Erkan Zergeroglu

Nonlinear coupling control laws for an underactuated overhead crane system

In this paper, we consider the regulation control problem for an underactuated overhead crane system. Motivated by recent passivity-based controllers for underactuated systems, we design several controllers that asymptotically regulate the planar gantry position and the payload angle. Specifically, utilizing LaSalles invariant set theorem, we first illustrate how a simple proportional-derivative (PD) controller can be utilized to asymptotically regulate the overhead crane system. Motivated by the desire to achieve improved transient performance, we then present two nonlinear controllers that increase the coupling between the planar gantry position and the payload angle. Experimental results are provided to illustrate the improved performance of the nonlinear controllers over the simple PD controller.

Robust tracking and regulation control for mobile robots

This paper presents the design of a new, differentiable kinematic control law that utilizes a damped dynamic oscillator with a tunable frequency of oscillation to achieve global uniformly ultimately bounded tracking (i.e., the position/orientation tracking errors globally exponentially converge to a neighbourhood about zero that can be made arbitrarily small). In contrast to many of the previously developed kinematic tracking controllers, the proposed controller can be used for the regulation problem as well; hence, a unified framework is provided for both the tracking and the regulation problem. To compensate for uncertainty in the dynamic model, we illustrate how the kinematic controller can be used to design a robust nonlinear controller. Experimental results are presented to demonstrate the performance of the proposed controller. Copyright

Nonlinear coupling control laws for an overhead crane system

We consider the regulation control problem for a two-degree-of-freedom (2-DOF), underactuated overhead crane system. Inspired by recently designed passivity-based controllers for underactuated systems, we design several controllers that asymptotically regulate the gantry position and payload position. Specifically, utilizing LaSalles invariance set theorem, we first illustrate how a simple proportional-derivative (PD) controller can be utilized to asymptotically regulate the overhead crane system. Motivated by the desire to achieve improved transient performance, we then design a two nonlinear controllers that increase the coupling between the gantry position and payload position.

Global exponential tracking control of a mobile robot system via a PE condition

This paper presents the design of a differentiable, kinematic control law that achieves global asymptotic tracking. In addition, we also illustrate how the proposed kinematic controller provides global exponential tracking provided the reference trajectory satisfies a mild persistency of excitation (PE) condition. We also illustrate how the proposed kinematic controller can be slightly modified to provide for global asymptotic regulation of both the position and orientation of the mobile robot. Finally, we embed the differentiable kinematic controller inside of an adaptive controller that fosters global asymptotic tracking despite parametric uncertainty associated with the dynamic model. Experimental results are also provided to illustrate the performance of the proposed adaptive tracking controller.

Robust Visual-Servo Control of Robot Manipulators in the Presence of Uncertainty

This paper considers the problem of position control of planar robot manipulators via visual servoing in the presence of uncertainty associated with the robot mechanical dynamics and the camera system for both fixed-camera and camera-in-hand configurations. Specifically, we first design a robust controller that compensates for uncertainty throughout the whole robot-camera system and ensures global uniformly ultimately bounded position tracking for the fixed-camera configuration. Under the same class of uncertainty, we then develop a setpoint controller for the camera-in-hand configuration that achieves global uniformly ultimately bounded regulation. Experimental results illustrating the performance of both controllers are also included.

Adaptive set–point control of robotic manipulators with amplitude–limited control inputs

This paper addresses the link position setpoint control problem of n–link robotic manipulators with amplitude-limited control inputs. We design a global-asymptotic exact model knowledge controller and a semi-global asymptotic controller which adapts for parametric uncertainty. Explicit bounds for these controllers can be determined; hence, the required input torque can be calculated a priori so that actuator saturation can be avoided. We also illustrate how the proposed control algorithm in this paper can be slightly modified to produce a proportional-integral-derivative (PID) controller which contains a saturated integral term. Experimental results are provided to illustrate the improved performance of the proposed control strategy over a standard adaptive controller that has been artificially limited to account for torque saturation.

Robust visual-servo control of robot manipulators in the presence of uncertainty

This paper considers the problem of position control of planar robot manipulators via visual servoing in the presence of uncertainty associated with the robot mechanical dynamics and the camera system for both fixed-camera and camera-in-hand configurations. Specifically, we first design a robust controller that compensates for uncertainty throughout the whole robot-camera system and ensures global uniformly ultimately bounded position tracking for the fixed-camera configuration. Under the same class of uncertainty, we then develop a setpoint controller for the camera-in-hand configuration that achieves global uniformly ultimately bounded regulation.

Adaptive tracking control of a wheeled mobile robot via an uncalibrated camera system

This paper considers the problem of position orientation tracking control of wheeled mobile robots via visual serving in the presence of parametric uncertainty associated with the mechanical dynamics and the camera system. Specifically, we design an adaptive controller that compensates for uncertain camera and mechanical parameters and ensures global asymptotic position/orientation tracking.

On global output feedback tracking control of robot manipulators

We revisit the global output feedback (OFB) tracking control problem for rigid-link robot manipulators subject to parametric uncertainty. Motivated by misunderstandings in the literature concerning our previous result, we propose a new global OFB adaptive controller which, in contrast to our previous work, eliminates the need for a post-stability analysis transformation to derive a velocity-independent control strategy. The structure of the new controller along with a new Lyapunov function are used to illustrate global asymptotic link position tracking. Experimental results are included to demonstrate the controller performance.

Global adaptive partial state feedback tracking control of rigid-link flexible-joint robots

This paper presents a solution to the global adaptive partial state feedback control problem for rigid-link, flexible-joint (RLFJ) robots. The proposed tracking controller adapts for parametric uncertainty throughout the entire mechanical system while only requiring link and actuator position measurements. A nonlinear filter is employed to eliminate the need for link velocity measurements while a set of linear filters is utilized to eliminate the need for actuator velocity measurements. A backstepping control strategy is utilized to illustrate global asymptotic link position tracking. An output feedback controller that adapts for parametric uncertainty in the link dynamics of the robot manipulator is presented as an extension. Experimental results are provided as verification of the proposed controller.