This study attempts to address the angular velocity regulation problem associated with quadcopters under constraints such as model-plant mismatch, uncertain loads, and limited measurement capability. The proposed solution is an output-feedback structure that includes an angular velocity observer, active damping, and a disturbance observer to enhance the performance of the closed-loop system, which provides the following features: first, the model-free observer yields estimates of angular velocities by stabilizing the diagonalized error dynamics; second, the output-feedback double integral control with feed-forward compensation terms stabilizes the angular velocity errors while satisfying a predetermined critically damped performance. An experimental platform provided by Quanser demonstrates the effectiveness of the proposed technique.

This paper proposes an observer-based output feedback controller that enforces triply damped dynamics in servo drives. This makes transients softer as well as the model less dependent. The primary contributions are as follows: (a) The observer gain, structured by virtual damping (VD) and a convergence rate, enables the estimation loop to be governed by a first-order transfer function without requiring any system model information; (b) a high-order disturbance observer (HODOB) exponentially estimates high-frequency disturbances in accordance with the triple-damping transfer function; and (c) a proportional–integral-type controller based on the observer and HODOB, incorporating VD terms, guarantees exponential recovery of the desired triply damped performance. Experimental results on a commercial servo drive confirm the practical effectiveness of the proposed method across varying load conditions.

This article proposes a multiloop feedback system that utilizes the virtual damping (VD) injection technique to ensure critically damped input–output behavior for each quadcopter in a multiagent topology. The proposed framework also considers system nonlinearity and model–plant mismatches to ensure robustness while maintaining a simple proportional–derivative (PD) controller design for convenient industrialization. The benefits of the proposed system are threefold. First, the observer allows both the outer and inner loops to feed back the time-derivative components of the position and attitude measurements, without requiring any system model information. Second, the PD-type adaptive controllers for each loop incorporate observer-based VD components into the feedforward and feedback loops to attenuate disturbances. Third, based on a nonlinear combination of two design parameters for VD and the desired convergence rate, the critically damped transfer function for the closed loop is determined using the order-reduction technique. A hardware testbed with the three quadcopters confirmed the practical advantages of the proposed solution in maintaining specified formations.

This paper is concerned with the problem of robustly estimating the speed and acceleration of servo drives without the system model parameter information, depending on only the order of the open-loop system. The proposed filtering solution incorporates the disturbance observer (DOB) into the second-order pole-zero cancellation (PZC) observer. The main contributions fall into three parts. First, the model-free Luenberger observer as the first subsystem specifies its gain structure in the nonlinear form to invoke the second-order PZC. Second, the first-order nonlinear DOB as the second subsystem estimates the high-frequency disturbance to yield the compensation term for the second-order PZC observer. Third, the combination of these two subsystems eventually results in the diagonalized estimation error dynamics, which makes the performance adjusting process more convenient for field engineers. The experimental study confirms the effectiveness of the proposed filtering solution using a 500-W brushless DC (direct current) motor-based servo drive under various operation modes.

This study considers both a robot and its actuator dynamics to construct a performance recovery controller for rover vehicle applications. The resultant controller structures the simple single loop forms for linear velocity and yaw angle measurements, equipping the feed-forward compensators against disturbances caused by uncertainties of the motion equations. The salient aspects of this paper are (a) the order reduction observers estimate the velocities and accelerations independent from the motion equations; the simple observer-based order reduction output-feedback controller forms the proportional-integral-derivative and proportional-integral-double derivative with the nonlinearly structured gains; and (c) the closed-loop system guarantees to recover the closed-loop responses to the first-order desired system exponentially. A prototype rover vehicle with a MyRIO1900 processor validates the practical benefits of these three novelties above.

