Background
With the continuous innovative development of the automobile electronic technology and the control technology, the automobile power steering system goes from the traditional pure mechanical power steering system to the gradually developed and perfect hydraulic power steering system and then to the later novel electric control hydraulic power steering system, and the electric power steering system, namely the EPS system, is widely popularized and used nowadays. The EPS system adopts a power-assisted motor to provide steering power assistance, and the power assistance is directly controlled by an electric control system. Compared with the traditional hydraulic power-assisted steering system, the method for controlling the power assistance by the motor can save energy and is very environment-friendly.
The EPS system is provided with a power source by a power-assisted motor, and mainly comprises a torque sensor, the power-assisted motor, a speed reducing mechanism and a motor electronic control unit. The hydraulic system is cancelled, the engine works independently, and the energy consumption is reduced; the EPS system only adopts mechanical connection and electric signal control, has higher efficiency and is beneficial to chassis integrated control; the direct current motor has good starting and speed regulating performance, so that the direct current motor is widely applied to an EPS system, but the sliding contact of the electric brush and the commutator causes mechanical abrasion and sparks to form a radio interference source, so that the direct current motor has many faults and low reliability. The existing permanent magnet synchronous motor has the advantages of small size, high efficiency, high power factor and the like, and is developed into a novel steering motor which replaces an EPS system direct current motor, namely an EPS permanent magnet synchronous motor.
The EPS system, as a torque servo system, requires a motor assist torque with rapid and accurate response, and is very sensitive to the pulsation of the torque, so that the stable and reliable operation of the motor depends on a motor control technology. In practical industrial control systems, especially in high-performance speed regulation occasions, the position sensor is an important element for acquiring a rotor position signal, but the sensor may be in failure under the environments of high and low temperature, humidity and the like, so that the accuracy of the sensor is reduced and even the sensor is damaged, and the operation stability and controllability of the motor are affected. The simultaneous mounting of position sensors increases the cost of the drive system as well as the bulk and complexity of the drive system. Therefore, the research on the control of the motor without a position sensor is very necessary.
The traditional position-sensorless control method is to inject high-frequency signals, a heterodyne demodulation technology is adopted in position sensing control, and because heterodyne demodulation has an inertia link, delay exists in estimation of rotor position signals, and the speed regulation performance of a motor is directly influenced.
Disclosure of Invention
The invention aims to provide a position sensorless controller of an automobile EPS steering system, which can effectively improve the control precision of a motor position sensorless control scheme, particularly high-performance control under transient working conditions, aiming at the defects of the existing position sensorless control scheme of an EPS permanent magnet synchronous motor.
The invention relates to a controller of an automobile EPS steering system without a position sensor, which adopts the technical scheme that: the device consists of an EPS state feedback controller, a band-pass filter, a per-unit module, a discrete angle judgment module, a low-pass filter, a two-phase high-frequency voltage calculation module, a 2s/2r coordinate transformation module, a 3s/2s coordinate transformation module, an angle initialization module and a low-pass filter, wherein the first input of the EPS state feedback controller is a reference angle theta
refThe second input is the fundamental current i under the two-phase rotating coordinate system output by the 2s/2r coordinate transformation module
dq(k) The third input is the final estimated angle theta (k) output by the first low-pass filter, and the EPS state feedback controller outputs a control voltage u
αβ(k) (ii) a The input of the two-phase high-frequency voltage calculation module is a high-frequency voltage V
inAnd angular frequency ω
inThe output is high-frequency injection voltage under a two-phase static coordinate system
The control voltage u
αβ(k) And high frequency injection voltage
As two inputs of the EPS steering system, the EPS steering system outputs three-phase current I
abc(k) To a 3s/2s coordinate transformation module, the 3s/2s coordinate transformation module outputs current I under a two-phase static coordinate system
αβ(k) Respectively to a band-pass filter and a second low-pass filter, the band-pass filter outputs high-frequency current under two-phase static coordinate system
To the per unit module, the second low-pass filter outputs fundamental current i under the two-phase static coordinate system
αβ(k) To a 2s/2r coordinate transformation module, the 2s/2r coordinate transformation module outputs fundamental current i under a two-phase rotating coordinate system
dq(k) (ii) a The per-unit module outputs per-unit parameters K
αβ(k) To a discrete angle judgment module as the first input of the discrete angle judgment module, and the second input of the discrete angle judgment module is the angular frequency omega
inThe discrete angle judgment module outputs a preliminary estimated angle
The first low-pass filter outputs the final estimated angle theta (k) to the angle initialization module, the 2s/2r coordinate transformation module and the EPS state feedback controller respectively, and the angle initialization module outputs the third input of the discrete angle judgment module3 initialization angles theta
1,θ
2,θ
3。
The invention has the beneficial effects that:
1. according to the invention, the precision estimation of the position angle of the motor is realized through the discrete angle judgment module, so that the position sensor-free control of the EPS steering system is realized, and the defects of increased cost, complex driving system and the like caused by the installation of a position sensor in the traditional control are overcome. Compared with the traditional controller without the position sensor, the controller is efficient and direct, avoids the defects of system delay, buffeting and the like, and realizes the high-precision control of the EPS steering system without the position sensor.
