Mirosław Pajor

Unilateral Hydraulic Telemanipulation System for Operation in Machining Work Area

The paper is focused on the minimization of the time transport delay effect which is present in the communication channel of a telemanipulation system. For the minimization of the time transport delay, a prediction block was proposed. The prediction block is characterized by a unitary gain and positive-linear phase shift in a useful frequency spectrum of the system operation. These features allow the block to predict the signal with a constant time and minimizes the gain to a unity level. The use of prediction blocks in the communication channel strongly improved the position tracking abilities of the unilateral system which feature was confirmed in experiments.

Nonlinear inverse modeling with signal prediction in bilateral teleoperation with force-feedback

In the paper a sensor-less control scheme for a bilateral teleoperation system with a force-feedback based on a prediction of an input and an output of a non-linear inverse model by prediction blocks is presented. The prediction method was designed to minimize the effect of the transport delay and the phase shift of sensors, actuators and mechanical objects. The solution is an alternative to complex non-linear models like artificial neural networks which requires complex stability analysis and control systems with high computing power. The effectiveness of the method has been verified on the hydraulic manipulator test stand.

Intelligent Machine Tool – Vision Based 3D Scanning System for Positioning of the Workpiece

The presented innovative vision system is a new solution for quick matching the workpiece reference point using non-contact 3D scanning method, based on structural light patterns [1, 2]. The vision system uses special reference markers [3] and flexible calibration procedure [4] in order to integrate with the CNC machine workspace. Based on 3D geometry of the workpiece, placed on CNC table, the new object coordinate system for tooling process is precisely aligned.At present, the system is in the final phase of laboratory tests confirmed its functionality. In this paper, the results of several tests for 3D scanning quality, scanning recurrence and for positioning recurrence using CNC table will be presented. All the most critical stages of integration with CNC machine will be showed and discussed. The obtained results revealed far improvement in terms of time and simplicity of use, as well as good stability of the system.

Loader Crane Working Area Monitoring System Based on LIDAR Scanner

Segmentation and analysis of the environment using 3D data (point clouds) in real time are dynamically developing the area. Falling prices of depth sensors based on technologies: LIDAR, ToF, RADAR, increasing computing power, growing interest in autonomous vehicles and robots, favor this trend. This paper presents test studies of loader crane working area monitoring system based on the Velodyne VLP-16 LIDAR scanner. Developed system use ground plane estimation and surroundings segmentation algorithms. The ground points filtering algorithm is based on the dot product of vectors as well as interpolation using the RANSAC method. Segmentation algorithm uses angle threshold between points and breadth-first search (BFS) method for determine neighborhood. The proposed system was adapted to operate with sparse LIDAR data in real time. Described system allows for detects human bodies, environmental elements, and monitors changes in the loader crane work area. The effectiveness of developed algorithms was tested on data obtained from loader crane test bench. An experiment showed that segmentation and monitoring loader crane working area in real time even with sparse data is possible. Moreover, the authors discuss other methods used to segmentation sparse point cloud in real time, describe the Velodyne VLP-16 scanner, and presents an outline of current research into HMI interfaces for loader cranes.

Ground plane estimation from sparse LIDAR data for loader crane sensor fusion system

Research on the development of control systems for loader cranes, despite their importance in the industry, is conducted by only a few scientific centers. West Pomeranian University of Technology, Szczecin in collaboration with loader cranes manufacturer — Cargotec company, started research on the multisensory monitoring system for cranes. proposed system also allows you to track the position of the operator. This paper presents the subsystem for ground plane estimation and ground points filtration. The developed algorithm uses data from the Velo dyne LIDAR VLP-16 scanner. The subsystem is designed for real time operation. It is based on the RANSAC algorithm and vector dot product. The effectiveness of the algorithm was compared with other algorithms described in this publication. Tests were carried out on a loader crane test bench at various positions of the LIDAR sensor. Experiments confirms that ground plane estimation results of the proposed algorithm are better than other presented methods.

