Method and arrangement for actuating electromechanical transducers

Claims

I claim:

1. A method for controlling an electro-mechanical transducer incorporating at least a stationary part and a movable part, comprising the steps of:

obtaining at least two distinct sets of data specific to said transducer, each said set of data relating to a type of perturbation known to occur in operation of said transducer and being in machine-usable form;

determining in response to actual energization of said transducer at least one of elapsed time, linear position and angular position of the movable part to obtain a determined value; and

modifying the energization of said transducer according to a schedule responsive to representative data from said two sets of data and to the determined value to compensate for said known perturbations, thereby to improve the operation of said transducer.

2. The method for controlling a transducer according to claim 1, wherein the step of obtaining a first set of data comprises obtaining a representative datum from the first data set with an access signal to obtain a drive current corrective signal to compensate for a deviation in operation caused by an expected perturbation in response to an electromagnetic forcing parameter in a single repetitive portion of motion of said transducer.

3. The method for controlling a transducer according to claim 1, wherein

the obtaining step obtains via access signals the representative data from the respective first and at least second sets of data which sets relate to perturbations of motive force of the transducer which are respectively caused by at least two different ones of the following four types of influences:

a) electromagnetic influences,

b) reluctance influences,

c) permanent magnet influences, and

d) mechanical influences other than permanent magnet influences, which mechanical influences are dependent on at least one of speed and position.

4. The method for controlling a transducer according to claim 1, wherein

the obtaining step obtains the second set of data, which second set takes account of perturbations of motive force of the transducer caused by permanent magnet influences to produce a second corrective signal, and

the modifying step modifies the energization of the transducer on a time scale commensurate with the time scale of the perturbations caused by the permanent magnet influences.

5. The method for controlling a transducer according to claim 1, wherein

the obtaining step obtains one of the sets of data, which has values sufficiently closely spaced with respect to transducer position to compensate for deviations in operation caused by harmonics of a desired motive force.

6. The method for controlling a transducer according to claim 1, wherein

the first and second sets of data are obtained by a preliminary step of calculating the data based on the structure and material of the transducer.

7. The method for controlling a transducer according to claim 1, wherein

the first and second sets of data are obtained by a preliminary step of calculating the data based on measurements of parameters and of energization response characteristics of a model of the transducer.

8. The method for controlling a transducer according to claim 7, wherein

the preliminary step of calculating is based in part on measurement of the energization response characteristics with energization sufficient to achieve a desired motive force.

9. The method for controlling a transducer according to claim 1, wherein

the first and second data sets are obtained by a preliminary step of calculating the data based in part on the influences of a load coupled to the transducer.

10. The method for controlling a transducer according to claim 1, wherein

the step of obtaining at least two distinct sets of data includes the step of producing signals from one of the first and second data sets which signals are variable to match motive-force-related characteristic dependent on a non-linear property of the transducer, which property varies within a respective repetitive portion of motion of the transducer.

11. The method of controlling a transducer according to claim 10, wherein

the non-linear property is one of the group consisting of iron saturation and armature reactive effect, and

the step of producing signals includes the sub-step of switching among data sets corresponding respectively to members of group consisting of iron saturation and armature reactive effect to obtain the first set of data.

12. The method for controlling a transducer according to claim 11, wherein

the sub-step of switching among sets of data comprises switching among the sets of data dependent upon the operating state of the transducer.

13. The method for controlling a transducer according to claim 1, wherein the determining step includes initially measuring at least one of elapsed time, linear position and angular position of the movable part and thereafter calculating a value to obtain the determined value.

14. The method for controlling a transducer according to claim 13, wherein

the obtaining step obtains via access signals the representative data from the respective first and at least second sets of data which sets relate respectively to perturbations of motive force of the transducer which are respectively caused by at least two different ones of the following four types of influences:

a) electromagnetic influences,

b) reluctance influences,

c) permanent magnet influences, and

d) mechanical influences other than permanent magnet influences, which mechanical influences are dependent on at least one of speed and position.

15. The method for controlling a transducer according to claim 13, wherein

the obtaining step obtains one of the sets of data, which has values sufficiently closely spaced with respect to transducer position to compensate for deviations in operation caused by harmonics of a desired motive force.

16. The method for controlling a transducer according to claim 13, wherein

the first and second sets of data are obtained by a preliminary step of calculating the data based on the structure and material of the transducer.

17. The method for controlling a transducer according to claim 13, wherein

the first and second sets of data are obtained by a preliminary step of calculating the data based on measurements of parameters and of energization response characteristics of a model of the transducer.

