In memory of the teacher and friend.

Alexey Grigorievich Ivakhnenko was born on March 30, 1913. He was outstanding scientist and remarkable person. Alexey Grigorievich Ivakhnenko set up his scientific school, brought up hundreds of candidates and tens of doctors of sciences. His personal merits before science are great and were acknowledged worldwide. Alexey Grigorievich was the first to write a domestic monograph on technical cybernetics which was repeatedly released abroad, had tens of other books published. These books dealt with results of his research in the field of control theory, mathematical modeling and informatics. Without making an attempt to describe in frames of this assay everything made by him we will consider only his contribution to the invariance theory of control systems whose history features a lot of grave events. We will remind a reader that by the term “invariance theory of control systems” is meant the method of control synthesis of a dynamical system which ensures the independence (invariance) of a controlled coordinate from disturbances acting upon this system. In the 50s of the last century at the Institute of Electrical Engineering of AS of Ukraine A.G. Ivakhnenko successfully carried out a large cycle of theoretical and practical investigations which convincingly demonstrated the efficiency of application of compensating connections which allowed one to prove in practice the possibility of attaining the invariance effect, speaking more precisely, quasiinvariance in industrial samples of control systems due to velocity of an asynchronous motors. The value of this result consisted in the fact that at that time it was one of few examples of invariant theory ideas implemented “in iron” and which was in great demand among its supporters.