Vibration reduction device for seat and occupant condition estimation system

Abstract

A vibration reduction device (21) for a seat comprises: a reference signal detection sensor (31); an excitation device (32), (232) that imparts reducing vibrations in order to reduce vibrations which are inputted to a seat (4) among disturbance vibrations; a pressure sensor (33) that is positioned within a cushion (12) of the seat (4) and outputs a signal corresponding to pressure inputted via the cushion (12); and an excitation control device (34) that controls the excitation device (32), (232). The excitation control device (34) comprises an error signal calculation unit (61) that, on the basis of the signal outputted by the pressure sensor (33), calculates a vibration component of the pressure sensor (33) as an error signal, and an adaptive control unit (62) that, on the basis of the reference signal and the error signal, performs adaptive control so as to reduce a reference signal effect component included in the error signal, and controls the excitation device (32), (232) on the basis of an output value from the adaptive control.

Description

Seat vibration reduction device and occupant state estimation system

[0001] The present disclosure relates to a vibration reduction device for a seat and an occupant state estimation system.

[0002] Patent Document 1 discloses a vehicle seat control device that aims to effectively reduce discomfort experienced by seat occupants due to vibration. The device includes an actuator between the vehicle body and the seat for outputting vibration reduction. Seat vibration is reduced by controlling the actuator with a control unit. The control by the control unit can be, for example, adaptive control, in which case the reference signal can be the vertical acceleration of the unsprung weight detected by a sensor, and the error signal can be the vertical acceleration of the seat detected by a sensor. The control unit accordingly controls the damping force of the suspension device, etc., to reduce seat vibration. The detection sensor for detecting the error signal is a sensor built into the seat cushion that detects vertical acceleration.

[0003] Patent Literature 2 discloses an in-vehicle biological information detection device that detects biological information related to the biological activity of a person seated in a vehicle seat based on the output of a pressure sensor arranged in the seat. The device arranges multiple pressure sensors along the surface of the seat, and excludes pressure sensors that detect pressure equal to or greater than a first predetermined pressure and pressure sensors that detect pressure equal to or less than a second predetermined pressure that is lower than the first predetermined pressure from the pressure sensors used to detect biological information. An adaptive filter is then created that cancels vibrations due to factors other than biological activity using a vibration reference for detecting vibrations due to factors other than biological activity. The vibration reference is a pressure sensor located in the seat cushion or a pressure sensor excluded from the pressure sensors used to detect biological information.

[0004] Japanese Patent Laid-Open No. 7-186804 Japanese Patent Laid-Open No. 2006-346093

[0005] In the vibration reduction device for a seat described in Patent Document 1, the detection sensor for detecting the error signal is a sensor built into the seat cushion that detects vertical acceleration. If the acceleration sensor is placed inside the seat cushion, the presence of the acceleration sensor will cause discomfort to the occupant, leading to a decrease in seating comfort. Therefore, there is a need for a method of reducing seat vibration without using an acceleration sensor.

[0006] In addition, in the occupant state estimation device including biometric information described in Patent Document 2, the occupant state, such as biometric information, can be obtained using a pressure sensor for acquiring target information such as biometric information and a sensor serving as a vibration reference different from the pressure sensor. However, it is necessary to provide a sensor serving as a vibration reference in addition to the pressure sensor for acquiring target information, which increases the size of the device and causes the wiring to become complicated. Therefore, there is a demand for a device that can be made smaller and has a simpler configuration.

[0007] The present disclosure has been made in light of the above background, and aims to provide, first, a seat vibration reduction device that can reduce seat vibration without using an acceleration sensor, and, second, an occupant state estimation system that can be made smaller and has a simpler configuration.

[0008] a vibration reduction device for a seat, the vibration reduction device comprising: a reference signal detection sensor that detects, as a reference signal, disturbance vibrations in a basic vibration transmission path from a vibration source to a seat in a vehicle; a vibration excitation device that applies reducing vibrations to the seat or to members that constitute a partial vibration transmission path from the reference signal detection sensor to the seat in order to reduce vibrations of the disturbance vibrations that are input to the seat; a pressure sensor that is disposed in a cushion of the seat and outputs a signal corresponding to pressure input via the cushion; and a vibration excitation control device that controls the vibration excitation device, the vibration excitation control device comprising: an error signal calculation unit that, when an occupant is seated in the seat and the vibration excitation device is driven, calculates a vibration component of the pressure sensor as an error signal based on the signal output by the pressure sensor; and an adaptive control unit that performs adaptive control based on the reference signal and the error signal to reduce an influence component of the reference signal included in the error signal, and controls the vibration excitation device based on an output value of the adaptive control.

