DE102006020966A1 - Synchronous or stepping motors blocking condition detecting method for use in control drive of motor vehicle, involves regulating controlled intensity of current by variation of control time based on constant average value - Google Patents

Abstract

The method involves producing a pulse-width-modulated voltage in addition to a stepping motor by a microcontroller, and controlling the stepping motor with the pulse-width-modulated voltage. Current consumption of the stepping motor is monitored. The controlled intensity of current is regulated by variation of the control time based on a constant average value. Communication time is detected and a blocking condition is detected from falling of the communication time below a threshold value. An independent claim is also included for a device for execution of a method of detecting a blocking condition in synchronous or stepping motors.

Description

The The invention relates to a method and a device for detection a lock state in a synchronous or stepping motor, the is driven with a pulse width modulated voltage, and its Current consumption monitored becomes.

In known methods for blocking detection, as used for example in the DE 196 12 596 A1 and the DE 196 12 597 A1 are described, electrical variables are used to detect a blocking state. The DE 196 12 597 A1 proposes for this purpose the evaluation of the voltage induced in a currentless winding of a stepping motor; the DE 196 12 596 A1 evaluates three parameters for blocking detection, namely the motor current, the current operating voltage and the resistance of the motor winding.

task The invention was an alternative advantageous and easy to implement Method for blocking detection in a synchronous or stepper motor to develop.

These Task is inventively characterized solved, that the Ansteuerstromstärke by varying the drive time to a constant average is regulated and that the Umkommutierungszeit detected and from the fall of commutation time below a threshold a blocking condition is detected.

When an application example of the invention is an actuator with a Stepper motor listed. For actuators, as used for example in motor vehicles It is necessary that the the engine driving device at any time the position of the actuator knows. You can do this Position sensors may be provided, but quite expensive are. In general, it is sufficient for position control, the Number of steps performed by a stepper motor based on a reference position, to be counted. The reference position can be specified by an end stop, against which the stepper motor is driven to Einjustierung. Of the this occurring blocking state must by the drive device be recognized. About that addition, the Control device, of course also blocking conditions recognize that are caused by an error, for example in a trapping case.

stepper motors become common with quasi-stationary Stream operated, z. B. in full-step mode with +1 and -1. This Current is adjusted by a pulse width modulation. One yourself rotating rotor generates a reverse voltage in the stator winding, counteracts the applied driving voltage. To the nominal current must therefore reach over the Pulse width, the stator voltage can be increased. By determination the Umkommutierungszeit from the pulse width modulated voltage can be detected whether the engine is rotating at a predetermined frequency or if he stands. Size Umkommutierungszeiten mean a turn, small Umkommutierungszeiten mean a standing of the engine.

There thus the Umkommutierungszeit smaller in a blocking state is as a rotation of the motor, can be a limit for the Umkommutierungszeit below that of a stall condition that has occurred can be closed.

in the The invention will be explained in more detail with reference to the drawing. It demonstrate

1 a schematically illustrated measuring structure,

2 an equivalent circuit diagram of a permanent-magnet-excited synchronous or stepper motor,

3 the current and voltage curve in the full-step mode of a stepper motor.

to Application comes the proposed method here at a motor control, in which the current is not through a microprocessor but through an external motor driver is regulated. This is especially in Multi-motor systems of use, since analog-to-digital converters and the required computing time for several Current regulator only in very powerful and thus expensive microprocessors whereas time attendance entries are due to the additional Use of multiplexers are usually available in sufficient numbers.

The 1 shows a schematic diagram of the components required for the proposed method. A microcontroller provides a current setpoint via an interface of an external drive device. The drive device regulates the motor current by means of a pulse width modulated voltage. By evaluating an output signal of the control device, the microcontroller detects the time duration of the respective re-commutation phase. The timing can be done advantageously by a capture input of the microcontroller. In each case, the instantaneous value of a running digital counter is stored for given values of the output signal. From two detected values of the rising or falling edge during commutation, the commutation time can thus be determined. If the microcontroller detects a commutation time which is below a predetermined limit value, the microcontroller recognizes a stationary motor, in particular in a blocking position, from this.

