Patent Grant
9991835
The present invention relates to a control device for an electric compressor.
When controlling a motor of an electric compressor or the like, the motor is controlled by detecting a rotation position or a rotation speed of a rotor of the motor using a sensor such as a position sensor or a speed sensor. In this case, since a decrease in reliability accompanied with a high temperature environment, disconnection or the like, an increase in the size of the device (dimensions of the outer frame of the motor, especially axial length), an increase in cost and the like are caused, sensorless control is applied these days. Since the sensorless control is influenced by speed estimation characteristics, it is difficult to suppress oscillation. Therefore, as a measure for that, the technology disclosed in Patent Document 1 is known.
In order to control a motor of a compressor in a sensorless manner, the conventional control device for an electric compressor disclosed in Patent Document 1 has a first command current setting portion which sets a first command current for reducing a rotation speed deviation between a target rotation speed and an actual rotation speed, a second current setting portion which sets a second command current of the motor based on the load fluctuation frequency set from mechanical fluctuation factors of the compressor, a third command current calculation portion which sets a third command current of the motor from the first command current and the second command current, and an inverter switching pattern generation portion which generates a command for motor driving from at least the third command current and the actual rotation speed (estimated from the motor inverter).
In the second command current setting portion, the rotation speed deviation is input to a peak filter using a load fluctuation frequency as a peak frequency to set, as the second command current, the output of the peak filter obtained using a transfer function expressed by the following expression.
That is, the transfer function of the peak filter is expressed as follows:
Peak Filter(s)=kω/(s2+ω2)
Here, ω indicates a peak frequency (rad/s) and is determined as a load fluctuation frequency. s indicates the Laplacian operator and k indicates a gain.
Patent Document 1: JP-A-2010-88200
However, the conventional control device for an electric compressor has a problem as described below.
That is, in the conventional control device, the oscillation of the compressor is reduced by reducing the fluctuation of the rotation speed using the peak filter.
However, since the frequency range that can be handled by the peak filter is narrow, an estimation error is generated when a frequency outside of this range is input. Thus, the estimation accuracy of the rotation speed is reduced.
The actual load fluctuation has a plurality of frequency components. Accordingly, when the peak filter is used, it is necessary to connect and use peak filters having different handling frequencies in parallel. However, in that case, tuning becomes complicated and difficult.
The invention is contrived in view of the problem and an object thereof is to provide a control device for an electric compressor capable of successfully controlling a drive motor of the compressor in response to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner.
For this object, a control device for an electric compressor according to the invention includes a target rotation speed setting portion which sets a target rotation speed of a motor which drives the compressor; an estimated rotation speed calculation portion which calculates an estimated rotation speed of the motor; a drive command signal generation portion which generates a drive command signal of the electric motor to remove a rotation speed difference between the target rotation speed and the estimated rotation speed; a repetitive control portion to which the rotation speed difference is input to perform a repetitive operation using the rotation speed difference of one preceding cycle of the compressor, thereby reducing the rotation speed difference; a pressure detecting portion which detects a pressure value of the compressor; and a reset signal generation portion to which the pressure value of the compressor is input to calculate a timing of one rotation of the compressor by counting the number of predetermined parts of load fluctuations of the compressor based on the pressure value, thereby outputting a reset signal to the repetitive control portion according to the timing.
In a control device for an electric compressor of the invention, a repetitive control portion performs a repetitive operation using a rotation speed difference between a target rotation speed of one preceding cycle and an estimated rotation speed to reduce the rotation speed difference to thus suppress a disturbance. However, in that case, since the cycle switching timing in the repetitive control portion is determined according to the pressure fluctuation of the compressor, the drive motor of the compressor can be successively controlled with respect to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner.
Hereinafter, embodiments of the invention will be described in detail based on the examples shown in the drawings.
A control device for an electric compressor of Example 1 controls an interior permanent magnet synchronous motor (IPMSM) which drives a compressor of a vehicular air conditioning device in a sensorless manner.
Here, in the above-described control, repetitive control advantageous for suppressing the cyclic disturbance is used since the signal is cyclic due to the rotation of the compressor.
In the repetitive control of this example, in the suppression of the disturbance of a rotation speed difference, a reset signal for switching the cycle of the repetitive operation is different from that in a conventional normal method. That is, in the invention (Example 1), the reset signal is generated using a pressure signal of the compressor.
