CN113370573B - System and method for restraining clearance impact of mechanical transmission system of servo press - Google Patents
System and method for restraining clearance impact of mechanical transmission system of servo press Download PDFInfo
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- CN113370573B CN113370573B CN202010160350.XA CN202010160350A CN113370573B CN 113370573 B CN113370573 B CN 113370573B CN 202010160350 A CN202010160350 A CN 202010160350A CN 113370573 B CN113370573 B CN 113370573B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/26—Programme control arrangements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/14—Control arrangements for mechanically-driven presses
- B30B15/148—Electrical control arrangements
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Abstract
The invention discloses a clearance impact suppression system of a mechanical transmission system of a servo press, which comprises a control system, a motor and a servo motor, wherein the control system is connected with the motor through a power cable; an output shaft of the motor is mechanically connected with the speed reducer and is provided with an encoder, and a signal output end of the encoder is electrically connected with the control system; the speed reducer is connected with the sliding block through a crank connecting rod mechanism, and the corresponding method is to judge whether the transmission system is in a clearance state in real time in the servo control process. If the sliding block is in the clearance state, the motor is commanded to output smaller torque, so that the rotating speed difference between the driving side and the load side is limited, and the impact can be reduced, and the sliding block is driven by the crank-link mechanism to move up and down along the guide rail.
Description
Technical Field
The invention relates to the field of servo press control, in particular to a system and a method for restraining clearance impact of a mechanical transmission system of a servo press.
Background
The servo press machine adopts a servo motor to generate power, and pushes a sliding block to reciprocate through a mechanical transmission mechanism such as a gear, a crank, a connecting rod or a threaded screw rod to generate pressure, so that the material is extruded and formed. Because the mechanical transmission system has a gap, when the servo motor rotates in a certain angle range, the load keeps still, the transmission system is in a gap state at the moment, the load is separated from the motor, and the motor is in an idle state. If the motor rotates at a fast speed, the driving-side components connected to the motor shaft will quickly hit the load-side components, thereby causing an impact. Not only is the noise huge, but also the equipment is easy to damage, the abrasion is accelerated, and the service life of the equipment is shortened.
At present, the high-precision parts are generally adopted in the industry to reduce the clearance of a transmission system as much as possible, so that the impact is reduced. However, this method requires precision machining of the parts, resulting in expensive equipment. And wear is inevitable as the use time is prolonged, and the gap is increased, thereby generating impact.
With the progress of automatic control technology, a technology for suppressing backlash strike by a control method has now appeared. A chinese patent document entitled control method, apparatus, system for eliminating gear backlash and new energy automobile discloses a solution to the impact generated during the starting process of an electric automobile, which applies a small torque to a motor when the automobile is stationary, which is insufficient to cause the automobile to move, thereby eliminating backlash in a transmission system. It is clear that this method only works when the vehicle is started and does not prevent the impact of the mechanical clearance, both during the running and during the stopping of the vehicle. The application of the method disclosed by the Chinese patent document, named as a speed control algorithm for solving the problem of jitter caused by mechanism clearance, is limited to the control process of starting from zero speed, accelerating, keeping constant speed, decelerating and finally ending at zero speed. The method has poor adaptability to load change and complex motion modes in the numerical control machine tool and is difficult to avoid impact and jitter.
Disclosure of Invention
The invention provides a system and a method for restraining clearance impact of a mechanical transmission system of a servo press in order to make up for the defects of the prior art.
The invention is realized by the following technical scheme:
a clearance impact suppression system of a mechanical transmission system of a servo press comprises a control system, wherein the control system is connected with a motor through a power cable; an output shaft of the motor is mechanically connected with the speed reducer and is provided with an encoder, and a signal output end of the encoder is electrically connected with the control system; the speed reducer is connected with the sliding block through a crank connecting rod mechanism.
The device also comprises a slide pressure sensor electrically connected with the control system.
