Method and device for controlling the movement of a manipulating element
Patent Information
- Application Number
- EP2023786476
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-09-30
- Filing Date
- 2023-09-28
- Publication Date
- 2025-08-06
Smart Images
Figure 1.1
Abstract
Description
[0001] Method and device for controlling the movement of a handling element
[0002] The invention relates to a method and a device for controlling the movement of a handling element of a removal robot along a predetermined path with a location-dependent path speed, wherein the removal robot has several axes and a motor for each axis.
[0003] The production of components, for example made of plastic, is becoming increasingly automated and supported by robots. One class of robots used for this purpose are removal robots, which typically have a handling element, in particular a gripper, with which components can be removed from one location and placed at another. For example, removal robots can be used to remove injection-molded parts from an injection-molding system and transport them to another location for further processing or storage. Due to the complex structure, the usually tight space conditions and the often complex geometry of such production lines or systems, it is necessary for the handling elements to be guided along correspondingly complex paths. For this purpose, the removal robots typically have a plurality of axes, each of which is motorized.In addition to the path geometry, the speed of the handling element as a function of location is also part of the path specification. Typically, the handling element should be moved at the highest possible speed to maximize component throughput. The speed of the handling element along the path is generally not constant in removal robots and is usually limited by limits in the individual axes.
[0004] To ensure error-free processing of the specified path and orders, the picking robot must be able to achieve the required speeds and accelerations using the power grid available on site. To achieve this, the supply voltage of the picking robot must typically not fall below a certain lower limit. If the supply voltage falls below this limit, the picking robot cannot follow the specified path and is usually stopped, particularly for safety reasons. Typical error messages relate to a positioning or following error, or for example, an undervoltage. Numerous hardware technologies are available in the state of the art to minimize the impact of voltage drops or brief power interruptions. Examples include voltage stabilizers, additional energy storage devices in the voltage intermediate circuit, and UPS (uninterruptible power supply) systems.However, all these solutions require space and are often associated with considerable costs.
[0005] If the handling device were to deviate from the specified path in the event of a voltage drop, damage to the component, the system, and the picking robot cannot be ruled out. There may also be a danger to personnel present. It is therefore critical to ensure that the picking robot or handling element remains on the same path at all times. Unstable grids with frequent voltage drops or grids to which electrical machines with high starting current are connected therefore represent a challenging environment for production systems in general and picking robots in particular.
[0006] Several methods are known from the prior art to ensure safety in the vicinity of picking robots in the event of a supply voltage drop. For example, KR 2012 00445766 Bl shows an emergency stop procedure for an industrial robot with multiple axes. It shows a regulation for rapidly braking the axes in the event of an emergency stop, without deviating from the specified trajectory. However, a complete stop of the picking robot impairs the productivity of the industrial robot. This can lead to the standstill of an entire production line.
[0007] EP 0 879 119 B1 discloses a method for controlling a robot with multiple axes along a predetermined path. To protect the robot's mechanical components from overload, the path speed can be reduced if a maximum permissible torque is exceeded. The acceleration for the (other) axes is limited accordingly so that the robot continues to follow the path. EP 0 879 119 B1 contains no indication of how to handle a voltage drop.
[0008] EP 0 167 080 B1 shows a controller for the robot tip of stationary multi-axis industrial robots. Inadmissible speeds of individual axes should be avoided, as these could cause damage to the robot. At the same time, path accuracy can be maintained. For this purpose, a control unit is provided for optimally changing the path speed, which intervenes in cases where inadmissible speeds would occur in individual axes. To avoid inadmissible speeds, the control unit extrapolates expected target speeds in the individual axes and checks whether a permissible speed is exceeded in an axis. If this is the case, a path speed control section intervenes and the path speed is reduced until the limit value is undershot again.EP 0 167 080 Bl also contains no indication as to how a voltage drop should be handled.
[0009] US 10 345 827 B2 shows a control device for a robot with a single motor. Among other things, the control device is equipped with a device for detecting voltage fluctuations (“Voltage Fluctuation Detection Unit”). If the device for detecting voltage fluctuations determines that the voltage of the power source has fallen below a predetermined reference value, either the rotational speed of the motor is reduced and / or the speed is reduced. In a second exemplary embodiment, it is shown how a robot with a single motor transports a semiconductor wafer onto an aligner. Once the wafer has been placed on the aligner, the aligner can adjust the alignment of the wafer. The aligner has a separate motor for this purpose. The robot motor and the aligner motor are independent of one another and operate separate devices.The document gives no indication that—or even how—a multi-axis robot could be controlled in the event of a voltage drop. JP H0530776 A discloses a method for manufacturing glass, whereby voltage variations can be detected and the speed of a motor reduced.
