Unknown Constant Load Research Articles

Lyapunov-based estimation and control of velocity and load in rotating machines via Luenberger globally-convergent observer

This paper presents the design of a Lyapunov-based Luenberger-like observer to simultaneously estimate the non-available angular velocity and the unknown constant load torque of rotating machines. This proposal assumes that the only measurable output is the rotor angle, which is considered to be defined in the circle, its natural topology. This provides nonlinear dynamics where the Lyapunov-based Luenberger-like observer globally converges. Moreover, a trajectory tracking controller for the motor angular velocity is also designed by feeding back the observer estimations. Convergence analysis of the observer-controller system is performed using Lyapunov-like theory. The effectiveness and performance of the system are validated through tests performed on an experimental platform.

A reduced-order adaptive state observer for DC–DC converters with unknown constant power load

In this paper, main objective is to develop a reduced-order adaptive state observer (RASO) for a large class of DC–DC converters with constant power load (CPL) to estimate their unavailable states and unknown parameter, which facilitates achieving an output feedback control (OFC) scheme of the systems. Its construction contains two main procedures. First, by using a generalized parameter estimation based observer (GPEBO) technique, state reconstruction problem is reformulated as the estimate of parameter after the system reparameterization. A linear regressor equation is then obtained. Second, we apply GPEBO technique for it again and then dynamic regressor extension and mixing (DREM) method are adopted such that a RASO for the converters described by a class of bilinear system is designed, which is called as 2G+D observer. The comparison study among the proposed observer and other existing observers is conducted. An obvious merit of the former is that the observability of the systems is only verified for ensuring exponential convergence without needing any extra excitation condition. Subsequently, the presented observer is applied to boost converter feeding unknown CPL for achieving an OFC. Finally, the simulation and experimental results are provided.

Adaptive Voltage Control for Second-Order DC–DC Converters Supplying an Unknown Constant Power Load: A Generalized PBC Plus Damping Injection Design

This paper presents a generalized controller design to regulate the output voltage of second-order DC-DC converters feeding an unknown constant power load (CPL). Passivity-based control plus damping injection theory is employed to design a generalized action control to stabilize DC-DC converters. Furthermore, starting from the immersion and invariance (I&I) method, a generalized observer for second-order DC-DC converters is implemented to estimate the CPL value. By mixing the proposed controller with the I&I method, an adaptive generalized control approach is presented, which guarantees the locally asymptotic stability of the closed-loop for each converter. The main advantage of the nonlinear adaptive control design is its nonparametric dependence on the capacitance and inductance values, which makes it robust against parametric uncertainties. Phase portrait and sensitivity analyses are performed, and simulation and experimental results are examined to evaluate the performance of the proposed approach, which is also compared against feedback linearization and sliding mode control. Simulation and experimental results show the robustness and effectiveness of the adaptive proposed control approach.

Adaptive Sensorless PI+Passivity-Based Control of a Boost Converter Supplying an Unknown CPL

This paper presents an adaptive control to stabilize the output voltage of a DC–DC boost converter that feeds an unknown constant power load (CPL). The proposed controller employs passivity-based control (PBC), which assigns a desired system energy to compensate for the negative impedance that may be generated by a CPL. A proportional-integral (PI) action that maintains a passive output is added to the PBC to impose the desired damping and enhance disturbance rejection behavior, thus forming a PI+PBC control. In addition, the proposed controller includes two estimators, i.e., immersion and invariance (I&I), and disturbance observer (DO), in order to estimate CPL and supply voltage for the converter, respectively. These observers become the proposed controller for an adaptive, sensorless PI+PBC control. Phase portrait analysis and experimental results have validated the robustness and effectiveness of the adaptive proposed control approach. These results show that the proposed controller adequately regulates the output voltage of the DC–DC boost converter under variations of the input voltage and CPL simultaneously.

