CN113541529B - Position control method of laser terminal based on ultrasonic motor - Google Patents
Position control method of laser terminal based on ultrasonic motor Download PDFInfo
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- CN113541529B CN113541529B CN202110566714.9A CN202110566714A CN113541529B CN 113541529 B CN113541529 B CN 113541529B CN 202110566714 A CN202110566714 A CN 202110566714A CN 113541529 B CN113541529 B CN 113541529B
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- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/10—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing rotary motion, e.g. rotary motors
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Abstract
The invention relates to a position control method for laser terminal coarse pointing based on an ultrasonic motor, which adopts a position ring-speed ring combined control mode to drive a laser terminal coarse pointing mechanism when the pointing angle error of the laser terminal coarse pointing mechanism is more than or equal to a preset threshold; and when the pointing angle error of the laser terminal coarse pointing mechanism is smaller than a preset threshold, only adopting a position ring control mode to drive the laser terminal coarse pointing mechanism. The invention realizes the position control of the ultrasonic motor with high precision and high bandwidth under the state of extremely low rotating speed.
Description
Technical Field
The invention relates to a position control method of a laser terminal based on an ultrasonic motor, and belongs to the technical field of tracking and aiming.
Background
The laser communication pointing mechanism (CPA) is one of three core units (pointing mechanism, telescope and transceiver channel) of the laser communication terminal. The performance of the pointing mechanism directly influences the establishment of a communication link of the laser terminal, so that the success or failure of the whole laser communication is influenced. In order to realize the light weight of the laser terminal coarse pointing mechanism, the ultrasonic motor with higher energy density is adopted to replace the permanent magnet motor as a driving source for driving control, the weight of the motor is reduced, meanwhile, the design of a locking mechanism can be cancelled, and the weight of the coarse pointing mechanism is effectively reduced. The CPA has extremely low working rotating speed and extremely high tracking precision requirement, but the working rotating speed of the conventional ultrasonic motor control method is high, high-precision control at extremely low rotating speed cannot be realized, and a micro-stepping control method is required to be adopted for driving control. Therefore, a position control method of a laser terminal based on an ultrasonic motor needs to be provided to realize high-precision tracking pointing of a novel laser terminal.
When the coarse pointing mechanism of the laser terminal based on the ultrasonic motor carries out high-precision tracking control, the following problems are faced:
(1) The control of the conventional ultrasonic motor is basically frequency control, and can meet the speed control precision of more than 1 degree/s, while the control requirement of a coarse pointing mechanism is difficult to meet under the working speed of 0.001-1 degree/s.
(2) The command period is short (2 ms), and the micro-stepping control of the ultrasonic motor is related to the intermittent time, so that the control of extremely low rotating speed is difficult when the micro-stepping control is carried out.
(3) When micro-step position control is carried out, under the condition of large pulse, high rotating speed and torque can be obtained, but micro-vibration caused by the high rotating speed and the high torque affects the performance of an optical system.
(4) And the ultrasonic motor has the problem of difficult starting due to the material mechanism of the ultrasonic motor.
The documents of the traveling wave ultrasonic motor multi-regulation-amount coordination control method (chinese journal of motor engineering, 2009, volume 29, stage 6), "the ultrasonic motor ultra-low rotation speed control strategy based on multivariable variable speed integral (chinese journal of motor engineering, 2015, volume 30, stage 2)," the stepping characteristic and stepping positioning control of the ultrasonic motor (chinese journal of motor engineering, 2004, volume 24, stage 1), "the ultrasonic motor speed and positioning control system (chinese journal of motor engineering, 2005, volume 25, stage 1)," the two-degree-of-freedom rotation device driven by an ultrasonic motor in the patent, the ultrasonic motor ultra-low rotation speed control method in the patent, and the like respectively describe the low-speed control method of the ultrasonic motor and the position control method of the ultrasonic motor, but the control methods face difficulties in the position control of the laser terminal based on the ultrasonic motor, and mainly reflect that: (1) The problem of extremely high tracking precision position tracking at ultralow rotating speed is not solved by both a low-speed control method and a position control method of the ultrasonic motor; (2) The problem that the laser terminal is short in instruction period, static starting and micro-vibration is not involved.
