Summary of the invention
Technical problem to be solved by this invention provide a kind of lower-cost, do not need position transducer such as external encoder can and realize rotor is lost the detection method of losing step detection architecture, stepping motor and use thereof of stepping motor of the detection in step.
The objective of the invention is to be achieved through the following technical solutions:
A kind of stepping motor lose the step detection architecture, comprise that the back electromotive force according to stepping motor obtains device to the physical location of the calculating measuring and calculating device of rotor actual angular position, the given position to obtain system's given position that is connected with the Stepping Motor Control system, and obtain the comparison means that device is connected with given position with physical location measuring and calculating device; Described comparison means compares rotor actual angular position and system's given position, and whether output loses the testing result in step.
The described physical location measuring and calculating device of losing the step detection architecture comprises back electromotive force calculation element that back electromotive force is calculated, and calculates the actual angular position calculation element of rotor actual angular position according to back electromotive force.
Described back electromotive force calculation element comprises winding voltage checkout gear, winding current checkout gear, and it is according to equation group:
Calculate; Wherein, e
A, e
BBe respectively the back electromotive force of two windings of motor; u
A, u
ABe respectively the voltage of two windings of motor; i
A, i
BBe respectively the electric current of two windings of motor; R is the resistance of stepping motor winding; L is the inductance of stepping motor winding.This is a kind of mode of calculating back electromotive force.
Described actual angular position calculation element is according to equation
Calculate, wherein, θ
rBe the rotor actual angular position, described e
A, e
BBack electromotive force for two windings of motor.This is a kind of mode of calculating actual angular position according to back electromotive force.
The described step detection architecture of losing also comprises the filter that the result of calculation of back electromotive force calculation element is carried out filtering that is arranged between back electromotive force calculation element and the actual angular position calculation element.Owing in losing the step detection architecture, calculate the differential of electric current
The time, can cause very big noise, cause error calculated bigger, owing to causing the inaccurate of voltage and current measurement, the HF switch action can carry out Filtering Processing in order to reduce simultaneously, to improve computational accuracy to the result of calculation of back electromotive force calculation element.
The described step detection architecture of losing also comprises the coordinate transform structure with three-phase stepper motor or five phase step motor equivalence one-tenth two-phase stepping motor that is connected with physical location measuring and calculating device.Like this be arranged so that this lose the step detection architecture can be common in two-phase stepping motor, three-phase stepper motor or the five phase step motor.
Be preset with the difference and the threshold that obtain after threshold value, described comparison means compare rotor actual angular position and system's given position in the described comparison means, only when the difference that relatively obtains is outside the preset threshold value scope, export the testing result that this stepping motor is lost the step.
A kind of stepping motor comprises control system, and wherein, described stepping motor also includes the above-mentioned step detection architecture of losing.
A kind of stepping motor detects the method for losing the step, may further comprise the steps:
A: calculate the rotor actual angular position according to the back electromotive force of stepping motor;
B: system's given position that actual angular position and the Stepping Motor Control system of measuring and calculating is given compares, and exports the testing result of whether losing the step.
In the described steps A, may further comprise the steps:
A1: detect the also winding back electromotive force of calculated step motor;
A2: calculate rotor position angle according to the winding back electromotive force.
In the described steps A 1, also comprise the voltage to winding, the step that electric current detects respectively, and according to equation group:
Carry out e
A, e
BCalculating; Wherein, e
A, e
BBe respectively the back electromotive force of two windings of motor; u
A, u
ABe respectively the voltage of two windings of motor; i
A, i
BBe respectively the electric current of two windings of motor; R is the resistance of stepping motor winding; L is the inductance of stepping motor winding.
In the described steps A 2, according to equation
Carry out θ
rCalculating, wherein, θ
rBe the rotor actual angular position, described e
A, e
BBack electromotive force for two windings of motor.
In the described steps A 1, also comprise the step of the result of calculation of back electromotive force calculation element being carried out filtering.
Before the described steps A 1, also comprise step with the coordinate transform of three-phase stepper motor or five phase step motor equivalence one-tenth two-phase stepping motor.Like this be arranged so that this lose the step detection architecture can be common in two-phase stepping motor, three-phase stepper motor or the five phase step motor.
Among the described step B, after the given system's given position of actual angular position and Stepping Motor Control system that will measuring and calculating compares, comprise that also the difference that will relatively obtain compares with preset threshold value, if the difference that relatively obtains is then exported the step that this stepping motor is lost the testing result in step outside the preset threshold value scope.
