The paper addresses optimal control problem of mobile manipulators. Dynamic equations of those mechanisms are assumed herein to be uncertain. Moreover, unbounded disturbances act on the mobile manipulator whose end-effector tracks a desired (reference) trajectory given in a task (Cartesian) space. A computationally efficient class of two-stage cascaded (hierarchical) control algorithms based on both the transpose Jacobian matrix and transpose actuation matrix, has been proposed. The offered control laws involve two kinds of non-singular terminal sliding mode (TSM) manifolds, which were also introduced in the paper. The proposed class of cooperating sub-controllers is shown to be finite time stable by fulfilment of practically reasonable assumptions. The performance of the proposed control strategies is illustrated on an exemplary mobile manipulator whose end-effector tracks desired trajectory.

The paper presents the summary of research on polymer melt particle motion trajectories in a disc zone of a screw-disk extruder. We analysed two models of its structure, different in levels of taken simplifications. The analysis includes computer simulations of material particle flow and results of experimental tests to determine the properties of the resultant extrudate. Analysis of the results shows that the motion of melt in the disk zone of a screw-disk extruder is a superposition of pressure and dragged streams. The observed trajectories of polymer particles and relations of mechanical properties and elongation of the molecular chain proved the presence of a stretching effect on polymer molecular chains.

Beamforming is an advanced signal processing technique used in sensor arrays for directional signal transmission

or reception. The paper deals with a system based on an ultrasound transmitter and an array of

receivers, to determine the distance to an obstacle by measuring the time of flight and – using the phase

beamforming technique to process the output signals of receivers for finding the direction from which the

reflected signal is received – locates the obstacle. The embedded beam-former interacts with a PID-based

line follower robot to improve performance of the line follower navigation algorithm by detecting and

avoiding obstacles. The PID (proportional-integral-derivative) algorithm is also typically used to control

industrial processes. It calculates the difference between a measured value and a desired set of points, then

attempts to minimize the error by adjusting the output. The overall navigation system combines a PID-based

trajectory follower with a spatial-temporal filter (beamformer) that uses the output of an array of sensors to

extract signals received from an obstacle in a particular direction in order to guide an autonomous vehicle

or a robot along a safe path.

In this paper, the author presents the possibility of using phase trajectory for detecting damage in an axial piston pump. The wear on main part of pump elements, such as the rotor and the valve plate, was investigated, and phase trajectories were determined based on vibration signal measured in three directions on the pump's body. In order to obtain a quantitative measure of the analyzed trajectory, the At_{p,i} parameter was introduced, and the relation between this parameter and the wear on the pump's parts was determined.

A method of planning collision-free trajectory for a mobile manipulator tracking a line section path is presented. The reference trajectory of a mobile platform is not needed, mechanical and control constraints are taken into account. The method is based on a penalty function approach and a redundancy resolution at the acceleration level. Nonholonomic constraints in a Pfaffian form are explicitly incorporated to the control algorithm. The problem is shown to be equivalent to some point-to-point control problem whose solution may be easier determined. The motion of the mobile manipulator is planned in order to maximise the manipulability measure, thus to avoid manipulator singularities. A computer example involving a mobile manipulator consisting of a nonholonomic platform (2,0) class and a 3 DOF RPR type holonomic manipulator operating in a three-dimensional task space is also presented.

Many real-time systems can be described as cascade space-state models of different orders. In this paper, a new predefined controller is designed using a Strongly Predefined Time Sliding Mode Control (SPSMC) scheme for a cascade high-order nonlinear system. The proposed control scheme based-on SMC methodology is designed such that the system states reach zero within a determined time prior to performing numerical simulation. Moreover, Fixed Time Sliding Mode Control (FSMC) and Terminal Sliding Mode Control (TSMC) schemes are presented and simulated to provide a comparison with the proposed predefined time scheme. The numerical simulation is performed in Simulink/MATLAB for the proposed SPSMC and the other two existing methods on two examples: second and of third order to demonstrate the effectiveness of the proposed SPSMC method. The trajectory tracking of the ship course system is addressed as an example of a second-order system. Synchronization of two chaotic systems, Genesio Tesi and Coullet, is considered as an example of a third-order system. Also, by using two performance criteria, a thorough comparison is made between the proposed predefined time scheme, SPSMC, and the two no predefined time schemes, FSMC and TSMC.

The present paper examines how, at a time of post EU-enlargement migration, female Polish migrants in the UK act within, despite and against the social structure of gender regimes in the origin and host societies and how female migrant agents are actively mediating structures in a quest to fulfil their as-pirations. Biographical narrative interviews conducted with female Polish migrant workers in the UK and semi-structured expert interviews provide the empirical data for the analysis of how employment trajectories in migration can challenge or reinforce gender roles, and of the role of female migrants’ agency. The paper shows how some women are limited in their opportunities by gender roles and fa-milial obligations, while others are able to progress professionally either by entering a typical ‘mi-grant’ sector, by undertaking UK education, or by starting their own businesses, challenging the gendered expectations they face. The paper thus contributes to the discussion on female migrants as disadvantaged migrant workers or as active agents of change.

This paper proposes a method for offline accurate ball tracking for short volleyball actions in sport halls. Our aim is to detect block touches on the ball and to determinate accurate trajectory and impact positions of the ball to support referees. The proposed method is divided into two stages, namely training and ball tracking, and is based on background subtraction. Application of the Gaussian mixture model has been used to estimate a background, and a high-speed camera with a capture rate of 180 frames per second and a resolution of 1920 × 1080 are used for motion capture. In sport halls significant differences in light intensity occur between each sequence frame. To minimize the influence of these light changes, an additional model is created and template matching is used for accurate determination of ball positions when the ball contour in the foreground image is distorted. We show that this algorithm is more accurate than other methods used in similar systems. Our light intensity change model eliminates almost all pixels added to images of moving objects owing to sudden changes in intensity. The average accuracy achieved in the validation process is of 0.57 pixel. Our algorithm accurately determined 99.8% of all ball positions from 2000 test frames, with 25.4 ms being the average time for a single frame analysis. The algorithm presented in this paper is the first stage of referee support using a system of many cameras and 3D trajectories.

Adaptive locomotion over difficult or irregular terrain is considered as a superiority feature of walking robots over wheeled or tracked machines. However, safe foot positioning, body posture and stability, correct leg trajectory, and efficient path planning are a necessity for legged robots to overcome a variety of possible terrains and obstacles.Without these properties, anywalking machine becomes useless. Energy consumption is one of the major problems for robots with a large number of Degrees of Freedom (DoF). When considering a path plan ormovement parameters such as speed, step length or step height, it is important to choose the most suitable variables to sustain long battery life and to reach the objective or complete the task successfully.We change the settings of a hexapod robot leg trajectory for overcoming small terrain irregularities by optimizing consumed energy and leg trajectory during each leg transfer. The trajectory settings are implemented as a part of hexapod robot simulation model and tested through series of experiments with various terrains of differing complexity and obstacles of various sizes. Our results show that the proposed energy-efficient trajectory transformation is an effective method for minimizing energy consumption and improving overall performance of a walking robot.

The main objective of this article is to obtain equations of motion of the spin–stabilized projectile in the presence of non–constant wind. Introducing models allowing utilization of inhomogeneous wind is dictated by new possibilities created by the use of e.g. lidars in the Fire Control Systems (FCS). Constant feed of wind data can replace meteorological messages, increasing the FCS effectiveness. Article contains results of projectile flight simulations which indicate the positive effect that the derived explicit form of the model has when considering software development for modern Fire Control Systems.