End effector with integrated backfeed protection device, process

Abstract

The invention relates to an end effector for arrangement on a handling device, the end effector comprising at least one effector element movable by means of an electric drive, a backfeed protection device integrated in the end effector for receiving and / or converting a backfeed voltage during the braking process of the electric drive, and a control device for controlling the backfeed protection device.

Description

[0001] The invention relates to an end effector and a method for operating an end effector.

[0002] In end effectors with electric drives, the drive acts as a generator during braking, with the rotor inducing an electrical voltage in the stator windings. This induced voltage can disrupt or destroy power and control electronics within the end effector. External energy sources, such as power supplies that power the end effector, can also enter a fault mode and shut down if the return voltage is too high. This leads to process problems and can also pose a safety risk.

[0003] The invention is therefore based on the objective of ensuring reliable operation of an end effector in conjunction with different energy sources, in particular power supplies.

[0004] The problem underlying the invention is solved by an end effector for arrangement on a handling device with the features of claim 1. The end effector comprises a base housing; at least one movable effector element, in particular movably mounted in or on the base housing; an electric drive, in particular arranged in or on the base housing, for driving the at least one effector element; a backfeed protection device integrated in the end effector, in particular arranged in the base housing, for receiving and / or converting a backfeed voltage during the braking process of the electric drive; and a control device, in particular arranged in or on the base housing, for controlling the backfeed protection device.

[0005] Accordingly, the energy stored in the electric drive during braking can be absorbed into the regenerative voltage and preferably converted into heat. Consequently, the power and control electronics of the end effector, as well as integrated or external energy sources, can be protected from excessive currents or voltages, particularly the regenerative voltage. This eliminates the need for a separate fuse on the customer's power supply.

[0006] The end effector can preferably be designed as a gripper, particularly a mechatronic one. Due to the limited size of the end effector, especially its housing, the end effector is preferably battery-free, i.e., without a battery. Therefore, storing braking energy is neither practical nor possible for a compact end effector.

[0007] The electric drive is preferably designed as an electric motor, in particular an internal rotor motor or an external rotor motor.

[0008] It is advantageous if the backfeed protection device has at least one load resistor, in particular two, three or four load resistors, for converting the backfeed voltage into heat. The braking energy is converted into heat energy in the at least one load resistor. The heat energy is preferably dissipated to the environment via the main housing.

[0009] It is further advantageous if the backfeed protection device includes a switch for activating and deactivating it. The switch is preferably designed as a field-effect transistor. In the deactivation state, no energy is converted into heat energy to drive the end effector. In the activation state, the braking energy introduced during the braking process is converted into heat energy, among other things. Therefore, the backfeed protection device can be used selectively when, for example, a backfeed voltage is coupled into the end effector. In the deactivation state, the power source, in particular the power supply, can regulate the appropriate voltage in the end effector independently.

[0010] The end effector preferably has an electrical interface for connection to an electrical power source to supply power to the electric drive. The electrical power source can be, for example, an external power supply unit.

[0011] The end effector preferably has a supply line which electrically connects the electrical interface to the electric drive.

[0012] A further advantageous design provides that the backfeed protection device is connected to a supply line that electrically connects the electrical interface and the electrical drive. It is advantageous if at least one load resistor is electrically connected in parallel to the supply line.

[0013] The power supply line can be configured separately from a first circuit board and / or a second circuit board. Alternatively, the power supply line can also be arranged on, attached to, and / or within a first circuit board and / or a second circuit board. It is advantageous if the power supply unit is located in the gripper and / or on the first circuit board and / or the second circuit board.

[0014] It is advantageous if the backfeed protection device is designed such that, in an activated state, the switch electrically connects the at least one load resistor to the supply line and / or, in a deactivated state, electrically disconnects the at least one load resistor from the supply line. Accordingly, current flows from the supply line to the backfeed protection device only when the switch is in the activated state.

[0015] Preferably, the end effector includes a voltage measuring device for detecting a first quantity that characterizes the actual voltage applied to the supply line, in particular the actual voltage itself. The voltage measuring device can measure the first quantity cyclically at discrete time intervals or continuously.

[0016] It is also advantageous if the backfeed protection device, in particular the at least one load resistor and / or the switch and / or a contact point for connecting the load resistor to the supply line, is arranged on a common first circuit board.