Nonlinear control of the boost converter subject to unknown constant power load and parasitics

ABSTRACT A robust adaptive controller is developed to regulate the output voltage of the boost converter feeding an unknown constant power load (CPL) and subject to unknown parasitic parameters. The boost converter is a non-minimum phase system that is very prone to the destabilising effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilising controllers. An adaptive controller is developed to tightly regulate the output voltage of the converter despite large load variations, parasitic elements in the converter parameters and instability effects induced by the CPL. A systematic procedure is developed to select the adaptive controller gains to achieve a satisfactory output response. Using simulation, the effectiveness of the proposed controller is validated and compared to a recent robust nonlinear controller.

Stabilization of DC–DC buck converter with unknown constant power load via passivity‐based control plus proportion‐integration

It is known that constant power load (CPL) may cause a negative impedance, which seriously affects the stability of power system. In this paper, a new control algorithm for DC–DC buck converter feeding unknown CPL is proposed. First, under the assumption of known extracted power load, the standard passivity–based control (PBC) is presented to reshape the system energy and compensate for the negative impedance and a proportion-integration (PI) action around passive output is added to improve disturbance rejection performance, which forms the PBC plus PI (PBC+PI). Then, a parameter estimation algorithm is developed, based on immersion and invariance (I&I) technique, in order to online estimate the extracted power load. In the next step, the online estimation scheme is adopted to construct an adaptive strategy. Finally, the stability analysis of the cascaded system containing a closed-loop control system and observer error dynamics is conducted. Simulation and experimental results are demonstrated to validate the performance of the proposed controller.

Voltage Regulation of an Isolated DC Microgrid with a Constant Power Load: A Passivity-based Control Design

Passivity-based nonlinear control for an isolated microgrid system is proposed in this paper. The microgrid consists of a photovoltaic array and a battery energy storage connected to a point of common converters, supplying a constant power load. The purpose of this control strategy is to maintain the output direct current voltage in its reference value under load variations, improving battery interaction. The system is represented by its state space averaged model and the proposed controller is designed using the interconnection and damping assignment strategy, which allows obtaining controller parameters while ensuring the closed-loop system stability. The unknown constant power load is estimated using an observer based on the energy function of the system. The behavior of the proposed control strategy is validated with simulation and experimental results.

Voltage regulation of buck converter with constant power load: An adaptive power shaping control

In this paper, the problem of voltage regulation of DC–DC buck converter with unknown constant power load (CPL) and input voltage is addressed. A power shaping controller (PSC) based on the passivity theory is proposed to stabilize this system. In addition, borrowing immersion & invariance (I&I) technique, an observer can be designed to estimate CPL and input voltage simultaneously. By combining PSC with I&I observer, an adaptive control scheme is achieved. Besides, the estimate of the domain of attraction is given to rigorously guarantee the convergence property by virtue of the invariant set theory. Then, the locally asymptotic stability of the closed-loop system is established. Finally, the simulation and experimental results show the effectiveness of the proposed control method.

Multiple-model adaptive control architecture for a quadrotor with constant unknown mass and inertia

This paper proposes an architecture based on a multiple-model solution for height and yaw control of a quadrotor transporting an unknown constant load, added before the flight. Estimates of the inertial parameters (mass and z-axis inertia) and state variables (vertical position, velocity, yaw angle and rate) are obtained using data from the onboard sensors. A Multiple-Model Adaptive Controller (MMAC) architecture is proposed. The control of each partial model is based on a steady state Linear Quadratic Regulator (LQR), using integrative action for the height control. The resulting system is validated with load variations of up to 10% of the vehicle mass, both in simulation and experimentally, resorting to an off-the-shelf commercially available quadrotor.

