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In the analysis of vibration systems, classical transfer functions are used. Usually, it is the ratio of Fourier or Laplace transforms. The wavelet transfer function is proposed in this work. In this paper, the wavelets transfer function is the ratio of output and input wavelet transforms. It is considered as a distinctive correlation of the output and input system signals. The wavelet transform consists of coefficients, where the first is a scale and second time shift. To get input and output signals in the human body-seat system the dedicated test stand was made. The stand consists of a seat, moved by special shaker, which is used as a mechanical vibration device. The control program included in the source file is taken to imitate angular position of the engine. Motor shaft is connected with exciter's moving parts and stand base, which influences directly on the seat position. The disturbance signal usually simulates a horizontal road influence on a driver. It can be considered as a low-frequency signal. It is measured by accelerometers called inertial sensors, which are placed on the platform of the shaker. The output signal is measured by an accelerometer placed on a seat and on the human head. Both signals are recorded by the Inertia Studio software wireless in the real time. After the measurement, the signals are transformed into wavelet coefficients by using Matlab package functions. The transfer function and its visualization are presented in two dimensions scale-time. The scale is related to frequency (pseudo-frequency). By the transfer function it is possible to analyze the systems, evaluate safety, compare the systems, and many more.

(1) Background and purpose: SPIDER (Strengthening Program for Intensive Developmental Exercises and activities for Reaching health capability) is dedicated for patients suffering from Cerebral Palsy, Sclerosis Multiplex, Spinal Bifida, Spinal Muscular Atrophy and strokes. Authors proposed a computer model for the evaluation patient’s condition and the rehabilitation progress. (2) Methods: The 2-year-old and 76-year-old patients with neurological problems, who underwent individual therapy included balancing and coordination practising with SPIDER device. The model comparing the forces, which act during the therapy process, such as the expander and gravity forces, was worked out using Matlab software. (3) Results: The model allowed controlling the changes into the patients centre of gravity forces continuous adjustment and postural stability during any patient’s movement. After rehabilitation sessions, lasted for 28 days during which patients received the progress information and the therapist got the numeric data, regarding the period of the therapy. (4) Conclusions: The first patient was able to move, dramatically improved the ability to balance and coordination. The second one presented change in gait, improvement in mobility, motor function and decreased fall risk. The proposed computer model gives information about the forces acting to the patient body. The physiotherapist can evaluate the progress of patient verticalization and receive information, in the form of numbers and charts.

It is assumed in the paper that the signals in the enclosure in a transient period are similar to a noise induced by vehicles, tracks, cars, etc. passing by. The components of such signals usually points out specific dynamic processes running during the observation or measurements. In order to choose the best method of analysis of these phenomena, an acoustic field in a closed space with a sound source inside is created. Acoustic modes of this space influence the sound field. Analytically, the modal analyses describe the above mentioned phenomena. The experimental measurements were conducted in the room that might comprise the closed space with known boundary conditions and the sound source Brüel & Kjaer Omni-directional type 4292 inside. To record sound signals before the field's steady state was reached, the microphone type 4349 and the 4-channel frontend 3590 had been used. The obtained signals have been analysed by using two approaches, i.e. Fourier and the wavelet analysis, with the emphasis on their efficiency and the capability to recognise important details of the signal. The results obtained for the enclosure might lead to the formulation of a methodology for an extended investigation of a rail track or vehicles dynamics.Keywords: modal analysis, short-time Fourier transform, wavelet transform, acoustic signal processing.

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(1) Background: The purpose of this study was to evaluate the analysis of measurements of bioelectric signals obtained from electromyographic sensors. A system that controls the speed and direction of rotation of a brushless DC motor (BLDC) was developed; (2) Methods: The system was designed and constructed for the acquisition and processing of differential muscle signals. Basic information for the development of the EMG signal processing system was also provided. A controller system implementing the algorithm necessary to control the speed and direction of rotation of the drive rotor was proposed; (3) Results: Using two muscle groups (biceps brachii and triceps), it was possible to control the direction and speed of rotation of the drive unit. The control system changed the rotational speed of the brushless motor with a delay of about 0.5 s in relation to the registered EMG signal amplitude change; (4) Conclusions: The prepared system meets all the design assumptions. In addition, it is scalable and allows users to adjust the signal level. Our designed system can be implemented for rehabilitation, and in exoskeletons or prostheses.

Purpose:The article aims to discuss the authors' own experiences and literature review on the topic of small communities of additive production in COVID-19 conditions and propose an improvement of emergency procedures in situations of global threat. Design/Methodology/Approach: Its object is organizing and analyzing the experience gained during the production of healthcare products in 3D technology during the first wave of the COVID-19 pandemic. Findings: Further objects include identifying problems, proposing solutions, signaling problems to be solved, improving the efficiency of managing the production and distribution of health protection products, and improving the energy efficiency of the production process. Practical Implications: Structured conclusions and the resulting proposals for activities in the production and distribution of health protection products in situations of global life threat formulated further research goals.Originality/Value: An in-depth analysis of the literature on the subject and the research results presented in the article indicate the need for further research on the concept of optimization of the production process in the context of the temporary market demand for specific products. The article presents a proposal for a model that allows the use of incremental techniques and cost optimization depending on the market demands.

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