[0010] It is therefore an object of the invention to alleviate or eliminate all or at least some of the disadvantages of the prior art. Preferably, the object of the invention is to operate a multi-axis removal robot stably even in the event of a supply voltage drop, without requiring a handling device of the removal robot to stop and / or deviate from a predetermined path.
[0011] The object is achieved by a method according to claim 1. The method is a method of the type mentioned at the outset and comprises the following steps:
[0012] - Determining the next positions of the axes for moving to the next position of the handling element along the path;
[0013] - Detecting a supply voltage;
[0014] - Adjusting, in particular reducing, the path speed in the event of a limit value of the detected supply voltage being undershot; and
[0015] - Determining a speed for each of the axes to assume the next position depending on the calculated next positions of the axes and the adjusted path speed;
[0016] - Control and / or regulate the motors according to the calculated speeds for each of the axes.
[0017] The object is also achieved by a device according to claim 6. The device is a device of the type mentioned at the beginning and comprises:
[0018] - a measuring device for detecting a supply voltage;
[0019] - a processing device, preferably a processor, configured to receive the detected supply voltage from the measuring device, to determine the next positions of the axes for moving to a next position of the handling element along the path, further configured to adjust, in particular reduce, the path speed in the event of a limit value of the detected supply voltage being undershot and to determine the speed for each of the axes for assuming the next position depending on the determined next positions of the axes and the adjusted path speed; and
[0020] - at least one axis control device for controlling and / or regulating the motors according to the determined speed for each of the axes.
[0021] The path here refers to a set of positions or a path in three-dimensional space. If strictly monotonically increasing points in time are assigned to the individual positions along the path, the result is a trajectory. In addition to the information about the positions, the trajectory also contains the specified path speed along the path. The specified path along which the handling element is to be moved is typically divided into segments which are described or approximated by polynomials and can be evaluated at specific points in time. The handling element can form an end effector of the removal robot. For example, the handling element can be a gripper. In order to determine orTo calculate the position of the axes, the processing device determines the next positions of the axes from a (current) position along the path in order to move to the next position(s) along the path. In this way, the handling element can be moved along the path. The positions and / or the positions of the axes can, for example, be stored in a table or calculated during operation. The position along the path can be transformed into the coordinates of the axes, i.e. into the joint space. Optionally, a fine interpolator can be inserted to improve the approximation of the path. The measuring device for detecting the supply voltage measures the current supply voltage and transmits this value to the processing device. The measuring device can, for example, be a voltage measuring sensor, a multimeter or an oscilloscope.For example, the measuring device can be a sensor connected to the processing device. An output stage can be connected in front of each motor, whereby each output stage can contain an analog / digital converter (ADC) for voltage measurement. The measuring device can therefore also be formed by one or more ADCs, which can be contained in the output stages and record the voltage. The motors can be controlled or regulated using pulse width modulation (PWM). The PWM signal can therefore also be used to indirectly measure the supply voltage, since the PWM signal is typically approximately inversely proportional to the supply voltage. With higher input voltages of output stages, in particular inverters, the duty cycle can be selected to be lower than with low input voltages.The measurement can be performed continuously or, preferably, at discrete times. For example, sampling or measurement can be performed at a multiple of the frequency of the higher-level power grid. The supply voltage powers the motors of the axes of the picking robot. The supply voltage can, but does not have to, correspond to the voltage of a higher-level power grid. The supply voltage can be a voltage derived from the voltage of a higher-level power grid.
[0022] The method is explained below using an embodiment with a characteristic curve. The measured voltage value is used by the processing device to evaluate a characteristic curve. The characteristic curve represents a relationship between the supply voltage and a respective associated maximum path speed. The path speed should not exceed the maximum path speed for a specific supply voltage. The concrete embodiment of the characteristic curve is not important for the invention. The characteristic curve can, for example, be a mathematical function which specifies a maximum path speed as a function of the supply voltage. The characteristic curve can also be shown graphically. In order to reduce the calculation effort, the characteristic curve can, in particular, be presented as a table of values.The invention therefore determines the maximum path speed that can be achieved with the determined supply voltage. The maximum path speed can be above zero even in the event of significant voltage drops, for example voltage drops below 50% of a nominal voltage, in order to prevent the removal robot from coming to a standstill. There is a limit value in the supply voltage, which can also be found in the characteristic curve, with the maximum path speed above the limit value being constant. The limit value can, for example, be a nominal voltage of the supply voltage that supplies the robot. Alternatively, the limit value can also be below the nominal voltage. If the measured supply voltage is above the limit value, the maximum path speed is constant. This means that the path speed is not adjusted for supply voltages above the limit value.The path speed is adjusted so that it corresponds to or is lower than the maximum path speed for the detected supply voltage. This prevents the removal robot from coming to a standstill.