2. The EPS state feedback controller replaces the traditional series closed-loop control system, so that the defects of the series closed-loop system are avoided, and the control precision of the system is improved.
3. The required control variable and the input variable are easy-to-measure variables, and the control algorithm of the controller can be realized only by modular software programming, thereby being beneficial to engineering realization.
Detailed Description
As shown in fig. 1, the present invention is composed of an EPS state feedback controller 1, a band pass filter 3, a per unit module 4, a discrete angle determination module 5, a first low pass filter 6, a two-phase high frequency voltage calculation module 7, a 2s/2r coordinate transformation module 8, a 3s/2s coordinate transformation module 9, an angle initialization module 10, and a second low pass filter 11.
The output end of the EPS state feedback controller 1 is connected with a first input end of the EPS steering system 2, and the output end of the two-phase high-frequency voltage calculation module 7 is connected with a second input end of the EPS steering system 2. The output end of the EPS steering system 2 is connected with the input end of a 3s/2s coordinate transformation module 9, the output end of the 3s/2s coordinate transformation module 9 is divided into two paths, one path is sequentially connected with a second low-pass filter 11, a 2s/2r coordinate transformation module 8 and the EPS state feedback controller 1 in series, and the other path is sequentially connected with a band-pass filter 3, a per-unit module 4, a discrete angle judgment module 5 and a first low-pass filter 6 in series. The output end of the first low-pass filter 6 is respectively connected with the angle initialization module 10, the 2s/2r coordinate transformation module 8 and the EPS state feedback controller 1. The output end of the angle initialization module 10 is connected with the discrete angle judgment module 5.
The EPS state feedback controller 1 has three inputs, the first of which is a reference angle theta
ref(ii) a The second input is the fundamental current i under the two-phase rotating coordinate system output by the 2s/2r coordinate transformation module 8
dq(k) K is a discrete sample sampling index, and
) (ii) a The third input is the final estimated angle θ (k) output by the first low pass filter 6.
The EPS state feedback controller 1 processes the three output values and outputs a control voltage uαβ(k) The control voltage uαβ(k) Is the first input to the EPS steering system 2.
The input of the two-phase high-frequency voltage calculation module 7 is a high-frequency voltage V injected from the outside
inAnd a high frequency voltage V
inAngular frequency of (omega)
inThe output is high-frequency injection voltage under a two-phase static coordinate system
The high frequency injection voltage
Is an EPS steering system 2To the second input of (a).
EPS steering System 2 to control Voltage u
αβ(k) And high frequency injection voltage
As input, three-phase current I is output
abc(k) The three-phase current I
abc(k) And outputs to the 3s/2s coordinate transformation module 9. The 3s/2s coordinate transformation module 9 transforms the three-phase current I
abc(k) Conversion to a current I in a two-phase stationary coordinate system
αβ(k) Respectively passes through a band-pass filter 3 and a second low-pass filter 11, and the band-pass filter 3 outputs a high-frequency current under a two-phase static coordinate system
The second low-pass filter 11 outputs a fundamental current i in the two-phase stationary coordinate system
αβ(k) In that respect The 2s/2r coordinate transformation module 8 transforms the fundamental current i
αβ(k) Converted into fundamental current i under a two-phase rotating coordinate system
dq(k) And input into the EPS state feedback controller 1 as a second input to the EPS state feedback controller 1.