The Reprecipitation times of the motor in full-step mode are measured. When the engine is stopped, these times are shorter than when driving because the complete supply voltage is available for the current build-up. When the motor is running, however, the induced in the stator winding acts Counter voltage of the supply voltage against and the current build-up slower.

With The proposed method makes it possible to overload of the engine or the achievement of an end stop. With the ride against a known stop, the rotor position be matched.

The 3 illustrates the current and voltage curve in a synchronous or stepper motor. In order to operate the motor with a magnitude constant current + I ^ or -I ^, a pulse width modulated voltage Ü is applied to the stator winding of the motor, wherein the current in each case the sign changes in a commutation phase. Plotted is the voltage applied to a motor terminal clocked voltage Ü to ground. During the commutation phase, to achieve a fast current reversal, a long voltage pulse with ground potential or, as in the commutation phase [t1, t2], with maximum potential at the motor terminal is.

As will be shown below, the duration of the commutation phase depends essentially on the engine speed. In turn, the commutation period [t ₁ , t ₂ ] is considered.

The 2 shows a simplified, reduced to a phase equivalent circuit diagram for a real naturally multi-phase running permanent magnet synchronous motor or stepper motor. It can be seen that the applied voltage U is distributed to an ohmic voltage drop R · i, an inductive voltage component L · di / dt and to a countervoltage ω · Ψ induced in the stator winding. The corresponding voltage equation is therefore U = R * i + L di dt + ω · Ψ

wobei, wie die 3 zeigt, die Spannung U während des Kommutierungszeitraums [t₁, t₂] als konstant vorausgesetzt werden kann.For a current jump from I1 to I2 it follows generally

being like that 3 shows that the voltage U during the commutation period [t ₁ , t ₂ ] can be assumed to be constant.

When the motor is driven with a constant current, ie I1 = -I ^ and I2 = I ^, this leads to the solution approach for determining the commutation duration

welches die allgemeine Gleichung für einen Stromsprung von –I ^ auf +I ^ ist. Für einen stehenden Motor wird die induzierte Gegenspannung zu Null, daher gilt speziell ω·Ψ = 0und damit folgt für die Umkommutierungszeit eines stehenden Motors

The solution of this integral equation gives for the commutation time

which is the general equation for a current jump from -I ^ to + I ^. For a stationary motor, the induced reverse voltage will be zero, so special ω · Ψ = 0 and thus follows for Umkommutierungszeit a stationary engine

By comparing the clip terms of Eq. 1 and Eq. 2 it can be seen that the Umkommutierungszeit T _{F of} a running engine is always greater than the Umkommutierungszeit T _{S of} a stationary engine. Based on the difference between T _F and T _S can be distinguished between a rotating and a stationary engine.

Claims (6)

A method for detecting a blocking state in a synchronous or stepping motor, which is driven by a pulse width modulated voltage, and whose current consumption is monitored, characterized in that the driving current is controlled by varying the driving time to a constant average and that the Umkommutierungszeit is detected and off the lowering of Umkommutierungszeit below a limit, a blocking state is detected. Device by performing a method according to Claim 1, characterized in that this in addition to the stepper motor at least one microcontroller and a drive device for Generation of a pulse width modulated voltage has. Device according to claim 2, characterized in that that the Microcontroller for specifying a current setpoint with one input the drive device is connected, and that an output signal of the drive device an input of the microcontroller is supplied. Device according to claim 3, characterized in that that the Input of the microcontroller is a time measurement input and that the microcontroller from the course of the output signal of the drive device the Umkommutierungszeit or a relative change of Umkommutierungszeit determined by the engine. Device according to claim 2, characterized in that that the Stepper motor is part of an actuator. Device according to claim 5, characterized in that that by the blockage detection reaching the end stops of the Actuator is detected.