[0023] In a next step, the processing device adapts the web speed according to the characteristic curve or according to the evaluation of the characteristic curve, so that the web speed corresponds to or is lower than the maximum web speed for the detected supply voltage. If the supply voltage is equal to or higher than a nominal voltage, the specified web speed remains unchanged, as in this case no adjustment is necessary. If the supply voltage falls below the nominal voltage, a change in the web speed may be necessary if the specified web speed is above the maximum web speed according to the characteristic curve. The nominal voltage can in particular be an intermediate circuit voltage for which the intermediate circuit is designed with knowledge of the voltage of the higher-level power grid.By reducing the path speed, a further drop in the supply voltage due to reduced motor power can be avoided, while at the same time it is possible for the removal robot to remain in operation. If, for example, a servo motor is used, an output stage connected in front of the motor can basically transfer energy in both directions. When a load is reduced or when the corresponding axis is braked, the motor becomes a generator and energy flows via the motor through the output stage back to the supply, for example into the intermediate circuit. The energy introduced in this way can stabilize the supply voltage. Any voltage drop can therefore be reduced or stopped by reducing the path speed. The processing device determines the next positions along the path or the next positions along the path that have been adjusted, in particular reduced.of the path, the speed for each of the axes to reach the next position. This can be done on the basis of coordinate transformations, for example using the Denavit-Hartenberg transformation. In addition to the speed, the acceleration for each of the axes can also be determined. The speed can be an angular speed. The acceleration can be an angular acceleration. Boundary conditions for the speed and acceleration in the individual axes and / or for the handling element as well as boundary conditions for jerky movements can be taken into account. For example, the reduction in path speed can be carried out mathematically by stretching the time axis. If, for example, the path speed is to be reduced by 50 percent due to a voltage drop, the time axis is stretched by a factor of 2.In this case, the time required to travel a constant distance would be double the original estimate, halving the orbital speed. The acceleration, for example, can be reduced to a quarter.
[0024] Due to curvilinear movements of the handling device, among other things along individual axes, it is generally not possible to implement a reduced path speed by reducing the speed of each of the individual axes by the same percentage without deviating from the specified path. For example, a two-axis removal robot with a linear axis and a rotational axis is conceivable. In this case, the speed of the handling element depends non-linearly on the position of the linear axis or on the distance of the handling element from the rotational axis. In other words: with a constant angular speed around a rotational axis, the path speed of the handling element varies depending on the radius or distance from the rotational axis. It is therefore necessary to coordinate the speeds of the individual axes in order not to deviate from the specified path and to ensure path fidelity.Path fidelity means that the handling element essentially adheres to the originally defined path within the movement tolerances of the picking robot and does not deviate from it despite adjustments to the path speed. Otherwise, this could endanger nearby objects or persons if the handling element deviates from the path.
[0025] In a further step, the determined speed for each of the axes is transferred to at least one axis control device for controlling and / or regulating the motors, which then controls the motors accordingly. The motors can be, for example, electric motors, preferably three-phase motors or direct current motors. For example, the motors can be linear motors or servomotors. Servo controllers can be used together with servomotors. Servo controllers contain at least one power stage with power transistors, the associated drivers and a unit for controlling the power switches (transistors). PWM (pulse width modulation) signals can be used for this purpose, for example. A servo controller can also receive setpoints from a higher-level microcontroller, a higher-level processor or from the axis control device.Depending on the architecture, the setpoint can be a voltage, current, speed, or position setpoint. The maximum power of a servo motor and, depending on the design, also the maximum speed depend on the available supply voltage. The device and method according to the invention thus make it possible to prevent the multi-axis picking robot from stopping even in the event of supply voltage drops and to ensure path fidelity.
[0026] Preferably, the path speed is adjusted by means of a control loop with a controller, wherein the control loop regulates the path speed in such a way that the supply voltage does not fall below the limit value. In this embodiment, no characteristic curve is necessary because the control loop can regulate the path speed without knowledge of the characteristic curve in such a way that the supply voltage is stabilized. The reference variable of the control loop is the limit value of the supply voltage, the fed-back measured variable is the supply voltage, and the manipulated variable is the path speed. The controller can be, for example, a P, a PD, or a PID controller.
[0027] In one embodiment of the invention, the characteristic curve below the limit value can have a linear relationship between supply voltage and maximum path speed.
[0028] The linear relationship is determined by two points: first, by the supply voltage limit and the maximum path speed at the limit, and second, by the supply voltage at which the maximum path speed drops to zero. At least in the interval between these two points, there is a linear relationship between the maximum path speed and the supply voltage.
