JP5233966B2 - Motor control device and motor control program - Google Patents

Description

  The present invention relates to a motor control device that performs feedback control of a motor, and a motor control program.

  As the motor control device, there is known a seat belt retractor that winds up a seat belt when the possibility of a vehicle collision is increased (see, for example, Patent Document 1).

International Publication No. 2006/043590 Pamphlet

  By the way, in the motor control device used for the seat belt retractor, the wiring for supplying electric power to the motor (motor wiring) is short-circuited from the viewpoint of preventing a large current from flowing through the motor and the control circuit for controlling the motor. It is preferable to have a function of detecting.

  In order to detect a short circuit in the motor wiring, it is conceivable to detect whether or not the current value supplied to the motor exceeds a threshold value. However, in the seat belt retractor, when the seat belt can no longer be wound, the motor is locked. Since a large current may flow, it is considered that there is a possibility of erroneous detection that a short circuit is detected even in a normal state in a method of simply detecting a short circuit based on whether or not the current value exceeds a threshold value.

  Accordingly, in view of such a problem, in a motor control device used for a seat belt retractor, a technique capable of preventing erroneous determination that the motor wiring is short-circuited when the motor wiring is not short-circuited is provided. It is an object of the present invention.

  The motor control device according to claim 1, wherein the determination means starts the operation of the motor, and then the motor is locked as the driven object is locked. The controlled value is monitored within the non-lock period representing the period up to and until it is determined whether or not the controlled value exceeds the short reference value set to a value larger than the target value of the feedback control. The short detection means determines that the motor wiring is short when the controlled value exceeds the short reference value.

  In the present invention, the controlled value represents a current value flowing through a motor that drives a driven object or a voltage value applied to the motor. Moreover, what is necessary is just to utilize the preset time as a non-lock period.

  In the present invention, when the motor wiring is not short-circuited, the controlled value may exceed the short reference value when the motor is locked, but the motor is not locked (within the non-lock period). Is used to determine whether or not the motor wiring is short before the motor is locked, using the characteristic that the controlled value is unlikely to exceed the short reference value.

  Therefore, according to such a motor control device, it is possible to prevent erroneous determination that the motor wiring is short-circuited even though the motor wiring is not short-circuited. Therefore, it is possible to improve the accuracy of detecting motor wiring shorts.

  By the way, in the motor control device according to claim 1, as described in claim 2, the determination means determines whether or not the controlled value repeatedly exceeds the short reference value within the non-lock period, The short detection means may determine that the motor wiring is short-circuited when the number of times the controlled value exceeds the short reference value is equal to or more than a reference number set in advance to a value of 2 or more.

  According to such a motor control device, it is not determined that the motor wiring is short-circuited unless the number of times that the controlled value exceeds the short reference value is two times or more. When the value is temporarily exceeded, it can be determined not to be a short circuit. Therefore, it is possible to improve the accuracy when detecting a short circuit in the motor wiring.

  Furthermore, in the motor control device according to claim 2, as described in claim 3, the short detection means is the number of times that the controlled value exceeds the short reference value with respect to the number of times the determination means repeatedly performs the determination. If the ratio is equal to or higher than a preset reference ratio, it may be determined that the motor wiring is short-circuited.

  According to such a motor control device, it is possible to further improve the accuracy when detecting a short in the motor wiring by setting an appropriate reference ratio according to the operation characteristics of the motor and the driven object. .

  Next, the invention according to claim 4 is a motor control program for causing a computer to realize functions as respective means constituting the motor control device according to any one of claims 1 to 3. It is characterized by being.

  According to such a motor control program, at least the same effect as that of the motor control device according to the first aspect can be enjoyed.

It is a block diagram which shows schematic structure of a pre-crash safety system. It is a block diagram showing a schematic configuration of a seat belt ECU. It is a flowchart which shows a motor control process. It is a flowchart (a) which shows an overcurrent determination process, and a flowchart (b) which shows a motor control process.

Embodiments according to the present invention will be described below with reference to the drawings.
[Pre-crash safety system]
Here, FIG. 1 is a block diagram showing a schematic configuration of a pre-crash safety system including a seat belt control device to which the present invention is applied. Hereinafter, an automobile equipped with a pre-crash safety system is referred to as a host vehicle.