A method for restraining the clearance impact of a mechanical transmission system of a servo press comprises the following steps:
s1, extracting data, wherein the data comprises driving side rotational inertia
The inertia of the load-side component is converted into the rotational inertia of the motor shaft
Motor driving torque
Actual measurement motor speed of current control period
And the measured motor speed of the previous control period
；
S2, calculating the angular acceleration of the motor in a clearance state
;
S3, calculating the actual angular acceleration of the motor
Wherein, in the step (A),
is the control cycle time;
s4, judging whether the transmission system is in a clearance state: if the actually measured angular acceleration of the motor is obviously smaller than that in the clearance state, that is to say
Judging that the transmission system is in a contact state; otherwise, judging that the transmission system is in a clearance state;
s5, output control: when the transmission system is judged to be in a clearance state, the control system limits the driving torque of the motor by limiting the maximum current output to the motor; and when the transmission system is judged to be in the contact state, the control system normally controls.
The above-mentionedStep S4, judging whether the transmission system is in the clearance state comprises S4-1 setting a threshold value
(ii) a S4-2, judging the state of the transmission system, and when the actually measured angular acceleration is smaller than the threshold value, judging that the actual angular acceleration is smaller than the threshold value
Then reliably obtain
To conclude that the transmission is in contact; otherwise, the transmission system is judged to be in a clearance state.
Threshold value in the step S4-1
Is determined by first calculating the angular acceleration of the motor when the drive train is in contact
Then by the formula
And (6) obtaining.
The data in the S1 extraction data also comprises the conversion of the pressure F to the load torque on the motor shaft
(ii) a Threshold value in the step S4-1
Is determined by first calculating the angular acceleration of the motor when the drive train is in contact
Then by the formula
And (6) obtaining.
The specific process of the step S5 of output control is to firstly define the maximum value of the angular acceleration of the clearance state as
Calculating the maximum torque
If the motor torque command obtained by the control system according to the gapless control algorithm is larger than the maximum value
Then command the motor to output only
Otherwise, the torque command is output as calculated.
The invention has the following beneficial effects:
1. the technical scheme utilizes the characteristics and the basic control principle of a transmission system of the servo press to realize the automatic identification of the clearance state of the transmission system, and limits the maximum angular acceleration of the servo motor in the clearance state to reduce the relative speed of a driving side and a load side, thereby inhibiting the impact.
2. The method has the advantages of simple principle, small calculation amount, low requirements on software and hardware of the control system and easy use.
3. The method requires only a few parameters of the mechanical system to be known and the parameters are readily available and therefore easy to implement.
4. The method aims at the general problem of the transmission system clearance, is not limited by the operation mode and the use occasion of equipment, has strong universality and can be applied to a servo press or other similar processing equipment.
5. The method can be used on the basis of the condition of the existing servo control equipment, any new hardware can be omitted, and only algorithm software needs to be added, so that the material cost is not brought to the upgrading and reconstruction of the existing equipment, and the method is simple, convenient and easy to implement.
7. The method greatly reduces the impact of the equipment, is particularly suitable for frequent acceleration and deceleration application occasions, can greatly reduce the field noise, reduces the abrasion of the equipment and prolongs the service life of the equipment.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic structural diagram of a mechanical transmission system gap impact suppression system of a servo press using a slide pressure sensor according to the present invention.
FIG. 2 is a schematic diagram of a mechanical drive train lash impact suppression system for a servo press of the present invention without the use of a ram pressure sensor.
FIG. 3 is a flow chart of a method for damping lash of a mechanical drive train of a servo press according to the present invention.
Detailed Description
The following is a description of an embodiment of the present invention, and it should be noted that the scope of the present invention is not limited to the following embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also included in the present invention.
Fig. 1 to 3 show an embodiment of the present invention. The embodiment provides a system and a method for restraining clearance impact of a mechanical transmission system of a servo press.
