Method and apparatus for automatically determining values ​​of drivetrain state variables for moving a load - Patents.com

Abstract

The present invention relates to a method for automatically determining values ​​of state variables of a drive train (2) for moving a load (3), the drive train (2) comprising a drive (4) and a drive element (6) driven by the drive (4) and moving together with the load (3), and a fixed support element (7) on which the drive element (6) is supported, thereby moving the load (3) relative to the support element (7), the method comprising the following method steps: a) accelerating the load (3) by the drive (4) by specifying a drive profile (13) with acceleration reversal; b) detecting the actual acceleration of the drive unit (4) during acceleration of the load (3) and detecting the actual acceleration of the load (3); c) determining values ​​of state variables of the drivetrain (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 present invention relates to a method and apparatus for automatically determining values ​​of state variables of a drive train for moving a load, in particular a translationally driven load, the drive train having a drive section, a drive element driven by the drive section and moving with the load, and a fixed support element on which the drive element is supported, to move the load relative to the support element.

[0002] For example, known 2D laser cutting machines use a rack and pinion drive train to move a translationally driven guide carriage, the drive train including a motor and a pinion driven by the motor via gears, all of which are attached to the guide carriage so as to move with it, and a fixed rack that meshes with the pinion to move the guide carriage relative to the rack.

[0003] Due to manufacturing tolerances and to protect all components involved from wear, rack and pinion drives usually have some back play, which describes the distance between one tooth flank on the pinion and the next tooth flank on the rack when the opposing tooth flanks are in contact with each other.

[0004] The degree of this reverse play must be checked regularly to ensure the functionality of the machine. Since rack and pinion drives often lack direct measurement systems, additional measurement techniques must be implemented to measure the play, for example, manually during a service call. Traditionally, meters or measuring probes have been installed to measure the relative displacement of the guide carriage, on which the gear and pinion are mounted, relative to the guide rail on which the guide carriage moves. The guide carriage is then manually moved along the guide rail, and the distance traveled without excessive force is read by the measuring probe or on the meter. This value corresponds to the reverse play.

[0005] In contrast, the object of the present invention is to disclose a method and an apparatus that can automatically measure any drive train state variable, such as reverse play.

[0006] This object is achieved according to the invention by a method for automatically determining values ​​of state variables of a drive train for moving a load, in particular a translationally driven load, the drive train having a drive, a drive element driven by the drive and moving together with the load, and a fixed support element on which the drive element is supported, for moving the load relative to the support element, the method comprising the following method steps: a) accelerating the load with a drive by specifying a drive profile with acceleration reversal; b) detecting an actual acceleration of the drive during acceleration of the load, and detecting an actual acceleration of the load; c) determining values ​​of drivetrain state variables by evaluating the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0007] According to the present invention, the load is moved by the drive control according to a drive profile and accelerated until an acceleration reversal, i.e., an acceleration zero crossing, occurs. 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, a suitable algorithm can be used to determine the value of the state variable. The state variable can be automatically monitored during machine operation (whenever the load switches from accelerating to braking). The actual acceleration of the drive can correspond, for example, to a target acceleration of the load predetermined by the drive control. The method according to the present invention can provide information about the state of the machine as part of a condition diagnosis and, if necessary, support for fault diagnosis.

[0008] Preferably, the state variable is the reverse play of the drive train, which is unavoidably present, for example, in rack / pinion drives or screw drives (e.g., ball screw drives). The reverse play is particularly pronounced in areas when there is an acceleration reversal in the load. At this point, the pinion tooth flank and the rack tooth flank separate from each other, and the load continues to move until the opposite tooth flanks collide with each other once the reverse play is complete. This allows for automatic monitoring of the reverse play during machine operation. Alternatively, the state variable may be, for example, the elasticity or degree of contamination of the drive train.

[0009] Preferably, the co-moving drive element meshes with a fixed support element to move the load relative to the support element, for example the moving drive element is a pinion and the fixed support element is a rack (or vice versa), both of which mesh with each other.

[0010] The drive preferably moves with the load, but may alternatively not be used with the load, i.e. may be fixed in the same way as the support element.

[0011] Particularly advantageously, the actual acceleration of the drive is determined from the detected rotational speed of the drive designed as a rotary motor, which can be detected, for example, by a motor measurement system that is usually already present in the rotary motor.

[0012] Preferably, the actual acceleration of the load is detected using an acceleration sensor attached to the load itself or to an element moving with 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.

[0013] The actual acceleration of the drive and the actual acceleration of the load are preferably detected synchronously during the acceleration of the load, but can alternatively be synchronized with each other a posteriori, i.e. after the detection process.

