of the pressure buildup inside the PAM, whereas the outer loop is designed to cope with the nonlinearity of the PAM dynamics itself. The experimental results show that position control of a single PAM–mass system with hysteresis compensation (HC) is effectively improved compared to a control without HC, and the control system shows high robustness to load changes.     

Improvement of downlink LTE system performances using nonlinear equalization methods based on SVM and Wiener–Hammerstein

In this paper, we present versatile nonlinear equalizer based on support vector machine for a standard downlink LTE link. The nonlinear effects are introduced through a solid state power amplifier. The equalizer is compared with a linear RLS and nonlinear Wiener–Hammerstein (W–H) for 16QAM–MIMO–OFDM transmission, revealing improved performance at 1 Mb/s, by 3 and 2 dB in SNR, respectively, when targeting a EVM (dB) of ?60 dB. SVM equalization also outperforms the Wiener–Hammerstein by 1 dB in SNR.     

Design of integrated and autonomous conductivity–temperature–depth (CTD) sensors

Impedance characterization of interfaces is a basic technique for a large class of chemical and biological sensors. This technique is often used to model interfaces between ion-based and electron-based conductive materials by means of electric variables such as voltage, current and charge. Conductivity–temperature–depth (CTD) sensors are sophisticated devices used in the environmental monitoring field to understand the effects of climate changes on oceans and on marine organisms. They usually require impedance sensing as readout technique. High-accuracy CTD sensors are present on the market but they are bulky and power hungry. However, the downscale of modern CMOS technology allows shrinking very complex bioelectronic interfaces into millimeter square size systems, thus opening a large ground of applications. This paper will describe an IC architecture and the related design approach to implement an electrochemical impedance spectroscopy (EIS) technique for CTD sensing and will propose a general approach for sensing complex impedance with low power consumption and high precision. The presented system is designed to achieve 15-bit resolution and power consumption to ensure lifetime up to 1 year using button-size batteries in ocean environment.     

Position control of shape memory alloy actuator based on the generalized Prandtl–Ishlinskii inverse model

Hysteresis and significant nonlinearities in the behavior of Shape Memory Alloy (SMA) actuators encumber effective utilization of these actuator. Due to these effects, the position control of SMA actuators has been a great challenge in recent years. Literature review of the research conducted in this area shows that using the inverse of the phenomenological hysteresis models can compensate the hysteresis of these actuators effectively. But, inverting some of these models, such as Preisach model, is numerically a complex task. However, the generalized Prandtl–Ishlinskii model is analytically invertible, and therefore can be implemented conveniently as a feedforward controller for compensating hysteresis nonlinearities effects in SMA actuators. In this paper a feedforward–feedback controller is used to control the tip deflection of a large deflected flexible beam actuated by an SMA actuator wire. The feedforward part of the control system is based on the generalized Prandtl–Ishlinskii inverse model while a conventional proportional–integral feedback controller is added to the feedforward controller to increase the accuracy together with eliminating the steady state error in position control process. Experimental results show that the proposed controller performs well in terms of achieving small overshoot and undershoot for square wave tracking as well as small tracking errors for sinusoidal trajectory. It has also great capability for tracking hysteresis minor loops.     

Magnetically shielded electron–optical system of a continuous gyrotron with an operating frequency of 24 GHz

It is shown that it is possible to use warm solenoids with copper winding screened with ferromagnetic shields in order to reduce the solenoid supply power by a factor of 1.8–2 while retaining the strength of the magnetic field in the working space for continuous gyrotrons operating in a frequency range of 24–30 GHz. The configuration of the shields as well as the shape and location of the correcting solenoids providing an extended (up to 10 wavelengths long) section of a uniform field in the region of the gyrotron cavity have been determined. It has been shown that introduction of an additional cathode coil into the magnetic system reduces the degree of nonadiabaticity of the magnetic field approximately by an order of magnitude and thereby makes it possible to use the magnetron injection gun for formation of a helical electron beam. Optimization of the configuration of the gun electrodes based on the trajectory analysis makes it possible to obtain an electron beam whose parameters are as good as parameters of the electron beams formed in classical adiabatic electron–optical systems of gyrotrons.     

Position control of hybrid pneumatic–electric actuators using discrete-valued model-predictive control

The design, modeling and position control of a novel hybrid pneumatic–electric actuator for applications in robotics and automation is presented. The design incorporates a pneumatic cylinder and DC motor connected in parallel. By avoiding the need for a high ratio transmission, the design greatly reduces the mechanical impedance that can make collisions with conventionally actuated robot arms dangerous. A novel discrete-valued model-predictive control (DVMPC) algorithm is proposed for controlling the position of the pneumatic cylinder with inexpensive on/off solenoid valves. A variant of inverse dynamics control is proposed for the DC motor. A prototype was built for validating the actuator design and control algorithms. It is used to rotate a single-link robot arm. The actuator inertia and static friction torque values for the prototype were only 0.6% and 4%, respectively, of the values found for a comparable actuator from an industrial robot. Simulation results for position control of pneumatic actuators with different valve speeds and friction coefficients show that the DVMPC algorithm outperforms a sliding mode control algorithm in terms of position error and expected valve life. Experimental results are presented for vertical rotary cycloidal trajectories. Even with the poor quantization caused by the on/off valves, the pneumatic cylinder controlled by the proposed DVMPC algorithm achieved a 0.7% root mean square error (RMSE) and a 0.25% steady-state error (SSE). With the addition of the DC motor to form the hybrid actuator, the RMSE and SSE were reduced to 0.12% and 0.04%, respectively. By incorporating a novel estimation algorithm, the system was made robust to an unknown payload.     

