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Parkinson’s disease (PD) is responsible for a broad spectrum of signs and symptoms, including relevant motor impairments generally rated by clinical experts. In recent years, motor measurements gathered by technology-based systems have been used more and more to provide objective data. In particular, wearable devices have been adopted to evidence differences in the gait capabilities between PD patients and healthy people. Within this frame, despite the key role that the upper limbs’ swing plays during walking, no studies have been focused on their harmonic content, to which this work is devoted. To this end, we measured, by means of IMU sensors, the walking capabilities of groups of PD patients (both de novo and under-chronic-dopaminergic-treatment patients when in an off-therapy state) and their healthy counterparts. The collected data were FFT transformed, and the frequency content was analyzed. According to the results obtained, PD determines upper limb rigidity objectively evidenced and correlated to lower harmonic contents.

The transient stabilization and voltage regulation problem for a synchronous generator connected to an infinite bus is addressed, in this technical note, in the presence of all uncertain physical parameters. First, new interpretations for the Desensitized Four Loops Regulator, here referred to as robust coordinated PSS-AVR (Power System Stabilizer & Automatic Voltage Regulator), are derived in terms of minimum phase properties with respect to a suitably chosen output for the linearized error system. Secondly, on the basis of such an output, a nonlinear generalization of the robust coordinated PSS-AVR is designed with the aim of enlarging the stability region and improving the transients about the unpredictable operating conditions determined by the faults. Its linear action coincides with the one provided by the robust coordinated PSS-AVR: the compelling simplicity of control structure (just one integrator is involved) and robust tuning procedure of the linear design are definitely inherited, with, additionally, no use of the mechanical input power. A numerical analysis along with realistic simulations confirm improved stability when the proposed nonlinear controller is applied.

Extended Kalman Filters (EKFs), Phase Locked Loops (PLLs), and Stator Flux Observers (SFOs) are widely used for sensorless control of Permanent Magnet Synchronous Motors (PMSMs) drives. Their use (in their most advanced version) is here extended, on the basis of model analogies and suitably-guaranteed closed loop stability properties, to the sensorless speed regulation control of Hybrid Stepper Motors (HSMs), in which position and speed sensors are not employed to reduce costs and increase robustness with respect to high temperature and high-vibration environments. Both realistic simulations and experimental results demonstrate the feasibility of the proposed methods in terms of closed-loop performance and robustness to parameters mismatch.

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.

A harmonically self-similar temporal partition, which turns out to be subtly exhibited by elite swimmers at middle distance pace, is formally defined for one of the most technically advanced swimming strokes—the butterfly. This partition relies on the generalized Fibonacci sequence and the golden ratio. Quantitative indices, named ϕ-bonacci butterfly stroke numbers, are proposed to assess such an aforementioned hidden time-harmonic and self-similar structure. An experimental validation on seven international-level swimmers and two national-level swimmers was included. The results of this paper accordingly extend the previous findings in the literature regarding human walking and running at a comfortable speed and front crawl swimming strokes at a middle/long distance pace.

A master–slave synchronisation control problem is addressed for current-fed DC and permanent magnet synchronous motors with all uncertain parameters. A measurable exogenous rotor position reference signal, which belongs to the class of biased sinusoidal signals with uncertain bias, amplitude, angular frequency, phase, is to be tracked without assuming its a priori knowledge. An innovative modification of disturbance cancellation techniques allows to prove that an output feedback adaptive nonlinear control scheme, which simply generalises the classical internal-model-based input law, solves the aforementioned problem, with an overall stability proof concerning the entire closed-loop system. The practical effectiveness of the proposed approach is illustrated by experimental results.

New sensorless observers (i.e., from stator currents/voltages measurements only), to be included into a simple observer-based sensorless control for the tracking of non-definitely zero speed references in nonsalient-pole surface permanent magnet synchronous machines (PMSMs), are proposed. They are obtained through a “minimum distance” modification from recently presented position-sensorless observers (i.e., from rotor speed and stator currents/voltages measurements only). The rotor speed estimate is here directly provided by the phase locked loop (PLL)-based third-order steady-state linear kalman filter (SSLKF) that has been previously used to mitigate the distortions on the estimated position. Experimental results illustrate the effectiveness of the proposed approach in a speed sensor fault-tolerant scenario.

The experimental comparison of two different global learning position controls (namely, “adaptive learning” and “repetitive learning” controls) for hybrid step motors performing repetitive tasks has been recently presented in the literature. Related benefits and drawbacks have been successfully analyzed on the same robotic application. However, the design of the two aforementioned learning controls—though relying on a rigorous stability analysis—are based on a simplified current-fed model of the motor. They cannot achieve precise current tracking due to the mere presence of proportional-integral (PI) control actions in the outer current control loops. The aim of this paper is to enrich and update the results of the aforementioned comparison in the light of the latest contributions that generalize the theoretical design to the full-order voltage-fed motor models of hybrid step motors. Learning actions are now included in the outer current control loops: They generalize the corresponding PI actions to the periodic scenario and allow to solve a control problem whose solution was seeming very difficult to be obtained.

