1. Field of the Invention
The present invention relates to a brushless motor driving device, a brushless motor starting method, and a method of detecting the rotor stop position of a brushless motor.
Priority is claimed on Japanese Patent Application No. 2006-206390, filed Jul. 28, 2006, Japanese Patent Application No. 2006-242647, filed Sep. 7, 2006, and Japanese Patent Application No. 2007-000469, filed Jan. 5, 2007, the content of which is incorporated herein by reference.
2. Description of Related Art
In a brushless motor of the type in which the rotor has a permanent magnet, position sensorless drive control may be performed in which position sensors that detect the rotational position of the rotor are not provided. In this case, the rotational position of the rotor is detected from the edge gap of a pulse signal obtained by inputting an induced voltage that appears at the motor terminals of an open section (non-energized phase) and an equivalent neutral-point potential to a comparator. However, when the rotational frequency is zero or the rotational frequency is extremely low, such as during startup of a brushless motor, since the induced voltage is not generated or is extremely small, a signal sufficient for detection of the rotational position is not acquired.
A conventional method for detecting the stop position of a rotor includes detecting the voltage impressed on coils of three phases and detecting the inductances of the coils from the differences in voltage rise times to determine the coils facing magnetic poles of permanent magnets (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2004-40943). In the event of the flux direction of the coil and the flux direction of the magnet core not coinciding, when a current is flowed, the impedance changes before and after the flow of the current due to residual magnetization of the magnet core. Therefore, in the driving device that is disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-40943, a current is flowed in succession two times or more in the same phase and the coil with the smallest voltage rise time in the second time onward is detected.
As another method of detecting the rotor stop position, three-phase conduction is performed by simultaneously flowing short pulse currents, a degree of which does not rotate the rotor, from one coil to the two other coils. By measuring the pulse width of square-wave pulse voltages that are simultaneously generated in the two coils when the current is turned OFF, the rotor stop position is determined (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2002-335691). Since the pulse widths of the two square-wave pulse voltages that are simultaneously generated in the two coils subtly change in accordance with differences in the rotor stop position, the rotor stop position is specified by comparing both.
Also, as a conventional method of starting a brushless motor, open loop forced energization is performed that forcibly switches the energization without detecting the rotor position, and when the rotor position can be detected, the energization switching is controlled based on the aforementioned pulse signal (for example, refer to Japanese Unexamined Utility Model Application, First Publication No. H06-25224).
In addition, there is also a method of starting a brushless motor which includes putting the rotor position in a locked state by attracting the rotor position to a specific position by applying a first energizing pattern that positions the rotor at a specific position, applying a second energizing pattern that leads the first energizing pattern by 60° for a minimal time, and then applying a third energizing pattern that leads the second energizing pattern by a further 60° (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2001-211684).
Here, as a starting method in the case of the brushless motor rotating in reverse by an external load, there is the method disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-128485. First, after reducing the rotational frequency of the rotor by three-phase energization, the energization during the three-phase energization is repeatedly turned ON/OFF, and the phase difference and the position at which the phase current becomes zero are investigated. The rotational direction is determined from the phase difference of the currents, and in the case of being determined to be in a reverse rotational state, the reverse rotational frequency is found from a generation cycle of zero point at each phase. After an AC current with a reverse rotational frequency is supplied and brought in, the frequency is slowly changed from a reverse direction to a frequency in a forward direction, whereby the motor can be started by raising the rotational frequency of the rotor to a desired rotational frequency.
However, when detecting the stop position of a rotor, in the method as disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-40943, it is necessary to add transistors, resistors, and comparators and the like that constitute a stop position detecting circuit that detects the rotor stop position, thus becoming a factor in complicating the device constitution. Also, as the difference between voltage rise times is small, the inductance difference becomes minute, thereby hindering an accurate determination.
The method disclosed in Japanese Unexamined Patent Application, First Publication No. 2002-335691 has the advantage of eliminating special-purpose circuits, but since the difference between inductances due to the impressed voltage in the three-phase energization is small, the difference between pulse widths of square-wave pulse voltages becomes small, thereby hindering an accurate detection.
Also, among conventional methods of starting a brushless motor, in the case of open loop forced energization being performed, its susceptibility to disturbances causes a high parameter dependency of the brushless motor, which makes the setting of the parameters difficult. Also, continuing forced energization slowly causes the rotor to start to rotate. As a result, the time required for starting the motor becomes longer, and the torque during starting diminishes. Performing forced energization switching many times further increases the susceptibility to disturbances.
In the case of the rotor being put in a locked state by a predetermined energization pattern, and also in the case of measuring inductance, since it is necessary to perform open loop forced energization during the period the brushless motor starts to rotate until the rotor position can be detected, the same issues are involved. Moreover, in the case of putting the rotor in a locked state, in a motor with large inertia, a long time is required for positioning the rotor.
In the case of starting from a reverse rotational state, since the rotational direction and the frequency of rotation are calculated after finding the position at which the phase current becomes zero, complicated processing is required. Also, by slowly changing the frequency from a reverse rotational direction to a frequency in a forward direction, a long time is required until starting.
The present invention was achieved in view of the above circumstances, and has as its main object to start a motor in a short time by a simple method and also to enable high torque to be obtained during starting.
The invention according to a first aspect of the present invention that solves the aforementioned problem is a driving device that drives a brushless motor, the device includes an energization pattern determining device that, during start-up of the brushless motor, applies to the brushless motor an excitation pattern according to a stop position of a rotor of the brushless motor for an initial energization time and then stops the energization to cause the rotor of the brushless motor to coast; and an excitation switch timing calculating device that determines an excitation timing by detecting the rotor position from an induced voltage that is generated at the motor terminals during coasting of the rotor.
In this driving device for a brushless motor, in order to be able to correctly detect the rotational position of the rotor when starting, it is accelerated and then allowed to coast to detect the rotor position from an induced voltage that is generated during the coasting. Since the induced voltage at this time is in a state of not being influenced by pulse width modulation signals and the like, the rotor position is correctly detected. After detecting the rotor position, ordinary energization switching is performed.
A second aspect of the present invention is the driving device for a brushless motor according to a first aspect of the present invention, in which the initial energization time being of a length that is not longer than the time until a first energization switch timing after the rotor starts rotation.
In this driving device for a brushless motor, acceleration is performed within a range in which the rotor is attracted to the stator and reverse torque does not occur. Therefore, the rotor can be coasted with sufficient rotational speed for rotor position detection.