  The pre-crash safety system 1 increases the braking force of the host vehicle when the possibility of a collision between an obstacle on the traveling path and the host vehicle (hereinafter referred to as a collision possibility) is high. It is intended to strengthen the binding force of the belt.

  In order to realize this, as shown in FIG. 1, the pre-crash safety system 1 includes a front monitoring device 5 that monitors the traveling path of the host vehicle, and a brake control device 7 that controls a brake mechanism provided in the host vehicle. And at least one seat belt retractor 10 for retracting each of the seat belts provided in the host vehicle and the output from the front monitoring device 5 determines whether or not the collision possibility is equal to or higher than a set threshold value. In both cases, the pre-crash control device (so-called electronic control unit (ECU)) 6 that controls the brake control device 7 according to the determination result and the pre-crash control device 6 determine that the possibility of collision is greater than or equal to a set threshold value. Then, a seat belt control device (hereinafter referred to as a seat belt control device) that controls each of the seat belt retractor 10 so as to strengthen the restraint force of the seat belt. Seatbelt also called ECU) and a 20 (motor control unit).

  Among these, the forward monitoring device 5 detects a target such as a preceding vehicle by transmitting and receiving a radar wave, and acquires target information including the position and speed of the target and the own vehicle. The apparatus is configured mainly with a device and the like, and the acquired target information is output to the pre-crash control device 6. The forward monitoring device 5 is arranged so as to capture the traveling direction of the host vehicle, and an in-vehicle camera that acquires target information based on the captured image, or a target such as a preceding vehicle by transmitting and receiving laser light. May be configured around a laser radar device that detects target and acquire target information, or may be configured by combining these (that is, a millimeter wave radar device, an in-vehicle camera, and a laser radar device). Good.

  Further, the pre-crash control device 6 is configured around a known microcomputer including at least a CPU, a ROM, a RAM, and a bus connecting them. Then, the pre-crash control device 6 calculates the possibility of collision according to the target information acquired from the forward monitoring device 5, notifies the calculated possibility of collision in the host vehicle, and calculates the calculated possibility of collision. Is determined to be greater than or equal to a first set threshold value that is defined in advance as one of the set threshold values. Thus, a process of increasing the braking force of the host vehicle is executed. In addition to this, the pre-crash control device 6 determines whether or not the collision possibility is equal to or higher than a second setting threshold value that is defined in advance as one of the setting threshold values. If it is equal to or greater than the second set threshold value, the seat belt control device 20 outputs an activation command for starting control of the restraining force of the seat belt to the seat belt control device 20.

[Seat belt retractor]
Next, the seat belt retractor 10 will be described.
Each of the seat belt retractors 10 is a well-known part of a seat belt mechanism that restrains a person (for example, a driver or the like, hereinafter also referred to as an occupant) seated on a seat provided in the own vehicle to the seat. The seat belt band (hereinafter referred to as webbing) 12 can be pulled out and wound.

  That is, each seat belt retractor 10 includes a spool 13 to which one end of the webbing 12 is fixed, a motor 11 that generates a driving force for driving the spool 13, and a driving force generated by the motor 11 to the spool 13. A transmission gear group (not shown), a clutch 14, and a spool 13 are rotatably held, and the motor 11, the gear group, and the clutch 14 are supported to fix the seat belt retractor 10 to the own vehicle. And a holding member (not shown).

  The motor 11 is configured as a well-known DC motor (DC motor) that converts electrical energy into rotational motion (that is, motion energy), and generates a driving force according to the energization direction.

  Further, the clutch 14 is engaged with the first member (not shown) to which the driving force generated by the motor 11 is transmitted (generally referred to as being fixed to the driving side), and the spool 13 is engaged with the first member. And a second member (not shown) that transmits driving force (generally, fixed to the driven side). However, the clutch 14 has an initial position in which the first member is disengaged from the second member when a driving force in a predetermined direction (hereinafter referred to as a forward direction) is transmitted to the first member. When the driving force in a direction different from the forward direction (hereinafter referred to as the reversal direction) is transmitted to the first member, the engagement between the first member and the second member is established. The combination is released and the first member is configured to return to the initial position.

