Method for rotor position detection for a revolving cylinder motor or a linear motor

(42) Date of commencement of the patent: 15.11.1998 (45) Date of issue: 26. 7.1999

<td>(56) Documents:</td><td>(73) Patent owner:</td>

<td>0E 3148007A1 US 4992710A US 5001405A EP 0500295A1</td><td>LST LASER &amp; JET TECHNOLOGY MANUFACTURING UN</td>

<td>US 5072166A</td><td>TRADING SOCIETY MBH A-1130 VIENNA (AT). (72) Inventor: GirraiLLINGER PETER ING. VIENNA (AT).</td>

FLO (54) PROCESS FOR RUNNING POSITION DETERMINATION FOR CIRCUIT ARRANGEMENT FOR CARRYING OUT THIS (57) Method for rotor position determination for a rotary or linear motor, eg a stepper motor, a synchronous motor od. Like., With at least two Ständerwicktungen (6, 60) and a rotor with pronounced poles, in which in a control process, the actual value of the rotor position, eg Runner rotation angle or runner displacement, determined with respect to a controlled setpoint value and the excitation current for reaching the setpoint position of the rotor is changed as a function of the inductance of the driven stator windings, wherein the exciting current of the driven stator windings (6, 60) a periodic measuring current is superimposed, which has a frequency greater than the running frequency of the motor and does not substantially affect the excitation of the stator winding, and the reactive voltage drop caused by the measuring current is measured at the stator winding and the inductance is determined therefrom, and circuit arrangement for carrying out the method.

A ROTARY OR LINEAR ENGINE AND METHOD

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The invention relates to a method for rotor position determination for a rotary or linear motor, for example a stepper motor, a synchronous motor od. Like., With at least in stator windings and a rotor with pronounced poles, in which in a control process, the actual value of the rotor position, eg Rotor rotation angle or rotor displacement, determined against a controlled setpoint and the exciting current to reach the setpoint position of the rotor is changed in dependence on the inductance of the driven stator windings.

Furthermore, the invention relates to a circuit arrangement for carrying out the method, wherein for driving the stator windings of the motor, these are connected to excitation current generators and in each case a control input of these exciter current generators for compensating the setpoint deviation of the rotor position are connected to the output of a respective control circuit, whose output voltage is determined by the inductance of the driven stator winding, wherein the stator windings are connected to the input of a respective measuring circuit and whose outputs are connected to the inputs of the control circuits.

Known methods of this type are particularly applicable where a rotor position determination of a motor can not be performed by a sensor arranged on the shaft, for example, or if the arrangement of such a sensor is to be avoided.

Will eg a stepper motor operated in the so-called full-step or half-step mode, so the rotor of the motor moves exactly the position corresponding to the drive pulses applied to its stator windings, even if this stepping motor is not controlled by a position control device. However, the prerequisite is that the motor is not overloaded by the mechanical load, ie that the drive pulses are so high in energy that the mechanical load of the motor can be overcome.

Stepper motors can be driven by driving their stator windings with sinusoidal current in the so-called microstep operation. Normally, such operated stepper motors can also without a control loop, ie without retiming and correction of the position approach a target position exactly. Is a stepper motor, however, variable or subjected to unknown loads, it is necessary to determine the current position of the runner and to correct if necessary, to achieve an exact positioning; essentially to provide a position control loop.

From IEEE Transactions on Industrial Electronics, Vol.36, No.4, 1989, a method for rotor position determination of stepping motors has become known, wherein the rise time of the exciting current is measured. Namely, the stator windings are driven by stepper motors with pronounced rotor poles with a voltage, so the rise time of the thereby forming exciter current depends on the refining position. Since the associated rise time is known for each rotor position, the current rotor position can be determined by comparing these known values ​​with the measurement result.

However, the comparison of the measured with the known rise times required in the realization of a complex circuit structure, and this comparison can not be replaced by an arithmetic operation, since the dependence of the excitation current rise time of the rotor position can not be described accurately enough by a mathematical function.

By WO 92/01331 a method and a circuit arrangement for sensorless rotation angle detection of a damperless, preferably permanently excited, powered by a power converter synchronous machine by measuring signals became known. In this case, voltage jumps generated by the feeding converter are used as measuring signals, and the determined measured data are fed to a computer which calculates the rotor position from the dependence of the stator reactance. To carry out the necessary measurements, a separate measuring module takes over the control of the machine control system, carries out the measurements and then passes the control back to the control device of the machine.