[0014] Preferably, the predetermined drive profile includes forward and backward movement of the load. The load shaft to be tested is moved forward and backward a few millimeters one or more times via the motor controller using a stepped (jerk-limited) trajectory, and acceleration reversal is achieved through the reversal of this movement. Alternatively, drive profiles with only forward movement of the load or only backward movement of the load are also conceivable, as long as there is acceleration reversal.

[0015] The sensed actual acceleration of the drive and the sensed actual acceleration of the load can be evaluated using a variety of methods to determine the values ​​of the drivetrain state variables.

[0016] For the first evaluation variable, the relationship between the state variable and the changes in the acceleration process of the actual acceleration of the drive unit and the actual acceleration of the load is experimentally confirmed and stored for different values ​​of the state variable. If the tooth flanks collide after an acceleration reversal, the moving load mass is suddenly braked or the drive unit is impacted. The larger the state variable, the stronger these sudden changes in the acceleration process. This relationship can be experimentally confirmed and stored in the machine. Based on the stored relationship, the value of the state variable can be determined from the detected actual acceleration of the drive unit and the detected actual acceleration of the load.

[0017] In a second evaluation variant, the relationship between the state variable and the time period during which the drive element and the support element separate and re-enter contact during the acceleration reversal is experimentally determined and stored for different values ​​of the state variable. The larger the state variable, the longer the time period between the release of the tooth flanks and the re-impact. The release moment is when the drive undergoes an acceleration reversal, for example, when the drive switches from acceleration to braking. The impact moment is when the mass acceleration suddenly decreases or the drive acceleration suddenly increases. The relationship between this time period and the state variable can be experimentally determined and stored in the machine. Based on the stored relationship, the value of the state variable can be determined from the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0018] For the third evaluation variable, from the detected actual acceleration of the drive and the detected actual acceleration of the load, the time point at which the drive element and the support element separate from each other and come into contact with each other again during the acceleration reversal, the travel distance and thus the value of the state variable are analytically calculated. If the acceleration measurement signal is of sufficiently good quality (resolution, noise), the travel distance, i.e. the state variable, can be analytically calculated from the time of tooth flank separation and the time of tooth flank impact.

[0019] The invention also relates to a device for automatically determining values ​​of state variables of a drive train for moving a load, in particular a translationally driven load, in particular for carrying out the method according to the invention, comprising: a drive train having a drive part, a drive element driven by the drive part and moving with the load, and a fixed support element on which the drive element is supported, for moving the load relative to the support element; a first device for detecting the actual acceleration of the drive; a second device for detecting the actual acceleration of the load; an evaluation device programmed or configured to determine values ​​of state variables of the drive train from the detected actual acceleration of the drive and the detected actual acceleration of the load.

[0020] Preferably, the drive element engages a fixed support element, and the drive also moves with the load.

[0021] The drive may be, for example, an electric rotary motor, a linear motor or a hydraulic motor. In the case of an electric rotary motor, the first device is preferably formed by a motor measurement system for determining the motor speed, which is already present in the rotary motor.

[0022] In an advantageous embodiment, the drive train comprises gears (eg planetary gears) acting between the drive and the drive element and moving with the load.

[0023] The second device is preferably formed by an acceleration sensor attached to the load itself or to an element that moves with the load.

[0024] 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 explanation of the drawings]

[0025] Further advantages and advantageous embodiments of the subject matter of the present invention are evident from the description, the claims and the drawings. Likewise, the features mentioned above and those to be presented may in each case be used alone or together in any desired combination. The illustrated and described embodiments should not be understood as an exhaustive list, but rather as exemplary features for explaining the invention. In the drawings: [Figure 1] 1 shows a schematic representation of an apparatus for automatically determining reverse play in a rack and pinion drive train according to the present invention; [Figure 2a] 1 shows the reverse play in a pinion / rack drive train when accelerating the pinion on the rack counterclockwise. [Figure 2b] Shown is the reverse play of the pinion / rack drive train when accelerating the pinion on the rack clockwise. [Figure 3] 2 shows an exemplary drive profile (target trajectory) of the guide carriage shown in FIG. 1 moved by the drive train when carrying out the method according to the invention for automatically determining the reverse play; [Figure 4] 4 shows the time-synchronized actual acceleration of the drive and the load detected when carrying out the method according to the invention;

[0026] The device 1 shown in FIG. 1 is used to automatically determine the value of a state variable, in this case the reverse play S (FIGS. 2a, 2b), in a drive train 2 for moving a load, which here is formed, for example, by a translationally driven guide carriage 3.