[0029] In a preferred embodiment, the supply voltage is an intermediate circuit voltage of an intermediate circuit, wherein the intermediate circuit is separated from a higher-level power grid, for example by means of a rectifier. The intermediate circuit is an electrical device that electrically couples several electrical networks at an intermediate current or voltage level, for example via rectifiers or inverters. The rectifier converts alternating voltage into direct voltage. In this case, the intermediate circuit is also referred to as a direct voltage intermediate circuit. The rectifier can be unidirectional or bidirectional, for example. The rectifier can be passive or active. A bridge rectifier is an example of a passive unidirectional AC / DC rectifier.In contrast to passive rectifiers, the output voltage of active rectifiers is usually regulated, often to a higher voltage level than with passive rectification. The intermediate circuit can contain a capacitor as an energy store, for example at least one capacitor or several capacitors can be provided. The energy stored in the capacitor can cover short-term power or voltage drops in the higher-level power grid. The intermediate circuit is fed, for example, by a higher-level power grid and in turn supplies the removal robot or at least one or all of the motors. Especially in unstable grids, the use of one or more intermediate circuits can improve the stability of the supply and thus of the entire system. It is therefore advantageous not to have to monitor the voltage of the higher-level power grid.to measure, but to use the intermediate circuit voltage to adjust the web speed. For example, the higher-level power grid can supply a rectifier via which all the motors are supplied with power. In this case, all the motors are supplied via the same intermediate circuit. Alternatively, several rectifiers can be supplied by the higher-level power grid, with one or more motors being supplied with power via each rectifier. In this case, the motors are supplied via several intermediate circuits. The measuring device can measure each intermediate circuit voltage of the several intermediate circuits. Preferably, the minimum of the measured intermediate circuit voltages is determined and used to evaluate the characteristic curve in order to adjust the web speed. Alternatively, a separate characteristic curve can be provided for each intermediate circuit.This means that each characteristic curve can be evaluated with the respective intermediate circuit voltage, with each evaluation leading to a maximum path speed. The minimum of the determined maximum path speeds is then used to adjust the speeds of the axes. The measuring device can be part of one rectifier or part of each rectifier. The rectifier(s) can be designed to measure the intermediate circuit voltage and provide this measured value. The measuring device can therefore already be implemented by the rectifier(s).
[0030] If, for example, servo motors are used as motors, an output stage connected in front of the motor can basically transfer energy in both directions. When a load is reduced or when the corresponding axis is braked, the servo motor becomes a generator and energy flows via the servo motor through the output stage back into the DC link. The energy introduced in this way can stabilize the supply voltage or the DC link for a short time. Any voltage drop can be reduced or stopped. The energy introduced via the motor can increase the DC link voltage to higher values than would correspond to the higher-level power grid. The method is therefore also suitable for actively stabilizing the supply voltage by feeding energy from the motors or the load back into the DC link.
[0031] The supply voltage is preferably filtered, in particular averaged, during detection. The supply voltage can be a direct voltage or an alternating voltage, for example. The instantaneous value of the supply voltage can be subject to fluctuation or oscillation at a frequency that is not relevant for the picking robot or the motors. Averaging or filtering the supply voltage can therefore improve the stability of the control of the picking robot. The filter can be implemented digitally or analogically, for example. The filter can be a low-pass filter and / or a notch filter and / or a band-pass filter. Alternatively or additionally, a filter with a predictor can be used which extrapolates the further course of the supply voltage based on the current value and / or past values.The filter can, for example, be a combination of a notch filter and a low-pass filter.
[0032] Preferably, a control loop with a controller is provided to adjust the path speed, wherein the control loop controls the path speed such that the supply voltage does not fall below the limit value. The control loop does not require a characteristic curve, since without knowledge of the characteristic curve, the path speed can be controlled such that the supply voltage does not fall below the limit value. The controller can be part of the processing device or part of the axis control unit. Alternatively, the controller can be implemented separately.
[0033] In one embodiment, a single axis control device controls all motors. This means that only a single axis control device is necessary.
[0034] In another embodiment, each axis control device controls exactly one of the motors. The device thus has a separate axis control device for each motor.
[0035] Each motor is preferably connected to an output stage, the output stage being controlled by an axis control device in order to open and / or close-loop control the motor. As described above, a single axis control device can be provided for all motors or one axis control device can be provided for each motor. A power stage is the last electronic stage which amplifies the signal if necessary before the signal reaches the load or the motors. The power stage can be an inverter or a rectifier, for example, or at least have an electrical switch, for example a transistor. The measuring device can be part of the power stages in that the supply voltage or the intermediate circuit voltage is detected by the power stages.
[0036] The measuring device can have a filter, for example a digital or analog filter. The supply voltage is preferably filtered, in particular averaged, during detection. The supply voltage can be, for example, a direct voltage or an alternating voltage. The instantaneous value of the supply voltage can be subject to fluctuation or oscillation that is irrelevant to the picking robot or the motors. Averaging or filtering the supply voltage can therefore improve the stability of the picking robot's control system.