Hereinafter, an overall configuration of the control device for an electric compressor of Example 1 will be described.
As shown in
The compressor pressure detecting portion 1 detects the magnitude of a pressure of the compressor (not shown) and outputs a pressure value having a pressure waveform detected herein to the reset signal generation portion 4.
The target rotation speed setting portion 2 calculates and sets a target rotation speed ωref of the motor as a control target.
That is, a detected actual air temperature and a target air temperature are compared to set the target rotation speed ωref of the motor by proportional integral (PI) control, so that the temperature of the air after passing through an evaporator (outside of the drawing) of the vehicular air conditioning device reaches a desired value. The target rotation speed ωref is input to the subtracter 3.
The subtracter 3 calculates a rotation speed difference as a control deviation by subtracting an estimated rotation speed ω_
Based on the pressure value input from the compressor pressure detecting portion 1, the reset signal generation portion 4 determines the timing of one rotation (corresponding to one cycle of the repetitive operation in the repetitive control portion 5) of the compressor by counting the number of predetermined parts according to the inlet pressure or discharge pressure with respect to the pressure fluctuation of the compressor, and outputs a reset signal to the repetitive control portion 5 according to this timing.
The generation of the reset signal will be described in detail later.
The repetitive control portion 5 which is a type of time delay system performs a repetitive operation using a set control deviation of one preceding cycle to follow the cyclic target input.
That is, when a minimum rotation number for performing the repetitive control is indicated by Wref_min and a sampling cycle is indicated by Ts, the repetitive control portion 5 has n delay devices 5a (Z in
The n delay devices 5a are connected in series and output a signal V0 from the delay device positioned at the rear end to the adder 5b. As shown in
The adder 5b adds the rotation speed difference calculated by the subtracter 3 to the value of the signal V0 and outputs the result to the delay devices 5a positioned at the front end.
A signal Vα is input to the coefficient multiplier 5c and its value is multiplied by a coefficient β. The result is output to the LPF 6 as an output u of the repetitive control portion 5. As shown in
In the repetitive control portion 5, the flowchart shown in
First, in Step S1, a deviation e (difference of rotation number in Example 1) is observed for each sampling cycle Ts.
Next, the process proceeds to Step S2.
In Step S2, a value obtained by adding the deviation e observed in Step S1 to an i-th value di among values d stored for one preceding cycle (N items) is stored as a new value di.
Next, the process proceeds to Step S3.
In Step S3, a value obtained by multiplying an i+α-th value di+α by a coefficient β is provided as an output u. That is, u=βdi+α is obtained.
As will be described later, in a case of i+α>N, the output value is output to the coefficient multiplier 5b as u=βdi+α−N. Here, di+α−N indicates a value di+α obtained in a cycle after the data of one preceding cycle. This will be described later.
Next, the process proceeds to Step S4.
In Step S4, i+1 is set to i and the positions of the values of d are shifted by one to the downstream side.
Next, the process proceeds to Step S5.
In Step S5, it is determined whether a new reset signal has been input from the reset signal generation portion 4. If the result is YES, the process proceeds to Step S6, but if the result is NO, the process returns to Step S1.
In Step S6, i is reset to 0 and the process returns to Step S1 to perform the calculation of the next new cycle.
These steps are repeatedly executed during the control of the motor.
Here, the output in Step S3 will be described in detail below.
Here, a case in which α is 2 and N is 100 will be used as an example for description.
Accordingly, as shown in
Here, in a case of i=1, that is, d1, i+α=i+2=3 is obtained. Accordingly, a value at the position of d3 is taken and multiplied by a coefficient β, and the obtained value becomes the output u.
Similarly, in a case of i=4, that is, d4, i+2=4+2=6 is obtained. Accordingly, a value at the position of d6 is taken and used for calculation of the output u.
Similarly, in a case of i=5, 6, 7, etc., values of d7, d8, d9, etc. are taken.
However, in a case of i=99 (that is, the above-described condition of i+α>N is satisfied), d101 does not exist. In this case, in an operation for storing the actual values d, the next values d are sequentially given as d1, d2, etc. after the value d100 of one preceding cycle as shown in
When the above-described operation is shown while comparing with the respective delay devices 5a of
In a case of i=0 (that is, d0), the operation is as shown in
These values d are sequentially shifted to the downstream side (the right side in
Accordingly, the values d of the signals V0 to V3 are also sequentially switched.