The present invention is under the situation of not using additional sensor, by the back electromotive force that extracts stepping motor the rotor actual angular position is calculated, again by the given system's given position of Stepping Motor Control system is compared with the rotor actual angular position that test obtains, just can judge whether stepping motor is lost the step, can realize open loop control down to stepping motor lose the step detection, effective, cost is low.
Embodiment
The invention will be further described below in conjunction with accompanying drawing and preferred embodiment.
When the stepping motor steady operation, the back electromotive force of motor is synchronous with the rotation of rotor all the time, so the frequency of back electromotive force is also identical with the running frequency of rotor.Therefore, just can calculate the rotor actual angular position by the back electromotive force of stepping motor; And the Stepping Motor Control system uses the pulse command form usually, and in corresponding one step of stepping motor operation of pulse, meeting usage counter paired pulses instruction count forms given system's given position in its control system.By the given system's given position of Stepping Motor Control system is compared with the rotor actual angular position that test obtains, just can judge whether stepping motor is lost the step.Inventive concept of the present invention that Here it is.
Stepping motor of the present invention includes control system and loses the step detection architecture, and as shown in Figure 1, the described step detection architecture of losing comprises:
Back electromotive force according to stepping motor is calculated device to the physical location of calculating of rotor actual angular position;
The given position to obtain system's given position that is connected with the Stepping Motor Control system obtains device;
Reach with physical location measuring and calculating device and obtain the comparison means that device is connected with given position;
Described comparison means compares rotor actual angular position and system's given position, and whether output loses the testing result in step.
The described physical location measuring and calculating device of losing the step detection architecture comprises back electromotive force calculation element that back electromotive force is calculated, and calculates the actual angular position calculation element of rotor actual angular position according to back electromotive force.
Fig. 2 is that the composite stepper motor with two-phase is the action model of the MOSFET of the stepping motor winding model made of example and H bridge.In this model, what DC power supply 1 had produced back electromotive force 3, switch 4 expression field effect transistor (MOSFET) when comprising resistance R and inductance L, motor operation for motor windings 2 power supplies, motor windings turns on and off action, analog to digital converter 5 and analog to digital converter 6 the collection busbar voltage of correspondences and the electric current of motor windings respectively.In a switch periods, the electric equation of motor two phase windings is:
Wherein: e
A, e
BBe respectively the back electromotive force of two windings of motor; u
A, u
ABe respectively the voltage of two windings of motor; i
A, i
BBe respectively the electric current of two windings of motor; R is the resistance of stepping motor winding; L is the inductance of stepping motor winding.
Simultaneously, establishing rotor position angle is θ
r, rotor speed is ω
r, the back electromotive force that then produces in AB two phase windings is as follows respectively:
e
A=-ψ
f?ω
r?sin?θ
r
e
B=ψ
f?ω
r?cos?θ
r (2)
Wherein, Ψ f is the magnetic linkage of rotor permanent magnet in the induction of stator phase winding.
According to (2) Shi Kede, the position θ of rotor
rFor:
By (3) formula as can be known, the actual angular position of motor can estimate by back electromotive force, by actual angular position calculation element specific implementation; And, need obtain winding current, voltage, resistance and inductance in (1) formula in order to calculate back electromotive force, by back electromotive force calculation element specific implementation.
Described back electromotive force calculation element comprises winding current checkout gear and winding voltage checkout gear, described winding current checkout gear is realized the detection to the stepping motor winding current, it can adopt existing resistance method of temperature measurement or Hall element method or other current measurement method to measure usually, wherein resistance method of temperature measurement is comparatively simple, cost is low, but because the power and the power consumption constraints of measuring resistance, be not suitable for use in Super-Current Measurement, and because the running current of stepping motor is less usually, generally all less than 10A, so the electric current that uses resistance method of temperature measurement to detect stepping motor is fully passable; And the advantage of Hall element method is that it has realized isolation measurement by Hall element, can eliminate that ground wire in the control circuit disturbs, the switching noise of high frequency power device, but its cost is more expensive.When specifically putting into practice, can select corresponding current measuring method according to actual needs.
Described winding voltage checkout gear is realized the detection to the voltage at stepping motor winding two ends, its can be by busbar voltage therewith the time duty ratio of pulse-width modulation PWM (Pulse Width Modulation) calculate, busbar voltage is measured to the voltage range that analog to digital converter 5,6 can bear by electric resistance partial pressure, and the duty ratio of PWM is a numerical control system by as calculating after the control algolithms such as proportional integral.Certainly, also can adopt other method that the voltage at motor windings two ends is measured.