A third aspect of the present invention is the driving device for a brushless motor according to a first or second aspect of the present invention, in which the excitation switch timing calculating device calculates the excitation timing from a time interval between the second and subsequent induced voltage signals generated at the motor terminals during coasting of the rotor.
In this driving device for a brushless motor, the signal that is generated at the first time during coasting may be a square-wave pulse voltage due to energy that is stored in the coil. Therefore, skipping this signal and using the second and subsequent signals improves the detection accuracy.
A fourth aspect of the present invention is the driving device for a brushless motor according to any one of aspects 1 to 3 of the present invention, which further includes an excitation voltage output device that selects a plurality of excitation patterns that are capable of driving the brushless motor and applies each excitation pattern in turn within a time range in which the rotor does not rotate; a square-wave pulse voltage width detecting device that detects the pulse widths of a square-wave pulse voltage generated in a coil of the brushless motor when switching excitation patterns; and a rotor position estimating device that finds the minimum value or the maximum value from the pulse widths of square-wave pulse voltages in the plurality of excitation patterns and determines the stop position of the rotor from the excitation pattern of the minimum value or maximum value; in which an energization pattern that leads or lags by a predetermined electrical angle from the stop position of the rotor determined by the rotor position estimating device is output as a start-up excitation pattern.
This driving device for a brushless motor investigates the pulse widths of square-wave pulse voltages that are generated when switching excitation patterns for a plurality of types of excitation patterns, with the stop position of the rotor being specified by the maximum value or the minimum value thereof. Since the excitation pattern for starting that is in accordance with the rotor stop position is defined in advance, the driving device starts the brushless motor with that excitation pattern.
A fifth aspect of the present invention is the driving device for a brushless motor according to a fourth aspect of the present invention, in which the excitation voltage output device performs an excitation pattern that does not energize a coil between an excitation pattern that N pole magnetizes the coil and an excitation pattern that S pole magnetizes the same coil.
In this driving device for a brushless motor, after a coil of one phase is N pole magnetized, it is put in a non-energized state before being S pole magnetized and therefore residual magnetization of the coil is released. Since the coil enters a non-energized state also when changing from S-pole magnetization to N-pole magnetization, residual magnetization of the coil is released.
A sixth aspect of the invention is the driving device for a brushless motor according to fourth or fifth aspects of the present invention, in which an excitation pattern having a phase lag of 120 degrees during forward rotation and outputting an excitation pattern having a phase lead of 120 degrees during reverse rotation, when the rotor position estimating device has determined the stop position of the rotor from the minimum value of the pulse widths of the square-wave pulse voltages.
When this driving device for a brushless motor selects an excitation pattern with a phase difference of 120 degrees with respect to the rotor stop position, sufficient torque for starting rotation of the rotor is obtained, and a rotational characteristic is obtained in which the torque increases just after rotation. For this reason, the rotor can be started in a stable manner, and a large acceleration can be obtained.
A seventh aspect of the present invention is the driving device for a brushless motor according to any one of first to sixth aspects of the present invention, which further includes a voltage dividing circuit that divides square-wave pulse voltages generated at the coils and inputs them to the square-wave pulse voltage width detecting device.
In this driving device for a brushless motor, when a square-wave pulse voltage is high, by changing it to a desired voltage level with the voltage dividing, circuit signal processing becomes possible.
An eighth aspect of the invention is the driving device for a brushless motor according to any one of fourth to seventh aspects of the present invention, in which, when the rotor is rotating in reverse, impressing a low duty ratio voltage and running the excitation voltage output device after applying a brake to the rotor.
This driving device for a brushless motor detects the rotor stop position after putting the rotor in a stopped state or nearly stopped state by applying the brake to the rotor during reverse rotation. In accordance with the detected rotor stop position, starting process is performed.
A ninth aspect of the invention is the driving device for a brushless motor according to eighth aspect of the present invention, which further includes a filter that removes noise that is included in the detection signal of the terminal voltage in a device that detects the terminal voltage of each phase of the brushless motor and a filter delay phase correction device that corrects the delay phase of the filter that changes in accordance with the rotational speed of the brushless motor in the excitation switch timing calculating device.
This driving device for a brushless motor corrects the excitation pattern switching timing in consideration of the phase delay due to the filter, and enables phase switching with an appropriate timing.
A tenth aspect of the invention is the driving device for a brushless motor according to ninth aspect of the present invention, in which the filter is a primary CR filter that removes noise that is generated when performing pulse width modulation control of the brushless motor.
This driving device for a brushless motor has a characteristic of removing high frequency component noise in the pulse width modulation control, and so a phase delay easily occurs when the rotational speed of the brushless motor is high. The filter delay phase correction device corrects such a phase delay.
A eleventh aspect of the invention is the driving device for a brushless motor according to tenth aspect of the present invention, in which the excitation switch timing calculating device further includes a circuit delay phase correction device that corrects the delay phase due to circuits other than the filter.
This driving device for a brushless motor has a function of correcting the delay phase that is characteristic to a device that is independent of rotational speed.
A twelfth aspect of the invention is a method of starting a brushless motor, the method comprising: energizing the brushless motor with an excitation pattern according to a stop position of a rotor of the brushless motor for an initial energization time and then stopping the energization to cause the rotor of the brushless motor to coast; detecting the rotor position from an induced voltage that is generated at the motor terminals during coasting of the rotor; and performing switching of the excitation pattern based on the detected rotor position.
In this method of starting a brushless motor, when the rotor starts rotation, the energization is stopped to cause the rotor to coast. The position of the rotor during rotation is detected from the induced voltage generated at this time. Thereafter, drive controlling of the brushless motor is performed by carrying out ordinary energization switching based on the position of the detected rotor.
A thirteenth aspect of the invention is the method of starting a brush motor according to twelfth aspect of the present invention, in which the initial energization time is of a length that is not longer than the time until a first energization switching timing after the rotor starts rotation, and the step of detecting the rotor position is performed until the induced voltage, which is generated at the motor terminals when rotating the rotor, is generated fourth time.
In this method of starting a brushless motor, during start-up the rotor is made to coast after being accelerated until a time corresponding to the first energization switching timing, and the rotor position is detected until the time corresponding to the fourth energization switching timing.
A fourteenth aspect of the invention is a method of detecting a stop position of a rotor of a brushless motor, which includes selecting a plurality of excitation patterns that are capable of driving the brushless motor; selecting an energization sequence so that an excitation pattern that does not energize a coil of the brushless motor is applied between an excitation pattern that N pole magnetizes the coil and an excitation pattern that S pole magnetizes the same coil; energizing with each excitation pattern in turn within a time range in which the rotor does not rotate; and determining the stop position of the rotor from the minimum value of pulse widths of square-wave pulse voltages generated in the coil of the brushless motor when switching the excitation pattern.
