CN112994567A - Motor control method and motor control device without current sensor, and servo device - Google Patents
Motor control method and motor control device without current sensor, and servo device Download PDFInfo
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- CN112994567A CN112994567A CN202110488272.0A CN202110488272A CN112994567A CN 112994567 A CN112994567 A CN 112994567A CN 202110488272 A CN202110488272 A CN 202110488272A CN 112994567 A CN112994567 A CN 112994567A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/0003—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/06—Rotor flux based control involving the use of rotor position or rotor speed sensors
Abstract
The invention relates to a motor control method, a motor control device and a servo device of a currentless sensor, wherein the method comprises the following steps: according to the obtained real position of the rotor of the servo motorθCalculating the true rotation speed of the servo motorv(ii) a Comparing true locationsθAnd a set positionθ *Obtaining the position difference value, and obtaining the speed set value through PI controlv *(ii) a Given value of speedv *With true speed of rotationvObtaining a rotation speed difference value by difference making and obtaining the rotation speed difference value through PI controlqShaft voltageu q (ii) a For the current real positionθPerforming trigonometric function calculation to obtain trigonometric function valueu d =0, voltageu q And voltageu d Transforming to obtain voltage vector on static coordinate systemMeasurement ofU a 、U b 、U c (ii) a Comparing voltage vectorsU a 、U b 、U c And a triangular wave; and generating six paths of PWM control signals for driving the servo motor to work according to the comparison result. The device is realized by FPGA, and a magnetic powder brake and a flywheel are added. The invention improves the low-rotating-speed stability and the positioning control precision of the servo motor.
Description
Technical Field
The invention belongs to the technical field of motor control, relates to a servo motor control technology, and particularly relates to a motor control method, a motor control device and a servo device without a current sensor.
Background
In an automatic control system, a system in which an output quantity can be changed with a certain degree of accuracy following a change in an input quantity is called a servo system, and the servo system is composed of a servo drive device and a drive element (i.e., a servo motor). In recent years, with the development of control theory and electronic technology, servo systems have been widely used in the fields of daily life, aerospace, weaponry, and the like.
For some special application scenes (such as space load servo, space antenna orientation and the like), a servo system needs to run at a low rotating speed and a light load for a long time, and the requirements on the rotating speed and the positioning control precision of a motor are high. However, in the low-speed and light-load mode, the load torque of the motor is switched back and forth between the static friction torque and the dynamic friction torque, so that the load torque presents strong nonlinearity, and the speed fluctuation phenomenon of 'stagnation-slippage' of the motor is easily caused. Meanwhile, the permanent magnet flux linkage of the motor rotor and the stator tooth slot interact to generate tooth slot torque, so that the fluctuation of the rotating speed is further intensified. Therefore, the nonlinear friction and the motor cogging torque are key factors influencing the rotating speed stability of the low-speed servo system, and must be considered with great importance. In addition, in aerospace applications, to ensure the reliability of the servo system, the current sensor is generally very expensive to manufacture, and has strict requirements on the volume and power consumption of the servo system. The reference is made to the literature "Kang GH, Son YD, Kim GT, Hur J: A Novel coding Torque Reduction Method for interor-Type Permanent-Magnet Motor. IEEE Transactions on Industry Applications 2009, 45: 161-7", and the existing ultra-low speed special motor needs to be optimized in motor structure, so that the production cost is high and the universality is poor. From the viewpoint of reducing cost and satisfying the demands for miniaturization and low power consumption of products, it is necessary to optimize a motor control method and apparatus.
The chinese patent application with publication number CN110855204A discloses a device and a method for controlling torque periodic pulsation suppression of a permanent magnet synchronous motor, and in particular discloses a method for compensating a set value of a torque current by using an iterative learning controller, aiming at the problem that the iterative learning controller needs to optimize a plurality of parameters, the application adopts an improved particle swarm optimization algorithm to automatically optimize the controller parameters, thereby achieving a certain torque pulsation suppression effect. The disadvantages are that: although the patent application has better control performance for periodic disturbance, the control effect of the patent application is poor for non-linear disturbance, such as non-linear friction.
