Method for controlling at least one servo motor, associated control device, robot and computer program product

Abstract

The invention relates to a method for controlling at least one servo motor (M, M1-M6) by means of a converter (1), comprising the following steps: monitoring the current flow in a circuit of a DC voltage intermediate circuit (4) connected to an input circuit (3); when a stop signal occurs, switching off a first switching device (21, 21a) to terminate the power supply from a power grid (2) to the DC voltage intermediate circuit (4); if it is determined by monitoring that no current flows after switching off the first switching device (21, 21a), braking the servo motor (M, M1-M6) by controlling a power semiconductor switch (S1-S6) of an inverter circuit (7) to reduce the rotation speed of the servo motor (M, M1-M6); if it is determined by monitoring that current flows after switching off the first switching device (21, 21a), switching off a second switching device (22, 22a) to stop feeding electrical energy from the DC voltage intermediate circuit (4) to the servo motor (M, M1-M6). The invention also relates to a related control device (27), a robot (8) and a computer program product.

Description

Technical Field

[0001] The invention relates to a method for controlling at least one servomotor by means of a converter, and also to a related control device, a robot and a computer program product. Background Art

[0002] Patent document EP2224586A1 discloses a method for controlling a motor-driven industrial robot, the industrial robot comprising at least one drive motor, the drive motor being fed by a power supply circuit connectable to a power supply voltage, the power supply circuit comprising at least one rectifier circuit connectable to the power supply voltage, an intermediate circuit having at least one intermediate circuit capacitor, and a bridge switching device connected to the drive motor on the output side, the bridge switching device providing an AC or DC power supply to the drive motor, wherein the power supply circuit of the drive motor is controlled by a control device for accelerating and braking the drive motor. The method for electrically braking the drive motor comprises the steps of isolating the intermediate circuit from the power supply and adjusting the intermediate circuit voltage to a predetermined value greater than zero, wherein the intermediate circuit capacitor is fed in the generator operation of the drive motor.

[0003] Patent document DE102007059492B4 discloses an industrial robot, which has a robot arm, the robot arm has multiple axes and at least one electric drive, the electric drive has a three-phase AC motor and a power electronic device for controlling the three-phase AC motor, wherein the power electronic device has a three-phase inverter for driving the three-phase AC motor and an intermediate circuit having an intermediate circuit capacitor and connected upstream to the three-phase inverter, the intermediate circuit having a first braking resistor and a first switch; wherein the electric drive is designed to move the relevant axis; wherein the industrial robot is designed to short-circuit the three-phase AC motor simultaneously by means of two independent current paths under the framework of emergency braking, and to close the first switch during emergency braking to connect the braking resistor in parallel with the intermediate circuit capacitor so that one of the two current paths for emergency braking passes through the first braking resistor. Summary of the invention

[0004] The object of the present invention is to provide a method for controlling at least one servomotor by means of a converter which method can be operated particularly efficiently and safely.

[0005] The object of the present invention is achieved by a method for controlling at least one servo motor by means of a converter, the converter comprising:

[0006] - input circuit connected to the grid,

[0007] - a DC voltage intermediate circuit capable of being fed by the input circuit,

[0008] a first switching device which, in its switched-on state, is designed to feed electrical energy from the input circuit into the DC voltage intermediate circuit and, in its switched-off state, to shut down the supply of electrical energy from the grid to the DC voltage intermediate circuit, so that no electrical energy can enter the DC voltage intermediate circuit from the grid,

[0009] at least one inverter circuit which can be fed from a DC voltage intermediate circuit and has controllable power semiconductor switches for electrically controlling the servomotor, and

[0010] - a second switching device, which is configured to feed the electric energy from the inverter circuit to the servo motor to drive the servo motor in its on state, and to stop driving the servo motor in its off state so that the electric energy for driving the servo motor cannot enter the servo motor from the inverter circuit,

[0011] The method comprises the following steps:

[0012] - monitoring the current flow of the circuit of the DC voltage intermediate circuit connected to the input circuit,

[0013] - upon occurrence of the stop signal, switching off the first switching device in order to terminate the supply of the DC voltage intermediate circuit from the grid,

[0014] - braking the servomotor in a generative braking mode or by short-circuit braking by actuating power semiconductor switches of the inverter circuit to reduce the rotational speed of the servomotor when it is determined by monitoring after the first switching device has been switched off that no current flows in the circuit of the DC voltage intermediate circuit connected to the input circuit,

[0015] If, after switching off the first switching device, monitoring determines that current is flowing in the circuit of the DC voltage intermediate circuit connected to the input circuit, switching off the second switching device in order to stop feeding electrical energy from the DC voltage intermediate circuit to the servomotor.

[0016] Although frequency converters are usually used as converters, in which the DC voltage intermediate circuit of the frequency converter is fed by an AC voltage network, the invention can also be used in converters fed by a DC network. In this case, no rectifier circuit is required on the input side, because the AC voltage does not have to be rectified before the electrical energy can be supplied to the DC voltage intermediate circuit due to the DC network. The input circuit can therefore have a very simple structure and can be formed, for example, by the first switching device alone.

[0017] In most current applications, a high-power DC voltage network is not readily available. The invention can be implemented in the form of a frequency converter which is fed from an AC voltage network and has a rectifier circuit as input circuit.

[0018] Therefore, the object of the present invention can be achieved in particular by a method in which the converter is designed as a frequency converter, the power grid is an AC voltage network, and the input circuit is designed as a rectifier circuit, the method comprising the following steps:

[0019] - monitoring the current flow of a circuit of the DC voltage intermediate circuit connected to the rectifier circuit,

[0020] - upon occurrence of the stop signal, switching off the first switching device in order to terminate the supply of the DC voltage intermediate circuit from the AC voltage network,

[0021] - braking the servomotor in a generative braking mode or by short-circuit braking by actuating power semiconductor switches of the inverter circuit to reduce the rotational speed of the servomotor when it is determined by monitoring after the first switching device has been switched off that no current flows in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit,

[0022] If, after switching off the first switching device, monitoring determines that current is flowing in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit, switching off the second switching device in order to stop feeding electrical energy from the DC voltage intermediate circuit to the servomotor.

