KR100315258B1 - encoder system for srm driving - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder device for driving a switched reluctance motor. In the conventional phase switch ON / OFF method, the degree is largely determined by the sampling cycle of the microprocessor, and the steady state of the SRM at high speed is particularly high. It solved the problem of driving unsafe. To this end, the encoder device for driving SRM according to the present invention comprises: a disc configured to rotate in engagement with a rotating shaft of an electric motor; A first pattern (FW) formed on the disc to output pulses having the same period as the on time of the gate signal of the switching element constituting the SRM drive inverter when the disc rotates; A second pattern (BW) having an appropriate phase difference with the first pattern so as to form the same gate signal during forward / reverse operation of the SRM with reference to the inductance profile of the SRM, and formed inside the first pattern; Output signals (FW, BW signals) generated by the first pattern and the second pattern in accordance with the rotation is processed into a gate signal having the same number as the number of phase of the SRM, so that the gate signal is driven SRM And a logic circuit for driving the SRM by sequentially turning on the inverter switching element. When designing the SRM controller using the SRM encoder device according to the present invention as described above, the switch ON, OFF angle delay is always constant regardless of the operating speed of the SRM, so if properly compensated, always ON / OFF switching at the correct position This enables the stable operation in a wide range of speed ranges, as well as the advantages of forward and reverse operation. In addition, the SRM controller does not require a high-speed microprocessor, and since the low-cost encoder is used, there is an advantage that stabilization and low cost of the SRM drive system can be realized. Therefore, the possibility of practical use of SRM is further enhanced.

Description

Encoder device for SM drive {encoder system for srm driving}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device of a switched reluctance motor, and more particularly, to an SRM drive encoder device capable of performing ON / OFF switching at an accurate position and enabling stable operation in a wide range of speed ranges. It is about.

With the rapid development of technology for power semiconductor devices, high-speed switching and large capacity of devices are possible, and according to industrial mechatronics, the development of motors with multifunction and high performance is being actively performed. Switched reluctance motor (hereinafter referred to as SRM) is a single excited machine, simple in structure and inexpensive, stable against shoot-through fault by separating each phase, and speed-torque characteristic of DC motor. It has a wide speed variable range, high speed and reverse rotation characteristics, and it is strong. Research on SRM is being conducted in advanced countries, expanding its field of application to home appliances, electric vehicles, aircraft and industries.

SRM is an electric device with simple electromagnetic structure, high efficiency, high torque / inertia ratio, variable speed operation in a wide range, etc., and is expanding its application area to home appliances, electric vehicles, aircraft, and industrial fields. And development is underway.

The driving principle of the SRM is that the rotational force is generated as the rotor is forced in a direction in which the magnetic resistance of the excited magnetic circuit is minimized. This phenomenon implies a physical meaning of minimizing the energy of the system by converting the energy stored in the system into mechanical energy. Devices using this principle include simple actuators, lifting magnets, linear solenoids, relays, step switches, and the like.

In order to maximize the reluctance torque, SRM has both the rotor and the stator structure of salient pole type, and the winding is wound around the stator only, so that the excitation power is intermittently and sequentially applied to each winding line. Let's do it.

The stator winding wire of the SRM requires information on the rotor position angle due to the characteristics of the torque generating mechanism that should be excited in synchronization with the rotor position. Rotor position angle detection generally uses an encoder or resolver, but the higher the resolution of such a mechanical external position sensor, the higher the unit cost. Therefore, in order to reduce the burden on the installation cost, the research on the sensorless driving to use a low-cost encoder, or to completely remove it has been actively conducted. This conventional technique uses a microprocessor to turn on / off the switches of each phase of an inverter driving SRM. However, in the SRM control method by the microprocessor, the degree of ON / OFF of the phase switch is limited by not only the resolution of the encoder but also the sampling cycle of the microprocessor. In this case, the higher the driving speed of the motor, the lower the accuracy of the phase switch ON / OFF angle by the microprocessor, which causes a problem that the normal operation state becomes unstable.

SRM is a motor that uses reluctance torque. In order to make the best use of it, the stator and the rotor are usually of salient structure, and the winding is wound around the stator only. At this time, the torque is generated in the direction of minimizing the reluctance of the magnetic circuit, and the magnitude of the generated torque is the current i flowing in the phase winding as shown in the following equation (1). Inductance for the square of and the rotor position angle θLProportional to the rate of change.

