ISSN 1068-3712, Russian Electrical Engineering, 2017, Vol. 88, No. 6, pp. 366–371. © Allerton Press, Inc., 2017.
Original Russian Text © P.G. Kolpakhch’yan, V.G. Shcherbakov, A.E. Kochin, A.R. Shaikhiev, 2017, published in Elektrotekhnika, 2017, No. 6, pp. 48–54.
Sensorless Control of a Linear Reciprocating Switched-Reluctance
P. G. Kolpakhch’yan
*, V. G. Shcherbakov
, A. E. Kochin
, and A. R. Shaikhiev
Donskie Tekhnologii, Novocherkassk, Russia
South Russian State Polytechnic University, Novocherkassk, Russia
Rostov State Transport University, Rostov-on-Don, Russia
Received May 16, 2016
Abstract—It is proposed to use a simple switched-reluctance electric machine that does not have windings or
permanent magnets on a movable part to develop a linear reciprocating electric machine intended for use as
an electric generator together with a free-piston internal-combustion engine. It is noted that one of the most
difficult problems in the development of such a linear electric machine is the development of a control sys-
tem. A sensorless control algorithm is considered. Information on the stator-phase inductance of the electric
machine and its variation is used to determine the position of the movable part. For its estimation, probing
voltage pulses of known duration are applied to the phase. The amplitude of the current pulses caused by them
will be proportional to the phase inductance. A mathematical model of electromagnetic processes is used to
test the efficiency of the proposed control algorithm and determine appropriate control parameters. Since
stator phases have separate magnetic circuits and are not magnetically connected, the electromagnetic pro-
cesses in each phase are considered independently. Model parameters are determined experimentally using
an experimental prototype of the considered electric machine, for which the dependences of the phase flux
linkage and the generated force on the phase current for different positions of the movable part are obtained.
The results of the investigation of processes in the considered electric machine at different frequencies of the
movable part are given. It is found that, at frequencies of the movable part close to the nominal frequency, the
phase should be connected to the power supply even before the movable part reaches the extreme position.
Control using probing pulses applied to the operating phase is impossible, because the level of these pulses
does not reach the maximum value until the phase is switched on. In this case, it is necessary to use the prob-
ing pulses of another, nonoperating phase to determine the position of the movable part. Such an algorithm
makes it possible to control a linear reciprocating switched-reluctance electric machine at both low and high
frequencies of the movable part. The obtained results confirmed the correctness of the adopted approaches
to the development of a sensorless control algorithm.
Keywords: linear electric machine, switched-reluctance electric machine, mathematical model, sensorless
One of the most common types of autonomous
power sources is electric generators based on an inter-
nal-combustion engine (ICE). Analysis of the applica-
tions of autonomous power generating systems shows
that such generators are in demand as continuous and
high readiness mobile power sources. As such, they are
superior to turbine-based installations and installa-
tions using renewable energy. The most popular are
10- to 20-kW generators.
In most existing designs, the functions of the elec-
tric generator are performed by a rotating electric
machine (EM). The use of a linear reciprocating EM
as an electric generator makes it possible to not use a
crank mechanism and pass on to a free-piston ICE
without mechanical coupling between the cylinders.
In the free-piston ICE design, the movable part of
the linear EM is in the immediate vicinity of the cylin-
der-piston group. It is under significant alternating
forces, vibration, and high temperatures. In this case,
the placement of permanent magnets on the EM mov-
able part requires special cooling and mechanical
damage-prevention measures. Therefore, it is justifi-
able to use an inductor EM with no windings and per-
manent magnets on the movable part.
A feature of the linear EM operation as an electric
generator together with a free-piston ICE is the recip-
rocating motion (oscillations) of the movable part,
i.e., the absence of a steady operating mode (moving at
a constant speed). The normal operation of the system
requires precise control of the generated high-speed