Method and device for automatically determining value of state variable of drive train for moving load

Abstract

The invention relates to a method for automatically determining a value of a state variable of a drive train (2) for moving a load (3), the drive train (2) comprising a drive (4) and a drive element (6) which is driven by the drive (4) and which moves together with the load (3), and a stationary support element (7) on which the drive element (6) is supported, in this way, the load (3) is moved relative to the support element (7). The method comprises the following method steps: a) reversely accelerating the load (3) with acceleration by means of the drive (4) by specifying the travel curve (13); b) during the acceleration of the load (3), detecting an actual acceleration of the drive (4) and an actual acceleration of the load (3); and c) determining a value of a state variable of the drive train (2) by evaluating the detected actual acceleration of the drive (4) and the detected actual acceleration of the load (3).

Description

Technical Field

[0001] The invention relates to a method and a device for automatically determining the value of a state variable of a drive train for moving a load, in particular a translationally guided load, wherein the drive train comprises a drive and a drive element, which is driven by the drive and moves with the load, and a fixed support element, on which the drive element is supported in order to move the load relative to the support element. Background Art

[0002] For example, known 2D laser cutting machines use a rack and pinion drive system to move a translationally guided guide carriage. The drive system comprises a motor and a pinion driven by the motor via a transmission, all of which are mounted on the guide carriage and thus move with it, and a stationary rack that meshes with the pinion to move the guide carriage relative to the rack.

[0003] Due to manufacturing tolerances and to protect all involved components from wear, rack / pinion drives typically have backlash. Backlash describes the distance between one tooth flank of the pinion and the closest tooth flank of the rack when the opposing tooth flanks abut each other.

[0004] The magnitude of this backlash must be checked regularly to ensure the machine's functionality. Since rack / pinion drives are typically not equipped with a direct measuring system, additional measuring technology must be used to measure the backlash, and the value must be measured manually, for example during maintenance. Previously, a measuring gauge or probe was installed to measure the relative movement of the guide carriage, on which the transmission and pinion are mounted, relative to the guide rail on which the guide carriage moves. The guide carriage was then manually moved along the guide rail, and the distance traveled without applying excessive force was read using the measuring probe or on a measuring gauge. This value corresponds to the backlash. Summary of the Invention

[0005] In contrast, the present invention is based on the object of providing a method and a device which can automatically measure state variables of a drive train, such as backlash.

[0006] According to the invention, this object is achieved by a method for automatically determining a value of a state variable of a drive train for moving a load, in particular a translationally guided load, wherein the drive train comprises a drive and a drive element, which is driven by the drive and moves together with the load, and a fixed support element, on which the drive element is supported, in order to move the load relative to the support element, the method comprising the following method steps:

[0007] a) accelerating a load by means of a drive over a predetermined driving profile with an acceleration reversal;

[0008] b) during acceleration of the load, detecting the actual acceleration of the driver and detecting the actual acceleration of the load; and

[0009] c) Determining the value of a state variable of the drive train by evaluating the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0010] According to the present invention, a load is moved according to a driving curve by means of a drive controller and accelerated in such a way that acceleration reversals occur, i.e., acceleration passes through zero. During this movement, the drive-side acceleration (actual acceleration of the drive) and the output-side acceleration (actual acceleration of the load) are detected. By comparing these two detected acceleration signals, the value of a state variable can be calculated using a suitable algorithm. The state variable can be automatically monitored during continuous operation of the machine (each time the load transitions from acceleration to deceleration). The actual acceleration of the drive can, for example, correspond to a target acceleration of the load predetermined by the drive controller. The method according to the present invention can provide information about the state of the machine as part of a state diagnosis and, if necessary, support fault diagnosis.

[0011] The state variable is preferably the backlash of the drive train, which is unavoidable in rack / pinion drives or screw transmissions (e.g., ball screw drives). Backlash is particularly effective when there is a reversal of acceleration on the load. In this case, the tooth flanks of the pinion and rack separate, and the load continues to travel until the backlash is exhausted and the tooth flanks on opposite sides collide. This allows the backlash to be automatically monitored during the continuous operation of the machine. Alternatively, the state variable can be, for example, the elasticity of the drive train or the degree of contamination.