The Chinese patent application with the publication number of CN111416560A discloses a permanent magnet synchronous motor control method and system without a current sensor, which adopts a control module without a current sensor and is based on a motor modelqShaft voltage anddthe shaft voltage is estimated, the rotating speed and the electric angular speed are obtained through the position sensor, the estimated current value is more stable, anddshaft andqwhen the actual current of the shaft reaches a steady state, the estimated current can be quickly converged to the actual current, and the method is suitable for the field in which the control frequency of an outer ring (such as a speed ring or a position ring) is far lower than that of an inner ring and the requirement on force control precision is high. Although the patent application can reduce the system cost, the calculation amount is large, and the hardware resources are highThe current value is required and estimated with a certain error.
The method is characterized in that a DSP-based permanent magnet synchronous motor control system hardware design [ J ]. manufacture automation 2019, 41:118-20 ] is adopted as a core processor by a digital signal processor TMS320F28335 of TI company, a hardware system of the permanent magnet synchronous motor control system is designed, and effective control of the position, the rotating speed, the acceleration and the output torque of the permanent magnet synchronous motor is realized. The scheme is a permanent magnet synchronous motor control scheme widely adopted at present, and has the following defects: for a satellite-borne application environment, the reliability of a DSP processor is low due to a single event upset phenomenon, and a conventional DSP-based permanent magnet synchronous motor control framework is difficult to adapt to a space environment.
The aerospace-level antifuse FPGA has good radiation resistance, and a literature report for realizing the control of the permanent magnet synchronous motor by adopting the FPGA is reported at present, such as a literature 'Liyaar', the design and realization of a permanent magnet synchronous motor controller based on the FPGA [ J ]. electronic technology and software engineering, 2016(11): 110-. But the prior method has the defects that: most of the existing FPGA permanent magnet synchronous motor control schemes are that a DSP motor control framework is transplanted to an FPGA platform, so that the calculation amount is large, and the occupied resources are large.
Disclosure of Invention
Aiming at the problems of poor control precision and the like of the existing method, the invention provides a motor control method without a current sensor, a motor control device and a servo device, which can realize low-rotation-speed control and positioning control of a motor, reduce the performance requirement of the motor and improve the control precision of the rotation speed stability and the rotor position of the motor.
In order to achieve the above object, the present invention provides a motor control method without a current sensor, which comprises the following steps:
a position information acquisition step: obtaining a true position of a rotor of a servo motorθ；
A speed calculation step: according to the true positionθCalculating the true rotation speed of the servo motorv;
Position ofThe control steps are as follows: will be true positionθAnd a set positionθ *Comparing to obtain a position difference value, and obtaining a speed given value by the position difference value through PI controlv *；
And a rotating speed control step: setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
Three-phase duty ratio operation: magnetic field orientation of servo motor rotor under conventional conditionsd-qThe transformation formula of the coordinate system and the static coordinate system is as follows:
in the formula (I), the compound is shown in the specification,u d is a statordThe current component of the shaft is such that,u q is a statorqThe current component of the shaft is such that,θis the angle of the rotor of the motor,U a 、U b 、U c respectively are three-phase sine modulation wave voltage vector values;
order tou d =0, obtained from formula (1):
obtaining a voltage vector on a stationary coordinate system from the formula (2)U a 、U b 、U c ；
A comparison step: vector of voltageU a 、U b 、U c Comparing with the triangular wave;
a drive signal generation step: and generating six paths of PWM control signals for driving the servo motor to work according to the result in the comparison step.
Further, the method also comprises a position information processing step: acquiring the real position acquired in the step of acquiring the position information according to the communication protocolθAnd (5) carrying out a digital system conversion treatment.
Preferably, in the velocity calculation processing step, the velocity is calculated based on the true positionθCalculating the real rotation speed of the servo motor by adopting a difference methodv。
Preferably, in the position control step, the position is set when the servo motor adopts a rotation speed control modeθ *=ṽ * tWherein, in the step (A),ṽ *in order to achieve the desired set rotational speed,tthe operation time of the servo motor is set; when the servo motor adopts a position control mode, setting the positionθ *I.e. the angular position that is expected to be reached.
In order to achieve the above object, the present invention further provides a motor control device for implementing the motor control method without a current sensor, including:
a position sensor mounted at the tail end of the main shaft of the servo motor for acquiring the real position of the rotor of the servo motorθ；
A speed calculation unit connected with the position sensor and used for calculating the speed according to the real positionθCalculating the true rotation speed of the servo motorv；
A position controller connected with the position sensor for calculating the set positionθ *With the true positionθBy calculation of a PI control algorithm to produce a given speed valuev *；
A rotation speed controller respectively connected with the position controller and the speed arithmetic unit and used for setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
A three-phase duty ratio operation unit connected with the rotation speed controller and used for controlling the rotation speed of the motoru d According to voltage under the condition of =0u q Calculating a voltage vector on a stationary coordinate systemU a 、U b 、U c ；
A triangular wave generating unit for generating a triangular wave;
a comparator respectively connected with the three-phase duty ratio operation unitConnected to the triangular wave generating unit for comparing the voltage vectorsU a 、U b 、U c And a triangular wave;
and the driving signal generating unit is connected with the comparator and used for generating six paths of PWM control signals for driving the servo motor to work according to the comparison result.