Therefore, the rate of change of the inductance should be maximized and the torque generation section should be utilized to the maximum by establishing and extinguishing the current corresponding to the load at the ON / OFF time of each phase switch. When voltage is applied to the stator winding of SRM, the equivalent voltage equation is given by the following equation (2).

only, : Mechanical angular velocity of the rotor [rad / s]

1 shows phase current waveforms A, B, and C according to phase inductance and ON / OFF angle change of the phase switch. In Fig. 1, θ _min and θ _max represent the rotor angles when the poles of the stator and the rotor start to overlap each other and coincide completely. Figure 1 (a) shows the switch OFF angle ( ) And keep the ON angle ( , , ), And the ON angle changes, the magnitude of the current established at the start of the torque generation section is different, and this value is almost the ON angle (ignoring the winding resistance of the motor). , , Is proportional to). In addition, the phase current waveforms A and C of the three waveforms A, B, and C have a positive or negative change rate of the current in the torque generation section, so that the generated torque is not constant and the torque pulsation is severe. However, the phase current waveform of B having a constant current in the torque generation section generates smooth torque when the inductance change rate is constant, and becomes a reference current for efficiently operating the motor due to less torque pulsation.

Figure 1 (b) shows the switch ON angle ( ) And the OFF angle ( , , ), The OFF angle ( , , ) Is closer to the maximum inductance point, which increases the utilization of the torque generating area, which is beneficial to the generation of positive torque, but if it is too large, it may be affected by the negative torque, causing torque pulsation and decreasing the mechanical output. Therefore, the switch ON angle should be determined so that the shape of the phase current becomes smooth current regardless of the load torque and the operating speed, and the OFF angle should be adjusted so that no negative torque is generated so that the reluctance torque can be effectively used, and a small pulsation torque can be obtained. have.

A general configuration of a conventional SRM controller, which is widely used thus far, is briefly shown in FIG.

2, the controller 10, the inverter 20 using the IGBT module, the current and position sensor 40, the electric motor 30 and the like. The controller 10 is composed of a PWM generator 5 for controlling the phase current i, a speed controller 3, a speed calculator 9 by an output signal of the encoder 40, and the like. And the speed controller 3 controls the difference (1) between the reference speed (W ^* ) and the actual speed (W) to make a reference torque (T ^* ). Based on this reference torque T ^* and the detected rotor position angle θ, a reference current i ^* capable of generating a desired torque is obtained from the table 7. In addition, each current controller compares the reference current (i ^* ) with the phase current (i) obtained through the current sensor so that the actual current follows the reference current (i ^* ).

In such a general driving system, since the SRM needs to be switched according to the rotor position angle, position information of the rotor is essential. In general, the rotor position angle is usually detected by installing a resolver or encoder on the motor shaft, and in particular, using an incremental encoder in consideration of the unit cost. The incremental encoder obtains the output pulse number according to the position as a digital value by an up or down-counter, and uses the microprocessor to control the signals of each phase.

However, the phase switch ON / OFF control method is highly dependent on the sampling cycle of the microprocessor. In particular, the higher the higher the speed, the lower the accuracy, which may lead to unstable operation of the SRM. There is a problem. Therefore, such a controller is generally implemented as a high-speed DSP to significantly reduce the sampling period, but there is a limit to the maximum speed for stable operation. In addition, there is a problem in that the use of a high-speed DSP, the price of the controller becomes expensive, which acts as a factor to inhibit the spread of SRM.

Accordingly, an object of the present invention is to provide a low-cost SRM driving optical encoder device suitable for stable driving of SRM in order to solve the above problems.

1 is a phase current waveform diagram according to changes in ON and OFF angles of a switching device.

2 is a block diagram of an SRM controller according to the prior art.

3 is a change in the switching angle according to the speed of the SRM.

Figure 4 is an encoder for driving the SRM according to the present invention.

5 is an output waveform of the encoder for driving the SRM according to the present invention.

6 is an embodiment of an SRM controller according to the present invention;

7 is a schematic diagram of the structure and inductance profile of the SRM used in the verification of the present invention and a drive inverter circuit.

8 is a block diagram and operating waveforms of a current controller according to the present invention;

9 is a block diagram and operation waveform of the voltage controller according to the present invention.

10 is a gate signal of each phase at the forward / reverse rotation of the SRM by the SRM drive encoder according to the present invention.

11 is a gate signal and phase current waveform of the switching element when the SRM is 6000rpm.

Figure 12 is a gate signal and phase current waveform of the switching element when the SRM is 1800rpm.

Figure 13 is a comparison of the phase current waveform in the prior art and the present invention.

14 is a velocity and current waveform during SRM startup according to the present invention.

Figure 15 is a phase current waveform at the time of variable load torque of the SRM to which the present invention is applied.

<Description of the symbols for the main parts of the drawings>

10 controller 20 PWM inverter

30: electric motor 50: 80196KB

55: current controller 60: voltage controller

65, 69: decoder 67: counter

73: analog switch 80: classic inverter

In order to achieve the above object, the encoder device for driving an SRM according to the present invention comprises: a disc configured to rotate in engagement with a rotating shaft of an electric motor; A first pattern (FW) formed on the disc to output pulses having the same period as the on time of the gate signal of the switching element constituting the SRM drive inverter when the disc rotates; A second pattern (BW) having an appropriate phase difference with the first pattern so as to form the same gate signal during forward / reverse operation of the SRM with reference to the inductance profile of the SRM, and formed inside the first pattern; Output signals (FW, BW signals) generated by the first pattern and the second pattern in accordance with the rotation is processed into a gate signal having the same number as the number of phase of the SRM, so that the gate signal is driven SRM And a logic circuit for driving the SRM by sequentially turning on the inverter switching element.

