Motor Control Device And Corresponding Control Method

Abstract

The aim of the invention is to provide a speed control method for reducing current ripple and speed ripple at constant dynamics behavior while reducing the hardware required to a minimum. For this purpose, a control signal, especially a speed deviation (ev) is divided up into at least two signal portions (evhi and evlo). Every one of the at least two signal portions (evhi and evlo) is processed in a different manner. The low-order portion (evlo) can be smoothed by means of a low-pass filter (F). In an adder (Sum6) mounted downstream thereof the differently processed signal portions are then added up for further control.

Description

BRIEF DESCRIPTION OF THE DRAWING

The present invention is explained in more detail with reference to the appended drawings, in which:

FIG. 1 shows a speed control circuit corresponding to the prior art;

FIG. 2 shows a speed control circuit with filtering of the actual value of the speed corresponding to the prior art;

FIG. 3 shows a speed control circuit with division of the signal in accordance with the present invention; and

FIG. 4 is a block circuit diagram of a position control system according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The exemplary embodiments which are explained in more detail below constitute preferred embodiments of the present invention.

The speed control system according to the invention which is shown in FIG. 3 is composed essentially of the components which have already been presented in conjunction with FIG. 1. However, a nonlinear controller NR is connected upstream of the controller R described in said figure. In said controller NR the speed difference ev is divided into two portions, as is also possible in a similar way in the case of a binary number with the splitting into higher order bits and lower order bits. In the present case, the splitting is into a higher value portion evhi and a lower value portion evlo where evhi+evlo=ev.

It is clear here that the lower value portion evlo corresponds approximately to that signal level which is caused by the interference variable rx. With the higher value portion the procedure adopted is as in the prior art according to FIG. 1, while the lower value portion is, for example, a) previously filtered or b) fed only to the I element. This is possible since the interference variable rx is free of mean values. For the case a) a block circuit diagram is specified in FIG. 3.

The signal output of the adder Sum1 is split into two signal paths. A limiter B is arranged in one of the signal paths. Said limiter limits the signal amplitude corresponding to a desired saturation function, for example

$\mathrm{evlo}=\{\begin{array}{c}-Q\mathrm{for}\mathrm{ev}<-Q\\ \mathrm{ev}\mathrm{for}-Q\le \mathrm{ev}\le Q\\ Q\mathrm{for}Q<\mathrm{ev}\end{array}$

with a positive constant Q. The resulting signal evlo comprises only the lower value portions of the original signal ev. In an adder Sum5, the signal portion evlo is subtracted from the original signal ev, resulting in the higher value signal portion evhi. The higher value signal portion, which originates, for example, from a load change of the motor and thus corresponds to an actual change in the speed v, is fed in an unprocessed form to an adder Sum6. The lower value signal portions evlo are, on the other hand, filtered in a filter F before they are fed to the adder Sum6. The two signal portions are added again to form a common signal in the adder Sum6, and are fed to the controller R or its amplifier G1.

The limiter B ensures that the amplitude of the lower value portion evlo corresponds approximately to the signal portion which is brought about in the actual speed signal vist by the interference signal rx. For example the low pass filter TP from FIG. 2 can be used for the filter. In this case, the smoothing of the actual value of the speed or rotational speed is effective only for the signal portion for which it is actually also required. Alternatively or additionally, one or more band stops with an adjustable stop frequency can be implemented in the filter F, their stop frequency or frequencies being adjusted, for example, in such a way that it corresponds to an integral multiple of the frequency of marks on the signal transmitter whose signal transmitter wheel has a predetermined number of marks to be sampled. In fact the actual value of the speed vist often has considerable interference portions at such frequencies.

Basically, it is also possible for the signal of the speed difference ev to be divided into more than two portions and for the nonlinear control in these portions to be carried out individually. Furthermore, it is also possible, as has already been mentioned above, to use an acceleration sensor in parallel with the position sensor in order to suppress noise or interference portions. In addition the signal transmitter G can also permit oversampling.

The nonlinear control step can also be carried out between the signal transmitter evaluation A and the adder Sum1 for the actual speed signal visit instead of before the control process R. Although this alternative is less advantageous, it is appropriate in existing control circuits in which, for example, only the actual speed signal vist is accessible.

The control mechanism according to the invention can also be used for position control. Said control can be built up in a customary way without conversion into speed signals. However, alternatively it can also be implemented by utilizing the speed control system from FIG. 3. A corresponding block circuit diagram is represented in FIG. 4, the speed control circuit from FIG. 3 being indicated by the dashed rectangle GR. The actual position signal for the position control is fed to an adder Sum7 which subtracts this signal from a reference position value xref. The subsequent amplifier G5 converts the position difference signal into the speed reference value vref. In this context, a nonlinear controller of the type of the nonlinear controller NR from FIG. 3 can alternatively be connected between the output of the adder Sum7 and the input of the amplifier G5. As a result, the control circuit from FIG. 3 can be used both for controlling speed and for controlling position.

Claims

1-14. (canceled)

15-26. (canceled)

27. A motor control device, comprising: a control component adapted to provide a control signal;a signal dividing device adapted to divide an amplitude of the control signal into at least two signal portions, one of the control signal portions being a higher value signal portion and the other one of the control signal portions being a lower value signal portion;at least one signal processing device adapted to process each of the at least two control signal portions in different ways; andan adder device adapted to add together the differently processed control signal portions before further processing.

28. The motor control device of claim 1, wherein the at least one signal processing device includes a low pass filter which is connected in a signal path for the lower value signal portion.

29. The motor control device of claim 1, wherein the at least one signal processing device includes at least one band stop filter which is connected in a signal path for the lower value signal portion.

30. The motor control device of claim 1, further comprising a position sensor for sensing a movement of an adjustment element; and an acceleration sensor for sensing a movement of the adjustment element.

31. The motor control device of claim 1, further comprising a sampling device adapted to repeatedly sample a variable to be sensed within a time step so as to acquire a plurality of sampled values for the time step, said sampling device being adapted to supply an average of the sampled values acquired for the time step as an actual variable.

32. The motor control device of claim 1, wherein the control component includes a subtraction device for providing a differential signal by subtracting an actual variable from a reference variable, said signal dividing device being connected downstream of the subtraction device.

33. A method for controlling a motor, comprising the steps of: providing a control signal;dividing an amplitude of the control signal into at least two control signal portions, one of the control signal portions having a higher value signal portion and another one of the control signal portions having a lower value signal portion;processing each of the at least two control signal portions in different ways; andadding the differently processed control signal portions together before further processing.

34. The method of claim 33, further comprising the step of filtering the lower value signal portion with a low pass filter.

35. The method of claim 33, further comprising the step of filtering the lower value signal portion with at least one band stop filter.

36. The method of claim 33, further comprising the steps of sensing a position signal; providing the position signal as an actual variable; sensing an acceleration signal; and providing the acceleration signal as an actual variable.

37. The method of claim 33, further comprising the steps of repeatedly sampling a variable which is to be sensed within a time step so as to acquire a plurality of sampled values for the time step, and providing an average of the values acquired for the time step as an actual variable.

38. The method of claim 33, wherein the providing step includes the step of subtracting an actual variable from a reference variable to produce a differential signal, said differential signal representing the control signal that is divided into the at least two control signal portions.