A Nonlinear Control Strategy for DC-DC Converter with Unknown Constant Power Load Using Damping and Interconnection Injecting

DC-DC converters with constant power loads are mostly used in DC microgrids. Negative impedance and large disturbances of constant power loads may lead to the instability of DC-DC converters. To address this issue, a nonlinear control strategy consisting of an improved passivity-based controller and nonlinear power observer is proposed in this paper. First, an improved passivity-based controller is designed based on the port-controlled Hamiltonian with dissipation model. By proper damping and interconnection injecting, the fast dynamic response of output voltage and stability of the DC-DC converter is achieved. Second, the constant power load is observed by a nonlinear power observer, which is adopted to estimate the power variation of the constant power load within a small settling time and improve the adaptability of the DC-DC converter under power disturbance. Finally, the simulation and experimental results are presented, which illustrate the proposed control strategy not only ensures the stability of the DC-DC converter under large disturbances, but also can track the desired operating point with low voltage overshoot in no more than 10 milliseconds.

Multiple-model control architecture for a quadrotor with constant unknown mass and inertia

This paper presents a methodology for height and yaw angle control of a quadrotor that transports an unknown constant load added before the flight. Based on measurements from the onboard sensors, estimates of inertial parameters – mass and z-axis inertia – and state variables – vertical position, velocity, yaw angle and rate – are provided resorting to Multiple-Model Adaptive Estimators. The number and worst case performance of Kalman filters is selected based on the Baram Proximity Measure. The proposed control methods are a steady state Linear Quadratic Regulator (LQR) with integrative action for the height, and an LQR controller for the yaw angle. The overall system obtained is validated with load variations of up to 10% of the vehicle mass, both in simulation and experimentally, resorting to an off-the-shelf commercially available quadrotor.

An Adaptive Observer-Based Controller Design for Active Damping of a DC Network With a Constant Power Load

This article explores a nonlinear, adaptive controller aimed at increasing the stability margin of a direct-current (dc), small-scale, electrical network containing an unknown constant power load (CPL). Due to its negative incremental impedance, this load reduces the effective damping of the network, which may lead to voltage oscillations and even to voltage collapse. To overcome this drawback, we consider the incorporation of a controlled dc–dc power converter in parallel with the CPL. The design of the control law for the converter is particularly challenging due to the existence of unmeasured states and unknown parameters. We propose a standard input–output linearization stage, to which a suitably tailored adaptive observer is added. The good performance of the controller is validated through experiments on a small-scale network.

Persistency of excitation and position-sensorless control of permanent magnet synchronous motors

In this brief, the exponential rotor position tracking/regulation problem for position-sensorless (nonsalient-pole surface) PMSMs with unknown constant load torque and stator resistance is addressed. The requirement of persistency of excitation conditions involving a non-definitely zero rotor speed reference is removed, owing to the design of an innovative (speed measurement-based) adaptive observer that relies on a local version of the persistency of excitation lemma and does not involve straightforward adaptations of previous ideas.

Energy shaping control for buck–boost converters with unknown constant power load

We develop in this paper an adaptive passivity-based controller for output voltage regulation of DC–DC buck–boost converter with an unknown constant power load. This control problem is theoretically challenging since the average model of the converter is a bilinear second order system that, due to the presence of the constant power load, is non-minimum phase with respect to both states. A solution to the problem was recently reported in Wei et al. (2017), however, the resulting control law is extremely complicated to be of practical interest. The purpose of this paper is to present a new, significantly simpler, controller that can be easily implemented in applications. The key modifications introduced in the new design are the use of a change of coordinates and a partial linearization that transform the system into a cascade form, to which an adaptive energy-shaping controller is applied. Another advantage of the proposed controller, besides its simplicity, is that it is amenable for the addition of an outer-loop PI that improves its transient and disturbance rejection performances. Simulations and experimental results are provided to assess the improved performance of the proposed controller.

A Consensus-Based Controller for DC Power Networks

In this paper we propose a new distributed passivity-based control scheme, achieving proportional (fair) current sharing and average voltage regulation in Direct Current (DC) power networks, with an arbitrary topology. The considered DC network is composed of several Distributed Generation Units (DGUs) interconnected through resistive-inductive power lines. Each DGU includes a generic energy source that supplies an unknown constant impedance load through a DC-DC buck converter. The proposed distributed control scheme achieves current sharing and average voltage regulation, independently of the initial condition of the controlled network, facilitating Plug-and-Play capabilities. Moreover, the proposed control strategy exploits a communication network to achieve current sharing using a consensuslike protocol. Global convergence to a desired steady state is proven and simulations show satisfactory performance.