[0023] In the case of feeding the frequency converter from an AC voltage network via an input-side rectifier circuit, the rectifier circuit can be constructed as a controlled three-phase bridge (B6C), in which thyristors are used as rectifying elements instead of diodes. Thyristors are switchable elements that are non-conductive, i.e. switched off, in an initial state and can be switched on by a control current on the gate electrode of the thyristor. After being switched on, the thyristor can remain conductive, i.e. switched on, even when there is no current on the gate electrode. When the minimum through current, the so-called holding current, is lowered, the thyristor is switched off. In this regard, in a particular embodiment, the first switching device is formed by a controllable thyristor of a rectifier circuit constructed as a controlled three-phase bridge (B6C).

[0024] In another embodiment, in particular in the embodiment of the rectifier circuit as an uncontrolled three-phase bridge (B6U), the rectifier circuit can have uncontrolled diodes and the first switching device can be formed by a separate switch. The switch separated from the rectifier circuit can also be formed by a semiconductor element, but can also be formed by an electromechanical switch if necessary. The switch separated from the rectifier circuit can have the advantage in particular that the DC voltage intermediate circuit can be separated from the grid current.

[0025] Therefore, the object of the present invention is also achieved in particular by a method for controlling at least one servo motor by means of a frequency converter, the frequency converter comprising:

[0026] - a rectifier circuit connected to an alternating voltage network,

[0027] - a DC voltage intermediate circuit capable of being fed from a rectifier circuit,

[0028] a first switching device which is designed to feed electrical energy from the rectifier circuit to the DC voltage intermediate circuit in its switched-on state and to electrically separate the DC voltage intermediate circuit from the rectifier circuit in its switched-off state, so that electrical energy cannot pass from the rectifier circuit into the DC voltage intermediate circuit,

[0029] at least one inverter circuit which can be fed from a DC voltage intermediate circuit and has controllable power semiconductor switches for electrically controlling the servomotor, and

[0030] a second switching device, which is configured to feed electrical energy from the inverter circuit to the servomotor in its switched-on state and to electrically disconnect the servomotor from the inverter circuit in its switched-off state so that electrical energy cannot enter the servomotor from the inverter circuit,

[0031] The method comprises the following steps:

[0032] - monitoring the current flow of a circuit of the DC voltage intermediate circuit connected to the rectifier circuit,

[0033] - upon occurrence of the stop signal, switching off the first switching device in order to electrically separate the DC voltage intermediate circuit from the rectifier circuit,

[0034] - braking the servomotor in a generative braking mode by actuating power semiconductor switches of the inverter circuit to reduce the rotational speed of the servomotor when it is determined by monitoring after the first switching device has been switched off that no current flows in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit,

[0035] If, after the first switching device has been switched off, monitoring has detected that a current is flowing in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit, the second switching device is switched off in order to electrically separate the inverter circuit from the servomotor.

[0036] The method according to the invention can in principle be implemented to control a single servomotor. However, the method according to the invention can in particular be implemented to control at least two servomotors. In a specific embodiment of the drive for a robot arm, the method according to the invention can, for example, be implemented to control six or seven servomotors, which form the drive for the robot arm.

[0037] Braking according to the method of the invention is understood in particular to mean that during the execution of the method, the one or more servomotors are braked neither by mechanical braking nor by (electro)mechanical braking, but rather during the execution of the method, in particular in the generative operation of the actively controlled inverter circuit of the one or more servomotors, they are braked electrically at most by short-circuit braking. Thus, in such an actively controlled generative operation of the one or more servomotors, the inverter circuit is fed with electrical energy from a DC voltage intermediate circuit, so that by switching on and off the control of the power semiconductor switches of the inverter circuit, corresponding alternating currents can be introduced into the windings of the one or more servomotors, which generate magnetic fields, which generate a braking mechanical force on the one or more servomotor shafts. Braking is understood to mean a reduction in the rotational speed of the corresponding servomotor shaft. Braking does not necessarily have to be performed until the corresponding servomotor shaft comes to a complete standstill. Instead, braking can only be performed from a higher first rotational speed to a lower second rotational speed, which is less than the first rotational speed. However, braking can in particular be performed until a complete standstill.

[0038] In the case of actuating two or more servomotors according to one of the methods according to the invention, it is not necessary for all servomotors to be brake-actuated simultaneously. Instead, at any point in time, a first group of a subset of servomotors can be selectively brake-actuated, while a second group of another subset of servomotors can be driven stably at a constant speed, not driven, i.e., in idling, or even driven in an accelerated manner. In a special state, only individual servomotors can be brake-actuated in a generatorisch abbremsend angesteuert, while the other servomotors are not brake-actuated in a generatorisch abbremsend angesteuert. In a special state, all servomotors can be brake-actuated in a generatorisch abbremsend angesteuert simultaneously.

[0039] At least one servomotor is electrically controlled with the aid of a frequency converter according to the invention with respect to its position (motor position, i.e. the current angular position of the motor shaft), its rotational speed, its acceleration and / or its braking behavior (negative acceleration). In the case of two or more servomotors, the frequency converter has a number of inverter circuits corresponding to the number of servomotors. In this case, the plurality of inverter circuits can be connected to a common DC voltage intermediate circuit. When the frequency converter is connected to an AC voltage network, the common DC voltage intermediate circuit is fed from the same AC voltage network by a common rectifier circuit.

[0040] The AC voltage network is provided with electrical energy by the power grid of the energy supplier. This is usually a low-voltage power grid. The low-voltage power grid can be a three-phase AC voltage network in particular. The three-phase AC voltage network provides a sinusoidal network AC voltage. The sinusoidal network AC voltage can have an effective value in particular, under which there is a voltage of, for example, 230 volts between the outer conductor of the three-phase AC voltage network and the neutral conductor of the three-phase AC voltage network, and there is a voltage of, for example, 400 volts between each two of the three outer conductors. The grid frequency can be, for example, 50 Hz or 60 Hz. The three-phase AC voltage network can be configured in particular as a TN system, which includes three outer conductors (L1, L2, L3), a neutral conductor (N) and a protective conductor (PE).

[0041] The rectifier circuit of the frequency converter may be, for example, a three-phase rectifier. The three-phase rectifier may be implemented in the form of an uncontrolled three-phase bridge structure.

