METHOD FOR CONTROLLING AN ELECTRICAL DRIVE, AND ELECTRICAL DRIVE

Abstract

The invention relates to a self-learning repetitive method for an electrical drive or motor, in particular a linear or slewing drive, for determining the maximum speed during the movement of the actuator between a starting point (SP) and an end point (EP), wherein the actuator is accelerated to a speed v.sub.max over a first distance (x.sub.beschl), is braked over a second distance (x.sub.brems) and is then moved at a safe low speed (v.sub.safe) over a third distance (x.sub.safe) as far as the stop and is stopped. The method is repeated with the aim of minimizing the third distance (x.sub.Safe,min) and thereby achieving the maximum speed (BPmax, v.sub.max). The method also provides for taking into account the external interfering influences, for example external forces and friction. The invention also relates to such an electrical drive.

Claims

1. Method for controlling an electrical drive, comprising the steps of: moving an actuator in a forward movement between a starting point (SP) and an end point (EP) and in a return movement between the end point (EP) and the starting point (SP), accelerating the actuator in at least one of the forward movement and the return movement, to a speed v.sub.max over a first distance x.sub.beschl, braking over a second distance x.sub.brems and then moving at a lower speed v.sub.safe over a third distance x.sub.safe1 as far as a stop, characterized in that the actuator is moved, in at least one subsequent movement, at a low speed, or at the low speed v.sub.safe, over a distance x.sub.safe2 that is shorter than the distance x.sub.safe1, toward the stop, the acceleration phase and the braking phase becoming longer owing to the distance x.sub.safe2 that is becoming shorter, and the maximum speed v.sub.max to be achieved increasing owing to the longer acceleration phase.

2. Method according to claim 1, characterized in that in a starting phase, in particular during the first forward movement and/or the first return movement, the actuator is accelerated only to the low speed v.sub.safe.

3. Method according to claim 1, characterized in that in a teaching phase over several forward and return movements, the distances x.sub.safe1, x.sub.safe2 become shorter, until a minimum distance x.sub.safe-min is achieved.

4. Method according to claim 3, characterized in that at least one of the length of the minimum distance x.sub.safe-min and the maximum speed v.sub.max are specifiable.

5. Method according to claim 1, characterized in that the external interfering influences acting on the actuator are detected, the actuator being driven such that at least one of the interfering influences are taken into account and the drive is switched to an interference mode, if the interfering influences exceed a specified susceptibility to interference.

6. Method according to claim 5, characterized in that the interfering influences are detected by means of an acceleration monitoring process.

7. Method according to claim 5, characterized in that the susceptibility to interference can be adjusted.

8. Method according to claim 5, characterized in that, when at least one of the distance x.sub.safe is lengthened and the maximum speed v.sub.max is increased, at least one of the following occurs: the susceptibility to interference reduces, and when either of the distance x.sub.safe is shortened and the maximum speed v.sub.max is reduced, the susceptibility to interference is increased.

9. Method according to claim 1, characterized in that, at either of the starting point (SP) and end point (EP), the actuator strikes the stop with an increased force.

10. Electrical drive, comprising an actuator that can be moved in a forward movement between a starting point (SP) and an end point (EP), and in a return movement between the end point (EP) and the starting point (SP), comprising adjustable stop means, against which the actuator strikes at least one of a starting point (SP) and end point (EP), comprising an electrical motor for moving the actuator, comprising position measuring means for determining the position of the actuator, comprising a controller for controlling the motor depending on the signals from the position measuring means, characterized in that the controller is designed and equipped in such a way that the drive can be operated during operation.

11. Electrical drive according to claim 10, characterized in that at least one of the length-adjusting means for adjusting the length of the distance x.sub.safe and/or speed-adjusting means for adjusting the maximum speed v.sub.max are provided.

12. Electrical drive according to claim 10, characterized in that the influence-adjusting means for adjusting the susceptibility to interference, and influence-measuring means for determining the external interfering influences acting on the actuator are provided.

13. Electrical drive according to claim 11, characterized in that an adjustment means is provided for each forward movement and return movement, such that during each movement the susceptibility to interference is increased by at least one of lengthening the distance x.sub.safe and reducing the maximum speed v.sub.max, and in each case the susceptibility to interference is reduced by at least one of shortening the distance x.sub.safe and increasing the maximum speed v.sub.max.

14. Electrical drive according to claim 10, characterized in that the motor is a linear motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings:

[0032] FIG. 1 is a perspective view of a drive according to the invention;

[0033] FIG. 2 shows the drive according to FIG. 1 with the housing cut open;

[0034] FIGS. 3 and 4 show the movement path of the actuator over its speed in the starting phase;

[0035] FIGS. 5 and 6 show the movement path of the stop over its speed in the teaching phase; and

[0036] FIGS. 7 and 8 show the movement path of the actuator over its speed in two different operating phases.