Further, the system also comprises a position information processing unit connected with the position sensor and used for acquiring the real position according to a communication protocolθAnd the speed arithmetic unit and the position controller are connected with the position sensor through the position information processing unit.
The device further comprises an FPGA, wherein the speed operation unit, the position controller, the rotating speed controller, the three-phase duty ratio operation unit, the triangular wave generation unit, the comparator, the driving signal generation unit and the position information processing unit are all arranged in the FPGA.
Furthermore, a trigonometric function processing unit, a clock management unit and an external data interaction unit which is respectively connected with the speed operation unit and the position information processing unit are also arranged in the FPGA, and the trigonometric function processing unit is connected with the position information processing unit and the three-phase duty ratio operation unit and is used for carrying out trigonometric function calculation on the current real position to obtain a trigonometric function value; the clock management unit is used for generating a clock, a sampling clock and a reset signal required by the motor control device; the external data interaction unit is connected with an upper computer, receives an instruction of the upper computer and outputs the rotating speed and the position information of the motor to the upper computer.
The power module supplies power to the FPGA, and the driving module is connected between the drive generation unit and the servo motor and used for amplifying the power of the six paths of PWM control signals generated by the drive generation unit and driving the servo motor to work.
In order to achieve the above object, the present invention further provides a servo apparatus, comprising:
fixing a bracket;
the servo motor is arranged on the fixed bracket;
the magnetic powder brake is arranged on the fixed support and arranged above the servo motor, and the main shaft of the magnetic powder brake is parallel to the main shaft of the servo motor;
the first gear is arranged on a main shaft of the servo motor;
the second gear is arranged on the main shaft of the magnetic powder brake and is meshed with the first gear;
the flywheel is arranged on the motor output shaft of the servo motor, arranged on the outer side of the first gear and connected with the main shaft of the servo motor;
and a motor control device using the motor control device.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) the invention adoptsdAnd the control strategy that the shaft voltage is equal to zero only adopts the double closed-loop control of a rotating speed loop and a position loop to realize the high-precision rotating speed control and the motor positioning control of the servo motor.
(2) The invention can meet the calculation requirement of the motor control device only by adopting the single FPGA, thereby reducing the cost of the servo system, reducing the volume of the equipment and improving the reliability.
(3) The servo device provided by the invention can generate constant load moment by magnetic powder braking, and can increase the rotational inertia of the motor rotor through the flywheel, thereby improving the rotational speed stability of the motor during low-speed operation. By applying external load moment, the working point of the motor is changed, and the phenomenon of 'stagnation-slippage' caused by friction force in low-speed operation is weakened, so that the common servo motor can also achieve higher servo control precision.
Drawings
Fig. 1 is a control schematic diagram of a motor control method of a currentless sensor according to an embodiment of the present invention;
FIG. 2 is a diagram of a motor control apparatus according to an embodiment of the present inventiond-qA schematic diagram of an axis current simulation result;
FIG. 3 is a diagram illustrating a simulation result of a rotational speed control mode of the servo apparatus according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a simulation result of a position control mode of a servo apparatus according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a motor control device according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a servo apparatus according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating experimental results of a rotational speed control mode of the servo apparatus according to an embodiment of the present invention;
FIG. 8 is a schematic diagram illustrating experimental results of a position control mode of the servo apparatus according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of an ultra-low speed response curve of a servo device according to an embodiment of the present invention and a servo device not employing the servo device of the present invention.
In the figure, 1, a fixed bracket, 2, a servo motor, 3, a magnetic powder brake, 4, a first gear, 5, a second gear, 6, a flywheel, 7, a motor output shaft, 8, a position sensor, 9, a magnetic powder brake, a magnetic,qAxial current, 10,dThe shaft current.