[0042] When the frequency converter is connected to the AC voltage network, electrical energy is fed into the DC voltage intermediate circuit from the AC voltage network. When the DC voltage intermediate circuit is disconnected from the AC voltage network, only electrical energy is supplied to the DC voltage intermediate circuit from the inverter circuit, which can provide electrical energy in generative operation of the at least one servomotor.

[0043] During the operating time during which the method according to the invention can be carried out, electrical energy can also be output from the intermediate circuit capacitor, specifically either to the inverter circuit or to a braking resistor of the DC voltage intermediate circuit.

[0044] In this case, the braking resistor is configured to extract electrical energy from the DC voltage intermediate circuit and convert it into heat when it is connected to the DC voltage intermediate circuit. The braking resistor has no electrical effect on the DC voltage intermediate circuit when it is separated from the DC voltage intermediate circuit, i.e., the DC voltage intermediate circuit is not affected by the braking resistor when the braking resistor is separated. The braking chopper is a controllable switch, by which the braking resistor can be connected and / or separated from the DC voltage intermediate circuit. In this regard, the braking chopper can be operated in a pulse width controlled manner.

[0045] The inverter circuit fed by the DC voltage intermediate circuit includes power semiconductor switches, which can be electronically controlled, for example, by an associated drive circuit. The inverter circuit can be a three-phase inverter and is configured, for example, as a two-stage inverter (U-inverter) or a pulse inverter. In the inverter circuit, when the current and the voltage have the same sign, the power semiconductor switch conducts the electrical energy to the servo motor. The electrical energy thus flows out of the DC voltage intermediate circuit and flows into the servo motor. In the generative operation, it can be provided that the freewheeling diodes assigned to the power semiconductor switches do not divert the electrical energy in order to transfer the generative energy from one or more servo motors back to the DC voltage intermediate circuit, that is, the intermediate circuit capacitor, but the power semiconductor switch can remain activated and can be controlled accordingly by the drive circuit assigned to the power semiconductor switch, so as to draw electrical energy from the servo motor and feed it into the DC voltage intermediate circuit, that is, the intermediate circuit capacitor.

[0046] In the method according to the invention, a separation of the DC voltage intermediate circuit from the AC voltage network is performed, which is at least advantageous, for example, in the case of an emergency stop of a corresponding machine driven by at least one servomotor, or is even absolutely necessary for certain safety requirements that must be complied with.

[0047] Thus, for example, for industrial robots, in the event of an emergency stop of stop category 0 (e.g. according to standard EN 60204-1), provision is made for immediate interruption of the power supply, in particular if, for example, mechanical separation, i.e. decoupling in the drive system and / or mechanical braking cannot be achieved alone.

[0048] On the other hand, a machine, such as an exemplary industrial robot, can have a system state in which a controlled reduction in the speed of the servomotors, in particular to a stationary state with a speed of zero, can be carried out more quickly than a simple mechanical braking in which the speed of the servomotors is not reduced in a controlled manner. In this case, a stop of stop category 0 or stop category 1 (e.g. according to standard EN60204-1) can be carried out, during which a controlled stop of the machine is carried out, wherein in order to be able to carry out such a controlled stop, it is necessary to maintain the power supply to the servomotors. The power supply is interrupted only when one or more servomotors have reached the stationary state.

[0049] However, for emergency stops of stop category 0 and stops of stop category 1, provision can be made to additionally use an STO function (Safe Torque Off according to standard EN 61800-5-2) associated with the servo motor or integrated in the servo drive.

[0050] The first switching device can be a first relay, in particular a first relay with a rail-guided switching contact, a first contactor, in particular a first contactor with a double or multiple break-off switching contact. Alternatively or additionally, the second switching device can be a second relay, in particular a second relay with a rail-guided switching contact, a second contactor, in particular a second contactor with a double or multiple break-off switching contact.

[0051] Although the first switching device and the second switching device can generally be configured as mechanical switches, in an extension according to the present invention, it is specifically proposed that the first switching device is configured as a first semiconductor switching device and / or the second switching device is configured as a second semiconductor switching device. In the design as semiconductor switching devices, the first semiconductor switching device and / or the second semiconductor switching device can, for example, include one or more transistors, in particular MOS-FETs and / or one or more thyristors, in particular GTO thyristors.

[0052] According to an embodiment, the first switching device can be formed in particular by controlled thyristors of a rectifier circuit configured as a controlled three-phase bridge (B6C). Alternatively or additionally, the second switching device can be formed in particular by power semiconductor switches of an inverter circuit of the converter. In this regard, a separate switch, i.e. a switch that is different from the rectifier circuit and / or the inverter circuit, can be omitted.

[0053] Both in the case of a relay-like electromechanical switch design and in the case of a semiconductor switch design, the first switching device and the second switching device can be designed as simple switches, ie, as non-redundant switches.

[0054] The first switching device, in particular the first semiconductor switching device, can be configured in the switching circuit of the rectifier circuit and in the DC voltage intermediate circuit to switch in such a way that the rectifier circuit remains connected to the AC voltage network even in the switched-off state of the first switching device.

[0055] Due to the structural design of the electromechanical relay and in any case the design as a semiconductor switching device, both the first switching device and the second switching device are disconnected in an unsafe manner, since there is no galvanic separation from the AC voltage network.

[0056] Therefore, in a special embodiment of the method, the safety stop function is implemented in the following manner: namely, the current flow of the circuit of the DC voltage intermediate circuit connected to the rectifier circuit is monitored. When the stop signal occurs, the first switching device is turned off to electrically separate the DC voltage intermediate circuit from the rectifier circuit. Then, if the monitoring of the current flow in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit determines that no current flows in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit after the first switching device is turned off, the servo motor is braked in a generative braking operation by controlling the power semiconductor switches of the inverter circuit to reduce the rotation speed of the servo motor. However, if the monitoring of the current flow in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit determines that there is current flowing in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit after the first switching device is turned off, that is, the monitoring determines that there is still current despite the shutdown, then the STO function (safe torque off according to the EN61800 standard) is activated, which directly interrupts the power supply to one or more servo motors.

