JPH0491693A - Driving method of brushless motor - Google Patents

Abstract

PURPOSE:To drive a brushless motor stably by detecting currents made to flow through an armature winding, changing currents into a voltage signal, converting the voltage signal into an arithmetic quantity at the next stage and conducting specified arithmetic operation. CONSTITUTION:The armature windings iu, iv of a brushless motor are detected as voltage signals proportional to current values by a current detecting means, and the voltage signals are converted as shown in formula by a current conversion means 8. igamma and idelta obtained by conversion by the current conversion means are input to an arithmetic means 10. On the other hand, wm deg. as the command value of the number of revolution of the brushless motor and the set value LAMBDAdeltaof primary magnetic flux are input to the arithmetic means 10. The arithmetic means arithmetically operates voltage vgamma, vdelta, gamma1 to be applied to the brushless motor by specified control formula. Signal waves eu, ev, ew for forming switching signals are output from vgamma, vdelta, gamma1 to a pulse width modulation means by a coordinate conversion means. The pulse width modulation means feeds back the output voltage of an inverter so that the output voltage is not subject to the effect of DC voltage Vd.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a brushless motor, and is obtained by detecting the current flowing through the armature winding while maintaining the primary magnetic flux of the brushless motor at a predetermined value, and converting the signal. By detecting the relative position of the magnet rotor and armature winding using a signal and obtaining a commutation signal, a brushless motor can be operated quickly from startup to transient and steady operation while responding to the load. This relates to a drive method.a.Conventional technology experts A brushless motor requires a magnetic pole position detector to detect the magnetic pole position of its rotor.For example, when this brushless motor is used in an air conditioner compressor, Since the reliability of the detector cannot be guaranteed under high pressure conditions, it is impossible to drive the compressor with the method using the detector. Therefore, in this case, the magnetic pole position detector is not used and the A method has been used in which a commutation signal is generated based on the signal obtained by converting this detection signal by detecting a voltage signal generated by the load.Then, the rotation speed is detected based on the commutation signal, and the rotation speed is detected based on the signal obtained by converting this detection signal. However, the above-mentioned method of using voltage signals induced in the armature windings has the following problems. Especially when driving at low rotation speeds, the voltage signal induced in the armature winding is small, so it is susceptible to external noise and lacks detection accuracy and stability. Generally speaking, in the initial stage of driving, a forced rotating magnetic field is applied to the armature winding, and the rotor rotates due to this rotating magnetic field, causing the armature winding to rotate. After a sufficient voltage signal is induced in the motor, the system switches to a method in which a commutation signal is obtained based on the voltage signal.Therefore, the drive method includes a forced rotation operation period and an operation period using a commutation signal.
When starting up from a stopped state, the above-mentioned periods were switched midway through, so switching could fail depending on the load condition.During the forced rotation operation period, a large current flows through the armature windings, so In order to solve the above-mentioned problems, which may cause demagnetization of the rotor magnet and impose an excessive load on the power transistor for driving the motor, resulting in an increase in the capacitance of the component elements and reliability, the present invention has the following configuration: A brushless motor having a three-phase armature winding connected to a non-grounded point, a DC power supply, a group of semiconductor switching elements for supplying or interrupting current to the armature winding, a magnet rotor, and an armature winding. , a rotation speed command means, a current detection means for detecting the current flowing in the armature winding and converting it into a voltage signal, a current conversion means for converting the voltage signal into a calculation amount for the next stage, and a predetermined calculation. This is a brushless motor driving device comprising a calculation means for performing coordinate conversion, a coordinate conversion means for converting the coordinates of the calculation result, and a PWM control means for issuing a switching command to the group of semiconductor switching elements based on this signal.

Operation The present invention has the above-described configuration, and the brushless motor starts and ends.
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of a brushless motor drive device in an embodiment of the present invention.

