MACHINE TOOL AND METHOD FOR CONTROLLING A MACHINE TOOL

Description

[0001] The present invention relates to a machine tool with a fixed machine control and a rotating clamping device, wherein the machine control communicates with a clamping device control rotating with the clamping device via an intermediary coupling unit, wherein the coupling unit connects the machine control to the clamping device control in a contactless manner, wherein the clamping device control has a control unit for controlling drive means for actuating clamping means of the clamping device and at least two redundant microprocessors are assigned to the control unit, by means of which process data records received from the machine control via the control unit can be checked independently of one another and / or process data received from process sensors can be inserted independently of one another into process data records and transmitted to the machine control via the control unit,and a method for controlling such a machine tool.,

[0002] Such a machine tool is already known from EP 4 015 144 A1. Regarding the further prior art, reference should first be made to EP 3 620 248 A1. This document provides a coupling device for a machine tool, via which an inductively operated chuck can be electrically coupled in the simplest possible manner, independent of user-specific components of the machine tool, and monitoring of the function of the chuck and the clamping jaws attached to it is ensured.

[0003] This is achieved by arranging a programmable interface in such a way that an interface is assigned to the chuck, which can be controlled by a control unit of a machine control system via a coupler.

[0004] However, this results in the problem that it cannot be guaranteed that control signals, and especially that safety-critical signals such as a safe torque-off signal (STO signal), are correctly transmitted and received by the inductive coupler.

[0005] This stop function is the most common safety function, which prevents a drive from being supplied with energy that causes rotation or movement. The drive coasts to a stop without generating any torque. This stop function also prevents unintentional restart.

[0006] Although redundant testing is provided for in the state of the art, since the transmission path via the inductive coupler is the same for both redundantly provided controllers, there is an increased risk that if a data packet is lost at a first controller, the corresponding data packet will also be lost at the redundant second controller.

[0007] Furthermore, reference should be made to US 2006 / 176823 A1 as further prior art.

[0008] Against this background, the present invention is based on the object of creating a machine tool in which a coupling between the machine control and the clamping device is designed in such a way that the security of the data communication is improved compared to the prior art.

[0009] This is achieved by a machine tool according to the features of independent claim 1, as well as by a method for controlling such a machine tool according to the features of the independent claim 6. Useful embodiments of such a machine tool and of a corresponding method for controlling it can be found in the respective subsequent dependent claims.

[0010] According to the invention, a machine tool is provided with a stationary machine control and a rotating clamping device, wherein the machine control communicates with a clamping device control rotating with the clamping device via a coupling unit. This is characterized in that the coupling unit connects the machine control to the clamping device control in a contactless manner, wherein the clamping device control has a control unit for controlling drive means for actuating clamping means of the clamping device, and at least two redundant microprocessors are assigned to the control unit, by means of which process data records received from the machine control via the control unit can be independently checked and / or process data received from process sensors can be independently inserted into process data records and transmitted to the machine control via the control unit.

[0011] This creates a machine control system on the machine tool side and a clamping device control system on the clamping device side, which communicate with each other via the intermediate coupling unit. The drive means can be controlled by controllers that enable the clamping devices to advance towards each other. Due to this drive system when the clamping devices are positioned opposite each other, an even number of clamping devices clamp a workpiece from opposite sides. In the case of a clamping device with three clamping devices, no opposite sides are selected, but rather an offset of 120° is selected; with five clamping devices, 72°, and so on. This centers a workpiece between the clamping devices.

[0012] To ensure improved data security, process data records received by a control unit of the clamping device control system, which thus represent output signals from the machine control system, are evaluated by two identical microprocessors that are stored redundantly. The process data records to be received contain, among other things, an STO signal; however, all process data records contain a calculated signature and a consecutive identification number. If the microprocessors determine that the value of the STO signal specifies a safe operating mode, they transmit this to their assigned clamping device controller, thus preventing the clamping device from opening, and thus the drive devices or servomotors from operating, until the STO signal cancels the safe mode.Specifically, an STO signal value of 1 can specify a safe operating state, while an STO signal value of 0 can cancel a safe operating state. This allows for simple coding in a short overall message that can be transmitted using the simplest infrastructure.

[0013] If an invalid signature is received that contains an incorrect CRC code, Huffman code, an incorrect check digit, or something similar, this indicates a malfunction and communication is no longer secure. Therefore, the microprocessor will forward this information to the clamping device control unit, which will safely stop the machine. If the received signature does not match the expected sequential identification number, the same thing happens, as communication may be running in circles or even be disrupted altogether.

