Simple Feedforward Control Research Articles

Advanced Feedforward Controller for a Molten Salt Receiver in Star Design Based on Real-Time Flux Measurement

This paper presents a control system with a panel-wise applied feedforward temperature controller for a molten salt receiver in star design utilizing temperature measurements in the connecting pipes between the panels and a real-time flux density measurement as inputs. It is tested in realistic cloud passage scenarios and the results are compared to the results from an earlier developed control system for the same receiver, in which the temperature controller is based on a simple feedback controller (PID) supported by a simple feedforward controller. The results show that the performance of the new feedforward controller is outstanding and could be applied to common cylindrical receiver designs as well. Nevertheless, the highly increased actuator movement of the control valves is to be further investigated.

Direct Power Control of a Surface-Mounted Permanent Magnet Synchronous Generator Wind Turbine for Offshore Applications

This paper proposes a direct power control scheme for an offshore wind turbine-driven surface-mounted permanent magnet synchronous generator with a full back-to-back converter situated onshore to decentralize the weight of the turbine. The proposed model is designed in a stationary reference frame and does not require a phase-locked loop as opposed to the traditional vector current control method. Simple feed-forward and feedback control loops are used in the proposed model to extract the maximum available wind power, maintain constant voltage at the coupling DC link, and ensure power injection into the electric network at unity power factor. Simulation results carried out in MATLAB/SIMULINK show that the proposed model has fast transient response and steady-state performance consistent with the vector current control model. Furthermore, eigenvalue analysis results demonstrate that the proposed method’s performance is robust to variations in different system parasitic elements, even under both stiff and weak electric network conditions. These results also indicate that the back-to-back converter can operate effectively when located onshore close to the load center, while the turbine is in close proximity offshore. This can be suitable for multiple specific offshore applications as it has the potential to reduce the overall weight, volume, and cost of the offshore wind turbine infrastructure.

Stability Improvement of Dynamic EV Wireless Charging System with Receiver-Side Control Considering Coupling Disturbance

Receiver-side control has been a reliable practice for regulating the transferred energy to the batteries in the electric vehicle (EV) wireless power transfer (WPT) systems. Nonetheless, the unpredictable fluctuation of the mutual inductance in dynamic wireless charging brings extreme instability to the charging process. This overshoot that appears in instant vibrations may largely increase the voltage/current stress of the system, and even cause catastrophic failure in the battery load. In addition, the speed of the vehicles may lead to untraceable steady-state operation. However, existing solutions to the above two issues suffer from either long communication time delay or significantly compromised output regulation. In this paper, the slow dynamics and the overshoot issues of the WPT system are elaborated in theory, and the small-signal model mainly considering mutual inductance disturbance is established. A simple feedforward control is proposed for overshoot damping and fast system dynamics. Experimental results validate that the overshoot can be reduced by 13% and the settling time is improved by 50% in vehicle braking or acceleration. In constant speed driving, the battery charging ripple is decreased by 12% and ensures better system stability.

A New Mechanical Design for Legged Robots to Reduce Energy Consumption

Many legged robots have been designed and built by universities, research institutes and industry; however, few investigations regard energy consumption as a crucial design criterion. This paper presents a novel configuration for legged robots to reduce the energy consumption. The proposed leg can be either used as a single leg or easily attached to bodies with four, six and eight legs. This mechanism is a parallel four-bar linkage equipped with one active and four passive joints. In fact, the usage of the passive elements leads to simple feed-forward control paradigms. Moreover, another distinctive feature of this design is the arrangement of one-way clutches and flat springs to store the potential energy for utilizing it in the next step. A locomotion prototype of the proposed mechanical structure is built and its simulation is also presented in this paper. Comparing the results with other structures demonstrates the superiority and efficiency of this work regarding energy consumption problem.

직동외란의 효율적 억제기능을 갖는 서보계 설계법에 관한 연구

This paper presents an interference disturbance compensation method for the connected system. The disturbance is generated from the system motion such that it directly affects the relative motion. For example, in the robot system, the arm motions influence each other because the arms are connected in series. If we design a servosystem for controlling the robot motions including arm angle, the interference disturbance should be carefully considered. The reason for this is that it influences and works as the disturbance which degrades the tracking performance. Therefore, the authors developed a novel interference disturbance rejecting method by simple feedforward control strategy based on the framework of robust servosystem design. By applying the proposed method to a 2DOF robot system, its effectiveness was evaluated.