DETAILED DESCRIPTION

[0037] FIGS. 1 and 2 show an electrical drive 10 in the form of a linear drive. The drive 10 comprises an actuator 12 in the form of an axial bar. The actuator 12 can be moved between two stops 14, although only one stop 14 is visible in FIGS. 1 and 2. The stop 14 is adjustably arranged in a housing 16 in the movement direction of the actuator 12. An additional stop is provided below the actuator 12, which stop is covered by the actuator 12 owing to the perspective of FIG. 2. This additional stop is also preferably adjustable, and so the actuator 12 can be moved in a forward movement and a return movement between a starting point, which is specified by a stop 14, and an end point, which is specified by an additional stop 14.

[0038] On its free end, the actuator 12 provides an adapter plate 18, to which components to be moved can be fastened. The actuator 12 is movably mounted in the housing 16 by a cross roller guide 20.

[0039] In order to move the actuator 12, a motor 22 is provided in the housing, which motor is in the form of a linear motor. As is clear in particular from FIG. 2, the motor comprises a stator 24 which is accommodated in the housing and comprises corresponding magnet windings. Permanent magnets 26 are provided on the underside of the actuator, which permanent magnets interact with the stator 24 and form the secondary part of the motor. By appropriately supplying current to the stator 24, the actuator 12 moves, which movement results in the forward movement and return movement between the starting point and the end point.

[0040] A controller 28 is also integrated in the housing 16, which controller processes the various input signals and controls the motor 22 accordingly. In order to supply current, an electrical connection 30 is provided.

[0041] The drive 10 additionally comprises position measuring means for determining the position of the actuator 12. The position measuring means are formed by the permanent magnets 26 provided on the actuator 12 and a magnetic field sensor provided on the housing 16, which magnetic field sensor detects alternating magnetic fields within its detection range and emits corresponding signals to the controller 28.

[0042] As can be seen in FIG. 1, the drive 10 has a control panel 32, on which various status notifications are indicated, namely: Ready, Power, Error and Status. Furthermore, two adjustment means 34 and 36 are provided which are formed as variable transformers. The adjustment means 34 or 36 respectively can be used to adjust the susceptibility to interference or speed of the actuator 12 in its forward movement and/or return movement.

[0043] The drive 10, and/or its controller 28, is designed such that, during operation, the drive functions as follows:

[0044] In total, the drive can be operated in three different phases: firstly in the starting phase; secondly in the teaching phase; and also in the operating phase.

[0045] When the drive is being started up, the drive is initially in the starting phase. For this purpose, in particular during the first forward movement between the starting point SP and the end point EP, and also during the first return movement between the end point EP and the starting point SP, the actuator is accelerated to a low speed v.sub.safe. During the first forward movement and return movement, the controller 28 does not know the position of the starting point SP and the end point EP, which can be displaced by the adjustable stops 14. In this case, the low speed v.sub.safe is selected such that the actuator 12 is moved toward and strikes the stops 14, without the actuator 12 or the stops being damaged. The position of the starting point SP and the end point EP can then be detected by the position measuring means after the first forward movement and return movement and can be recorded in the controller 28.

[0046] In FIG. 3, the forward movement of the actuator is entered in millimeters over the speed in millimeters/second. It can be seen that the actuator 12 starts at the starting point SP at the position 7 millimeters and is accelerated to a speed v.sub.safe of approximately 80 millimeters per second until it strikes the stop 14 at 45 millimeters at the end point EP and is braked to a speed of 0 millimeters per second.

[0047] FIG. 4 shows the first return movement, specifically from the endpoint EP 45 millimeters to the starting point SP 7 millimeters.

[0048] It is therefore clear from FIGS. 3 and 4 that the actuator 12 is moved substantially at a constant speed v.sub.safe over the entire first forward movement and the entire first return movement.

[0049] A teaching phase then follows the starting phase, which teaching phase is described in more detail in FIGS. 5 and 6. In the teaching phase, in the forward movement and the return movement over a first distance x.sub.beschl, the actuator is accelerated to a speed v.sub.max1 of approximately 270 mm/s, specifically up to a first braking point BP1 which, according to FIG. 5, is approximately 16 mm. A second distance x.sub.brems then follows the distance x.sub.beschl, within which second distance the actuator is braked from the speed it has in braking point BP1 to the low speed v.sub.safe. The distance x.sub.safe1 then follows the distance x.sub.brems, in which distance x.sub.safe1 the actuator 12 is moved at the low speed as far as the end stop EP, at which said actuator strikes the stop 14. The actuator is preferably accelerated to a maximum within the distance x.sub.beschl and is braked to a maximum within the distance x.sub.brems.

[0050] In order to reduce vibration damping when the actuator strikes the stops, it is advantageous for the controller 28 to control the motor 22 such that the actuator 12 strikes the stop at the starting point and the end point with an increased and in particular maximum force.