[0009] a vibration applying device that applies a reducing vibration to a member that constitutes a partial vibration transmission path from the reference signal detection sensor to the seat or to the seat in order to reduce vibration of the disturbance vibration input to the seat; a pressure sensor that is disposed in a cushion of the seat and outputs a signal corresponding to a pressure input via the cushion; an occupant state estimating device that estimates a state of an occupant seated in the seat by performing arithmetic processing based on the signal output by the pressure sensor; and a vibration applying control device that controls the vibration applying device, wherein the vibration applying control device includes: an error signal calculating unit that, when the occupant is seated in the seat and the vibration applying device is driven, calculates a vibration component of the pressure sensor as an error signal based on the signal output by the pressure sensor; and an adaptive control unit that performs adaptive control based on the reference signal and the error signal to reduce an influence component of the reference signal included in the error signal, and controls the vibration applying device based on an output value of the adaptive control.

[0010] According to a first aspect of the present disclosure, a vibration reduction device for a seat can reduce vibrations of a seat by controlling a vibration excitation device through adaptive control. Here, the vibration reduction device for a seat includes a pressure sensor disposed in a cushion of the seat and outputting a signal corresponding to pressure input via the cushion. The error signal used for adaptive control is a vibration component of the pressure sensor calculated based on the signal output by the pressure sensor.

[0011] In other words, instead of using an acceleration sensor placed inside the seat cushion, a pressure sensor is used. Of the pressure input to the pressure sensor via the cushion, the vibration component of the pressure sensor itself is extracted and used as an error signal. Therefore, compared to an acceleration sensor, using a pressure sensor can reduce discomfort felt by the occupant and improve seating comfort.

[0012] As described above, according to the first aspect of the present disclosure, it is possible to provide a vibration reduction device for a seat that can reduce vibrations of a seat without using an acceleration sensor.

[0013] According to a second aspect of the present disclosure, an occupant state estimation system can reduce seat vibrations by controlling a vibration excitation device through adaptive control. Here, the occupant state estimation system includes a pressure sensor disposed in a seat cushion and outputting a signal corresponding to pressure input via the cushion. The error signal used in the adaptive control is a vibration component of the pressure sensor calculated based on the signal output by the pressure sensor.

[0014] In other words, instead of using an acceleration sensor placed inside the seat cushion, a pressure sensor is used. Of the pressure input to the pressure sensor via the cushion, the vibration component of the pressure sensor itself is extracted and used as an error signal. Therefore, compared to an acceleration sensor, using a pressure sensor can reduce discomfort felt by the occupant and improve seating comfort.

[0015] Furthermore, the occupant state estimation system estimates the state of an occupant seated in the seat by performing arithmetic processing based on the signal output by the pressure sensor. That is, the pressure sensor has a function of detecting a signal that serves as a basis for an error signal for reducing seat vibration and a function of detecting a signal used to estimate the state of the seated occupant. In this way, by using a sensor that is used both to estimate the state of the occupant and to reduce seat vibration, the device can be made smaller and its configuration can be simplified.

[0016] As described above, according to the second aspect of the present disclosure, it is possible to provide an occupant state estimation system that can be made smaller and has a simpler configuration.

[0017] FIG. 1 is a diagram showing an overall configuration model of an occupant state estimation system including a vibration reduction device for a seat and an occupant state estimation device in embodiment 1. FIG. 2 is a diagram showing a cross-sectional structure of a pressure sensor in FIG. 1. FIG. 3 is a diagram showing a control block diagram of the vibration reduction device for a seat and showing its relationship with the occupant state estimation device in embodiment 1. FIG. 4 is a diagram showing an overall configuration model of an occupant state estimation system including a vibration reduction device for a seat and an occupant state estimation device in embodiment 2. FIG. 5 is a diagram showing a control block diagram of the vibration reduction device for a seat and showing its relationship with the occupant state estimation device in embodiment 2. FIG. 6 is a diagram showing an overall configuration model of a vibration reduction device for a seat in embodiment 3.

[0018] (Embodiment 1) 1. Basic Configuration of Occupant State Estimation System 100 The basic configuration of the occupant state estimation system 100 in embodiment 1 will be described with reference to Fig. 1. The occupant state estimation system 100 in embodiment 1 includes a seat vibration reduction device 21 configured to reduce vibrations of the seat 4 of the vehicle 1, and an occupant state estimation device 22 configured to estimate the state of an occupant seated in the seat 4 of the vehicle 1.

