The position control of designed 3 PRR flexure based mechanism is examined in this paper. The aims of the work are to eliminate the parasitic motions of the stage, misalignments of the actuators, errors of manufacturing and hysteresis of the system by having a redundant mechanism with the implementation of a sliding mode control and a disturbance observe. x-y motion of the end-effector is measured by using a laser position sensor and the necessary references for the piezoelectric actuators are calculated using the pseudo inverse of the transformation matrix coming from the experimentally determined kinematics of the mechanism. The effect of the observer and closed loop control is presented by comparing the results with open loop control. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control for active 2 piezoelectric actuators experiments then for active 3 piezoelectric actuators experiments are presented. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger.

ed/Indexed in Science Citation Index Expanded, SCOPUS, EBSCO and INSPEC (Institution of Electrical Engineers)

ed/Indexed in Science Citation Index Expanded, SCOPUS, EBSCO and INSPEC (Institution of Electrical Engineers)

ed/Indexed in Science Citation Index Expanded, SCOPUS, EBSCO and INSPEC (Institution of Electrical Engineers)

ed/Indexed in Science Citation Index Expanded, SCOPUS, EBSCO and INSPEC (Institution of Electrical Engineers)

AMC 2012 The 12 International Workshop on Advanced Motion Control Bristol Hotel, Sarajevo, Bosnia and Herzegovina 25-27 March 2012

Bilateral teleoperation systems are an active area of research with possible applications in healthcare, remote surveillance and military, space and underwater operations, allowing human operators to manipulate remote systems and feel environment forces to achieve telepresence. The physical distance between the local and remote systems introduces delay to the exchanged signals between the two and cause instability in the bilateral teleoperation. With the advent of the internet, possible applications of bilateral teleoperation systems have proliferated, growing the interest and amount of research in the field. The delay compensation method for stable and force reflecting teleoperation proposed in this thesis is based on utilization of three different types of observers: A novel predictor observer that estimates the undelayed states of the remote system based on a nominal model, disturbance observers that eliminate internal and external disturbances and linearize the nonlinear dynamics of the two systems, and reaction torque observers that estimate the net external forces on the two systems. The controller for the remote system is placed at the local site, along with the predictor observer and the control input is sent to the remote system through the communication channel. Force reflection is achieved using a modified version of the 4-channel architecture where control input and position of the remote system and the environment force estimations are exchanged between the two systems. Performance of the proposed method is tested with Matlab/Simulink simulations and compared to two other methods in the literature. Real-time experiments under variable communication delay are also performed where the delay is both artificially created using Matlab/Simulink blocks and obtained via the internet by bouncing signals off a remote computer outside the Sabanci University campus. Both the simulations and experiments are executed on a pair of 1-DOF robot arms and a pair of 2-DOF pantograph robots. The results show that stable and force reflecting teleoperation is achieved with successful tracking performances of the remote system.

Motion control systems represent a main subsystem for majority of processing systems that can be found in the industrial sector. These systems are concerned with the actuation of all devices in the manufacturing process such as machines, robots, conveyor systems and pick and place mechanisms such that they satisfy certain motion requirements, e.g., the pre specified reference trajectories are followed along with delivering the proper force or torque to the point of interest at which the process occurs. In general, the aim of force/torque control is to impose the desired force on the environment even if the environment has dynamical motion.

In this paper, microassembly system design issues are discussed with requirements, constraints and necessities for the development of an assembly platform, and these issues are shown over a versatile and reconfigurable microassembly workstation which is designed and realized as a research tool for investigation of the problems in microassembly and micromanipulation tasks. First prototype of a workstation and the development of a second prototype with enhancements on mechanical and control structure of the system are presented with details on the configuration of the systems. In addition, several experiments using a workstation are presented both on the first and the second prototypes in different modes of operation such as tele-operated, semi-automated and fully automated by means of visual feedback.

As fossil energy resources deplete, wind energy gains ever more importance. Recently, piezoelectric energy harvesting methods are emerging with the advancements in piezoelectric materials and its storage elements. Piezoelectric materials can be utilized to convert kinetic energy to electrical energy. Utilization of piezoelectric wind harvesting is a rather new means to convert renewable wind energy to electricity. Piezoelectric generators are typically low cost and easy to maintain. This work illustrates an overview of piezoelectric wind harvesting technology. In wind harvesting, piezoelectric material choice is of the first order of importance. Due to their strain rate, robustness is a concern. For optimum energy harvesting efficiency resonant frequency of the selected materials and overall system configuration plays important role. In this work, existing piezoelectric wind generators are grouped and presented in following categories: leaf type, rotary type, rotary to linear type and beam type wind generators.

This paper presents a state observer based on the action reaction law of dynamics. The proposed observer allows estimating states of single input flexible dynamical systems with unknown or inaccessible outputs where the instantaneous system reaction is utilized as a feedback like force/torque and used in the design of a state observer. Necessary and sufficient conditions for observability of this class of dynamical systems are investigated. Robustness of the proposed state observer to parameter uncertainties is further studied. The proposed observer makes it possible to keep a class of single input flexible dynamical systems free from any attached sensors while estimating their states. Validity of the proposed action reaction based state observer is evaluated experimentally.

This paper proposes a new algorithm based on model following control to recover the uncompensated slave disturbance on time delayed motion control systems having contact with environment. In the previous works, a modified Communication Disturbance Observer (CDOB) was shown to be successful in ensuring position tracking in free motion under varying time delay [11], [12]. However, experiments show that due to the imperfections in slave plant Disturbance Observer (DOB) when there is rapid change of external force on the slave side, as in the case of environment contact, position tracking is degraded. This paper first analyzes the effect of environment contact for motion control systems with disturbance observers. Following this analysis, a model following controller scheme is proposed to restore the ideal motion on the slave system. A virtual plant is introduced which accepts the current from the master side and determines what the position output would be if there was no environment. Based on the error bet ween actual system and model system, a discrete time sliding mode controller is designed which enforces the real slave system to track the virtual slave output. In other words, convergence of slave position to the master position is achieved even though there is contact with environment. Experimental verification of the proposed control scheme also shows the improvement in slave position tracking under contact forces.

This paper presents the analytical in-plane compliance calculation methods for single axis circular flexure hinges and compares the methods with Finite Element Analysis (FEA). These comparisons are also made for varying geometric parameters not only for “b” (the width of the flexure) but also “t” (the shortest distance of the flexure) parameter. The analyses give us the selectable calculation methods for certain “b” and “t” parameters besides they show which geometric parameter (b or t) have more influence on in which direction of compliances. Thus, while designing a flexure based mechanism this work gives us the advantage of selecting right in-plane compliance calculation methods which are less time consuming and easier than FEA and it also helps us to choose the right geometric parameters by showing the effects of them on the compliances.

This work attempts to achieve precise motion control using parallel robots with manufacturing tolerances and inaccuracies by migrating the measurements from their joint space to task space in order to decrease control system's sensitivity to any kinematical uncertainty rather than calibrating the parallel plant. The problem of dynamical model uncertainties and its effect on the derivation of the control law is also addressed in this work through disturbance estimation and compensation. Eventually, both task space measurement and disturbance estimation are combined to formulate a control framework that is unsensitive to either kinematical and dynamical system uncertainties.