High frequency current
Inputting into the per-unit module 4, the per-unit module 4 processes the high-frequency current
Performing per-unit processing to obtain per-unit parameter K
αβ(k) And input to the discrete
angle determination module 5 as the first input of the discrete
angle determination module 5. The second input of the discrete
angle judgment module 5 is the angular frequency omega of the high-frequency voltage
inThe third input is the initialized angle theta output by the angle initializing module 10
1,θ
2,θ
3The output of the discrete
angle judgment module 5 is the preliminary estimated angle
Preliminary estimation of angle
The first low-pass filter 6 outputs the final estimated angle θ (k) through the first low-pass filter 6. The final estimated angle θ (k) is used as an input of the angle initialization module 10, and the angle initialization module 10 outputs the initialized angle θ
1,θ
2,θ
3The initialized angle theta
1,θ
2,θ
3As a third input to the discrete
angle determination module 5.
As shown in fig. 2, the
EPS steering system 2 is composed of a space voltage
vector modulation module 21, a
voltage source inverter 22, a permanent magnet
synchronous motor 23, and a
speed reduction mechanism 24, which are connected in series in this order. Control voltage u of
EPS steering system 2 in two-phase stationary coordinate system
αβ(k) And high frequency injection voltage
As input, three-phase current I is output
abc(k) In that respect Space voltage
vector modulation module 21 to control voltage u
αβ(k) And high frequency injection voltage
The sum is used as input to output a switching pulse signal T
a、T
b、T
cThe
voltage source inverter 22 switches the pulse signal T
a、T
b、T
cAs input, three-phase current I is output
abc(k) The permanent magnet
synchronous motor 23 is driven by three-phase current I
abc(k) For input, output torque T
eTo the
speed reducing mechanism 24.
As shown in fig. 3, the EPS state feedback controller 1 is composed of a 2r/2s coordinate transformation module 12 and a feedback voltage controller 13. Current i in two-phase rotating coordinate systemdq(k) And a reference angle thetarefAnd the estimated angle theta (k) as input to the feedback voltage controller 13, the feedback voltage controller 13 outputting a control voltage u in a two-phase rotation coordinate systemdq(k) The control voltage udq(k) As a first input of the 2r/2s coordinate transformation module 12, a second input of the 2r/2s coordinate transformation module 12 is an estimated angle θ (k), and the coordinate transformation by the 2r/2s coordinate transformation module 12 is performedAfter conversion, the control voltage u under the two-phase static coordinate system is outputαβ(k) The control voltage uαβ(k) Is the output of the EPS state feedback controller 1.
The expression of the feedback voltage controller 12 is:
wherein X is ═ i
d(k),i
q k(k),θ(k),E
θ]
TAnd is a state variable matrix of the system. i.e. i
d(k),i
q(k) In order to synchronize the currents in the rotating coordinate system,
and k is the integral of the rotating speed error, k is a discrete sampling index, and T is a sampling period. The gain coefficient matrix of the feedback voltage controller 12 with P being 2 × 4, according to the actual parameters and the working condition of the
EPS steering system 2, the gain coefficient matrix of the feedback voltage controller 1 is:
the input of the two-phase high-frequency voltage calculation module 7 is high-frequency voltage V
inAnd angular frequency omega of high frequency voltage
inThe output is high-frequency injection voltage under a two-phase static coordinate system
The input-output relationship of the two-phase high-frequency voltage calculation module 7 is as follows:
where k is the discrete sampling index and T is the sampling period.
