Citation: Cardei, P.; Constantin, N.; Muraru, V.; Persu, C.; Sfiru, R.; Vladut, N.-V.; Ungureanu, N.; Matache, M.; Muraru-Ionel, C.; Cristea, O.-D.; et al. The Random Vibrations of the Active Body of the Cultivators. Agriculture 2023, 13, 1565. https://doi.org/10.3390/ agriculture13081565 Academic Editors: Jin He and Caiyun Lu Received: 25 April 2023 Revised: 26 July 2023 Accepted: 31 July 2023 Published: 4 August 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). agriculture Article The Random Vibrations of the Active Body of the Cultivators Petru Cardei 1 , Nicolae Constantin 2 , Vergil Muraru 1, *, Catalin Persu 1 , Raluca Sfiru 1 , Nicolae-Valentin Vladut 1 , Nicoleta Ungureanu 2, * , Mihai Matache 1 , Cornelia Muraru-Ionel 1 , Oana-Diana Cristea 1 and Evelin-Anda Laza 1 1 National Institute of Research—Development for Machines and Installations Designed for Agriculture and Food Industry—INMA, 013811 Bucharest, Romania; petru_cardei@yahoo.com (P.C.); persu@inma.ro (C.P.); raluca_sfiru@yahoo.com (R.S.); vladut@inma.ro (N.-V.V.); matache@inma.ro (M.M.); cornelia.muraru.ionel@gmail.com (C.M.-I.); diana10.cristea@gmail.com (O.-D.C.); eveline_anda@yahoo.com (E.-A.L.) 2 Department of Biotechnical Systems, Faculty of Biotechnical Systems Engineering, National University of Science and Technology Politehnica Bucharest, 060042 Bucharest, Romania; nicu.constantin49@yahoo.com * Correspondence: virgil.muraru@gmail.com (V.M.); nicoleta.ungureanu@upb.ro (N.U.); Tel.: +40-7-4435-7250 (V.M.) Abstract: The article continues the exposition of the results obtained in researching an agricultural machine for processing soil, designed for research with applications including exploitation. The MCLS (complex machine for soil tillage) was designed to research the working processes of the instruments intended for soil processing. The MCLS cultivator is a modulated machine (it can work for three working widths: 1, 2, and 4 m, with tractors of different powers) that is designed to use a wide range of working bodies. The experimental data obtained with the structure with a working width of 1m and the results of their processing within the framework of the theory of random vibrations are presented in this article. The experimental results are analysed as random vibrations of the supports of the active working bodies. As a result, the main characteristics of random vibrations are exposed: the distribution function, the average value, the autocorrelation, and the frequency spectrum. These general results regarding random vibrations are used for several critical applications in the design, execution, and exploitation of some subassemblies and assemblies of agricultural machines of this type. The main applications include estimating the probability of the occurrence of dangerous load peaks, counting and selecting the load peaks that produce fatigue accumulation in the material of the supports of the working bodies, identifying some design deficiencies or defects in the work regime, and estimating the effects of vibrations on the quality of soil processing. All of the outcomes are composed of applications in MCLS research and exploitation. The applications pursue well-known objectives of modelling the working processes of agricultural machines: safety at work, increasing the quality of work, optimising energy consumption, and increasing productivity, all in a broad context to obtain a compromise situation. The material and the method are based on experimental data acquisition, processing, and interpretation. Keywords: random; vibrations; tillage; tools; complex; cultivator 1. Introduction The phenomena and work processes encountered in agriculture involve, for the most part, important areas of the field of biology (environment, soil, plants, animals, etc.), which is “living”. According to all the assessments in the literature, the field of life is a field of un- predictability, uncertainty, randomness, and probability. According to [1], “understanding randomness is essential for modern life, as it underpins decisions under uncertainty”. Random phenomena are treated in physics through theories different from determin- istic ones, using the concepts of probability theory and statistics. In [2], it is shown that “in mechanical engineering, random vibration is motion that is non-deterministic, meaning that future behaviour cannot be precisely predicted. The randomness is a characteristic Agriculture 2023, 13, 1565. https://doi.org/10.3390/agriculture13081565 https://www.mdpi.com/journal/agriculture