In a case of i=1 (that is, d1), as shown in
In a case of i=2 (that is, d2), as shown in
As understood from above, the signals V are variables at fixed positions, and the values d stored in the memory corresponding to the signals V are sequentially shifted to the right side in
VN=e+di
VN−1=di−1
VN−2=di−2
. . . .
V1=e+di−N+1=di+1
V2=e+di−N=di
The value di is defined as follows.
. . . =di−N=di=di+Ndi+2N= . . . [Expression 2]
That is, for example, in a case of N=3, as shown in
As described above, the repetitive control portion 5 is a type of learning control system which reduces the deviation e by continuously performing the repetitive operation using the deviation e of one preceding cycle.
As described above, the switching of the cycle is performed when the reset signal output from the reset signal generation portion 4 is input to the repetitive control portion 5.
This reset signal is generated using a pressure waveform of the compressor in Example 1.
The generation of the reset signal in the reset signal generation portion 4 will be described based on
In this example, a case in which the discharge pressure fluctuates 10 times during one rotation of the compressor will be shown as an example.
Regarding a DC component of the pressure signal obtained as described above, a part below the dotted line is cut using a high-pass filter as shown in
As shown in
Therefore, as shown in
Since it is not necessary for the low-pass filter 6 to control the deviation of a high frequency component by following a target rotation number, a high frequency component is cut from an output signal u of the repetitive control portion 5 and output to an adder 8.
In this example, in the estimation of the rotation speed of the motor in the estimated rotation speed calculation portion 7, an error related to the rotation of the motor is calculated once and used to estimate the rotation speed, and thus the repetitive control portion 5 is allowed to be applied and the estimation accuracy of an estimated rotation speed ω_
In this example, an angle error is used as the error related to the rotation.
Based on such a purpose, the estimated rotation speed calculation portion 7 has a flux observer 7a, an angle error calculation portion 7b, and a speed calculation portion 7c.
In the flux observer 7a, identification is performed using a mathematical model of the motor based on a dq-axis current value idg output from a motor model 13 and a command dq-axis voltage value Ve output from a current proportional integral controller 11 to calculate motor current flux estimation errors Δλγ and Δλδ of a γ axis and a δ axis, and the result is input to the angle error calculation portion 7b.
The angle error calculation portion 7b calculates an angle estimation error θ_
The speed calculation portion 7c obtains an estimated rotation speed value ω_
The adder 8 adds the output value from the LPF 6 to the rotation speed difference (deviation e) from the subtracter 3, and outputs the obtained value to a speed proportional integral controller (speed PI controller) 9.
The speed proportional integral controller 9 performs PI control on the output value of the adder 8 using a proportional gain and an integral gain constant to calculate a command motor current iθ which is a drive command signal (which is the same as a torque command value signal), and outputs the obtained value to a subtracter 10.
The subtracter 10 subtracts the output value idq from the motor model 13 from the command motor current iθ and outputs the result to the current proportional integral controller (current PI controller) 11.
The current proportional integral controller 11 performs PI control using a proportional gain and an integral gain constant based on the correction command motor current output from the subtracter 10 by dividing into a command current of the d axis and a command current of the q axis, and outputs an axis voltage command value Ve to the estimated rotation speed calculation portion 7, a subtracter 12, and an inverter 20.
The current proportional integral controller 11 and the speed proportional integral controller 9 correspond to the drive command signal generation portion of the invention.
The subtracter 12 subtracts a value obtained by multiplying the estimated rotation number by a torque constant K from the output value from the current proportional integral controller 11 to calculate a motor voltage V0′, and outputs the calculated value to the motor model 13.
The motor model 13 which is used to show characteristics of the motor from inductance L and winding resistance R of coils of the motor calculates an actual motor current ie′ (which is the same as the motor torque) from an output Ve′ of the subtracter 12, L, and R, and outputs the result to an adder 14. K is a torque constant.
The adder 14 adds the output value of the motor model 13 to the output value from the sin function generator 19, and outputs the result to a load model 15 as a motor torque T including a load fluctuation component.
The load model 15 which is used to show load characteristics of the electric compressor from an all-inertial moment J and a viscous friction coefficient D of the motor shaft obtains an estimated rotation speed ωout from the output value T, J, and D based on an equation of motion of the motor.
The estimated rotation speed ωout is output to a feedback gain portion 16 and an integrator 17.
