JP2024066905A - Electric motor control device - Google Patents

Abstract

An electric motor control device is provided that can suppress shock caused by stopping an electric motor even when the operating range of the electric motor is narrow.
[Solution] In an electric motor control device that performs slow start-stop control of an electric motor that slides an electric seat of a vehicle, when the output of the electric motor is decreased at a predetermined downward gradient in the slow stop control, a slow stop control start position, which is the rotational position of the electric motor at which the slow stop control starts, is calculated so that the electric motor stops at a predetermined target stop position, and even if this calculated slow stop control start position is a position where the slow start control is being implemented, the slow stop control is started at that position. This makes it possible to suppress shock caused by stopping the electric motor even when the operating range of the electric motor is narrow.
[Selected figure] Figure 2

Description

The present invention relates to an electric motor control device.

Conventionally, electric seats are known as seats that are applied to vehicles, etc. This type of seat uses an electric motor as a drive source for forward and backward sliding movement and tilting of the seat back (hereinafter, these movements are collectively referred to as seat movement).

As disclosed in Patent Document 1, in this type of electric motor control, slow start-stop control is performed to achieve both shortening the time required to move the seat to the target position (target stop position) and suppressing large fluctuations in inertial force (shock occurrence) at the start and end of the movement. This slow start-stop control suppresses shock at the start of movement by controlling the electric motor to gradually increase its output when the seat starts to move (hereinafter referred to as slow start control), and after the slow start control, controls the electric motor to keep its output constant (maximum) (hereinafter referred to as constant output control) to move the seat at a high speed, and then controls the electric motor to gradually decrease its output when the seat stops moving (hereinafter referred to as slow stop control) to suppress shock at the time of stopping.

Figure 3(a) is a diagram showing an example of the relationship between time (elapsed time) and the change in the output of the electric motor in the slow start-stop control when the distance from the start position of the seat movement to the target stop position is relatively long. As shown in this figure (a), in the conventional slow start-stop control, after the seat movement starts, the slow start control is performed (see the slow start control period in the figure), and after a predetermined time has passed (when timing t1 in the figure is reached), the control shifts to constant output control (see the constant output control period in the figure). Then, after the constant output control is started, after a predetermined time has passed (when timing t2 in the figure is reached), the slow stop control is started (see the slow stop control period in the figure), and when the predetermined time has passed and the output of the electric motor has decreased to a certain extent (see timing t3 in the figure when the seat movement speed has sufficiently decreased), the output of the electric motor is reduced to zero to stop the seat movement.

JP 2017-132387 A

However, in conventional slow start-stop control, if the distance from the seat start position to the target stop position is short (for example, if the distance is short when performing slow start-stop control to a pre-stored target stop position of the seat), the output of the electric motor is set to zero midway through the slow start control (before switching to constant output control) and the control is terminated.

Figure 3(b) is a diagram showing an example of the relationship between time and the change in the output of the electric motor in the slow start-stop control (the dashed line shows the relationship between time and the change in the output of the electric motor shown in Figure 3(a)). In this way, if the seat reaches the target stop position before the transition to constant output control (timing t4, which is the stage before the aforementioned timing t1 is reached), the output of the electric motor is set to zero and the control is terminated even during the slow start control (the output of the electric motor is set to zero when timing t4 is reached), and the seat, which is accelerating as the output of the electric motor increases, suddenly stops, causing a relatively large shock and causing discomfort to the occupant.

However, this issue is not limited to electric seats used in vehicles, but can also occur in various devices equipped with electric motors that perform slow start-stop control.

The present invention was made in consideration of these points, and its purpose is to provide an electric motor control device that can prevent the electric motor from stopping suddenly even when the operating range of the electric motor is narrow.

