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The article analyzes the criteria for using mobile diagnostic stations for mandatory technical inspections of cars. Mandatory technical inspection of passenger cars is available in all EU countries. In Ukraine, mandatory technical inspection for passenger cars was canceled in 2011. Currently, mandatory technical inspection is provided only for commercial vehicles: buses, trucks, licensed taxis.Having signed the association agreement with the EU in 2014, Ukraine undertook to return the technical inspection for all car owners. This requirement is contained in the 40th and 45th EU directives. The state must implement this obligation no later than five years after the entry into force of the agreement in full (until September 2022). However, armed aggression against the state postponed the resolution of this issue, probably until the end of the war.In total, there are more than 10 million cars in Ukraine. There are more than 800 technical control points in the registry that have the right to carry out technical inspections, which is clearly not enough. It can be assumed that when technical inspection is introduced, out of 10 million cars, half (5 million cars) need to be inspected immediately. At each point, at the rate of 5 million cars per year, there are about 6.25 thousand vehicles (520 per month, or 23-24 per day. This is quite a heavy load. In addition, as a result of hostilities, the number of points is even smaller. Good mobile diagnostic stations (МDS) are an alternative to stationary stations.The advantages of МDS are as follows: the operation of the station does not require a production room; the cost of the PDS is much lower than a stationary control point; availability of serial samples of mobile stations (for example, MANA); the possibility of carrying out checks at the locations of cars. In order to determine the expediency of using МDS of different designs during technical inspections of cars, they were compared according to economic criteria. These criteria take into account the peculiarities of using the МDS to check the cars of organizations and cars belonging to individual owners in different conditions (city or countryside).

The article deals with the issues of modeling conditions for obtaining diagnostic information when checking the braking properties of cars on a roller stand.As many studies show, roller stands of inertial type provide the most reliable information about the technical condition of the car. This concern, first of all, the parameters that determine the accuracy of simulation on the stand of real speed and thermal conditions. The accuracy of diagnosing the brake system of a car on an inertial test bench depends on many factors. One of the determining factors is the value of the reduced masses of rotating elements in the "car-stand" system: rollers, wheels and car transmission parts. The main design parameter of the inertial roller stand is the diameter of the roller. The reduced mass of the transmission can be determined by measuring the moments of inertia of its individual parts and bringing them to a given axis. But this is a laborious process and takes a lot of time. At the same time, the reduced mass of the transmission is also variable due to the wear of parts. Therefore, methods are required to determine the reduced mass of the transmission of a particular vehicle, regardless of the degree of wear of parts.To determine the reduced mass of the transmission, two modes of acceleration of the car on the stand are used: acceleration from the drive of the stand, while two wheels of the car rotate; acceleration from the stand drive, in which one wheel of the car rotates. The analysis of these modes is made and the equations for determination of the reduced mass of transmission are made.The analysis of changes in the moments of inertia of the wheel and rotating parts of the car, as well as the radius of the wheel is carried out. Based on this, the general variation of the reduced mass of the wheel and associated rotating parts of the vehicle is presented. This variation can have a significant impact on the accuracy of diagnosis. The optimal way to compensate for this uncertainty may be to increase the reduced mass of the stand so that the proportion of the reduced mass of the wheel and the associated rotating parts of the car is a small part and introduces an error no more than acceptable.

The scheme of energy transmission from the engine to the wheels of the car is considered. It is indicated that the dynamics of the vehicle when driving in low gears is significantly influenced by the value of the moment of inertia of equivalent masses. For a passenger car, when driving in first gear, the equivalent weight can increase up to 28%. In the literature, inertial masses are determined approximately. The article proposes a simple technique for assessing the moments of inertia of the main parts (wheels, transmission, engine) without disassembling the car. The essence of the method is to measure the deceleration during free run of the car with the vehicle's wheels hanging, and then without the wheels. A system of equations for the power balance of the vehicle run-out in 3rd and 4th gears of the gearbox with open clutch is compiled. When drawing up the equation, it was assumed that with the same engine speed and the same throttle opening, the engine torque would be the same. Formulas are obtained for calculating the moment of inertia of the wheels and the variable part of the transmission, according to which the inertial mass of the engine is calculated without the need to remove it from the machine. The article describes the experimental research methodology applied to the Hyundai i30 car with a working volume of 1.4 liters, manufactured in 2007. In the course of the experiment, the engine speed was measured through the OBD II connector, using the ELM 327 adapter and the ScanMaster-ELM program, the vehicle on-road speed using the Garmin eTrex 30 navigator, and the wheel revolutions were recorded on video. During the experiment, the condition of the tires Nokian Nordman SX 195/65 R15 91H was monitored, for which the residual depth of the tire tread pattern, pressure, moment of inertia were determined (by the bifilar suspension method). Based on the results of the experiment, the developed mathematical model was used to calculate the moment of inertia of the rotating parts of the Hyundai i30 in different gears. The result of the study allows you to establish the actual state of the rotating parts of the car, the knowledge of which increases the accuracy of determining the performance characteristics. The technique can be used to diagnose the conditions of transmission elements and car wheels. The technique does not require the use of complex stands and expensive devices.