Disclosure of Invention
The invention solves the technical problems that: the position control method of the laser terminal based on the ultrasonic motor is provided for overcoming the defects of the prior art and aiming at the problem that the existing ultrasonic motor cannot be controlled at the precision of 1 degree/s, and the position control of the ultrasonic motor at the high precision and the high bandwidth in the extremely low rotating speed state is realized.
The technical scheme of the invention is as follows: a laser terminal coarse pointing position control method based on an ultrasonic motor is characterized in that when the pointing angle error of a laser terminal coarse pointing mechanism is larger than or equal to a preset threshold, a position ring-speed ring combined control mode is adopted to drive the laser terminal coarse pointing mechanism; and when the pointing angle error of the laser terminal coarse pointing mechanism is smaller than a preset threshold, only adopting a position ring control mode to drive the laser terminal coarse pointing mechanism.
Preferably, the position loop-speed loop combined control mode is as follows:
the position ring-speed ring combined control mode is a common position control mode, speed ring closed-loop control is adopted as an inner ring, a position ring is an outer ring, the error between a position instruction and an actual position is used as input, a speed control instruction is obtained by PID control, and then the error between the speed control instruction and the actual speed is obtained by a speed controller to control the motor;
when the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a high-speed section, the speed ring adopts a continuous control mode to carry out position control; when the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a low-speed section, the speed ring adopts a micro-stepping mode to carry out position control; in the high-speed section, the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is greater than or equal to the rotating speed threshold, and in the low-speed section, the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is less than the rotating speed threshold.
Preferably, when the pointing angle error of the coarse pointing mechanism of the laser terminal is smaller than a preset threshold, the position loop control mode adopts a micro-stepping control mode for control.
Preferably, in the micro-stepping control mode, the step angle of the micro-stepping mode of the ultrasonic motor is controlled by adopting different frequency sections and different pulse numbers through the error range of the pointing angle of the coarse pointing mechanism of the laser terminal.
Preferably, the position control method based on the coarse pointing of the laser terminal of the ultrasonic motor further includes the following steps:
the laser terminal coarse pointing mechanism based on the ultrasonic motor is driven to start in a continuous mode, and in the starting process, the driving frequency is in a frequency conversion mode from high to low, so that the starting torque is continuously increased until the ultrasonic motor is started.
Acquiring the temperature of the ultrasonic motor, obtaining the frequency change delta f corresponding to the current temperature relative to the temperature change by using the known change relation curve of the resonant frequency of the ultrasonic motor and the temperature, and compensating the driving frequency of the ultrasonic motor by referring to the current temperature state:
the temperature compensation is as follows:
f driving frequency ＝f Driving frequency at room temperature +Δf
Wherein f is Driving frequency For compensated drive frequency, f Driving frequency at room temperature To the drive frequency before compensation.
Preferably, the change relation curve of the resonant frequency of the ultrasonic motor and the temperature is obtained by calibration.
Preferably, the preset threshold is 0.1-0.2 °. The rotational speed threshold is 1 DEG/s-3 DEG/s.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention adopts a sectional multivariable coordination composite control method, adopts different control methods and control parameters under different error conditions, and effectively improves the position tracking precision of the coarse pointing mechanism;
(2) The invention adopts a temperature compensation control strategy, reduces the influence of the temperature change of the space environment on the control performance based on the CPA of the ultrasonic motor, ensures the consistency of the performance of the same frequency and the same control method under different temperature environments, and brings great convenience for the application of the CPA based on the ultrasonic motor in the space environment;
(3) The control method adopts a position-speed control mode at large error, and the speed ring controls the characteristics of no micro-vibration and no noise at a high-speed section (more than 2 degrees/s) by using continuous mode frequency modulation, so that the micro-vibration of the coarse pointing mechanism at a higher rotating speed is effectively reduced;
(4) The control method adopts variable frequency starting in the starting process, overcomes the problem that the ultrasonic motor is static and is difficult to start, and improves the starting reliability.