This paper moves in the context highlighted in the recent literature, in which full and partial rotor speed sensor faults in induction motors with uncertain parameters can be detected by a single adaptive observer. Certain relevant experimental evidences concerning the use of such single adaptive observer in the aforementioned context, however, are yet to be theoretically motivated. Such evidences go beyond the already presented analyses and refer to the convergence of the resulting observer estimates under generating operations. In this paper, we present an algebraic equations-based analysis that extends any previous one, by providing a definite answer to the above question. It simultaneously clarifies any structural intrinsic limitation that is related to previously proposed approaches. The key point relies on deriving the explicit expressions for two admissible motor model solutions, which are characterized by the same output (rotor speed and stator currents) and input (stator voltages) profiles and whose existence is definitely linked to the adaptive observer behaviour in speed sensor fault detection scenarios.

1Simple adaptations of the latest design ideas in [2] suggest the existence of a new observer to be used for sensorless speed control of (nonsalient-pole surface) permanent magnets synchronous machines. The rotor speed measurement-assumed to be measured in [2] by a low-resolution transducer providing a single pulse per revolution — is here replaced by the output of a PLL (Phase Locked Loop) block that is based on a third-order Steady-State Linear Kalman Filter (SSLKF). Experimental results concerning the new observer are provided.

The original contribution of this paper, which concerns induction motors with uncertain constant load torque and rotor/stator resistances, is twofold. The first innovative contribution relies on the experimental analysis of the latest theoretically-based sensorless/output feedback solutions to the problem of tracking rotor speed and flux modulus reference signals with the simultaneous estimation of the uncertain parameters. The second novel contribution is constituted by the proof of existence for a new adaptive local flux observer from rotor speed and stator currents/voltages, which, in its full-order or reduced-order-like versions, involves neither over-parameterizations nor non-a priori verifiable first order stator resistance identifiability conditions at steady-state.

The heart rate can be effectively used as a measure of the exercise intensity during long duration cycle-ergometer exercises: precisely controlling the heart rate (HR) becomes crucial especially for athletes or patients with cardiovascular/obesity problems. The aim of this letter is to experimentally show how the nonlocal and nonswitching nonlinear control that has been recently proposed in the literature for the HR regulation in treadmill exercises can be effectively applied to cycle-ergometer exercises at constant cycling speed. The structure of the involved nonlinear model for the HR dynamics in cycle-ergometer exercises is mathematically inspired by the structure of a recently identified and experimentally validated nonlinear model for the HR dynamics in treadmill exercises: the role played by the treadmill speed is played here by the work load while the zero speed case for the treadmill exercise is here translated into the cycling operation under zero work load. Experimental results not only validate the aforementioned nonlinear model but also demonstrate the effectiveness--in terms of precise HR regulation--of an approach which simply generalizes to the nonlinear framework the classical proportional-integral control design. The possibility of online modifying the HR reference on the basis of the heart rate variability (HRV) is also suggested and experimentally motivated.

Permanent-magnet step motors offer several advantages such as high efficiency, high power density, high torque-to-inertia ratio, and excellent durability and serviceability, as well as the absence of external rotor excitation and windings. The nonuniformity in the developed torque due to the nonsinusoidal flux distribution in the airgap is, however, the major obstacle in achieving global high-precision position tracking. When the position reference profile is a periodic signal of known period, such an obstacle may be however overcome by using recent learning control techniques, which require neither high gains in the inner speed/position control loops nor resetting procedures. An experimental comparison of two different recently designed learning position controls (“adaptive” and “iterative”) is, for the first time, carried out with reference to the same low-speed robotic application. Benefits and drawbacks of the two learning approaches are analyzed in detail.

SUMMARY In this brief note, we consider the transient stabilization and voltage regulation problem for a synchronous generator connected to an infinite bus. We show how a much simpler output feedback controller, compared with previous results, can be obtained if a different stability analysis is carried out: a suitable change of coordinates is performed so that advantageous triangularity properties of the regulation error dynamics are highlighted. A novel first order estimator for the uncertain mechanical input power is designed: it is the only adaptation scheme used by the controller. The innovative crucial step in the presented control design relies on relaxing the constraint imposed by the typically (previously) adopted back-stepping techniques and constituted by the required availability of the regulation/tracking error variables: the converging estimate of the mechanical input power directly becomes the reference value for the electrical power and allows for the straightforward computation of the uncertain power angle constant value guaranteeing voltage regulation at steady state. Copyright © 2011 John Wiley & Sons, Ltd.