[0037] The filter can be a low-pass filter and / or a notch filter and / or a bandpass filter. Alternatively or additionally, a filter with a predictor can be used, which extrapolates the further course of the supply voltage based on the current value and / or past values. Multiple filters can also be used together. For example, a notch filter can be used together with a low-pass filter. The use of a filter can improve the stability of the method.
[0038] The invention generally relates to a method and a device for controlling the movement of a handling element of a removal robot along a predetermined path at a location-dependent path speed, in which the required power is adapted to the power provided by a supply, for example by a higher-level power grid. For this purpose, the instantaneous power consumption can be determined and compared with a maximum available power or supply voltage. The instantaneous power consumption can be adapted to the available power by reducing the path speed accordingly. Alternatively, the available power can be determined and an expected power consumption can be determined.If the expected power consumption exceeds the available power (for which the supply voltage can be a measure), the path speed of the handling element can be adjusted such that the expected power consumption does not exceed the available power. In general, the power consumption and thus also the expected power consumption when moving the handling element along the next segment and / or to the next position along the path depend on at least one or more of the following parameters:
[0039] - Path speed of the handling element: The higher the path speed, the higher the power consumption is generally. If the power consumption is too high, the supply voltage typically drops. By reducing the path speed, the power consumption of the removal robot can be reduced. In the event of a voltage drop, which is usually caused by insufficient available power compared to the power requirement, the power consumption can be reduced to such an extent that the handling device does not have to be stopped completely and path fidelity is guaranteed.
[0040] - Acceleration of the handling element : If the handling element is accelerated to a higher speed , an increased power consumption is to be expected .
[0041] - Positions of the axes: The individual axes are linked to each other via the handling element, so the power consumption of the individual motors on the axes depends on the position of the axes. For example, the torque on an axis depends on the distance from the axis. The position of the handling element in relation to gravity can also influence power consumption.
[0042] - Load on the handling element, in particular the mass of a component gripped by the handling device: The mass of the handling element itself, as well as the mass of a component gripped or grasped by the handling element, influences the power consumption.
[0043] - Power consumption of the handling element, in particular of an end effector: If the handling element has, for example, a component for gripping or a tool such as a drill, the handling element itself can also consume power.
[0044] This method and an associated device are set forth in the following embodiments.
[0045] 1 . Method for controlling the movement of a handling element of a picking robot along a predetermined path with a location-dependent path speed, wherein the picking robot has several axes and a motor for each axis, comprising the following steps:
[0046] - Determining the next positions of the axes to move to the next position of the handling element along the path,
[0047] - Determine available power;
[0048] - Determining the expected power consumption of the picking robot to move to the next position along the path;
[0049] - Compare the available power with the expected power consumption;
[0050] - adjusting the path speed according to the comparison, whereby the path speed is adjusted in such a way that the expected power consumption is less than or equal to the available power; and
[0051] - Determining a speed for each of the axes to assume the next position as a function of the determined next positions of the axes and the adjusted path speed;
[0052] - Control and / or regulate the motors according to the determined speeds for each of the axes.
[0053] 2. Method according to embodiment 1, characterized in that the expected power consumption is a function of at least one or more of the following parameters:
[0054] - Path speed of the handling element
[0055] - an acceleration of the handling element - positions of the axes
[0056] - a load on the handling element, in particular a mass of a component gripped by the handling device
[0057] - further power consumption of the handling element, in particular of an end effector
[0058] 3. Method according to embodiment 2, characterized in that a supply voltage is detected to detect the available power, wherein the supply voltage is proportional to the available power.
[0059] 4. Method according to one of the preceding embodiments, characterized in that the available power is provided by an intermediate circuit, wherein the intermediate circuit is separated from a higher-level power network, for example by means of a rectifier.
[0060] 5. Method according to one of the embodiments 3 or 4, characterized in that the supply voltage is filtered, in particular averaged, during detection.
[0061] 6 . Device for controlling a handling element of a removal robot along a predetermined path with a location-dependent path speed, wherein the removal robot has several axes and a motor for each axis, comprising:
[0062] - a measuring device for determining available power;
[0063] - a processing device, preferably a processor, configured to receive the determined available power from the measuring device, to determine next positions of the axes for moving to a next position of the handling element along the path, and configured to determine an available power and to determine an expected power consumption of the removal robot, further configured to compare the available power with the expected power consumption, and further configured to adjust the path speed according to the comparison, wherein the path speed is adjusted such that the expected power consumption is less than or equal to the available power, and to determine the speed for each of the axes for assuming the next position depending on the determined next positions of the axes and the adjusted path speed; and
[0064] - at least one axis control device for controlling and / or regulating the motors according to the determined speed for each of the axes.