[0057] In known controlled drive systems with an intermediate circuit, in order to meet certain requirements for functional safety, it is necessary to shut down the energy flow from the power supply system, i.e. from the AC voltage network, via the intermediate circuit into the drive system, i.e. the servo motor. In the prior art, the energy flow into the drive system is shut down by means of switching elements at the input of the rectifier circuit, i.e. by means of the feed-in unit. Electromechanical or electronic components can be used as switching elements.

[0058] However, when the energy flow through the feed unit is switched off, this must be monitored or performed redundantly in accordance with functional safety requirements. According to the known prior art, direct monitoring of the energy flow does not take place.

[0059] Alternatively, the energy flow can be shut off by a control device. In this case, however, the control device cannot be used to stop the drive system quickly, for example to execute a ramp stop.

[0060] If the feed unit has an electromechanical switching element (eg a main contactor), a safe shutdown can be performed via the contactor. However, if the feed unit is designed as a diode rectifier or a half-controlled thyristor bridge without further switching elements, the energy supply cannot be shut down in accordance with functional safety regulations.

[0061] The method according to the invention makes it possible, if necessary, to implement a safe energy shutdown in the feed-in unit, ie in the rectifier circuit, in particular on the basis of semiconductor components or without the addition of electromechanical switches.

[0062] Electromechanical switching elements should be avoided to the greatest extent possible due to wear and poor reliability.

[0063] In contrast to the prior art, the energy flow from the feed unit to the intermediate circuit is monitored. The energy flow into the drive system is shut off by means of, in particular, non-redundant switches in the feed unit, i.e., in particular by means of thyristors of a rectifier circuit designed as a controlled three-phase bridge (B6C). By shutting off the energy flow and in combination with monitoring the energy flow, the regulating device can still be regulated in a controlled manner, rather than just being shut off. The advantage over the prior art is that the drive system can be shut down more quickly and in a manner adapted to the operating situation.

[0064] The energy flow is switched off at the feed-in unit. The energy flow is monitored by a measuring device in the intermediate circuit to zero or a defined threshold value. This monitoring can be carried out by a measuring device in the output current (Hinstrom) or the return current (Rückstrom), or in both simultaneously. When the energy flow from the feed-in unit to the intermediate circuit is zero, the drive system can still be controlled by the regulating device using the residual energy in the intermediate circuit.

[0065] The measuring device can be continuously monitored during continuous operation, since the energy flow is continuously detected. The operability of the measuring device can therefore be continuously verified. If the measuring device determines that the feed-in unit does not correctly separate the energy flow from the power supply system, it can still be directly switched off by the second control device on the inverter circuit.

[0066] The current flow in the circuit of the DC voltage intermediate circuit connected to the rectifier circuit can be monitored by performing a single current measurement in one of the two lines of the circuit connecting the rectifier circuit to the DC voltage intermediate circuit.

[0067] The current measurement can be performed, for example, by one or more current sensors galvanically isolated from the circuit or by one or more measuring resistors (shunts) connected to the circuit. The current sensor or one or more measuring resistors can be connected to a control device that performs monitoring and / or evaluation.

[0068] Alternatively, the monitoring of the current flow in a circuit of the DC voltage intermediate circuit connected to the rectifier circuit can be carried out redundantly by means of a double current measurement, more precisely not only in a line of the circuit connecting the rectifier circuit to the DC voltage intermediate circuit (output line), but also in another line of the circuit connecting the rectifier circuit to the DC voltage intermediate circuit (return line).

[0069] The current measurement, which is redundant in this respect, can be performed, for example, by two or more current sensors separated from the circuit current or by two or more measuring resistors (shunts) connected to the circuit. Here, the current sensors and / or measuring resistors can also be selectively designed in a diversified manner. For example, current sensors and measuring resistors can be provided for redundant current measurement.

[0070] In all embodiment variants of the method, during continuous operation of the frequency converter, the current flow of the circuit of the DC voltage intermediate circuit connected to the rectifier circuit can also be monitored during the operational control of the servomotor independently of the presence of a stop signal. This monitoring during the operational control of the servomotor independently of the presence of a stop signal can be performed intermittently, i.e. at discrete time intervals, in particular at regular time intervals. Alternatively, this monitoring during the operational control of the servomotor independently of the presence of a stop signal can be performed continuously, i.e. without interruption or permanently.

[0071] By monitoring the current flow of the circuit of the DC voltage intermediate circuit connected to the rectifier circuit during the continuous operation of the frequency converter, also during the operational control of the servomotor, independently of the presence of a stop signal, a continuous credibility test can be performed on the current sensor and / or the measuring resistor. Thus, during the operational control of at least one servomotor, the electrical energy currently required or necessary for the control can be determined, and the currently required current can be derived therefrom as its nominal value and compared with the current value detected by the current sensor and / or the measuring resistor. If the measured current value deviates from the expected current value by more than a tolerable difference, it can be determined that a fault has occurred in the current measurement, in particular that a fault has occurred in the current sensor and / or the measuring resistor. As a result, the reliability of the monitoring or current measurement can be checked continuously and, in the event of a fault, a safe state can be entered even if the stop function has not yet been triggered.

[0072] The value of the current intensity in the output line of the DC voltage intermediate circuit can be directly compared and identical with the value of the current intensity in the return line of the DC voltage intermediate circuit, or the current variation curve detected by monitoring the current flow of the circuit connected to the rectifier circuit of the DC voltage intermediate circuit can be compared with the control signal for the frequency converter and / or with the current and / or voltage variation curve between the inverter circuit and the servo motor, wherein functional information about the electrical component performing the monitoring can be obtained from the comparison. In a preferred monitoring method, the value of the current intensity in the output line of the DC voltage intermediate circuit can be directly compared and identical with the value of the current intensity in the return line of the DC voltage intermediate circuit.

[0073] The electrical component performing the monitoring may be, for example, a current sensor galvanically separated from the circuit or a measuring resistor (shunt) connected to the circuit.

