UDC 621.382

CONTROL UNIT FOR A FOUR-PHASE STEPPING MOTOR

M. S. Sukhanov, V. S. Moskvin

(Submitted by the scientific seminar of the Faculty of Physics and Technology)

The article considers a control unit for stepping motors, distinguished from known ones by the simplicity of its structure.

The device is implemented on standard logic elements of the “Logika” series and can be used for four-phase stepping motors of various types. Illustrations 2, references 3.

In automation and telemechanics, discrete-action devices containing stepping motors are widespread. The need to ensure high reliability of the motor control unit determines the potential structure of its elements.

The control unit must meet the following requirements:

1 — conversion of a single-channel sequence of pulses into an \(m\)-phase system of voltages and connection of the corresponding phase windings of the SM with a minimum number of elements;

2 — operation over a wide frequency range, including zero frequency;

3 — provision of reversal of the rotation of the motor shaft without loss of information.

The choice of the elements and circuit of the SM control unit is determined by the convenience of matching the commutator and power amplifiers, and by the reliability and simplicity of the unit structure. In this connection, it is expedient to use standard logic elements [1] for constructing control units; these elements possess high reliability, noise immunity, and simplicity of adjustment and monitoring.

The control unit for a four-phase stepping motor with paired switching considered in this article is implemented on standard logic elements of the “Logika” series and differs from known ones [2] in its simplicity. The latter is achieved through the use in the unit of potential-pulse cells connected according to a pulse-coincidence circuit.

The logic circuit of the stepping-motor control unit is shown in Fig. 1.

The basis of the commutator consists of two symmetrical triggers (\(T_1\) and \(T_2\)) with separate control, which play the role of key elements. The commutator has two inputs—“forward” and “backward.” The direction of rotation is determined by the input to which the control pulses are applied.

From one of the input buses, the pulses enter the coincidence circuits \(I\), the second inputs of which are connected to the collector circuits of the triggers.

Depending on the presence of control potentials at the inputs of the potential-pulse cells D connected to the collectors of the triggers, the output pulses of the coincidence circuits are fed to the corresponding inputs of the triggers. The outputs of the triggers, through power amplifiers UM, control the switching of phase windings 1–4 of the ShD motor.

Fig. 1. Functional diagram of the stepper-motor control unit.

The timing diagram of the voltages on the motor phases is shown in Fig. 2. It follows from the diagram that the control unit under consideration implements a four-stroke pair-switching circuit with the winding-commutation sequence 12–23–34–41–12... The commutation system used makes it possible to obtain a simple circuit solution for the unit and to increase the reliability of motor operation in reversible mode. In this case, a greater torque is provided on the motor shaft than in circuits with single switching of windings [3].

Fig. 2. Timing diagram of voltages on the phases of a stepper motor.

The developed control unit can be used for various types of four-phase stepper motors having a pickup-frequency range of 0–2000 Hz, with the corresponding replacement of standard power amplifiers.

The control unit considered was built on standard logic elements of the “Logika” series and successfully passed tests together with stepper motors of types ShDR-5, ShDR-711, and ShDR-721.

LITERATURE

1. G. R. Grainer et al. Design of contactless logic circuits for automatic control. Moscow, Energiya Publishing House, 1969.

2. B. A. Ivobotenko et al. Unified electronic commutators. Moscow, Energiya Publishing House, 1968.

3. Discrete electric drive with stepper motors, ed. M. G. Chilikin. Moscow, Energiya Publishing House, 1971.