This article addresses the filtering of position, speed, and acceleration in servo motor applications by confronting practical challenges such as model dependence, complex matrix computations, and inconsistent performance. The proposed filter is systematically derived through the integration of a disturbance observer (DOB) design and a high-order pole–zero cancellation (PZC) technique, yielding the following contributions. First, a double-integral, offset-free position filter reduces the order of the filtering error dynamics by employing nonlinearly parameterized gains. Second, the combination of the DOB-based system with these gains facilitates the design of speed and acceleration filters based on filtered position measurements. Third, the diagonalization of the filtering error dynamics via nonlinear gain parameterization simplifies the tuning process for desired performance. The experimental validation using a 500-W brushless dc motor-based dynamometer demonstrates a 27% improvement in feedback system performance compared to a well-tuned extended state observer (ESO).

The proposed cascade-type feedback system stabilizes the terminal voltage of single machine infinite bus (SMIB) systems using two measurements: power angle and terminal voltage. The resultant control law only requires the nominal system parameters of the SMIB, and the observer removes any model dependence. This paper provides several contributions. First, the high-order pole-zero cancellation (PZC) technique constructs the observer to estimate the time derivatives of the terminal voltage and power angle measurements without any SMIB model information. Second, the high-order PZC technique enables the outer loop to estimate the desired power angle reference along the critically damped dynamics for the terminal voltage. Third, the observer-based proportional-double integral-derivative control law for the inner loop exponentially stabilizes the power angle error by reducing the closed-loop order to 2 through the high-order PZC technique. A MATLAB/Simulink implementation of the proposed cascade-type feedback system validates the effectiveness of the proposed solution.

This paper presents a novel filtering solution for servo system applications to extract the speed and acceleration information from the imperfect angle measurement. The proposed solution forms a cascade-type structure without using plant information, including its structural and parameter information, with the following contributions: (a) an improved disturbance attenuation capability incorporating the nonlinearly structured filter gain into the extended state observer and (b) a simple performance tuning process that does not involve matrix algebra to determine the desired filtering gain due to the filtering error dynamics diagonalization by the pole-zero cancellation technique. Moreover, the closed-loop filtering dynamics are rigorously analyzed, and various experiments validate the feasibility of the proposed solution.

This article exhibits a current controller guaranteeing the performance recovery property despite the parameter uncertainties for interior-mounted permanent magnet synchronous motors (IPMSMs). The contributions of the proposed method are as follows. The first one is to build the current control law for the closed-loop system to asymptotically recover the target current tracking performance, while estimating the unknown parameters. The second one is to present a systematic way assigning the optimal control gains by solving an optimization problem. The third one is to rigorously analyze the internal dynamics problem caused by the speed dynamics of IPMSMs. The efficacy of the proposed method is verified by conducting experiments where the proposed method is applied to a 5-kW IPMSM.

This article exhibits a novel solution to the speed tracking problem of permanent magnet synchronous motors (PMSMs) subject to parameter and load uncertainties. The resultant cascade structured solution is designed to give the speed tracking capability to the closed-loop system, which depends on only the nominal PMSM parameter information. This article provides two novel contributions: 1) a variable performance target system describing the desired perfect tracking nature with boosting feedback gains and 2) a robust control law forcing the target tracking system to be invariant through the utilization of active-damping pole-zero cancellation and disturbance observer techniques. The prototype 1-kW PMSM experimental set confirms the practical advantages of the proposed system compared to the recent autotuning controller.

In this article, we exhibit an order reduction output-feedback attitude stabilization scheme for 2-degree-of-freedom (2-DOF) helicopters by considering system nonlinearity and parameter variations in the controller and observer design tasks. As the first merit, the proposed observer for the angular velocity contains the disturbance estimation mechanism as a subsystem assisting the main estimator, which is independent of the system parameter information. As the second advantage, the resultant observer renders it possible to design an improved proportional-derivative-type controller that includes the active damping term and nonlinearly structured design parameters, reducing the closed-loop system order to 1. The Quanser 2-DOF helicopter system experimentally validates the practical merit of the proposed technique.