In addition, the logic circuit has a same cycle as the BW signal and a clock-only clock signal for extracting a synchronization signal having the same period as the FW signal and available for forward rotation of the SRM from the logical relationship between the FW signal and the BW signal. A clock extraction circuit for extracting a reverse rotation clock signal that can be used as a synchronization signal suitable for reverse rotation of the SRM; And a sequential circuit processing the gate signal for sequentially turning on the switching element of the inverter in synchronization with the output signal of the clock extraction circuit.

The sequential circuit further includes a counter for counting the output of the clock extraction circuit as a clock input signal; And a decoder which decodes the output of the counter and converts the output of the counter into consecutive sequential signals equal to the number on the SRM.

In addition, the clock extraction circuit includes a decoder for decoding a logical relationship between the FW signal and the BW signal; And a selection circuit for selecting a forward-only signal and a reverse-only signal among the outputs of the decoder.

The selection circuit is characterized in that an analog switch is used.

Hereinafter, an SRM driving encoder apparatus according to the present invention will be described in detail with reference to the accompanying equations and drawings.

If the microprocessor is used to control the phase switch of the SRM, the control accuracy is determined by the resolution of the encoder. ) And the change in rotor position angle during the sampling period ( Is determined by That is, the mechanical position angle resolution in encoder with pulse number per rotation N _p is irrelevant to the speed of the motor.

Also, the change in rotor position angle θ during the sampling period ( ) Depends on the speed of the motor and the value is as shown in the following equation (4).

T _s : Sampling period of the microprocessor [ s ]

Variation of ON and OFF angles in the phase switch control method using a microprocessor ( ) Is determined by the resolution of the encoder and the sampling period of the microprocessor, and the value is given from Equation (3) and (4) as shown in Equation (5).

The magnitudes of the ON and OFF angular fluctuations given by Equation (5) are shown in FIG. 3 according to the motor speed.

3, as the speed increases, the error due to sampling increases with a slope of 6T _s . In addition, if the resolution of the encoder and the position angle variation of the microprocessor do not appear as integer multiples, the lower harmonic components appear in the switching angle control. As a result, the same low-order harmonic components appear in the torque of the SRM, which adversely affects stabilization operation.

In general, when the speed of the motor is low, the variation of the position angle due to sampling is caused by the angular resolution of the encoder. ₎ Smaller than the variation in the ON / OFF angle is governed by the variations in the position of each sample, and the degree are subjected to controlled by the resolution of the encoder. However, the higher the speed of the motor, the more the encoder resolution remains unchanged, but the positional angle fluctuation by sampling becomes large.In this case, the variation of ON / OFF angle is subject to the positional angle fluctuation by sampling, and the degree is It is governed by the resolution of. Therefore, high-speed sampling is required to control the ON / OFF angle with a resolution similar to that of an encoder. A high-performance microprocessor is essential for this purpose. In order to control a high-precision phase switch without the help of such a high speed microprocessor, a special control method is required.

Therefore, in the present invention, in order to precisely control the on / off of the phase switch using a simple encoder, the encoder for driving the SRM as shown in FIG. 4 has been developed.

Referring to Figure 4, the disk has two pulse trains FW pattern and BW pattern As shown in FIG. 4, the two photocouplers provided in the pulse trains FW and BW are arranged in the same position.

The photocoupler is composed of a light emitting element and a light receiving element, and is adapted to generate an FW pulse and a BW pulse when the FW pattern and the BW pattern of the encoder rotate in response to the shaft of the motor. Most optical encoders and encoders according to the present invention are basic. Similar in principle. However, in the present invention, in order to configure the FW pattern and the BW pattern, in order to use for driving the SRM, the phase difference between the two patterns (FW, BW) should be determined by referring to the SRM inductance profile, not uniform, and configured accordingly. This is the difference from ordinary encoders. Most conventional encoders have a double or triple pattern, but the phase difference between the patterns As uniform. The FW pattern is used for forward rotation and the BW pattern is used for reverse rotation.

The period δ of the pulse of the encoder according to the present invention is determined by the following equation (6).

Where P _s is the number of poles of the stator and P _r is the number of poles of the rotor

According to Equation (6), when the number of stator poles and rotor poles of the SRM to be controlled is determined, the value of δ is substituted into Equation (6) and the FW pattern of the encoder is configured accordingly. Of course, if it is commercially available, an encoder having a calculated value according to equation (6) may be purchased and used for control.