[0074] The object of the present invention is also achieved by a control device for controlling at least one servo motor by a frequency converter, the control device comprising: a detection device for detecting a current and / or voltage variation curve in a circuit of a DC voltage intermediate circuit of the frequency converter connected to a rectifier circuit of the frequency converter; a signal input end for receiving a stop signal of a machine controller for controlling the servo motor; a first signal output end for controlling a first switching device of the frequency converter, the first switching device being constructed to feed electrical energy from the rectifier circuit to the DC voltage intermediate circuit in its on state and to electrically separate the DC voltage intermediate circuit from the rectifier circuit in its off state so that electrical energy cannot enter the rectifier circuit from the rectifier circuit; and a second signal output end for controlling a second switching device of the frequency converter, the second switching device being constructed to feed electrical energy from the inverter circuit to the servo motor in its on state and to electrically separate the servo motor from the inverter circuit in its off state so that electrical energy cannot enter the servo motor from the inverter circuit, wherein the control device is constructed to perform a method according to one or more of the embodiments of the present invention.

[0075] The control device can have a detection device including at least one current sensor, wherein the detection device is designed to carry out a single current measurement in one of two lines of the circuit which connect the rectifier circuit to the DC voltage intermediate circuit.

[0076] The detection device can, for example, receive, i.e. collect, the measured values ​​of one or more current sensors electrically separated from the circuit or the measured values ​​of one or more measuring resistors (shunts) connected to the circuit. One or more current sensors or one or more measuring resistors can be connected to the control device, which performs monitoring and / or evaluation.

[0077] The control device can have a detection device including two current sensors, wherein the detection device is designed to perform double current measurement redundantly and / or diversely not only in one line of the circuit connecting the rectifier circuit to the DC voltage intermediate circuit, but also in another line of the circuit connecting the rectifier circuit to the DC voltage intermediate circuit.

[0078] The redundantly constructed detection device can for example receive, i.e. collect the measured values ​​of two or more current sensors electrically separated from the circuit or two or more measured values ​​of the measuring resistors (shunts) connected to the circuit. The current sensor and / or the measuring resistor can be connected to a control device at this time, and the control device performs monitoring and / or evaluation. At this, the current sensor and / or the measuring resistor can also be optionally designed in a diversified manner. For example, a current sensor and a measuring resistor can be provided for redundant current measurement.

[0079] In the case of an exemplary application of a robot arm, the robot arm may have a plurality of joints and a plurality of limbs, which can be adjusted relative to one another by the movement of the joints of the robot arm. In this case, each joint may be assigned its own servomotor. Each of these servomotors is designed to adjust the joint of the robot arm assigned to it, more precisely by automatic control of the servomotor. For this purpose, the robot arm may have a control device, which is designed to automatically control the servomotors of the robot arm so that the limbs of the robot arm are automatically adjusted relative to one another by the drive movement of the joints.

[0080] Each joint and therefore each servomotor assigned to each joint moves a kinematic system, which is respectively formed by a distal kinematic subsystem installed upstream of the servomotor in the kinematic chain of the robot arm. Therefore, the servomotor arranged at the proximal end in the kinematic chain (servomotor of the base axis of the robot arm) usually has to be braked with a higher kinetic energy than the servomotor arranged at the distal end (servomotor of the hand axis of the robot arm). However, depending on the posture of the joints of the robot arm, another servomotor can be loaded with the currently highest braking load at any point in time. Thus, for example, a situation may arise in which the base joint that just reacts to the upward movement of gravity should be braked, and the braking force is therefore mainly provided by gravity, and the relevant servomotor is therefore not subject to a specific electrical braking load. On the other hand, the lighter hand joint of the robot arm may move exactly in the direction of gravity, so that when braking, the acting gravitational acceleration must be additionally reacted by the servomotor, and the servomotor assigned to this lighter hand joint is therefore subject to a particularly high electrical braking load.

[0081] Therefore, the purpose of the present invention is also achieved by a robot, which has: a robot arm, which has multiple joints and multiple limbs, and the limbs can be adjusted relative to each other by the movement of the joints of the robot arm, wherein at least one joint is equipped with a servo motor, and the servo motor is constructed to adjust the at least one joint, and the adjustment is performed by automatic control of the servo motor; and a robot controller, which is constructed to automatically control at least one servo motor of the robot arm so as to adjust the limbs of the robot arm relative to each other by driving the joints, wherein the robot controller includes a control device according to the present invention as described in one or more of the preceding embodiments, or is connected to the control device according to one or more of the preceding embodiments by control technology.

[0082] The at least one servomotor can in particular be a permanently excited synchronous motor.

[0083] The control device can be designed as part of the robot controller. Alternatively, however, the control device can also be designed as a separate control unit, which cooperates with the robot controller, for example by means of a communication connection. The control device is designed in particular for controlling a frequency converter, which comprises: a rectifier circuit connectable to an AC voltage network; a DC voltage intermediate circuit fed by the AC voltage network in the state connected to the AC voltage network, the DC voltage intermediate circuit having an intermediate circuit capacitor and a brake resistor connectable and disconnectable by a brake chopper of the DC voltage intermediate circuit; and at least one inverter circuit fed by the DC voltage intermediate circuit, the inverter circuit having controllable power semiconductor switches.

[0084] The object of the present invention is also achieved by a computer program product, which has a machine-readable carrier on which a program code is stored, which can be read by a control device according to one or more embodiments of the present invention, and the program code constructs and / or designs the control device to perform the method according to one or more embodiments of the present invention when the program code is executed by the control device.

[0085] The computer program product may be, for example, a CD, a DVD or a USB flash drive. The computer program product may also be a control card with an integrated microprocessor. However, the computer program product may also be implemented in the form of a download that can be provided and sold via the Internet or other networks.

[0086] Therefore, the machine-readable carrier can be a CD, a DVD or a microprocessor on which the program code is stored. The machine-readable carrier can also be a hard disk or an SSD drive to which the program code has been downloaded, for example, in particular in the form of a data packet.

[0087] The program code may be represented by a compiled program and / or data stored on a machine-readable carrier.

[0088] By reading in the edited program and / or data, the read-in control device is constructed and / or designed to be able to carry out the method according to the invention.