Real-time ground filtration method for a loader crane environment monitoring system using sparse LIDAR data

The segmentation and analysis of the environment using three-dimensional (3D) data (point clouds) is a dynamically developing area. This article presents a real-time ground filtration method for the loader crane environment monitoring system. The falling prices of depth sensors based on light detection and ranging (LIDAR), time of flight (ToF), radio detection and ranging (RADAR) technologies, and growth-computing power led us to use the Velodyne VLP-16 sensor in the developed system. In the presented filtering solution, we use characteristic scan pattern properties, the dot product of vectors, and interpolation using the RANSAC method. Algorithm performance was evaluated based on real data acquired under different conditions, and the results were compared to known filtration methods. The described algorithm is developed for real-time operation; therefore, the computation time is critical. Furthermore, in this article, we discuss other methods used to extract ground points from the entire point cloud in real time, describe Velodyne VLP-16 scanner and data acquisition methods.

Interactive Control Systems for Mobile Cranes

The paper presents an invented interactive control system for mobile lifting devices, particularly for loader cranes. The proposed innovative system is comprised of modules, output signals from which are sequentially transformed into a commands sequence corresponding to the motion strategy, related to incremental changes of position or motions depending on the distance to the end position. In the system, the commands sequence related to the position of the operating element corresponds to the trajectory optimization strategy in accordance with the positioning time minimization criterion, total length of the path of motion minimization during handling, or maximization of the safety indicator. An innovative processing scheme, using several functional modules, for the interactive control system has been presented, covering also the use of anti-patterns of normalized commands and standardized strategies, and analysis of crane stability. The invented system solves the problem of effectively controlling lifting devices during tasks requiring increased efficiency, safety, speed and precision.

Signal Prediction in Bilateral Teleoperation with Force-Feedback

In the paper a sensor-less and self-sensing control scheme for a bilateral teleoperation system with force-feedback based on a prediction of an input of a non-linear inverse model by prediction blocks was presented. As a part of the paper a method of a time constant estimation of the prediction block was also proposed. The prediction method of an input of an inverse model was designed to minimize the effect of the transport delay and the phase shift of sensors, actuators and mechanical objects. The solution is an alternative to complex non-linear models like NARX or artificial neural networks, which requires complex stability analysis, and control systems with high computing powers. The effectiveness of the method has been verified on the hydraulic manipulator’s test stand.

Intelligent Machine Tool – A Thermal Diagnostic System for a CNC Pretensioned Ball Screw

The paper presents a compensation system of thermal deformation for conventional feed axes applied in CNC machine tools allowing for an effective reduction in the impact of heat generated during its operation on the positioning accuracy of the axis. The result has been achieved by equipping feed screws with thermistor temperature sensors. Wiring sensors was led out through an axial bore in the screw and through a rotating electrical connector to an acquisition device coupled with the control system of the CNC machine. An algorithm based on neural networks was implemented in the machine control system, which allows for the online calculation and compensation of heat deformation of feed screws. The algorithm takes into account a variation of thermal deformation values as a function of the table position and the current distribution of the temperature field of the screw and machine. The paper presents a user-friendly method for implementing algorithms containing neural networks in the machine control system. The proposed compensation method has been verified by measuring the linear accuracy of the feed axis positioning. The obtained results confirm the effectiveness of the proposed method in reducing the impact of thermal deformation errors on the positioning accuracy of the axis in CNC machine tools.

Intelligent Machine Tool: New Manual Programming Techniques

Modern CNC machine tools constitute advanced mechatronic systems. Numerous works are undertaken on the development of new intelligent control systems for CNC machine tools [1–5] equipped with unique diagnostic systems. One of the development directions of CNC control systems is exploring new forms and techniques of operator-machine communication as well as new, simpler machine tool programming procedures. Nowadays, there are many techniques for programming CNC machine tools [6], [7]. These techniques have taken a variety of forms both due to historical limits of technology and various environmental requirements. Despite the existence of complex control systems for operation and programming CNC machine tools or CAD/CAM systems facilitating the generation of a machining strategy for complicated elements, there is a demand for machine tools that are easier to operate, and therefore do not require advanced programming skills for operation.