Detailed Description
The invention is described in detail below by way of exemplary embodiments. It should be understood, however, that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Example 1: referring to fig. 1, the present embodiment provides a method for controlling a motor without a current sensor, which includes the following specific steps:
(1) a position information acquisition step: obtaining a true position of a rotor of a servo motorθ；
(2) A speed calculation step: according to the true positionθCalculating the true rotation speed of the servo motorv；
(3) A position control step: will be true positionθAnd a set positionθ *Comparing to obtain a position difference value, and obtaining a speed given value by the position difference value through PI controlv *；
(4) And a rotating speed control step: setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
(5) Three-phase duty ratio operation: magnetic field orientation of servo motor rotor under conventional conditionsd-qThe transformation formula of the coordinate system and the static coordinate system is as follows:
in the formula (I), the compound is shown in the specification,u d is a statordThe current component of the shaft is such that,u q is a statorqThe current component of the shaft is such that,θis the angle of the rotor of the motor,U a 、U b 、U c respectively are three-phase sine modulation wave voltage vector values;
order tou d =0, obtained from formula (1):
obtaining a voltage vector on a stationary coordinate system from the formula (2)U a 、U b 、U c ；
(6) A comparison step: vector of voltageU a 、U b 、U c Comparing with the triangular wave;
(7) a drive signal generation step: and generating six paths of PWM control signals for driving the servo motor to work according to the result in the comparison step.
Specifically, the control method further includes a position information processing step of: acquiring the real position acquired in the step of acquiring the position information according to the communication protocolθAnd (5) carrying out a digital system conversion treatment. Before the speed calculation step and the position control step are performed, the position information is processed and converted into data required for position control and speed calculation.
Specifically, in the speed calculation step, the real position is calculated according to the real positionθCalculating the real rotation speed of the servo motor by adopting a difference methodv. Specifically, the true position is acquired according to every two adjacent timesθCalculating the real rotating speed of the servo motor by taking the difference and dividing the difference by the sampling timev。
Specifically, in the position control step, when the servo motor adopts a rotating speed control mode, the position is setθ *=ṽ * tWherein, in the step (A),ṽ *in order to achieve the desired set rotational speed,tthe operation time of the servo motor is set; when the servo motor adopts a position control mode, setting the positionθ *I.e. the angular position that is expected to be reached.
The simulation is carried out by adopting the control method of the embodiment, and referring to fig. 2, it can be seen thatu d When the value is not less than 0, the reaction time is not less than 0,i d the current is also approximately 0A, demonstrating the effectiveness of the control method described in this example. FIG. 3 shows the control of the rotational speedṽ *Motor speed response curve at 360 °/s, fig. 4 shows the set position in the position control modeθ *The response curve of the angular position of the motor when =180 °, as can be seen from fig. 3 and 4, the control method described in this embodiment can realize high-precision rotation speed and position control.
The method comprises the following steps of (1) carrying out mathematical modeling on a motor based on a rotor magnetic field orientation d-q coordinate system:
obtaining:
in the formula (I), the compound is shown in the specification,ψ m is a permanent magnet flux linkage, and is provided with a permanent magnet,Lis a statordThe current component of the shaft is the armature inductance,i d is a statordThe current component of the shaft is such that,i q is a statorqThe current component of the shaft is such that,Ris a resistor of a stator of the motor,ωis the motor speed.
As a motor resistorRSufficiently large and inductiveLTaking for enough hoursLs0, and then:
as can be seen from the formula (6),u d andi d approximately in a proportional relationship, i.e.u d When the value is not less than 0, the reaction time is not less than 0,i d also 0. The control method of the embodiment adoptsdThe control strategy of shaft voltage equal to zero only adopts the control of double closed-loop control of rotating speed loop control and position loop controlqShaft voltageu q The output torque of the motor can be adjusted, the decoupling control of the motor is realized, and the high-precision rotating speed control and the motor positioning control of the servo motor are realized.
Example 2: referring to fig. 5, the present embodiment provides a motor control apparatus for implementing the motor control method of the currentless sensor according to embodiment 1, including:
a position sensor mounted at the tail end of the main shaft of the servo motor for acquiring the real position of the rotor of the servo motorθ；
A speed calculation unit connected with the position sensor and used for calculating the speed according to the real positionθCalculating the true rotation speed of the servo motorv；
A position controller connected with the position sensor for calculating the set positionθ *With the true positionθBy calculation of a PI control algorithm to produce a given speed valuev *；
A rotation speed controller respectively connected with the position controller and the speed arithmetic unit and used for setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
A three-phase duty ratio operation unit connected with the rotation speed controller and used for controlling the rotation speed of the motoru d According to voltage under the condition of =0u q Calculating a voltage vector on a stationary coordinate systemU a 、U b 、U c ；
A triangular wave generating unit for generating a triangular wave;
a comparator connected with the three-phase duty ratio operation unit and the triangular wave generation unit respectively for comparing the voltage vectorsU a 、U b 、U c And a triangular wave;
and the driving signal generating unit is connected with the comparator and used for generating six paths of PWM control signals for driving the servo motor to work according to the comparison result.