The solution of the present invention to achieve the above object is premised on an electric motor control device capable of performing slow start control to gradually increase the output of the electric motor when the electric motor starts to rotate, constant output control to maintain the output of the electric motor constant after the slow start control, and slow stop control to decrease the output of the electric motor at a preset downward gradient when the electric motor stops rotating. This electric motor control device is characterized by having a slow stop control start position calculation unit that calculates a slow stop control start position, which is the rotational position of the electric motor at which the slow stop control starts, so that the electric motor stops at a predetermined target stop position when the output of the electric motor is decreased at the downward gradient, and a slow stop control start command unit that starts the slow stop control at the slow stop control start position calculated by the slow stop control start position calculation unit even if the slow stop control is being performed at that position.

Due to this specification, in a situation where the interval between the rotation start position of the electric motor and the target stop position is short (the operating range of the electric motor is narrow) and the target stop position is reached during slow start control, slow stop control is started even if the electric motor is in a position where slow start control is being implemented. In other words, the distance required for slow stop control from the target stop position (the rotation range of the electric motor) is calculated backwards, and slow stop control is started before the target stop position. This makes it possible to stop the electric motor at a predetermined target stop position while decreasing the output of the electric motor at a preset downward gradient. In other words, even if the operating range of the electric motor is narrow, it is possible to suppress shock caused by stopping the electric motor.

In the present invention, the slow stop control is started at the slow stop control start position even if the slow start control is currently being performed. Therefore, even if the operating range of the electric motor is narrow, shocks caused by stopping the electric motor can be suppressed.

1 is a diagram showing a schematic configuration of an electric motor control device according to an embodiment; Figure 2(a) is a diagram showing an example of the relationship between the amount of movement and the change in the output of the electric motor in slow start-stop control when the distance from the start position of the seat movement to the target stop position is relatively long in an embodiment, and Figure 2(b) is a diagram showing an example of the relationship between the amount of movement and the change in the output of the electric motor in slow start-stop control when the distance from the start position of the seat movement to the target stop position is short in an embodiment. Figure 3(a) is a diagram showing an example of the relationship between time and change in electric motor output in slow start-stop control in conventional technology when the distance from the start position of the seat movement to the target stop position is relatively long, and Figure 3(b) is a diagram showing an example of the relationship between time and change in electric motor output in slow start-stop control in conventional technology when the distance from the start position of the seat movement to the target stop position is short.

The following describes an embodiment of the present invention with reference to the drawings. In this embodiment, the present invention is applied to a control device (electric motor control device) for an electric motor that slides an electric seat installed in the passenger compartment of a vehicle.

Figure 1 is a schematic diagram showing an electric motor control device 1 according to this embodiment. As shown in this Figure 1, the electric motor control device 1 according to this embodiment controls an electric motor 2 that slides an electric seat installed in the vehicle interior. The electric motor 2 generates torque for sliding the seat. The output shaft (not shown) of the electric motor 2 is connected to the movable part of the seat via a reduction gear. The torque generated by the electric motor 2 is amplified by the reduction gear and transmitted to the movable part of the seat, thereby causing the seat to slide. The mechanism for sliding the seat is well known, so a description thereof will be omitted here.

The electric motor 2 is electrically connected to an on-board battery 3. The on-board battery 3 is a DC power source that can supply power to the electric motor 2 even when the vehicle ignition is off. The electric motor 2 operates with power supplied from the on-board battery 3, and generates torque for sliding the seat. The electric motor 2 can also change its direction of operation (direction of rotation) by switching the direction of the current, which also makes it possible to switch the direction of the sliding movement of the seat.

The electric motor control device 1 includes a control device 4. The control device 4 includes, for example, a processor such as a CPU, a ROM for storing a control program, a RAM for temporarily storing data, and an input/output port. The control device 4 includes functional units 41 to 43 shown in FIG. 1 as functional units realized by the control program. The functions of these functional units will be described later.

The control device 4 is also electrically connected to an operation switch 5 that is operated by the vehicle occupant to slide the seat. The control device 4 starts or stops the electric motor 2 in accordance with the operation of the operation switch 5 by the vehicle occupant. The control device 4 starts or stops the electric motor 2 in accordance with a predetermined switch operation by the vehicle occupant so that the seat moves to a seat position stored in memory (a target stop position of the seat according to the vehicle occupant).