The pulse width δ of Equation (6), which will be described later, is the width of the position angle that one phase of the SRM drive inverter should be responsible for in order to generate continuous torque in the SRM. Therefore, the phase difference between the internal pulse train BW and the encoder external pulse train FW ) Is the angle to set the proper ON / OFF angle in the reverse rotation operation of the SRM, which is determined by the inductance profile of the SRM. Therefore, in order to configure the encoder according to the present invention, the inductance profile of the SRM to be controlled must be known in advance, and the phase difference between the FW pattern and the BW pattern of the encoder is determined by this profile. ) Should be determined and configured appropriately.

The encoder's FW phase pulse has two pieces of information. The first is the position angle of the rising edge of the pulse, and this angle is used for turning on and off the phase switch of the inverter for driving SRM. The second information is the pulse width, and this value is used as the phase switch ON holding angle.

FIG. 5 shows an inductance profile L _A for one phase (phase A) of an 8 / 6-pole SRM, the FW phase and BW phase signals of the encoder, and the gate signals (Phase A FW, Phase A BW) at this time. In Fig. 5, β represents a period of the inductance profile of the SRM, and its value is expressed by the following equation (7).

Α, which becomes the ON angle of the phase switch from the maximum point of the phase inductance profile, is a value set by the operating conditions of the motor or the inductance profile, and the OFF angle is automatically given when the ON angle is given. Ε is the OFF angle of the phase switch on the basis of the maximum point of each phase inductance, and is determined by α and δ and the relationship is expressed by the following equation (8).

Encoder's BW phase is used to turn the phase switch ON and OFF during reverse rotation. It is possible to set any phase switch ON angle on the inductance profile. Also, the direction of rotation can be detected by applying the FW phase and BW phase as the encoder's forward and reverse judgment circuits.

For the forward rotation of the motor by the encoder shown in Fig. 4, each phase switch may be used as an ON signal every four counts as the FW phase clock based on Set_FW. For reverse rotation of motor, each phase switch is used as ON signal every 4 counts as BW phase clock based on Set_BW. For the forward / reverse rotation judgment of the motor, the FW and BW phases are used as they are in the existing encoder.

Next, the SRM controller using the SRM drive encoder according to the present invention for detecting the rotational speed and position of the SRM will be described. An embodiment of an SRM controller is shown in block diagram in FIG. And through the experiments will be described the performance of the encoder and the SRM controller using the same according to the present invention.

The SRM used in the experiment is a pole of the stator and the rotor of 8/6, 400W, 3000rpm, 160V equipment has a structure as shown in Figure 7 (a), to drive it, the conventional classic inverter as shown in Figure 7 (c) Was used. The inductance profile of this motor is shown in Fig. 7 (b), which changes the rotor by 1 ° and sets the current limit to 7 [A] and applies a voltage pulse until the limit is reached and then the current waveform at that time. After measuring with an oscilloscope, the inductance was calculated from the measured voltage and current data in consideration of the winding resistance of the motor. Therefore, the inductance profile obtained is a relatively accurate value that can represent the dynamic operation characteristics of the SRM.

Next, the δ value which is the pulse width of the FW pattern of the encoder to be used for the rotational speed and the position detection of the SRM having the characteristics as shown in FIGS. 7 (a) and 7 (b), Is determined by referring to the inductance profile of Equation (6) and FIG. 7 (b), and configured the encoder according to the determined value. Since it is an 8 / 6-pole SRM, substituting in equation (6) above is δ = Becomes Thus, δ = FW was configured. And Was set appropriately.

Next, the configuration of the SRM controller will be described in detail with reference to FIG.

6, the controller on the left side and the inverter 80 on the right side are large, and again the controller is a microcontroller 80196KB 50 and a peripheral circuit 71, ABS, for accepting an external input from the 80196KB 50. COMP), current controller 55 and voltage controller 60 for controlling inverter 80 using output signal of 80196KB (50), decoder 65,69, analog switch 73, counter 67 It consists of digital logic circuit using).

The FW and BW signals are input to the first decoder 65, the clock generation circuit 71, and the HSI0 and HSI1 terminals of the 80196KB (50), and the D0 output and the D2 output of the first decoder 65 are analog switches 73. Is connected to the input side, and the output of this analog switch 73 is input to the clock terminal of the counter 67. The analog switch 73 selects one of the D0 output and the D2 output of the first decoder 65 and outputs the counter 67 to the P1.3 terminal output signal of 80196KB 50. The output signal of the P1.3 terminal of the 80196KB 50 is the selection signal Dir for selecting the forward / reverse direction.

The clock generation circuit 71 is a logic circuit configured to measure the speed of the motor by the M / T technique, which is a speed calculation method using an encoder in 80196KB (50). Therefore, the FW signal and the BW signal, which are output signals of the encoder, are input to the clock generation circuit 71 and processed into a single clock signal CLK and an up-down signal UP / DOWN.

