Marcin Kiełczewski

Trajectory tracking for a mobile robot with skid-slip compensation in the vector-field-orientation control system

Trajectory tracking for a mobile robot with skid-slip compensation in the vector-field-orientation control system The article is devoted to a motion control problem for a differentially driven mobile robot in the task of trajectory tracking in the presence of skid-slip effects. The kinematic control concept presented in the paper is the Vector Field Orientation (VFO) feedback approach with a nonlinear feed-forward skid-slip influence compensation scheme. The VFO control law guarantees asymptotic convergence of the position tracking error to zero in spite of the disturbing influence of skid-slip phenomena. The paper includes a control law design description, stability and convergence analysis of a closed-loop system, and practical verification of the proposed control concept. The experimental results illustrate control quality obtained on a laboratory setup equipped with vision feedback, where the Kalman filter algorithm was used in order to practically estimate skid-slip components.

Vector-Field-Orientation Tracking Control for a Mobile Vehicle Disturbed by the Skid-Slip Phenomena

The paper is devoted to the trajectory tracking control task for a differentially-driven vehicle moving on a plane surface under conditions of the persistent skid-slip phenomena. The Vector Field(s) Orientation (VFO) control strategy, presented originally for undisturbed case in Michałek and Kozłowski (IEEE Trans Control Syst Technol 18(1):45–65, 2010), has been reformulated here to the new disturbed motion conditions. The extension of the VFO strategy relies on introduction of the nonlinear skid-slip influence compensator in the feed-forward loop, which in practical implementation involves the real-time estimation of the skid-slip velocities and their time-derivatives. The approach considers the skid-slip effects solely on the kinematic level avoiding the need of modeling a complicated phenomenon of the wheels-ground interaction. Theoretical analysis shows the asymptotic tracking ability for the position trajectory with boundedness of the orientation error. Experimental results included in the paper reveal substantial tracking quality improvement resulting from the utilization of the proposed skid-slip influence compensator.

Visual tracking of surgical tools for laparoscopic surgery

In this paper a concept of vision feedback in control of position of surgical tools for minimal invasive surgery (MIS) is presented. Vision feedback of robotic laparoscope positioning system for MIS is based on recognition of surgical tools on the image coming from a laparoscope camera. This information has to be used for automatic moving of camera during such operation. This is particularly useful in surgery, where the tool executes only small displacements. For laparoscopic surgeon it is very most important to keep position of the surgical tool in center of the image. In the paper, experimental results obtained using described method are presented. The prototype surgery telerobotic system is based on the Staubli robot equipped with laparoscopic camera mounted at the force-torque sensor.

The Concept of Passive Control Assistance for Docking Maneuvers With N-Trailer Vehicles

We present a concept of passive control-assistance system, which can help a human driver in precise maneuvers with a tractor-trailer vehicle in the task of docking with the last trailer. The novel approach is developed for truly N-trailer vehicles comprising a car-like tractor and arbitrary number of on-axle or off-axle hitched trailers. Passivity of the proposed assistance system results from the fact that it does not interact directly with a vehicle, but acts solely as an advisor suggesting control action to a human operator through a passive human-machine interface. The key role in the concept plays the cascaded Vector-Field-Orientation feedback control law responsible for computation of the efficient control strategy for a driver based on a feedback from a current vehicle configuration. The passive assistance system has been functionally compared with an alternative active control assistance proposed in the literature. This paper reports the results of experimental tests conducted with a laboratory-scale vehicle, which illustrate efficacy of the cooperation between a driver and a control assistant in the task of backward docking with three trailers.