In this method of detecting a stop position of a brushless motor, after a coil of one phase is N pole magnetized, it is put in a non-energized state before being S pole magnetized, and therefore residual magnetization of the coil is released. Since the coil enters a non-energized state when changing from S pole magnetization to N pole magnetization, residual magnetization of the coil is released and detection accuracy of the rotor stop position is improved.
A fifteenth aspect of the invention is a method of starting a brushless motor, which includes, when starting up a brushless motor, selecting a plurality of excitation patterns that are capable of driving the brushless motor; energizing with each excitation pattern in turn within a time range in which the rotor does not rotate; investigating the pulse width of a square-wave pulse voltage that is generated in a coil of the brushless motor when switching the excitation pattern; determining the stop position of the rotor from the minimum value thereof; outputting an excitation pattern having a phase lag of 120 degrees from the rotor stop position during forward rotation; and outputting an excitation pattern having a phase lead of 120 degrees from the rotor stop position during reverse rotation.
In this method of starting a brushless motor, by selecting an excitation pattern with a phase difference of 120 degrees with respect to the rotor stop position, sufficient torque for starting rotation of the rotor is obtained, and it is possible to increase the torque just after rotation. Therefore, a brushless motor can be reliably started.
A sixteenth aspect of the invention is a method of starting a brushless motor, which includes: detecting the stop position of a rotor of the brushless motor by utilizing the inductance of a coil; stopping energization all the phases after outputting an excitation pattern with a phase lag of 120 degrees from the stop position of the rotor for a prescribed time; performing energization control based on a detected rotor position when rotor position detection by induced voltage is possible in the state of having stopped energization to all phases; and energizing with an excitation pattern so as to stop rotation of the rotor when rotor position detection by induced voltage is impossible in the state of energization of all phases being stopped; in which a step of detecting the rotor stop position by utilizing the inductance of the coil after energizing with an excitation pattern for a predetermined time so as to stop rotation of the rotor is performed.
In this method of starting a brushless motor, when performing start-up control so as to cause the brushless motor to rotate forward, if the rotor position can be detected, the processing proceeds to ordinary rotational control. In contrast, when the rotor position cannot be detected, the rotor is determined to be rotating in reverse, a brake is applied to the rotor, and the start-up control is performed again.
In accordance with the present invention, it is possible to detect induced voltage generated at the motor terminals without being influenced by pulse width modulation signals or the like by making a coasting state during starting. Because of this, it is possible to accurately detect rotor position without being influenced by disturbances. Also, because rotor position is detected during the coasting, it is possible to detect rotor position in a short time and to shift to ordinary operation.
In the case of brushless motor being determined not to be in forward rotation during starting, by performing starting process again after performing energization control so as to stop rotor, it is possible to start quickly to forward rotational direction even from reverse rotational direction state. In this way, it is possible to eliminate complicated processing to determine reverse rotational direction.
The best modes for carrying out the invention shall be described in detail with reference to the drawings. Note that the same reference numbers are used to denote the same constituent elements in the embodiments. Also, overlapping explanations in the embodiments shall be omitted.
As shown in
The brushless motor 1 has a rotor that has permanent magnet and a stator. In the stator, coils of three phases (U, V, W) are wound in that order in the circumferential direction. This brushless motor system is a sensor-less type system that does not have a sensor that detects the rotor position.
The driving device 2 has a control unit 11 which is formed of microcomputers and the like, an induced voltage I/F (interface) circuit 12 that detects the voltage that is impressed on the current-carrying wires that form the coils of three phases of the brushless motor 1, an inverter 13, and a voltage dividing circuit 14 that is a level conversion circuit that converts the level of the voltage that is impressed on the current-carrying wires of the brushless motor 1, in which pre-drivers 37A and 37B, an overcurrent sensing circuit 38, and an overcurrent protection device 39 are provided between the control unit 11 and the inverter 13.
As shown in
Here, the circuit 16 that detects the equivalent neutral-point potential adopts a two-phase comparison method that, for example, detects the equivalent neutral-point potential from the motor terminal voltages of V-phase and W-phase for the U phase. By doing so, an approximately flat voltage is obtained as the equivalent neutral-point potential. It is also acceptable to use a three-phase comparison method that finds the equivalent neutral-point potential by using the signals of all three of the U, V, and W phases.
In this case, the equivalent neutral-point potential is an approximate triangular wave that is centered at ½ of the source voltage.
The comparators 17A to 17C generate pulse signals that output a low-level signal when the analog signal of the induced voltage is higher than the equivalent neutral-point potential and output a high-level signal when the analog signal of the induced voltage is lower than the equivalent neutral-point potential. In each comparator 17A to 17C, a pulse signal with an angular resolution of 120 degrees electrical angle is created. These signals are input to a composite signal formation circuit 19 through the low-pass filter circuits 18A to 18C.
The inverter 13 is a circuit that is formed by bridge connecting each two of six switching elements between the positive-negative terminals of a power supply 20. The inverter 13 converts the DC voltage that is supplied from the power supply 20 to an AC voltage based on the pulse width modulation signal (driving signal) that is input from the control unit 11 and impresses it on each phase of the brushless motor 1. Note that a shunt resistor 13A is provided between the inverter 13 and the ground level. The current that flows to the inverter 13 using the shunt resistor 13A, that is, the current that is input to the brushless motor 1, can be detected using the overcurrent sensing circuit 38.
The voltage dividing circuit 14 is a circuit that divides the terminal voltage (e.g., 12V or 36V and the like) generated in each of the current-carrying wires of the brushless motor 1 by two resistors into a voltage level that can be used by the control unit 11 (e.g., 3V or 5V and the like).
The control unit 11 has a separating device 21 that is connected to the induced voltage I/F circuit 12; an excitation switch timing calculating device 22; a rotational direction determining device 23; a rotational direction detection logic selection device 24; a brake stopping device 25; an energization pattern determining device 26; an excitation voltage output device 27; and a PWM duty ratio determining device 28. Also, the control unit 11 has a square-wave pulse voltage width detecting device 29 that is connected to the voltage dividing circuit 14 and is used during starting; a square-wave pulse voltage width comparing device 30; and a rotor position estimating device 31. Moreover, it has an overcurrent protection device 32 that is connected to the overcurrent sensing circuit 38.