It should be noted that the comparator outputs the comparison result to the driving signal generating unit in the form of a binary code.
In this embodiment, the servo motor is a permanent magnet synchronous motor.
With continued reference to fig. 5, the motor control apparatus further includes a position information processing unit connected to the position sensor, for collecting the actual position according to a communication protocolθAnd the speed arithmetic unit and the position controller are connected with the position sensor through the position information processing unit. Before the speed calculation and the position control, the position information is processed by the position information processing unit and converted into data required by the position controller and the speed calculation unit.
With reference to fig. 5, the motor control device further includes an FPGA, and the speed operation unit, the position controller, the rotational speed controller, the three-phase duty operation unit, the triangular wave generation unit, the comparator, the driving signal generation unit, and the position information processing unit are all disposed in the FPGA. The method combines the characteristics of the FPGA to control, can meet the calculation requirement of the motor control device through the single FPGA, reduces the cost of a servo system, reduces the volume of equipment and improves the reliability.
Specifically, a trigonometric function processing unit, a clock management unit and a clock management unit are arranged in the FPGA respectivelyAnd the speed operation unit and the position information processing unit are connected with an external data interaction unit. The trigonometric function processing unit is connected with the position information processing unit and the three-phase duty ratio operation unit, is used for carrying out trigonometric function calculation on the current real position to obtain a trigonometric function value, sending the obtained trigonometric function value to the three-phase duty ratio operation unit, and is used for voltage vector calculationU a 、U b 、U c The step of trigonometric function calculation is as follows: and calculating a sine and cosine value corresponding to the current real position. The clock management unit is used for generating a clock, a sampling clock and a reset signal required by the motor control device; the external data interaction unit is connected with an upper computer, receives an instruction of the upper computer and outputs the rotating speed and the position information of the motor to the upper computer. It should be noted that the FPGA communicates with the upper computer through the serial port to complete data exchange, and man-machine exchange can be realized through data monitoring software in the upper computer to monitor the FPGA.
The motor control device further comprises a power module and a driving module, wherein the power module supplies power to the FPGA, and the driving module is connected between the drive generation unit and the servo motor and used for amplifying the power of the six paths of PWM control signals generated by the drive generation unit and driving the servo motor to work. Specifically, drive module includes drive circuit and the three-phase full-bridge inverter circuit who comprises 6 IGBT, receives 6 way PWM control signal through drive circuit, with signal isolation amplify the back and carry to the three-phase full-bridge inverter circuit again, control switching on and turn-off of IGBT among the three-phase full-bridge inverter circuit, become three-phase alternating voltage with direct current voltage contravariant by the three-phase full-bridge inverter circuit to driving motor moves.
Specifically, in the present embodiment, the position sensor employs an absolute encoder or an incremental encoder, and may communicate by using SSI protocol, BSSI protocol, EnDat protocol, HIPERFACE protocol, or the like.
In addition, in this embodiment, the parameter setting of the position controller and the rotational speed controller may use a zero pole configuration method, but is not limited to the zero pole configuration method, and may also be other setting methods such as a critical ratio and a relay feedback setting method.
In the motor control device of the embodiment, the real position of the rotor of the servo motor is acquired through the position sensorθ(ii) a The speed arithmetic unit is based on the real positionθCalculating the true rotation speed of the servo motorv(ii) a The position controller calculates the set positionθ *With the true positionθBy calculation of a PI control algorithm to produce a given speed valuev *(ii) a The speed controller gives a given value of speedv *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q (ii) a Three-phase duty ratio operation unit inu d According to voltage under the condition of =0u q Calculating a voltage vector on a stationary coordinate systemU a 、U b 、U c (ii) a Generating a triangular wave by a triangular wave generating unit; comparing voltage vectors by means of comparatorsU a 、U b 、U c And a triangular wave; and the driving signal generating unit generates six paths of PWM control signals for driving the servo motor to work according to the comparison result, so that the servo motor is controlled.