[0065] 7. Device according to embodiment 6, characterized in that a single axis control device controls all motors.
[0066] 8. Device according to embodiment 6, characterized in that each axis control device controls exactly one of the motors.
[0067] 9. Device according to one of the preceding embodiments, characterized in that each motor is connected to a respective output stage, wherein the output stage is controlled by an axis control device in order to control and / or regulate the motor.
[0068] 10. Device according to one of the preceding embodiments, characterized in that the measuring device has a filter, for example a digital filter, preferably an analog filter.
[0069] 11. Device according to embodiment 10, characterized in that the filter is a low-pass filter and / or a notch filter (="Kerbf ilter") and / or a band-pass filter.
[0070] The present invention will be further explained with reference to embodiments shown in the drawings, to which, however, it is not intended to be limited.
[0071] Fig. 1 shows a schematic representation of a device for controlling a handling element of a removal robot with an axis control device.
[0072] Fig. 2 shows a schematic representation of a device for controlling a handling element of a removal robot with several axis control devices.
[0073] Fig . 3 shows a schematic representation of the implementation of the measuring device when the motors are supplied by an intermediate circuit .
[0074] Fig. 4 shows a schematic representation of the implementation of the measuring device when the motors are supplied by several intermediate circuits.
[0075] Fig. 5 shows a schematic representation of a program flow for controlling a removal robot with multiple axes.
[0076] Fig. 6 shows a schematic representation of a program flow for controlling a removal robot with adjustment of the path speed depending on the supply voltage.
[0077] Fig. 7 shows schematically a removal robot with three axes and a gripper.
[0078] Fig. 1 shows a device 1 for controlling a handling element 2 of a removal robot 21 (see Fig. 7) along a predetermined path 25 with a location-dependent path speed 26 (see Fig. 7), wherein the removal robot 21 has a plurality of axes 3 and a motor 4 for each axis 3. In this embodiment, the removal robot 21 has three axes 3 and three motors 4. A measuring device 5 is provided which detects a supply voltage 13. The measuring device 5 has a digital filter, wherein the digital filter is preferably a notch filter. Furthermore, the supply voltage 13 is averaged during detection. Furthermore, a processing device 6 is provided, wherein the processing device 6 is a processor 7. The processor 7 determines the next positions of the axes 3 for moving to a next position of the handling element 2 along the path.The processor 7 receives the measured value of the measured supply voltage 13 from the measuring device 5 and is set up to evaluate a characteristic curve 8 (see Fig. 6) using the detected supply voltage 13 (see Fig. 6), the characteristic curve 8 indicating a relationship between the supply voltage 13 and the maximum path speed. The processor 7 is further set up to adapt the path speed 26 in accordance with the characteristic curve 8, so that the path speed 26 corresponds to or is lower than the maximum path speed for the detected supply voltage, and to determine the speed for each of the axes 3 to assume the next position as a function of the determined next positions of the axes 3 and the adjusted path speed. An axis control device 9 is set up to control and / or regulate the motors 4 in accordance with the determined speed for each of the axes 3.For this purpose, the processor 7 transmits the determined speeds to the axis control device 9. Three output stages 10 are provided, each connected to a motor 4. The output stages 10 are controlled by the axis control device 9 in order to control and / or regulate the respective motor 4. In this embodiment, a single axis control device 9 controls all motors 4. Depending on the architecture, the axis control device can specify target positions, target speeds, or target voltages.
[0079] In contrast to Fig. 1, Fig. 2 shows three axis control devices 9, each axis control device 9 controlling one of the three motors 4. Each axis control device 9 thus controls exactly one motor 4. In this exemplary embodiment, the processing device 6 is also the controller 20. The controller 20 is part of a control loop which regulates the path speed 26 in such a way that the supply voltage (13) does not fall below the limit value (16). In this exemplary embodiment, no characteristic curve 16 is stored.
[0080] Fig. 3 shows a higher-level power network 11, through which an alternating voltage is provided. By means of a rectifier 12, the alternating voltage provided by the higher-level power network 11 is converted into a direct voltage. The rectifier 12 thus separates an intermediate circuit 18 from the higher-level power network 11. A capacitor 17 is provided in the intermediate circuit 18. By means of the capacitor 17, electrical energy can be stored in the intermediate circuit 18, which can cover short-term power and / or voltage drops from the higher-level power network 11. Three output stages 10 are provided, each of which is connected to a motor 4. The output stages 10 are controlled by an axis control device 9 (not shown in Fig. 3, see Fig. 1) in order to control and / or regulate the respective motor 4. The output stages 10 and thus the motors 4 are supplied by means of the direct voltage from the intermediate circuit 18.The output stages 10 and thus also the motors 4 are therefore supplied by a single intermediate circuit 18, which is separated from the higher-level power supply 11 by the rectifier 12. The measuring device 5 is configured to measure the intermediate circuit voltage 19 of this intermediate circuit 18, wherein the intermediate circuit voltage 19 is the supply voltage 13.