[0014] Due to the redundancy of the microprocessors, the reliability with which an error is detected and recognized as such can be increased. More than two microprocessors can be used, but operation with two microprocessors is always possible.

[0015] Even when process data sets are compiled and sent as input signals for the machine control system, the redundancy of the microprocessors is advantageous. Each safety-critical sensor, especially force sensors or clamping signal transmitters that indicate the clamping status of a zero-point clamping system, communicates with a microprocessor. Conversely, a microprocessor can communicate with several different sensors.

[0016] Within the framework of communication, the different signals from the microprocessors can be handled in such a way that either each microprocessor transmits its own signals to the control unit, which then creates a signal for the machine control system, or a circulating process data record is created and the microprocessors insert the signals they have processed there, thus supplementing the process data records.

[0017] With some advantage, the clamping device drive mechanisms can be servomotors controlled by servo controllers. The servomotors move the clamping devices on the clamping fixture toward a workpiece to be centered until the workpiece is held with a specified force, and then stop their advance. Friction brakes then ensure that the clamping device does not leave the position it has reached until an opening signal is given. Mechanical self-locking is also provided by the gearing.

[0018] In a first embodiment, at least one force sensor or clamping signal transmitter can be assigned to each of the clamping devices, so that each of them is data-connected to only one of the microprocessors. In this case, several microprocessors are used, as many as there are clamping devices. Since the use and coordination of numerous microprocessors is costly and complex, this embodiment is not preferred.

[0019] A preferred embodiment is one in which at least one force sensor or clamping signal generator is assigned to each clamping device, and the force sensors or clamping signal generators of multiple clamping devices are assigned to microprocessors, with the force sensors or clamping signal generators of opposing clamping devices being assigned to different microprocessors. This creates a connection such that the opposing pairs of clamping devices are each monitored by different microprocessors, so that each pair is monitored by two microprocessors. This means that in this embodiment, two microprocessors are always required, regardless of how many clamping devices are ultimately used.

[0020] In a further modification, at least one force sensor or clamping signal transmitter can be assigned to each clamping device, and the force sensors or clamping signal transmitters of multiple clamping devices can be assigned to microprocessors at the same time. The force sensors or clamping signal transmitters of clamping devices with opposing force components are assigned to different microprocessors. For example, if a chuck is provided with three clamping jaws, two of them can be monitored by one microprocessor, and the third by the other microprocessor.

[0021] Furthermore, it can be provided that position sensors are assigned to the clamping devices, which are data-linked to the control unit. These are not safety-relevant measured values, since a critical condition cannot be determined from the mere position of the clamping devices. Therefore, these measured values ​​are not transmitted to the microprocessors, but exclusively to the control unit of the clamping device control.

[0022] In a specific embodiment, the coupling device can establish an inductively coupled data connection between the machine control system and the clamping device control system. An inductive coupling is advantageous because it enables both power and signal coupling. However, according to the invention, it is also possible to provide a hydraulic coupling, for example, while the signal coupling can be inductive. A contactless coupling is necessary due to the fact that signal and power transmission from the stationary machine tool to the rotating clamping device must be established.

[0023] It is advantageous for the clamping device controller to communicate with the machine controller using the Ethernet protocol. This is a fast and robust protocol that can also be used wirelessly. For example, a PROFINET connection can be used, while bus systems such as CANBUS can also be used within the clamping device controller and / or the machine controller.

[0024] The invention described above is explained in more detail below using an exemplary embodiment.

[0025] It shows Figure 1 shows a schematic representation of a machine tool with a clamping device and a machine control, which is connected via a coupler to a clamping device control assigned to the clamping device, and Figure 2 shows a more detailed schematic representation of the machine tool with the details of the clamping device control and the machine control.

[0026] Figure 1shows a schematic representation of a clamping device 1 having two pairs of clamping elements 2, 3, by means of which a workpiece 4 is held at an offset of 90° each. A clamping device controller 20 of the clamping device 1 communicates via an inductive coupler 7 with a machine control 10 of the machine tool, which includes a control unit 11, a safety control unit 12, and a power supply 5. Control units 11 and 12, as well as a control unit 21 of the clamping device controller 20, can be designed, in particular, as a programmable logic controller (PLC).