  That is, the clutch 14 is configured to have a predetermined “play” from when the forward driving force is transmitted to the first member to when it is engaged with the second member. Is transmitted to the first member, and a predetermined time is required until the first member engages with the second member and the spool 13 rotates.

  Therefore, in the seatbelt retractor 10, when the motor 11 generates a forward driving force, the first member to which the driving force is transmitted starts rotating from the initial position after a predetermined time has elapsed. The first member and the second member are engaged (that is, the clutch 14 is connected). Then, the spool 13 rotatably supported by the holding member rotates in a direction corresponding to the forward direction, and the webbing 12 is wound around the spool 13 itself.

  In the seat belt retractor 10, when the driving force in the reverse direction is generated by the motor 11, the first member to which the driving force is transmitted releases the engagement with the second member and returns to the initial position. The “play” of the clutch 14 is maximized.

[About the seat belt controller]
Next, the seat belt control device will be described. Here, FIG. 2 is a block diagram showing a schematic configuration of the seat belt ECU.

  As shown in FIG. 2, the seat belt ECU 20 includes an energization to the motor 11, a drive circuit 21 that cuts off the energization, a shunt resistor 25 </ b> A for detecting a current value flowing through the motor 11, and a detected current value. (Hereinafter, also referred to as a detected current value) is amplified by the amplifier 25c, and is then subjected to A / D conversion and an A / D converter 25B for output, and according to the output from the current detection circuit 25, A microcomputer (hereinafter also referred to as a microcomputer) 30 that generates and outputs a motor control signal for controlling the motor 11 via the drive circuit 21 is provided.

  The motor control signal is for energizing the motor 11 if the signal level is high, and for de-energizing the motor 11 if the signal level is low. In other words, the motor control signal controls the duty ratio (that is, the ratio between the high level period and the low level period), whereby the torque generated in the motor 11, in other words, the current value flowing through the motor 11. Is to adjust.

  Among these, the drive circuit 21 is an H-bridge circuit having four N-channel FETs (field effect transistors). Of the four N-channel FETs, two FETs 22A and 22B have a microcomputer 30 at their gates. However, the battery 29 is connected to the drain, the motor 11 is connected to the source, the two FETs 23A and 23B are connected to the microcomputer 30 at the gate, the motor 11 is connected to the drain, and the source is grounded via the shunt resistor 25A.

  In the drive circuit 21, each FET 22A, 22B, 23A, 23B is provided with a diode having the source side of each FET as an anode and the drain side as a cathode. These diodes are omitted in FIG.

  In such a drive circuit 21, if the motor control signal input from the microcomputer 30 to each FET 22, 23 is high level, the FET 22, 23 to which the motor control signal is input is turned ON, and the motor control signal is low. If the level is reached, the FETs 22 and 23 to which the motor control signal is input are turned off. However, the driving circuit 21 and the motor 11 in the present embodiment generate a forward driving force in the motor 11 when the FETs 22A and 23A are turned on, and the motor 11 when the FETs 22B and 23B are turned on. Wiring is performed so that a driving force in the reverse direction is generated.

That is, the drive circuit 21 can switch the driving direction of the motor 11 by switching the FETs 22 and 23 that can be energized between the drain and the source.
Hereinafter, the FETs 22A and 23A are referred to as normal FETs 22A and 23A, and the FETs 22B and 23B are referred to as inverted FETs 22B and 23B. Further, a motor control signal that is input to the forward FETs 22A and 23A, that is, a motor control signal for generating a forward driving force in the motor 11, is referred to as a forward control signal, and is input to the inverting FETs 22B and 23B. A motor control signal for causing the motor 11 to generate a driving force in the reverse direction is referred to as a reverse direction control signal.

  By the way, since the FETs 22A and 22B are N-channel FETs, it is necessary to supply the FETs 22A and B with a specified voltage higher than the power supply from the battery 29 in order to turn on the FETs 22A and 22B with certainty. For this reason, all motor control signals output from the microcomputer 30 are input to the drive circuit 21 via the pre-driver circuit 24 having the signal level at the high level as a specified voltage.