The determination of the rotor position by this method, however, is relatively complicated, whereby a corresponding circuit arrangement is very expensive. Thus, for example, two separate modules must be provided for controlled control and for carrying out the position measurement.

Furthermore, a possibility of detecting the position of the rotor of a long-stator motor was known from DE-A1-31 48 007. For this purpose, two sensor arrangements are used, the first of which serves to detect the current distribution distribution and with the second of which the Statorwicklungsströme necessary to drive the rotor are detected.

Here are two different in their operation sensor systems provide, which is already consuming in itself. Furthermore, such an arrangement involves a complex type of evaluation and thus a complicated circuit structure.

US Pat. No. 5,001,405 has disclosed a method for determining rotor position of a commutatorless DC motor. Each stator winding is charged with two voltage pulses,

AT 405 352 Β which voltage pulses have the same amplitudes but different signs. This sign difference strengthens the bias of the iron caused by the rotor-the permanent magnet or DC current-excited by one of the two pulses, weakened by the other. This results in different time courses of the currents following the voltage pulses, which difference is used to determine the position.

A disadvantage of this method is that only a relatively inaccurate estimation of the position can be made.

U.S. Patent No. 4,992,710 is a continuation application to U.S. Patent No. 5,001,405, which operates in the same manner but provides ways of optimizing the duration of the voltage pulses.

EP-A1-500 295 discloses a device for determining the rotor position of a commutatorless, switched rotary motor, which enables accurate switching of the exciting current between successive motor stator windings. For this purpose, a resonant circuit is provided, whose inductive element is formed by the motor winding and its resistance and capacitance by predeterminable components. Via a capacitive or inductive coupling, a signal of low energy at a much greater frequency than the highest occurring switching frequency is fed into the resonant circuit. Since the resistance and the capacitance have fixed values ​​relative to the winding inductance which changes as a function of the rotor position, the resonant frequency of the oscillating circuit also changes indirectly in proportion to the winding inductance. Due to the course of the resonant circuit voltage, the respective rotor position angle can be determined. If the difference between the resonant frequency and the excitation frequency reaches a minimum, a detector circuit determines the maximum amplitude of the resonant circuit and thus controls a motor control unit which effects the timely switching of the exciter voltage to the subsequent stator winding.

In this device, however, the deviation of the actual value position is not compensated by the setpoint position of the rotor, but achieved by the correct control of the motor windings only the most uniform rotation of the motor.

US Pat. No. 5,072,166 also relates to a switched DC reluctance motor in which the position of the rotor is determined indirectly via the motor phase inductance. An oscillator generates a signal with an inductance-dependent period of time, which is further processed by suitable circuits to achieve the correct switching times of the exciting current between the phase windings. In each case two opposite stator poles are each driven with one of the three impressed phase currents. In order to achieve the most uniform possible rotation, the phase windings are excited in succession as a function of the current, relative position of the rotor to the stator, this position being determined from the dependent on the inductance of the respective stator winding period of a generated by an oscillator square wave signal. The oscillator frequency is far above the exciter frequency of the stator windings. Again, no compensation of a setpoint deviation of the rotor is made, but provided only high smoothness of the engine.

The object of the invention is therefore to propose a method of the type mentioned above, which allows a precise rotor position determination to compensate for the actual value deviation in a simple manner and which can be realized by a simple Schaitungsaufbau.

According to the invention this is achieved in that the excitation current of the driven stator windings - in a conventional manner - a periodic measuring current is superimposed, which has a greater frequency than the running frequency of the motor and the excitation of the stator winding is not substantially affected, and that by the Measuring current caused reactive voltage drop measured on the stator winding and from the inductance is determined.

As a result, the rotor position can be adjusted to its desired value in a simple and accurate manner by the inductance determination.

In a further development of the invention can be provided that the measuring current is triangular.

As a result, the inductance of the driven winding can be determined by means of a simple calculation.

Another object of the invention is to provide a circuit arrangement of the type described above, in which the function of driving a motor and the function of determining the rotor position can be realized by a simple assembly.

According to the invention this is achieved in that a measuring current generator is provided, that the measuring circuit is formed from a voltage measuring circuit for measuring the generated by the measuring current reactive voltage drop across the stator windings, so that the inductance of the driven stator windings can be determined for each controlled setpoint position of the rotor.

This allows a simple and thus maintenance-friendly design of the circuit arrangement.