The resistance of stepping motor winding and inductance can obtain by the nameplate of stepping motor usually, also can measure by numerical control system.The measurement of resistance and inductance can have a variety of methods to realize, such as applying a fixing voltage on winding by PWM, measures the electric current of winding this moment, can calculate the resistance of winding etc. according to Ohm's law.And after resistance measurement is finished, close PWM output, and make the electric current free damping of motor, the electrical time constant that current attenuation is exactly a motor to 0.36 times of employed time of initial current, it is exactly inductance that electrical time constant multiply by resistance.
The described step detection architecture of losing also comprises the filter that the result of calculation of back electromotive force calculation element is carried out filtering that is arranged between back electromotive force calculation element and the actual angular position calculation element.This is owing to calculate the differential of electric current in numerical control system
The time, may cause bigger noise, cause error calculated bigger; Inaccurate in order to reduce to cause that by the HF switch action of HF switch MOSFET4 voltage and current is measured simultaneously, need be to the result of calculation of (1) formula, just the result of calculation of back electromotive force calculation element is carried out filtering.
Because the back electromotive force of stepping motor is by the speed of service decision of stepping motor, when the stepping motor speed of service is zero, back electromotive force also is zero, when stepping motor during at low cruise, back electromotive force is very little, the error of the back electromotive force that is calculated by (1) formula accordingly will be bigger, therefore adopt the stepping motor of losing the step detection architecture of the present invention especially to be more suitable in the stepping motor that more than certain speed, moves, the threshold values of this speed is decided according to real electrical machinery, is good in the speed more than 1 revolutions per second usually.
Be preset with threshold value, described comparison means in the described comparison means with the rotor actual angular position θ that calculates
rCompare with the system's given position that obtains from stepping motor, when the difference that relatively obtains is outside the preset threshold value scope, shows and taken place to lose the step, then export the testing result that this stepping motor is lost the step.
Fig. 3 shows the stepping motor of implementing in this programme and detects the method for losing the step, and it may further comprise the steps:
In a control cycle, start the electric current that analog to
digital converter 5,6 is measured busbar voltages and motor windings, calculate the voltage of motor windings according to busbar voltage and duty ratio, the winding terminal voltage that calculates is carried out low-pass filtering; Calculate
With
And carry out low-pass filtering;
According to equation group:
Calculate the back electromotive force e of two phase windings
A, e
BThe back electromotive force e of two phase windings
AAnd e
BAfter low pass filter filtering, can remove the noise that HF switch and digital operation cause, utilize formula like this
(3) rotor position angle that comes out of observation can be more accurate and stable;
Calculate rotor actual angular position θ according to formula (3)
rAnd from the Stepping Motor Control system reading system given position, after the given system's given position of actual angular position and Stepping Motor Control system of measuring and calculating compared, the difference that relatively obtains is compared with preset threshold value, if the difference that relatively obtains is then exported the testing result that this stepping motor is lost the step outside the preset threshold value scope.
Wherein, the definite of above-mentioned threshold values decides according to the The noise of control system, generally may be selected to be the step angle of two stepping motors.If threshold values is excessive, detect the time of losing the step will strengthen, if too small, might be because the noise effect in the system cause detecting the too sensitive flase drop survey that produces.Concrete threshold values can be chosen by experiment according to concrete stepping motor.
The foregoing description is that the composite stepper motor with two-phase is that example is made, for other stepping motor, as three-phase stepper motor or five phase step motor, can make three-phase stepper motor or five phase step motor equivalence become two stepping motors to detect by coordinate transform (Clake conversion).Therefore, the losing the step detection architecture and can also comprise the coordinate transform structure that three-phase stepper motor or five phase step motor equivalence is become two-phase stepping motor that is connected with physical location measuring and calculating device of the described stepping motor of this programme is so that this loses and goes on foot detection architecture and can be common in two-phase stepping motor, three-phase stepper motor or the five phase step motor.Lose when step and detect at it, only need be before calculating back electromotive force, carry out and become the step of the coordinate transform of two-phase stepping motor to get final product three-phase stepper motor or five phase step motor equivalence.
Though and be that example describes with the composite stepper motor in the foregoing description, but because composite stepper motor combines the characteristics of magneto and reaction stepping motor, the relation of the motor windings model of magneto and reaction equation and back electromotive force and position angle is all with hybrid consistent, so this programme is equally applicable to magneto and reaction stepping motor.
Above content be in conjunction with concrete preferred implementation to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.