Online Algebraic Identification Approach of Continuous Linear Time Delay Systems

AbstractIn this paper, we propose an online algebraic method to identify linear continuous time delay process from step response, in presence of unknown initial state and constant load disturbance. The identification mechanism is split into two sequential steps. The time delay and dynamic of the plant is estimated firstly through a spectral formulation. In the next stage, the transient regime is deduced from a linear regression. To improve the robustness of the proposed method, a local convolution by sigmoid function is proposed. Simulation results are provided, at last, to show the effectiveness of our conceived approach.

Inverters operation in rigid and autonomous grid

PurposeThe aim of this paper is to develop the method of optimal control of the three‐phase inverter system for autonomous and power grid operation. The presented method will also allow the cooperation of several inverters creating an autonomous network. This system should also be able to reduce demanded higher harmonics in power voltage according to the list of numbers of these harmonics. In this article the authors describe a system that is used to create a symmetrical three‐phase voltage. The supply power is taken from the renewal source. The inverter system as well as cooperation of several such systems to create an autonomous network is under consideration. The generated three‐phase voltage should be symmetrical even when the RL load is not symmetrical or else it changes in impulse. Cooperation of the system with the autonomous network is also under consideration. The task is to supply the set current of the basic harmonic to the power grid and possibly to reduce voltage higher harmonics on output terminals of the system.Design/methodology/approachThe method of optimal control for a quadratic objective function was applied.FindingsIn the autonomous system the presented method provides a symmetrical three‐phase voltage with an unknown unsymmetrical constant or pulsed load. When operating for a power grid the system provides the desired current related to the basic harmonic of the grid voltages. In both cases the demanded higher harmonics of the grid voltages are reduced.Originality/valueFilter of the main harmonic for the power grid voltage was applied. Applied numerical solutions and obtained simulations are also original.

An asymptotically stable sensorless speed controller for non‐salient permanent magnet synchronous motors

SUMMARYA solution to the longstanding problem of sensorless control of an electrical machine is provided in this paper. That is, the construction of an asymptotically stable controller that regulates the mechanical speed of the motor, measuring only the electrical coordinates. The result is presented for a non‐salient permanent magnet synchronous motor perturbed by an unknown constant load torque. The proposed scheme is a fourth order nonlinear observer‐based controller that does not rely on—intrinsically nonrobust—operations like open‐loop integration of the systems dynamical model nor signal differentiation and can be easily implemented in real time. The controller is easy to commission, with the tuning gains directly determining the convergence rates of the position, speed, and load torque observers. Simulation and experimental results are presented. In particular, a comparison with a sensorless field‐oriented controller, recently proposed in the drives literature, is carried out. Copyright © 2012 John Wiley & Sons, Ltd.

Observer-Based Speed Tracking Control for Sensorless Permanent Magnet Synchronous Motors With Unknown Load Torque

The tracking control problem is addressed for sensorless (nonsalient-pole surface) permanent magnet synchronous motors with unknown constant load torque. Assuming that only stator currents and voltages are available for feedback, a novel sixth order nonlinear adaptive control algorithm is designed, which does not rely on nonrobust open loop integration of motor dynamics and guarantees, under persistency of excitation, local exponential rotor speed tracking.

Sensorless Speed Control of Non–salient Permanent Magnet Synchronous Motors

AbstractIn this paper it is presented an asymptotically stable sensorless controller for a non–salient permanent magnet synchronous motor that is perturbed by an unknown constant load torque. The proposed scheme is a fourth order nonlinear observer–based scheme that does not rely on—intrinsically nonrobust—operations like open-loop integration of the systems dynamical model nor signal differentiation, and can be easily implemented in real time. The controller is easy to commission, with the tuning gains directly determining the convergence rates of the position, speed and load torque observers. Experimental results that illustrate the usefulness of the scheme are presented.