In Fig. 1, l is a DC type, #2 is a semiconductor switching element, 3 is a brushless motor, and 4 is an electric pre-winding device.
5 is a magnet rotor, 6 is a current detection means, 7 is a pulse width modulation amount ratio, 8 is a current conversion means, 9 is a coordinate conversion means, 1
0 is the calculation amount Q, 11 is the rotation speed command means, 12 is the magnetic flux command, and 13 is the start command means.

The control method of the present invention will be explained below. The armature windings iu and iv of the brushless motor are detected by the current detection means as a voltage signal proportional to the current value, and this is converted into the following equation (1) by the current conversion means 8. Perform the transformation shown.

θ+= (w+dt, w+: lγ, lδ obtained by conversion by the inverter angular frequency current conversion means are manually input to the calculation means 10. - person The calculation means 10 is inputted with w, which is the command value of the rotation speed of the brushless motor. , ° and the set value Δδ of the primary magnetic flux are input.

The calculation means calculates the voltage v7. to be applied to the brushless motor using the control formula shown below. Calculate vδ and θ1. Change the number by using the coordinate conversion means to convert v7. A signal wave e for generating a switching signal from vδ, θ1 to the pulse width modulation means
u, ev, e- are output by the pulse width modulation means (by the pulse width modulation means).Even if feedback is performed so that the output voltage of the inverter is not affected by the DC voltage Vd, the control formula will be explained below. The −δ axis is a coordinate system that rotates in synchronization with the rotating magnetic field created by the armature winding of the brushless motor.
If the shaft is advanced by an angle φ, the voltage equation of the brushless motor at this time is equation (2): a λ py=L+1r−Aθsinφ λ pδ=L+ i δ+AθcosφR++L+P
: To the impedance of the armature winding 〇 : Constants λpγ and λpδ proportional to the field magnetic flux are the γ and δ axis components of the primary magnetic flux linkage. Here, the -th order magnetic flux λp7. The characteristics when λpδ is controlled as shown in equation (3) are explained below. Assuming n, the equation (5) becomes λr=-Aθsinφ
, λδ=Aθcosφ---(4) τ=n(λδIT
−λ7iδ) = n[(λpδ−L+iδ)・1r−(λpr−L11
γ)・l δ co=n(λpδi7−λpyiδ)−・−(5)=nAδ
iγ Therefore, a torque proportional to i7 can be obtained, and on the other hand, equation (7) can be obtained from equation (6).

λpr=L1ir+λ7=o...(6) lθ° is a set value, and as explained later, during operation, φ=-π/
6 to π/6, so equation (8) holds true.4 If the angular velocity of the brushless motor is wm, equation (9) holds, so lγ is used in the loop that determines the inverter frequency W1.
All you have to do is give feedback ~W I= n Wffl
+φ −−−−(9) Up to this point, the force assuming the above equation (3) (Next, we will discuss the control method to realize the equation (3).λpδ=L+iδ+λpδ...(10)(
Substituting equation (10) into equation (2) and rearranging it, we get equation (11).

Pλδ=-Aθsinφ・φ knee Aθφ・φ”= P(L+i θ°φ”
/2) Knee P (L+ir'/2・l θ°)...
(l 2) Therefore, we can introduce equation (13) as an auxiliary variable here. We can also rewrite equation (12) as equation (14): λ pδ= L + (i δ−i r”/2・
l θ°)... (13) If the armature resistance R is known, set the second term on the right side of equation E (14) to 0. v7. vδ can be determined. In other words, if we write them as v7Vδ°, equation (15) holds true, but v 7”==Ri 7+w+λpδ−Wlλpδ=Ri
70 w+L+ iθ"+w+L+ (i r'/2i
θ°−1δ) Vδ゛=R1δ− δλpδ=Ri δ
δL1(ir”/2i θ°−1δ) (15) It can be seen that this group − order magnetic flux control system operates as a stable system with the eigenvalue equation (16) λ1.λ2−− δ/
2± (Kδ/2)"w+"Here, how to control the operating frequency W1 will be described below, assuming that the -order magnetic flux can be controlled stably and quickly.

