In this paper, control of piezostage using sliding-mode control (SMC) method is presented. Due to the fast dynamics of the piezostage and since high accuracy is required the special attention is paid to avoid chattering. The presence of hysteresis characteristics represents main nonlinearity in the system. Structure of proposed SMC controller is proven to offer chattering-free motion and rejection of the disturbances represented by hysteresis and the time variation of the piezostack parameters. In order to enhance the accuracy of the closed loop system, a combination of disturbance rejection method and the SMC controller is explored and its effectiveness is experimentally demonstrated. The disturbance observer is constructed using a second-order lumped parameter model of the piezostage and is based on SMC framework. Closed-loop experiments are presented using a proportional-integral-derivative controller and sliding-mode controller with disturbance compensation for the purpose of comparison

This work aims the precise control of the piezoelectric actuators that can theoretically provide unlimited motion resolution. For this purpose Sliding Mode Controller (SMC) is used. The proposed algorithm is known to have order of sampling time square and therefore faster application than DSP was required. The application of the algorithm via analog electronics is suggested. Preliminary work, simulation and experimental results are presented.

In this paper discrete sliding mode control (SMC) of Piezo actuator is demonstrated in order to achieve a very high accuracy in Nano-scale with the desired dynamics. In spite of the fast dynamics of the Piezo actuator the problem of chattering is eliminated with the SMC control structure. The Piezo actuator suffers from hysteresis loop which is the inherent property and it gives rise to the dominant non-linearity in the system. The proposed SMC control structure has been proved to deliver chattering free motion along with the compensation of the non linearity present due to hysteresis in the system. To further enhance the accuracy of the closed loop system and to be invariant to changes in the plant parameters a robust disturbance observer is designed on SMC framework by taking into consideration the lumped nominal plant parameters. Experimental results for closed loop position and micromanipulation applications are presented in order to verify the Nano-scale accuracy.

In this paper a discrete-time sliding-mode based controller design for high accuracy motion control systems is presented. The controller is designed for a general SISO system with nonlinearity and external disturbance. Closed-loop behavior of the general system with the proposed control and Lyapunov stability is shown and the error of the closed loop system is proven to be within an o(T2). The proposed controller is applied to a stage driven by a piezo drive that is known to suffer from hysteresis nonlinearity in the control gain. Proposed SMC controller is proven to offer chattering-free motion and rejection of the disturbances represented by hysteresis and the time variation of the piezo drive parameters. As a separate idea to enhance the accuracy of the closed loop system a combination of disturbance rejection method and the SMC controller is explored and its effectiveness is experimentally demonstrated. Closed-loop experiments are presented using PID controller with and without disturbance compensation and sliding-mode controller with and without disturbance compensation for the purpose of comparison

In this paper an estimate of the upper bound of control error for discrete-time implementation of a sliding mode control (DTSMC) combined with disturbance observer is investigated. Having in mind application to PZT high bandwidth actuators and since high accuracy is required the special attention is paid to avoid chattering. Selected structure of proposed SMC controller is proven to offer chattering-free motion. The proposed structure also avoids deadbeat poles that are the cause of large control action which is not desirable in practical applications. The proposed scheme is shown to allow a maximum error bound of O(T) for the system with disturbance. The main disturbances are represented by hysteresis and the time variation of the piezo stack parameters. The evaluation of the upper bound of error in such a system is shown and experimentally verified. Closed-loop experiments are presented using the proposed method to verify the theoretical results

The paper deals with high precision motion control of linear drive system. The accuracy and behavior of the linear drive system are highly affected by the non-linear frictional component compromising of stiction, viscous and Stribeck effect present in the system especially in the vicinity of zero velocity. In order to achieve the high accuracy and motion it is mandatory to drive our system with low velocity resulting in many nonlinear phenomena like tracking error, limit cycles and undesired stick-slip motion etc. This paper discuss the design and implementation of discrete time sliding mode control along with the implementation of dynamic frictional model in order to estimate and compensate the disturbance arising due to frictional component. Experimental results are presented to illustrate the effectiveness and achievable control performance of the proposed scheme

In this paper a discrete-time sliding-mode (SM) based controller for high accuracy position control is investigated. The controller is designed for a general SISO system with nonlinearity and external disturbance. It would be shown that application of the proposed controller forces the state trajectory to be within an O(Ts 2). The proposed controller is applied to a stage driven by a piezo drive that is known to suffer from nonlinearity. As a separate idea to enhance the accuracy of the closed loop system a combination of disturbance rejection method and the SMC controller is explored and its effectiveness is experimentally demonstrated. Closed-loop experiments are presented using PID controller with and without disturbance compensation and sliding-mode controller with and without disturbance compensation for the purpose of comparison

In this work, a sliding mode approach to model reference control of fully actuated electromechanical systems affine with control is presented. Instead of the traditional state error regulator between the desired model and the actual plant, the proposed approach utilizes the fact that on sliding mode, plant is enforced to remain on the sliding manifold. Performance of the controller is demonstrated on simulations and experiments on a piezoactuator. Results show that the approach is effective in dictating the nonlinear plant to behave as the desired linear model, so as to drive the piezoactuator for 1 nm step with only an open loop position controller in addition to the sliding mode model reference controller proposed