The output signal of the clock generation circuit 71 is input to the timer 2 (T2CLK, T2UPDN) at 80196KB (50), and configured to calculate the speed (Wr) of the motor by a software method (Wr estimation).

The 80196KB 50 receives the FW signal and the BW signal of the encoder through the HSI terminals HSI0 and HSI1 to detect the phase θ of the motor by an internal program θestimation. In this way, the phase is detected to determine the forward and reverse rotation of the motor.

The digital logic circuit including the first decoder 65, the analog switch 73, the counter 67, and the second decoder 69, which will be described later, is an essential part of the present invention. After completing the configuration, it will be described.

Next, the outputs Q _A , Q _B of the counter 67 are input to the second decoder 69 of the next stage, and the outputs Q1, Q2, Q3, Q4 of the second decoder 69 are connected to the inverter ( The switching element 80, that is, the phase switch Q _AU, Q _BU, Q _CU, Q _DU , is controlled. 6 shows only a circuit for one phase (A phase) of the inverter 80. The circuits for the remaining three phases B, C, and D of the classic inverter 80 are similar to those for the A phase and thus are omitted. A detailed circuit of the classic inverter 80 is shown in Fig. 7 (c). For reference, in FIG. 7C, the switching element Q _CH for controlling the input voltage V _C is omitted.

On the other hand, the output signal of the P1.0 to P1.2 terminal of the 80196KB 50 controls the counter 67, and the output of the second decoder 69 to the P0.4 to P0.7 terminal of the 80196KB 50 ( Q0 to Q3) are input.

The 80196KB 50 detects the outputs Q0 to Q3 of the second decoder 69 through the P0.4 to P0.7 terminals to determine whether the switching sequence is correct when starting or operating the motor. Check by). If a malfunction occurs, the switch state is changed through Port1 (P1.0 to P1.3).

Next, the PWM1 signal output from the PI controller in the 80196KB 50 is input to the low pass filter LPF, and the output of the low pass filter LPF is input to the current controller 55 of the next stage. The output of the current controller 55 is input to the AND gate together with the output of the second decoder 69, and the output of the AND gate is configured to control the phase switch Q _AD of the classic inverter 80. Meanwhile, the PWM0 output signal of the PI controller is input to the voltage controller 60, and the output of the voltage controller 60 controls the switching element Q _CH for controlling the input voltage V _C of the inverter 80. It is structured.

The current controller 55 is configured to make the initial position of the motor constant at the start of the motor, and a detailed configuration of the current controller 55 is shown in FIG.

When driving the motor by the method proposed in the present invention there is no information on the initial position angle of the motor. In order to solve this problem, in this embodiment, the initial position is made constant by flowing a rated current on an arbitrary phase before starting the SRM. The current controller is essential for flowing the initial starting current.

Referring to FIG. 8, the current controller 55 of FIG. 8 (a) is composed of a comparator 57 and a flip-flop 59, and is configured to control current in a peak current control method. In FIG. 8, the current command value I _a _ Ref is an output signal of the low pass filter LPF as shown in FIG. 6, and the actual current I _a _ Real is an emi of the switching element Q _AD of the inverter 80. Current detected by feeding back from the terminal side. Fig. 8B is an operating waveform of each part of the current controller 55. Figs.

Switching period whenever you to enable the set terminal of the flip-flop 59 to turn ON the switch, the actual current (I _a _Real) is increased, the current command value by the comparator (57), (I _a _Ref) and the actual current (I _a _Real is compared and the actual current (I _a _Real) is larger than the setpoint current (I _a _Ref) to enable the reset terminal of the flip-flop 59 to turn off the switch (Q _AD ) shown in Figure 6 to the motor The incoming current is reduced. Due to this current control method, the rapid response of the SRM controller has the same excellent characteristics as the delta modulation method, and the switching frequency can be made constant.

Next, the voltage controller 60 is configured to control the speed of the motor, and a detailed circuit is shown in FIG.

In the control method proposed in the present invention, the ON and OFF angles of the phase switch are constant. Therefore, in order to control the speed of the motor, it is necessary to adopt a current control method or a voltage control method by delta modulation. Since a lot of research has already been made on the current control method, the description is omitted in the present invention. In this embodiment, a decompression chopper circuit is adopted as a variable voltage source, and the voltage controller 60 constitutes a PI controller with 80C196KB (50) as shown in Fig. 6 and inputs the PWM signal of the PI controller as an input. It was configured to.

In the 80C196KB 50, since the PWM counter 67 uses 8 bits, its resolution is about 1/256 of the input DC voltage, which makes it difficult to control a good DC output voltage. Therefore, in this embodiment, a logic circuit using a T flip-flop 61 and an EX-OR 63 as shown in FIG. 9 (a) is applied to a PWM terminal of 80C196KB (50) to increase the voltage resolution to 9 bits of 1/512. Added. Fig. 9B shows the operation waveforms of the parts of the voltage controller 60. Figs.