18. The method for controlling a transducer according to claim 13, wherein

the step of obtaining at least two distinct sets of data includes the step of producing signals from one of the first and second sets of data which signals are variable to match a motive-force-related characteristic dependent on a non-linear property of the transducer, which property varies within a respective repetitive portion of motion of the transducer.

19. The method for controlling a transducer according to claim 18, wherein

the non-linear property is one of the group consisting of iron saturation and armature reactive effect, and

the step of producing signals includes the sub-step of switching among sets of data corresponding respectively to members of group consisting of iron saturation and armature reactive effect to obtain the first set of data.

20. The method for controlling a transducer according to claim 19, wherein

the sub-step of switching among sets of data comprises switching among the sets of data dependent upon the operating state of the transducer.

21. The method for controlling a transducer according to any one of claims 10, 11, 12, 18, 19 and 20, wherein

the step of producing signals, in appropriate ones of its sub-steps, includes providing arithmetic logic units to combine a selected datum with other relevant control values.

22. The method for controlling a transducer according to any one of claims 10, 11, 12, 18, 19 and 20, wherein

the step of producing signals, in appropriate ones of its sub-steps, includes providing phase-shifting units to modify a selected set of data.

23. A method for controlling an electro-mechanical transducer including at least a movable part, comprising the steps of:

providing signals for scheduling performance of the transducer, including the sub-steps of:

obtaining at least two distinct sets of data specific to said transducer, each said set of data relating to perturbations known to occur in the operation of said transducer and being in machine-usable form;

determining in response to actual energization of said transducer at least one of elapsed time, linear position and angular position of the movable part to obtain a determined value; and

modifying the energization of said transducer according to a schedule responsive to representative data from said two sets of data and to the determined value to compensate for said know perturbations, thereby to improve the operation of said transducer; and

the method further including

subjecting the modified energization of the transducer to a closed loop control for the transducer, the representative data from the first and second data sets and the determined value contributing to the closed loop control.

24. A method for controlling an electro-mechanical transducer including at least a movable part, comprising the steps of:

providing signals for scheduling performance of the transducer, including the sub-steps of:

obtaining at least two distinct sets of data specific to said transducer, each said set of data relating to perturbations known to occur in the operation of said transducer and being in machine-usable form;

determining in response to actual energization of said transducer at least one of elapsed time, linear position and angular position of the movable part to obtain a determined value; and

modifying the energization of said transducer according to a schedule including corrective signals responsive to representative data from said two sets of data and to the determined value to compensate for said known perturbations, thereby to improve the operation of said transducer;

the signals providing step further including

providing signals to access the representative data in the two sets of data; the method further including

feeding the corrective signals into a closed loop control for the transducer;

measuring the position and the speed of the transducer to provide status signals; and

applying the status signals to modify the corrective signals.

25. A method for controlling a mechanical-electrical transducer incorporating at least a movable part and an electrical output circuit, comprising the steps of:

obtaining at least two distinct sets of data specific to said transducer, each said set of data relating to a type of perturbation known to occur in the operation of said transducer and being in machine-usable form;

determining in response to actual movement of said transducer at least one of elapsed time, position of the movable part and transduced output of said transducer to obtain a determined value;

modifying the energization including movement of said transducer according to a schedule responsive to representative data from said two sets of data and to the determined value to compensate for said known perturbations, thereby to improve the output of the electrical output circuit of said transducer.

26. A method for controlling an electro-mechanical transducer incorporating at least a stationary part and a movable part, comprising the steps of:

obtaining at least two distinct sets of data specific to said transducer, each said set of data relating to a respective type of perturbation known to occur in operation of said transducer and being in machine-usable form;

determining in response to actual energization of said transducer at least one of elapsed time, current consumption of said transducer, voltage supply to said transducer, linear position and angular position of the movable part to obtain at least one determined value, and corresponding to the at least one determined value at least one access signal; and

modifying the energization of said transducer according to a schedule responsive to representative data from said two sets of data accessed in response to the at least one access signal to compensate for said known perturbations.

27. The method for controlling an electro-mechanical transducer according to claim 26, wherein

the step of obtaining data comprises obtaining a first ordered sequence of data by accessing one of the at least two data sets with the at least one access signal; and

the modifying step comprises applying the first ordered sequence of data to a voltage or current generating means via a corrective signal to compensate for a deviation of parameters of motion caused by a known perturbation in response to an electromagnetic forcing parameter in a single repetitive portion of motion of said transducer.