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In a preferred embodiment of the invention can be provided that the excitation current generators are composed of sinusoidal voltage generators and the measuring current generators are made of rectangular voltage generators, whose outputs are connected to the inputs of a superposition circuit, which of the sinusoidal voltage superimposes the rectangular voltage, that the output of the superposition circuit is connected to the input of an integrator, that the output of the integrator is connected to the input of a voltage / current converter, which is connected at its output to one of the stator windings of the motor and that the measuring circuit is formed by a differential amplifier, which is connected with its two inputs to the respective stator winding and with its output to the input of the respective control circuit.

The two voltage signals can be generated with high quality by simple circuitry; Thus, therefore, a precise driving of the stator windings and accurate measurement results is achieved.

In this context, it can be provided that the integration member is formed by an operational amplifier whose output is connected via a parallel circuit of a resistor and a capacitor with its inverting input and whose non-inverting input is connected to ground.

Such an integrating element works very accurately in all frequency ranges of the winding drive signal.

Furthermore, it can be provided that the differential amplifier is formed by an operational amplifier, whose inverting input is connected on the one hand via a first resistor to the output and on the other hand via a second resistor to the first winding end of the stator winding and the non-inverting input connected via a third resistor to ground and on the other hand via a fourth resistor to the second winding end of the stator winding is.

As a result, exactly that voltage which is actually applied to the stator winding coil, tapped and further processed.

Another feature of the invention may be that the voltage / current converter is formed by an operational amplifier whose inverting input is connected via a resistor to ground and on the other hand via the stator winding to its output and whose non-inverting input forms the input of the voltage / current converter ,

Such a voltage / current converter is well controllable and works reliably even at high measurement frequencies.

The inventive method for a rotary or linear motor, eg a stepper motor, a synchronous motor od. Like., With at least two stator windings 6, 60 and a rotor with salient poles, in which in a control process, the actual value of the rotor position, eg Rotor rotation angle or rotor displacement, determined against a controlled target value and the excitation current to reach the setpoint position of the rotor in response to the inductance of the driven stator windings 6, 60 is changed, will be described in more detail below.

If, for example, a stepper motor is controlled by a position control loop, then its current position must be determined in order to compare it with the setpoint position and to adjust the current position of the setpoint position according to the result of this comparison. For motors with pronounced rotor poles, the inductance of the stator windings depends on the position of the rotor so that it can be used as a measure of the actual position of the rotor.

Due to the effect of iron saturation, there is no linear relationship between the excitation current in the stator windings and the resulting flooding. Negative affects this non-linear relationship, for example then off, when is overcome to double the increased mechanical load of the motor of this with twice the exciting current excitation. The flooding will not double in this situation as the excitation current, but only moderately to increase too small a value, whereby the increased mechanical load, however, can not be overcome.

This nonlinearity is determined by the current dependence of the relative permeability of the iron cycle. Both the flooding and the inductance of a coil with iron core, however, are linearly dependent on the relative permeability. Thus, the non-linear dependence of the flooding of the current can be achieved by measuring the inductance and corresponding tracking of the excitation current.

Φ = k1'ur * i kl Constant of the iron circle ur relative permeability i Coil current

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Φ flooding

L = k2 * ur k2 Constant of the coil

L inductance of the coil

If the two material constants k1 and k2 are known, the actual flux can also be determined after measuring the inductance of the coil;

Φ = (k1 * L'i) / k2

By a control loop, the coil current can be changed so that the desired value of the flooding is always achieved and previously described Ansteuerungsproblerne be avoided.

Since the inductance of a stator winding in motors with pronounced poles is directly related to the position of the rotor, it is also possible to deduce the position of the rotor from the determined inductance of the stator winding.

The determination of the inductance is carried out according to the invention by observing the voltage at the stator winding when changing the current;

u = L * (di / dt)

Simplification of this formula is achieved when di / dt is constant and known for each measurement. This is achieved by a time-linear change of the current, ie with a triangular time course of the current. If the amplitude of such a measuring current and its frequency chosen so that it does not contribute to the drive of the motor, it can be superimposed on the excitation current necessary for driving the motor of the stator windings. This condition is then sufficiently fulfilled when the measuring current has, for example, a hundredfold greater frequency and a smaller amplitude by a factor of 100 than the exciter current.

It is important to comply with these conditions, as changes in the stator flux caused by the periodic measurement signal could lead to non-uniform movements which, for example, have a very disturbing effect on precise positioning tasks.