In order to control the DC voltage, which is the excitation voltage of the SRM, the output of the T flip-flop 61 is set to High by using the START signal at startup, and the ON time and the OFF time are alternately outputted every PWM cycle. Also, to synchronize the PWM, the PWM output is used as an external interrupter (EXT_INT) to write a new PWM value (PWM Ref) to the PWM register inside 80196KB (50) on the rising edge of the PWM output.

Next, looking at the lower left of Figure 6, + VC is connected to one side of the variable resistor, the other side of the variable resistor is connected to -VC, the variable resistor is an absolute value circuit (ABS) and a comparator (COMP) Becomes the input of. The output of the absolute value circuit ABS is input to the A / D converter terminal AD0 of 80196KB (50), and the output of the comparator COMP is input to the P1.4 terminal of 80196KB (50).

The variable resistor is a variable resistor for adjusting the speed of the motor. The speed command value Wr ^* of the user is received as a digital value by using the A / D converter function of 80196KB (50). The A / D converter of 80196KB (50) is not accurate with 8 bits of resolution. Therefore, in the present embodiment, the absolute value circuit ABS and the comparator COMP are added for more precise speed control, and the output of the 8-bit A / D converter and the comparator COMP in the 80196KB 50 are software-configured. The output is ORed to improve the resolution to 9 bits.

Next, a digital logic circuit composed of the first decoder 65, the analog switch 73, the counter 67, and the second decoder 69 in FIG. 6 will be described.

The digital logic circuits 65, 67, 69, and 73 are newly constructed in this embodiment so that the response of the controller is made at a high speed. In the present embodiment, the digital logic circuits 65, 67, 69, and 73 are regarded as part of the SRM controller. However, when the encoder is determined according to the present invention, the schematic configuration of the digital logic circuit is also determined. A digital logic circuit can be thought of as a device and can be regarded as an encoder device.

As described above, the phase switch on / off control method by the microprocessor is largely influenced by the sampling of the microprocessor, and the degree thereof is lowered at a high speed, and thus the steady state operation of the SRM becomes unstable. However, in the present invention, the output signal of the encoder is properly processed using a digital logic circuit, and then a method of controlling the phase switch of the inverter 80 is introduced to speed up the controller. In the present invention, since the microprocessor 50 merely controls the stationary of the motor or checks whether the phase switch on / off signal is properly output from the digital logic circuits 65, 67, 69, and 73, the microprocessor 50 is It does not participate in the generation of the gate signals Q0 to Q3 of the phase switch. The gate signals Q0 to Q3 of the phase switch are automatically generated by a logic circuit composed of the decoders 65 and 67, the analog switch 73, and the counter 67, so that the controller reacts at high speed. Looking at Figure 10 to be described later will be able to confirm this fact.

Next, a 2 to 4 decoder was used as the first decoder 65. As the counter 67, a 2-bit counter was used, and as the second decoder 69, a 2 to 4 decoder was used. The reason for this configuration is explained.

Fig. 10 shows the inductance profile (L _A , L _B , L _C , L _D ) of each phase of the experimental 8/6 SRM by the encoder proposed in the present invention, the outputs of the encoder (FW, BW) and the forward and reverse rotations. The gate signals A, B, C, and D of each phase are shown. Referring to Fig. 10, the gate signals A, B, C, and D of each phase switch are repeated every four counts of the FW and BW clocks. Therefore, it can be seen that the forward signal of the SRM may be used as the ON signal of each phase switch every 4 counts based on the FW phase clock. In addition, it can be seen from FIG. 10 that the reverse rotation of the SRM may be used as the ON signal of each phase switch every 4 counts based on the BW phase clock. Therefore, in order to process the FW phase clock and the BW phase clock into the ON signal of each phase switch, a combination of a 4 bit shift register or a ternary counter (2 bit counter) and a 2 to 4 decoder to make a sequential signal repeated in ABCD phase order It's easy to solve. When using the 4-bit shift register, four control lines are required to set the initial value of the phase switch. However, when the combination of the ternary counter and the 2 to 4 decoder is used, the phase switch can be set using the two control lines. Therefore, in the present embodiment, as shown in Fig. 6, the FW and BW signals are processed into phase switch gate signals A, B, C, and D using a 2 to 4 decoder 67 and a 2-bit counter 69. It was configured to. However, it is also possible to configure using a 4-bit shift register without following this embodiment.

