Leszek Podsedkowski

A new solution for path planning in partially known or unknown environment for nonholonomic mobile robots

Abstract This paper presents the theoretical analysis of different methods, which can be used in online path generation for mobile robots with nonholonomic constraints in a partially known workspace. Then the new method is introduced which works very fast and gives the optimal path in a complex environment. The algorithm of the presented method is based on A∗ graph searching with the nodes placed in the discretized configuration space. This paper is focused on the analysis of different heuristic cost functions and introduces a new statement of this function. The presented method is equipped with the procedures of fast path replanning — very useful in partially known workspaces. The series of simulation tests and experimental results of online control for car-like robot are also discussed.

Telemanipulator Control with Varying Camera Position

Technical University of Lodz in cooperation with the Foundation for Cardiac Surgery Development conducts research on the design and control method of Polish Robin Heart cardiosurgical robots family. One of the major problems in telemanipulation is intuitiveness of control. One of the methods to ensure it is using systems that duplicate master displacement to manipulator displacement. The selection of the proper method when it is not possible to predict what will be the position of the camera observing the work area in relation to the position of the manipulator arm is especially important. Transformations between different coordinate systems must be taken into consideration. Four methods of position copying system implementation tested on RobIn Heart cardiosurgical telemanipulator will be presented in this article. Detailed algorithms will be described and the results of tests determining the duration of certain tasks will be presented.

Data Fusion Using Fuzzy Logic Techniques Supported by Modified Weighting Factors (FLMW)

This article describes a data fusion algorithm that uses fuzzy logic techniques. The algorithm involves weighting factors, the values of which change depending on whether the conditions dictated by processes of fuzzy logic have been met. By modifying the values of weighting factors, one can achieve a measurement signal with expected properties. The article includes a general description of the algorithm and an example of its application. The algorithm was developed for the purposes of data fusion for contactless measurement of the linear and angular position of an automatic laparoscopic device or a laparoscopic camera (hereinafter Laparoscope sleeve or LS).These measurements are used in the article to close the feedback loop on the position within a servomechanism with two degrees of freedom.

Transversal Pneumatic Artificial Muscles

The paper presents an innovative construction of Pneumatic Artificial Muscles. Due to transverse deformation of the muscle, it allows obtaining a linear displacement by changing a diameter of a muscle. The new type of drive, which is represented by this solution, can be used in a robot designed for exploration of a human intestine. On the basis of investigation, there are presented results of a research, differences between traditional and transversal pneumatic muscles and profits of the new construction.

Are the surgeon’s movements repeatable? An analysis of the feasibility and expediency of implementing support procedures guiding the surgical tools and increasing motion accuracy during the performance of stereotypical movements by the surgeon

The developments in surgical robotics suggest that it will be possible to entrust surgical robots with a wider range of tasks. So far, it has not been possible to automate the surgery procedures related to soft tissue. Thus, the objective of the conducted studies was to confirm the hypothesis that the surgery telemanipulator can be equipped with certain routines supporting the surgeon in leading the surgical tools and increasing motion accuracy during stereotypical movements. As the first step in facilitating the surgery, an algorithm will be developed which will concurrently provide automation and allow the surgeon to maintain full control over the slave robot. The algorithm will assist the surgeon in performing typical movement sequences. This kind of support must, however, be preceded by determining the reference points for accurately defining the position of the stitched tissue. It is in relation to these points that the tools trajectory will be created, along which the master manipulator will guide the surgeons hand. The paper presents the first stage, concerning the selection of movements for which the support algorithm will be used. The work also contains an analysis of surgical movement repeatability. The suturing movement was investigated in detail by experimental research in order to determine motion repeatability and verify the position of the stitched tissue. Tool trajectory was determined by a motion capture stereovision system. The study has demonstrated that the suturing movement could be considered as repeatable; however, the trajectories performed by different surgeons exhibit some individual characteristics.

Simulation and experimental results of a new method of mobile robot localization

In this paper simulation and experimental results of a new localization method of a mobile robot are presented. The new method handles both tasks of localization and mapping simultaneously. Its main feature is no assumption about the shape of obstacles. The objects in the workspace can be of any shape. In experimental phase a 3D laser rangefinder was used as a source of data.

Nonholonomic mobile robot path planning with linear computational complexity graph searching algorithm

The A* algorithm and its modifications are commonly used in graph searching for mobile robot path planning. However in case of large open list sizes the A* algorithm needs significant time to find the solution due to the open list sorting procedure which determines the computational complexity of A*. This paper presents a new approach called L* which improves the A* graph searching algorithm and provides linear computational complexity due to the lack of the open list sorting procedure. This is a crucial factor in order to decrease the time consumption for large open list sizes in a graph searching algorithm.

The average 6 DOF path estimation with the use of initial approximation curve

The paper presents the average path estimation algorithm. This algorithm is based on the approximation curve, which shape should by defined as closely as possible to the shape of the analyzed path. With the use of this initial curve, the data space is divided into the intervals. All of the interval paths points are averaged individually. After the calculations, there is only one average point for each path. Next, these average points are averaged to one point in each interval. The set of these averaged points define the average path. Thanks to this algorithm the input paths can be non-linear and independent of time. The analyzed path can begin and end in any point in the 6DOF space, as well as reverse and loop. This paper presents the general model description and example of the use of the presented algorithm.

Compliance force control for Polish cardiosurgical manipulator RobIn Heart

In the paper hybrid control for Polish cardiosurgical robot RobIn Heart 3 has been presented. Classical position-force control with modification introduced by Fisher and Mujtaba has been simulated with dynamics model of this robot. It has been conducted extensive simulation study, which should give an answer to the question, if selected motion patterns, so-called “motion primitives”, could be prepared to support human reactions. Such patterns could give surgeon possibility to make a process of cutting or needling more precisely and with precise force of pressure. Simulation research has confirmed correctness of assumed control solution. It is a point of departure to practical implementation of such control scheme in robot RobIn Heart.

Online navigation of mobile robots using laser scanner

This paper presents a theoretical analysis of the application of different sensors for estimating the current position and orientation of the mobile robot. The paper also presents a new method for such navigation. This method is based on a laser scanner. This sensor determines straight edges of the obstacles (parts of walls), compares them with the previously memorised map of such edges, and estimates location and orientation of the robot. A new concept of gyroscope application is also presented.