In this embodiment, the motor control device adoptsdAnd the control strategy that the shaft voltage is equal to zero only adopts the double closed-loop control of a rotating speed loop and a position loop to realize the high-precision rotating speed control and the motor positioning control of the servo motor.
Example 3: referring to fig. 5 and 6, the present embodiment provides a servo apparatus, including:
a fixed bracket 1;
the servo motor 2 is arranged on the fixed support 1;
the magnetic powder brake 3 is arranged on the fixed support 1 and arranged above the servo motor 2, a main shaft (namely an X1 shaft) of the magnetic powder brake is parallel to a main shaft (namely an X2 shaft) of the servo motor 2, and an X1 shaft and an X2 shaft are perpendicular to and intersected with a Y shaft;
a first gear 4 mounted on a main shaft of the servo motor 2;
the second gear 5 is arranged on the main shaft of the magnetic powder brake 3 and is meshed with the first gear 4;
the flywheel 6 is arranged on a motor output shaft 7 of the servo motor 2, arranged on the outer side of the first gear 4 and connected with a main shaft of the servo motor 2;
a motor control device comprising:
a position sensor 8 arranged at the tail end of the main shaft of the servo motor 2 and used for acquiring the real position of the rotor of the servo motorθ；
A speed calculation unit connected with the position sensor and used for calculating the speed according to the real positionθCalculating the true rotation speed of the servo motorv；
A position controller connected with the position sensor for calculating the set positionθ *With the true positionθBy calculation of a PI control algorithm to produce a given speed valuev *；
A rotation speed controller respectively connected with the position controller and the speed arithmetic unit and used for setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
A three-phase duty ratio operation unit connected with the rotation speed controller and used for controlling the rotation speed of the motoru d According to voltage under the condition of =0u q Calculating a voltage vector on a stationary coordinate systemU a 、U b 、U c ；
A triangular wave generating unit for generating a triangular wave;
a comparator connected with the three-phase duty ratio operation unit and the triangular wave generation unit respectively for comparing the voltage vectorsU a 、U b 、U c And a triangular wave;
and the driving signal generating unit is connected with the comparator and used for generating six paths of PWM control signals for driving the servo motor to work according to the comparison result.
In this embodiment, the comparator outputs the comparison result to the driving signal generating unit in the form of a binary code.
Specifically, the flywheel is connected to the main shaft of the servo motor 2 through a key groove (not shown) to transmit torque.
With continued reference to fig. 5, the motor control apparatus further includes a position information processing unit connected to the position sensor, for collecting the actual position according to a communication protocolθAnd the speed arithmetic unit and the position controller are connected with the position sensor through the position information processing unit. Before the speed calculation and the position control, the position information is processed by the position information processing unit and converted into data required by the position controller and the speed calculation unit.
With reference to fig. 5, the motor control device further includes an FPGA, and the speed operation unit, the position controller, the rotational speed controller, the three-phase duty operation unit, the triangular wave generation unit, the comparator, the driving signal generation unit, and the position information processing unit are all disposed in the FPGA.
Specifically, with reference to fig. 5, a trigonometric function processing unit, a clock management unit, and an external data interaction unit respectively connected to the speed operation unit and the position information processing unit are further disposed in the FPGA. The trigonometric function processing unit is connected with the position information processing unit and the three-phase duty ratio operation unit, is used for carrying out trigonometric function calculation on the current real position to obtain a trigonometric function value, sending the obtained trigonometric function value to the three-phase duty ratio operation unit, and is used for voltage vector calculationU a 、U b 、U c The step of trigonometric function calculation is as follows: and calculating a sine and cosine value corresponding to the current real position. The clock management unit is used for generating a clock, a sampling clock and a reset signal required by the motor control device; the external data interaction unit is connected with an upper computer, receives an instruction of the upper computer and outputs the rotating speed and the position information of the motor to the upper computer. It should be noted that the FPGA communicates with the upper computer through the serial port to complete data exchange, and man-machine exchange can be realized through data monitoring software in the upper computer to monitor the FPGA.
Specifically, with reference to fig. 5, the motor control device further includes a power module and a driving module, the power module supplies power to the FPGA, and the driving module is connected between the driving generation unit and the servo motor, and is configured to amplify the power of the six paths of PWM control signals generated by the driving generation unit and drive the servo motor to operate. Specifically, drive module includes drive circuit and the three-phase full-bridge inverter circuit who comprises 6 IGBT, receives 6 way PWM control signal through drive circuit, with signal isolation amplify the back and carry to the three-phase full-bridge inverter circuit again, control switching on and turn-off of IGBT among the three-phase full-bridge inverter circuit, become three-phase alternating voltage with direct current voltage contravariant by the three-phase full-bridge inverter circuit to driving motor moves.
