• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    The invention relates to a method for pressing a workpiece (4) with a predetermined pressing force by means of a forming tool (3), which is coupled via a spindle drive (6) with an electric motor (2), wherein the spindle drive (6), the rotational movement of a drive shaft (8) of the electric motor (2) converts into a translatory movement of the forming tool (3). The method comprises the following method steps: - accelerating the electric motor (2) in the direction of rotation to a predetermined maximum speed; - Operating the electric motor (2) in maximum speed until the drive shaft (8) of the electric motor (2) has completed a predetermined number of revolutions; - Reduce the speed of the electric motor (2) to a predetermined reduced speed; Operating the electric motor (2) at a reduced speed until a pressure force rise which exceeds a predetermined threshold value is detected by a measuring unit (12) connected downstream of the electric motor (2); - Forming the workpiece (4) under constant detection of the pressing force by means of the measuring unit (12) until the predetermined pressing force is reached.
    公开号:AT518684A1
    申请号:T50502/2016
    申请日:2016-06-01
    公开日:2017-12-15
    发明作者:Brunner Matthias；Ing Dr Tobias Glück Dipl；Ing August Gründl Dipl；Ing Dr Andreas Kugi Dipl
    申请人:Stiwa Holding Gmbh；
    IPC主号:
    专利说明:

    The invention relates to a method for pressing a workpiece with a predetermined pressing force.
    Various methods for pressing a workpiece are known from the prior art. The methods known from the prior art relate in particular to production systems in which workpieces are to be pressed with a predetermined pressing force. In this case, the workpieces must be pressed with a predetermined pressing force, wherein the actual amount of pressing force has only a small tolerance range.
    The methods known from the prior art have the disadvantage that in order to achieve the required pressing force while maintaining the required tolerance range, the pressing speed must be selected correspondingly low, to suppress the pressing force falsifying dynamic effects which occur due to the inertia of the individual components of the drive train ,
    The object of the present invention was to overcome the disadvantages of the prior art and to provide a method which has an increased process speed while maintaining process accuracy.
    This object is achieved by an apparatus and a method according to claim 1.
    According to the invention, a method for pressing a workpiece with a predetermined pressing force by means of a forming tool, which is coupled via a Ge threaded operation with an electric motor, is provided. A screw drive converts the rotational movement of a drive shaft of the electric motor into a translational movement of the forming tool. The electric motor is controlled by a control. The method comprises the following method steps: - accelerating the electric motor in the direction of rotation to a predetermined maximum speed, whereby the forming tool is moved toward the workpiece; - Operating the electric motor in maximum speed until the drive shaft of the electric motor has completed a predetermined number of spindle revolutions or the forming tool has reached a predetermined position, wherein during this step, the forming tool is moved freely on the workpiece without touching it; - Reduce the speed of the electric motor to a predetermined reduced speed; Operating the electric motor at a reduced speed until a measuring force increase is detected by a measuring unit downstream of the electric motor which exceeds a predetermined threshold value or an increase in torque is detected at the electric motor which exceeds a predetermined threshold value, wherein the increase in pressing force occurs when the forming tool is in contact with the workpiece to be formed comes; - Forming the workpiece under constant detection of the pressing force by means of the measuring unit or the torque on the electric motor until the predetermined pressing force is reached.
    An advantage of the method according to the invention is that the method is divided into a very wide variety of method steps, with the electric motor having a different speed in the individual method steps. By this measure it is achieved that the pressing time can be shortened as possible and at the same time the required pressing force can be achieved as accurately as possible. In particular, during operation of the electric motor in a predetermined maximum speed as fast as possible deliver the forming tool is guaranteed. In this step, the forming tool is moved in the direction of the workpiece, taking care that the forming tool is moved freely on the workpiece and the forming tool not yet
    Workpiece abuts. Only in the subsequent process step in which the electric motor is operated at reduced speed is provided that the forming tool comes to rest on the workpiece to be machined. As an alternative to a spindle drive, it is also possible to use another means which is suitable for converting the rotary movement of the electric motor into a translatory movement of the shaping tool. The predetermined position of the forming tool can be detected, for example, by means of a linear measuring unit. The torque increase in the electric motor can be detected, for example, by detecting the motor current in the electric motor.
    Furthermore, it may be expedient if, after the detection of the press force increase, the electric motor is braked to a predetermined minimum speed. The advantage here is that by braking the electric motor to minimum speed excessive pressing and thus handing over the pressing force can be prevented.