Average Model-Based Feedforward and Feedback Control for PUC5 Inverter

This paper proposes new average model based control strategies for a 5-level Packed U-cell (PUC5) inverter in both standalone and grid-connected modes of operation. First, a simple feedforward controller (FFC) is designed, using only two pulse width modulation (PWM) carrier signals, for the PUC5 inverter operating in standalone mode. This proposed control technique ensures self-balanced operation with high steady-state performance. Moreover, the employment of the proposed FFC leads to a decrease in the capacitor’s value as well as the minimization of the Total Harmonic Distortion (THD). Then, a feedback linearizing control technique is designed to improve the transient and steady-state performances. In grid-connected mode, a reduced-sensor technique based on the FFC and the state feedback (FC) techniques was applied. Simulations and experimental results are presented to prove the high performance of the proposed solutions for standalone and grid-connected operating modes.

An optimal control strategy for a heat pump in an integrated solar thermal system

In this paper, an optimal control strategy is developed for managing a heat pump in an integrated solar thermal system. Solar thermal systems usually operate with both feedback and feedforward controllers. The focus of many existing studies in solar thermal system applications has been on the feedback part, while less effort has been made to improve the performance of the feedforward part. This paper introduces a novel robust feedforward controller as a sub-controller of an optimal controller for operating a heat pump integrated with the solar thermal system. In a simulation environment, the optimal control structure is implemented, and the performance of the robust feedforward controller is compared with a simple feedforward controller. Regarding the electrical power consumption, the simulation results demonstrate that the optimal control structure with the proposed robust feedforward controller outperforms the control structure with the simple feedforward controller.

Congestion Avoidance in Low-Voltage Networks by using the Advanced Metering Infrastructure

Large-scale decentralized photovoltaic (PV) generators are currently being installed in many low-voltage distribution networks. Without grid reinforcements or production curtailment, they might create current and/or voltage issues. In this paper, we consider the use the advanced metering infrastructure (AMI) as the basis for PV generation control. We show that the advanced metering infrastructure may be used to infer some knowledge about the underlying network, and we show how this knowledge can be used by a simple feed-forward controller to curtail the solar production efficiently. By means of numerical simulations, we compare our proposed controller with two other controller structures: open-loop, and feed-back P(U) and Q(U). We demonstrate that our feed-forward controller - that requires no prior knowledge of the underlying electrical network - brings significant performance improvements as it can effectively suppress over-voltage and over-current while requiring low energy curtailment. This method can be implemented at low cost and require no specific information about the network on which it is deployed.

LED Series Current Regulator Based on a Modified Class-E Resonant Inverter

This paper presents a new topology based on a modified class-E resonant inverter used as an LED series current regulator. The proposed topology behaves as a controllable nondissipative impedance that adjusts the current flowing through the lamp. In this circuit, the LED is placed at the dc side of the class-E inverter, in series with the input filter inductance. The power handled by the ac side is sent back to the input by means of two diodes. Despite the addition of these two diodes, the converter maintains all the advantages of the class-E inverter: low component count, simple control, and extremely low switching losses. The LED current can be controlled with a small variation of the operating frequency. This way, the low-frequency current ripple of the lamp can be strongly reduced even when there is a considerably high input voltage excursion, such as the one expected in electrolyticless high-power-factor LED ballast. This paper proposes a simplified methodology based on the fundamental approach aiming to design and build a laboratory prototype. The prototype is designed in order to minimize the effect of LED voltage in the output current. This way, the input voltage ripple can be canceled using a simple feedforward control.

A Solid-State Converter Topology, −100 kV, 20 A, 1.6 ms, Modulator for High Average Power Klystron Amplifier

This paper presents the design and development of a −100 kV, 20 A, all solid-state long-pulse modulator for driving high average power klystron amplifier. Modular design approach has been adopted for achieving the −100-kV output. Six dc–dc converters along with high-voltage high-frequency transformers are used for high-voltage generation. Low-loss insulated gate bipolar transistor (IGBT) switches in full-bridge configuration have been used for high-frequency switching. The IGBT-based inverter modules are delayed in phase by 120° with respect to each other. The switching frequency is 20 kHz. Output pulses of 1.6-ms pulsewidth, 70- $\mu \text{s}$ rise time, and 65- $\mu \text{s}$ fall time have been achieved at the modulator output. A droop of ±1% is achieved using a simple feedforward correction control technique. The performance of the modulator with the resistive load is presented.