The first decoder 65 and the analog switch 73 are configured to extract the clock signal of the counter 67 from the FW signal and the BW signal. The counter 67 counts in synchronization with the input clock signal and should output a signal having the same period as the input clock signal. Therefore, in the present embodiment, the first decoder 65 is used to extract the clock signal having the same period as the FW signal from the logical relationship between the FW signal and the BW signal. Since the motor should be synchronized with the FW signal when the motor rotates forward, the output signal of the D0 terminal of the first decoder 65 is input as the clock signal of the counter 67 using the analog switch 73. In this case, the output signal of the D2 terminal of the first decoder 65 is input as the clock signal of the counter 67 using the analog switch 73 so as to be synchronized with the BW signal.

As described above, in the present embodiment, the analog switch 73 is used to select the forward-only signal and the reverse-only signal. However, it is also possible to configure to select using a relay, a data selector, or the like without following the present embodiment.

Next, the operation of the SRM controller shown in FIG. 6 will be briefly described.

Once the rotor is positioned at the point where the C phase inductance of the SRM is maximum for starting, it can be placed in the area where the A phase inductance increases in the forward rotation, and the D phase inductance in the increase region in the reverse rotation. Therefore, the 80196KB 50 outputs a signal to the P1.0 terminal and the P1.1 terminal, and sets the Q2 terminal of the second decoder 69 to be turned on when the counter 67 is enabled to output the signal. The terminals A and B of the counter 67 are terminals for presetting the counter 67. When the counter 67 outputs '10', the Q2 terminal of the second decoder 69 is turned on. Therefore, setting the A and B terminals of the counter 67 to '10' will start counting from '10' when the counter 67 is enabled. Next, 80196KB 50 outputs a signal to the P1.2 terminal to enable the load terminal L of the counter 67. Then, the counter 67 outputs a binary number '10', and the Q2 terminal of the second decoder 69 is turned on and coordinates with the current controller 55 to position the position of the motor rotor at a desired initial position.

When the rotor of the motor is in the initial position, the motor is started next. For forward rotation, the analog switch 73 is controlled by the P1.3 terminal output signal of 80196KB (50) to D0 of the first decoder 65. After the output signal of the terminal is selected as the clock input of the counter 67 (DIR terminal), the Q0 of the second decoder 69 is turned on by using the load terminal of the counter 67. For reverse rotation, the analog switch 73 is controlled by the P1.3 terminal output signal of 80196KB (50) to select the output signal of the D2 terminal of the first decoder 65 as the clock input of the counter 67, and then the second decoder. What is necessary is just to make Q3 of (69) turn on.

80196KB (50) checks the upper 4 bits (P0.4 ~ P0.7) of Port0 to verify that the switching sequence at startup and operation is correct. Check the upper 4 bits (P0.4 ~ P0.7) and if the switching sequence is not correct, set the A and B terminals of the counter 67 properly through Port0 (P1.0, P1.1), and set the counter (67). ) Is enabled to forcibly control the output of the second decoder 69 to a desired state to change the phase switch state of the inverter 80.

On the other hand, 80196KB (50) receives the FW, BW phase of the encoder to the HSI pin. 80196KB (50) detects the phases of the encoder's FW and BW to determine whether the motor is rotating forward or reverse by internal program (θestimation), and the speed is 80196KB (50) Timer2 (T2CLK, T2UPDN). It calculates by M / T method which is a speed calculation method by the existing encoder.

After the description of the SRM driving encoder device and the SRM controller proposed in the present invention, the results of the SRM driving experiment performed using the SRM driving encoder device and the SRM controller proposed in the present invention will be described with reference to the drawings.

When the SRM rotates clockwise in the forward direction and the counterclockwise rotation in the reverse direction, Fig. 11 (a) shows the photos of the encoder's FW and BW when the SRM rotates forward at 6000 rpm. The output signals 1 and 3 of the coupler and the signals 2 and 4 after passing this signal through the comparator are shown. The comparator is a comparator that is not shown in the drawing, and is a comparator built in the encoder together with a photo coupler in order to improve the waveform of the output signal of the photo coupler. In general, since the comparator is used to improve the waveform of the output signal of the photocoupler, the description of the comparator will be omitted.

At this time, the forward / reverse rotation of the motor is determined based on the phase angle difference between the FW and BW output signals 2 and 4 of the comparator, and the gate signal is sequentially applied to each phase for each rising edge of each pulse of the FW or BW. As shown in Fig. 11A, a phase delay occurs to some extent between the output signals 1 and 3 of the photocoupler and the output signals 2 and 4 of the comparator. However, this phase delay is not a phase delay over time but a phase delay over a position. Therefore, this phase delay angle is always constant regardless of the speed of the motor, so if the position of the photocoupler is compensated by this angle, it can be switched at the desired position.

The gate signals 1 to 4 of each motor phase are shown in Fig. 11B, and the B to D phase signals 2, 3 and 4 shift the A phase signal 1 by 15 degrees. Fig. 11C shows the gate signal 1 and current 2 on the A phase. As shown in Fig. 11 (c), since the phase switch can be turned on and off at a constant rotor position angle even at a high speed, the phase current 2 has almost the same shape, and it is possible to control the speed and torque very stably. It is showing. Accurate and stable phase switch ON and OFF are very helpful for the system stability under normal conditions.