We address the tracking control problem for sensorless (nonsalient-pole surface) permanent magnet synchronous motors with unknown constant load torque. On the basis of stator current and voltage measurements only and without relying on nonrobust open loop integration of motor dynamics, a novel sixth order nonlinear adaptive control algorithm is designed, which guarantees, under persistency of excitation, local exponential rotor speed tracking. Simulation results illustrate the closed loop performance and show the effectiveness of the proposed solution even in the presence of current sensor noise and stator resistance variations.

The position estimation problem is addressed for (nonsalient-pole surface) permanent magnets synchronous machines. Rotor speed and stator currents/voltages measurements are assumed to be available for feedback. Two novel adaptive observers are compared and experimental results concerning pump-fan and generating applications are provided.

A master-slave synchronization control problem is addressed for current-fed permanent magnets synchronous machines with uncertain parameters and no speed sensor. An exogenous rotor position reference signal, which belongs to the class of biased sinusoidal signals with uncertain bias, amplitude, angular frequency, phase, is to be tracked without assuming its foreknowledge. An innovative output feedback adaptive nonlinear control scheme, which solves the aforementioned problem and simply generalizes the classical internal model-based input law, is presented. The effectiveness of the proposed approach is validated by experimental results.

In this paper we show that, when the rotor position is not measured in (nonsalient-pole surface) PMSMs with unknown constant load torque and stator resistance (with the rotor speed being available along with the stator currents), it is possible to guarantee exponential rotor position tracking and — mainly — regulation without resorting to persistency of excitation conditions which involve a non-definitely zero rotor speed reference. A new output feedback control is accordingly designed, which relies on a novel adaptive observer. The only price to be paid is constituted by a non-constant reference for the stator current vector d-component.

Repetitive space-learning controls are designed for current-fed uncertain permanent magnet step motors with non-sinusoidal flux distribution (the family of permanent magnet synchronous motors with cogging torque is allowed as a special case). Either semi-global rotor speed tracking is asymptotically achieved or local rotor position tracking is asymptotically guaranteed without requiring the time-periodicity of the corresponding reference signals. Simulation results illustrate the effectiveness of the presented approach in a typical electric drive control scenario, even in the presence of stator current dynamics which have been neglected at the design stage.

It has been recently shown in the literature that a robust output feedback controller for the heart rate regulation can be designed for an experimentally validated second order nonlinear model of the human heart rate response during long-duration treadmill exercises: It is based on piecewise linear approximations of the original nonlinear model and involves (local) robust linear control techniques. In this letter, we resort to recent nonlinear advanced control techniques in order to illustrate the existence of a nonlocal and nonswitching control which guarantees heart rate regulation with no exact knowledge of model parameters and nonlinearities: It simply generalizes to the nonlinear framework the classical proportional-integral control design for linear models of heart rate response during treadmill exercises. Simulation and experimental results demonstrate the effectiveness of the proposed approach in typical training exercises involving warm up/holding/cool down phases.

International audience; The robust transient stabilisation problem (with stability proof) of a synchronous generator in an uncertain power network with transfer conductances is rigorously formulated and solved. The generator angular speed and electrical power are required to be kept close, when mechanical and electrical perturbations occur, to the synchronous speed and mechanical input power, respectively, while the generator terminal voltage is to be regulated, when perturbations are removed, to its pre-fault reference constant value. A robust adaptive nonlinear feedback control algorithm is designed on the basis of a third-order model of the synchronous machine: only two system parameters (synchronous machine damping and inertia constants) along with upper and lower bounds on the remaining uncertain ones are supposed to be known. The conditions to be satisfied by the remote network dynamics for guaranteeing L2 and L∞ robustness and asymptotic relative speed and voltage regulation to zero are weaker than those required by the single machine-infinite bus approximation: dynamic interactions between the local deviations of the generator states from the corresponding equilibrium values and the remote generators states are allowed.

The transient stabilization problem of a synchronous generator in a multimachine power system is addressed. A robust adaptive nonlinear feedback control algorithm is designed on the basis of a third order model of the synchronous machine in a multimachine power network which takes into account the effect of transfer conductances and of the remote network dynamics: it does not require the machine internal voltage measurement and relies on the knowledge of only three model parameters and of upper and lower bounds on the uncertain ones. Sufficient conditions to be satisfied by the remaining part of the network for guaranteeing L2 and L∞ disturbance attenuation and relative speed regulation are derived which are more general than those required by the single machine-infinite bus approximation.

International audience; The robust transient stability problem of a synchronous generator in an uncertain power network with transfer conductances is addressed. A robust adaptive nonlinear feedback control algorithm is designed on the basis of a third order model of the synchronous machine: only two system parameters (synchronous machine damping and inertia constants) along with upper and lower bounds on the remaining uncertain ones are supposed to be known. The conditions to be satisfied by the remote network dynamics for guaranteeing L 2 and L ∞ robustness and asymptotic relative speed regulation to zero are weaker than those required by the single machine-infinite bus approximation.