The determination of the inductance of the driven stator winding is carried out according to the inventive method thus characterized in that the excitation current of the driven stator windings, a periodic measuring current is superimposed, which has a greater frequency than the running frequency of the motor and the excitation of the stator winding is not substantially affected, and that the caused by the measuring current caused by reactive voltage drop across the stator winding and from the inductance is determined.

Since only one simple calculation step is necessary for this determination (see the above formula), this calculation can be carried out quickly and with the necessary accuracy even by simply constructed arithmetic units.

The circuit arrangement according to the invention, in the case of driving the stator windings 6, 60 the motor are connected to excitation current generators and in each case a control input of these excitation current generators are connected to the output of a respective control circuit for compensating the setpoint deviation of the rotor position, whose output voltage through the inductance of the driven stator winding 6, 60 is determined wherein the stator windings 6, 60 with the input of a respective measuring circuit 3, 30 are connected and whose outputs are connected to the inputs of the control circuits, will now be described with reference to a preferred embodiment shown in the drawing.

The circuit arrangement according to the invention operates according to the following principle; A measuring current generator is provided which generates the measuring signal superimposed on the exciting current. The measuring circuit is formed from a voltage measuring circuit 3, 30 for measuring the reactive voltage drop generated by the measuring current to the stator windings 6, 60, so that for each controlled setpoint position of the rotor, the inductance of the driven stator windings 6, 60 can be determined.

In the embodiment of the invention shown in the drawing, which is designed for two stator windings having stepper motors, the operating principle just described is realized. This, however, the invention is not limited in terms of the design of the motors, but the rotor position of any, marked rotor poles having motor, for example, a synchronous motor od. Like., According to be determined according to the invention.

The excitation current generators are composed of sinusoidal voltage generators, and the measuring current generators are constituted by square-wave voltage generators whose outputs are connected to the inputs of a superposition circuit, respectively, which transmits the rectangular voltage to the sinusoidal voltage

AT 405 352 B siege. The sine and square-wave voltage generator and the superposition circuit are formed by a digital signal processor 16. The output of the superposition circuit is connected via a digital / analog converter 160 or 161 to the input of an integrator 4 and 40, respectively.

This integrator 4 or 40 is formed by an operational amplifier 13 and 130, whose

Output is connected via a parallel connection of a resistor 15 or 150 and a capacitor 14 or 140 with its inverting input and whose non-inverting input is connected to ground.

By such an integrator 4 or 40 are sinusoidal or cosinusoidal voltages in their

Waveform not changed, but only out of phase. However, the superimposed square-wave voltage is transformed into a voltage with a triangular time characteristic.

The output of the integration member 4 and 40 is connected to the input of a voltage / current converter 2 and 20, whose output is connected to the stator winding 6 and 60 of the stepping motor.

The voltage / current converter 2 or 20 is formed by an operational amplifier 5 and 50, whose inverting input is connected via a resistor 7 or 70 to ground and on the other hand via the stator winding 6 and 60 with its output and its non-inverting input the input of the voltage / current transformer 2 or 20 forms.

This voltage / current converter 2 or 20 converts the control and measuring signals calculated and output by the signal processor 16 into the currents necessary for winding control.

The measuring circuit 3 or 30 is formed by a differential amplifier, which is connectable with its two inputs to the stator winding and with its output to the input of the control circuit. Also, the just-mentioned control circuit is formed by the signal processor 16, whereby it is necessary that the output of the differential amplifier via an analog / digital converter 170 or 171 is connectable to the input of the control circuit.

The differential amplifier is connected through an operational amplifier 12 and 120 formed, whose inverting input on the one hand via a first resistor. 9 or. 90 to the output and on the other hand via a second resistor 8 and 80 with the first coil end of the stator winding 6 or 60 is connected and whose non-inverting input on the one hand via a third resistor 11 and 110 to ground and on the other hand via a fourth resistor 10 and 100 is connected to the second winding end of the stator winding 6.

Since neither of the two terminals of the stator winding 6 or 60 is at a defined and known potential, it is not possible to tap only the potential of a winding terminal and to calculate the voltage applied to the stator winding 6 and 60, respectively. It must therefore, as shown in the drawing, be provided a differential amplifier whose output voltage is determined by the difference of the potentials of the two winding terminals.

By means of the switch 21 or 22, the input of the control circuit is selectively connected to the output of the measuring circuit 3 or 30 or to the output of the integration member 4 and 40, respectively. As a result, the voltage generated by the integration element 4 or 40 can be checked and, due to component tolerances, possibly resulting impurities in the stator winding drive voltage can be taken into account in the calculation of the inductance of the stator winding.