Fig. 1 shows a first embodiment of the system part of the present invention, which includes a motor connected to a control system through a power cable, the motor is a servo motor, and the control system supplies a required current to the motor through the power cable to drive the motor to generate a torque for rotation. The output shaft of the motor is mechanically connected with the speed reducer and is provided with an encoder, and the signal output end of the encoder is connected with the control system. The control system uses the encoder signals to calculate the rotational speed and angular acceleration of the motor. The speed reducer drives the sliding block to move up and down along the guide rail through the crank connecting rod mechanism, pressure is generated on a workpiece below the sliding block, and the pressure of the sliding block is measured through the sliding block pressure sensor and sent to the control system.
The method provided by the invention has the idea that whether the transmission system is in a clearance state or not is judged in real time in the servo control process. If the sliding block is in the clearance state, the motor is commanded to output smaller torque, so that the rotating speed difference between the driving side and the load side is limited, and the impact can be reduced, and the sliding block is driven by the crank-link mechanism to move up and down along the guide rail.
And the side close to the motor is a driving side, and the side close to the sliding block is a load side. Drive side moment of inertia of
The inertia of the load-side component is converted into the rotational inertia of the motor shaft
. The motor generates a driving torque of
. The sum of external forces (including forming force and friction) applied to the slide during operation is F, which is measured by a pressure sensor on the press. The pressure F is converted into a load torque on the motor shaft
. Parameter(s)
And
determined by the mechanical system as a known parameter. Parameter(s)
The servo motor control algorithm is obtained through calculation according to a motor control model and current and belongs to servo control process variables.
And calculating according to the measured value of the slide pressure. Therefore, the above parameters are all known quantities.
Because the crank connecting rod of the press is a nonlinear transmission mechanism, when the inertia and the stress of the slide block, namely the inertia and the pressure of a load-side part, are converted on a motor shaft, the size of the slide block can be periodically changed along with the change of a crank angle. The method takes the minimum value of the equivalent moment of inertia and the equivalent load torque under each crank angle. How to convert the load side inertia and the external force to the rotational inertia and the load torque on the motor shaft respectively is an industry basic method, and is not described herein.
First extracting the driving side moment of inertia
The inertia of the load-side component is converted into the rotational inertia of the motor shaft
Motor driving torque
The pressure F is converted into a load torque on the motor shaft
The way of extracting the variables has been described above.
Calculating the angular acceleration of the motor in a clearance state, namely when the gear of the speed reducer is in the clearance state:
(ii) a Because of the fact that
And
are known, so can be calculated at any time
。
Calculating the actual angular acceleration of the motor:
wherein the content of the first and second substances,
is the measured motor angular velocity of the current control period,
is the measured motor angular velocity of the last control period,
is the control cycle time.
And
measured by the encoder.
Judging whether the transmission system is in a clearance state: if the actually measured angular acceleration of the motor is obviously smaller than that in the clearance state, that is to say
If so, judging that the transmission system is in a contact state; otherwise, judging that the transmission system is in a clearance state; wherein
Is alpha _ m<alpha_T。
Further, in order to accurately judge the contact and clearance states, the angular acceleration of the motor when the transmission system is in the contact state, that is, the gears of the speed reducer are in the contact state, is calculated:
(ii) a The motor drives all the components and external loads on the driving side and the load side.
Because of the fact that
Is positive and located on a molecule, and
is positive number and is positioned in the denominator, and the combined action of the two inevitably leads the angular acceleration under the contact state to be smaller than the angular acceleration under the clearance state, namely
；
Setting a threshold value
So that when the actual angular acceleration is less than the threshold value
Can reliably derive
To conclude that the transmission is in contact; otherwise, judging that the transmission system is in a clearance state; wherein
。
And (3) output control:
when it is determined that the transmission system is in the lash state, the control system limits the drive torque of the motor by limiting the maximum current output to the motor. Specifically, first, the maximum value of the angular acceleration of the clearance state is defined as
Calculating the maximum torque
If the motor torque command obtained by the control system according to the gapless control algorithm is larger than the maximum value
Then command the motor to output only
Otherwise, output as the calculated torque command. By limiting the maximum output torque, the angular acceleration of the motor can be suppressed, so that the drive-side component does not reach a high relative speed when crossing the gap, and the impact at the moment of contact can be reduced.
