Ahmad Ghaderi

Wide-Speed-Range Sensorless Vector Control of Synchronous Reluctance Motors Based on Extended Programmable Cascaded Low-Pass Filters

This paper proposes a new sensorless vector control of a synchronous reluctance motor for a wide range of speeds. The estimation of speed and rotor angle is based on extended programmable cascaded low-pass filters (LPFs), which effectively reduce the effects of direct-current (dc) offsets at low speeds. The effect of the number of LPF stages on output dc offset, estimation accuracy, and dynamic performance are determined, and their equations are developed. The determination of the number of LPF stages is based on these developed equations. Because the estimate of the rotor angle near-zero speed is possible, the motor start-up procedure can be done without complexity. The experimental results show that the estimated and the actual rotor angles are in agreement at very low and high speeds. Thus, sensorless vector control can be achieved over a wide range of speeds. In addition, motor start-up in a standstill condition is possible, and the transient response at low and high speeds is acceptable.

A Novel Seamless Direct Torque Control for Electric Drive Vehicles

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

A new direct torque control for AC motors with over modulation ability

Comparison of various motor drives has revealed that direct torque control (DTC) drive has several advantages and a much faster torque response compared to other AC or DC drives. However, the conventional DTC cannot operate in the six-step mode, which is required in high-speed applications. Therefore, an accurate method is essential in order to achieve a seamless transformation between conventional DTC and six-step operation. In the present paper, a single-mode seamless control of AC motors is achieved by proposing a new direct torque control. Since seamless control is not possible using the conventional DTC, we develop a new DTC in which the flux trajectory is modified. In the proposed method, the motor flux trajectory changes continuously between a circular shape and a hexagonal shape, and thus the inverter voltage changes from high-frequency switching to a six-step square wave with only one control mode. Therefore, in the proposed method, which uses only one mode, torque discontinuity does not occur because this discontinuity usually occurs during switching between modes. In addition, since the proposed method is a single-mode control, this method is much simpler than existing technologies, which are based on multi-mode controllers.

Sensorless speed control of synchronous reluctance motor using a novel flux estimator based on Recursive Fourier Transformation

This paper proposes a sensorless control of SynRM (synchronous reluctance motor). It can calculate the motor flux from an armature voltage and a current directly. The proposed estimator is able to eliminate both the dc offset and harmonic component of the armature current which cause the estimation error. State observer based Fourier Transformation called RFT (Recursive Fourier Transformation) is effective to estimate the fundamental component of the flux. Also a block pulse approximation is used to convert a continuous time state equation to a difference equation to reduce the calculation time. The validity of the proposed method is shown in the experimental results.

Power and propulsion systems design for an autonomous omni-directional mobile robot

In this paper power and propulsion systems design for an autonomous omni-directional mobile robot which is developed for RoboCup compaction, is presented. For robot energy storage unit, lithium ion polymer battery is chosen because of its high power and energy densities, and a protection circuit against deep battery discharge was designed for it. Because the power flow between energy storage units and motors and also speeds of motors have to be controlled at the same time, we proposed a two cascaded cell modules consisting motor speed control and power flow control modules. The other parts of our robot power system are dc-dc converters and kicker circuit. The simulation and experimental results show proposed scheme is valid and energy management and speed control can be achieved properly using this method. The filed experiments show robot mobility functions to perform the requested motion is enough and it has a high maneuverability in the field.

An Altered PWM Scheme for Single-Mode Seamless Control of AC Traction Motors for Electric Drive Vehicles

In an electric drive vehicle (EDV), the available voltage on a dc-link is limited, and so the inverter output voltage and, consequently, the line motor maximum speed are limited. The fundamental voltage of the inverter output is increased approximately 27% using a square wave (SW) switching pattern instead of a sine wave switching pattern. However, this pattern can only be used at high speeds, and at lower speeds a pulsewidth modulation (PWM) pattern should be used. In order to achieve proper control, the switching pattern should be changed seamlessly. In the present paper, a new PWM scheme for single-mode seamless control of Vernier motors is proposed. In the proposed scheme, the reference voltage is modified to change the switching pattern continuously so that the voltage changes smoothly from a high-frequency pattern to an SW and voltage discontinuity does not occur. Experimental results reveal that the inverter-switching pattern changes smoothly from a sinusoidal PWM pattern to an SW pattern, and so seamless control from the constant-torque region to the constant-power region, and vice versa, is achieved. Since the proposed scheme is a single-mode control, it is much simpler than current technologies, which are based on multimode controllers. Also the proposed method has a lower total harmonic disturbance (THD) as well as a lower harmonic distortion factor (HDF) compared to some existing methods.

RTLinux Based Online Real Time Simulator of SPMSM Using the Block Pulse Approximation

RTLinux based online real time simulator for speed control system of SPMSM (Surface Permanent Magnet Synchronous Motors) is proposed. For realization of the online real time simulator, a motor mathematical model based on the three phase stationary coordinate is solved using a Single Term Block Pulse Function (STBPF) and system analysis in real time. The STBPF analysis is one of the linearized model approximation so that it is more simple and it saves more calculation time compared with the other numerical analysis method, such as a Runge-Kutta algorithm. In addition, the proposed method can simulate the system more precisely by a variable width of the orthogonal input state, so it is suitable to solve an inverter model which generates the PWM pulse and the dead time effect, so on. The experimental system is based on the RTLinux and this accomplishes both the motor control and the real time simulation at the same time in 200 μs control period. Experimental results show that the online simulation results show considerable coincidence with the experimental results.

A Novel Embedded Computer Based Autonomous Robot for Sewer Pipe Inspection

In this paper, in order to realize an effective inspection system, an embedded computer based autonomous pipe inspection robot is presented. This robot is designed as a fully autonomous, un-tethered robot, which fits to the pipes within a diameter range of 200- 300 millimeters. The practical field tests show that the robot performs well and can do pipe inspection properly and the robot moves gracefully not only at straight paths but also at junctions and curves.

Concept of mechatronics safety and modularity design for an autonomous mobile soccer robot

In this paper, we describe the concept, design and implementation of a series of autonomous mobile soccer robots, named ldquoMusashirdquo robot, which have safety design which is based on ISO and a mechatronics modular architecture, to participate in the RoboCup middle-size league. In modularity design methodology, we show that the selection of a proper moving mechanism, a suitable vision system and a mechatronics modular architecture design can lead to realize a reliable, simple, and low cost robot comparing with most of car-like robots including many kinds of sensors and a complex design structure.