    Furthermore, it can be provided that the electric motor is operated at minimum speed for a predetermined or predeterminable period of time until oscillations that occur in the drive system due to the deceleration process from the reduced rotational speed to the minimum rotational speed have largely disappeared. The advantage here is that can be achieved by operating the electric motor in the minimum speed in a predetermined period of time that the drive system can swing out and thus there is no distortion of the measured pressing force on the measuring unit. In extreme cases, it may be necessary to select a complete standstill as the minimum speed. The oscillations that have to die out are due to the mass inertia or the inertial forces of the individual components in the drive system and due to the abrupt deceleration maneuver.
    In addition, it can be provided that, during the forming of the workpiece, the control of the electric motor is predetermined by the control on the basis of the pressing force measured in the measuring unit. After expiration of this predetermined time period in which the sensor signal is corrupted, it is possible to switch over to pressing force control in order to be able to achieve the required pressing force.
    Also advantageous is an expression according to which it can be provided that the reduced rotational speed is between 0.1% and 100%, in particular between 0.5% and 99%, preferably between 50% and 80% of the maximum rotational speed. The advantage here is that during operation of the electric motor in a reduced speed, a pressing force which exceeds a predetermined threshold, can be detected and due to the reduced speed then sufficient time remains to lower the speed further and set the required pressing force.
    According to a development, it is possible that directly after the detection of the press force increase the further control of the electric motor is set by the control based on the pressing force, wherein after the detection of the pressing force increase, the electric motor is decelerated to a predetermined minimum speed and in an initial period during the braking process the pressing force detected in the measuring unit is superimposed by a pressing force based on a model calculation, and after the initial period, the pressing force detected by the measuring unit serves as input for the control. This alternative variant has the advantage that the process time can be further shortened and optimized. By blending the detected pressing force with a pressing force based on a minor computation, the measurement error that occurs due to the oscillation of the system after the deceleration of the electric motor can be compensated.
    Furthermore, it may be expedient if in the model calculation, the inertia and / or the spring stiffness and / or the damping and the angular or linear accelerations of the individual components installed in the drive train is taken into account. The advantage here is that based on these values or on the basis of these state variables, the dynamic behavior of the drive train can be accurately calculated and thus a distortion of the measured pressing force during braking or when accelerating the electric motor can be compensated.
    In addition, it can be provided that the model calculation is adjusted on the basis of the respective previous cycles in an iterative learning process, wherein used to adapt the model calculation of the time course of the measured value of the torque in the measuring unit, and the engine torque and the associated rotation angle of the drive shaft in the electric motor becomes. The advantage here is that the drive method can be adjusted and improved during operation, which on the one hand, the accuracy can be increased to achieve the pressing force and beyond the process time can be further reduced.
    Furthermore, it can be provided that a disturbance observer, in particular a Kalman filter, is used for the model calculation, which is also regulated in the first step and only superimposed on the force detected in the measuring unit at a certain point in time. The advantage in this case is that such disturbance observer can estimate the actual actual force applied based on the manipulated variable and the sensor signals and the estimated external force can be specified to the scheme, whereby the accuracy in achieving the predetermined pressing force can be improved.
    It may also be provided to extend the control loop by a feedforward control for force and / or inertia compensation, should the dynamics of the lower-level controllers not be sufficient. The pilot controls can be derived from the mathematical models. It may be sufficient to use a much simplified model, such as a pure rigid body system, which takes into account only moments of inertia and no dynamic elements. Alternatively, a dynamic system as described in this document may be used for mathematical modeling.
    Furthermore, it can be provided that a piezoelectric sensor is used as the measuring unit, which is arranged to detect the pressing force in the region of the forming tool. The advantage here is that a piezo sensor on the one hand has a high accuracy and also has a very fast response.
    Furthermore, it can be provided that directly after the detection of the press force increase, the further control of the electric motor is predetermined by the control based on a setpoint trajectory of the press force value, wherein the speed profile is calculated in a feedforward control from the setpoint trajectory of the press force value. If a disturbance observer is used, the actual force can be estimated. By fading to this estimated force, noise can be faded out.
    Furthermore, it can be provided that, in a first phase after the detection of the press force increase, the press force value is estimated by means of a disturbance observer and that in a second phase after the detection of the press force increase, the press force is detected directly by the measuring unit and serves as input for the control. By specifying the press force value by means of the disturbance observer, vibrations or disturbances in the system can be filtered, so that no settling occurs in the control.
    After the vibrations have subsided, the torque actually measured at the measuring unit can then serve as the input value for the control.
    Furthermore, it can be provided that the transition between different rotational speeds of the individual method steps is predetermined such that no sudden increases in acceleration occur. By avoiding sudden increases in acceleration, the jolt that acts on the individual components of the press can be reduced and thereby the longevity of the press can be increased.
    The maximum speed to which the electric motor is accelerated need not necessarily correspond to the maximum possible speed of the electric motor. Rather, it is also possible that the maximum speed results from the process parameters and is a calculated value. The predetermined maximum speed can vary from one pressing process to the next.