[0027] While the control unit 11 outputs control signals to the clamping device controller 20, for example, based on a running program or user settings on an interface not shown here, the safety control unit 12 is primarily or exclusively available for the communication of safety-relevant signals. These include, in particular, the transmission of a force signal indicating the force with which the clamping devices 2, 3 grip a workpiece. To improve the reliability of the data transmission via the inductive coupler 7, the invention provides for redundant monitoring of the signals transmitted to the control unit 21 of the clamping device controller 20 using redundantly designed microprocessors 22, 23 in the clamping device controller 20. Transmission via the inductive coupler 7 represents a normal, simple communication channel and is initially not secured.The evaluation of the signals passing through the inductive coupler 7 by two independent microprocessors 22, 23 therefore helps to improve the security of the data transmission.

[0028] In addition to the rough classification of Figure 1 This situation is shown in greater detail in Figure 2, although some subordinate aspects have been omitted.

[0029] Using the example of two clamping devices 2, 3, it is shown that a workpiece 4 can be centered by these. For this purpose, the clamping devices 2, 3 can be moved using servo motors 26, 27, which is monitored using position sensors 32, 33. Control is carried out using a control unit 21 of the clamping device control 20 via a CAN bus. Servo controllers 29, 30 are data-connected to the control unit 21 via this bus. While the control specifications come from the machine control 10, specifically from a control unit 11, the direct control of the servo controllers 29, 30 and, via these, the control of the servo motors 26, 27 takes place within the clamping device control 20. The clamping device control 20 and the machine control 10 are, as already mentioned in Figure 1 shown, data connected via an inductive coupler 7.

[0030] Specifically, positioning commands are initially transmitted to a control unit 11 of the machine control system 10 based on appropriate programming. This, in turn, sends positioning commands via the inductive coupler 7 to the control unit 21 of the clamping device control system 20. The control unit 21 then causes, for example, the clamping devices 2, 3 to be closed, i.e., moved toward the workpiece 4. Corresponding control signals 28 are transmitted to the two servo controllers 29, 30, which in turn control the servo motors 26, 27 accordingly. The position sensors 32, 33 monitor the position of the respectively assigned clamping devices 2, 3 and report their positions back to the control unit 21.

[0031] At the same time, however, the force acting on the clamping devices 2, 3 is also recorded. For this purpose, each clamping device 2, 3 is assigned a force sensor 35, 36, which communicates with a microprocessor 22, 23 and transmits status signals 31 thereto. To achieve sufficient redundancy in data acquisition, a first force sensor 35 assigned to a first clamping device 2 communicates with a first microprocessor 22, while another force sensor 36, which is assigned to another clamping device 3, communicates with a second microprocessor 23. The microprocessors 22, 23 receive the force signals and enter them into a process data record, which is filled in a circulating process by the microprocessors 22, 23 and then transmitted by the control unit 21 to the machine control system 10. There, the safety control unit 12, in particular, receives and processes the signals from the force sensors.Should an error occur, particularly if a force decreases, the machine control system 10 can react and return the machine to a safe state. The two criteria that must always be met are that the clamping devices must not loosen and that the workpiece remains clamped with the specified clamping force.

[0032] For sufficient redundancy, it is sufficient if several microprocessors 22, 23 are involved in controlling each force equilibrium, so that even with a larger number of clamping devices 2, 3, more than two microprocessors 22, 23 do not necessarily have to be involved. However, this can still be implemented. Even with an odd number of clamping devices, one clamping device can be controlled by one microprocessor and the other two clamping devices by the other, since at least two microprocessors are involved in controlling the total force for each clamping device.

[0033] If a microprocessor 22, 23 detects an incorrect, in particular excessive, force on a force sensor 35, 36 during operation, or if another critical error occurs, namely an error in a signature or an identification number of a process data record, which are redundantly checked by the microprocessors 22, 23, the microprocessor 22, 23 reports this to the safety control unit 12 of the machine control 10, which controls the machine into a safe state, in particular by means of a stop signal with which the machine is stopped in order to avoid injuries or damage due to the rapidly rotating, but in the worst case scenario, loosened workpiece.

[0034] What is described above is a machine tool in which a coupling between machine and tool is designed in such a way that the security of data communication is improved compared to the state of the art. LIST OF REFERENCE SYMBOLS

[0035] 1 Clamping device 2 First clamping device 3 Additional clamping device 4 Workpiece 5 Power supply 6 Monitoring signal 7 Inductive coupler 10 Machine control 11 Control unit 12 Safety control unit 20 Clamping device control 21 Control unit 22 First microprocessor 23 Second microprocessor 24 First stop signal 25 Second stop signal 26 First servo motor 27 Additional servo motor 28 Control signal 29 First servo controller 30 Additional servo controller 31 Status signal 32 First displacement sensor 33 Additional displacement sensor 34 Displacement signal 35 First force sensor 36 Additional force sensor

