Roberto Petrella

Adaptive sliding mode observer for speed sensorless control of induction motors

This paper presents an adaptive sliding mode observer for speed sensorless field-oriented control of induction motors. The observer detects the rotor flux components in the two-phase stationary reference frame by the motor electrical equations. The motor speed is identified by an additional relation obtained by a Lyapunov function. The analytical development of the sliding observer and the speed identification algorithm is fully explained. Experimental results are presented, based on a TMS320F240 DSP controller implementation, showing the system performance with different observer gains and the influence of the motor parameters deviations.

Initial rotor position estimation method for PM motors

This paper presents a method to detect the rotor position of PM motors at standstill. It is suitable to avoid temporary reverse rotation or starting failure. The basic approach is the well-known method to estimate the rotor position by using the inductance variation as a function of the magnets position and the stator currents: a suitable sequence of voltage pulses is applied to the stator windings and the evaluation of the peak value of the current leads to the rotor position estimation. Actually, the current measurements show significant uncertainties which affect the rotor detection. In order to avoid these problems, the authors propose a novel procedure which combines an iterative sequence of voltage pulses with a fuzzy logic processing of the current responses and phase currents derivation based on the DC link current measurements. The proposed method has been implemented on a /spl mu/C DSP (TMS320F240). The obtained results confirm the effectiveness of the proposed solution. It is consistent with sensorless or nonabsolute position transducers drives, a wide range of motors and it does not require the knowledge of any of the motor parameters.

Sensorless speed control of a PM synchronous motor by sliding mode observer

This paper presents a sensorless speed control of a permanent magnet synchronous motor using a sliding mode observer. A vector control strategy is considered, for a motor with sinusoidal flux distribution. The sliding mode observer detects the voltages induced by the magnet flux on the stator windings. These signals are used to calculate the rotor position and speed needed for vector control. Due to the sliding mode operation, filters are used to smooth the estimated variables. A speed-dependent compensation is also proposed, in order to achieve an accurate estimation of the rotor position. As the observed variables are not available below a limit frequency, an open loop starting procedure is implemented. The resulting observer has been fully analyzed by simulations, in order to test the performance both in steady-state and transient operations. Experimental results based on a DSP TMS320C50 controller are presented, showing the performance of the sensorless drive over a wide range of operating conditions.

Sensorless speed control of a PM synchronous motor based on sliding mode observer and extended Kalman filter

In this paper a method for rotor speed and position detection in permanent magnet synchronous motors is presented, suitable for applications where low speed and standstill operations are not required. The approach is based on the estimation of the motor back-EMF through a sliding mode observer and a cascaded Kalman filtering. Due to its characteristics, the technique can be applied to motors having distorted and whatever shaped back-EMF waveform. The equation error for the rotor position estimation is derived and discussed. Test results are presented, which show the system performance including start-up capability, which is one of the most critical conditions in back-EMF based sensorless schemes.

Low cost phase current sensing in DSP based AC drives

This paper presents the implementation of two techniques for phase current sensing based on a low cost last generation /spl mu/C DSP (TMS320F24x). The first one is based on the measurement of the current flowing in a shunt resistor put in the DC bus of the inverter, the second one is based on the measurement of the current flowing in shunt resistors put in series to the emitter of the IGBT for each lower leg of the inverter. The information provided by these sensors, together with the pulse width modulation (PWM) information, is used to reconstruct the motor phase currents. After a description of the two methods and the limitations they present, an application in case of an induction motor drive is illustrated in which the adjacent vector-space vector pulse width modulation (AV-SVPWM) technique is used to drive the inverter. Some aspects involving the non ideal behaviour of different parts of the system (presence of dead time, power switches driver delay, rise and settling time of the current, A/D conversion module sampling time) are investigated in details and the specific hardware implementation is discussed. Experimental results and comparisons between the two methods are presented.

Speed and position estimation for PM synchronous motor with back-EMF observer

This paper presents a sensorless scheme for PM synchronous motors, based on back-EMF observer. It provides full analytical description of the back-EMF observer, and the calculation of the position estimation error, taking into account the variation of the electrical parameters of the motor, i.e. stator resistance and synchronous inductance, and the variation of the feeding voltage. The knowledge of such characteristics could be used to improve the performance and the robustness of the sensorless drive by a specific real-time compensation mechanism. Verifications and comparisons are carried out in three steps: a) a time-continuous simulation model (using Matlab-Simulink) is developed to confirm the analytical results; b) a real time simulator of the sensorless drive is used, to evaluate the influence of the time-discrete implementation; c) an experimental BSP based implementation is used to compare actual results.

Torque ripple compensation in permanent magnet synchronous motors based on Kalman filter

This paper presents a scheme for compensation of the electromagnetic torque ripple in field oriented control of nonsinusoidal permanent magnet synchronous motors. The stator flux linkage produced by the magnets is modelled as the sum of two terms, the first accounting for the 1/sup st/ spatial harmonic component and the second for the residual high order harmonics. The sources of torque ripple, due to the harmonics term, are identified by a Kalman filter and used to compensate the torque current reference generated by a speed controller. The reduction of the torque pulsation obtained by the method and the sensitivity with respect to the variation of the motor parameters are presented and discussed by means of realistic simulations.

Speed sensorless control of an interior PM synchronous motor

This paper presents an adaptive observer for speed sensorless field-oriented control of interior permanent magnet (IPM) synchronous motors. The observer detects the rotor magnet flux components in the two-phase stationary reference frame using the motor electrical equations. The motor speed is identified by a model reference adaptive scheme using an additional equation obtained by a Lyapunov function. The analytical development of the observer is fully explained. The convergence of the estimates at low speeds and standstill is achieved through the assistance of a high frequency signal injection technique. Realistic simulations accounting for the inaccuracy of an actual digital signal processor (DSP) implementation are presented and discussed.

Speed and Position Estimation for PM Synchronous Motor using self-compensated Back-EMF Observers

The paper deals with the self-compensation of the intrinsic estimation error in back-EMF based rotor position observers for PM synchronous motors. The self-compensation is based on the analytical calculation of the rotor position estimation error for two types of popular back-EMF observers, such as the standard-linear Luenberger observer and the nonlinear sliding mode observer. Once the compensation characteristics are derived, they are included in the observer itself by a proper mechanism in order to cancel the position error affecting the estimation, thus providing the real-time self-compensation scheme. As a consequence, the performance and the robustness of the transducer-less drive can be improved, both at steady state and transient operations. Test results are presented to verify the effectiveness of the method in several operating conditions: both simulation results using a time-continuous Matlab/ Simulink model, and experimental results using a DSP based transducer-less drive

DSP based AC drive controller with real-time complex path generation for intelligent motion applications

The paper presents a single axis intelligent position controller for high performance multiple axes motion control systems where complex paths must be employed for each axis to obtain smooth acceleration, speed and position shapes. The task of complex path generation is performed by the same electrical drive controller in real-time, based on a simple set of movement characteristics. The proposed solution permits employment of a low-cost general purpose /spl mu/C as master controller while the overall system communication requirements are reduced and fast and accurate motion control is achieved. A vector controlled permanent magnet synchronous motor (PMSM) drive is considered as an actuator, based on a last generation /spl mu/C DSP (TMS320F24x). Experimental results showing the system performance for different movement characteristics are presented.