The feedback gain portion 16 calculates a correction voltage Ve″ by multiplying the estimated rotation speed ωout by the torque constant K, and outputs the result to the subtracter 12.
The integrator 17 integrates and converts the estimated rotation speed ωout into a rotation position (rotation angle), and outputs the result to a coefficient multiplier 18.
The coefficient multiplier 18 multiplies the rotation position obtained by the integrator 17 by n (order of rotational fluctuation) and outputs the result to the sin function generator 19.
In the sin function generator 19, a sin function depending of the rotation angle obtained by the coefficient multiplier 18 is generated and output to an adder 14 as a load fluctuation component of the electric compressor.
The command voltage of the d axis and the command voltage of the q axis of the motor obtained by the current proportional integral controller 11 are output to the known inverter 20 to drive and control the motor.
Next, results of a simulation in which a rotation error is generated by applying a disturbance to the control device for an electric compressor configured as described above will be described.
A noise signal of 1 rad/s as a disturbance signal nd was applied to the estimated rotation speed ωout obtained in the generation of a delay time of the load model 15 to obtain an estimated rotation speed having a rotation error.
The order n of the rotational fluctuation was set to 10, Wref and Wref_min were set to 2π×10 rad/s, and the sampling cycle Ts was set to 1.0×10−4 s. In addition, the number of stages N of the delay device 5a was set to 1,000, and in a conventional repetitive control portion, the reset signal was set to be output when i was 1,000 in order to make a comparison.
The resistance coefficient R was set to 0.85Ω, the inductance L was set to 1.2 mH, the viscous friction coefficient D was set to 8.34×10−5, the inertial moment J was set to 0.7×10−4, and the torque coefficient K was set to 0.076 Nm/A.
The results are shown in
In the repetitive control of Example 1, when the simulation is performed with the same settings as the above-described conventional normal control, it is found that as shown in
For simplicity,
Next, a reason for accurately setting a reset timing for each rotation in Example 1 will be described based on
In
Based on the deviation between a command rotation speed and an estimated rotation speed in one previous rotation, a command speed in the next one rotation is corrected as indicated by the broken line. When the value of the command rotation speed is corrected to the increase side in a case in which the estimated rotation speed is smaller than the command rotation speed, and the command rotation speed is corrected to the reduction side in the reverse case, the value of the estimated rotation speed becomes gradually consistent with the command rotation speed, and thus the correction amount does not change.
Therefore, the repetitive control can be applied only to a cyclic fluctuation, and thus when the reset timing does not exist for each rotation (that is, when the reset timing does not match the load fluctuation cycle), the above-described correction does not successively act. Accordingly, reset should be accurately performed for each rotation.
In Example 1, in a compressor in which a cyclic load fluctuation is generated, since one rotation can be accurately determined from a pressure waveform of the compressor, the repetitive control can be applied well.
The control device for an electric compressor of Example 1 can obtain the following effects.
That is, in the control device for an electric compressor of Example 1, the repetitive control portion 5 performs a repetitive operation using a rotation speed difference between a target rotation speed ωref of one preceding cycle and an estimated rotation speed ωout to reduce the rotation speed difference and to thus suppress a disturbance. However, in that case, since the cycle switching timing in the repetitive control portion 5 is determined according to the pressure fluctuation of the compressor in the reset signal generation portion 4, the drive motor of the compressor can be successively controlled with respect to the load fluctuation having complicated frequency components even when the motor is controlled in a sensorless manner.
In addition, in the reset signal generation portion 4, since the number of load fluctuations of the compressor is counted by detecting a discharge pressure of the compressor, the timing of one cycle can be easily and securely detected.
The invention has been described based on the examples. However, the invention is not limited to these examples, and even when there are modifications in design and the like without departing from the gist of the invention, the invention includes the modifications.
For example, in the reset signal generation portion 4, the number of load fluctuations of the compressor is counted by detecting a discharge pressure of the compressor. However, in place of this, the number of load fluctuations of the compressor may be counted by detecting a suction pressure of the compressor to determine the timing of one cycle.
In addition, the control device for an electric compressor of the invention is not limited to control devices for compressors of vehicular air conditioning devices and may be applied to control devices for other compressors.
The present application is based on Japanese Patent Application No. 2012-245009, filed Nov. 7, 2012, the content of which is incorporated herein by reference. In addition, all references cited herein are incorporated by reference in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-245009 | Nov 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/078543 | 10/22/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/073365 | 5/15/2014 | WO | A |
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