This paper develops an observer-based positioning scheme for ball-beam systems considering actuator dynamics. The practical constraints are handled systematically, including the mechanical dynamical nonlinearities, mismatched load disturbances, and parameter uncertainties. This result provides contributions as follows. First, parameter-independent observers exponentially estimate the ball velocity, motor speed, and its acceleration to remove the velocity, motor speed, and current feedback. Second, the auto-tuner automatically adjusts the desired closed-loop input-output behaviors to update its cut-off frequency in the transient operations. Third, observer-based active damping injection reduces the closed-loop ball position and actuator speed dynamics to 1 by pole-zero cancellation. Finally, disturbance observers act as a dynamic compensator by estimating the disturbances from model-plant mismatches such as dynamic nonlinearities, mismatched load disturbances, and parameter variations. The experimental study verifies the applicability of the proposed technique using the Quanser Ball-Beam hardware driven by an SRV02 servomotor.

In this paper, a robust output voltage-tracking algorithm is proposed for dc/dc boost power conversion systems based on a variable invariant manifold. A systematic multivariable approach, considering not only nonlinearity but also the parametric uncertainties, is used for deriving the control law. The proposed method has two features. First, a variable cut-off frequency algorithm is constructed to automatically adjust the invariant manifold, improving the transient output voltage-tracking performance. Second, nonlinear disturbance observers are introduced to enable the control law to exponentially recover the desirable tracking performance without any offset errors in the variable invariant manifold. The performance of the proposed technique is experimentally confirmed with a 3-kW dc/dc boost power conversion system.

In this article, the position-tracking problem for magnetic levitation (MAGLEV) systems is addressed by handling the model nonlinearities and uncertainties of parameters and loads. The first feature is devising a variable cut-off frequency algorithm enhancing the transient tracking performance by updating the feedback gain accordingly. The second is introducing the disturbance observer (DOB) improving the disturbance attenuation performance with the offset-free property, which corresponds to the replacement of tracking error integrators. The simulation results numerically demonstrate the effectiveness of the proposed technique considering model-plant mismatches and load variations.

This paper suggests a position-tracking algorithm for the outer-loop through the invariant dynamic surface approach for balancing robot applications. The main feature is to devise a dynamic surface representing the target position-tracking performance with variable cut-off frequency. The proposed controller makes the dynamic surface invariant while updating the closed-loop cut-off frequency accordingly with the self-tuner. The closed-loop properties are rigorously analyzed. The experimental verification result shows that the proposed controller establishes the 48% enhancement of the circular tracking performance in comparison with the feedback linearization method, where the LEGO Mindstorms EV3 is used.

This letter devises a novel signal-filtering technique subject to the feedback structure without the exact source signal dynamics information. The main idea of this result is comprised of two parts: first, the combination of the Luenberger and disturbance observer design techniques to improve the disturbance rejection capability in the feedback structure; second, the closed-form filtering gain-boosting mechanism updating the gain into the direction of the filtering error reduction. It is experimentally confirmed that the proposed filter contributes to lowering the current regulation performance degradation level from the filtering performance improvement using a 500-W permanent-magnet synchronous motor driven by the three-phase inverter.

In this article, we deal with the one-step time-delay problem in power converter and motor drive system applications implemented by the digital signal processor. For these wide applications, a novel one-step time-delay compensation algorithm is proposed, comprising a standard Luenberger-type observer including a learning algorithm and disturbance observer (DOB). The first novelty is to suggest the learning algorithm automatically determining the observer feedback gains according to the estimation error magnitude. The second is to introduce DOBs with estimation error integrators for removing the steady-state estimation errors, removing the additional adaptive and nonlinear damping compensation terms. The closed-loop observer behaviors are rigorously analyzed to present useful properties. The experimental data obtained using a 3-kW prototype dc-dc boost converter validates the effectiveness of the proposed algorithm.

In this paper, a robust position tracking controller is proposed using an invariant dynamic surface approach in a cascade control system structure. There are two main contributions. The first is to design a dynamic surface giving the desired tracking-performance with a time-varying cutoff frequency automatically adjusted by the proposed auto-tuner, which can enhance the reliability of the resulting control system. The second is to derive the inner- and outer-loop control laws driving the closed-loop trajectories to the dynamic surface, incorporating a disturbance observer with the use of only nominal plant parameters. A reduction of plant parameter dependence can be accomplished by the second contribution. The realistic simulation results confirm the advantages of the proposed technique.