Optimizing the number of anti-skid device for vehicle

We can image the shift work of the vehicle in the form of: a) the movement of the unit from the park to the object of work; b) work on the object; c) the movement from the object to the park. Depending on the condition of the roads, as well as the weather conditions of spring and autumn, the driving wheels of the vehicle can be equipped with the hooks just before leaving, on the road or directly at the work site. In any case, it is necessary to spend a certain amount of the shift time for installation and disassembly of the anti-skid device.


Introduction
The characteristics of the undercarriage systems of transport vehicles significantly affect the technical level. The advantages of wheeled propulsion units are obvious compared to crawlers. They are distinguished by their low specific metal consumption and the possibility of using them on highways. Wheeled vehicles provide the best working conditions for the driver and service personnel.
Their works note that the towing properties of vehicles are enhanced by: 1) the use of the entire mass of the tractor; 2) an increase in tire contact with the soil; 3) the development of new design solutions; 4) the development of new technological solutions. The solution to this issue will be reduced to the determination of such number of anti-skid devices, which will ensure the maximum performance of the vehicle in these operating conditions [2,3].
Let's present the shift performance of a vehicle operating without devices, as (1) Then the shift performance of the vehicle working with devices will be determined as: (2) where VT -theoretical speed, m/s; TO -basic working time, hrs; B -vehicle width, m; TC -time required for installation and disassembly of the anti-skid device, hrs.
Consequently, the change in shift performance will be: (3) With the increase in the number of anti-skid devices on the driving wheel, the expression in square brackets of the optimization model changes, having an extremum point [4]. For the full slip mode of the propulsor, equipped with removable hooks, the model of their quantity optimization, according to the increment factor of the shift time, will receive the following form: For general case we have: The resulting model of optimization of the number of antiskid devices graphically represents a curve with an extreme value ( Figure 1).

Materials and methods
The results of the study showed that diamond-shaped intersections at two levels are the safest intersection types. First, the diamond-shaped intersection is simple in layout and provides good visibility for drivers, which greatly reduces the likelihood that the driver can choose the wrong direction to enter or exit. Second, the ramps of the diamond-shaped intersection at different levels have a direct form. Curvy ramps have a higher degree of risk than direct ones. Third, in most cases at the diamond-shaped intersections a minor road passes over the main road.
The research plan includes:  preparation and processing of the obtained experimental material in accordance with GOST 8.207-76. Figure 2 shows the purpose, objectives of research and ways to achieve them.

Discussion
With the rising number of hooks, we observe an increase in the shift time to a certain value, after which it starts to decrease. The maximum value of the increment in these operating conditions of the unit will determine the optimal number of devices on the wheel [7]. In order to get the mathematical model of the optimal number of anti-skid devices on the propulsor from the expression (2), we take the derivative by equating it to zero and substituting the model ( Therefore, after the transformations we get: (6) Analysis of this model shows that the optimal number of anti-skid devices is influenced by the vehicle's basic operation time, device installation and disassembly time, slip coefficients of the wheel with and without hooks [8].
Let's determine the optimal number of hooks on the propulsor for the next levels and intervals of variation of significant factors (Table 1).

Results
The calculated values of the optimal number of hooks on the propulsor according to model (5) showed the following values ( Table 2).  After studying the effect of installation and disassembly time of the anti-skid device on the optimal number of hooks, we should note that regardless of the basic operating time of the vehicle, with an increase in TC, Zopt decreases along the curve with negative acceleration (Figure 3  One of the factors that increase the productivity of the vehicles (as shown by the models [8]) and, consequently, the range of expediency of removable hooks usage, is the time required for installation and disassembly of the anti-skid device [9]. The value of this factor depends on the mass of the removable device, convenience and the connection of its attachment to the wheel rim.
We have developed and manufactured prototypes of removable anti-skid devices with minimal attachment on the wheel rim.  a -0,9…2,0; b -0,6. The anti-skid device for tractiob class 0.9 ... 2.0 consists (Figure 7) from the axis 1, fastened to the wheel rim disk by nuts 3 and fixing the position of the cheek 2, the guide sleeve 4, with the bolt 5, the adjustable stand 6 with the holes 10; hook 7, fixed in the lower groove of the rack using a bolt connection 8, and spring 9.
A device for wheel propulsors consists of a bracket 1 (Figure 7), a pillar 2 fixed to the bracket with the help of bolts 3; a hook 4 connected to the bottom of the rack by a bolt connection 5. To increase the resistance of the bracket, stiffener 6 is welded to bending and torsion moments.

Conclusion
Mitigation of dynamic loads on the wheel disk is achieved by a rubber gasket 7, worn on one of the edges of the bracket.
To attach the device to the wheel rim, it is enough to unscrew one of the disc nuts and, aligning it with the hole in the bracket, fix the device. On average, the installation and disassembly of the device takes 8 ... 12 minutes.
Thus, this analysis of the model for optimizing the number of removable hooks, depending on the operating time of the vehicle, installation and disassembly of the anti-skid device, soil properties by the criterion of traction characteristics of the propulsor, shows its suitability in engineering calculations.