GB2264785A

GB2264785A - Process and device for determining the weight of a movable object

Info

Publication number: GB2264785A
Application number: GB9303005A
Authority: GB
Inventors: Helmut Meyer; Johann Schunn
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1992-03-06
Filing date: 1993-02-15
Publication date: 1993-09-08
Anticipated expiration: 2013-02-15
Also published as: DE4207072A1; DE4207072C2; GB2264785B; FR2688306B1; FR2688306A1; GB9303005D0

Description

2264785 Process and device for determining the weight of a movable object

SPECIFICATION

The invention relates to a process and a device for determining the weight of a movable object.

To enable the torque of a drive to be rated in such a manner that an object is moved at a constant speed or by a constant increment, it is necessary for changes in the weight of the object to be known at all times.

Let the application be a pile-lifting apparatus which is disposed at the feeder or at the delivery of a sheet-fed printing press. Such a pilelifting apparatus is incrementally adjusted in height through the intermediary of a suitable driving apparatus, with the increment always being such that, at the feeder, the individual sheets can be transported in problem-free manner from the pile into the printing press by means of the suction head; similarly, the pile-lifting apparatus at the delivery must at all times be in such a position that the printed sheets are deposited accurately. In order to ensure a constant increment, the torque must be matched to the respective weight of the pile-lifting apparatus.

The object of the present invention is to measure the weight of a movable object, without this requiring additional measuring apparatuses.

The object of the invention is achieved in that a brushless directcurrent motor is provided for moving the object, in that the commutation sequence of the brushless direct- current motor is interrupted, in that a progression to a following commutation phase is initiated and in that the weight of the movable object is determined from the difference obtained between one of the motor variables with load and the specified motor variable without load.

Said process is particularly suitable if the movable object is a pilelifting apparatus at the feeder or at the delivery of a sheet-fed printing press. The continuous removal of sheets from the feeder pile and the continuous deposition of the sheets on the delivery pile result in constant changes in the weights of the pile-lifting apparatuses. In particular, as a result of non-stop feeding and delivery, the drive must respond to great differences in load torque.

According to an advantageous further development of the process according to the invention, it is provided that the weight of the movable object is determined from the angle difference of the rotor resulting with load and without load at constant current intensity. As an alternative embodiment, it is proposed that the current intensity required in order to obtain a specified angle difference between the rotor positions with and without load is used as a measure of the weight of the movable object. Either, therefore, the motor variable of "current intensity" is kept constant and the corresponding angle difference is viewed as a measure of the weight, or the current intensity is changed in such a manner that the motor variable of "angle difference with and without load" always has a constant value. In the latter case, a change in the current intensity is taken as a measure of the weight of the movable object.

An absolute-value angle sensor is advantageously used for the implementation of the process - particularly for measuring the angle position of the rotor. It is also easily possible, of course, to employ an incremental sensor, with it being necessary here, however, to distinguish between two cases:

If the angle difference is positive - this case arises if the lifting apparatus is operating in down mode then the angle position of the rotor obtained without load is select ed as the reference angle position or synchronization pulse for measuring the angle difference of the rotor with and without load. If, conversely, the angle difference is negative - this case arises when the lifting apparatus is operating in up mode - then a "111 signal before the angle position without load is used as the reference angle position for measuring the angle difference of the rotor with and without load. A counting apparatus counts the increments up to the end position of the rotor, and a computing apparatus subtracts said number from the known number of increments between two signals from the rotor-position sensor.

In a further embodiment of the device for the implementation of the process according to the invention, a 2-position current controller of fixed current hysteresis is provided. The frequency of the 2 position controller changes as a function of the rotor position, which, in turn, depends on the load torque. The weight of the movable object or of the object to be moved can likewise be determined from the change in the frequency of the current with and without load.

As an alternative possibility, the 2-position current controller is operated at a fixed frequency and the difference in ripple of the current resulting With and without load is used as a measure of the weight of the movable object.

A further advantageous embodiment of the device for the implementation of the process according to the invention provides that a control apparatus starts a time measurement upon the application of current to two phase windings of the brushless direct-current motor and that a measure of the weight of the movable body is derived from the time that elapses until the end position of the rotor under load is reached.

The invention is explained in greater detail with reference to the following figures, in which:

Fig. 1 shows a schematic representation of a pilelifting apparatus at the feeder or at the delivery of a sheetfed printing press; and Fig. 2 shows a flow diagram for an embodiment of the process according to the invention.