[0027] The drive train 2 comprises a drive, here designed as a (rotary) motor 4, and a drive element, here designed as a pinion 6, driven by the motor 4 by means of an optional gear 5. The motor 4, gear 5 and pinion 6 are attached to the guide carriage 3 and thereby move together with it. The drive train 2 further comprises a fixed support element, here shown as a rack 7, with which the pinion 6 meshes, causing the guide carriage 3 to move together with the motor 4, gear 5 and pinion 6 in its longitudinal direction A relative to the rack 7. The rotation of the motor 4, gear 5 and pinion 6, here counterclockwise, is indicated by arrows 19, 20 and 21.

[0028] As shown in Figures 2a and 2b, for functional reasons, the tooth thickness of the pinion 6 is smaller than the gap width between two teeth of the rack 7 by a (reverse) play S. When the pinion 6 is driven counterclockwise as shown in Figure 2a, the pinion 6 rolls on the rack 7 and moves to the left (rotational movement 21, arrow direction A), as specifically shown here by the left acceleration b1 of the pinion 6, causing the guide carriage 3 to move to the left together with the motor 4 and gear 5. The pinion 6 engages with a tooth 8 in a tooth gap 9 of the rack 7, and the right tooth flank 8a of the tooth 8 is supported on the right tooth flank 9a of the tooth gap 9. If there is an acceleration reversal on the guide carriage 3, and therefore on the pinion 6, after completing the reverse play S, the right tooth flanks 8a, 9a separate from each other until the left tooth flank 8b of the tooth 8 abuts the left tooth flank 9b of the tooth gap 9, as shown in Figure 2b. The pinion 6 continues to move to the left while rolling on the rack 7 (rotational movement 21, arrow direction A), but moves to the right with acceleration b2, accelerating the guide carriage 3 together with the motor 4 and gear 5 to the right.

[0029] The rotational speed of the motor 4 is detected by 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 attached to the pinion 6.

[0030] The actual acceleration of the guide carriage 3 is determined by 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 gear 5.

[0031] The value of the reverse play 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 .

[0032] To automatically determine the value of the reverse play S, the following method steps are carried out:

[0033] The guide carriage 3 is accelerated by the motor 4 by specifying a drive profile with acceleration reversal. The drive profile is stored, for example, in the motor control unit. Figure 3 shows such a drive profile 13 in the form of a jerk-limited stepped target trajectory 14 of the guide carriage 3 in a distance / time diagram. In the illustrated drive profile 13, the guide carriage 3 moves forward by one step of 3 mm at time t = approximately 1 second, and then moves backward by one step of 3 mm at time t = approximately 2.2 seconds.

[0034] During this movement of the guide carriage 3, the actual acceleration of the motor 4 is detected by a motor measurement system 10 and the actual acceleration of the guide carriage 3 is detected by an acceleration sensor 11. More precisely, the engine acceleration can be ascertained from the detected motor speed by differentiation and optional correction.

[0035] In the evaluation device 12, the actual acceleration of the motor 4 and the actual acceleration of the guide carriage 3, detected synchronously or subsequently, are evaluated using various methods to determine the value of the reverse play S of the drive train 2.

[0036] 4 shows, in an acceleration (a) / time (t) diagram, the acceleration of the motor 4 (solid line a) and the acceleration of the guide carriage 3 (dashed line b) detected for the drive profile 13 at time t = approx. 1 second. During the transition from acceleration to deceleration, i.e., during the acceleration reversal (zero crossing) at time t = approx. 1.1 seconds, a time offset Δt occurs between the two curves a and b, which results from the reverse play S. From this time offset Δt, the reverse play S can be determined in various ways.

[0037] For the first evaluation variable, the relationship between the changes in the acceleration process of the actual acceleration of the motor 4 and the actual acceleration of the guide carriage 3 is experimentally determined and stored for different values ​​of the reverse play S. If a tooth flank collides after an acceleration reversal, the moving guide carriage 3 is suddenly braked or the motor 4 is shocked. The greater the reverse play S, the stronger these sudden changes in the acceleration process. This relationship can be experimentally determined and stored in the evaluation device 12. Based on the stored relationship, the value of the reverse play S can be determined from the detected actual acceleration of the motor 4 and the detected actual acceleration of the guide carriage 3.

[0038] For the second evaluation variable, the relationship between the time periods during which the pinion 6 and rack 7 separate and re-enter contact during an acceleration reversal is experimentally determined and stored for different values ​​of the reverse play S. The larger the reverse play S, the longer the time period between the separation of the tooth flanks of the pinion 6 and rack 7 and their re-entry into contact. The moment of separation occurs when the motor 4 undergoes an acceleration reversal, e.g., when it transitions from acceleration to braking. The moment of impact occurs when the mass acceleration suddenly decreases or the motor acceleration suddenly increases. This relationship between this time period and the reverse play S can be experimentally determined and stored in the evaluation device 12. Based on the stored relationship, the value of the reverse play S can be determined from the detected actual acceleration of the motor 4 and the detected actual acceleration of the guide carriage 3.