And when the transmission system is judged to be in the contact state, the control system normally controls.
Fig. 2 shows a second embodiment of the system of the present invention, which is different from the first embodiment only in that the present embodiment does not have a slider pressure sensor, and accordingly, since the force applied to the slider is unknown, the angular acceleration of the motor in the contact state cannot be accurately calculated. However, if the load-side equivalent moment of inertia is large (accounting for 30% or more of the total) with respect to the drive side, the angular accelerations calculated in the two states can be made significantly different even without considering the load torque, and the backlash state can be reliably determined. At this time, the threshold formula of the angular acceleration is modified as follows:
wherein
The method comprises the following specific steps.
First extracting the driving side moment of inertia
The inertia of the load-side component is converted into the rotational inertia of the motor shaft
And motor drive torque
；
Calculating the angular acceleration of the motor in a clearance state, namely when the gear of the speed reducer is in the clearance state:
Calculating the actual angular acceleration of the motor:
wherein the content of the first and second substances,
is the measured motor angular velocity of the current control period,
is the measured motor angular velocity of the last control period,
is the control cycle time.
And
measured by the encoder.
Judging whether the transmission system is in a clearance state: if the actually measured angular acceleration of the motor is obviously smaller than that in the clearance state, that is to say
Then the transmission system can be judgedThe contact state is achieved, otherwise, the gap state of the transmission system is judged; wherein
Is alpha _ m<alpha_T。
Further, the angular acceleration of the motor is calculated when the transmission system is in a contact state, i.e. the gears of the reducer are in a contact state:
when the motor drives all the components and external loads on the driving side and the load side to move.
Setting a threshold value
So that when the actual angular acceleration is less than the threshold value
Can reliably derive
To conclude that the transmission is in contact; otherwise, judging that the transmission system is in a clearance state; wherein
；
And (3) output control: when it is determined that the transmission system is in the lash state, the control system limits the drive torque of the motor by limiting the maximum current output to the motor. Specifically, first, the maximum value of the angular acceleration of the clearance state is defined as
Calculating the maximum torque
If the motor torque command obtained by the control system according to the gapless control algorithm is larger than the maximum value
Then command the motor to output only
Otherwise, the torque command is output as calculated.
And when the transmission system is in the contact state, the control system normally controls.
After the device is assembled in the manner shown in fig. 1 or fig. 2, the control software in the control system executes the control program according to the flow cycle shown in fig. 3. Each cycle period is fixed in time. At each control cycle, the algorithm first reads in measured data from sensors internal and external to the control system, including motor current, motor encoder speed, and slider pressure. The motor angular acceleration in the gap state and the contact state is then calculated according to the aforementioned formula and known constants,
and
(or
) And calculating a gap state judgment threshold value
And simultaneously calculating the actual angular acceleration of the motor
. Finally, will
And
and comparing and judging whether the gap state exists or not. If the motor torque command is judged to be in the clearance state, the maximum value of the motor torque command output by the control system is limited, otherwise, the motor torque command is limited to the maximum valueThe raw torque command is directly output. After that, the control algorithm waits for the control period to end, and enters the next cycle, and the above operation is repeatedly executed.