A study of an hybrid CDN–P2P system over the PlanetLab network

In this work we propose an hybrid CDN–P2P architecture for video contents delivery based on the NextShare platform. Experiments were conducted over the PlanetLab network using a number of peers which encompass real network behaviors. Results show that although the NextShare is based on the original BitTorrent file sharing mechanism, the implemented tools can efficiently deliver video over a heterogeneous and time varying network if peers can rely on an intermediate distribution layer between the CDN and the final users. Among the other benefits, CDN edge servers are significantly offloaded and peers can experience low start-up delays. Architecture design and simulation results are taking place in the context of the European FP7 project COAST.     

H∞ control of electrorheological suspension system subjected to parameter uncertainties

Vehicle suspension is normally used to attenuate unwanted vibration from various road conditions. The successful suppression of the vibration leads to the improvement of ride comfort as well as steering stability of the vehicle. One of attractive candidates to formulate successful vehicle suspension is to use electrorheological (ER) damper. This paper presents robust control performances of ER suspension system subjected to parameter uncertainties associated with sprung mass of the vehicle and time constant of the ER damper. After identifying dynamic bandwidth of a cylindrical ER damper operated with two different ER fluids (one has fast response characteristic, while the other slow response characteristic), a quarter car model is established by incorporating with time constant of the damping force. A robust H_∞ controller, which compensates the sprung mass and time constant uncertainties, is designed in order to suppress unwanted vibration of the vehicle. Control responses such as vertical acceleration of the sprung mass are presented in time and frequency domains. In addition, the effect of time constant of the damping force on the vibration control performance is investigated by undertaking a comparative work between fast and slow dynamic characteristics of the ER damper.     

Semi-Markov performance model of an extended token bus protocol†

In this paper we present the semi-Markov performance model of a bus protocol (IMAP—Improved token bus Multi-Access Protocol) suitable for embedded networks. IMAP is an improvement over the token bus scheme and is proposed in Sood et al. (1986). The semi-Markov model is developed by considering normal and interrupt modes of operation of IMAP. Performance of IMAP has been compared to token-bus scheme.     

H<Subscript>∞</Subscript> control of multiple model subject to actuator saturation: application to quarter-car suspension system

This paper deals with the H_∞ control of nonlinear systems in multiple model representation subject to actuator saturation. An application to Quarter-Car suspension system under actuator saturation is then given using the multiple model approach. The concept of so-called parallel distributed compensation (PDC) is employed for designing control system. The idea of this controller consists in designing a linear feedback control for each local linear model. To address the input saturation problem in this paper, both constrained and saturated controls input cases are proposed. In the two cases, H_∞ stabilization conditions in the sense of Lyapunov method are derived. Moreover, a controller design with larger attraction domain is formulated and solved as a linear matrix inequality (LMI) optimization problem. Our simulation results show that both the saturated and constrained controls can stabilize the resulting closed-loop suspension system and eliminate the effect of external disturbances. Indeed, the main roles of car suspension systems, which consist on improving ride comfort of passengers and the road holding capacity of the vehicle, are achieved.     

Realistic model of compact VLSI FitzHugh–Nagumo oscillators

In this article, we present a compact analogue VLSI implementation of the FitzHugh–Nagumo neuron model, intended to model large-scale, biologically plausible, oscillator networks. As the model requires a series resistor and a parallel capacitor with the inductor, which is the most complex part of the design, it is possible to greatly simplify the active inductor implementation compared to other implementations of this device as typically found in filters by allowing appreciable, but well modelled, nonidealities. We model and obtain the parameters of the inductor nonideal model as an inductance in series with a parasitic resistor and a second order low-pass filter with a large cut-off frequency. Post-layout simulations for a CMOS 0.35 μm double-poly technology using the MOSFET Spice BSIM3v3 model confirm the proper behaviour of the design.     

Digital modular control of high frequency DC–DC converters

This paper presents a solution for controlling integrated DC–DC converters with high switching frequency (>20 MHz). The increase of the switching frequency is a trend biased by output filter volume restrictions and integration demand. The control of DC–DC converters operating at high frequency presents an opportunity to speed up the converter response time but also a challenge specially for the control solution, quiescent current and to limit the sensitivity to process and operating conditions for the mixed signal circuits involved. The solution presented in this work relies on separating the duty-cycle into three parts: a load-free value that depends only on the input and output voltages, a transient fast correction contribution, and an accurate compensation for the IR drop that depends on the load current. The load-free portion of the duty-cycle has a compensation of PVT variations and the fast transient part of the duty-cycle uses a non-linear sliding mode control solution. All the analog blocks required for the implementation of the proposed solution are detailed.     

Statistical analysis of mobile radio reception: an extension of clarke?s model

Statistical analysis and modeling of wireless channels is essential to wireless communication systems. Clarke?s model [1] and the corresponding statistical analysis of mobile radio reception has been widely accepted in numerous wireless applications. Since the component phases in Clarke?s model are assumed to be constant in time, the well-known results of statistical analysis based on this model, such as the autocorrelation and Doppler power spectrum, are not appropriate to describe real wireless channels for which the random environments (radio propagation paths) are time-varying and accordingly for which the channel is non-constant in the absence of Doppler frequency shift. In this paper, we extend the traditional Clarke?s model incorporating the effect of fluctuations in the component phases, and perform the statistical analysis which results in a closed-form expression of the autocorrelation of the fading. The theoretical power spectral density function, which is the Fourier transform of the resultant autocorrelation of the fading, is shown to fit the practical measured spectra, which is in contrast to the traditional theoretical flat fading channel spectra (Jakes? spectrum in [2]). The proposed model and statistical results should have important implications for detailed spectral analysis and channel simulations for real wireless communications systems in random fluctuating electromagnetic propagation environments.