Aerodynamic and load control performance testing of a morphing trailing edge flap system on an outdoor rotating test rig

A testing campaign utilizing DTU’s outdoor rotating rig is described, where a novel morphing flap system developed in collaboration with the University of Bristol within the INNWIND.eu project has been evaluated and successfully demonstrated. In addition, the aerodynamic performance of ECN’s newly designed aerofoil has been evaluated in atmospheric conditions. The morphing wing is shown to achieve good performance in terms of aerodynamic lift control, and compares well with computational fluid dynamics predictions. Moreover, simple feed-forward controller implementations, also utilizing inflow sensors, show promising results in terms of dynamic load alleviation.

A simple input current wave-shaping technique for three-phase diode and SCR converters

ABSTRACTThree-phase converters using diode or silicon-controlled rectifier (SCR) are widely employed to convert the commercial AC supply to DC. Such converters inject harmonics into the power supply system and thereby distort supply system voltage waveform. A simple input current wave-shape improvement technique using a shunt-connected harmonic current compensator is presented in this work, intended to reduce the total harmonic distortion (THD) of input current of three-phase diode and SCR phase-controlled rectifiers operating with inductive loads, by matching them to the specific converter as a combined package. The compensator proposed here comprises of a three-limb voltage source converter using insulated-gate bipolar transistor, working on instantaneous current and voltage measurements of the compensator only and not of the load. The technique uses a simple feedforward control for AC source current harmonic compensation of rectifiers without monitoring the AC line currents, i.e. use of online computation. The proposed system is simulated and tested on a laboratory prototype. The measured input current THD values without additional line filters are found to be below 8.3%, which is within acceptable limits, proving that the new technique is capable of compensating predetermined current harmonics of diode or SCRs.

Fixed-Structure Feedforward Control Law for Minimum- and Nonminimum-Phase LTI SISO Systems

Fundamental limitation of the model-inverse feedforward control results from instability or noncausality of the inverse of nonminimum-phase dynamics which cannot be applied in practice. To overcome this limitation, the approximate-inverse methods have been proposed in the literature. Structures of feedforward controllers proposed so far highly depend on a plant model structure. Therefore, in general, their implementation may be inconvenient or troublesome in industrial applications. In this context, a simple fixed-structure feedforward control law is proposed in this paper in the form of a weighted linear combination of a reference trajectory and its time derivatives. Design rules for selection of the weights are derived and provided in an explicit (analytical) form. The proposed control law can be applied to both nonminimum- and minimum-phase linear time invariant single-input-single-output systems. The new method has been compared with classical feedforward controllers known from the literature, revealing its advantages and limitations. The results of numerical examples and experimental validation tests obtained for an electronic plant have been reported.

A Comparison of Two Pressure Control Concepts for Hydraulic Offshore Wind Turbines

Current research in offshore wind turbines is proposing a novel concept of using seawater-based hydraulics for large-scale power transmission and centralized electrical generation. The objective of this paper is to investigate the control of such an open-loop circuit, where a fixed line pressure is desirable for the sake of efficiency and stability. Pressure control of the open-loop hydraulic circuit presents an interesting control challenge due to the highly fluctuating flow rate along with the nonlinear behavior of the variable-area orifice used by the pressure controller. The present analysis is limited to a single turbine and an open-loop hydraulic line with a variable-area orifice at the end. A controller is proposed which uses a combination of feed-forward compensation for the nonlinear part along with a feedback loop for correcting any errors resulting from inaccuracies in the compensator model. A numerical model of the system under investigation is developed in order to observe the behavior of the controller and the advantages of including the feedback loop. An in-depth analysis is undertaken, including a sensitivity study of the compensator accuracy and a parametric analysis of the actuator response time. Finally, a Monte Carlo analysis was carried out in order to rank the proposed controller in comparison to a simple feed-forward controller and a theoretical optimally tuned controller. Results indicate an advantageous performance of the proposed method of feedback with feed-forward compensation, particularly its ability to maintain a stable line pressure in the face of high parameter uncertainty over a wide range of operating conditions, even with a relatively slow actuation system.

空気圧人工筋駆動小型四脚ロボットの高速走行

This report describes a small quadruped robot driven by pneumatic artificial muscles that can realize fast locomotion. Since the size of the robot is small, the room for the actuators is limited. We simplify the driving mechanism of each leg as three pneumatic artificial muscles and two valves, 13 muscles and 9 valves in total. By applying simple feedforward control, the robot can realize fast trot whose speed is up to 2.67 [m/s] (9.6km/h).