[0051] In subsequent forward and return movements, the braking point BP, as shown in FIG. 6, is displaced toward the end point EP or, in return movements, toward the starting point SP. Accompanying this is a greater maximum speed v.sub.max2 of approximately 400 mm/s and a shortening of the distance x.sub.safe. It is therefore clear from FIG. 6 that in a further forward movement, the actuator 12 is accelerated over the distance x.sub.beschl2 as far as the braking point BP2, and is then subsequently braked over the distance x.sub.brems2. From X=31 mm, the actuator 12 is then moved at the speed v.sub.safe as far as the end point, i.e. along the distance x.sub.safe2. Owing to the longer acceleration as far as the braking point BP2, the v.sub.max2 of 400 mm/sec is achieved, which results in a forward movement which is temporally shorter than the previous forward movement according to FIG. 5. Therefore, overall the actuator is moved between the starting point SP and end point EP within a shorter duration.

[0052] In another forward movement, the braking point is displaced further toward end point EP or the distance x.sub.safe is further shortened and the speed v.sub.max is further increased for a time until the distance x.sub.safe has reached a specifiable, minimum length x.sub.safe-min, as shown in FIG. 7.

[0053] In this state, as is shown in FIG. 7, the operating phase is then achieved; the actuator 12 moves at a maximum speed v.sub.max of approximately 570 mm/s in a maximally short time between the starting point SP and the end point EP. The actuator 12 is accelerated over a maximum distance x.sub.beschl-max as far as the braking point BP.sub.max. The distance x.sub.brems-max follows this, within which distance the actuator is limited to the speed v.sub.safe. The distance x.sub.safe-min is selected such that it is ensured that the actuator 12 strikes the stop 14 at the still-permitted speed v.sub.safe.

[0054] During operation, interfering influences are measured in particular by an acceleration sensor provided on the actuator 12, which interfering influences result from forces acting on the actuator 12. The interfering influences can occur as a result of different installation positions, moved masses, external forces or friction. If the interfering influences change only within a specified susceptibility to interference, these interfering influences are automatically corrected by the drive. In FIG. 7, a permitted level of susceptibility to interference is indicated by the two parallel lines 38, 40, within which level of susceptibility to interference an acceleration by the drive is permitted. Acceleration fluctuations within these two lines 38, 40, i.e. within the susceptibility to interference, are leveled out by the drive, so that it can be ensured that the distance x.sub.safe-min can be maintained, which in turn means that the actuator 12 strikes the stop 14 at the still-permitted speed v.sub.safe.

[0055] As mentioned at the outset, the susceptibility of the actuator 12 to interference in a forward movement or return movement can be adjusted by means of the two adjustment means 34 and 36. The change to the susceptibility to interference also means that, when the susceptibility to interference increases, the speed v.sub.max increases and the distance x.sub.safe reduces, and when the susceptibility to interference reduces, the speed v.sub.max reduces and the distance x.sub.safe is lengthened.

[0056] FIG. 8 shows an operating state, in which the susceptibility to interference in the forward movement is reduced by the adjustment means 34. The two interfering influence lines 38, 40 are shown here mutually spaced further apart, as a result of which greater acceleration or speed fluctuations within the distance x.sub.beschl are permitted. Accompanying this is a limited permitted speed v.sub.max=v.sub.begrenzt, and an enlarged distance x.sub.safe.

[0057] In the braking point BPa, the acceleration is therefore terminated and the actuator 12 is moved back to braking point BPb at a largely constant speed v.sub.begrenzt. Here, braking to the still-permitted speed v.sub.safe takes place.

[0058] As a result of greater acceleration or speed fluctuations being permitted, it is necessary for the distance x.sub.safe to be enlarged accordingly, in order to always ensure that the actuator 12 strikes the stop 14 in the end point at the still-permitted speed v.sub.safe.

[0059] The drive 10 shown in the drawings is therefore advantageous in that the operator does not have to take any further measures after starting up the drive. The drive 10 automatically goes into the starting phase, following this into the teaching phase, and then into the operating phase. Monitoring the acceleration of the actuator 12 always ensures that the actuator 12 is moved for a maximally short time between the starting point and the end point. For very rapid movements, the susceptibility to interference can be increased; for low acceleration deviations, the controller then switched into an interference mode when the susceptibility to interference is exceeded.

[0060] For example, it is conceivable in the interference mode for the actuator 12 to be braked into the still-permitted speed v.sub.safe or for the actuator to be stopped.

[0061] If the robustness of the drive 10 is to be increased, or if the susceptibility to interference is to be lowered, this can take place by means of the corresponding variable transformer 34, 36. Overall, the actuator is then not moved at such high speeds v.sub.max. However, it is ensured that in the event of greater acceleration deviations, the actuator is nevertheless reliably moved from the starting point to the end point.