Cascaded VFO Control for Non-Standard N-Trailer Robots

Articulated mobile robots consisting of a tractor and passively off-hooked trailers belong to a class of highly nonlinear, nonholonomic, structurally unstable, differentially non-flat, and underactuated dynamic systems. Due to the mentioned properties of their kinematics, motion control problems related to N-trailer robots (N-trailers) are non-trivial and challenging. Cascaded control strategy presented in this paper provides unified solution to the set-point and trajectory tracking control tasks for articulated robots equipped with arbitrary number of passively off-axle hitched trailers. Practically useful features of the proposed controller come from its high scalability and from application of the Vector-Field-Orientation (VFO) controller in the outer loop, which ensures fast errors convergence and simplicity of control implementation and tuning. Control input limitations of the robot are directly taken into account by utilization of a simple velocity scaling procedure which preserves an instantaneous motion curvature of a tractor. Description and theoretical substantiation of the concept are followed by the results of experimental validation tests conducted with usage of a 3-trailer semi-autonomous vehicle.

Cascaded VFO Set-Point Control for N-Trailers With On-Axle Hitching

Set-point control task for N-trailers corresponds to the practical problem of parking/docking maneuvers performed by a vehicle comprised of an active tractor and N passively interconnected trailers. So far, solutions to the automated parking problem for N-trailers have been formulated mostly using highly nonlinear local transformations of vehicle kinematics into the chained form. Inherent limitations of this approach motivated the authors to propose an alternative cascaded control solution with the Vector-Field-Orientation controller used in the outer loop. The new control law proposed in this brief does not involve any auxiliary model transformation and is highly scalable. The concept has been verified by simulations and results of experimental trials conducted with a three-trailer vehicle.

Helping a driver in backward docking with N-trailer vehicles by the passive control-assistance system

The paper presents a control-assistance system devised for human drivers of articulated vehicles equipped with arbitrary number of trailers mounted in the off-axle manner. The proposed assistance system is passive, which means that it does not interact directly with a vehicle, but it only suggests control action to a human operator solely by a (passive) human-machine interface (HMI). In contrast to the active assistance systems proposed for N-trailers in the literature, the passive assistant does not require installation in a vehicle any high-end actuation subsystems like steer-by-wire or cruise control. The concept presented in the paper utilizes the cascaded VFO control law as a control-assistance function and the HMI with a simple and intuitive graphical interface, which allows a driver to focus an attention only on a single bar-like indicator. The system has been devised for N-trailer vehicles with a tractor of differentially-driven or car-like kinematics. Effectiveness of the assistance system has been illustrated by experimental results obtained with a laboratory-scale vehicle.

Modular architecture of the multi-robot system for teleoperation and formation control purposes

In this paper architecture of the control system for the multiple mobile robots is presented. It was designed for teleoperation and multiagent algorithm tests. Subsystems are connected with wired or wireless links depending on their mobility and distance. The modules, their software and hardware interfaces were designed to make the system easily modifiable as different algorithms require less or more sensors, interaction, communication and computing power. The goal was to design a system on which a large number of control algorithms can run.

Vision Feedback in Control of a Group of Mobile Robots

This article is devoted to the vision system, which is an integral part of control system for mobile robots soccer team. The paper describes an experimental test bed used for real-time image acquisition, processing, and recognition of objects placed on the 2D surface. Description of specific features of objects being recognized, which are controlled and opponent team robots as well as a ball has been also included. Filtering methods used to improve quality of the image received from camera have been presented. The paper also shows a new heuristic algorithm, invented for objects recognition on the scene, playground in our case. The algorithm has been implemented, experimentally verified and quality of measurement has been estimated.

Measurement and Navigation System of the Inspection Robot RK-13

Specialized robots designed for performing functions which are known in advance have been the subject of intensive development recently. These functions depend on the domain, where the mentioned specialized constructions are used. Applications come mainly from areas which are dangerous for humans or where high manipulation precision is required. Many research papers are devoted to applications of robots in medicine. In such cases a robot manipulator can take place of a surgeon’s hand or assists in laparoscopic operations, e.g. following movement of surgical tools in the abdominal cavity and delivering images to the operator [1]. Inspection robots belong to another group of specialized robots [2, 3]. They perform examination of application-dependent infrastructure through measurement of specified parameters. Therefore, such robots are equipped with suitable measurement and navigation systems. Besides that, an inspection robot has to be equipped with a locomotion system.