The separating device 21 performs a processing to separate the edge of the pulse signal that is input from the induced voltage I/F circuit 12 into the edge of the induced voltage and the edge of the square-wave pulse voltage. The excitation switch timing calculating device 22 generates one pulse signal with an angular resolution of 60 degrees electrical angle from the three pulse signals with an angular resolution of 120 degrees electrical angle to compute the excitation phase in accordance with the induced voltage edge and calculates the excitation switch timing. A delay phase correction portion 22A that corrects the excitation switch timing is provided in the excitation switch timing calculating device 22.
The rotational direction determining device 23 determines the rotational direction from the excitation switch timing, and outputs a predetermined instruction to the rotational direction detection logic selection device 24 and to the brake stopping device 25. The rotational direction detection logic selection device 24 is used in the case where the logic that the separating device 21 uses depending on the rotational direction of the brushless motor 1 is selectable. The brake stopping device 25 is used when energizing an energizing pattern so as to stop the brushless motor 1.
The energization pattern determining device 26 has a steady-state excitation device 33, a stop position detection device 34, a coasting control device 35, and a start-up excitation device 36. The steady-state excitation device 33 decides an excitation pattern in accordance with the rotor position with the excitation switch timing that is calculated by the excitation switch timing calculating device 22. The stop position detection device 34 receives a start instruction from outside and generates a pulse width modulation signal for detecting the rotor stop position to an excitation voltage output device 27. The start-up excitation device 36 decides an excitation pattern in accordance with the rotor stop position corresponding to the square-wave pulse voltage width that is decided to be a minimum by the rotor position estimating device 31. The coasting control device 35 performs a process that applies the start-up excitation pattern for a predetermined initial energization time Ts1 and then allows the brushless motor 1 to coast to detect the rotor position. These processes are explained in detail later.
The excitation voltage output device 27 outputs a signal to impress an excitation current on the coil of the brushless motor 1 to each of the pre-drivers 37A and 36B. The hi-side pre-driver 37A is a driver that performs ON/OFF switching of the switching elements on the high-potential side by the duty ratio that is decided by the PWM duty ratio determining device 28. The lo-side pre-driver 37B is a driver that performs ON/OFF switching of the switching elements on the low-potential side. The hi-side pre-driver 37A has a function that turns off each switching element when a signal is input from the overcurrent protection device 39 at the time of an overflow current flowing to the inverter 13. Also, when an overflow current is detected, a signal is input to the overcurrent protection device 32 and a software reset is applied.
The square-wave pulse voltage width detecting device 29 performs a processing to detect a square-wave pulse voltage width from the signal that is input from the voltage dividing circuit 14. The square-wave pulse voltage width detecting device 29 has a storage device 29A such as a memory, and can store data of the detected square-wave pulse voltage width in association with the excitation pattern at that time. The square-wave pulse voltage width comparing device 30 compares the data of a plurality of detected square-wave pulse voltage widths stored in the storage device 29A of the square-wave pulse voltage width detecting device 29 and determines the one that is a minimum. The rotor position estimating device 31 estimates the rotor position during standstill and during low speed based on the comparison result of the square-wave pulse voltage widths.
Next, the operation of the driving device 2 shall be described.
When starting the brushless motor 1, there are cases where the brushless motor 1 is standstill and cases where the brushless motor 1 is being made to rotate by an external load. Moreover, in the case of the brushless motor 1 being made to rotate, there are cases where it is rotating in forward direction and cases where it is rotating in reverse direction. For example, in the case of using the brushless motor 1 for a rotating mechanism of a radiator fan, when wind blows from the radiator to the direction of the engine room, the brushless motor 1 is made to rotate in forward in accordance with the rotation of the radiator fan even if energization is not performed. In contrast, it is conceivable for the brushless motor 1 to rotate in reverse when wind is blowing from the engine side in the direction of the radiator or when a negative pressure occurs in the reverse direction with respect to the radiator fan.
In the case of assuming the driving device 2 to be used for the radiator fan, the radiator fan has a structure that allows it to readily rotate in the forward direction, with a strong wind force needed in order to make it rotate in the reverse direction. However, there is a low possibility of a large wind force occurring in the reverse direction due to the configuration of the vehicle, and even if the radiator fan rotates in reverse, the rotational speed would conceivably be low. Accordingly, in the driving device 2, even if the brushless motor 1 rotates in reverse by an external load, control during starting is performed assuming the rotational frequency and the torque are small.
Also, in the region R3 smaller than R1, that is, where the rotational speed in the reverse rotational direction is large, rotor position detection is performed after applying a brake to the brushless motor 1 as described below. The region R1 and the region R3 overlap near the rotational speed −N1 (rpm).
Here, the region R1 and the region R2 may be divided at the rotational speed N1 without overlapping, and the region R1 and the region R3 may be divided at the rotational speed −N1 without overlapping.
The driving device 2 initially performs a processing assuming that the rotational speed of the brushless motor 1 is in the region R1, and shifts to steady driving via processing equivalent to the region R2. In the case that rotor position detection cannot be performed when performing the processing corresponding to the region R2, the brushless motor 1 is regarded as being in region R3, and the position detection is performed again from the processing corresponding to the region R3. An illustrative example of this starting method is explained referring to the flowchart in
When a start-up initiation instruction is input to the stop position detection device 34, overflow current detection is performed (step S101). The overcurrent is monitored by a current value that flows through the shunt resistor 13A of the inverter 13. When the current that flows through the shunt resistor 13A exceeds a predetermined value, the current is judged as being an overcurrent, that is, an overload state (“Yes” in step S101), and a stop process is carried out by turning off all phases (step S102) to end the process. When an overcurrent is not detected (“No” in step S101), a process to detect the rotor position by inductance detection is carried out (step S103). Checking for an overcurrent is constantly performed by a separate program that runs in parallel, so that if an overcurrent is detected while executing a process from step S103 onward, the process is stopped at that point.
When the rotor stop position is detected by inductance detection, the start-up excitation device 36 decides the start-up excitation pattern with the phase that is capable of generating the maximum torque with respect to that rotor position, and the excitation voltage output device 27 outputs a start-up excitation pattern (step S104). An initial energization counter is activated, and the aforementioned phase is energized until the constant initial energization time Ts1 set in advance elapses (step S105). When the initial energization time Ts1 elapses (“Yes” in step S105), the coasting control device 35 allows the rotor to coast by turning off energization to all phases (step S106). Position detection of a rotor 41 is performed using forward rotation specific logic from the induced voltage that is generated while the rotor 41 is coasting by inertia (step S107). When the rotor position can be detected a predetermined number of times (“Yes” in step S108), the processing proceeds to sensorless driving (steady driving mode) by induced voltage using the steady-state excitation device 33 (step S1109).