[0017] An advantageous further development provides that the control unit is configured to control the electric drive and to activate and deactivate the backfeed protection device. The control unit can include a microcontroller with firmware. The microcontroller can be implemented, in particular as an integrated circuit on a second circuit board. Accordingly, the control unit can selectively activate and deactivate the backfeed protection device depending on the conditions described above.

[0018] The control device is preferably arranged on a second circuit board that is separate from the first. The first circuit board generates significant heat and / or electromagnetic interference due to high currents, which can negatively affect the components on the second circuit board. This phenomenon can be reduced by separating the circuit boards. It is conceivable that the first and second circuit boards are spaced apart from each other. Alternatively, it is conceivable that the first and second circuit boards are formed by a single circuit board and / or comprise a single circuit board. In this case, the backfeed protection device, in particular the at least one load resistor and / or the switch, can be arranged on a single circuit board together with the control device, in particular with the microcontroller and / or power electronics components.

[0019] It is advantageous if the control device is configured to activate or deactivate the backfeed protection device depending on the actual voltage applied to the supply line and / or the operating state of the end effector, in particular a motor operating state and a generator operating state. Accordingly, the backfeed protection device can be selectively activated and deactivated by the control device.

[0020] It is further advantageous if the control device is configured to activate the backfeed protection device when the actual voltage applied to the supply line exceeds an activation threshold voltage, and particularly when the end effector is, preferably predominantly, in a generator-like operating state. Accordingly, operating ranges can be defined within the end effector in which the electrical components are not damaged.

[0021] It is also advantageous if the control device is configured to deactivate the backfeed protection device when the actual voltage applied to the supply line falls below a deactivation threshold voltage. This switches off the backfeed protection device, preventing conflicts with a power supply unit that also regulates the voltage. Furthermore, it is advantageous if the control device is configured to deactivate the backfeed protection device when, additionally or alternatively, the end effector is, preferably predominantly, in a motor operating state. This deactivates the backfeed protection device when no more backfeed voltages occur.

[0022] For the purposes of the invention, a "motor operating state" is understood to mean that the electric drive is used to drive the at least one effector element. In this state, the electric drive is supplied with electrical energy by means of an energy source, in particular a power supply unit, wherein the energy is directed from the energy source to the electric drive. For the purposes of the invention, a "generator operating state" is understood to mean that during a braking process, kinetic energy is converted into electrical energy by means of the electric drive, which is then fed back towards the energy source.

[0023] Preferably, the backfeed protection device includes a temperature-dependent protection circuit. The protection circuit is preferably designed such that it switches to an open state when a limit temperature is reached or exceeded. This can be achieved mechanically, by the protection circuit blowing a fuse, and / or via software, by interrupting the protection circuit so that no energy is supplied to the load resistor.

[0024] The problem underlying the invention is also solved by a method for operating an end effector with the features of claim 13. The method comprises the following steps: a) Detecting the actual voltage applied to a supply line of the end effector, b) if the actual voltage exceeds an activation threshold voltage, activation of a backfeed protection device integrated in the end effector, and / or c) if the actual voltage falls below a deactivation threshold voltage, deactivate the backfeed protection device integrated in the end effector.

[0025] The activation limit voltage ensures that the backfeed protection device only intervenes if there is actually an excessively high voltage in the system.

[0026] It is conceivable that the procedure is designed as a computer-implemented procedure.

[0027] Preferably, the procedure prior to step b) includes the following step: a1) Detection of an operating state of the end effector, in particular a generator operating state or a motor operating state.

[0028] It is advantageous if the backfeed protection device according to step b) is only activated when the actual voltage exceeds the activation limit voltage and also when the end effector is in a generator operating state.

[0029] In generator mode, the electric drive acts as a generator when driven by a load and feeds electrical energy back into the system. A controller cascade located in the end effector, particularly in the control unit, detects whether the electric drive is being used as a drive or as a generator. For the purposes of the invention, a "controller cascade" is understood to be an arrangement of several control loops connected in series. Each control loop in the controller cascade has its own controlled variable and its own controller.

[0030] It is further advantageous if the backfeed protection device according to step c) is only deactivated if the actual voltage falls below a deactivation limit voltage, and / or if the end effector is in a motor operating state.

[0031] An advantageous further development of the method involves filtering the measured actual voltage to determine its mean value, particularly using an Infinite Impulse Response (IIR) filter. Since an IIR filter considers both current and past values, it effectively filters out interference. Using an IIR filter allows for strong filtering to eliminate high-frequency noise and obtain a smooth, stabilized mean value of the actual voltage.