    Furthermore, it can be provided that a third-order low-pass filter of the form RP (s) = kpp 3 is selected as the regulator. bfe)
    Furthermore, it can be provided that controller parameters can be set by means of a loop-shaping method.
    The threshold value of the pressing force or of the torque which is detected may be a predetermined or individually definable absolute value of the pressing force, for example in N, or the torque, for example in Nm.
    Alternatively, it is also possible that an absolute value of the pressing force or the torque is not specified as the threshold value, but that as a threshold value a predetermined or individually predeterminable press force increase per travel of the forming tool (wherein the travel can be measured directly on the forming tool, or via the Number of revolutions of the drive motor can be calculated) or torque increase per angular unit of the motor is specified. The threshold value of the press force increase can be defined approximately in N per mm travel or in N per ° rotation angle of the electric motor. The threshold value of the torque increase can be defined approximately in Nm per "rotation angle.
    In yet another embodiment, it is conceivable that a maximum change in the press force increase per travel of the forming tool (the travel can be measured directly on the forming tool, or calculated over the number of revolutions of the drive motor) or the torque increase per rotation angle unit of the motor is specified. The maximum change in the press force increase per rotation angle unit can be calculated, for example, by the first derivation of the function of the press force increase per travel path unit of the forming tool. This threshold value of the change in the torque increase can be defined approximately in .DELTA.Ν per Arnrn travel. The maximum change of the torque increase per rotation angle unit can be calculated, for example, by the first derivative of the function of the torque increase per rotation angle unit of the motor. This threshold value of the change in the torque increase can be defined approximately in ANm per A ° rotation angle.
    As a regulation in the sense of this document, a Zweifreiheitsgradekraftregelung be understood with subordinate engine control, a control loop with this scheme may also have additional pilot controls.
    Furthermore, it can be provided that a speed curve is calculated on the basis of the load characteristic and a desired desired trajectory for the external pressing force. This speed starts at the reduced speed and is transferred to standstill. This speed profile ensures that the external pressing force follows the desired setpoint trajectory sufficiently well. As a result, it is possible to compensate for the permanent control deviation with a linear controller Rf. If a disturbance observer is used, the estimated signal is regulated and blended to the measurement signal at the end of the trajectory. If the disturbance observer is not present because the quality of the measurement signal is sufficiently good, then the measurement signal is controlled directly and thus no cross-fading is performed.
    For a better understanding of the invention, this will be explained in more detail with reference to the following figures.
    In each case, in a highly simplified, schematic representation:
    Fig. 1 is a schematic representation of a possible construction of a press;
    FIG. 2 is a flow chart of a first control strategy for pressing a workpiece; FIG.
    Fig. 3 is a structural diagram of the mechanical model of the press;
    4 shows a force profile representation of the press;
    5 is a structural diagram of a control circuit for the force control;
    6 shows an exemplary controlled system of a force control;
    Fig. 7 is a flow chart of another control strategy for pressing a workpiece;
    FIG. 8 is a structural diagram of a control circuit with disturbance observer and load precontrol, force precontrol and inertia compensation; FIG.
    FIG. 9 shows a structural circuit diagram of a control loop with disturbance observer and force precontrol as well as inertia compensation; FIG.
    10 is a structural diagram of a control loop with Störgrößenbeobachter and force precontrol;
    11 is a structural diagram of a control loop with disturbance observer and load precontrol and force precontrol;
    12 is a structural diagram of a control circuit with load precontrol, force precontrol and inertia compensation;
    13 is a structural diagram of a control circuit with force precontrol and inertia compensation;
    14 is a structural diagram of a control circuit with force precontrol;
    15 is a structural diagram of a control circuit with load pre-control and
    Force pilot control.
    By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location.
    1 shows a schematic representation of a process press 1. The process press 1 comprises an electric motor 2, and a forming tool 3 coupled to the electric motor 2. The forming tool 3 can act on a workpiece 4 in order to be able to deform it. Such deformation can example, be an embossing. Furthermore, it is also conceivable that the workpiece 4 is bent for example by means of the forming tool 3. The forming process of the workpiece 4 can be automated. The forming tool 3 can have a wide variety of shapes.
    Furthermore, it can be provided that the electric motor 2 is designed as a servomotor. Such a servomotor may be, for example, a synchronous motor. In addition, it can be provided that the electric motor 2 is connected to a controller 5. Furthermore, it can be provided that a frequency converter is formed, which cooperates with the electric motor 2 and predetermines the rotational speed of the electric motor 2.
    As can further be seen from FIG. 1, it can be provided that a spindle drive 6 is coupled to the electric motor 2. Such a spindle drive 6 may be formed, for example, as a screw, preferably as a ball screw. A ball screw has the advantage that it has a low clearance. As a result, a high accuracy of the process press 1 can be achieved.