[0039] For the third evaluation variable, from the detected actual acceleration of the motor 4 and the detected actual acceleration of the guide carriage 3, the time point at which the pinion 6 and the rack 7 separate from each other and come into contact with each other again during the acceleration reversal, the travel distance and thus the value of the reverse play S are analytically calculated. If the acceleration measurement signal is of sufficiently good quality (resolution, noise), the travel distance and therefore the reverse play S can be analytically calculated from the time of tooth flank separation and the time of tooth flank collision.

Claims

1. 1. A method for automatically determining values ​​of state variables of a drive train (2) for moving a load (3), the drive train (2) having a drive (4) and a drive element (6) driven by the drive (4) and moving together with the load (3), and a fixed support element (7) on which the drive element (6) is supported, thereby moving the load (3) relative to the support element (7), the method comprising the following method steps: a) accelerating the load (3) by the drive (4) by specifying a drive profile (13) with acceleration reversal; b) detecting an actual acceleration of the drive unit (4) during acceleration of the load (3) and detecting the actual acceleration of the load (3); c) determining the value of the 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).

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

3. 3. A method according to claim 1 or 2, characterized in that the drive element (6) engages the fixed support element (7) thereby moving the load (3) relative to the support element (7).

4. Method according to any one of claims 1 to 3, characterized in that the drive (4) also moves together with the load (3).

5. 5. The method according to claim 1, wherein 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. 6. The method according to claim 5, characterized in that the rotational speed of the rotary motor is detected by a motor measurement system (10) of the rotary motor.

7. 7. The method according to any one of claims 1 to 6, characterized in that the actual acceleration of the load (3) is detected by an acceleration sensor (11) mounted on the load (3) itself or on an element (4-6) moving with the load (3).

8. 8. The method according to any one of claims 1 to 7, characterized in that the actual acceleration of the drive (4) and the actual acceleration of the load (3) are detected synchronously during the acceleration of the load (3) or are subsequently synchronized with each other after the detection process.

9. 9. The method according to any one of claims 1 to 8, characterized in that the predetermined drive profile (13) comprises a forward and a backward movement of the load (3), only a forward movement of the load (3), or only a backward movement of the load (3).

10. 10. The method according to claim 1, wherein a relationship between the state variables and the changes in the acceleration process of the actual acceleration of the drive unit (4) and the actual acceleration of the load (3) is experimentally ascertained and stored for different values ​​of the state variables, and the value of the state variable is determined from the detected actual acceleration of the drive unit (4) and the detected actual acceleration of the load (3) using the stored relationship.

11. 10. The method according to claim 1, wherein a relationship between the state variable and the time period during which the drive element (6) and the support element (7) separate from each other and come into contact with each other again during an acceleration reversal is experimentally ascertained and stored for different values ​​of the state variable, and wherein the value of the state variable is determined from the detected actual acceleration of the drive (4) and the detected actual acceleration of the load (3) using the stored relationship.

12. 10. The method according to claim 1, wherein from the detected actual acceleration of the drive (4) and the detected actual acceleration of the load (3), the time points at which the drive element (6) and the support element (7) separate from each other and come into contact with each other again during an acceleration reversal, the travel distance and thereby the values ​​of the state variables are analytically calculated.

13. 1. An apparatus for automatically determining values ​​of state variables of a drive train (2) for moving a load (3), comprising: a drive train (2) comprising a drive (4), a drive element (6) driven by said drive (4) and moving with said load (3), and a fixed support element (7) on which said drive element (6) is supported, thereby moving said load relative to said support element (7); a first device (10) for detecting the actual acceleration of said drive (4); a second device (11) for detecting the actual acceleration of the load (3); an evaluation device (12) programmed to determine values ​​of state variables of the drive train (2) from the detected actual acceleration of the drive (4) and the detected actual acceleration of the load (3).

14. 14. Device according to claim 13, characterized in that the drive element (6) meshes with the fixed support element (7).

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

16. Device according to any one of claims 13 to 15, wherein the drive (4) is an electric rotary motor or a linear motor or a hydraulic motor.

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

18. 18. Apparatus according to any one of claims 13 to 17, characterized in that the drive train (2) comprises a gear (5) acting between the drive (4) and the drive element (6) moving with the load (3).

19. 19. Device according to any one of claims 13 to 18, characterized in that the second device is formed by an acceleration sensor (11) attached to the load (3) itself or to an element (4-6) moving with the load (3).

20. Device 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 a screw drive.

Images