[0032] It is advantageous to determine the activation threshold voltage by adding an activation offset to the mean value. It is also advantageous to determine the deactivation threshold voltage by adding a deactivation offset to the mean value. In this case, these are relative deactivation thresholds and activation thresholds, respectively. This allows for better adaptation to variable operating conditions, as they are related to the current state of the system. Relative activation thresholds are independent of absolute values. This means that changes in the supply voltage or other global system parameters do not directly affect the thresholds. In systems with different configurations or adaptations, the use of a relative activation threshold can be more flexible.The threshold can adapt to different operating conditions or variants without the need to define specific absolute voltage limits.

[0033] The end effector, in particular the control unit and its firmware, is configurable. Activation and deactivation offsets, for example, can be passed as parameters. Configuring these offsets allows the sensitivity of the activation and deactivation thresholds to be adapted to the specific requirements of the system or application. This results in a high degree of flexibility in adapting to different operating conditions.

[0034] Alternatively, absolute activation and deactivation limit voltages can also be stored in the end effector.

[0035] The activation offset is preferably larger in magnitude than the deactivation offset. The activation cutoff voltage is preferably larger in magnitude than the deactivation cutoff voltage.

[0036] The following is an example of variable operating conditions for a backfeed protection device or a brake chopper: Average of the current voltage 25,1 V Activation offset 2,0 V Activation threshold voltage 27,1 V Deactivation offset 1,0 V Deactivation threshold voltage 26,1 V

[0037] It is also advantageous if an error is triggered and / or an error message is issued when, despite the backfeed protection device being activated, the actual voltage does not fall below the deactivation threshold voltage after a maximum active time. In this case, it can be assumed that the backfeed protection device is defective, for example, the protection circuit has switched to the open-circuit state. The active time begins when the backfeed protection device is activated, i.e., when the activation threshold voltage is exceeded, and ends when it is deactivated, i.e., when the deactivation threshold voltage of the backfeed protection device is reached.

[0038] The problem underlying the invention is also solved by a computer program with the features of claim 21. The computer program comprises instructions which, when executed by a computer, cause the computer to execute the method described above. Preferably, the computer program includes firmware executable on a microcontroller.

[0039] Further details and advantageous embodiments of the invention can be found in the following description, which further describes and explains exemplary embodiments of the invention.

[0040] They show: Fig. 1 a block diagram of an end effector connected to a power source; Fig. 2 a block diagram of a backfeed protection device; Fig. 3 Diagram of a voltage curve of an actual voltage, the mean value and the limiting voltages.

[0041] In Fig. Figure 1 shows an end effector 10, in particular a gripper, in a block diagram. The end effector 10 has a base housing (not shown). Within the base housing, the end effector has an electrical interface 12 for connection to an external power source 14. Furthermore, the end effector 10 has an electric drive 16 arranged within the base housing for driving at least one effector element 18. The electric drive 16 is electrically connected to the electrical interface 12 by means of a supply line 20.

[0042] The electric drive 16 is supplied with energy, in particular a motor voltage, preferably 24V, via the electrical interface 12 and the supply line 20 by means of the energy source 14. The end effector 10 has a control unit 22 for controlling the electric drive 16. The control unit 22 preferably has firmware.

[0043] The electric drive 16 can, for example, be designed as an external rotor motor. During braking of the end effector, in particular the effector element, the motor does not act as a drive but as a generator. In this process, a backfeed voltage is induced in the stator windings by means of the rotor, which can be harmful to the power and control electronics as well as the external energy source 14 and can lead to failures.

[0044] A voltage measuring device 24 is provided on the supply line 20 for recording an actual voltage 25.

[0045] The backfeed voltage can affect the external power source 14 via the supply line 20. Therefore, the end effector 10 has a backfeed protection device 30. The use of a backfeed protection device 30 prevents an overshoot of the supply voltage by ensuring that the braking energy is dissipated in a controlled manner. This protects the electronic components and the customer power supply from damage caused by excessive voltages or currents. If the supply voltage overshoots, the applied voltage exceeds defined operating parameters of connected electronic components, especially the power supply, which can lead to damage to the connected electronic components, particularly the power supply. Without a backfeed protection device 30, the end effector can no longer be operated reliably. The effect of an overshoot of the supply voltage is compounded when several end effectors are operated from one power supply.