Model-based optimisation and predictive control of a turbocharged diesel engine with variable geometry compressor

This paper presents a model-based optimisation and preliminary control design for a diesel engine equipped with variable geometry turbocharger (VGT), exhaust gas recirculation (EGR), and variable geometry compressor (VGC) systems. Starting from a validated model of the engine air path dynamics, a model-based optimisation is conducted at steady state conditions. The optimisation results define a simple feed-forward control strategy, which shows how the VGC can be used to increase the stability range of the compressor by means of shifting the surge limit of the machine while providing opportunity to improve fuel efficiency and turbo-lag. A design of feedback control is then investigated by coordinating the available actuators to track the desired performance variables derived from the steady state optimisation, and ensure the stability of the compressor during transient. The regulation is formulated as a receding horizon optimisation problem, which is cast as a constrained quadratic programming to reduce the computational load. The proposed controller is implemented into the nonlinear engine model, followed by an analysis of the simulation results.

Development and Flight Testing of a Turbulence Mitigation System for Micro Air Vehicles

There are significant challenges associated with the flight control of fixed-wing micro air vehicles MAVs operating in complex environments. The scale of MAVs makes them particularly sensitive to atmospheric disturbances thus limiting their ability to sustain controlled flight. Bio-inspired, phase-advanced sensors have been identified as promising sensory solutions for complementing current inertial-only attitude sensors. This paper describes the development and flight testing of a bio-inspired, phase-advanced sensor and associated control system that mitigates the impact of turbulence on MAVs. Multihole pressure probes, inspired by the sensory function of bird feathers, are used to measure the flow pitch angle and velocity magnitude ahead of the MAV's wing. The sensors provide information on the disturbing phenomena before it causes an inertial response in the aircraft. The sensor output is input to a simple feed-forward control architecture, which enables the MAV to generate a mitigating response to the turbulence. The results from wind-tunnel and outdoor testing in high levels of turbulence are presented. The disturbance rejection performance of the phase-advanced sensory system is compared against that of a conventional inertial-based control system. The developed sensory system shows significant improvement in terms of disturbance rejection performance compared to that of standard inertial-only control system. It is concluded that a phase-advanced sensory systems can complement conventional inertial-based sensors to improve the attitude-tracking performance of MAVs.

A Simple Analog Feed-Forward Controller Design for DC-DC Buck Converter

This paper presents usage of analog feed-forward control to improve the transient response of DC-DC buck converters with pulse-width-modulation (PWM). The analog feed-forward controller is simple and does not require complicated calculations. Duty cycle is modulated directly based on the charge balance of the output capacitor. Compared with conventional feedback control, this simple feed-forward controller reduces control delay and provides a satisfactory transient response. We apply this technique to a Single-Inductor-Dual-Output (SIDO) buck converter as well as a Single-Inductor-Single-Output (SISO) buck converter, and show that its cross-regulation is improved. We have validated the proposed method with SIMetrix simulations.

차량모델을 고려한 햅틱 큐 기어변속보조 시스템의 성능평가

This paper proposes a driver supportive device with haptic cue function which can transmit optimal gear shifting timing to a driver without requiring the driver's visual attention. Its performance is evaluated under vehicle model considering automotive engine, transmission and vehicle body. In order to achieve this goal, a torque feedback device is devised and manufactured by adopting the MR (magnetorheological) fluid and clutch mechanism. The manufactured MR clutch is then integrated with the accelerator pedal to construct the proposed haptic cue device. A virtual vehicle emulating a four-cylinder four-stroke engine, manual transmission system of a passenger vehicle and vehicle body is constructed and communicated with the manufactured haptic cue device. Control performances including torque tracking and fuel efficiency are experimentally evaluated via a simple feed-forward control algorithm.

Control of a Novel Linear-Rotary Actuator for High-Speed Pick-and-Place Application

A direct-drive electromagnetic actuator is designed with integration of linear and rotary modules in a common shaft. The two-degree-of-freedom motion is driven by two sets of single-phase coils enclosed by dual-magnet and rotary Halbach array accordingly, greatly enlarging the force/torque constants while minimised the moving mass. Moreover, with integral vacuum sensing and actuation, it is extremely suitable for high-speed pick-and-place (PnP) application. Thus, in the second part of this paper, a typical PnP process is designed with sequential motion of linear and rotary axes with s-curve command. It is also proved that the proportional-integralderivative (PID) controllers are capable to stabilise the closed-loop dynamics even with presence of various non-linearities and disturbances in both axes, such as friction, position dependent DC gain, gravity force and counter gravity spring. The experiment test verifies that this 2-DOF actuator is capable to PnP more than 8000 integrated-circuit chips per hour with simple decentralised PID plus feedforward control.