  Next, the microcomputer 30 stores the ROM 31 that stores data and programs that need to retain the contents even when the power is turned off, the RAM 32 that stores data temporarily generated during the processing, and the ROM 31 and the RAM 32. It is a well-known one provided with at least a CPU 33 for executing the processing program and a bus connecting them.

  The ROM 31 includes an information acquisition process for transmitting / receiving information to / from other electronic control devices (that is, ECUs other than the seat belt ECU 20) mounted on the host vehicle such as the pre-crash control device 6 and the motor 11. A processing program is stored for the CPU 33 to execute a motor control process for controlling the duty ratio (that is, the pulse width) of the motor control signal that is always output so that the flowing current value becomes a predetermined target value. Yes.

[About motor control processing]
Next, the motor control process will be described.
Here, FIG. 3 is a flowchart showing a motor control process executed by the CPU 33.

  This motor control process is a process that is started when the vehicle power source such as an ignition switch (not shown) is turned on, for example. In this process, the processes after S130 are repeated at a predetermined cycle (for example, every 5 ms). Executed. Specifically, first, when the motor control process is started, the duty ratio of the forward control signal (hereinafter also referred to as drive duty) is set to the initial duty (for example, 50% duty ratio) (S110).

  Then, it is determined whether or not a start command is input from the pre-crash control device 6 (S120). If the start command is not input as a result of the determination (S120: NO), the process waits until it is input. When a start command is input (S120: YES), output of a forward control signal that is the initial duty set in S110 is started.

  Subsequently, an overcurrent determination process to be described later is performed (S130). When the overcurrent determination process ends, it is determined whether an end command for stopping the output of the forward control signal is input (S140). If no termination command is input as a result of the determination (S140: NO), the detected current value from the current detection circuit 25 is read, and the read detected current value is compared with a predetermined target value (S150). .

  As a result of the comparison, if the detected current value is smaller than the target value (S150: small), the drive duty is increased (that is, the period of high level is increased) (S160), and then the process returns to S130. As a result of the comparison, if the detected current value is larger than the target value (S150: large), the drive duty is reduced (that is, the period of high level is shortened) (S170), and then the process returns to S130. . However, a lower limit value (for example, 10%) and an upper limit value (for example, 100%) are set for the drive duty, and a value within this range is set.

  Further, as a result of the comparison, if the detected current matches the target value (including that the detected current is within a predetermined range preliminarily defined around the target value) (S150: within the allowable range). The process returns to S130 while maintaining the drive duty.

  Note that when the detected current value is compared with the target value in the process of S150, the magnitude of these differences (difference in absolute value) is also detected. Then, a change amount of the duty ratio in the processing of S160 and S170 is set according to the magnitude of this difference, and the duty ratio is increased or decreased by this change amount.

  That is, when the difference between the detected current value and the target value is large, the duty ratio increase or decrease is set large, and when the difference is small, the duty ratio increase or decrease is set small. By changing the duty ratio in this way, the detected current value can be quickly matched with the target value.

By the way, as a result of the determination in S140, if an end command is input, this motor control process is ended.
In the motor control process described above, the processes of S150 to S170 are repeated so that the detection result of the current detection circuit 25 (that is, the torque generated by the motor 11) becomes a predetermined target value. So-called PWM control is performed to control the duty ratio (that is, pulse width) of the direction control signal (or the inversion direction control signal).

  Here, in the seat belt control device 20 of the present embodiment, the wiring of the motor 11 is compared by comparing the detected current value with the short reference value in the overcurrent determination process and the overcurrent detection process described below. It is determined whether or not (motor wiring) are short-circuited. This is because if the motor wires are short-circuited, a large current flows through the drive circuit 21 and the current detection circuit 25, and the FETs 22A, 23A, 22B, and 23B and the shunt resistor 25A may be damaged by the large current.

  For example, when the motor wires are short-circuited in the vicinity of the motor 11, the resistance and reactance in the motor wires are increased. Therefore, when the duty ratio is small, only a small current flows through the motor wires. For this reason, when the processing of S150 to S170 is performed next, the duty ratio increases. When the duty ratio increases, the current value increases rapidly.