Specifically, in the present embodiment, the position sensor employs an absolute encoder or an incremental encoder, and may communicate by using SSI protocol, BSSI protocol, EnDat protocol, HIPERFACE protocol, or the like.
Motion control system motion equation
It can be known that whenT L >>T f The influence of the friction force on the torque generated by the motor is negligible, so that the influence of the friction torque on the rotation speed fluctuation can be reduced by increasing the constant load, wherein,Jin order to be the moment of inertia of the machine,ω m is the mechanical angular velocity of the rotor and,T e in order to be an electromagnetic torque,T L in order to be the load torque,T f in order to obtain the friction torque of the motor,Bis the damping coefficient. Literature study on servo system of Lishuai, low-speed and high-stability permanent magnet synchronous motor [ D ]]Harbin university of industry, 2019 "analyzes the influence of friction on the stability of rotating speed in low-speed state, and obtains the lowest stable speed at which the motor does not have the phenomenon of slip and shakeω minHaving a value of about
Wherein, isFThe static friction and the dynamic frictionThe difference between the values of the two signals,ω n zeta is the damping ratio for undamped natural oscillation angular frequency of the system, and is known from the above formulaFThe smaller the size of the tube is,J、ω n the larger zeta is, the lower the minimum steady speed is, and the better the low speed performance of the system is. According to law of rotation of rigid bodiesM=JαI.e. external resultant torque of the motorMUnder certain conditions, angular accelerationαAnd mechanical moment of inertiaJIn inverse proportion, namely: the larger the moment of inertia of the motor is, the smaller the angular acceleration is. Therefore, increasing the moment of inertia can improve the rotational speed stability at low system speeds. According to the servo device, the constant load is reasonably added through the magnetic powder brake, the rotational inertia of the motor rotor is increased through the flywheel to change the working point of the motor, and the phenomenon of 'stagnation-slippage' caused by friction force during low-speed running is weakened, so that the low-speed running stability of the servo motor is improved. Through reasonable design of external torque, the control precision of the common servo motor is improved. Meanwhile, high-precision rotating speed control and motor positioning control of the servo motor can be realized only by adopting a motor rotating speed ring and a motor position ring.
In this embodiment, the rotation speed of the motor is set to 360 °/s, the rotation speed mode experiment and the position mode experiment are respectively performed, the experiment results are shown in fig. 7 and 8, the rotation speed stability is less than 0.83%, and the positioning accuracy is less than 0.001%, which proves that the servo device described in this embodiment can realize high-precision control of the servo motor.
In this embodiment, the rotation speed of the motor is set to be 3 °/s, the same controller parameters are used, and a comparison experiment is performed by using the servo device described in this embodiment and without using the servo device described in this embodiment, respectively, and the result is shown in fig. 9. According to the experimental result, it can be analyzed that the rotation speed fluctuation under the condition that the servo device is not adopted reaches 40 degrees/s, after the servo device is adopted, the rotation speed fluctuation is less than 0.5 degrees/s, namely after the servo device is adopted, the rotation speed fluctuation of a common servo motor in a low-speed running state is obviously reduced, and the effectiveness of the servo device in the embodiment is proved.
The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are possible within the spirit and scope of the claims.
Claims (10)
1. A motor control method without a current sensor is characterized by comprising the following specific steps:
a position information acquisition step: obtaining a true position of a rotor of a servo motorθ；
A speed calculation step: according to the true positionθCalculating the true rotation speed of the servo motorv；
A position control step: will be true positionθAnd a set positionθ*Comparing to obtain a position difference value, and obtaining a speed given value by the position difference value through PI controlv*；
And a rotating speed control step: setting the speed to a given valuev*With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
Three-phase duty ratio operation: for the current real positionθCalculating a trigonometric function to obtain a trigonometric function value, and orienting the magnetic field of the rotor of the servo motor under the conventional conditiond-qThe transformation formula of the coordinate system and the static coordinate system is as follows:
in the formula (I), the compound is shown in the specification,u d is a statordThe current component of the shaft is such that,u q is a statorqThe current component of the shaft is such that,θis the angle of the rotor of the motor,U a 、U b 、U c respectively are three-phase sine modulation wave voltage vector values;
order tou d =0, obtained from formula (1):
obtaining a voltage vector on a stationary coordinate system from the formula (2)U a 、U b 、U c ；
A comparison step: vector of voltageU a 、U b 、U c Comparing with the triangular wave;
a drive signal generation step: and generating six paths of PWM control signals for driving the servo motor to work according to the result in the comparison step.