[0019] The state of the occupant to be estimated includes at least one piece of biological information selected from heart rate information, respiratory information, and the like. Furthermore, the state of the occupant to be estimated may also include the seating posture of the occupant. In this embodiment, the state of the occupant to be estimated includes the heart rate information, respiratory information, and seating posture of the occupant. The seating posture of the occupant includes at least one of the seating posture itself, which indicates the seating position, and a change in the seating posture.

[0020] 2. Basic structural model of vehicle 1 The basic structural model of vehicle 1 will be described with reference to Fig. 1. Fig. 1 shows a structural model showing a part of vehicle 1, and shows the vibration transmission path from a first support member 2 that supports a vibration source to a seat 4.

[0021] For example, the vibration source may be a member to which vibration is input from the road surface. In this case, the first support member 2 is attached to, for example, a wheel (not shown). The first support member 2 may be a knuckle or a suspension frame that constitutes a suspension device of a vehicle. The vibration source may also be an on-board drive device that generates vibration, such as an internal combustion engine or a drive motor. In this case, the first support member 2 is a member attached to the on-board drive device. For example, the first support member 2 may be a subframe that mounts the on-board drive device.

[0022] A second support member 3 is attached to the first support member 2 via a spring element. The second support member 3 constitutes, for example, a chassis frame or a floor member. A seat 4 is attached to the second support member 3 via a spring element. Note that a damper element may be used in addition to the spring element.

[0023] The seat 4 includes a seat frame 11, a seat cushion 12, a seat covering material 13, a back frame 14, a back cushion 15, a back covering material 16, a headrest frame 17, a headrest cushion 18, and a headrest covering material 19. In the seat 4, the seat cushion 12 and the seat covering material 13 may be configured to be fixed to the seat frame 11, or may be configured to be detachably placed on the seat frame 11 like a cushion.

[0024] 3. Functional Description of the Occupant State Estimation System 100 The following describes the functions of the occupant state estimation system 100. As described above, the occupant state estimation system 100 includes the seat vibration reduction device 21 and the occupant state estimation device 22.

[0025] The seat vibration reduction device 21 is configured to reduce vibrations of the seat 4 by applying adaptive control. In particular, in this embodiment, the seat vibration reduction device 21 aims to reduce vibrations of the seat 4 caused by disturbance vibrations. Disturbance vibrations include, for example, vibrations input from the road surface via the wheels. In addition, disturbance vibrations can also be vibrations generated by on-board driving equipment such as an internal combustion engine or various drive motors.

[0026] Here, the state of the occupant, which is the target of estimation by the occupant state estimation device 22, mainly has components of 10 Hz or less, particularly 5 Hz or less. As described above, the state of the occupant, which is the target of estimation, includes the occupant's heart rate information, breathing information, and seating posture of the occupant. The heart rate, which is the target of estimation, is about 0.5 to 3 Hz, and the breathing, which is the target of estimation, is about 0.1 to 1 Hz. Furthermore, the seating posture itself, which indicates the seating position, etc., which is the target of estimation, has components of 10 Hz or less, particularly 5 Hz or less. Furthermore, changes in the seating posture, which is the target of estimation, are also about 10 Hz or less.

[0027] Therefore, it is preferable that the seat vibration reduction device 21 targets a frequency band of 10 Hz or less as the target frequency band for reduction. When the seat vibration reduction device 21 reduces vibrations having a frequency peak between 5 and 10 Hz, it is not only possible to reduce disturbance vibrations in the 5 to 10 Hz frequency band, but it is also effective in reducing disturbance vibrations of 5 Hz or less. Therefore, by reducing disturbance vibrations that affect the frequency band that is the target of estimation by the occupant state estimation device 22, it is possible to acquire information on the target of estimation with high accuracy.

[0028] Furthermore, the vehicle 1 is configured to reduce the transmission of vibrations using anti-vibration devices (not shown) that support each component. For example, if external vibrations are input from the road surface via the wheels, an anti-vibration device or the like disposed in the vibration transmission path from the wheels to the seat 4 is configured to reduce vibrations in a certain frequency band of the external vibrations. Therefore, the frequency bands targeted for vibration reduction by the seat vibration reduction device 21 should preferably be frequency bands excluding frequency bands that can be isolated by anti-vibration devices or the like. Generally, existing anti-vibration devices or the like can reduce vibrations in a frequency band of approximately 10 Hz or higher that are transmitted to the seat 4. From this perspective, the seat vibration reduction device 21 only needs to reduce external vibrations in a frequency band of, for example, 10 Hz or lower.