28. The method for controlling an electro-mechanical transducer according to claim 26, wherein

the step of obtaining data comprises obtaining a first ordered sequence of data by accessing one of the at least two data sets with the at least one access signal; and

the modifying step comprises applying the first ordered sequence of data to a voltage or current generating means via a corrective signal to compensate for a deviation of parameters of motion caused by a known perturbation in response to an electromagnetic forcing parameter.

29. The method for controlling an electro-mechanical transducer according to claim 26, comprising also mechanical components, wherein

the step of obtaining data comprises obtaining an ordered sequence of data by accessing one and at least another of the at least two data sets with the at least one access signal, the one and the at least another of the at least two data sets respectively relating to different known perturbations of the motion of the transducer, respectively produced by influences selected from the following types and combinations of the following types involving less than all of them:

a) electromagnetic influences,

b) reluctance influences,

c) permanent magnet influences, and

d) mechanical influences other than permanent magnet influences.

30. The method for controlling an electro-mechanical transducer according to claim 26, comprising also mechanical components, wherein

the step of obtaining data comprises obtaining an ordered sequence of data by accessing one and at least another of the at least two data sets with the at least one access signal, the one and the at least another of the at least two data sets respectively relating to different known perturbations of the motion of the transducer, respectively produced by influences selected from the following types and combinations of the following types involving less than all of them:

a) electromagnetic influences,

b) reluctance influences,

c) permanent magnet influences, and

d) mechanical influences other than permanent magnet influences,

which mechanical influences are dependent on at least one of speed and position of at least one of the movable part and the mechanical components.

31. The method for controlling an electro-mechanical transducer according to claim 26, wherein

at least one of the sets of data include ordered sequences of values of comprehensive range and yet sufficiently closely spaced with respect to transducer position to compensate for deviations in operation caused by harmonics of a desired motive force.

32. The method for controlling an electro-mechanical transducer according to claim 26, wherein

the obtaining step comprises obtaining an ordered sequence of data from at least one of the two distinct data sets, which ordered sequence of data is variable to match a motive-force-related characteristic of the transducer dependent on a non-linear property of the transducer.

33. The method for controlling an electro-mechanical transducer according to claim 32, wherein the non-linear property of the transducer varies within a respective repetitive portion of the motion of the transducer.

34. The method of controlling an electro-mechanical transducer according to claim 32, wherein the non-linear property of the transducer varies within a representative distance of travel of the transducer.

35. The method for controlling an electro-mechanical transducer according to claim 32, wherein the nonlinear property is one of the group of iron saturation and armature reactive effect, and the step of obtaining data includes the sub-step of switching among the at least two data sets, said data sets embodying iron saturation and armature reactive effect, to obtain the determined value.

36. The method for controlling an electromechanical transducer according to claim 26, wherein the transducer effects an energy conversion and wherein

the determining step includes initially measuring at least one of elapsed time, linear or angular position of the movable part and an energy conversion state of the transducer, and thereafter calculating from the measured item the determined value.

BACKGROUND OF THE INVENTION

The invention relates to a method for actuating electromechanical transducers for the purpose of generating a prescribed power characteristic or torque characteristic, in particular for reducing angle-dependent torque fluctuations in electric motors, in which time-dependent or position-dependent (travel-dependent or angle of rotation-dependent) data sets are stored in a function memory, which data sets are called up as a function of the travel or angle of rotation covered in operation or with timing control and are logically connected in an arithmetic switching unit to an input variable to form momentary values, and in which, as a function of the momentary values, voltages or currents with corresponding time-dependent or position-dependent curve shape are impressed into the electrical terminals of the transducer. In addition, an arrangement for carrying out such a process is a subject of the present invention.

An important property, for example of an electric motor, is its concentricity quality (or the uniform power characteristic of an electromechanical transducer). It influences both the accuracy and the stability of a drive system. In order to be able to suppress the disturbing torque pulsations in motors, it is first necessary to localize the cause. Four factors are essentially responsible for the torque fluctuations:

Already with a currentless armature, permanent-magnet torque fluctuations arise, triggered by the interaction of the permanently magnetic materials and the winding grooves or other ferromagnetic components, in motors with permanent-magnet excitation or in motors with iron parts having high residual induction. A rotation of the rotor leads to fluctuations of the overall energy of the magnetic circuit and thus to angle-dependent torques with alternating stable and unstable extreme values.