The article proposes a method for assessing the change in the braking properties of passenger cars during operation following a change in the main characteristic of the brake system - the coefficient of distribution of braking forces between the axles of vehicles, both equipped and not equipped with tracking systems for the braking process by installing brake force regulators in the brake circuits, working according to different laws of changing the drive pressure. The aim of the work is a comparative assessment of the braking efficiency of passenger cars using the example of Lanos cars, the braking systems of which are equipped with various devices for changing the coefficient of distribution of braking forces between the axles, under changing operating conditions. It is known that braking efficiency is an indicator characterizing the braking properties and the ability of a car to maintain a given law of motion during braking, which is determined both by the nature of the adhesion properties of the wheels to the road and the capabilities of the braking system itself to implement these properties. Since the operating conditions of passenger cars significantly affect the braking properties, in order to ensure the required braking efficiency, it is necessary to take into account the change in the primary distribution coefficient of the braking forces generated by the braking mechanisms and the change in their implementation during the operation period. In order to assess the change in the braking properties in the general case of the operation of a passenger car, the dependence of the actual coefficient of distribution of braking forces between the axles on the braking coefficient was proposed. Moreover, the value of the coefficient of distribution of braking forces between the axles depends both on the type of laws of regulation of braking forces and on the residual values of the parameters of braking systems that determine these laws. These dependences on the parameters of the braking systems and the parameters of the passenger car in operation are a function of the goal for determining the residual output characteristics of its braking system.

Decision-making in solving the problems of auto technical examination of road accidents (road accidents) is carried out in conditions of incomplete information, ie in conditions of uncertainty, which may be stochastic or fuzzy in nature, and therefore is compositional. When forming expert opinions of auto technical examination of road accident the general uncertainty is formed due to uncertainty of the chosen structure of model of road accident, experimental data, error of measuring devices, adequacy of model of road accident, uncertainty of indications of witnesses and other proofs, competence and honesty of the expert. The calculation of vehicle parameters in motor vehicle expertise in the vast majority of cases is performed without estimating the error of the results, which does not meet the requirements of the Law of Ukraine "On Metrology and Metrological Activity" and determines the relevance of improving methods of solving road accident technical examination. The paper reveals the prospects of improving the existing methods of assessing the effectiveness of braking of wheeled vehicles, as the main way to prevent accidents in road transport, which is regulated by the current Traffic Rules. The basic theoretical dependences which form a basis of the improved technique of estimation of parameters of movement of cars at braking are presented. Analysis of the results of the calculations shows that by taking into account the design of the braking system, type and condition of tires used in assessing braking efficiency, the improved technique avoids the same solutions within one category of vehicles, and taking into account stochastic and fuzzy uncertainty narrows the range of possible solutions by 49.4 %. The probability of occurrence of type I errors is reduced by 1.75-18.5%, and type II errors - by 43.1-67.8%.

The article discusses the issues of modeling conditions for obtaining diagnostic information about complex objects. As an example, the study of the braking qualities of four-wheel drive cars on an inertial roller stand is considered. Diagnosing the technical condition of cars from the point of view of traffic safety is one of the most important problems. This is especially important for systems whose technical condition affects traffic safety: especially braking systems. Foreign and domestic experience testifies to the effectiveness of instrumental control. The diagnostic equipment includes roller stands, on which you can check the braking properties of cars. As shown by many studies, in particular, carried out at the Department of Technical Operation and Service of Automobiles, KhNADU (HADI), inertial stands provide more reliable information about the technical condition of the car. Such stands allow you to reproduce the real speed and thermal modes of the brakes (especially those equipped with ABS). To improve the accuracy of diagnosing a car on a roller stand, it is necessary to have an idea of the nature of the interaction of the car wheels with the rollers. The studies of wheel rolling on the stand rollers have been carried out by many authors since the 80s of the last century. However, all these studies were carried out on uniaxial stands and for mono-drive vehicles. Nowadays, a large number of passenger cars have four-wheel drive. Rolling of the wheels of such cars on rollers and their interaction has practically not been studied. Therefore, a return to the study of this issue is relevant. A power model of the system of interaction between the car and the stand has been developed, taking into account the design features of the stand and the design features of the car's suspension. The power model of the system under consideration contains the equilibrium equations of the body and two bridges and the equations of motion of the rollers and wheels of the car. Based on the results of the analysis of the acting forces in the "car-stand" system, the braking moments on the wheels M and the coefficients of the use of the load q during the braking tests of a 4x4 vehicle were determined. The obtained research results allowed to improve the theory of interaction of a car wheel with the rollers of an inertial diagnostic stand.

Fuel efficiency is one of the indicators for evaluating the efficiency of rolling stock. The article discusses the main reasons that determine the need to assess the fuel efficiency of road vehicles during their operation. An analysis of recommendations for the accuracy of measuring vehicle parameters in regulatory documents was given. The goal of the work was formulated, which is to develop measures to improve the accuracy of measurements during bench tests of cars. The main features of measuring fuel consumption on a simulation stand with running drums were considered. Formulas for calculating fuel travel on the road and on the stand with running drums were presented. A criterion for the similarity of road and bench tests for the fuel efficiency of a car was determined. The factors that influence the measurement of fuel consumption were considered. The general measuring scheme of the simulation bench was drawn up. The components of the load-speed modes for the stand operation were analyzed. A metrological assessment was made of the equipment used to measure the torque and rotation speed of the drive shaft of the running drums. A diagram of the calibration process of a strain gauge beam was given, which is used to measure the torque on the running drums of the stand and the wheels of a car. An assessment was made of the regularity of the change in the output channel of the measuring signal from the torque. The characteristic of the relative error was obtained for two ranges of load measurements. The influence of the frequency and number of successive measurements on the convergence of the accuracy of determining the fuel consumption, speed and load of the vehicle during bench tests was established. The optimal measurement time was obtained with an acceptable accuracy. The general dependence of the total error in measuring fuel consumption on a stand with running drums was obtained, taking into account the accuracy of measuring, processing and sampling the signal. The influence of the sampling frequency of the analog-to-digital conversion on the measurement accuracy was assessed. Conclusions and recommendations were developed, which indicated the main avenues for further research.

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.