Motion control technology is making its way into the unstructured world inhabited by humans. It allows development of applications beyond the structured environment of an industrial plant. Such applications of motion control technology require shifting focus to the models, control strategies and algorithms needed for systems to work, interact, and cooperate with humans or other artifacts in an unstructured environment. Real-world haptic interactions are becoming an important technology with potential application in many different fields like surgery, teleoperation, cooperative work, microsystems, and education. These developments are leading to numerous challenges that need to be solved in order to develop practical and competent systems that support the human operator, and are fault tolerant, safe, easy to use, and capable of adapting to long-term changes in the environment. This paper discusses a number of the emerging issues within motion control technology, including but not limited to new algorithms that allow concurrent force/position control, human-in-the loop control, control in functionally related systems and haptics over internet.

In this paper, design of a robust cascade controller for a Cuk converter is investigated. The controller contains two loop cascaded structure. The external voltage loop, which is the slow loop, contains the continuous proportionalintegral( PI) voltage controller whereas the internal current loop, which is the fast loop, contains the continuous sliding mode controller(CSMC). The controller effectiveness is validated by simulating the Cuk converter in SimPowerSystems ® toolbox of MATLAB/Simulink ®. The simulation is done for six different cases including ideal case, sudden variation of input supply voltage, load resistance, reference voltage, for noise disturbance and parametric variation. It is shown that the performance of the proposed controller is satisfactory and the ultimate goal of tracking the reference by the converter output voltage and the inductor current is achieved with little or no sensitivity to the uncertainties simulated.

This paper is concerned with the force control of a walking piezoelectric motor, a commercially available Piezo LEGS motor. The motor is capable of providing high precision positioning control on nanometer scale, but also relatively high forces up to 6 N. The proposed force control algorithm is very simple, but effective, and it is based on a recently presented coordinate transformation. The transformation allows definition of the driving waveforms for the motor according to a desired motion of the motor legs in the plane of motion. Such a possibility opens a path for creating the y-direction interaction force between the motor legs and the rod which is enough to ensure no relative motion between the legs and the rod. Once that is achieved, one can control the x-direction force imposed by the motor rod on its environment. The presented force control scheme has been successfully validated through a series of experiments.

Compliant mechanisms have great advantages to be used as micropositioning stages for high-precision applications but they are very sensitive to manufacturing tolerances and assembling errors. In this work, a novel compliant stage having 3-PRR kinematic structure and actuated by piezoelectric actuators is introduced. A kinematic modeling based on compliance of the flexible elements and finite element analysis based model have been extracted. It is found out that the experimental results are not compatible with the theoretical results due to the manufacturing, actuator assembly errors. The position control of the mechanism has been achieved using sliding mode control which is a great method for unpredictable varying parameters in the system. Sliding mode observer has also been used for the hysteresis and nonlinearities of the piezoelectric actuators. Experimental models for each actuation axis have been used as the nominal models for the sliding mode observer. In order to see the advantage of the control method simple PID control has also been implemented. It is seen that sliding mode control with sliding mode observer using experimental models reduces the position tracking errors to the range of the accuracy of our available measurement. Graphical Abstract

In this study, a novel compression and decompression algorithm, namely the selected discrete cosine transform (DCT), is presented for implementation in networked motion control systems. The proposed method relies on the utilization of a selection algorithm based on bubble sorting to choose the highest power coefficients of the signal obtained by using DCT. In order to better illustrate the effectiveness of the proposed method, comparisons are made with the methods existing in the literature. To this aim, the basics of the compression schemes used in the comparison, namely, the DCT, discrete Fourier transform, and wavelet packet transform, are also briefly discussed followed by the derivation of the proposed method. The algorithmic bases of all four schemes are given to provide further reference for practical applications. The proposed method is tested on an experimental platform consisting of a single-single-degree-of-freedom master and slave systems, and the results are comparatively analyzed based on relevant performance evaluation metrics. The obtained results demonstrate the improvement achieved by the proposed compression scheme over the existing compression methods used in network-based motion control applications, hence proving the feasibility of the approach in teleoperation systems.

The popularity of renewable energy conversion systems, and especially of wind energy, has been growing in recent years. Doubly fed induction generator (DFIG)-based wind energy systems are extensively used due to their wide range of active and reactive power controllability. Conventional DFIG control structures consist of decoupled PI rotor current controllers with stator flux orientation and machine parameter-dependent compensating terms. The accuracy of stator flux calculations is dependent on how accurately the stator resistance is known. Integration problems also exist and additional low-pass filters are implemented to accurately calculate the stator flux. In the current study, machine-dependent compensating terms are estimated with a rst-order low-pass filter disturbance observer. Therefore, a single proportional (P) controller is sufficient to control decoupled rotor currents. The proposed controller structure is implemented on a MATLAB/Simulink platform with the parameters of 500 kW DFIG used in the M_ILRES (Turkish National Wind Energy) project. The proposed controller is also experimentally validated in an experimental setup.

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.

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.

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.

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.

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.