In contrast with this, the electromagnetic torque fluctuations arise from the interaction of the armature electric loading and the magnetic field. The electromagnetic fluctuations are a result of the special distribution of magnetic fields in the air gap, the winding arrangement and the armature electric loading curve shape as a function of the angle of the rotor.

An angle-dependent change in the motor inductance, as occurs for example with a non-uniform air gap, with partial iron saturation, with a non-uniform material distribution, with respect to the magnetic permeance, and other effects, leads in conjunction with the armature currents to reluctance torque fluctuations.

Torque pulsations in the motor can also have mechanical causes. The mechanical torque fluctuations, as they will be referred to below for the sake of simplicity, are triggered for example by unsymmetrical stresses of the motor shaft such as axle shifts at couplings, eccentric bearing seats etc. They can also result from the load coupled to the motor (or generally transducer).

As a rule, all four types of torque fluctuation referred to occur together in the electric motor but usually with a different order of magnitude of the individual components. There are cases in which individual components are negligible with respect to the others.

Efforts have already been made to improve the concentricity quality of electric motors by constructional measures.

The portion of the permanent-magnet torque fluctuations can be eliminated for example by using a non-iron-containing winding with an annular magnetic yoke (for example: bell-type armature motors). A considerable reduction is already achieved by placing the iron laminated core at an angle, for example by one slot pitch, and by a suitable design of the shape of the magnet and of the slot, tooth or poleshoe geometry. Drive motors which are designed for steady-state motor speeds are frequently equipped with an additional flyweight (for example, record players).

The electromagnetic pole sensitivity (pole cogging) can be favorably influenced for example by means of a selection of the winding design matched to the air gap field and the current curve and thus also by inclining the slot pitch.

The reluctance torque fluctuations can be considerably reduced, inter alia, by using rotationally symmetrically arranged low-retentivity and high-retentivity materials.

However, these known constructional measures for improving the concentricity quality or corresponding measures for achieving a uniform power characteristic of a general, electromechanical transducer (for example linear motor, loudspeaker or the like) come up against limits without achieving complete uniformity. Moreover, such constructional measures frequently make the design more expensive and involve additional tolerance problems or a worsening of the data of such electric motors or transducers.

A different possible way of improving the synchronism is the electrical compensation of the torque pulsations. In the simplest case, an automatic control device ensures improved synchronism, running up or positioning. Further, the demands made on the controller with respect to adaptive control parameters, rapidity and stability cannot always be satisfactorily fulfilled with this method. Therefore, it is suitable to relieve the controller of the oscillatory moments and to generate the current harmonics required for constant torque in accordance with a characteristic line which has been previously determined from the motor data.

A method frequently used with brushless DC motors is to vary the ratio of the switch-on and switch-off range of the square-wave actuation. By means of a corresponding selection of the switch-on range of the different phases, an improved synchronism characteristic is achieved.

A universal and even better matched actuation is obtained by superimposing defined current harmonics. The required summing current curves can deviate considerably from a sinusoidal or square-wave shape. In this way, without external intervention in the motor, the synchronism quality can be considerably improved in a purely electronic manner. The motor developer is now presented with the possibility of optimizing the drive according to other viewpoints (for example, a more favorable production method). However, the greater outlay, in terms of control and power electronics, required for this should not be overlooked. The most recent progress in microelectronics and power transistors makes it considerably easier today to realize such high-quality servodrive systems.

Previous work on the aforementioned subject area is restricted merely to the electronic compensation of the electromagnetic torque fluctuations. This is usually only sufficient for an electric drive if the generated useful torque is very much greater than the other angle-dependent interfering pulses. Generally, this requirement is not fulfilled. Instead, a drive is required here which supplies in an angle-independent manner a constant moment over the entire torque range, i.e. a simultaneous reduction of permanent-magnet torque fluctuations, electromagnetic torque fluctuations, reluctance torque fluctuations and mechanical torque fluctuations or a selection of the latter if one or more components are negligible.

In addition, it is already known from EP-A-180 083 to generate a defined angle-dependent torque by means of corresponding actuation with currents of a particular curve shape. However, with this known measure only reluctance torque fluctuations are reduced, and to be precise also not very extensively since the actuation curves used are symmetrically trapezoidal or sinusoidal with a flattened maximum range.

SUMMARY OF THE INVENTION

The present invention is based on the object of proposing a method and an arrangement for actuating electromechanical transducers for the purpose of generating a prescribed power or torque characteristic in which all the components, at least the most important and most strongly manifest ones affecting the power or torque characteristic and possibly other interfering variables in other directions also are taken into account in order to achieve in particular a good concentricity quality in electric motors, for which purpose it is not necessary to carry out any constructional measures on the motor.