When the rotor position cannot be detected the predetermined number of times (“No” in step S1108), the processing waits until the counter that measures the edge intervals of the induced voltage overflows the predetermined number of times (step S110). When the counter overflows the predetermined number of times (“Yes” in step S110), the rotational direction determining device 23 judges the brushless motor 1 to be rotating in reverse. As a result, two-phase energization lock processing is performed with a low duty ratio as brake process by the brake stopping device 25 (step S111). The brake process is performed for a prescribed time defined in advance, and when this time elapses (step S112), the processing returns to step S101.
From step S103 to step S105, the initial rotational speed is in the range of the region R1, are the processes to accelerate to region R2 from region R1.
Step S103 shall be explained in detail. Here, the stop position is decided focusing on the fact that when the direction of the magnetic flux produced by the coil and the direction of magnetic flux of the magnet are in the same direction, the magnetic permeability of the magnet cores increases and the inductance decreases.
When starting the brushless motor 1 in a stopped state, a start-up instruction is input from outside to the stop position detection device 34 of the control unit 11. The stop position detection device 34 outputs an instruction to the excitation voltage output device 27 so that six predetermined excitation patterns for stop position determination are continued for a period during which the rotor does not rotate. The period during which the rotor does not rotate differs depending on the inertia of the brushless motor 1, but, for example, is a period from several microseconds to several milliseconds, and is counted by a counter provided in the control unit 11. The excitation voltage output device 27 outputs the pulse width modulation signal in accordance with the excitation pattern to the inverter 13. In accordance with the pulse width modulation signal, the switching elements are switched ON or OFF so that any two of the three phases are energized.
Here,
In the excitation pattern No. 1, a current flows from the U-phase coil (hereinafter referred to as the U phase) to the V-phase coil (hereinafter referred to as the V phase). The U phase is N pole magnetized, and the V phase is S pole magnetized. When the arrangement of the U, V, and W phases and the stop position of the rotor 41 are in the arrangement that is illustrated, magnetic flux is formed from the U phase, passing through the S-pole and the N-pole of the permanent magnet 42 of the rotor 41 in this order, to the V phase as shown by the arrow.
In the excitation pattern No. 2, a current flows from the U phase to the W phase. The U phase is N pole magnetized, and the W phase is S pole magnetized. Magnetic flux is formed from the U phase, passing through the S-pole and the N-pole of the permanent magnet of the rotor 41 in this order, to the W phase as shown by the arrow.
In the excitation pattern No. 3, a current flows from the V phase to the W phase. The V phase is N pole magnetized, and the W phase is S pole magnetized. Magnetic flux is formed from the V phase, passing through the S-pole and the N-pole of the permanent magnet of the rotor 41 in this order, to the W phase as shown by the arrow.
In the excitation pattern No. 4, a current flows from the V phase to the U phase. The V phase is N pole magnetized, and the U phase is S pole magnetized. Magnetic flux is formed from the V phase, passing through the S-pole and the N-pole of the permanent magnet of the rotor 41 in that order, to the U phase as shown by the arrow.
In the excitation pattern No. 5, a current flows from the W phase to the U phase. The W phase is N pole magnetized, and the U phase is S pole magnetized. Magnetic flux is formed from the W phase, passing through the S-pole and the N-pole of the permanent magnet of the rotor 41 in this order, to the U phase as shown by the arrow.
In the excitation pattern No. 6, a current flows from the W phase to the V phase. The W phase is N pole magnetized, and the V phase is S pole magnetized. Magnetic flux is formed from the W phase, passing through the S-pole and the N-pole of the permanent magnet of the rotor 41 in this order, to the V phase as shown by the arrow.
As shown in
In step 0, the energization pattern No. 1 is selected, which energizes with the duty ratio of the pulse width modulation signal set to 100%. The remaining W phase is opened. In step 1, by setting the duty ratio to 0% none of the phases are energized. In transition to step 1 after step 0 is complete, the moment the switching elements of the inverter 13 turn off, the electrical energy that is stored in the coil flows as current via a free wheel diode of the switching elements. A square-wave pulse voltage is generated at the V-phase terminals at this time. The terminal voltage, as a square-wave pulse voltage, is introduced into the voltage dividing circuit 14 to be divided, and then is input to the square-wave pulse voltage width detecting device 29. The square-wave pulse voltage width detecting device 29 checks the count value when it detects the falling edge of a pulse. Since the count value corresponds to the elapsed time from the switching timing of the step, this count value is stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 1 (UV energization).
In step 1, together with executing the process of the square-wave pulse voltage width detecting device 29 and the like, the counter is counted up. When the count value becomes a predetermined value as same as step 0, the counter is reset and the processing proceeds from step 1 to step 2. In step 2, the excitation pattern No. 2 is used, and the pulse width modulation signal duty ratio is set to 100%. The remaining V phase is opened. In step 3, by setting the duty ratio to 0% none of the phases are energized. The count value is checked when the edge of the square-wave pulse voltage generated in the W phase falls and stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 2 (UW energization).
In step 4, the U phase is opened by energizing with the excitation pattern No. 3. In step 5, without energizing any of the phases, the pulse width of the square-wave pulse voltage generated in the W phase is checked and stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 3 (VW energization).
In step 6, the W phase is opened by energizing with the excitation pattern No. 4. In step 7, without energizing any of the phases, the pulse width of the square-wave pulse voltage generated in the U phase is checked and stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 4 (VU energization).
In step 8, the V phase is opened by energizing with the excitation pattern No. 5. In step 9, without energizing any of the phases, the pulse width of the square-wave pulse voltage generated in the U phase is checked and stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 5 (WU energization).
In step 10, the U phase is opened by energizing with the excitation pattern No. 6. In step 11, without energizing any of the phases, the pulse width of the square-wave pulse voltage generated in the V phase is checked and stored in the storage device 29A as a square wave pulse voltage width with respect to the excitation pattern No. 6 (WV energization).
At the timing of step 12 that follows step 11, the rotor position estimating device 31 investigates the excitation pattern with the minimum value among the square wave pulse voltage widths of the excitation patterns No. 1 to No. 6 that are stored in the storage device 29A of the square-wave pulse voltage width detecting device 29, and sets the rotor position where the inductance by that excitation pattern becomes a minimum as the stop position of the rotor 41. In the example of
The process of the rotor position estimating device 31 is specifically explained in detail below. In the case of the count value of the square-wave pulse voltage width being known in advance to be 1000 or less, a value greater than 1000 is stored as an initial value in a memory that stores the minimum value to be compared with the count value of the square-wave pulse voltage width of the excitation pattern No. 1. When the count value is smaller, the data to be stored in the minimum value memory is substituted with the count value of the excitation pattern No. 1 from the initial value. The data of the minimum value memory is thus compared in turn with the count values of all of the square-wave pulse voltage widths, with the count value which is smaller, stored in the minimum value memory. The count value that is finally stored becomes the minimum value, and the excitation pattern at that time becomes the excitation pattern in which the square-wave pulse voltage width becomes a minimum.