2. The current sensor-less motor control method according to claim 1, further comprising a position information processing step of: acquiring the real position acquired in the step of acquiring the position information according to the communication protocolθAnd (5) carrying out a digital system conversion treatment.
3. The current sensor-less motor control method according to claim 1 or 2, wherein in the speed calculation step, the actual position is based onθCalculating the real rotation speed of the servo motor by adopting a difference methodv。
4. The current sensor-less motor control method according to claim 1 or 2, wherein in the position control step, the position is set when the servo motor adopts a rotation speed control modeθ *=ṽ * tWherein, in the step (A),ṽ *in order to achieve the desired set rotational speed,tthe operation time of the servo motor is set; when the servo motor adopts a position control mode, setting the positionθ *I.e. the angular position that is expected to be reached.
5. A motor control apparatus for implementing the current sensor-less motor control method according to any one of claims 1 to 4, comprising:
a position sensor mounted at the tail end of the main shaft of the servo motor for acquiring the real position of the rotor of the servo motorθ；
A speed calculation unit connected with the position sensor and used for calculating the speed according to the real positionθCalculating the true rotation speed of the servo motorv；
A position controller connected with the position sensor for calculating the set positionθ *With the true positionθBy calculation of a PI control algorithm to produce a given speed valuev *；
A rotation speed controller respectively connected with the position controller and the speed arithmetic unit and used for setting the speed to a given valuev *With true speed of rotationvObtaining a rotation speed difference value by difference making, and obtaining the rotation speed difference value through PI controlqShaft voltageu q ；
A three-phase duty ratio operation unit connected with the rotation speed controller and used for controlling the rotation speed of the motoru d According to voltage under the condition of =0u q Calculating a voltage vector on a stationary coordinate systemU a 、U b 、U c ；
A triangular wave generating unit for generating a triangular wave;
a comparator connected with the three-phase duty ratio operation unit and the triangular wave generation unit respectively for comparing the voltage vectorsU a 、U b 、U c And a triangular wave;
and the driving signal generating unit is connected with the comparator and used for generating six paths of PWM control signals for driving the servo motor to work according to the comparison result.
6. The motor control device according to claim 5, further comprising a position information processing unit connected to the position sensor for collecting the true position according to a communication protocolθAnd the speed arithmetic unit and the position controller are connected with the position sensor through the position information processing unit.
7. The motor control device according to claim 6, further comprising an FPGA, wherein the speed operation unit, the position controller, the rotational speed controller, the three-phase duty ratio operation unit, the triangular wave generation unit, the comparator, the drive signal generation unit, and the position information processing unit are provided in the FPGA.
8. The motor control device according to claim 7, wherein a trigonometric function processing unit, a clock management unit and an external data interaction unit respectively connected to the speed operation unit and the position information processing unit are further provided in the FPGA, and the trigonometric function processing unit is connected to the position information processing unit and the three-phase duty ratio operation unit, and is configured to perform trigonometric function calculation on the current real position to obtain a trigonometric function value; the clock management unit is used for generating a clock, a sampling clock and a reset signal required by the motor control device; the external data interaction unit is connected with an upper computer, receives an instruction of the upper computer and outputs the rotating speed and the position information of the motor to the upper computer.
9. The motor control device according to claim 7, further comprising a power module and a driving module, wherein the power module supplies power to the FPGA, and the driving module is connected between the drive generation unit and the servo motor and is configured to amplify the power of the six PWM control signals generated by the drive generation unit and drive the servo motor to operate.
10. A servo apparatus, comprising:
fixing a bracket;
the servo motor is arranged on the fixed bracket;
the magnetic powder brake is arranged on the fixed support and arranged above the servo motor, and the main shaft of the magnetic powder brake is parallel to the main shaft of the servo motor;
the first gear is arranged on a main shaft of the servo motor;
the second gear is arranged on the main shaft of the magnetic powder brake and is meshed with the first gear;
the flywheel is arranged on the motor output shaft of the servo motor, arranged on the outer side of the first gear and connected with the main shaft of the servo motor;
a motor control apparatus using the motor control apparatus according to any one of claims 5 to 9.
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