The control device 4 performs PWM drive for the electric motor 2 so that the duty ratio of the on/off of the power supply from the vehicle battery 3 can be varied. The electric motor 2 is PWM driven according to instructions from the control device 4. The control device 4 also performs slow start/stop control, which gradually changes the duty ratio in PWM drive when the electric motor 2 is started and stopped, to gradually change the speed of the electric motor 2. In other words, when the seat starts to move, control (slow start control) is performed to gradually increase the output of the electric motor 2 to suppress shock at the start of movement, and after the slow start control, control (constant output control) is performed to maintain the output of the electric motor 2 constant (maximum) to move the seat at a high speed, and then control (slow stop control) is performed to gradually decrease the output of the electric motor 2 at a preset downward gradient when the seat movement is stopped to suppress shock at the time of stopping.

More specifically, the electric motor control device 1 includes a switching element 6 that controls the drive of the electric motor 2. This switching element 6 is a MOS-FET as a semiconductor element. This switching element 6 has a source terminal that is grounded and a drain terminal that is connected to the electric motor 2. The control device 4 is electrically connected to the gate terminal of the switching element 6, and a signal for PWM drive is input. The control device 4 PWM drives the electric motor 2 by controlling the on/off of the switching element 6.

In addition, a rotation speed sensor 7 is connected to the electric motor 2 to detect the rotation speed (number of rotations) of the electric motor 2. This rotation speed is correlated (proportional) with the sliding movement position of the seat. Furthermore, the relationship between the rotation speed of the electric motor 2 and the sliding movement position of the seat is reproducible. Information on the rotation speed of the electric motor 2 detected by the rotation speed sensor 7 is sent to the control device 4.

2A is a diagram showing an example of the relationship between the movement amount and the change in the output of the electric motor 2 in the slow start-stop control in this embodiment when the distance from the start position of the seat movement to the target stop position is relatively long. In the slow start-stop control in this case, after the seat starts moving, the slow start control is implemented (see the slow start control period in the figure), and after the seat moves to a predetermined movement amount (when the movement amount x1 in the figure is reached), the output control is switched to constant output control (see the constant output control period in the figure). Then, after the constant output control is started, the seat moves to a predetermined movement amount (when the movement amount x2 in the figure is reached), and the output of the electric motor 2 is reduced to a certain extent by moving to the predetermined movement amount (when the movement speed of the seat reaches the movement amount x3 in the figure, which is sufficiently low), and the movement of the seat is stopped.

As mentioned above, in conventional slow start-stop control, when the distance from the seat movement start position to the target stop position is short (for example, when the distance is short when performing slow start-stop control to a pre-stored target stop position of the seat), the output of the electric motor is set to zero in the middle of the slow start control (before switching to constant output control) and the control is terminated (see FIG. 3(b)). As a result, the seat, which is accelerating as the output of the electric motor increases, suddenly stops, generating a relatively large shock and causing discomfort to the occupants, which was an issue.

In this embodiment, to solve this problem, the control device 4 is provided with an information receiving unit 41, a slow stop control start position calculation unit 42, and a slow stop control start command unit 43 as functional units realized by the control program. The following provides an overview of the functions of each of these units.

The information receiving unit 41 can receive information on the rotation speed of the electric motor 2 detected by the rotation speed sensor 7, operation information from the operation switch 5, information on the target stop position of the seat, etc. Since the target stop position of the seat is correlated with the rotation speed of the electric motor 2 (e.g., the number of rotations from a reference position), the target stop position of the seat is given as information on the rotation speed of the electric motor 2.

When performing the slow stop control, the slow stop control start position calculation unit 42 calculates the slow stop control start position, which is the rotational position of the electric motor 2 at which the slow stop control starts, so that the electric motor 2 stops at a predetermined target stop position (target stop position of the seat) when the output of the electric motor 2 is lowered at the previously set downward gradient. In other words, by starting the slow stop control from this calculated slow stop control start position, the electric motor 2 stops at the predetermined target stop position (target stop position of the seat).

