Marcello Montanari

Speed Sensorless Control of Induction Motors Based on a Reduced-Order Adaptive Observer

A novel speed sensorless indirect field-oriented control for the full-order model of the induction motor is presented. It provides local exponential tracking of smooth speed and flux amplitude reference signals together with local exponential field orientation, on the basis of stator current measurements only and under assumption of unknown constant load torque. Speed estimation is performed through a reduced-order adaptive observer based on the torque current dynamics, while no flux estimate is required for both observation and control purposes. The absence of the flux model in the proposed algorithm allows for simple and effective time-scale separation between the speed-flux tracking error dynamics (slow subsystem) and the estimation error dynamics (fast subsystem). This property is exploited to obtain a high performance sensorless controller, with features similar to those of standard field-oriented induction motor drives. Moreover, time-scale separation and physically-based decomposition into speed and flux subsystems allow for a simple and constructive tuning procedure. The theoretical analysis based on the singular perturbation method enlightens that a persistency of excitation condition is necessary for the asymptotic stability. From a practical viewpoint, it is related to the well-known observability and instability issues due to a lack of back-emf signal at zero-frequency excitation. A flux reference selection strategy has been developed to guarantee Persistency of excitation in every operating condition. Extensive simulation and experimental tests confirm the effectiveness of the proposed approach.

Control of a camless engine electromechanical actuator: position reconstruction and dynamic performance analysis

Camless internal combustion engines offer major improvements over traditional engines in terms of efficiency, maximum torque and power, and pollutant emissions. Electromechanical valve actuators are very promising in this context, but they present significant control problems. Further, to keep system cost at an acceptable level, a control system without a valve position sensor needs to be adopted. Low valve seating velocity, small transition time for valve opening and closing, and unavailability of position sensor are conflicting objectives that need to be jointly considered. In this paper, a control system architecture is presented, capable of dealing with all these issues. It is shown that a position tracking controller is needed: a key point is the design of the reference trajectory to be tracked. Actuator physical limitations strongly influence the feasible trajectory when low valve seating velocity is required, thus affecting valve transition time. Owing to the same limitations, valve electromagnets have to be energized for a significant part of the trajectory, thus allowing valve position reconstruction starting from electrical measurements only. A method for position reconstruction is presented, which makes use of auxiliary coils to reconstruct electromagnets fluxes; it is shown via sensitivity analysis that the functional characteristics of position reconstruction and its accuracy are compatible with the required applications. The trajectory design is then addressed as an optimization problem that explicitly considers the tradeoff between fast dynamic performance and system robustness. The solution of this optimization problem enlightens the limitations on achievable dynamic performance, which are presented and discussed.

Sensorless control of induction motor with adaptive speed-flux observer

A novel sensorless controller for induction motor is presented. Indirect field oriented control approach and Lyapunov-adaptive design are exploited for the derivation of the controller and the speed-flux observer constituting the proposed solution. No direct integration of the neutrally stable stator flux dynamics is adopted. Persistency of excitation conditions with clear practical interpretation is derived to guarantee local exponential stability with a defined region of attraction for the proposed approach. Simulation results are provided.

Modelling of a Car Driveline for Servo-Actuated Gear-Shift Control

A physically-based dynamic model of the drive- line of a vehicle with automated manual transmission (AMT) is presented. The driveline is decomposed into three main subsystems: the drivetrain, constituted by the transmission shafts connecting the engine to the wheels, and two electro- hydraulic actuators for clutch and gear-box control. The main feature of the model proposed is to consider in a detailed way both the nonlinear dynamics of the clutch and gear-box actuators and the drivetrain behavior. Model parameter identification is obtained both through theoretical relations and experimental tests. By means of experiments, it is shown that the proposed model is able to describe the main phenomena characterizing the driveline dynamics.

Sensorless indirect field-oriented control of induction motors, based on high gain speed estimation

A novel speed sensorless control algorithm for IM with analytically proven local asymptotic stability properties is presented. It provides asymptotic speed tracking and flux regulation under condition of constant load torque. Conditions of persistency of excitation are defined; they coincide with the well-known nonzero excitation frequency of IM. Intensive experimental study demonstrates performance suitable for wide spectrum of technological applications.

Trajectory generation for camless internal combustion engine valve control

Camless internal combustion engines offer major improvements over traditional engines in terms of efficiency, maximum torque and power, pollutant emissions. Electromechanical valve actuators are very promising in this context, but still present significant control problems. Low valve seating velocity, small transition time for valve opening and closing, unavailability of position sensor are the main objectives to be considered in the design of the valve control system. Actuator physical limitations strongly influence the feasible trajectory when low valve seating velocity is required, thus affecting valve transition time. One key point for the control is the design of the reference trajectory to be tracked by the closed loop controller. In this paper, the trajectory design is addressed, solving an optimization parametric problem that explicitly considers the physical constraints and the trade-off between fast dynamic performance and system robustness.

Sensorless Control of Induction Motors based on High-Gain Speed Estimation and On-Line Stator Resistance Adaptation

Stator resistance adaptation is a crucial issue in sensorless control of induction motor, particularly at low speed. In this paper, an improved indirect field oriented controller based on high gain speed estimation, which was previously proposed by the authors, is deeply revised in order to add a stator resistance adaptation mechanism. Simplicity and easy-to-tune structure of the non-adaptive version of the controller is preserved, while its robustness is significantly improved thanks to stator resistance estimation. Experimental results are provided to show the effectiveness of the proposed method

LEARNING CONTROL OF CURRENT-FED INDUCTION MOTOR WITH MECHANICAL UNCERTAINTIES

Abstract In this paper repetitive learning control technique has been applied to the position/flux tracking control of an Induction Motor (IM) under hypothesis of periodic reference trajectory and uncertainties on the mechanical model. The electro-magnetic IM model has been directly taken into account in the control development. Indirect Field Oriented approach has been exploited and combined with control actions derived from Lyapunov-like design. In order to compensate the periodic disturbances, the model of a generic periodic signal with known period has been embedded in the controller with a suitable update rule. The convergence properties of the overall solution proposed have been formally proven. Simulation results confirm the validity of the approach presented.

Hybrid optimal control of an automated manual transmission system

Abstract In this paper, on the basis of a simplified hybrid model of an Automated Manual Transmission (AMT) system with servo-actuated clutch and gearbox, the control strategy for the gearshift is formally addressed as a hybrid optimal control problem and solved by means of numerical optimization method. The gear upshift request is performed with locked clutch and achieving the synchronization of the requested gear by exploiting engine cut-off and properly controlling the engine and the gearbox. Performance achievable with the proposed strategy under various vehicle conditions and engine regimes are shown.

Induction motor model identification via frequency-domain Frisch scheme

Abstract In this paper the frequency domain version of the Frisch identification scheme is applied to identify parameters of the continuous-time model of an induction motor. A formulation of the identification problem in the errors-in-variables framework is given, in particular this formulation allows handling of periodic signals affected by noises with stochastic properties. A new approach, based on Bilinear Matrix Inequalities, is introduced to estimate noise variances of measured signals in the Frisch scheme. Simulations and experimental results are reported to show the properties of the proposed approach.