The problem of estimating motion from a sequence of images has been a major research theme in machine vision for many years and remains one of the most challenging ones. In this work, we use sliding mode observers to estimate the motion of a moving body with the aid of a CCD camera. We consider a variety of dynamical systems which arise in machine vision applications and develop a novel identification procedure for the estimation of both constant and time varying parameters. The basic procedure introduced for parameter estimation is to recast image feature dynamics linearly in terms of unknown parameters and construct a sliding mode observer to produce asymptotically correct estimates of the observed image features, and then use "equivalent control" to explicitly compute parameters. Much of our analysis has been substantiated by computer simulations and real experiments

Robots are expected to expand their range of activities to human environment. Robots in human environment need redundancy for environmental adaptation. Furthermore, they have to automatically modify their controllers in response to varying conditions of the environment. Therefore, the authors have proposed a method to design a hyper-degrees-of-freedom (DOF) control system efficiently. The method decouples a large control system into small independent components called ldquofunction.rdquo Motion of the entire control system is expressed as superposition of multiple functions. Combination of some functions realizes many patterns of motion. Hence, various motions are realized with much smaller efforts on controller design. Additionally, the controller design is explicit since a controller and a function correspond directly. This paper expands the method to multi-DOF robots in 3-D space, since the conventional method was limited to a multirobot system in 1-D space. A new problem of interference among function-based systems occurs along with the expansion. A disturbance observer is applied on each actuator to eliminate the interference. Procedures of controller design under varying conditions are also shown. The proposed method is applied to a grasping manipulator with 18 DOF. Its experimental results show the validity of the method.

Coordinated task manipulation by a group of autonomous mobile robots has received significant research effort in the last decade. Previous studies in the area revealed that one of the main problems in the area is to avoid the collisions of the robots with obstacles as well as with other members of the group. Another problem is to come up with a model for successful task manipulation. Significant research effort has accumulated on the definition of forces to generate reference trajectories for each autonomous mobile robots engaged in coordinated behavior. If the mobile robots are nonholonomic, this approach fails to guarantee successful manipulation of the task since the so-generated reference trajectories might not satisfy the nonholonomic constraint. In this work, we introduce a novel coordinated task manipulation model inclusive of an online collision avoidance algorithm. The reference trajectory for each autonomous nonholonomic mobile robot is generated online in terms of linear and angular velocity references for the robot; hence these references automatically satisfy the nonholonomic constraint. The generated reference velocities inevitably depend on the nature of the specified coordinated task. Several coordinated task examples, on the basis of a generic task, have been presented and the proposed model is verified through simulations

From the open-loop tele-operator systems of 1950’s to the modern kinesthetic training and surgery support setups, haptic systems took a long way of evolution. Application areas ranging from minimally invasive surgery to space training systems for astronauts, still there is a large room for improvements. The vast areas of emerging applications put a number of demands on haptic interfaces. Fidelity, large workspace and high force/torque capacity are among those demands. The thesis concentrates on the design of a haptic master arm. The mechanical system with an analysis of dynamics properties, electronic hardware, algorithms for forward and inverse kinematics and software for the integration of sensors and actuators are developed to create an infrastructure for haptic interaction. Though the major design criteria applied in this design are a large workspace and high force/torque capacity, dynamics compensation techniques are also discussed as part of the developed infrastructure. The main focus of the thesis is the design of this hardware and software base for haptic applications rather than the design of haptic control algorithms. A survey on haptic interfaces and master arm design criteria is presented firstly. A set of specifications for the master arm is determined for a general and multipurpose yet ergonomic use. Newton-Euler based simulation techniques are employed for the component selection. Sensors and controller hardware are selected according to the demands of the haptic control problem. Dynamics compensation techniques for the designed manipulator are considered and tested in simulation. Finally the designed master arm is assembled and electrically integrated.

In this paper a method for motion controller parameters adaptation in the framework of sliding mode control (SMC) system is presented. Design is based on minimization of a cost function selected to depend on the distance from sliding mode manifold thus providing that adaptive controller enforces sliding mode motion in a closed loop system. It has been proven that selected cost function guarantees that the global minima is reached and then the sliding mode conditions are satisfied, thus closed loop motion is robust against parameter changes and the disturbances. The design for both MIMO and SISO systems is discussed. For the controller design the system states and the nominal value of the control input matrix are used. The stability proofs are given and the controller performance is verified by experimental results. The proposed algorithm is applied to control of the PZT actuator having hysteresis nonlinearity. Experimental verification shows that very high accuracy is reached (sub-nanometer motion) while the complexity of the controller did not exceed the usual SMC control schemes

Accurate position-tracking control in a belt-driven servomechanism can experience vibrations and large tracking errors due to compliance and elasticity introduced by force transmission through the belt and nonlinear-friction phenomenon. In this paper, a new control algorithm which is based on a sliding-mode control that is able to deal with these problems is proposed. In order to further optimize position-tracking performance, the control scheme has been extended by an asymptotic disturbance observer. It has been proven that robust and vibration-free operation of a linear-belt-driven system can be achieved. The experiments presented in this paper show improved position-tracking error response while maintaining vibration suppression.