    By means of the spindle drive 6, the rotational movement of the electric motor 2 can be converted into a translational movement of the forming tool 3.
    Furthermore, it can optionally also be provided that a gearbox 7 is arranged between the spindle drive 6 and the electric motor 2, by means of which the speed of the drive shaft 8 of the electric motor 2 can be reduced.
    If a transmission 7 is provided in the drive train, then a spindle 9 of the spindle drive 6 is coupled to a transmission output shaft 11 arranged on the transmission output 10 and has the same rotational speed as this.
    If no gear 7 is provided in the drive train, then the spindle 9 of the spindle drive 6 is coupled to the drive shaft 8 of the electric motor 2 and has the same rotational speed as this.
    Furthermore, it is provided that between spindle drive 6 and forming tool 3, a measuring unit 12 is arranged, which is designed to detect the voltage applied to the forming tool 3 pressing force. The measuring unit 12 can be designed in particular as a force sensor or as a load cell. Preferably, it can be provided that the measuring unit 12 is designed as a piezoelectric sensor. The measuring unit 12 is coupled to the controller 5.
    Furthermore, it can be provided that a coupling 13 is provided for connecting the electric motor 2 and the transmission 6 or for connecting the transmission 7 and the spindle drive 6. The clutches 13 are used in particular for torque transmission between the individual components and are therefore arranged between the individual components.
    Furthermore, it can be provided that the spindle 9 of the spindle drive 6 is mounted on a bearing 14, which serves for receiving the introduced into the spindle 9 axial forces and radial forces. Furthermore, it can be provided that the spindle drive 6 comprises a threaded nut 15, which is coupled to the spindle 9 and converts the rotational movement of the spindle 9 into a translational movement of the threaded nut 15.
    With the threaded nut 15, a carriage 16 may be coupled, which can serve to receive the forming tool 3. In particular, it can be provided that the measuring unit 12 is arranged between carriage 16 and forming tool 3.
    In an embodiment variant, not shown, it can be provided that the measuring unit 12 is integrated in the carriage 16.
    It can preferably be provided that the forming tool 3 is detachably coupled to the carriage 16. It can thereby be achieved that different forming tools 3 can be coupled to the carriage 16 for different application requirements.
    Furthermore, it can be provided that the carriage 16 is guided on a guide rail 17.
    The general mode of operation of the process press 1 will now be explained with reference to FIG.
    The forming tool 3 is moved by means of the spindle drive 6 on the workpiece 4, wherein the spindle drive 6 is driven by the electric motor 2. In a first method step, the forming tool 3 is thereby moved freely onto the workpiece 4, care being taken that the forming tool 3 does not touch the workpiece 4. In other words, one can also speak of a delivery process.
    At the end of this Zustellvorganges a pressing surface 18 of the forming tool 3 comes into contact with the workpiece 4, whereby the force acting on the forming tool 3 increases abruptly. Subsequently, the forming tool 3 is pressed into the workpiece 4, whereby the workpiece 4 is deformed by means of the forming tool 3.
    It can be said that the pressing process is divided into two stages. The first stage is a delivery process in which the forming tool 3 is moved freely onto the workpiece 4 without, however, touching it.
    The second stage is a forming stage in which the pressing surface 18 of the forming tool 3 bears against the workpiece 4 and the workpiece 4 is deformed by means of the forming tool 3, wherein an increased torque must be applied to the drive shaft 8 of the electric motor 2.
    During the delivery process can be provided that the electric motor 2 is superimposed speed controlled until a predefined pressing force is exceeded or the impact of the forming tool 3 is detected on the workpiece 4 by means of a gradient method. In the forming stage, it can be provided that the electric motor 2 is superimposed torque-controlled, wherein the measured pressing force for controlling the electric motor 2 is used.
    In the forming stage, a predefined pressing force can be set by means of a cascaded two-degree-of-freedom control. This cascaded control consists of an internal speed control, a superimposed torque control or force control and a corresponding model-based feedforward control.
    The model-based feedforward control compensates for the occurring pressing force due to the load and the inertia of the drive. If the mechanical coupling between the electric motor 2 and the forming tool 3 is sufficiently rigid, then the pressing force detected at the measuring unit 12 can be used as a direct feedback variable for the torque control or force regulation.
    The difficulty with the control is to keep the process speed high and the press force within predetermined limits. If an ideal, interference-free route is assumed, a motor speed curve can be found, which makes it possible to set a desired pressing force.
    In the real application, however, occurring interference and measurement noise in the measurement unit 12 is to be expected.
    In order to achieve a defined pressing force while keeping the process speed as high as possible, the control strategies according to the invention have been developed.