[0046] The backfeed protection device 30 is arranged on a first circuit board 32, in particular a brake chopper board. The first circuit board 32 is preferably designed separately from a second circuit board 34, in particular a main board. The control device 22 and / or the voltage measuring device 24 are preferably arranged on the second circuit board 34. Furthermore, a separate third circuit board 36, in particular a connection board, may be provided, on which the electrical interface 12 is provided.

[0047] The backfeed protection device 30 comprises a switch 38 and at least one load resistor 40 for converting electrical energy into heat energy. The switch 38 is designed as a field-effect transistor. The switch 38 can be switched between an activation state and a deactivation state by means of the control device 32.

[0048] The backfeed protection device 30 connects to the supply line 20, with the load resistors 40 being electrically connected in parallel to the supply line 20 or the electric drive 16.

[0049] In the deactivation state, switch 38 is open, so no current flows through the load resistors 40. This corresponds to the operation of the motor as a drive. During heavy braking, the actual voltage 25 in the supply line 20 increases. The control unit 22 detects the regenerative operation of the electric drive 16 and the increase in the actual voltage 25 and closes switch 28. In the activation state, current flows to the load resistors 40, so that the braking energy introduced into the end effector during braking is converted into heat energy. For this purpose, the control unit 22 is connected to switch 38 by means of a switching line 42. The switching line 42 is preferably designed such that the control unit 22 and switch 38 are galvanically isolated. For galvanic isolation, a means 43 is provided, which can preferably be arranged on the third circuit board 36.

[0050] The control unit 22, in particular the firmware, receives according to Fig. 2. The voltage signal of the voltage measuring device 24 is measured against the actual voltage 25 applied to the supply line 20. Subsequently, the control device 22 determines, based on the actual voltage 25, whether the backfeed protection device 30 should be activated or deactivated. Depending on the conditions, the control device 22 sends a switching signal via the switching line 42 and thereby opens (deactivation state) or closes (activation state) the switch 38.

[0051] In the activated state, a current flows through the load resistors 40, converting the electrical energy into heat energy. Therefore, a significant temperature increase can occur on the first circuit board 32. To prevent an excessive amount of electrical energy from being converted into heat energy at the load resistors, an upstream temperature-dependent protection circuit 44 (overtemperature shutdown) is provided. The protection circuit 44 is preferably configured to interrupt the electrical connection between the supply line 20 and the load resistors 40 when a limit temperature is reached. Alternatively or additionally, the protection circuit 44 can also be voltage- and / or current-dependent and interrupt the electrical connection when a limit voltage and / or limit current is reached.

[0052] The control device 22 is preferably configured such that it first detects the actual voltage 25 applied to the supply line 20. Furthermore, the control device 22 determines whether the end effector 10 is in motor operation or in generator operation. Finally, the control device 22 determines an average value 46 of the actual voltage 25 by filtering the actual voltage 25 using an IIR filter.

[0053] Furthermore, the control device 22 determines an activation threshold voltage 48 and a deactivation threshold voltage 50. The activation threshold voltage 48 represents a permissible voltage level of the end effector 10. The threshold voltages 48 and 50 are determined by adding an activation offset 52 and a deactivation offset 54, respectively, to the average value 46. The deactivation offset 54 is selected such that the backfeed protection device 30 does not interfere with the voltage regulation of a power supply. The activation offset 52 can be, for example, 2 V and the deactivation offset 54 can be 1 V. With an average value 46 of 24 V, the activation threshold voltage 48 is 26 V and the deactivation threshold voltage 50 is 25 V.

[0054] If according to Fig.3. When the actual voltage 25 exceeds the activation limit voltage 48 and the end effector is in regenerative operation, the control unit 22 sends a switching signal to the switch 38 via the switching line 42, which then closes and activates the backfeed protection device 30. Consequently, the braking energy is converted into heat energy by means of the load resistors 40. The activation of the backfeed protection device 30 is in Fig. 3 is represented by the dashed areas. Therefore, it shows Fig. 3 a first activation phase with a first activation time t1 and a second activation phase with a second activation time t2.

[0055] If according to Fig.3 if the actual voltage 25 falls below the deactivation limit voltage 50 and / or the end effector is in motor operation, the control device 22 sends a switching signal again to the switch 38 via the switching line 42, which then opens and deactivates the backfeed protection device 30.

[0056] During braking, the backfeed protection device 30 may be activated and deactivated multiple times. The excess electrical energy is then dissipated in the form of pulses via the load resistors 40. The backfeed protection device 30 is preferably switched periodically so that the excess braking energy is periodically converted into heat energy by the load resistors 40.