[0012] Preferably, the co-moving drive element meshes with a stationary support element to move the load relative to the support element. For example, the moving drive element is a pinion and the stationary support element is a rack (or conversely, the drive element is the rack and the support element is the pinion), and the drive element and the support element mesh with each other.

[0013] The drive preferably moves together with the load, but can alternatively be used independently of the load, ie can be stationary like the supporting element.

[0014] Particularly advantageously, the actual acceleration of the drive is determined from the detected rotational speed of the drive designed as a rotary motor. The rotational speed of the rotary motor can be detected, for example, by means of a motor measuring system that is usually already present for the rotary motor.

[0015] Preferably, an acceleration sensor mounted on the load itself or on an element moving together with the load is used to detect the actual acceleration of the load. The use of such an acceleration sensor is a very cost-effective solution, especially since so-called MEMS acceleration sensors are already available at low cost and of sufficiently good quality.

[0016] The actual acceleration of the drive and the actual acceleration of the load are preferably detected synchronously in time during the acceleration of the load, but can alternatively be synchronized with one another subsequently, ie after the detection process.

[0017] Preferably, the predetermined driving profile includes forward and backward movement of the load. For example, the motor controller moves the axis of the load to be tested forward and backward by a few millimeters one or more times in a step-like (ruckbegrenzten, limited-impact) trajectory, so that the acceleration reversal is achieved by this reversal of movement. Alternatively, driving profiles with only forward or only backward movement of the load are also possible, as long as there is an acceleration reversal.

[0018] Various methods can be used to evaluate the detected actual acceleration of the drive and the detected actual acceleration of the load in order to determine the value of the state variable of the drive train.

[0019] In a first evaluation variant, the relationship between the state variable and the changes in the acceleration profile of the actual acceleration of the drive and the actual acceleration of the load is experimentally determined and stored for different values ​​of the state variable. When a tooth flank collides after an acceleration reversal, the moving load mass suddenly decelerates or the drive is impacted. These sudden changes in the acceleration profile are more pronounced as the state variable increases. This relationship can be experimentally determined and stored on the machine. Based on this stored relationship, the value of the state variable can be determined based on the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0020] In a second evaluation variant, for different values ​​of the state variable, the relationship between the state variable and the following time period is experimentally determined and stored: during this time period, the drive element and the support element separate from each other and come into contact with each other again in the case of acceleration reversal. The larger the state variable, the longer the time period between the separation of the tooth surfaces and the re-collision. The separation time point is the time point at which acceleration reversal occurs in the drive, for example, the transition from acceleration to deceleration. The collision time point is the time point at which the mass acceleration (Massebeschleunigung) suddenly decreases or the drive acceleration suddenly increases. Such a relationship between a time period and the state variable can be experimentally determined and stored on the machine. Based on the stored relationship, the value of the state variable can be determined based on the actual acceleration of the detected drive and the actual acceleration of the detected load.

[0021] In a third evaluation variant, the times at which the drive element and the support element separate from each other and come into contact again during the acceleration reversal, the distance covered during this time, and the value of the state variable are analytically calculated based on the detected actual acceleration of the drive and the detected actual acceleration of the load. If the acceleration measurement signal has sufficiently good quality (resolution, noise), the distance covered and, therefore, the state variable can be analytically calculated based on the times at which the tooth flanks separate and the times at which the tooth flanks collide.

[0022] The present invention also relates to a device for automatically determining the value of a state variable of a drive train for moving a load, in particular a translationally guided load, in particular for carrying out the method according to the invention, comprising:

[0023] a drive train comprising: a driver and a drive element which is driven by the driver and moves together with the load, and a fixed support element on which the drive element is supported so as to move the load relative to the support element,

[0024] - first means for detecting the actual acceleration of the drive,

[0025] - a second device for detecting the actual acceleration of the load, and

[0026] An evaluation device is programmed or configured to determine a value of a state variable of the drive train as a function of the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0027] Preferably, the drive element engages with a fixed support element and the drive also moves with the load.

[0028] The drive can be, for example, an electric rotary motor or an electric linear motor or a hydraulic motor. In the case of an electric rotary motor, the first device is preferably formed by a motor measuring system already present in the rotary motor for determining the motor rotational speed.