(5) When the extremely high tracking precision (within 5 urad) is realized, the micro-vibration and the noise are effectively reduced, and the performance of the laser terminal based on the ultrasonic motor is greatly improved.
Drawings
FIG. 1 is a block diagram of a position-velocity control method of an embodiment of the present invention;
FIG. 2 is a block diagram of a control system according to an embodiment of the present invention;
FIG. 3 (a) is a trace of a laser coarse pointing mechanism using a conventional PID (0.23Hz, 0.2443 °/s) for a sinusoidal command;
FIG. 3 (b) is a tracking curve (0.23Hz, 0.2443 °/s) of the laser coarse pointing mechanism to the sine command using the control method of the present invention;
FIG. 3 (c) is a plot of the tracking error for a sinusoidal command using a conventional PID laser coarse pointing mechanism (0.23Hz, 0.2443 °/s);
FIG. 3 (d) is a tracking error curve (0.23Hz, 0.2443 °/s) of the laser coarse pointing mechanism for the sinusoidal command using the control method of the present invention;
FIG. 4 (a) is a diagram showing the micro-vibration of the coarse pointing device according to the control method of the present invention (tracking command is 0.23Hz,0.2443 °/s);
FIG. 4 (b) is a plot of the micro-vibrations of the coarse pointing mechanism between conventional control methods (tracking command 0.23Hz,0.2443 deg./s).
Detailed Description
The invention is further illustrated by the following examples.
As shown in fig. 1, the laser terminal coarse pointing mechanism is a structure in which the laser terminal coarse pointing mechanism adopts a common theodolite type, a driving source adopts a traveling wave type ultrasonic motor, and feedback adopts a 26-bit reflective grating.
The position loop-speed loop control mode is a common position control mode, and adopts speed loop closed-loop control as an inner loop and a position loop as an outer loop, as shown in fig. 1. The method takes the error between the position command and the actual position as input, obtains a speed control command by using PID control, and obtains a motor control quantity control motor by the error between the speed control command and the actual speed through a speed controller.
The ultrasonic motor control is mainly divided into a continuous mode and a micro-stepping mode, wherein the continuous mode realizes the control of the rotating speed and the position by taking frequency as a control variable, and the micro-stepping mode realizes the control of the rotating speed and the position of the motor in a stepping mode by taking variables such as pulse number, frequency and the like.
The invention abandons the control of a speed ring, provides a position control method based on a traveling wave ultrasonic motor laser terminal coarse pointing mechanism, and the control block diagram is shown in figure 2, and the composite control method comprises the following steps:
(1) The laser terminal coarse pointing mechanism based on the ultrasonic motor is driven in a continuous mode (the frequency is used as a control variable to realize rotating speed and position control) in the starting process of the laser terminal coarse pointing mechanism based on the ultrasonic motor, the frequency conversion starting mode that the driving frequency is continuously reduced (the driving frequency is closer to the resonant frequency of the ultrasonic motor, the larger the moment is), the starting moment is continuously increased until the motor is started, the problem that the ultrasonic motor is difficult to start due to long-time placement is solved, and the high-reliability starting of the ultrasonic motor is realized.
(2) And when the pointing angle error of the laser terminal coarse pointing mechanism is greater than or equal to a preset threshold, the threshold is 0.1 degrees, the laser terminal coarse pointing mechanism is driven in a position ring-speed ring combined control mode, stable control of a laser terminal double shaft on a target is realized, and stepping oscillation caused by position ring control under large error is prevented. When the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a high-speed section (more than or equal to 2 DEG/s), the speed ring controller adopts a continuous control mode (only frequency is used as a control quantity) to carry out position control; when the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a low-speed section (below 2 DEG/s), a micro-stepping mode (micro-amplitude stepping motion with frequency, pulse number and the like as control variables) is adopted for position control, and the defect that the continuous mode cannot be used for low-speed control is overcome.