[0081] Fig. 4 shows a higher-level power network 11 which provides an alternating voltage. The alternating voltage is converted to direct voltage by means of rectifiers 12. Three servo controllers 14 are provided, each of which is connected to a motor 4. The motors 4 are servo motors 15. The servo controllers 14 are controlled by an axis control device 9 (not shown in Fig. 4, see Fig. 1) in order to control and / or regulate the respective servo motor 15. The servo controllers 14 and thus the servo motors 15 are each supplied with direct voltage from a rectifier 12. The servo controllers and thus also the servo motors 15 are therefore each supplied by an intermediate circuit 18 (see Fig. 3), which is separated from the higher-level power network 11 by a rectifier 12.Each intermediate circuit 18 contains a capacitor 17, each having a corresponding capacitance to cover short-term voltage dips and / or power peaks. The measuring device 5 is configured to measure each intermediate circuit voltage 19 of the intermediate circuits 18. A minimum of the measured intermediate circuit voltages 19 is determined and further used for comparison with the characteristic curve 8 or for further adjustment of the track speed 26.
[0082] According to Fig. 5, a picking robot 21 can be controlled by means of a user program 101 that is implemented on a processing device 6 (see Fig. 1). The user program 101 contains information about the geometry of the picking robot 21 and the environment of the picking robot 21, as well as boundary conditions for speed and acceleration, boundary conditions for jerky movements (English "jerk constraints") and other basic data relating to the picking robot 21. The stored boundary conditions or limits must not be exceeded at any time. These limits cannot be changed or overwritten during operation. In a path planning block 102, the path is planned accordingly and the path is divided into segments that are described by polynomials s(t). The polynomials s(t) describe the position of the handling element as a function of time t.In the block Path Evaluation 103 the polynomials s (t) are evaluated at specific times.
[0083] The evaluation of the polynomials can be written in the form s ( t ) = n c n t n be carried out, where c n are constants. Typically, the trajectory is approximated by a polynomial of at least third order (n=3). After evaluating the polynomials at a time t, the polynomials are evaluated at a next time t+T c evaluated, where T cis a (positive) cycle time or a time increment. This results in the next (time-dependent) positions of the handling element 2, which are transformed into the coordinates of the axes 3 of the removal robot 21 by a coordinate transformation 104. The determined setpoints are transmitted to an axis control device 9 (see Figure 1), which controls the motors 4 (see Figure 1) accordingly and therefore transmits the determined setpoints to the axes 3. The removal robot 21 can have N axes 3, where N is an integer greater than one. The axes 3 or the motors 4 of the axes 3 are supplied with voltage.
[0084] Fig. 6 shows an implementation of the method according to the invention with the control shown in Fig. 5. A measuring device 5 (see Fig. 1) measures the supply voltage 13 in a voltage measurement block 105 and forwards the measured value to a processing device 6 (see Fig. 1). The measured supply voltage 13 is filtered in a filtering block 106. In an evaluation block 107, a characteristic curve 8 is evaluated using the determined measured value of the supply voltage 13. Alternatively, a controller 20 could be located at this point, which compares the supply voltage 13 with the limit value 16 and, if the supply voltage falls below the limit value, adjusts or reduces the path speed 26 accordingly. The characteristic curve 8 shown is a graphical representation of a mathematical function. The characteristic curve 8 shown is also stored as a table of values.For this purpose, the maximum path speed that can be achieved with the determined supply voltage 13 is determined. The characteristic curve 8 indicates a relationship between the supply voltage 13 and the maximum path speed. The characteristic curve 8 has a limit value 16 in the supply voltage 13, whereby the maximum path speed is constant above the limit value. Below the limit value 16, the characteristic curve shows a linear relationship between the supply voltage 13 and the maximum path speed. By evaluating the characteristic curve 8 using the supply voltage 13, a reduction value for the relative speed reduction is determined. The determined reduction value lies between 0% and 100% and is taken into account by scaling the time axis in the polynomial calculation for the further control of the removal robot 21.For example, a reduction value of 50% means that the time base for the polynomial calculation is 50% of the normal cycle time T. c is incremented . With a reduction value of 50%, a scaled time period T ' would be twice as long as a nominal time period T ( corresponding to T ' = T / 0 . 5 =2 *T ) . A program block calculation of the time increment T x 108 ensures that the determination of the adjusted time increment T x taking into account the currently valid limit values. Tx lies between 0 and the original time increment T c . The adjusted time increment T x is transferred to the block Path Evaluation 103, where it replaces the original time increment T c and is therefore included in the determination or calculation of the axis speeds.