[0029] In an advantageous embodiment, the drive train has a transmission (for example a planetary transmission) acting between the driver and the drive element, which transmission moves together with the load.

[0030] The second means are preferably formed by an acceleration sensor which is mounted on the load itself or on an element which moves together with the load.

[0031] Preferably, the drive train is formed by a pinion / rack drive train, in particular with a pinion as the drive element and a rack as the support element, or by a screw drive, in particular a ball screw drive. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further advantages and advantageous configurations of the subject matter of the present invention can be derived from the description, the claims and the drawings. Likewise, the features mentioned above and those not yet mentioned can be used alone or in combination in any combination. The embodiments shown and described are not to be understood as exhaustive, but rather as having exemplary character for describing the present invention. In the drawings:

[0033] Figure 1 Schematically shows a device according to the invention for automatically determining backlash in a rack / pinion drive train;

[0034] Figure 2a shows the backlash in the pinion / rack drive train as the pinion on the rack accelerates counterclockwise;

[0035] Figure 2b shows the backlash in the pinion / rack drive train as the pinion on the rack accelerates clockwise;

[0036] Figure 3 The method for automatically determining backlash according to the present invention is shown. Figure 1 An exemplary travel curve (target trajectory) of the guide carriage shown in ; and

[0037] Figure 4 The time-synchronized actual accelerations of the drive and the load detected during the execution of the method according to the invention are shown. DETAILED DESCRIPTION

[0038] Figure 1The device 1 shown serves to automatically determine a state variable, here the backlash S ( Figure 2a 、 Figure 2b ))--the load being formed here, for example, by a translationally guided guide carriage 3.

[0039] The drive train 2 comprises a drive, here implemented as a (rotating) motor 4, and a drive element, here implemented as a pinion 6, which is driven by the motor 4 via an optional transmission 5. The motor 4, transmission 5, and pinion 6 are mounted on the guide carriage 3 and thus move together with the guide carriage 3. The drive train 2 also comprises a stationary support element, here implemented as a rack 7, with which the pinion 6 meshes to move the guide carriage 3 together with the motor 4, transmission 5, and pinion 6 in the longitudinal direction A of the rack relative to the rack 7. The rotation of the motor 4, transmission 5, and pinion 6 is counterclockwise here, as indicated by arrows 19, 20, and 21.

[0040] like Figure 2a and Figure 2b As shown, for functional reasons, the tooth thickness of the pinion 6 is smaller than the tooth width between two teeth of the rack 7 (reverse clearance S). Figure 2a If driven counterclockwise as shown, the pinion 6 rolls on the rack 7 and moves to the left (rotational movement 21, arrow direction A) - here in particular, it is shown with an acceleration b1 of the pinion 6 to the left, whereby the guide carriage 3 moves to the left together with the motor 4 and the transmission 5. Here, the pinion 6 engages with its teeth 8 in the tooth gap 9 of the rack 7, wherein the right tooth flank 8a of the tooth 8 rests on the right tooth flank 9a of the tooth gap 9. If a reversal of acceleration occurs on the guide carriage 3 and therefore also on the pinion 6, then as shown Figure 2b As shown, the right tooth flanks 8a and 9a separate from each other until, after the backlash S has been exhausted, the left tooth flank 8b of the tooth 8 now rests on the left tooth flank 9b of the tooth gap 9. The pinion 6 continues to roll to the left on the rack 7 (rotational movement 21, arrow direction A), but with an acceleration b2 to the right, whereby the guide carriage 3, together with the motor 4 and the transmission 5, accelerates to the right.

[0041] The rotational speed of the motor 4 is detected by means of a first device, here in the form of a motor measurement system 10. The actual acceleration of the motor 4 can then be determined from the detected rotational speed. Alternatively, the actual acceleration of the motor 4 can also be determined using an additional acceleration sensor, for example, which is mounted on the pinion 6.

[0042] The actual acceleration of the guide carriage 3 is determined by means of an acceleration sensor 11 which is mounted on the guide carriage 3 itself or on one of the elements 4 to 6 moving together with the guide carriage 3 , for example, here on the housing of the transmission 5 .