  When the current value increases in this way, the next time the processing of S150 to S170 is performed, the duty ratio is set to be small, and at this time, only a small current flows through the motor wiring. That is, when the motor wirings are short-circuited in the vicinity of the motor 11, when the processes of S150 to S170 are repeated, an oscillation state in which the current value is large and small is repeated.

  On the other hand, when the motor wiring is short-circuited at a site away from the motor 11 (near the pre-driver circuit 24), the resistance and reactance in the motor wiring are reduced, so that even when the duty ratio is small, the motor A large current flows through the wiring. That is, when the motor wiring is short-circuited at a site away from the motor 11, the current value is always large.

  From the above, in order to determine that the cause of the large current flowing in the motor wiring is due to the short circuit between the wirings of the motor 11, if a large current is detected in about half of the energization time. It will be good.

  However, if the motor 11 is locked with a large duty ratio, such as when the seat belt (webbing 12) is locked, a large current may flow temporarily due to the characteristics of the motor 11 that is a DC motor. For this reason, in the overcurrent determination process and the overcurrent detection process described below, it is determined whether or not a large current flows through the wiring of the motor 11 for a certain period of time or more within the time until the seat belt is locked. By doing so, a short state in which a large current flows in the motor wiring is detected.

[Overcurrent judgment processing]
Detailed overcurrent determination processing will be described. FIG. 4A is a flowchart showing an overcurrent determination process in the motor control process. That is, the overcurrent determination process is a process that can be performed while performing feedback control of the motor 11.

  In the overcurrent determination process, first, the number of overcurrent detections recorded in a memory such as the RAM 32 is compared with a preset specified number (reference number, for example, 40 times) (S210: short detection means). Here, the number of times of overcurrent detection represents the number of times that an overcurrent has been detected in an overcurrent detection process described later, and data of this number is recorded in a memory such as a RAM.

The specified number here is set to a predetermined ratio corresponding to the overcurrent detection period (the number of attempts to detect overcurrent).
As a result of the comparison, if the overcurrent detection count is less than the specified number (S210: NO), the overcurrent determination process is terminated as it is. As a result of the comparison, if the number of overcurrent detections is equal to or greater than the specified number (S210: YES), it is determined that the overcurrent is abnormal (short circuit between motor wires), and this result is recorded in a memory such as a RAM. (S220: Short detection means).

Then, an end command to end the operation of the motor 11 is output (S230), and the overcurrent determination process is ended.
[About overcurrent detection processing]
Next, the overcurrent detection process will be described. FIG. 4B is a flowchart showing a motor control process executed by the CPU 33 in parallel with the motor control process. The overcurrent detection process is a process that is repeatedly performed at a cycle (for example, every 500 μS) shorter than the cycle at which S130 to S170 of the motor control process described above are performed. It is assumed that the overcurrent detection count is cleared at the first activation of this process.

  In the overcurrent detection process, first, it is determined whether or not it is within an overcurrent detection period (for example, 50 ms) (S310). Here, the overcurrent detection period means a non-lock period indicating a period from the start of the operation of the motor 11 until the motor 11 is locked as the driven object is locked. The period is set based on experiments in advance.

  Subsequently, the detected current value from the current detection circuit 25 is read, and the read detected current value is compared with a predefined short reference value (overcurrent reference value) (S320: determination means). Note that the short reference value is set to a value larger than the target value to be compared in the process of S150.

  If the detected current value is equal to or greater than the short reference value as a result of the comparison (S320: YES), the overcurrent detection count is incremented and recorded in a memory such as the RAM 32 (S330), and the overcurrent detection process is terminated. If the detected current value is less than the short reference value as a result of the comparison (S320: NO), the overcurrent detection process is immediately terminated.

[Operations and effects of this embodiment]
In the seat belt control device 20 described in detail above, the microcomputer 30 locks the motor 11 as the driven object is locked after starting the operation of the motor 11 in the overcurrent detection process. The controlled value is monitored within the non-locking period that represents the period until the operation is performed, and it is determined whether or not the controlled value exceeds the overcurrent reference value set to a value larger than the target value of the feedback control. To do. Then, the microcomputer 30 of the seat belt control device 20 determines that the motor wiring is short-circuited when the controlled value exceeds the overcurrent reference value in the overcurrent determination process.