[0085] Fig. 7 shows a schematic diagram of a removal robot 21 with three axes 3 and a handling element 2, which is a gripper 23. The gripper 23 is moved along the path 23. The path P(t) 25 contains, in addition to the information about the positions P, further information about the time sequence of the positions P(t) along the path 23. Thus, the path 25 also contains information about the path speed v(t) 26 along the path 25. The path speed 26 of the robot runs tangentially to the path 24. In order to adapt or reduce the path speed 26, the absolute value of the path speed 26 is determined. The adaptation is carried out in such a way that the path speed 26 or its absolute value corresponds to or is lower than the maximum path speed for the detected supply voltage.
Claims
Claims:
1. Method for controlling the movement of a handling element (2) of a removal robot (21) along a predetermined path with a location-dependent path speed (26), wherein the removal robot (21) has several axes (3) and a motor (4) for each axis (3), comprising the following steps: - Determining the next positions of the axes (3) for moving to a next position of the handling element (2) along the path, - detecting a supply voltage (13); - adjusting, in particular reducing, the path speed (26) in the event of a limit value (16) of the detected supply voltage (13) being undershot; and - determining a speed for each of the axes (3) for assuming the next position as a function of the determined next positions of the axes (3) and the adjusted path speed (26); - Controlling and / or regulating the motors (4) according to the determined speeds for each of the axes (3).
2. Method according to claim 1, characterized in that the adjustment of the web speed (26) is carried out by means of a control loop with a controller (20), wherein the control loop regulates the web speed in such a way that the supply voltage (13) does not fall below the limit value (16).
3. Method according to claim 1, characterized by the further step: - Evaluating a characteristic curve (8) by means of the detected supply voltage, wherein the characteristic curve (8) indicates a relationship between supply voltage (13) and maximum path speed and has the limit value (16) in the supply voltage, wherein the adjustment of the path speed (26) takes place according to the characteristic curve (8) so that the path speed (26) corresponds to or is lower than the maximum path speed for the detected supply voltage.
4. Method according to claim 3, characterized in that the characteristic curve (8) below the limit value (16) has a linear relationship between supply voltage (13) and maximum web speed.
5. Method according to one of the preceding claims, characterized in that the supply voltage (13) is an intermediate circuit voltage (19) of an intermediate circuit (18), wherein the intermediate circuit (18) is separated from a higher-level power network (11), for example by means of a rectifier (12).
6. Method according to one of the preceding claims, characterized in that the supply voltage (13) is filtered, in particular averaged, during detection.
7. Device (1) for controlling a handling element (2) of a removal robot (21) along a predetermined path (25) with a location-dependent path speed (26), wherein the removal robot has several axes (3) and a motor (4) for each axis (3), comprising: - a measuring device (5) for detecting a supply voltage (13); - a processing device (6), preferably a processor (7), configured to receive the detected supply voltage (13) from the measuring device (5), to determine the next positions of the axes (3) for moving to a next position of the handling element (2) along the path (25), further configured to adjust, in particular reduce, the path speed (26) in the event of a limit value (16) of the detected supply voltage (13) being undershot, and to determine the speed for each of the axes (3) for assuming the next position depending on the determined next positions of the axes (3) and the adjusted path speed; and - at least one axis control device (9) for controlling and / or regulating the motors (4) according to the determined speed for each of the axes (3).
8. Device according to claim 7, characterized in that a control circuit with a controller (20) is provided for adjusting the web speed (26), wherein the control circuit regulates the web speed (26) in such a way that the supply voltage (13) does not fall below the limit value (16).
9. Device according to claim 7, characterized in that the processing device (6) is set up to evaluate a characteristic curve (8) by means of the detected supply voltage (13), wherein the characteristic curve (8) indicates a relationship between supply voltage (13) and web speed, wherein the adaptation of the web speed (26) takes place in accordance with the characteristic curve (8).
10. Device according to one of claims 7 to 9, characterized in that a single axis control device (9) controls all motors (4).
11. Device according to one of claims 7 to 9, characterized in that each axis control device (9) controls exactly one of the motors (4).
12. Device according to one of claims 7 to 11, characterized in that each motor (4) is connected to a respective output stage (10), wherein the output stage (10) is controlled by an axis control device (9) in order to control and / or regulate the motor (4).
13. Device (2) according to one of claims 7 to 12, characterized in that the measuring device (5) has a filter, for example a digital filter, preferably an analog filter.
14. Device (2) according to claim 13, characterized in that the filter is a low-pass filter and / or a notch filter (="Kerbf ilter") and / or a band-pass filter.