The speed control mode is as follows:
the operating rotational speeds of the azimuth axis and the pitch axis of the laser terminal coarse pointing to the terminal are both 0.001 DEG/s-5 DEG/s, so that 2 DEG/s or less is divided into a low speed section and 2 DEG/s or more is divided into a high speed section.
(3) When the pointing angle error of the laser terminal coarse pointing mechanism is smaller than a preset threshold, the laser terminal coarse pointing mechanism is driven only in a position loop control mode, the control mode is micro-step control, and the defect that an ultrasonic motor cannot perform accurate position control is overcome (in the ultrasonic motor, the frequency, the pulse number and the position are not in a complete linear relation). The control mode is as follows: adopt the size of the little step mode step angle of different frequency section different pulse numbers control ultrasonic motor through the big or small scope of error, effectively promote coarse pointing mechanism's position tracking precision, specifically as follows:
in a specific embodiment of the invention, when the error is large (more than 500 urad), 35.2kHz driving frequency is adopted, and the PID control pulse range is 4-40;
when the error is larger than 200urad, 35.6kHz driving frequency is adopted, and the PID control pulse range is 4-40;
when the error is small (more than 50 urad), 36kHz driving frequency is adopted, and the PID control pulse range is 4-40.
The invention effectively improves the position tracking precision of the coarse pointing mechanism by the coordinated control of frequency and pulse number at a low-speed stage; the continuous mode frequency modulation is used for controlling the continuity in the high-speed section, so that the micro-vibration of the coarse pointing mechanism at a high rotating speed is effectively reduced, and the position tracking precision and the balance control of the micro-vibration are realized.
(4) In order to compensate the influence of the self temperature change of the ultrasonic motor on the dynamic performance of the ultrasonic motor, the temperature of the ultrasonic motor is collected by adopting a thermistor and an AD (analog-digital) module, the driving frequency of the ultrasonic motor is compensated by referring to the current temperature state by utilizing the relation between the change of the resonant frequency of the ultrasonic motor and the temperature, the influence of the temperature change on the ultrasonic motor is reduced, and the constancy of the driving torque of the ultrasonic motor with the same frequency at different temperatures is ensured. The temperature compensation is as follows:
f driving frequency ＝f Driving frequency at ambient temperature +Δf
Wherein, the delta f is obtained by a change relation curve of the resonant frequency of the ultrasonic motor and the temperature and can be obtained by calibration; the drive frequency corresponding to the change in the resonant frequency also changes accordingly, so that Δ f is applied to the drive frequency to compensate.
In order to verify the effectiveness of the control method, the traditional position control method and the control method are compared with each other according to test results. As can be seen from fig. 3 (a) - (d) and fig. 4 (a) - (b), compared with the conventional control method, the tracking accuracy of the azimuth axis and the pitch axis of the laser terminal coarse pointing terminal using the control method of the present invention is reduced from 60 μ rad to 10 μ rad, the micro-vibration amplitude is also reduced by about 60% (the tracking accuracy and the micro-vibration comparison result are shown in the following figure), and the control noise is reduced from 68.8Db to 48.5Db (the result measured by a professional acoustic measuring instrument).