Claims

1. Machine tool comprising a fixed machine controller (10) and a rotating clamping device (1), wherein the machine controller (10) communicates with a clamping device controller (20) rotating with the clamping device (1) with the interposition of a coupling unit (7), wherein the coupling unit (7) contactlessly data-links the machine controller (10) to the clamping device controller (20), wherein the clamping device controller (20) has a control unit (21) for controlling drive means for actuating clamping means (2, 3) of the clamping device (1), and at least two redundant microprocessors (22, 23) are assigned to the control unit (21), by means of which process data sets received from the machine controller (10) via the control unit (21) can be checked independently of one another and / or process data received from process sensors can be inserted independently of one another into process data sets and transmitted to the machine controller (10) via the control unit (21), characterized in that either at least one force sensor (35, 36) or clamping signal transmitter is assigned to each of the clamping means (2, 3) and they are each data-linked to only one of the microprocessors (22, 23), or the force sensors (35, 36) or clamping signal transmitters of multiple clamping means (2, 3) are assigned to the microprocessors (22, 23) and the force sensors (35, 36) or clamping signal transmitters of opposing clamping means (2, 3) are assigned to different microprocessors (22, 23).

2. Machine tool according to claim 1, characterized in that the drive means of the clamping means (2, 3) are servo motors (26, 27) which are controlled by means of servo controllers (29, 30).

3. Machine tool according to any of claims 1 or 2, characterized in that at least one force sensor (35, 36) or clamping signal transmitter is assigned to each of the clamping means (2, 3), and the force sensors (35, 36) or clamping signal transmitters of multiple clamping means (2, 3) are assigned to microprocessors (22, 23), wherein the force sensors (35, 36) or clamping signal transmitters of clamping means (2, 3) with opposing force components are assigned to different microprocessors (22, 23).

4. Machine tool according to any of the preceding claims, characterized in that the clamping means (2, 3) are assigned displacement sensors (32, 33) which are data-linked to the control unit (21).

5. Machine tool according to any of the preceding claims, characterized in that an inductively coupled data link between the machine controller (10) and the clamping device controller (20) is established by the coupling device (7).

6. Method for controlling a machine tool comprising a fixed machine controller (10) and a rotating clamping device (1), wherein the machine controller (10) communicates with a clamping device controller (20) rotating with the clamping device (1) with the interposition of a coupling unit (7), wherein the coupling unit (7) contactlessly data-links the machine controller (10) to the clamping device controller (20), and the clamping device controller (20) has a control unit (21) for controlling drive means for actuating clamping means (2, 3) of the clamping device (1), and process data sets sent from the machine controller (10) to the clamping device controller (20) are independently checked by two redundant microprocessors (22, 23) and / or the microprocessors (22, 23) insert process data received from process sensors independently of one another into process data sets and transmit them to the machine controller (10) via the control unit (21), characterized in that either at least one force sensor (35, 36) or clamping signal transmitter is assigned to each of the clamping means (2, 3), and process data sets sent by these are each checked by only one of the microprocessors (22, 23), or the force sensors (35, 36) or clamping signal transmitters of multiple clamping means (2, 3) are assigned to the microprocessors (22, 23), and the force sensors (35, 36) or clamping signal transmitters of opposing clamping means (2, 3) are assigned to different microprocessors (22, 23) for checking the sent process data sets.

7. Method according to claim 6, characterized in that process data sets have a calculated signature and / or a consecutive identification number.

8. Method according to any of claims 6 or 7, characterized in that process data sets output by the machine controller (10) comprise an STO signal (Safe Torque Off signal) for each drive means, wherein a movement of the relevant drive means is enabled only if the signal corresponds to an enabling signal.

9. Method according to any of claims 7 or 8, characterized in that the microprocessors (22, 23) independently output a stop signal to the clamping means (2, 3) in the event of receipt of an STO signal or in the event of an error in a signature or a deviation from an expected identification number.

10. Method according to any of claims 6 to 9, characterized in that sensor data from force sensors (35, 36) or clamping signal transmitters are transmitted to the microprocessors (22, 23) and these are inserted into process data sets for sending to the machine controller (10).

11. Method according to claim 10, characterized in that each microprocessor (22, 23) creates its own process data sets and transmits them to the machine controller (10) via the control unit (21).

12. Method according to claim 10, characterized in that each microprocessor (22, 23) enters the process data received by it into a circulating process data set and the control unit (21) transmits the circulating process data set to the machine controller (10).