This object is achieved with a method of the type mentioned at the beginning by a plurality of different data sets, determined from the power or torque characteristic of the transducer and possibly from a connected load and taking into account different influences, being stored in the function memory in particular in the form of tables, regulations, equations or functions, by these data sets being called up out of the function memory in a position-dependent manner (for example in the case of a self-controlled synchronous motor) or time-dependent manner (for example in the case of a step motor) and being logically connected in sets, divided up according to the influences, to in each case at least one input variable, and by these logical connection results obtained in this way being combined to form the position-dependent and time-dependent momentary values.

The method according to the invention and a corresponding arrangement have the advantage that a more simple design of the transducer with lower tolerance requirements is obtained and that in the event of the position-dependent power and torque fluctuations being reduced noise reductions are obtained in electric motors and special flywheels in the drives can be dispensed with.

Depending on the type of motor design, it is possible for the purpose of simplifying the actuation to take into account only a number of the influences on the power or torque characteristics. However, in an electromagnetic transducer preferably one of the influences a), c) or d) or at least two of the subsequent influences are taken into account:

a) electromagnetic influences,

b) reluctance influences,

c) permanent-magnet and mechanical influences,

d) mechanical influences (in the transducer and possibly also the connected load).

If, with the corresponding transducer design, one or more of the influences have only a small influence on the power or torque characteristic, these can then be ignored.

In order to be able to compensate interfering forces occuring in other directions than the useful force or the useful torque, in this respect in particular the radial and the axial interfering forces in rotation motors should be mentioned, this can be taken account of by impressing additional, special voltage or current components.

The data sets which take into account the power or torque characteristic of the transducer and possibly the load can be calculated either from the given design and material data or they are calculated indirectly from parameters and/or characteristic lines measured on a model. In the first case, neither a test bench not other measurements are required.

However, it is also possible to determine the data sets which take account of the power or torque characteristic of the transducer and possibly of the load, by measuring passes on a measuring and test bench for optimization for the purpose of achieving the randomly prescribed power or torque characteristic of a model. Although this solution requires a test bench, it permits individual fine adjustment independently of manufacturing and material tolerances, which is not possible by means of calculations. For this solution there are two processes, specifically the direct one (measurement, determining the data sets, operation of the transducer with the data sets) and the iterative process in which the steps of the direct process are followed by the renewed measurement, the correction of the data sets and the operation of the transducer with the corrected values, these subsequent steps being repeated as often as desired.

An expedient arrangement for carrying out the method according to the invention is characterized by a function memory having in each case one memory section per influence to be taken account of for storing the associated data set, an arithmetic switching unit for logically connecting data sets read out of the memory sections to in each case at least one input variable and for combining the logic connection results to form momentary values, a position or time generator assigned to the electromechanical transducer for controlling the position-dependent or time-dependent reading out of the data in the function memory and a power controller for impressing voltages or currents into the electrical terminals of the transducer in accordance with the momentary values.

If the transducer is a multi-phase transducer, for example a multi-phase electric motor, data sets can be stored for each of the individual phases and corresponding momentary values can be derived therefrom, in which case for each of the individual phases corresponding function memories, arithmetic switching units and power controllers or corresponding sections are provided or the latter are operated with time-division multiplexing. In such a case, asymmetries and other deviations between the individual phases of the transducer can be taken account of. However, a simpler solution consists in common data sets being stored for all the phases and either these data sets being read out with a phase shift for the individual phases and logically connected for the individual phases by means of the arithmetic switching units to form momentary values or common momentary values being derived from these common data sets and a phase shifting unit being provided which derives from the common momentary values the momentary values, shifted by the corresponding phase angles, for all the phases. This latter solution requires a smaller degree of outlay but cannot take into account asymmetries between the individual phases as is the case for the first solution.

Further advantageous embodiments of the invention can be found in the further subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below by means of exemplary embodiments and with reference to the enclosed drawings, in which:

FIG. 1 shows the equivalent circuit diagram of a permanent-magnet-excited synchronous motor;

FIG. 2 shows a flow diagram for determining the phase currents for the electric motor for the purpose of reduction of the electromagnetic torque fluctuations;

FIG. 3 shows an illustration of the induced voltage in a phase of a four-phase motor in standardized form;

FIG. 4 shows the circuit diagram of a device for the direct measurement of the static torque of a model motor;

FIG. 5 shows the circ