Optimal gear shift algorithm in the car transmission during its deceleration

Abstract

On the way to improving the car one can not avoid the problem of optimal gear shift in stage transmissions. Typically, the gear (stage) shift laws are distinguished, which are optimal because of fuel efficiency, either in terms of dynamics (speed), or in terms of comfort / safety of the car, etc. And all these types of laws are considered to be special, irreducible to each other. Because of this, in the designs of real automotive transmissions, it is often foreseen for the driver to have several automatic control programs at the same time. But everything that is entrusted to the driver is to some extent the subjective negation of automaticity and optimality. The purpose of the work is to refute such very common system of views on the optimality of transmission control as: it turns out there is a single optimal gear shift law, within which there are no contradictions, at least between energy efficiency requirements and the requirements for the dynamics (or performance) of the vehicle. The basis of the research methodology is the fully motivated principle of non-interference of the automatic transmission control system in the choice of the car movement program - a choice that is largely due to the circumstances and road conditions of the vehicle movement. So, optimizing the gear shift laws, it is necessary to consider the movement program to be predetermined (subject only to the driver), and the consequences of forced deviation from it during the operation of the elements of transmission control should be minimized. Specifically, gear shifting is considered during the car deceleration. Direct involvement of the engine in the process of gear changes is envisaged, that is, the implementation of the principle of active synchronization of the rotation speed of separate parts of the transmission on adjacent gears during their shifting. In this case, the transmission of mechanical energy through the transmission is carried out by a continuous flow. The implementation of the dynamic principles of automation also leads to a decrease in the amount of mechanical energy that is transformed into heat during the skid of gear shift elements (frictions, for example). This makes it possible to increase the durability of the gear-shift elements or to impose lighter requirements in the process of designing the transmission. The described algorithm of the optimal transmission control of the car provides grounds for the formation of motivated guidelines for selecting the moments of gear shift also during purely manual control of the car. The obtained results are quite general, although significant simplifications were introduced into the car model. In particular, the scheme of the gearbox, considered to be very simple, actually fully reproduces the principles of work of the mechanical stage transmission of any structure. The process of gear shifting is so fast that the linearized reproduction of the operating modes of the “engine-transmission” system is quite natural and such that it can not distort the idea of the optimal functioning of the engine-transmission system.