[0043] The value of the backlash S of the drive train 2 can be determined in the evaluation device 12 from the detected actual acceleration of the drive 4 and the detected actual acceleration of the guide carriage 3 .

[0044] The following method steps are carried out to automatically determine the value of the backlash S.

[0045] By predefining a driving profile, the guide carriage 3 is accelerated in the opposite direction by means of the motor 4. The driving profile is stored, for example, in a motor controller. Figure 3 The distance (s) / time (t) diagram shows a travel curve 13 in the form of a shock-limited, step-like target trajectory 14 of the guide carriage 3. In the shown travel curve 13, the guide carriage 3 moves forward in a step-like manner by 3 mm at the time t=approximately 1 s and then moves back in a step-like manner by 3 mm at the time t=approximately 2.2 s.

[0046] During this movement of the guide carriage 3, the actual acceleration of the motor 4 is detected by the motor measurement system 10 and the actual acceleration of the guide carriage 3 is detected by the acceleration sensor 11. More precisely, the motor acceleration can be determined from the detected motor speed by differentiation and optional smoothing.

[0047] In the evaluation device 12 , various methods are used to evaluate the synchronously detected or subsequently time-synchronized actual accelerations of the motor 4 and the guide carriage 3 in order to determine the value of the backlash S of the drive train 2 .

[0048] Figure 4 The acceleration (a) / time (t) graph shows the acceleration of the motor 4 (solid line a) and the acceleration of the guide carriage 3 (dashed line b) detected at time t = approximately 1 s for the travel curve 13. During the transition from acceleration to deceleration, i.e., during the acceleration reversal (zero crossing) at time t = approximately 1.1 s, a time offset Δt occurs between the two curves a and b, caused by backlash S. Based on this time offset Δt, backlash S can be determined using various methods.

[0049] In a first evaluation variant, the relationship between the state variable and the changes in the acceleration profile of the actual acceleration of the motor 4 and guide carriage 3 is experimentally determined and stored for different values ​​of backlash S. When tooth flanks collide after an acceleration reversal, the moving guide carriage 3 brakes suddenly or the motor 4 is jolted. The greater the backlash S, the more pronounced these sudden changes in the acceleration profile. This relationship can be experimentally determined and stored in the evaluation device 12. Based on this stored relationship, the value of backlash S can be determined from the detected actual accelerations of the motor 4 and the guide carriage 3.

[0050] In a second evaluation variant, the relationship between the state variable and the time period during which the pinion 6 and rack 7 separate from each other and come into contact with each other again in the event of a reversal of acceleration is experimentally determined and stored for different values ​​of the backlash S. The greater the backlash S, the longer the time period between the separation and the re-collision of the tooth surfaces of the pinion 6 and rack 7. The separation time point is the time point at which the motor 4 undergoes a reversal of acceleration, for example, a transition from acceleration to deceleration. The collision time point is the time point at which the mass acceleration suddenly decreases or the motor acceleration suddenly increases. This relationship between such a time period and the backlash S can be experimentally determined and stored in the evaluation device 12. Based on the stored relationship, the value of the backlash S can be determined based on the detected actual acceleration of the motor 4 and the detected actual acceleration of the guide slide 3.

[0051] In a third evaluation variant, the times at which pinion 6 and rack 7 separate from each other and come into contact again in the event of a reversal of acceleration, the distance covered during this time, and, from this, the value of the backlash S are analytically calculated based on the detected actual acceleration of motor 4 and the detected actual acceleration of guide carriage 3. If the acceleration measurement signal has sufficiently good quality (resolution, noise), the distance covered and, therefore, the value of the backlash S can be analytically calculated based on the times at which the tooth flanks separate and the times at which the tooth flanks collide.

Claims

1. A method for automatically determining the value of a state variable of a drive train (2) for moving a load (3), wherein: The drive system (2) comprises: a driver (4); and a drive element (6) driven by the driver (4), the drive element moving together with the load (3); as well as , a stationary support element (7), the drive element (6) being supported on the support element so as to move the load (3) relative to the support element (7), the method comprising the following method steps: a) accelerating the load (3) with the aid of the drive (4) in a reverse direction by means of a predetermined driving curve (13); b) during the acceleration of the load (3), detecting an actual acceleration of the drive (4) and detecting an actual acceleration of the load (3); as well as c) determining the value of the state variable of the drive train (2) by evaluating the detected actual accelerations of the drive (4) and the load (3).