[0057] Furthermore, the control unit 22 records the active time of the backfeed protection device 30. If, after a maximum active time of 1 s, in particular 500 ms, preferably 300 ms, the actual voltage has not reached or has fallen below the deactivation threshold voltage, an error is triggered and / or a fault message is issued. Therefore, it can be assumed that the backfeed protection device 30 is defective, e.g., the protection circuit 44 has burned out. In this case, a technician should acknowledge the fault and take appropriate action.

Claims

[1] End effector for arrangement on a handling device, the end effector comprising: - at least one effector element movable by means of an electric drive, - a backfeed protection device integrated in the end effector for receiving and / or converting a backfeed voltage during the braking process of the electric drive - a control device for controlling the backfeed protection device. [2] End effector according to claim 1, wherein the backfeed protection device has at least one load resistor for converting a backfeed voltage into heat. [3] End effector according to claim 1 or 2, wherein the backfeed protection device has a switch for activating and deactivating the backfeed protection device. [4] End effector according to one of the preceding claims, wherein the end effector has an electrical interface for connection to an electrical energy source for supplying energy to the electric drive, and wherein the backfeed protection device connects to a supply line electrically connecting the electrical interface and the electric drive. [5] End effector according to claims 2 to 4, wherein the backfeed protection device is designed such that in an activation state the switch electrically connects the at least one load resistor to the supply line and / or in a deactivation state electrically disconnects the at least one load resistor from the supply line. [6] End effector according to one of claims 4 or 5, wherein the end effector comprises a voltage measuring device for detecting a first quantity that characterizes an actual voltage applied to the supply line. [7] End effector according to one of the preceding claims, wherein the backfeed protection device, in particular the at least one load resistor and / or the switch, is arranged on a first circuit board. [8] End effector according to one of the preceding claims, wherein the control device is configured to control the electric drive and to activate and deactivate the backfeed protection device. [9] End effector according to one of the preceding claims, wherein the control device is arranged on a second circuit board. [10] End effector according to one of claims 4 to 9, wherein the control device is configured such that it activates or deactivates the backfeed protection device depending on an actual voltage applied to the supply line and / or an operating state of the end effector, in particular a motor operating state and a generator operating state. [11] End effector according to the previous claim, wherein the control device is configured to activate the backfeed protection device when an actual voltage applied to the supply line exceeds an activation limit voltage and in particular when the end effector is in a generator operating state, and / or to deactivate the backfeed protection device when an actual voltage applied to the supply line falls below a deactivation limit voltage and in particular when the end effector is in a motor operating state. [12] End effector according to one of the preceding claims, wherein the backfeed protection device has a temperature-dependent protection circuit which is designed such that it can switch to an interrupted state. [13] Method for operating an end effector comprising the following steps: a) Detecting the actual voltage applied to a supply line of the end effector, b) if the actual voltage exceeds an activation threshold voltage, activation of a backfeed protection device integrated in the end effector, and / or c) if the actual voltage falls below a deactivation threshold voltage, deactivate the backfeed protection device integrated in the end effector. [14] Method according to the preceding claim, wherein the method before step b) comprises the following step: a1) Detecting an operating state of the end effector, in particular a generator operating state or a motor operating state. [15] Method according to claim 13 or 14, wherein the backfeed protection device according to step b) is only activated if the actual voltage exceeds the activation limit voltage and if the end effector is in a generator operating state. [16] Method according to any one of claims 13 to 15, wherein the backfeed protection device according to step c) is only deactivated if the actual voltage falls below a deactivation threshold voltage, and / or if the end effector is in a motor operating state. [17] Method according to any one of claims 13 to 16, wherein the recorded actual voltage is filtered to determine an average value of the actual voltage, in particular by means of an Infinite Impulse Response Filter. [18] Method according to the preceding claim 17, wherein the activation threshold voltage is determined by adding an activation offset to the mean value. [19] Method according to claim 17 or 18, wherein the deactivation threshold voltage is determined by adding a deactivation offset to the mean value. [20] Method according to any one of claims 13 to 19, wherein an error is triggered and / or an error message is issued if, with the backfeed protection device activated, after a maximum active time the actual voltage does not fall below the deactivation limit voltage. [21] Computer program comprising instructions which, when executed by a computer, cause the computer to execute the method according to any one of claims 13 to 20, wherein the computer program in particular comprises firmware executable on a microcontroller.

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