    As long as the forming tool 3 is moved freely on the workpiece 4 and is not applied to this, is to be expected no significant increase in the actual force applied to the forming tool 3 pressing force. It therefore makes sense to specify a motor speed profile without additional torque control or force control directly in this forming stage. Only when the pressing surface 18 of the forming tool 3 contacts the workpiece 4, there is a rapid increase in the voltage applied to the forming tool 3 pressing force and the torque control or force control is active. In the forming stage, a motor speed profile is specified in which different speed levels are continuously connected to each other. This ensures that the mechanical components of the process press 1 are not unnecessarily strained and the excitation of vibrations in the system is kept low.
    The aim of the scheme is to regulate the force actually applied to the forming tool so that it reaches a defined value, also referred to as a predetermined pressing force.
    The actual force applied to the forming tool 3 pressing force is to be measured by means of the measuring unit 12 and serve as a feedback variable in the scheme. However, it should be mentioned that the pressing force measured in the measuring unit 12 only corresponds to the pressing force actually applied to the forming tool 3 when the forming tool 3 is not being accelerated or decelerated and therefore no dynamic effects due to the inertia of the individual components occur. In other words, the pressing force actually applied to the forming tool 3 can be accurately measured by the measuring unit 12 when the forming tool 3 is stationary or moving at a constant feed speed, this condition also having to last for a certain period of time, so that vibrations have already subsided.
    2 shows a flowchart of a schematic sequence of a first control strategy for pressing the workpiece 4.
    At the decision paths there is a plus (+) for condition is met. A minus (-) stands for condition is not met.
    In method step 1, the drive shaft 8 of the electric motor 2 is accelerated to maximum speed. In order to accelerate the electric motor 2 to maximum speed, a specific time profile of the angular velocity or a certain acceleration ramp can be predetermined on the basis of which the electric motor 2 is accelerated. In the query A is queried whether the drive shaft 8 of the electric motor 2 has already completed a predetermined number of spindle revolutions, or, consequently, how far the forming tool 3 has already been moved by means of the spindle drive 6 in its linear movement.
    The electric motor 2 is operated at maximum speed until reaching the predetermined number of spindle revolutions or achievement of the predetermined feed travel of the forming tool 3 in the interrogation A to fulfill the condition. The number of spindle revolutions which serves as a trigger for switching to method step 2 is selected as high as possible, but chosen so low that it is possible in all possible cases due to the tolerances that the pressing surface 18 of the forming tool 3 not during this process step on the workpiece 4 comes to the concern. During method step 1, it may be provided that the pressing force measured at measuring unit 12 is not interrogated or at least not included in the motor control.
    Subsequently, in method step 2, the electric motor 2 is operated at reduced speed. The reduced speed serves to ensure that sufficient time remains in the detection of a press force increase in the measuring unit 12 in order to reduce the engine speed or to switch to a force control. The rotational speed in the reduced speed is dependent on how fast the electric motor 2 can be braked and which travel the forming tool 3 can still be moved after placing on the workpiece 4. This maximum travel is also called offset. For example, if the intended press-in depth is very large, the reduced speed may have a high value and, for example, be approximately the same size as the maximum speed.
    The transition from maximum speed to reduced speed can also be carried out according to a predetermined time profile of the angular velocity. During operation of the electric motor 2 at a reduced speed, the measuring unit 12 is activated to be able to detect when the pressing surface 18 of the forming tool 3 comes into contact with the workpiece 4, thereby causing a sudden increase in the pressing force detected in the measuring unit 12. Query B determines whether the pressing force detected in the measuring unit 12 has reached a certain predefined threshold value and when the threshold value is reached, the method step 3 is initiated.
    Subsequently, in method step 3, a force control, as shown in the structural diagram of the control circuit in FIG. 5 with the controlled system in FIG. 6, is activated. By means of the force control, the electric motor 2 is controlled such that the predetermined pressing force is achieved.
    3 shows a structural diagram of the mechanical model of the process press 1. This serves as the basis for the modeling of the process press 1. The input variable of the model represents the engine torque Mm, which counteracts the friction torque Mrm of the drive. The motor moment of inertia is determined by 0m. The clutch 13 is modeled as a linear spring-mass-damper element. This is characterized by the spring constant Ck, the damping constant dk and the moment of inertia 0fc, wherein the moment of inertia on the input side or the output side is taken into account half each. The moment after the clutch 13, which acts as the drive torque of the spindle 9, is designated Msp. The friction losses are taken into account with the moment Mrs. With the moment of inertia of the spindle 9 is specified. The ball screw transforms the rotational movement of the spindle 9 in a translational movement of the carriage 16. The ratio of this transformation is denoted by ig. The measuring unit 12, which connects the carriage 16 with the mass mi and the forming tool 3 with the mass m2, is modeled with a linear spring-damper model with the spring constant cs and the damping constant ds.
