Ahmet Ozcan Nergiz

Scaled Bilateral Teleoperation Using Discrete-Time Sliding-Mode Controller

In this paper, the design of a discrete-time sliding-mode controller based on Lyapunov theory is presented along with a robust disturbance observer and is applied to a piezostage for high-precision motion. A linear model of a piezostage was used with nominal parameters to compensate the disturbance acting on the system in order to achieve nanometer accuracy. The effectiveness of the controller and disturbance observer is validated in terms of closed-loop position performance for nanometer references. The control structure has been applied to a scaled bilateral structure for the custom-built telemicromanipulation setup. A piezoresistive atomic force microscope cantilever with a built-in Wheatstone bridge is utilized to achieve the nanonewton-level interaction forces between the piezoresistive probe tip and the environment. Experimental results are provided for the nanonewton-range force sensing, and good agreement between the experimental data and the theoretical estimates has been demonstrated. Force/position tracking and transparency between the master and the slave has been clearly demonstrated after necessary scaling.

Development of a micromanipulation mystem with force sensing

This article provides in-depth knowledge about our undergoing effort to develop an open architecture micromanipulation system with force sensing capabilities. The major requirement to perform any micromanipulation task effectively is to ensure the controlled motion of actuators within nanometer accuracy with low overshoot even under the influence of disturbances. Moreover, to achieve high dexterity in manipulation, control of the interaction forces is required. In micromanipulation, control of interaction forces necessitates force sensing in milli-Newton range with nano-Newton resolution . In this paper, we present a position controller based on a discrete time sliding mode control architecture along with a disturbance observer. Experimental verifications for this controller are demonstrated for 100, 50 and 10 nanometer step inputs applied to PZT stages. Our results indicate that position tracking accuracies up to 10 nanometers, without any overshoot and low steady state error are achievable. Furthermore, the paper includes experimental verification of force sensing within nano-Newton resolution using a piezoresistive cantilever end- effector. Experimental results are compared to the theoretical estimates of the change in attractive forces as a function of decreasing distance and of the pull off force between a silicon tip and a glass surface, respectively. Good agreement among the experimental data and the theoretical estimates has been demonstrated.

Model following control with discrete time SMC for time-delayed bilateral control systems

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.

Function based control for bilateral systems in tele-micromanipulation

Design of a motion control system should take into account (a) unconstrained motion performed without interaction with environment or any other system, and (b) constrained motion with system in contact with environment or other systems. Control in both cases can be formulated in terms of maintaining desired system configuration what makes essentially the same structure for common tasks: trajectory tracking, interaction force control, compliance control etc. The same design approach can be used to formulate control in bilateral systems aimed to maintain desired functional relations between human and environment through master and slave motion systems. Implementation of the methodology is currently being pursued with a custom built tele-micromanipulation setup and preliminary results concerning force/position tracking and transparency between master and slave are clearly demonstrated.

A Hybrid Force-Position Controller based Man-Machine Interface for Manipulation of Micro Objects

A hybrid force-position controller based man-machine interface for manipulation of micro objects through pushing with a micro cantilever is presented. Visual feedback is employed to detect position and orientation of a micro particle and a piezoresistive AFM cantilever is automatically positioned to align the line of action of interaction forces in a way that will ensure the particle to track a desired trajectory. Control of the interaction force is delegated to a human operator through scaled bilateral teleoperation. A custom tele-micromanipulation setup is built for testing and preliminary experiments of controlled pushing to achieve pure translational motion of rectangular micro objects are implemented.

Design and control of laser micromachining workstation

The production process of miniature devices and microsystems requires the utilization of non-conventional micromachining techniques. In the past few decades laser micromachining has became micro-manufacturing technique of choice for many industrial and research applications. This paper discusses the design of motion control system for a laser micromachining workstation with particulars about automatic focusing and control of work platform used in the workstation. The automatic focusing is solved in a sliding mode optimization framework and preview controller is used to control the motion platform. Experimental results of both motion control and actual laser micromachining are presented.

An efficient and scalable meeting minutes generation and presentation technique

Meetings are essential for a group of individuals to work together. An important output of meetings is minutes. Taking and distributing minutes is a time consuming task. Also, any new member of a meeting series will not be able to easily refer to old minutes if they are in written or e-mail format. Our contribution to this problem is to propose a new approach for taking meeting minutes that will allow dynamic and cooperative note taking. In addition, resulting minutes will allow any new participant to spend a smaller integration time.

Desktop microfactory for high precision assembly and machining

This work presents a modular and reconfigurable desktop microfactory for high precision machining and assembly of micro mechanical parts. Miniature factory is inspired by the downsizing trend of the production tools. The system is constructed based on primary functional and performance requirements such as miniature size, operation with sub-millimeter precision, modular and reconfigurable structure, parallel processing capability, ease of transportation and integration. Proposed miniature factory consists of several functional modules such as two parallel kinematic robots for manipulation and assembly, galvanometric laser beam scanning system for micromachining, camera system for inspection, and a rotational conveyor system for sample part delivery. The overall mechanical structure of the proposed microfactory facilitates modularity and reconfigurability, parallel processing, flexible rearrangement of the layout, and ease of assembly and disassembly of the whole structure. Experiments involve various tasks within a single process such as pick-place of the 3 mm diameter metallic ball, marking a 2D sub-millimeter image on the ball surface with high power laser, and inspection along with verification of the image by means of microscopic camera. Results have shown the possibility of implementation of the desktop microfactory concept for machining and assembly of tiny mechanical parts with microprecision.

A novel state observer for dynamical systems with inaccessible outputs

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.

Implementation of a novel complex mechatronics software framework on laser micromachining workstation

As technology brings more complex and sophisticated systems, the importance of the problem of designing and developing a mechatronic system increases as well and it becomes more complicated to obtain a reliable, accurate and sustainable system. Since complex systems are generally composed of many different types of sub-systems, a necessity for a systematic approach towards the development arises. In this paper, the problem of software development for complex mechatronic systems is addressed and a novel software framework is proposed in order to provide common design and development criteria and related software structures. As an implementation of the framework and to present a proof of concept, software for a laser micromachining workstation is developed from scratch using this framework. Experiments are conducted using the workstation and results are provided.