Claims (5)
1. A method for restraining the clearance impact of a mechanical transmission system of a servo press is characterized by comprising the following steps:
s1, extracting data, wherein the data comprises a driving side moment of inertia J D The inertia of the load-side component is converted into the rotational inertia J on the motor shaft L Motor drive torque T D Actual measurement motor speed omega of current control period k And the measured motor speed omega of the previous control period k-1 ；
S2, calculating the angular acceleration of the motor in a clearance state
S3, calculating the actual angular acceleration of the motor
Where Δ t is the control cycle time;
s4, judging whether the transmission system is in a clearance state: if α is m ＜＜α D Judging that the transmission system is in a contact state; otherwise, judging that the transmission system is in a clearance state;
s5, output control: when the transmission system is judged to be in a clearance state, the control system limits the driving torque of the motor by limiting the maximum current output to the motor; when the transmission system is judged to be in a contact state, the control system normally controls;
the step S4 of judging whether the transmission system is in the clearance state comprises the step S4-1 of setting a threshold value alpha T (ii) a S4-2, judging the state of the transmission system, and when the actually measured angular acceleration of the motor is smaller than the threshold value, namely alpha is obtained m <α T Then, alpha is reliably obtained m ＜＜α D To conclude that the transmission is in contact; otherwise, judging that the transmission system is in a clearance state;
the steps areThreshold value α in step S4-1 T Is determined by first calculating the angular acceleration of the motor when the drive train is in contact
Then by the formula
And (6) obtaining.
2. The method for suppressing lash impact of a mechanical transmission system of a servo press as set forth in claim 1, wherein: the data in the S1 extraction data also comprises the load torque T converted from the pressure F to the motor shaft L (ii) a Threshold value alpha in the step S4-1 T Is determined by first calculating the angular acceleration of the motor when the drive train is in contact
Then by the formula
And (4) obtaining.
3. The method for suppressing lash impact of a mechanical transmission system of a servo press as claimed in any one of claims 1 to 2, wherein: the specific process of the output control in the step S5 is that firstly, the maximum value of the angular acceleration of the clearance state is defined as alpha S Calculating the maximum torque T S ＝α S ·J D If the motor torque command obtained by the control system according to the gapless control algorithm is larger than the maximum value T S Then command the motor to output only T S Otherwise, the torque command is output as calculated.
4. The method for restraining the mechanical transmission system clearance impact of the servo press according to claim 1, wherein the method is applied to a mechanical transmission system clearance impact restraining system of the servo press, and the mechanical transmission system clearance impact restraining system of the servo press comprises a control system which is connected with a motor through a power cable; an output shaft of the motor is mechanically connected with the speed reducer and is provided with an encoder, and a signal output end of the encoder is electrically connected with the control system; the speed reducer is connected with the sliding block through a crank connecting rod mechanism.
5. The mechanical drive train lash impact suppression system of a servo press as claimed in claim 1, wherein: the slider pressure sensor is electrically connected with the control system.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP3925842B2 (en) * | 2002-01-11 | 2007-06-06 | アイダエンジニアリング株式会社 | Press machine |
| CN100515749C (en) * | 2006-08-31 | 2009-07-22 | 东南大学 | Computer digital control system in use for AC servomotor to drive crank press directly |
| JP5476106B2 (en) * | 2009-12-07 | 2014-04-23 | アイダエンジニアリング株式会社 | Control method and control apparatus for electric servo press |
| JP5470223B2 (en) * | 2010-11-09 | 2014-04-16 | アイダエンジニアリング株式会社 | Servo press control device and control method |
| CN102107544B (en) * | 2010-12-21 | 2013-11-13 | 南京埃斯顿自动化股份有限公司 | Pressure control method for servo crank press |
| JP5560356B1 (en) * | 2013-02-12 | 2014-07-23 | コマツ産機株式会社 | Press machine and control method of press machine |
| JP5940106B2 (en) * | 2014-02-26 | 2016-06-29 | アイダエンジニアリング株式会社 | Servo press machine and control method of servo press machine |
| CN110143009B (en) * | 2019-05-21 | 2021-04-16 | 山东省科学院激光研究所 | Multi-point non-linear predictive control system of press |
| CN110682590A (en) * | 2019-10-31 | 2020-01-14 | 济宁科力光电产业有限责任公司 | Press machine full closed-loop control system and method based on limited control set sensorless |
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