The step S104 shall be explained in detail. The start-up excitation device 36 selects as the excitation pattern during start-up the excitation pattern that has a 120 degree lag in the rotational direction from the excitation patterns in which the square-wave pulse voltage width becomes a minimum. This is explained in
The processes thus far are described in greater detail in
When the start-up signal is input at time t1, the rotor stop position detection process (step S103) is performed until time t2. The rotational speed during this period is zero.
When the rotor stop position is determined at time t2, as shown by the current waveform of the shunt resistor 13A, the start-up excitation device 36 energizes by continuing the start-up excitation pattern for the initial energization time Ts1 (step S104). During this time, the rotational speed of the rotor 41 slowly increases.
Here, the initial energization time Ts1 is the time during which it is possible to accelerate the rotor 41 so as to be able to allow it to coast at rotational speed N1 or greater after the energization is turned off and until the edge of the induced voltage occurs a plurality of times, for example four or more times. From this standpoint, the initial energization time Ts1 is preferably long. However, when the initial energization time Ts1 is too long, the switching position of the excitation pattern is exceeded during normal operation, thereby continuing the same excitation pattern. This leads to the generation of reverse torque, causing the rotor 41 to decelerate. Accordingly, the initial energization time Ts1 is preferably as long as possible within a range in which reverse torque does not occur. As an example of a method of determining the initial energization time Ts1, the brushless motor 1 is operated with a Hall sensor in the design stage or manufacturing stage, and the time by which the signal of the Hall sensor first changes is measured. The time that is approximately the same as this time or a shorter time can be stored in the control unit 11 as the initial energization time Ts1.
When the initial energization time Ts1 has elapsed at time t3, the coasting control device 35 turns off energization of all the phases (corresponding to step S106). The current value that is measured by the shunt resistor 13A becomes zero, and the rotor 41 coasts. Thereafter, the rotational speed gradually decreases over time. At time t3, a pulse appears at each position signal. For this reason, a first signal SL1 is generated at the excitation switch timing signal corresponding to the rising edge of the three-phase composite signal. The pulse signal at this time is generated due to the generation of square-wave pulse voltages at the motor terminal voltages of all three phases when the energy that is stored in the coil of the stator is discharged as the fly wheel pulse. In the case of ordinary driving, these square-wave pulse voltages can be ignored by the separating device 21. However, due to the logic that turns off all of the phases at time t3, an exceptional state arises that is not possible during ordinary operation, and so, without being capable of ignoring the square-wave pulse voltage, leads to an erroneous detection. For this reason, the first signal SL1 after start-up is not used for detection of the rotor position.
Moreover, because the rotor 41 coasts, induced voltage is generated at the motor terminals of the predetermined phase in accordance with the rotational position of the rotor 41. In this case, rising edges or falling edges are generated in the order of the W-phase position signal, the U-phase position signal, and the V-phase position signal. As a result, as the excitation switch timing signal, a second signal SL2 that occurs at the edge of the W phase, a third signal SL3 that occurs at the edge of the U phase, and a fourth signal SL4 that occurs at the edge of the V phase are generated. By turning all phases off, it is possible to measure the intersection of the induced voltage and the equivalent neutral point potential in the state with no unnecessary signal components such as the pulse width modulation signal that is input from the inverter 13 to the brushless motor 1. Thus it is possible to accurately measure the rotor position.
During this time, the excitation switch timing calculating device 22 measures the time interval between the second signal SL2 and the third signal SL3 to compute 60 degrees electrical angle. Moreover, it measures the time interval between the third signal SL3 and the fourth signal SL4 to compute 60 degrees electrical angle. Based on these time intervals, it computes the excitation switch timing by leading, for example, 30 degrees electrical angle from the fourth signal SL4. Then, thereafter, based on the three-phase composite signal that is produced from the comparison result between the motor terminal voltage and the equivalent neutral point potential, the excitation switch timing is determined, and by performing switching control of the energization pattern, synchronized operation of the brushless motor 1 is performed. Driving with an equivalent performance with driving by 120 degrees electrical angle rectangular wave in the case of having a Hall sensor becomes possible, whereby rotational speed is controlled.
In a brushless motor with large inertia, the fifth signal onward may be acquired to similarly calculate the excitation energization timing from the time interval. The stability and accuracy during start-up can be further improved.
Also, in a brushless motor with large inertia, the time interval between the second and third signals SL2, SL3 and the time interval between the third and fourth signals SL3, SL4 are approximately equivalent. For this reason, it is acceptable to shift to sensorless driving with only the second and third signals SL2, SL3. By doing so, it is possible to initiate steady driving in an even shorter time. Also, it is acceptable to shift to sensorless driving by acquiring only the time interval of the first signal SL1 and the second signal SL2. This is effective for a brushless motor with small inertia. In this case, a preset value is used for the initial energization time SL1, and at the point of detecting the timing of SL2, the time interval of SL1 and SL2 can be calculated and used as the rotor position signal. Therefore, it is possible to shift to sensorless driving until the second signal SL2.
Also, in a brushless motor with small inertia, the deceleration increases and the time interval of the third and fourth signals SL3 and SL4 is greater than the time interval of the second and third signals SL2 and SL3. In this case, the acceleration may be calculated from the change in the time interval, and the excitation energization timing may be computed by estimating the next time interval by using this acceleration.
Moreover, this start-up method carries out a method of starting while restricting current during motor start-up (hereinafter referred to as “soft start”). For example, as shown in
Sensorless driving by induced voltage of step S109 (steady driving mode) shall now be described in detail.
In the steady driving mode, the rotor position is detected by detecting the induced voltage of the motor terminal. However, since a square-wave switching pulse (square-wave pulse voltage) overlaps the induced voltage waveform, it is necessary to remove such noise. In this embodiment, when the edge corresponding to the rotor position signal of each phase has been detected, the rotor position signal and the square-wave pulse voltage are distinguished by performing level detection of other phases. The forward rotation specific logic that is used at this time are formed of induced voltage signal detection logic shown in Table 1 and square-wave pulse voltage ending edge determination logic shown in Table 2.
