FUNDAMENTAL PRINCIPLES OF OPTIMAL GEAR SHIFT SYNTHESIS THEORY IN AUTOMOBILE STEPPED RATION GEAR TRANSMISSION
Authors: Hashchuk P. , Pelo R. 
Published: October 2019

The laws of gear transmission are practically always transformed into rather illustrative and relatively easy programmed in the controller the so called maps of transmission. But the notion of optimality are prone to misunderstanding.  To avoid this it is suggested a driver opt for himself for the factored technical possibilities of multiprogrammed automated or automatic control of transmission, or at sole discretion to implement a certain programing compromise that in most cases is not disclosed. Thus the system of automated control is subject to uncertainty. There has been no theory able to recommend an irrefutable compromise.

It turned out that alongside with insufficiently optimal laws of gear transmission the so called cycle of shift operation occurs, i.e. excessive or irrational changeability of structure and parameters of transmission which cannot be blocked by the criterion of optimality. To contend this phenomenon the optimal laws are considerably distorted and invalidated. So, why do we strive for optimality? Was it really necessary to create a true model of automobile, search for the sense of ultimate transmission? Are there any other issues possible more important than dynamics, energy saving, purely technical factors that determine the efficiency of transmission? Should we prognosticate artificially created chaos in the control system while programming asystemic errors in the operation of the controller? It is obvious that these questions presuppose substantial negative answers that are to be proved.

However, there are grounds to suggest completely different explanation of gear shift optimality laws: when a driver chosen program of automobile motion is realized we can mention only the energy saving, whereas the requirement of dynamics means “interference” in driver’s actions, “limitation’ of the freedom of choice, decrease in operability within the “drive – automobile” system. This treatment of the sense of transmission automation is firmly grounded. “Dynamics” is based only on the assumption that there exists an indicator of car sensitivity to the driver.

If both paradigms coexist, undoubtedly, everything related to one of them is absolutely false. It is the traditional paradigm that seems false, for it relies on so called map of shifts. Due to this fact in the theory of automated operation of “engine – transmission – automobile” system there has long been ambiguity in the understanding of automobile transmission operation. And this statement is the fundamental, key one in defining really objective principles for the synthesis of automobile transmission operation laws.

The aim of this paper is to reveal the content, evaluate the objectivity and credibly validate both paradigms contesting in the theory of automobile stepped ration gear transmission and constituting the basis of synthesis theory of optimal gear shift laws in these transmissions.

Usually, the problem of gear shift softness is treated outside the general motivation of the gear shift optimization laws. It is considered that the softness of the shift is just a reason of comfort and prevention from harmful dynamic load of transmission. In fact the synchronization of transmission elements rotation under participation of engine is directly connected with transference of energy to automobile’s propulsion units and the accuracy of the desired motion program representation. That is why the effectiveness of synchronization is to be evaluated according to the same criteria as the rationality of the choice of transmissions. It is worth mentioning that in the process of active (with the participation of the engine) operation of synchronization the automobile transmission transforms to the variator that, although it dispels energy in the form of the heat, potentially allows the engine to work longer and under more energy saving modes.

It is proved that the optimization of the gear shift laws should be considered solely according to the criterion of energy saving. Herewith, the organization of the process of shift from one transmission to another should be submitted solely to the laws of energy saving rather than to the requirements of softness that could hardly be formalized. In this case the algorithms of internal combustion engine operation in the process of automobile transmission shift (in the process of clutches slipping) are of great importance.