Luca Peretti

Design and Implementation of Model Predictive Control for Electrical Motor Drives

This paper deals with a model predictive control (MPC) algorithm applied to electrical drives. The main contribution is a comprehensive and detailed description of the controller design process that points out the most critical aspects and also gives some practical hints for implementation. As an example, the MPC is developed for a permanent-magnet synchronous motor drive. Speed and current controllers are combined together, including all of the state variables of the system, instead of keeping the conventional cascade structure. In this way, the controller enforces both the current and the voltage limits. Both simulation and experimental results point out the validity of the design procedure and the potentials of the MPC in the electrical drive field.

Online MTPA Control Strategy for DTC Synchronous-Reluctance-Motor Drives

This paper presents an online procedure for the automatic search of the maximum-torque-per-ampere operating region for a synchronous reluctance motor. The algorithm is based on a signal-injection method with a random-based perturbation pattern applied to a common direct-torque-controlled drive. Among motor parameters, only the stator resistance is required to perform the automatic procedure. Simulations and experimental results are presented in the paper, demonstrating the benefits of the proposed algorithm. The solution is easily extended to any ac drive.

Parameter Sensitivity Analysis of an ImprovedOpen-Loop Speed Estimate forInduction Motor Drives

In the last decades, several schemes have been proposed for speed-sensorless control of induction motor drives. Promising approaches are closed-loop observers, as model reference adaptive systems (MRAS) and Kalman filters, and open-loop estimators, which have recently aroused lively interest because of their simplicity and low-cost profile. As known, open-loop algorithms use only motor equations to derive the speed estimation, whose accuracy turns out to be strictly related to the motor model and its parameters. This paper presents an improved open-loop speed estimation algorithm, which uses reference voltages and measured currents, after that a state-of-the-art dead time compensation has been performed. The often undervalued topic of parameter sensitivity is handled by an accurate mathematical investigation, confirmed by a complete set of both simulated and experimental results. The estimated speed is then used as feedback signal in a closed loop speed control, and a performance evaluation is accomplished as well.

Real-time Ethernet networks for motion control

Communication networks have been traditionally employed in motion control applications, especially within factory automation systems. While in the past they were merely used to exchange non time critical data (e.g. parameters and configuration data) nowadays they allow for much more powerful performance. In particular, the recently introduced Real-time Ethernet (RTE) networks, have been explicitly designed in order to cope with very tight timing constraints in terms of both determinism and real-time. In this paper we focus on two popular RTE networks, namely Ethernet POWERLINK and EtherCAT, and provide an example of their employment for a coordinated motion control application. In particular, we consider the tracking of a circular trajectory by the coordinated motion of two independent axes where the velocity set-points are transmitted to the electrical drives implementing the axis control by means of the RTE networks. After providing some essential features of the two networks, we describe the configurations adopted for the coordinated motion control application. Then we check the effectiveness of the solution proposed by means of numerical simulations which take into consideration possible error scenarios deriving from the adoption of the communication networks such as transmission errors, communication delays and cable breaks.

Speed measurement algorithms for low-resolution incremental encoder equipped drives: a comparative analysis

Precise motion control requires high-accuracy and high- bandwidth feedback speed information, often calculated by direct measurement of the rotor position available through the incremental encoder equipping the drive. The resolution of the encoder heavily affects the cost of the drive and the accuracy and bandwidth of the calculated speed. The limitations introduced by a low resolution encoder can be partially reduced by a proper speed calculation (or estimation) algorithm, that therefore plays a key role in modern drive systems. In this paper a comparative analysis of state-of-art speed measurement and estimation algorithms suitable for low-resolution incremental encoder equipped drives is presented, aiming at highlighting the specific feature of each one, both from the performance point of view, and from the computational requirements needed for actual implementation. The paper proposes itself as a guide for engineers in the complex choice of the best solution for each application.

Repetitive-Control-Based Self-Commissioning Procedure for Inverter Nonidealities Compensation

High-performance sensorless ac drives require the exact knowledge of the motor phase voltages in the whole speed range. The use of voltage sensors may be eschewed if the reference voltage signals, generated by the control algorithm, can be used instead. To this aim, an accurate compensation of most of inverter nonidealities is essential. This paper presents a novel self-commissioning procedure for the cancellation of inverter nonidealities, based on repetitive control. The main advantage is that the compensation generated by the procedure automatically includes the insulated-gate bipolar transistor parasitic effects during current zero-crossing, whose exact knowledge is one of the major problems in most of the standard dead-time cancellation techniques. Despite its elaborated theoretical background, the method requires few computational resources, and it is easy to implement. Mathematical developments, design hints, and an extensive batch of successful experimental tests are included in this paper.

Commissioning of Electromechanical Conversion Models for High Dynamic PMSM Drives

Several emerging applications require fast and precise torque control. Torque measurements are still expensive, bulky, and delicate. On the other hand, estimation techniques are all valid in principle, but their accuracy is largely affected by model identification and commissioning. This paper presents an accurate model for an effective torque estimation based on voltage and current measurements. The model includes all motor losses to get an enhanced overall accuracy, along with a fast response. The key feature is the commissioning procedure, based on a set of offline measurements. Procedure details and experimental results on a laboratory prototype are included.

Combined speed and current Model Predictive Control with inherent field-weakening features for PMSM Drives

The paper deals with the model predictive control (MPC) algorithm applied to control a permanent magnet synchronous motor, which is, at present, among the motors with the highest power efficiency and then very attractive for energy-saving applications. Absolute novelty of the proposed MPC is its feature of inherently managing the flux weakening control above base speed. Speed and current controller are combined together, including all the state variables of the system, instead of keeping the conventional cascade structure. In this way it is possible to enforce in the controller the current and voltage limits. Simulation and experimental results point out the validity of the design procedure and the powerful capabilities of the MPC in the electrical drives field.

The steering effect PM motor drives for automotive systems

The steer-by-wire (SBW) system requires the use of enhanced fuel economy, assist action given two motor drives, the first for the mechanical steering system and the second for the torque feedback to the steering wheel. An interior permanent magnet (IPM) synchronous motor is used for the steering actuator whereas a fractional-slot surface-mounted permanent magnet (SPM) synchronous motor is used for the torque feedback.

FPGA-based voltage measurements in AC drives

In the modern sensorless and self-commissioning drives scenario, the availability of precise phase voltage measurement represents an undoubted advantage. But the task is not trivial, and few viable solutions are available. The present paper proposes an up-to-date digital method for the measurement of the instantaneous phase voltages of a three-phase PWM inverter. The phase-to-phase PWM inverter voltages are oversampled with respect to the switching period by fast A/D converters, which feed the FPGA-based digital integrator. The digital output is ready for further uses in any advanced control and estimation algorithm. Measurement repeatability, reduced size, tuning-free circuit are among the inherent side-advantages of the FPGA-based solution with respect to the existing analog ones. The paper includes design hints and a full batch of experimental tests and validations.