Note that the separating device 21 refers to the forward rotation specific logic by the instruction of the rotational direction detection logic selection device 24 in the case of the rotational direction determining device 23 shown in
Also,
The induced voltage waveforms Uv, Vv, Wv of the stator windings U, V, W shown in
The separating device 21 separates the edge of the square-wave pulse voltage Ps and the edge of the induced voltage generated by rotation of the rotor 41 from the pulse signals of the induced voltage signals Ud, Vd, Wd. The rotational direction determining device 23 creates the position detection signals Us, Vs, Ws that are formed of information of the induced voltage generated by rotation of the rotor 41 and delivers it to the excitation switch timing calculating device 22. The excitation switch timing calculating device 22 counts the interval Te of the edges (induced voltage edge) of the position detection signals Us, Vs, Ws shown in
Here, the excitation voltage output device 27 is provided with a mask signal generation device 27A. This mask signal generation device 27A outputs a mask signal to the separating device 21 immediately before the excitation voltage output device 27 outputs the energization pattern to the inverter.
For example, in the example of
Note that as for the electrical angle that determines the pulse width of the mask signals Um, Vm, Wm, an angle that is stored in advance is always calculated from the measured value of Te. Specifically, a value greater that 0 degree and less than 30 degrees is used that is greater than the pulse width of the square-wave pulse voltage Ps when rotated by an ordinary load and that ensures that the intersection of the induced voltage waveforms Uv, Vv, Wv and the equivalent neutral point voltage is not masked by the pulse of the mask signal.
Thereafter, with respect to the induced voltage signals Ud, Vd, Wd that are input from the induced voltage I/F circuit 12, the pulse of the square-wave pulse voltage Ps is removed by the mask signals Um, Vm, Wm to create the position detection signals Us, Vs, Ws, and energization control of the brushless motor 1 is performed.
Here, the pulse width of the square-wave pulse voltage Ps changes depending on the size of the load and the rotational speed. In contrast to this, since the mask signals Um, Vm, Wm are fixed pulse widths, cases arise in which the pulse of the square-wave pulse voltage Ps can be completely masked by the mask signals Um, Vm, Wm and cases in which it cannot be completely masked.
First, when the pulse width of the square-wave pulse voltage Ps is less than or equal to the mask width, as shown in
In
In contrast, as shown in
In
Here, the process of correcting the timing of switching the energization when generating the phase detection signals Uss, Vss, Wss shall be described. The correction is performed by the delay phase correction portion 22A provided in the excitation switch timing calculating device 22.
First, the process of the delay phase correction portion 22A as a filter delay phase correction device shall be described.
In the case that the range R4 shown in
The transfer function G(s) of the low-pass filter circuits 15A to 15C is expressed by the following equation using τ(=C×R).
G(s)=1/(τs+1) (1)
From equation (1), the delay phase θ1[rad] is written as follows.
θ1=−arctan(ωτ) (2)
Here, since the angular acceleration ω can be expressed as a function of the fundamental frequency of the motor terminal voltage corresponding to the rotational speed, equation (3) is expressed as follows.
θ1=−arctan(2πτ×f) (3)
Converting the unit to degrees and regarding it as delay gives the following.
θ1=arctan(2πτ×f)×360/2π (4)
By letting the time required for 60 degrees electrical angle of rotation be Ta, 1/f=6Ta, leading to
θ1=arctan(2πτ/6Ta)×360/2π (5)
The delay phase θ1 due to the filter circuits 15A to 15C can be calculated by equation (5). While the delay phase θ1 may be calculated each time from equation (5), in this embodiment, it is map registered in the delay phase correction portion 22A, so that the delay phase θ1 is obtained by searching by time Ta.
Next, the process of the delay phase correction portion 22A as the circuit delay phase correction device shall be described.
The delay phase θ2 is generated by other circuits other than the filter circuits 15A to 15C and software processing. This delay phase θ2 occurs as a result of the comparators 17A to 17C, the low-pass filter circuits 18A to 18C, microcomputers, and the like. The delay time T2 at this time is a fixed value that does not depend on the rotational speed. Accordingly, it is possible to calculate the delay phase θ2 from the ratio of the delay time T2 to the time Ta required for a 60 degrees electrical angle rotation.
θ2=(T2/Ta)×60° (6)
From equation (6), since the delay time T2 is fixed, when the rotational speed increases and the time Ta shortens, the value of T2/Ta increases, and the delay phase θ2 increases. Note that mapping equation (6) also allows the calculation to be smoothly performed.
From the above, the timing Ew of switching the excitation becomes
Ew=30−(θ1+θ2) (7)
By correcting the timing Ew using a map, the timing Ew can be quickly calculated. Moreover, by using the corrected timing Ew, the excitation can be accurately changed without relying on the rotational speed.
Next, the case in which the rotational speed is already in the region R2 during start-up shall be explained.
As shown in
The situation in which the rotational speed is in the region R3 during start-up shall be described.
Even by performing step S101 to step S107 in
Accordingly, when the rotor position signal cannot be detected during a predetermined time of, for example, 1 to 9 seconds (corresponding to step S110), the rotational direction determining device 23 determines that the rotor 41 is in a state of reverse rotation.
In this case, the control unit 11 shown in
When the brake energization time has elapsed, the start-up process is performed using the inductance detection. Since the radiator fan is a system with large friction, the mechanical time constant is large. When forcibly stopped during reverse rotation, since time is required before beginning to rotate in the reverse direction again with wind force, the rotational speed remains in the region R1. Subsequently, steps S103 to step S108 are performed and the transition is made to the steady driving mode.
According to the present embodiment, by performing two-phase energization, it is possible to investigate the size of the inductance from the square-wave pulse voltage width. The pulse width can thus be readily measured compared to the conventional case of measuring the voltage rising time, and there is no need to add special circuits. The device constitution can thus be simplified, and a reduction in the manufacturing cost can be achieved.
In the case of the magnetic flux produced by the coil and the magnetic flux produced by the magnet being in the same direction, that is, at a rotor position in which the magnetic flux flows readily between the coil and the magnet, the inductance becomes small. Given this fact, the rotor stop position can be detected with greater accuracy and stability compared to conventional methods.
By using a sequence of excitation patterns that generate square-wave pulse voltages, that is, a switching sequence of executing excitation patterns that perform non-energization when changing from N-pole magnetization to S-pole magnetization in the rotor stop position searching sequence, it is possible to improve the detection accuracy of detecting inductance by hindering the influence of residual magnetization of the iron core around which the coil winds.