Three-phase current I output by EPS steering system 2
abc(k) Converted into a two-phase static coordinate system by a 3s/2s coordinate conversion module 9Current I of
αβ(k) Respectively passing through a band-pass filter 3 and a second low-pass filter 11 to output high-frequency current in a two-phase stationary coordinate system
And a fundamental current i
αβ(k)。
The per-unit module 4 outputs the high-frequency current to the band-pass filter 3
Per-unit, outputting per-unit parameter K
αβ(k) The expression of (a) is:
in the formula, L
d、L
qIs the stator inductance under the rotating coordinate system,
the angle initialization module 10 inputs the estimated angle theta (k) and outputs 3 initialization angles theta (k)1,θ2,θ3. The angle initialization module 10 first performs delay processing on the estimated angle θ (k) to obtain the estimated angle θ (k-1) of the previous period, and calculates 3 initialization angles θ (k-1) according to the estimated angle θ (k-1)1,θ2,θ3Respectively is as follows:
the discrete
angle judgment module 5 pairs the per unit parameter K
αβ(k) Angular frequency omega
in3 initialization angles theta
1,θ
2,θ
3Processing, making discrete angle judgment, and outputting the angle estimation value of current time
Discrete angleThe judgment process of judgment is as follows:
(1) initializing 3 angles theta1,θ2,θ3Are respectively recorded as 3 iteration angles theta'1,θ′2,θ′3Setting an iteration termination coefficient lambda;
(2) respectively iterating the angles theta'1,θ′2,θ′3Combined per unit parameter Kαβ(k) Angular frequency omegainAnd calculating 3 cost functions Q by the sampling period T1,Q2,Q3The cost function calculation formula is as follows:
if the estimated rotor angle is completely accurate, the corresponding cost function value Q1,Q2,Q3Is 0 and therefore the magnitude of the cost function value represents the accuracy of the rotor position signal.
(3) Will iterate an angle of θ'1,θ′2,θ′3Corresponding 3 cost function values Q1,Q2,Q3Comparing, and taking the iteration angle corresponding to the minimum cost function value as the optimal angle thetaop。
(4) Make theta'1=θop,θ′2=θop+2π/3·2-n,θ′3=θop-2π/3·2-nAnd n is the current iteration number.
(5) If (theta'2-θ′1) If lambda is less than lambda, the iteration is terminated, otherwise, the step (2) is returned.
(6) After the iteration is ended, outputting an angle estimated value
Estimated angle of output from the discrete
angle judgment module 5
As a first low passThe final estimated angle theta (k) is output by the filter 6, and is used as the input of the EPS state feedback controller 1, the 2s/2r coordinate transformation module 8 and the angle initialization module 10.
As shown in figure 1, an EPS state feedback controller 1 and a two-phase high-frequency voltage calculation module 7 are connected in parallel and then connected with an input end of an EPS steering system 2, an output end of the EPS steering system 2 is connected with a 3s/2s coordinate transformation module 9 in series, an output end of the 3s/2s coordinate transformation module 9 is connected with a second low-pass filter 11, a 2r/2s coordinate transformation module 8 and the EPS state feedback controller 1 in series in sequence to form local closed-loop control, and meanwhile, the output end of the EPS state feedback controller is connected with a band-pass filter 3, a per unit module 4, a discrete angle judgment module 5 and a first low-pass filter 6 in series to finally form an EPS steering system position-sensor-free controller, so that position-sensor-free control of the EPS steering system is realized. The EPS state feedback controller 1 replaces a traditional series closed-loop control system, so that the defects of the series closed-loop system are overcome, and the control precision of the system is improved. The two-phase high-frequency voltage calculation module 7 realizes the low-speed control of the permanent magnet synchronous motor by introducing high-frequency voltage. The per unit module 4 eliminates the adverse effect of the motor parameter change on the control. The invention overcomes the defects of increased cost, complex driving system and the like caused by installing the position sensor in the traditional control method, and avoids the control delay caused by the traditional phase-locked loop control technology without the position sensor. The defects of angle estimation precision, system delay, buffeting and the like are improved through discrete angle iterative optimization. Meanwhile, the EPS state feedback controller replaces the traditional series closed-loop control, and the control accuracy and the control structure are improved, so that the high-accuracy EPS steering system is controlled without a position sensor.