When a new speed command wm" (=wm1) is given to the motor operating at wm=wmθ, the magnetic flux command means nw
Create a primary magnetic flux command W1° that increases linearly from mθ to n W m I If the brushless motor is operated at L w+°, the −th order magnetic flux will be properly applied and unstable phenomena such as disturbances and step-outs will occur. There is a danger of falling into the phase difference angle φ
Here, the stability of the system when controlled as shown in equations (17) to (18) is shown below.

From λpr=o, λγ=-L+i72-Aθφ...(
17) Wl = WI° + (Kpλ7 + K IλT)”-・
- (18) The part in parentheses in equation (18) is the feedback term, and Kp and Kp correspond to the gain of the PI compensator.

From equation (19) to equation (20), j=o, λ7
In the steady state where =Q, nwm is W1°0K +λγ
is equal to and varies depending on the load4. Let λδ = λδθ + λδ, etc., and take any operating point (W, θ,
The equation for minute changes around λγθ, λδθ) is found to be PλT=−φλδ from equation (4). Also, if φθ = 0... (20) The equation for (20) is (21) as follows. )−1 nλδθWm”10nλ (21) −X Assuming an inertial load, from equation (22), (23)
Even if the formula is obtained, JPw=nAθi 7...(22) Pwa=nA
θ/J・1r=-nA θ/L + J・
λT...(23)(2
4) If we write equations (22) and (23) above using equations, we get (2
5) Equation becomes.

λ7=-L+i7 -1°(24)
Since λδθ=AθCOSφ, φ is 1π/6 to π/6
In this case, λδθ〉0, and the system is stable over the entire range.As mentioned above, by controlling the torque proportional to the brushless motor torque, a stable brushless motor can be achieved based on a consistent control theory from startup to transient and steady operation. A motor can be driven.

In this embodiment, the power conversion means, calculation means, and coordinate conversion means are used (some or all of which may be performed by a microcomputer.

Effects of the Invention As described above, the present invention performs control based on the control formula using the configuration described above, thereby stably driving a brushless motor based on a consistent control theory from startup to transient and steady operation. be able to. Therefore, there is no need to switch between the forced rotation operation period and the operation period using commutation signals as in the past, so it is possible to prevent step-out at startup, and it is also possible to give a command value that matches the required starting torque at startup. Therefore, it is possible to avoid excessive current flowing through the armature windings or imposing an excessive load on the power transistor for driving the motor, which is the case with conventional methods.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the present invention. Fig. 2 is an explanatory diagram showing the positional relationship between the rotor and the armature winding. , 3... Brushless motor 4... Armature winding 5... Magnet rotor, 6... Current detection element, 7... Pulse width modulation hand wash 8... Current conversion means, 9...Coordinate conversion means, 10...Calculation means, 11...Rotation speed command take-off 12...Magnetic flux command means, 13...Start command amount ratio agent Name Patent attorney Shigetaka Awano 1 person Figure 1 a Soaked electric row @ dedicated switch 2g 1 child t-9 Electrolytic erosion Tetsubetsu tightening magnet rotor treasurer ? ! In this article, I will teach you how to use the power to eat electricity! Yu hand 6 ffi No. 11 role rotating kan ■ 1 kettle No. nuclear magnet φ finger 9 hen 6 Ki h 1 straw change stage

Claims (1)

[Claims] While maintaining the primary magnetic flux of a brushless motor having a magnet rotor and an armature winding at a predetermined value, armature winding current is detected in two or more of the three phases, and the detection signal is used to rotate in synchronization with the rotating magnetic field. The brushless motor detects the rotor position by estimating the phase difference angle between the magnet rotor and the armature winding using a signal component proportional to the torque of one of the signal components obtained by decomposing the coordinate system into axial components. A method of driving a brushless motor that generates a commutation signal.