Note that the rotor position estimating device 31 may investigate the maximum value instead of investigating the minimum value of the square-wave pulse voltage width. In this case, the square-wave pulse voltage width detecting device 29 stores the largest pulse width in the storage device 29A in association with the excitation pattern at that time. The start-up excitation device 36 starts up the brushless motor 1 by selecting with the start-up excitation device 36 the energization pattern that lags by 60 degrees in the rotational direction from the excitation pattern that provides the maximum value of the pulse width. For example, in the example shown in
Also, the square-wave pulse voltage widths may be measured a plurality of times each. For example, the case of measuring two times each will be explained referring to
The square-wave pulse voltage width detecting device 29 stores all of the square-wave pulse voltage widths (count values) measured twice or only the square-wave pulse voltage widths (count value) measured on the second time in the storage device 29A in association with the excitation pattern at that time. The stop position estimating process of step 24 compares the size of the square-wave pulse voltage widths measured on the second time in the similar way as described above. The excitation pattern of a minimum square-wave pulse voltage width is then determined as the start-up excitation pattern.
By doing so, when the brushless motor 1 has a constitution that is easily influenced by the residual magnetization of the coil iron core, it is possible to further reduce the influence of the residual magnetization and therefore increase the accuracy of detecting the inductance.
Here, the stop position estimating process may calculate the average value of the square-wave pulse voltage widths (count values) measured a plurality of times for the same excitation pattern and compare the size of the average values in the manner described above. By performing the averaging process, it is possible to further improve the accuracy of detecting the inductance. Even in the case of acquiring the square-wave pulse voltage widths a plurality of times, the rotor stop position and start-up excitation pattern may be determined by checking the maximum value instead of the minimum value.
Also, in this embodiment, since a coasting state is created during start up of the brushless motor 1, it is possible in a state of no noise to perform position detection of the rotor 41 that starts to rotate in a state of all phases released. For this reason, the rotor position can be detected quickly and accurately.
The energization time until coasting (Ts1) is within a range in which reverse torque does not occur. Therefore, the rotor position can be correctly detected without the rotor 41 greatly decelerating during the coasting.
When using the second and subsequent signals SL2 to SL4 without using the first signal SL1 that occurs during the coasting, correct detection is possible even when a signal is generated due to the square-wave pulse voltage during the first signal.
Here, the brushless motor 1 is, for example, a fan motor or fuel pump motor, a motor with large inertia, a slotless motor without cogging torque, and a low-loss motor in which there is little loss due to friction or cogging torque or the like. In a slotless motor, since there is no slot core, the rotor stop position cannot be detected by inductance detection. However, since the inertia is extremely small, it is possible to easily attract the rotor to a predetermined rotational position by energization when detecting the stop position of the rotor. Therefore, it is acceptable to determine the stop position by such a method and then select an energization pattern in which the phase lags 120 degrees electrical angle from the stop position for the start-up energization pattern. In this way, the rotor stop position detection method and the start-up excitation pattern determination method can use various methods without being limited to a method based on inductance.
Also, according to this embodiment, when starting the brushless motor 1, even when the rotor 41 is rotating in reverse, detection of the rotor position is possible using the inductance of the coil by performing a brake process. By starting the brushless motor 1 from here, it is possible to quickly shift to steady driving by 120 degree energization. During non-energization of the brushless motor 1, by performing start-up control in accordance with whether the rotor 41 is in a state of rotating forward or rotating in reverse due to the effects of wind or the like, or is in a stopped state, it is possible to reliably set the brushless motor 1 into motion. For example, in the case of using the brushless motor 1 for driving of a radiator fan in an engine cooling system for an automobile and the like, it is possible to improve the reliability of the system.
This embodiment uses reverse rotation specific logic in addition to forward rotation specific logic. The constitution of the apparatus is identical to that of the first embodiment.
In step S110A, the rotor position is detected by detecting the induced voltage using the reverse rotation specific logic. The reverse rotation specific logic is selected by the rotational direction detection logic selection device 24 in the case of the rotational direction determining device 23 determining that the brushless motor 1 is rotating in reverse. The reverse rotation specific logic is formed of the induced voltage signal detection logic as shown in Table 2 and the square-wave pulse voltage ending edge determination logic as shown in Table 1 and is registered in the separating device 21. This reverse rotation specific logic is employed, and when the edge corresponding to the rotor position signal of each phase is detected, level detection of the other phases is performed to distinguish between the rotor position signal and the switching pulse, and the rotor position is detected. The process here is identical to the steady driving mode in the first embodiment, other than using a different logic.
When the rotor position detection process is performed and the rotor position detection signal has actually been obtained (“Yes” in step S110B), the processing from step S111 onward is carried out. Since it is only necessary to confirm rotating in reverse, the rotor position detection signal may be generated at least once. The processing from step S111 onward is the same as in the first embodiment.
In contrast, when the rotor position detection signal is not obtained (“No” in step S110B), after standing by for a certain time (“Yes” in step S110C), the processing proceeds to step S111.
In this embodiment, it is possible to reliably detect that the rotor is in a reverse rotational state by using reverse rotation specific logic. Other effects are identical to the first embodiment.
This embodiment initially performs a brake process.
As shown in
Also, as shown in
While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting.
For example, in the case of the terminal voltage fluctuating such as when the source voltage fluctuates, it is preferable to use a level conversion circuit instead of the voltage dividing circuit 14. The level conversion circuit uses a transistor, a field effect transistor (FET), and a comparator and the like, and is constituted so as to lower the terminal voltage in accordance with the source voltage.
The energization control during start-up monitors the current value from the shunt resistor 13A, and may control the value so as to remain below a predetermined value, and is not limited to a duty ratio of 50%.
The initial energizaton time Ts1 may be obtained by substituting predetermined physical constants in voltage/current equations and position/torque equations or may be determined by simulation.
When acceleration to a sufficient rotational speed for rotor position detection is not possible only with the initial energizaton time Ts1, sufficient acceleration may be achieved by performing a forced energization by a plurality of open loops before shifting to a coasting state. For example, as shown in
Note that in
Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.
Number | Date | Country | Kind |
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2006-206390 | Jul 2006 | JP | national |
2006-242647 | Sep 2006 | JP | national |
2007-000469 | Jan 2007 | JP | national |
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6704261 | Watt et al. | Mar 2004 | B2 |
20040036436 | Tieu | Feb 2004 | A1 |
Number | Date | Country |
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6-25224 | Apr 1994 | JP |
2001-128485 | May 2001 | JP |
2001-211684 | Aug 2001 | JP |
2002-335691 | Nov 2002 | JP |
2004-040943 | Feb 2004 | JP |
Number | Date | Country | |
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20080048598 A1 | Feb 2008 | US |