The slow stop control start command unit 43 is a functional unit that starts the slow stop control at the slow stop control start position calculated by the slow stop control start position calculation unit 42, even if that position is a position where slow start control is being implemented. In other words, even if the slow start control is being implemented and the sheet movement speed is accelerating as the output of the electric motor 2 increases, the slow stop control is started and the control is switched to one that decreases the output of the electric motor 2 at the downward gradient. In other words, the distance required for the slow stop control from the target stop position (the rotation range of the electric motor 2) is calculated backwards, and the slow stop control is started before this target stop position.

The characteristic operation of this embodiment (changes in the output of electric motor 2) will be described below. Figure 2(b) is a diagram showing an example of the relationship between the movement amount and changes in the output of electric motor 2 in slow start-stop control when the distance from the movement start position of the seat to the target stop position (the position of movement amount x4 in the figure) is short in this embodiment (the dashed dotted line shows the relationship between the movement amount shown in Figure 2(a) and changes in the output of electric motor 2).

As shown in FIG. 2(b), when the distance from the seat start position to the target stop position is short, slow start control is initiated, and before switching to constant output control (for example, when the seat reaches the amount of movement x5 in the figure: the slow start control period in this case is period T1 in the figure), slow stop control is initiated, and when the seat reaches the target stop position (see amount of movement x4 in the figure when the seat movement speed has become sufficiently slow), the output of the electric motor 2 is reduced to zero to stop the seat movement (the slow stop control period is period T2 in the figure). In this case, the position of amount of movement x5 in the figure corresponds to the slow stop control start position as referred to in this invention.

When the distance from the start position of the seat movement to the target stop position is extremely short (for example, when the target stop position is the position of movement amount x6 in the figure), the seat movement speed is relatively slow due to the short slow start control period. In this case, even if the output of electric motor 2 is set to zero during the slow start control and the control is terminated, no major shock will occur, so in this case, as shown by the two-dot chain line in the figure, the seat movement is stopped without implementing slow stop control. The value of the movement amount, which is the threshold value for whether or not to implement this slow stop control (whether or not slow stop control is necessary), is set in advance by experiment or simulation.

--Effects of the embodiment--
As described above, in this embodiment, even if the slow stop control start position is a position where the slow start control is being performed, the slow stop control is started at that position. Therefore, even if the operating range of the electric motor 2 is narrow, it is possible to suppress shock caused by stopping the electric motor 2.

-Other embodiments-
The present invention is not limited to the above embodiment, and all modifications and applications are possible within the scope of the claims and equivalents thereto. For example, in the above embodiment, the present invention is applied to the control of the electric motor 2 that slides the electric seat installed in the passenger compartment of the vehicle. The present invention is not limited to this, and can be applied to the control of an electric motor that tilts the seat back, an electric motor that moves the seat up and down, etc. Furthermore, the present invention is not limited to the electric seat, and can be applied to the control of various electric motors that perform slow start-stop control.

The present invention can be applied to the control of an electric motor that slides an electric seat.

REFERENCE SIGNS LIST 1... Electric motor control device 2... Electric motor 4... Control device 42... Slow stop control start position calculation unit 43... Slow stop control start command unit

Claims (1)

An electric motor control device capable of performing slow start control for gradually increasing an output of an electric motor when the electric motor starts to rotate, constant output control for maintaining the output of the electric motor constant after the slow start control, and slow stop control for decreasing the output of the electric motor at a preset decreasing gradient when the electric motor stops rotating,
a slow stop control start position calculation unit that calculates a slow stop control start position, which is a rotational position of the electric motor at which the slow stop control is started, so that the electric motor stops at a predetermined target stop position when the output of the electric motor is decreased at the downward gradient;
and a slow stop control start command unit that starts the slow stop control at the slow stop control start position calculated by the slow stop control start position calculation unit, even if the slow stop control is at a position where the slow stop control is being implemented.

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