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Claims (7)
1. A laser terminal coarse pointing position control method based on an ultrasonic motor is characterized in that when the pointing angle error of a laser terminal coarse pointing mechanism is larger than or equal to a preset threshold, a position ring-speed ring combined control mode is adopted to drive the laser terminal coarse pointing mechanism; when the pointing angle error of the laser terminal coarse pointing mechanism is smaller than a preset threshold, only adopting a position ring control mode to drive the laser terminal coarse pointing mechanism;
the position ring-speed ring combined control mode is as follows:
the position ring-speed ring combined control mode adopts speed ring closed-loop control as an inner ring and adopts a position ring as an outer ring, the error between a position instruction and an actual position is used as input, a PID control method is used for obtaining a speed control instruction, and then the error between the speed control instruction and the actual speed is obtained through a speed controller to obtain a motor control quantity control motor;
when the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a high-speed section, the speed ring adopts a continuous control mode to carry out position control; when the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is in a low-speed section, the speed ring adopts a micro-stepping mode to carry out position control; in the high-speed section, the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is greater than or equal to a rotating speed threshold, and in the low-speed section, the working rotating speed of the laser terminal coarse pointing terminal rotating shaft is less than the rotating speed threshold;
and when the pointing angle error of the laser terminal coarse pointing mechanism is smaller than a preset threshold, the position ring control mode adopts a micro-stepping control mode for control.
2. The position control method for the laser terminal coarse pointing based on the ultrasonic motor as claimed in claim 1, characterized in that the micro-step control mode controls the step angle of the ultrasonic motor micro-step mode by adopting different frequency segments and different pulse numbers through the range of the pointing angle error of the laser terminal coarse pointing mechanism.
3. The position control method for the laser terminal coarse pointing based on the ultrasonic motor according to any one of claims 1, characterized by further comprising the following steps:
the laser terminal coarse pointing mechanism based on the ultrasonic motor is driven to start in a continuous mode, and in the starting process, the driving frequency is in a frequency conversion mode from high to low, so that the starting torque is continuously increased until the ultrasonic motor is started.
4. The position control method for the laser terminal coarse pointing based on the ultrasonic motor according to claim 1, characterized in that:
acquiring the temperature of the ultrasonic motor, obtaining the frequency change delta f corresponding to the current temperature relative to the temperature change by using the known change relation curve of the resonant frequency of the ultrasonic motor and the temperature, and compensating the driving frequency of the ultrasonic motor by referring to the current temperature state:
the temperature compensation is as follows:
f driving frequency ＝f Driving frequency at ambient temperature +Δf
Wherein f is Driving frequency For compensated drive frequency, f Driving frequency at room temperature To compensate for the previous drive frequency.
5. The position control method for the coarse pointing of the laser terminal based on the ultrasonic motor as claimed in claim 4, wherein a curve of a change relation between the resonant frequency of the ultrasonic motor and the temperature is obtained by calibration.
6. The position control method for the coarse pointing of the laser terminal based on the ultrasonic motor as claimed in claim 1, wherein the preset threshold is 0.1-0.2 °.
7. The position control method for the laser terminal coarse pointing based on the ultrasonic motor according to claim 1, characterized in that the rotation speed threshold is 1 °/s-3 °/s.
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| CN100570283C (en) * | 2005-06-29 | 2009-12-16 | 精工爱普生株式会社 | Drive amout detection device of piezoelectric actuator and electronic equipment |
| JP4825600B2 (en) * | 2006-06-28 | 2011-11-30 | 株式会社東芝 | Motor control device |
| CN101478262A (en) * | 2008-09-24 | 2009-07-08 | 南京航空航天大学 | Speed-position dual close-loop control scheme for ultrasonic motor |
| CN104272159B (en) * | 2012-02-28 | 2016-11-02 | 株式会社尼康 | Driving means, driving method and optical device |
| CN103529858A (en) * | 2013-10-11 | 2014-01-22 | 北京航空航天大学 | Position closed-loop system-based minimum phase difference tracking method |
| CN104038100B (en) * | 2014-06-25 | 2016-04-06 | 哈尔滨工业大学 | What realize based on polypody rotary piezoelectric driver drives motivational techniques across yardstick |
| CN108233815B (en) * | 2018-01-23 | 2020-09-04 | 北京信息科技大学 | Control method of voice coil motor high-speed precise light beam pointing system based on PWM |
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