  In other words, when the motor wiring is not short-circuited, the controlled value may exceed the overcurrent reference value when the motor 11 is locked, but in a state where the motor 11 is not locked (within the non-lock period). The characteristic that the controlled value is unlikely to exceed the overcurrent reference value is utilized to determine whether the motor wiring is short before the motor 11 is locked.

  According to such a seat belt control device 20, it is possible to prevent erroneous determination that the motor wiring is short-circuited even though the motor wiring is not short-circuited. In particular, even when the winding of the seat belt is completed when the motor wiring is not short-circuited and the motor 11 is locked, a large current flows temporarily to the motor 11. There is no misjudgment. Therefore, it is possible to improve the accuracy of detecting motor wiring shorts.

  Further, in the seat belt controller 20, the microcomputer 30 determines whether the controlled value repeatedly exceeds the overcurrent reference value within the non-lock period in the overcurrent detection process. In the overcurrent determination process, it is determined that the motor wiring is short-circuited when the number of times that the controlled value exceeds the overcurrent reference value is equal to or greater than the reference number set in advance to a value of 2 or more.

  According to such a seat belt control device 20, it is not determined that the motor wiring is short-circuited unless the number of times that the controlled value exceeds the overcurrent reference value is two times or more. Can be determined not to be short-circuited when the overcurrent reference value is temporarily exceeded. Therefore, it is possible to improve the accuracy when detecting a short circuit in the motor wiring.

  Further, the microcomputer 30 of the seatbelt control device 20 sets the overcurrent reference value to the controlled value with respect to the number of times of repeated determination in the overcurrent detection process (100 times in the above embodiment) in the overcurrent determination process. It is determined that the motor wiring is short-circuited when the ratio of the number of times exceeds the preset reference ratio (40 times that is 40% in the above embodiment).

  According to such a seat belt control device 20, by setting an appropriate reference ratio according to the operating characteristics of the motor 11 and the driven object, the accuracy when detecting a short circuit in the motor wiring is further improved. be able to.

[Other Embodiments]
Embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention.

  For example, in the above embodiment, the current value is monitored in the process of S320, but other parameters such as a voltage value may be monitored.

  DESCRIPTION OF SYMBOLS 1 ... Pre-crash safety system, 5 ... Forward monitoring apparatus, 6 ... Pre-crash ECU, 7 ... Brake control apparatus, 10 ... Seat belt winding device, 11 ... Motor, 12 ... Webbing, 13 ... Spool, 14 ... Clutch, 20 DESCRIPTION OF SYMBOLS ... Seat belt control device, 21 ... Drive circuit, 22A, 23A ... Forward rotation FET, 22B, 23B ... Inversion FET, 24 ... Pre-driver circuit, 25 ... Current detection circuit, 25A ... Shunt resistance, 25B ... A / D converter 25C ... Amplifier, 29 ... Battery, 30 ... Microcomputer, 31 ... ROM, 32 ... RAM, 33 ... CPU.

Claims (4)

A controlled value representing a current value flowing through a motor or a voltage value applied to the motor used when driving a driven object held in a state where the belt of the seat belt is wound to wind up the seat belt is a predetermined value. A motor control device that performs feedback control to achieve a target value,
The controlled value is monitored in a non-lock period that represents a period from the start of operation of the motor until the motor is locked as the driven object is locked. Determination means for determining whether a control value exceeds a short reference value set to a value larger than the target value;
When the controlled value exceeds the short reference value, short detection means for determining that the motor wirings that supply power to the motor are short-circuited;
A motor control device comprising: The motor control device according to claim 1,
The determination means determines whether the controlled value repeatedly exceeds a short reference value within the non-lock period,
The short detection means determines that the motor wiring is short-circuited when the number of times the controlled value exceeds the short reference value is equal to or greater than a reference number set in advance to a value of 2 or more. A motor control device. The motor control device according to claim 2,
The short detection means is configured such that when the ratio of the number of times the controlled value exceeds the short reference value to the number of times the determination means repeatedly performs determination is equal to or greater than a preset reference ratio, A motor control device characterized in that it is determined that a short circuit has occurred.   The motor control program for making a computer implement | achieve the function as each means which comprises the motor control apparatus of any one of Claims 1-3.

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