[0089] The method according to the invention is carried out when the control device actually executes the program code, ie the compiled program, and / or actually processes the data accordingly. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The specific features of these exemplary embodiments can be considered as general features of the present invention individually or in combination as needed, regardless of where these features are mentioned in the context. Among them:

[0091] Figure 1 A flowchart showing an exemplary method of the present invention is shown,

[0092] Figure 2 A side view of an exemplary industrial robot is shown, which includes a robot arm with limbs, joints and servo motors and a robot controller, the robot controller being configured to perform the method according to the present invention,

[0093] Figure 3 schematically shows a circuit diagram of an exemplary frequency converter having an exemplary single servo motor and a first switching device implemented by a thyristor of a rectifier circuit,

[0094] Figure 4 A circuit diagram of a modified frequency converter is schematically shown, which has a servo motor and a first switching device separated from a rectifier circuit and a second switching device separated from an inverter circuit, and

[0095] Figure 5 A circuit diagram of an exemplary variant of a frequency converter is schematically shown, which has two or more servomotors, which are, for example, based on Figure 3 Connection to a common DC voltage intermediate circuit. DETAILED DESCRIPTION

[0096] exist Figure 1 The schematic diagram of the method according to the present invention is shown in FIG. Figure 3 , Figure 4 ) is a flowchart of an exemplary method for controlling at least one servo motor M.

[0097] like Figure 3 and Figure 4 As shown in , the frequency converter 1 may include:

[0098] A rectifier circuit 3 connected to an AC voltage network 2; a DC voltage intermediate circuit 4 capable of being fed by the rectifier circuit 3; a first switching device 21, which is constructed to feed electrical energy from the rectifier circuit 3 to the DC voltage intermediate circuit 4 in its connected state, and to electrically separate the DC voltage intermediate circuit 4 from the rectifier circuit 3 in its off state, so that electrical energy cannot enter the DC voltage intermediate circuit 4 from the rectifier circuit 3; at least one inverter circuit 7 capable of being fed from the DC voltage intermediate circuit 4, which has controllable power semiconductor switches S1-S6 for electrically controlling the servomotors M, M1-M6; and a second switching device 22, which is constructed to feed electrical energy from the inverter circuit 7 to the servomotors M, M1-M6 in its connected state, and to electrically separate the servomotors M, M1-M6 from the inverter circuit 7 in its off state, so that electrical energy cannot enter the servomotors M, M1-M6 from the inverter circuit 7.

[0099] The DC voltage intermediate circuit 4 can have an intermediate circuit capacitor 5 and a braking resistor 6 which can be connected and disconnected via a braking chopper S7 of the DC voltage intermediate circuit 4 .

[0100] like Figure 1 As shown, the method according to the present invention comprises the following steps:

[0101] In a first step ST1 , the current flow of the circuit of the DC voltage intermediate circuit 4 which is connected to the rectifier circuit 3 is monitored.

[0102] When the stop signal occurs, the first switching device is switched off in a second step ST2 in order to electrically separate the DC voltage intermediate circuit 4 from the rectifier circuit 3 .

[0103] If, after shutting down the first switching device, it is determined through monitoring that no current flows in the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3, then in a third step ST3, the servomotors M, M1-M6 are braked in a generative braking operation or by short-circuit braking by controlling the power semiconductor switches S1-S6 of the inverter circuit 7 to reduce the rotational speed of the servomotors M, M1-M6.

[0104] On the other hand, if, after shutting down the first switching device, it is determined through monitoring that current is flowing in the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3, the second switching device is shut down in the fourth step ST4 instead of the third step ST3 to electrically separate the inverter circuit 7 from the servo motors M, M1-M6.

[0105] Figure 2An industrial robot 8 is shown, which has a robot arm 9 and a robot controller 10. In the case of the embodiment of the invention, the robot arm 9 comprises a plurality of joints G1 to G7 which are arranged one behind the other and are rotatably connected to one another via joints L1 to L6.

[0106] The industrial robot 8 has a robot controller 10 which is configured to execute a robot program and automatically move the joints G1-G7 and joints L1-L6 of the robot arm 9. One of the plurality of joints G1-G7 forms an end joint (G7) of the robot arm 9 which has a tool flange 11.

[0107] The robot controller 10 of the industrial robot 8 is constructed or designed to execute a robot program, by which the joints L1 to L6 of the robot arm 9 can be adjusted or rotated automatically according to the robot program or in manual guidance. For this purpose, the robot controller 10 is connected to controllable electric drives, namely servomotors M1 to M6, which are constructed to adjust the individual joints L1 to L6 of the robot arm 9.

[0108] In the case of the embodiment of the invention, the members G1 to G7 include a robot base 13 and a turntable 14 which is rotatably mounted relative to the robot base 13 about an axis A1 extending vertically. The other members of the robot arm 9 include a rocker arm 15, a cantilever arm 16 and a preferably multi-axial robot hand 17 which has a fastening device configured as a tool flange 11 for fastening a tool. The rocker arm 15 is pivotally mounted on the turntable 14 at the lower end, i.e. at the joint L2 (also referred to as the rocker arm bearing head) of the rocker arm 15 about a preferably horizontal rotation axis A2.

[0109] At the upper end of the rocker arm 15, at the first joint L3 of the rocker arm 15, a cantilever arm 16 is again pivotably mounted about an axis A3, which is also preferably horizontal. The cantilever arm carries the robot hand at the end with its preferably three rotation axes A4, A5, A6. The joints L1 to L6 can be driven in a program-controlled manner by the robot controller 10 via one of the corresponding servomotors M1 to M6. For this purpose, the servomotors M1 to M6 are equipped with a frequency converter 1 according to the invention, such as Figure 3 and Figure 4 The robot controller 10 and / or the related individual control devices may be configured to execute one or more of the methods according to the present invention.

[0110] Converter 1, i.e. Figure 3 , Figure 4 and Figure 5 The frequency converter 1a shown in FIG. 1 can be connected to an AC voltage network 2a. The AC voltage network 2a can be, for example, a three-phase AC voltage network of 50 Hz. It can in particular be configured as a TN system.

[0111] If the frequency converter 1a is connected to the power grid 2, i.e. to the AC voltage network 2a, its input circuit 3, i.e. the rectifier circuit 3a, can convert the AC voltage fed from the AC voltage network 2 into a corresponding DC voltage. This DC voltage is then supplied to the DC voltage intermediate circuit 4. In addition, in the embodiment shown, the DC voltage intermediate circuit 4 is also equipped with an intermediate circuit capacitor 5 and a brake resistor 6 which can be connected and disconnected via a brake chopper S7 of the DC voltage intermediate circuit 4.