Fig. 1 shows a schematic representation of a lifting apparatus 2 at the feeder or at the delivery of a sheetfed printing press (not shown). The control apparatus 8 constantly positions the pile-lifting apparatus 2 and, ultimately, the top edge of the pile in such a manner that, in the region of the feeder, the individual sheets are gripped by a suction head (not shown) and are transported into the printing press5 or in such a manner that, in the region of the delivery, the printed sheets are deposited accurately.

The pile-lifting apparatus 2 moves the pile table 3. Said pile table 3 is, in the case of a non-stop feeder, a pallet- The pile of sheets 5 is positioned on said pile table 3. The up or down movement of the pilelifting apparatus 2 is effected by a motor. Provided as the motor 1 is a brushless directcurrent motor 1. Said brushless direct-current motor 1 moves the pile-lifting apparatus 2 up or down through the intermediary of a shaft 6 and chains 7. The motor 1 is controlled through the intermediary of a control apparatus 8 according to the signals from a rotor-position sensor 9.

Fig. 2 shows a flow diagram with which an embodiment of the process according to the invention can be implemented in simple manner.

The process starts in block 9 of the flow diagram. The case represented is that of an up movement of the pilelifting apparatus 2. Said up movement, which is performed in point 10 of the flow diagram, is interrupted at 11 after distance x has been covered. In up mode, a brake is actuated at rotational speed n = 0 in order to secure the position. At 13, the commutation phase of the motor 1 is determined from the data from the rotor-position sensor 9. Subsequently, at 14, the rotor is moved to a defined phase through suitable application of current to two phase windings of the motor 1. Without load, the rotor assumes an angle position that is situated in the centre of the energized angle segment. Depending on the load, the actual angle position of the rotor in the energized segment will deviate from the central position. This angle difference is determined at 15.

An absolute-value angle sensor is advantageously used for this measurement. Subsequently, at block 16 of the flow diagram, the measured angle difference is compared with stored characteristic curves. At 17, it is easily possible therefrom to determine the weight of the pile 4. It is, of course, also readily possible to compute the weight from the measured values. At 18, the brake is released, and the pile-lifting apparatus 2 carries out the following, incremental up movement according to point 10 in the flow diagram, with the torque of the motor 1 being matched to the load torque of the pilelifting apparatus 2.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

CLAIMS:

1. Process for determining the weight of a movable object, characterized in that a brushless direct-current motor is provided for moving the object; the commutation sequence of the brushless direct current motor is interrupted; a progression to a following commutation phase is initiated.and the weight of the movable object is determined from the difference obtained between one of the motor variables with load and the corresponding motor variable without load.

Process according to claim 1, characterized in that the movable object is a pile-lifting apparatus at the feeder or at the delivery of a sheet-fed printing press.

3.

Process according to claim 1 or 2, c h a r a c t e r i z e d i n t h a t the weight of the movable object is determined from the angle difference of the rotor resulting with load and without load at constant current intensity.

4. Process according to claim 1 or 2, c h a r a c t e r i z e d i n t h a t the current intensity required in order to obtain a specified angle difference between the rotor positions with and without load is used as a measure of the weight of the movable object.

Device for the implementation of the process according to claim 1, c h a r a c t e r i z e d i n t h a t an absolute-value angle sensor is provided for detecting the angle position of the rotor.

6. Device for implementing the process according to claim 1, characterized in that an incremental sensor is provided for detecting the respective angle difference, wherein, should the angle difference be positive, the angle position of the rotor obtained without load is selected as the refei7ence angle position for measuring the angle difference of the rotor with load and without load.

7. Device according to claim 5, characterized in that an incremental sensor is provided, wherein, should the angle difference be negative, the "1" signal before the angle position without load is used as the reference angle position for measuring the angle difference of the rotor with load and without load, with a counting apparatus counting the increments up to the actual rotor position and with a computing apparatus subtracting said number from the known number of increments between two signals from the rotor-position sensor.

8. Device for the implementation of the process according to claim 1, characterized in that a 2-position current controller of fixed current hysteresis is provided and - 9 the weight of the movable object is determined from the change in frequency of the current with load and without load.

9. Device for the implementation of the process according to claim 1, characterized in that a 2-position current controller is provided, said 2position current controller being operated at a fixed frequency and the difference in ripple of the current with and without load is used as a measure of the weight of the movable object.

10. Device for the implementation of the process according to claim 1, characterized in that a control apparatus starts a time measurement upon the application of current to two phase windings of the brushless direct-current motor and a measure of the weight of the movable body is derived from the time that elapses until the end position of the rotor with load is reached.

11. A process for determining the weight of a movable object, substantially as hereinbefore described with reference to the accompanying drawings.

12. A device for determining the weight of a movable object, substantially as hereinbefore described with reference to the accompanying drawings.