    The position of the carriage 16 is indicated by si and the position of the forming tool 3 by S2. The transformed spindle torque causes the force Fa, which acts on the carriage 16. The force Fs indicates the measured value of the measuring unit 12 and Fext the external force occurring during pressing.
    4 shows an exemplary course of the external force over the course of the position of the forming tool 3. The exemplary profile of the external force can be determined by a test. This exemplary course is also referred to as a load characteristic.
    To enable a wide range of press applications and to ensure the ease of model matching, the load model of the specific applications is determined empirically. The aim is to metrologically record a characteristic which indicates the relationship between the external force Fext and the position of the forming tool 3 S2. For this purpose, the forming tool 3 at a constant speed, according to the application, so far moved to the workpiece 4 until a defined limit force is reached. The relationship thus determined between force and displacement is shown in FIG. 4 and corresponds to that of a nonlinear spring of the form Fext (S2) = k (S2) * S2 with the position-dependent spring stiffness k (S2). The characteristic is divided into two areas. While the forming tool 3 moves freely, there is no significant increase in force. For this process, Fext = ON is assumed. Only from the impact of the forming tool 3 on the workpiece 4, there is a noticeable increase in force. When this force increase Fext »Fs> Trigger is detected, the forming stage begins. The associated carriage position is called strigger.
    Fig. 5 shows a structural diagram of a control circuit for the force control, wherein the force controller is designed for the forming stage and is active in this.
    In some pressing operations, there may be occurrences that the curve of the pressing force has a very steep rise. In other words, the pressing force increases steeply with only slight movement of the forming tool 3. Therefore, it may be necessary for the forming die 3 to be brought to a standstill within a short distance to reach a predetermined value of the pressing force. Due to the inertia of the system or due to the inertia of a conventional control of the electric motor 2, however, there may be occurrences that the dynamics of the subordinate speed controller of the electric motor 2 is not sufficient for this braking maneuver.
    To circumvent this problem, not only force pre-control but also motor speed pre-control is used for inertia and load compensation. This extended control loop is shown in FIG. Due to the high stiffness in the relevant frequency range, the precontrol and motor speed controller design assumes cpm = <psp = S2 / ig, where (pm stands for the motor angular position of the electric motor 2 and cpsp represents the spindle angular position of the spindle 9 of the spindle drive 6. First, the translational total mass, ie mt = rrn + m2 according to the gear ratio ig with the inertia ment of the drive train to a total moment of inertia 0 = 0m + 9k + 0 ^ + mtigz added, where 0m the moment of inertia of the electric motor 2, 0fe the moment of inertia of the clutch 13 and 0 ^ represents the moment of inertia of the spindle 9. This results in the simplified design model 0ω ^ = M ^ -Fextig-
    With F * = Fext and MFF =, the motor speed precontrol follows MFF = mü), ff + Mext, FF With the pilot proportion Μ * ωΡρ, the influence of the moment of inertia and masses of the press during the acceleration phases can be compensated , The input tax share for the compensation of the external force Fext is M ^ ff = F * ig - If the assumption of high stiffness is not justified, this simplified system does not apply and the pilot shares must be calculated using the system in Fig. 3.
    A substitute model for the controlled system Gw ^) Fj (s) is shown in FIG. The transfer function Gw N (s) with the engine torque Mm as the input and the engine speed ωτη as an output forms the output feedback ωηι for the untergeschten speed control loop Tw (s) = 1 + R of these together with the Uber tragungsfunktion GFs (s) with the engine torque Mm as an input and the sensor force Fs as the output, the entire controlled system Gw ^ Fs (s) = -f- = Tw (s) GFs (s) of ωτη the target speed ω ^ as an input to the sensor force Fs as an output from , As controller fc__, a third-order low-pass filter of the form RF (s) = - 3 is selected. The (1 + 4)
    Limit frequency ωΡβ and the gain kFP are adjusted so that a stable behavior for the closed loop adjusts itself. The controller parameters can be adjusted using a loop-shaping method.
    7 shows a flow chart of a schematic sequence of a further control strategy for pressing the workpiece 4, the first two method steps being the same as in the flowchart according to FIG. 2.
    In method step 3, the electric motor 2 is operated at a minimum speed. The minimum speed may vary from process to process and is dictated by the current process parameters. In extreme cases, it may even be necessary for the minimum speed to be zero or approximately zero. The braking of reduced speed to minimum speed should go as quickly as possible or abruptly within the framework of the strength values of the process press 1. In method step 3, the electric motor 2 is operated at minimum speed until the vibrations occurring in the drive train due to the abrupt deceleration maneuver have faded out. For this purpose, a precalculated time duration for the decay of the oscillations is interrogated in query C.