12 is an experimental result waveform when the SRM rotates forward at 1800 [rpm]. Fig. 12 (a) shows the FW output signal 1 and the A to C phase signals 2 to 4 of the encoder at the forward rotation. Fig. 12 (b) shows the BW (1) and FW signals (2) and FW signals. The A-phase signal 3 obtained from the above and the A-phase current 4 at that time are shown. 12 (c) shows currents A to D of the currents 1 to 4 at that time. As shown in Fig. 12 (c), it can be seen that all phase currents 1 to 4 always have the same shape every cycle by turning the phase switch ON and OFF at a constant rotor position angle.

FIG. 13 is an experimental result waveform for comparing phase switching stability in the conventional microprocessor method and the proposed method when the SRM rotates forward at 1800 rpm. 13 (a) is a conventional switching method using a microprocessor as shown in FIG. 2, the degree of control of the ON and OFF angles of the phase switch is reduced so that the phase current waveform cannot be uniform. As a result, it is considered that there is considerable pulsation in phase torque. On the other hand, in Fig. 13 (b) which is the proposed phase switching method, the ON and OFF angles are always controlled at a constant position, so that the phase current waveform is maintained in a constant shape. On the other hand, it must be mentioned here that the speed of the motor is 6,000 rpm. The driving test results by the proposed method at this speed are already shown as current waveforms in FIG. 11, but the driving results are very unstable in the case of the conventional microprocessor method, and thus the experimental results could not be obtained.

Fig. 14 shows the speed 4 and the phase current waveform 3 when starting by the variable voltage method in a state where the speed command value is set to 1800 rpm to investigate the starting characteristic of the proposed method. As shown in Fig. 14, it can be seen that the steady state is about 90 ms after starting.

Fig. 15 shows by experiment that the speed and torque of the motor can be controlled by the current control method under the rated speed. 15 (a) and 15 (b) show the respective phase current waveforms when the load torques are 1 Nm and 2 Nm, respectively, and it can be seen that the speed becomes constant even if the load changes. It can also be seen that.

As described above, in the present invention, a low-cost encoder suitable for SRM driving is proposed, and an SRM driving process for outputting the output signal of the proposed encoder into a phase switch gate signal of an SRM driving inverter by a digital logic circuit using a decoder and a counter, etc. We proposed an encoder device. When the SRM controller is designed using the proposed SRM drive encoder device, the switch ON and OFF angle delays are always constant regardless of the operation speed of the SRM. Therefore, if the compensation is properly compensated, the ON / OFF switching can always be performed at the correct position. The advantage is that not only stable operation is possible in the speed range, but also forward and reverse operation are possible.

In addition, the SRM controller does not require a high-speed microprocessor, and since the low-cost encoder is used, there is an advantage that stabilization and low cost of the SRM drive system can be realized. Therefore, the possibility of practical use of SRM is further enhanced.

Claims (5)

In the optical encoder, A disc configured to rotate in engagement with a rotating shaft of the electric motor; A first pattern (FW) formed on the disc to output pulses having the same period as the on time of the gate signal of the switching element constituting the SRM drive inverter when the disc rotates; A second pattern (BW) having an appropriate phase difference with the first pattern and formed inside the first pattern to form the same gate signal during forward / reverse operation of the SRM with reference to the inductance profile of the SRM; Output signals (FW, BW signals) generated by the first pattern and the second pattern in accordance with the rotation is processed into a gate signal having the same number as the number of phase of the SRM, so that the gate signal is driven SRM And a logic circuit configured to sequentially turn on an inverter switching element to drive the SRM. The logic circuit of claim 1, wherein the logic circuit comprises: From the logical relationship between the FW signal and the BW signal, a clock signal for exclusive use for extracting a synchronization signal having the same period as the FW signal and available for forward rotation of the SRM; A clock extraction circuit having the same period as the BW signal and extracting a reverse rotation clock signal that can be used as a synchronization signal suitable for reverse rotation of the SRM; And an sequential circuit for processing a gate signal for sequentially turning on the switching element of the inverter in synchronization with the output signal of the clock extraction circuit. The method of claim 2, wherein the sequential circuit, A counter for counting the output of the clock extraction circuit as a clock input signal; And a decoder which decodes the output of the counter and converts the output of the counter into consecutive sequential signals equal to the number on the SRM. The method of claim 2, wherein the clock extraction circuit, A decoder for decoding a logical relationship between the FW signal and the BW signal; And a selection circuit for selecting a forward-only signal and a reverse-only signal among the outputs of the decoder. The encoder driving apparatus of claim 4, wherein the selection circuit uses an analog switch.