Showing papers by "Asif Sabanovic published in 2015"

Piezo LEGS Driving Principle Based on Coordinate Transformation

Abstract: This paper offers a new approach for specifying the waveforms of driving voltages for a Piezo LEGS motor. A novel idea of coordinate transformation to define the waveforms of driving voltages, based on the motor static model, is presented. This transformation defines driving voltages according to the desired motion of the motor legs in the x - and y -directions. The approach allows a user to first define force acting on the motor rod in the y -direction and define the rod's x -direction trajectory profile. Waveforms of the driving voltages are subsequently defined to meet these requirements. The proposed approach also enables the possibility of defining the desired step shape for the motor and, according to that definition, producing driving voltages. Based on the given coordinate transformation, a simple method for Piezo LEGS motor control, identified as virtual time control, is presented. This method results in overshoot-free high precision positioning.

Practical PID controller tuning for motion control

Abstract: The most popular control method in the industry is PID control due to its simple structure and effective performance. Although huge numbers of PID controller tuning methods have been proposed so far, existing ones still do not have the desired performances and the simplicity. Complex system dynamics make it challenging for engineers and students to apply these methods on their applications especially in the motion control and robotics areas. Such systems generally include nonlinearity, friction, varying inertia and unknown disturbances which make the conventional tuning methods ineffective and too complex to be used. There is need for simple and effective PID tuning methods in these areas. In order to solve this problem, this paper proposes two novel practical PID tuning methods for motion control systems. These methods bring the superiority of the 2 degree of freedom control approach to simple PID controller structures analytically. They are very effective in motion control and robust both to parameter uncertainty and unknown disturbances, yet very simple. They can be easily used by the engineers in the industry and the students with very basic control knowledge, so little effort and time. The tuning methods of robust PID and PI controllers with velocity feedbacks are proposed, for position and force control problems of servo systems, respectively. The validities of the proposals are verified by the experimental results.

A novel current controller scheme for doubly fed induction generators

Abstract: This paper presents a novel current control methodology for grid connected doubly-fed induction generator (DFIG) based wind energy conversion systems. Controller is based on a proportional controller with additional first order low pass filter disturbance observer which estimates the parameter dependent nonlinear feed-forward terms. The results in simulations and experimental test bed obviously demonstrate that decoupled control of active and reactive power is achieved without the necessity of additional machine parameter.

Wavelet packet transform-based compression for teleoperation

Abstract: This paper introduces a codec scheme for compressing the control and feedback signals in networked control and teleoperation systems. The method makes use of Wavelet Packet Transform (WPT) and Inverse Wavelet Packet Transform (IWPT) for coding and decoding operations, respectively. Data compression is carried out in low-pass filter output by reducing the sampling rate, and in high-pass filter output by truncating the wavelet coefficients. The proposed codec works on both directions of signal transmission between a master robot and a slave robot over a networked motion control architecture. Following the formulation of the compression/decompression methodology, experimental validation is conducted on a single-degree-of-freedom motion control system. In the experiments, responses from different Wavelet structures are analyzed and a comparative study is carried out considering the factors of compression rate, reconstruction power error and real-time computational complexity. It is confirmed that the controller using the proposed compression algorithm performs very close to the uncompressed one while enabling transmission of much less data over the network.

Internet of things inspired photovoltaic emulator design for smart grid applications

Abstract: The future smart grid is considered to be solution for common problems associated with current electricity grid. Smart grid will incorporate renewable energy sources, intelligent sensors and controls, automated switches, robust communication technology, etc. Implementation of such smart grid requires the collective efforts from researchers from many fields of engineering and creation of reliable test platforms. This paper presents the PV emulator as a test platform for research of problems associated with the design of controller for PV sources, the design of energy management system, generation capacity prediction, wireless network integration and protocol issues, security and cloud based data management and analysis for smart grid applications.

Formation control of differential-drive mobile robots in the framework of functionally related systems

Abstract: A novel approach for formation control of differential-drive mobile robots is presented in this paper. The control design is done in the framework of functionally related systems. Functionally related systems are the systems that are ‘virtually’ interconnected. The term ‘virtually’ denotes the situation in which the states or outputs of otherwise separated systems are functionally related to each other. If a formation of mobile robots is analyzed, it can be considered as a group of functionally related systems. Therefore, formation control of the robots can be synthesized in the mentioned framework.

Control system for high precision positioning applications based on Piezo motors

Abstract: In this paper implementation of a control system for high precision applications is presented. The control system is developed for a Piezo LEGS motor, which is a walking piezo motor that can be employed in nanometric precision applications. In the control system structure, two main components are digital signal controller which executes control algorithm and power driver that is generating driving voltages for the motor. The waveforms of the driving voltages are designed using a recently presented coordinate transformation. This transformation enables synthesis of driving waveforms according to design requirements regarding force imposed to the motor's rod and rod's x-direction trajectory profile. In this work, the waveforms are selected to ensure no relative motion between the motor's legs and rod, and constant velocity of the rod within one step. Control algorithm is named as virtual time control. Despite its simplicity, the algorithm allows high precision positioning which is very close to theoretically achievable one.

DSC-based implementation for power control of DFIG in microgrid applications

Abstract: This paper presents a compact and low cost digital signal controller (DSC) based implementation for power control of a doubly fed induction generator (DFIG) based wind energy setup for micro-grid applications. The experimental setup consists of a back to back converter, a 1.1 kW DFIG and two low cost, industry standard DSCs. Stator active power and reactive power are controlled by means of the rotor currents. Decoupled components of the rotor current in a rotating frame are controlled by a robust, disturbance observer based control structure. The proposed controller was validated through experiments.