    In an alternative variant, it can also be provided that the time required for decaying the oscillations is not calculated on the basis of a model, but that it is adapted in an iterative method or that the decay of the oscillations by detecting the engine torque in the electric motor 2 in comparison with the measured Torque in the measuring unit 12 is detected.
    Subsequently, in method step 4, a force control, as shown in the structural diagram of the control loop in FIG. 4 or in the controlled system in FIG. 5, is activated. By means of the force control, the electric motor 2 is controlled such that the predetermined pressing force is achieved.
    Various structural diagrams of possible control circuits for force regulation are shown in FIGS. 8 to 14. In order to avoid unnecessary repetition, reference is made to FIG. 5 or the respective preceding figures.
    In the embodiment according to FIG. 8, the input signal used for the force regulator Rf is not the sensor signal Fs, as is the case in FIG. 5, but an estimated force xt is provided as input to the force regulator Rf by a disturbance observer 19. Furthermore, a force precontrol Vf, a load precontrol Vext and an inertia compensation νω are provided.
    In the embodiment according to FIG. 9, the input force used for the force regulator RFein estimated by the disturbance observer 19 is Pext. Furthermore, a force precontrol Vf and an inertia compensation νω are provided.
    In the exemplary embodiment according to FIG. 10, an input quantity for the force regulator RF is a force Fsxt estimated by the disturbance variable observer 19. Furthermore, a force precontrol Vf is provided.
    In the embodiment according to FIG. 11, an input quantity for the force regulator RF is a force Fext estimated by the disturbance observer 19. Furthermore, a force precontrol Vf and a load precontrol Vext are provided.
    In the exemplary embodiment according to FIG. 12, the sensor signal Fs serves as an input variable for the force controller RF. Furthermore, a force precontrol Vf, a load precontrol Vext and an inertia compensation νω are provided.
    In the embodiment according to FIG. 13, the sensor signal Fs serves as an input variable for the force regulator RF. Furthermore, a force precontrol Vf and an inertia compensation Vw are provided.
    In the embodiment according to FIG. 14, the sensor signal Fs serves as an input variable for the force regulator RF. Furthermore, a force precontrol Vf is provided.
    In the embodiment according to FIG. 15, the sensor signal Fs serves as an input variable for the force regulator RF. Furthermore, a force precontrol Vf and a load precontrol Vext are provided.
    The embodiments show possible embodiments, it being noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but also various combinations of the individual embodiments are mutually possible and this variation possibility due to the teaching of technical action by representational invention in Can the expert working in this technical field.
    The scope of protection is determined by the claims. However, the description and drawings are to be considered to interpret the claims. Individual features or combinations of features from the illustrated and described different embodiments may represent for themselves inventive solutions. The task underlying the independent inventive solutions can be taken from the description. All statements of value ranges in the present description should be understood to include any and all sub-ranges thereof, e.g. is the statement 1 to 10 to be understood that all sub-areas, starting from the lower limit 1 and the upper limit 10 are included, ie. all sub-areas begin with a lower limit of 1 or greater and end at an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.
    For the sake of order, it should finally be pointed out that for a better understanding of the construction, elements have been shown partially unevenly and / or enlarged and / or reduced in size.
    LIST OF REFERENCES 1 Process press 2 Electric motor 3 Forming tool 4 Workpiece 5 Control 6 Spindle drive 7 Transmission 8 Drive shaft 9 Spindle 10 Transmission output 11 Transmission output shaft 12 Measuring unit 13 Coupling 14 Bearing 15 Threaded nut 16 Slide 17 Guide rail 18 Pressing surface 19 Disturbance observer
    权利要求:
    Claims (14)
    [1]
    claims
    1. A method for pressing a workpiece (4) with a predetermined pressing force by means of a forming tool (3) which is coupled via a transmission, in particular a spindle drive (6) with an electric motor (2), wherein the spindle drive (6), the rotational Movement of a drive shaft (8) of the electric motor (2) converts into a translational movement of the forming tool (3), and wherein the electric motor (2) is controlled by a controller (5), characterized in that the method comprises the following steps: - accelerate the electric motor (2) in the direction of rotation to a predetermined maximum speed, whereby the forming tool (3) is moved towards the workpiece (4); - Operating the electric motor (2) in maximum speed until the drive shaft (8) of the electric motor (2) has completed a predetermined number of revolutions or the forming tool (3) has reached a predetermined position, wherein during this step, the forming tool (3) freely the workpiece (4) is moved without touching it; - Reduce the speed of the electric motor (2) to a predetermined reduced speed; Operating the electric motor (2) at a reduced speed until a pressure force increase is detected by a measuring unit (12) downstream of the electric motor (2) which exceeds a predetermined threshold value or an increase in torque is detected at the electric motor (2) which exceeds a predetermined threshold value, wherein the Press force increase or torque increase then occurs when the forming tool (3) comes to rest on the workpiece (4) to be formed; - Forming the workpiece (4) under constant detection of the pressing force by means of the measuring unit (12) or the torque on the electric motor (2) until the predetermined pressing force is reached.