[0112] At least one inverter circuit 7 is connected to the DC voltage intermediate circuit 4 , which inverter circuit 7 is fed by the DC voltage intermediate circuit 4 and has controllable power semiconductor switches S1 to S6 .

[0113] exist Figure 3 and Figure 4 In the embodiment shown, only a single inverter circuit 7 is connected to the DC voltage intermediate circuit 4. The single inverter circuit 7 supplies a single servomotor M with power.

[0114] exist Figure 5 In the case of the embodiment shown, a plurality of inverter circuits 7 are connected to the DC voltage intermediate circuit 4. The plurality of inverter circuits 7 are respectively connected to the DC voltage intermediate circuit 4. Figure 4 One of the plurality of servo motors M1 to M6 shown is powered. Figure 5 For ease of illustration, only two inverter circuits 7 and two servomotors M1 and M2 are shown in full. Dashed arrows and markings M3-M6 indicate a plurality of other servomotors M3, M4, M5 and M6 and other inverter circuits 7, all of which are connected to a common DC voltage intermediate circuit 4.

[0115] exist Figure 2 In the case of the exemplary industrial robot 8 shown, for example, a total of six inverter circuits 7 can be provided for the six servomotors M1 to M6 of the six joints L1 to L6 of the robot arm 9 .

[0116] In the case of the illustrated embodiment, the monitoring of the current flow of the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3a is performed either by a simple current measurement in the first line 23 of the circuit connecting the rectifier circuit 3a to the DC voltage intermediate circuit 4, or the monitoring of the current flow of the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3a is performed redundantly by double current measurement, more precisely, current measurement is performed not only in the first line 23 of the circuit connecting the rectifier circuit 3a to the DC voltage intermediate circuit 4, but also in the second line 24 of the circuit connecting the rectifier circuit 3 to the DC voltage intermediate circuit 4.

[0117] The detection device 25 comprises a current sensor 26 . 1 , wherein the detection device 25 is designed to carry out a single current measurement in one of the two lines 23 , 24 of the circuit which connect the rectifier circuit 3 a to the DC voltage intermediate circuit 4 .

[0118] However, the detection device 25 can also have two current sensors 26.1, 26.2, wherein the detection device 25 is constructed to perform double current measurement redundantly and / or diversely not only in the first line 23 of the circuit connecting the rectifier circuit 3a to the DC voltage intermediate circuit 4, but also in the second line 24 of the circuit connecting the rectifier circuit 3 to the DC voltage intermediate circuit 4.

[0119] according to Figure 3 and Figure 5 In the exemplary embodiment of FIG. 1 , the converter 1 is designed as a frequency converter 1 a , the power grid 2 is an AC voltage network 2 a , and the input circuit 3 is designed as a rectifier circuit 3 a .

[0120] In a first method step, the current flow of the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3a is monitored; when a stop signal occurs, the first switching device 21, 21b is turned off to end the power supply of the DC voltage intermediate circuit 4 from the AC voltage network 2a. If it is determined by monitoring after the first switching device 21, 21b is turned off that no current flows in the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3a, the servomotors M, M1-M6 are braked in a generative braking mode or by short-circuit braking by controlling the power semiconductor switches S1-S6 of the inverter circuit 7, so as to reduce the rotation speed of the servomotors M, M1-M6. On the other hand, if it is determined by monitoring after the first switching device 21, 21b is turned off that current flows in the circuit of the DC voltage intermediate circuit 4 connected to the rectifier circuit 3a, the second switching device 22, 22b is turned off to stop the feeding of electrical energy from the DC voltage intermediate circuit 4 to the servomotors M, M1-M6. Here, the first switching device 21 is formed by the thyristor 21b of the rectifier circuit 3a, and the second switching device 22b is formed by the power semiconductor switches S1-S6 of the inverter circuit 7. The thyristor 21b of the rectifier circuit 3a is controlled, for example, by the first signal output SA1 of the control device 27. The power semiconductor switches S1-S6 of the inverter circuit 7 are controlled, for example, by the second signal output SA2 of the control device 27.

[0121] In accordance with Figure 4In the embodiment of the present invention, the first switching device 21 is formed by a single switch 21a, and the second switching device 22 is formed by a single switch 22a. The first switching device 21 or the first switching devices 21 and 21a, and the second switching device 22 or the second switching devices 22 and 22a, and the detection device 25 or the current sensors 26.1 and / or 26.2 are connected to a control device 27, which performs monitoring.

[0122] The control device 27 and / or the robot controller 10 are correspondingly configured to control at least one servo motor M, M1-M6 according to the present invention through the frequency converter 1, and have: a detection device 25 for detecting a current and / or voltage change curve in a circuit of the DC voltage intermediate circuit 4 of the frequency converter 1a connected to the rectifier circuit 3a of the frequency converter 1, in particular through a second signal input terminal SE2 from a current sensor 26.1 and / or a current sensor 26.2; a first signal input terminal SE1 for receiving a stop signal of a machine controller (for example, the robot controller 10) for controlling the servo motors M, M1-M6; a first signal output terminal SA1 for controlling a first switching device 21a of the frequency converter 1a, which is constructed to, at In its connected state, the electrical energy from the rectifier circuit 3a is fed to the DC voltage intermediate circuit 4, and in its off state, the DC voltage intermediate circuit 4 is electrically separated from the rectifier circuit 3a, so that electrical energy cannot enter the DC voltage intermediate circuit 4 from the rectifier circuit 3a; and a second signal output terminal SA2, which is used to control the second switching device 22a of the frequency converter 1a, which is constructed to feed the electrical energy from the inverter circuit 7 of the frequency converter 1a to the servo motors M, M1-M6 in its connected state, and to electrically separate the servo motors M, M1-M6 from the inverter circuit 7 in its off state, so that electrical energy cannot enter the servo motors M, M1-M6 from the inverter circuit 7, wherein the control device 27 is constructed to execute the method.