2. The method according to claim 1, characterized in that The state variable is the backlash (S) of the drive train (2).

3. The method according to claim 1 or 2, characterized in that The drive element (6) engages with the stationary support element (7) to move the load (3) relative to the support element (7).

4. The method according to any one of the preceding claims, characterized in that The driver (4) also moves together with the load (3).

5. The method according to any one of the preceding claims, characterized in that The rotational speed of a drive (4) designed as a rotary motor is detected, and the actual acceleration of the drive (4) is determined from the detected rotational speed.

6. The method according to claim 5, characterized in that The rotation speed of the rotary motor is detected by a motor measurement system (10) of the rotary motor.

7. The method according to any one of the preceding claims, characterized in that The actual acceleration of the load (3) is detected by means of an acceleration sensor (11), which is mounted on the load (3) itself or on an element (4 to 6) that moves together with the load (3).

8. The method according to any one of the preceding claims, characterized in that The actual accelerations of the drive (4) and the load (3) are detected in a time-synchronous manner during the acceleration of the load (3) or are subsequently time-synchronized with each other after the detection process.

9. The method according to any one of the preceding claims, characterized in that The predetermined driving curve (13) includes both forward and backward movement of the load (3), or only forward movement of the load (3), or only backward movement of the load (3).

10. The method according to any one of the preceding claims, characterized in that For different values ​​of the state variable, the relationship between the state variable and the change in the acceleration trend of the actual acceleration of the drive (4) and the load (3) is experimentally determined and stored, and based on the stored relationship, the value of the state variable is determined from the detected actual acceleration of the drive (4) and the load (3).

11. The method according to any one of claims 1 to 9, characterized in that For different values ​​of the state variable, the relationship between the state variable and the time period during which the drive element and the support element (6, 7) separate from each other and again come into contact with each other under acceleration reversal is experimentally determined and stored, and based on the stored relationship, the value of the state variable is determined from the detected actual acceleration of the drive (4) and the load (3).

12. The method according to any one of claims 1 to 9, characterized in that Based on the detected actual accelerations of the drive (4) and the load (3), the time points at which the drive element and the support element (6, 7) separate from each other and come back into contact with each other in the event of a reversal of acceleration, the distance covered, and the value of the state variable are analytically calculated therefrom.

13. A device for automatically determining the value of a state variable of a drive train (2) for moving a load (3), the device comprising: - a drive train (2), comprising: a drive (4); and a driving element (6) driven by the driver (4), the driving element moving together with the load (3); as well as , a stationary support element (7), the drive element (6) being supported on the support element so as to move the load relative to the support element (7), - first means (10) for detecting the actual acceleration of the drive (4), - second means (11) for detecting the actual acceleration of said load (3), and An evaluation device (12) programmed to determine a value of a state variable of the drive train (2) from the detected actual accelerations of the driver (4) and the load (3).

14. The device according to claim 13, characterized in that The driving element (6) engages with the stationary supporting element (7).

15. The device according to claim 13 or 14, characterized in that The driver (4) also moves together with the load (3).

16. The device according to any one of claims 13 to 15, characterized in that The drive (4) is an electric rotary motor or an electric linear motor or a hydraulic motor.

17. The apparatus according to any one of claims 13 to 16, characterized in that The drive (4) is an electric rotary motor, and the first device is formed by a motor measuring system (10) of the rotary motor for determining the motor rotational speed.

18. The apparatus according to any one of claims 13 to 17, characterized in that The drive train (2) has a transmission (5) acting between the driver (4) and the drive element (6), the transmission moving together with the load (3).

19. The apparatus according to any one of claims 13 to 18, characterized in that The second means are formed by an acceleration sensor (11) mounted on the load (3) itself or on an element (4 to 6) moving together with the load (3).

20. The apparatus according to any one of claims 13 to 19, characterized in that The drive train (2) is formed by a pinion / rack drive train or by a screw gear.

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