    [2]
    2. The method according to claim 1, characterized in that after the detection of the press force increase, the electric motor (2) is braked to a predetermined minimum speed.
    [3]
    3. The method according to claim 2, characterized in that the electric motor (2) is operated for a predetermined or predeterminable period of time at minimum speed until oscillations, which occur in the drive system due to the deceleration of the reduced speed to the minimum speed, have largely eluded.
    [4]
    4. The method according to any one of the preceding claims, characterized in that during the forming of the workpiece (4) the control of the electric motor (2) by the control (5) on the basis of in the measuring unit (12) measured pressing force is specified.
    [5]
    5. The method according to any one of the preceding claims, characterized in that the reduced speed between 0.1% and 100%, in particular between 0.5% and 99%, preferably between 50% and 80% of the maximum speed.
    [6]
    6. The method according to any one of the preceding claims, characterized in that directly after the detection of the press force increase, the further control of the electric motor (2) is predetermined by the control (5) on the basis of the pressing force, wherein after the detection of the press force increase of the electric motor (2 ) is decelerated to a predetermined minimum speed and in an initial period during the deceleration process, the pressing force detected in the measuring unit (12) is superimposed by a based on a model calculation pressing force and after the initial period, the of the measuring unit (12) detected pressing force as input to the regulation (5) is used.
    [7]
    7. The method according to claim 6, characterized in that in the model calculation, the inertia and / or the spring stiffness and / or the damping and the angular or linear accelerations of the individual components installed in the drive train is taken into account.
    [8]
    8. The method according to claim 6 or 7, characterized in that the model calculation is adjusted on the basis of the respective preceding cycles in an iterative learning process, wherein for adapting the model calculation of the time course of the measured value of the pressing force in the measuring unit (12), and the engine torque and the associated angle of rotation of the drive shaft (8) in the electric motor (2) is used.
    [9]
    9. The method according to any one of claims 6 to 8, characterized in that a Störgrößenbeobachter (19), in particular a Kalman filter is used for the cross-fading of model calculation and in the measuring unit (12) detected pressing force.
    [10]
    10. The method according to claim 9, characterized in that a cross-fading is performed between the actual force estimated in the disturbance variable observer (19) and the force detected in the measuring unit (14).
    [11]
    11. The method according to any one of the preceding claims, characterized in that as a measuring unit (12), a piezoelectric sensor is used, which is arranged for detecting the pressing force in the region of the forming tool.
    [12]
    12. The method according to any one of the preceding claims, characterized in that directly after the detection of the press force increase, the further control of the electric motor (2) is predetermined by the controller (5) based on a desired trajectory of the pressing force value, wherein the speed curve in a feedforward is calculated from the desired trajectory of the press force value.
    [13]
    13. The method according to claim 12, characterized in that in a first phase after the detection of the press force increase the press force value by means of a Störgrößenbeobachter (19) is estimated and that in a second phase after the detection of the press force increase the pressing force directly from the measuring unit (12) is detected and serves as input for the control (5).
    [14]
    14. The method according to any one of the preceding claims, characterized in that the transition between different speeds of the individual process steps is specified such that no sudden increases in acceleration occur.
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    同族专利:
    公开号 | 公开日
    US11161316B2|2021-11-02|
    CN109195782A|2019-01-11|
    AT518684B1|2018-05-15|
    WO2017205888A1|2017-12-07|
    CN109195782B|2021-08-03|
    EP3463840A1|2019-04-10|
    US20200324503A1|2020-10-15|
    EP3463840B1|2020-08-05|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50502/2016A|AT518684B1|2016-06-01|2016-06-01|Method for pressing a workpiece with a predetermined pressing force|ATA50502/2016A| AT518684B1|2016-06-01|2016-06-01|Method for pressing a workpiece with a predetermined pressing force|
    EP17739846.8A| EP3463840B1|2016-06-01|2017-05-31|Method for pressing a workpiece with a predetermined pressing force|
    US16/305,558| US11161316B2|2016-06-01|2017-05-31|Method for pressing a workpiece with a predetermined pressing force|
    PCT/AT2017/060143| WO2017205888A1|2016-06-01|2017-05-31|Method for pressing a workpiece with a predetermined pressing force|
    CN201780032951.9A| CN109195782B|2016-06-01|2017-05-31|Method for pressing a workpiece with a predetermined pressing force|
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