Claims

1. A method for controlling at least one servo motor by means of a converter (1), the converter comprising: - an input circuit (3) connected to the grid (2), a DC voltage intermediate circuit (4) which can be fed by the input circuit (3), a first switching device, which is designed to feed electrical energy from the input circuit (3) into the DC voltage intermediate circuit (4) in its switched-on state and to stop the supply of electrical energy from the power grid (2) to the DC voltage intermediate circuit (4) in its switched-off state, so that no electrical energy enters the DC voltage intermediate circuit (4) from the power grid (2), at least one inverter circuit (7) which can be fed by the DC voltage intermediate circuit (4) and has controllable power semiconductor switches for electrically controlling the servomotor, and - a second switching device, which is configured to feed the electric energy from the inverter circuit (7) to the servo motor in its on state to drive the servo motor, and to stop driving the servo motor in its off state so that no electric energy for driving the servo motor enters the servo motor from the inverter circuit (7), The method comprises the following steps: - monitoring the current flow in the circuit of the DC voltage intermediate circuit (4) connected to the input circuit (3), - upon the occurrence of a stop signal, switching off the first switching device in order to terminate the supply of the DC voltage intermediate circuit (4) from the power grid (2), - braking the servomotor in a generative braking mode or by short-circuit braking by actuating the power semiconductor switches of the inverter circuit (7) in order to reduce the rotational speed of the servomotor if, after switching off the first switching device, the monitoring determines that no current flows in the circuit of the DC voltage intermediate circuit (4) connected to the input circuit (3), - If, after the first switching device is switched off, the monitoring determines that current is flowing in the circuit of the DC voltage intermediate circuit (4) connected to the input circuit (3), the second switching device is switched off in order to stop feeding electrical energy from the DC voltage intermediate circuit (4) to the servo motor.

2. The method according to claim 1, wherein: The converter (1) is designed as a frequency converter (1a), the power grid (2) is an AC voltage network (2a), and the input circuit (3) is designed as a rectifier circuit (3a), and the method comprises the following steps: - monitoring the current flow in the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a), - upon the occurrence of a stop signal, switching off the first switching device in order to terminate the supply of the DC voltage intermediate circuit (4) from the AC voltage network (2a), - braking the servomotor in a generative braking mode or by short-circuit braking by actuating the power semiconductor switches of the inverter circuit (7) in order to reduce the rotational speed of the servomotor if, after switching off the first switching device, the monitoring determines that no current flows in the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a), - If, after switching off the first switching device, the monitoring determines that current is flowing in the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a), the second switching device is switched off in order to stop feeding electrical energy from the DC voltage intermediate circuit (4) to the servo motor.

3. The method according to claim 2, characterized in that Monitoring of the current flow in a circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a) is achieved by performing a single current measurement in one of the two lines (23, 24) of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4).

4. The method according to claim 2, characterized in that: Monitoring of the current flow in the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a) is performed redundantly by means of a double current measurement, i.e., not only in a line (23) of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4), but also in another line (24) of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4).

5. The method according to any one of claims 2 to 4, characterized in that In continuous operation of the frequency converter (1a), the current flow of the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a) is monitored even during operational control of the servomotor, independently of the presence of a stop signal.

6. The method according to claim 5, characterized in that The numerical value of the current intensity in the output line of the DC voltage intermediate circuit (4) is directly compared with the numerical value of the current intensity in the return line of the DC voltage intermediate circuit (4), or the current variation curve detected by monitoring the current flow of the circuit of the DC voltage intermediate circuit (4) connected to the rectifier circuit (3a) is compared with the control signal for the frequency converter (1a), and / or with the current variation curve and / or the voltage variation curve between the inverter circuit (7) and the servo motor, and functional information about the electronic component performing the monitoring is obtained from the corresponding comparison.

7. A control device for controlling at least one servo motor via a frequency converter (1a), comprising: a detection device (25) for detecting a current variation curve and / or a voltage variation curve in a circuit of a DC voltage intermediate circuit (4) of the frequency converter (1a) connected to a rectifier circuit (3a) of the frequency converter (1a); a first signal input terminal (SE1) for receiving a stop signal of a machine controller for controlling the servo motor; a first signal output terminal (SA1) for controlling a first switching device of the frequency converter (1a), the first switching device being configured to feed electrical energy from the rectifier circuit (3a) to the DC voltage intermediate circuit (4) in its switched-on state; circuit (4), and in its off state, electrically separates the DC voltage intermediate circuit (4) from the rectifier circuit (3a), so that no electric energy enters the DC voltage intermediate circuit (4) from the rectifier circuit (3a); and a second signal output terminal (SA2) for controlling a second switching device of the frequency converter (1a), the second switching device being configured to feed electric energy from the inverter circuit (7) of the frequency converter (1a) to the servomotor in its on state, and to electrically separate the servomotor from the inverter circuit (7) in its off state, so that no electric energy enters the servomotor from the inverter circuit (7), wherein: The control device (27) is designed to carry out the method according to any one of claims 1 to 6.

8. The control device according to claim 7, characterized in that: The detection device (25) has at least one current sensor and is designed to perform a single current measurement in one of the two lines of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4).

9. The control device according to claim 8, characterized in that: The detection device (25) has two current sensors and is constructed to redundantly and / or diversely perform double current measurement not only in one line (23) of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4), but also in another line (24) of the circuit connecting the rectifier circuit (3a) to the DC voltage intermediate circuit (4).

10. A robot comprising a robot arm (9), wherein the robot arm has a plurality of joints and a plurality of limbs, wherein the limbs can be adjusted relative to each other by movement of the joints of the robot arm (9), wherein at least one joint is provided with a servo motor, wherein the servo motor is constructed to adjust the at least one joint, and the adjustment is achieved by automatic control of the servo motor; and the robot arm comprises a robot controller (10), wherein the robot controller is constructed to automatically control at least one servo motor of the robot arm (9) so that the limbs of the robot arm (9) are automatically adjusted relative to each other by movement of the driven joints, wherein the robot controller (10) comprises a control device (27) according to any one of claims 7 to 9 or is connected to the control device (27) according to any one of claims 7 to 9 by control technology.

11. A machine-readable carrier having a program code stored thereon, the program code being readable by a control device (27) according to any one of claims 7 to 9, and the program code constructing and / or designing the control device (27) to execute a method according to any one of claims 1 to 6 when the program code is executed by the control device (27).

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