[0029] In other words, if the seat vibration reduction device 21 can reduce external vibrations in the frequency band of 10 Hz or less, it can improve the comfort of the occupant by reducing vibrations in the frequency band that cannot be reduced by existing vibration-damping devices, and can also improve the accuracy of the target estimated by the occupant state estimation device 22.

[0030] 4. Details of Components of the Occupant State Estimation System 100 Details of each component of the occupant state estimation system 100 will be described with reference to Fig. 1. The seat vibration reduction device 21 constituting the occupant state estimation system 100 includes a reference signal detection sensor 31, a vibration applying device 32, a pressure sensor 33, and a vibration applying control device 34.

[0031] The reference signal detection sensor 31 detects, as a reference signal, disturbance vibrations in the basic vibration transmission path (reference numerals 2 → 3 → 4 in FIG. 1 ) from a vibration source to the seat 4 in the vehicle 1. For example, the reference signal detection sensor 31 is attached to the first support member 2 located on the basic vibration transmission path, and detects disturbance vibrations of the first support member 2. An acceleration sensor, for example, can be used as the reference signal detection sensor 31.

[0032] When vibration is input from the road surface to the wheel, the reference signal detection sensor 31 detects, as a reference signal, disturbance vibration in the basic vibration transmission path from the wheel to the seat 4. For example, if the first support member 2 is a knuckle or a suspension frame, the reference signal detection sensor 31 detects vibration of the knuckle or the suspension frame as a reference signal.

[0033] Furthermore, when the in-vehicle drive equipment generates vibrations, the reference signal detection sensor 31 may be configured to detect, as a reference signal, disturbance vibrations in the basic vibration transmission path from the in-vehicle drive equipment to the seat 4. For example, when the first support member 2 is a subframe, the reference signal detection sensor 31 detects vibrations of the subframe as a reference signal.

[0034] Furthermore, the reference signal detection sensor 31 may be configured to detect, as a reference signal, a component of the disturbance vibration of, for example, 10 Hz or less. In this case, the reference signal detection sensor 31 is configured to include a low-pass filter with a cutoff frequency of 10 Hz.

[0035] In order to reduce the vibrations of the disturbance vibrations input to the seat 4, the vibration excitation device 32 applies a reduction vibration to the seat 4 or to the members constituting the partial vibration transmission path from the reference signal detection sensor 31 to the seat 4. Here, the partial vibration transmission path constitutes a part of the fundamental vibration transmission path. While the fundamental vibration transmission path is the vibration transmission path from the vibration source to the seat 4, the partial vibration transmission path is the vibration transmission path from the reference signal detection sensor 31 to the seat 4.

[0036] In this embodiment, the vibration device 32 is attached to the seat frame 11 of the seat 4. That is, the vibration device 32 reduces the vibration of the seat 4 by applying a reduction vibration to the seat frame 11 of the seat 4, the reduction vibration being in the opposite phase to the vibration of the seat frame 11 of the seat 4.

[0037] The vibration generator 32 may be an active vibration generator using an actuator such as a voice coil motor (VCS) or a solenoid coil. The vibration generator 32 may also have a spring-mass configuration. In this case, the first support member 2 can be vibrated by actively vibrating the mass. The spring used here may be a viscoelastic body such as rubber or elastomer, or an elastic body such as a leaf spring or coil spring.

[0038] The pressure sensor 33 is disposed in the seat cushion 12 of the seat 4. More specifically, the pressure sensor 33 is disposed in the middle position of the seat cushion 12 in the vertical direction, sandwiched between the upper and lower cushions. The pressure sensor 33 outputs a signal corresponding to the pressure input via the seat cushion 12. The pressure sensor 33 may be disposed in the back cushion 15 instead of the seat cushion 12.

[0039] The pressure sensor 33 is configured so as not to cause an occupant seated in the seat 4 to feel uncomfortable due to the presence of the pressure sensor 33. For example, the pressure sensor 33 is formed in a sheet (film) shape and is flexible. The pressure sensor 33 may be configured to be stretchable in the planar direction, or may not be stretchable. The pressure sensor 33 may be, for example, an electrostatic sensor or a piezoelectric sensor.

[0040] The pressure sensor 33 is configured to detect a signal used to estimate the occupant's biological information. For example, the pressure sensor 33 is configured to detect pressure transmitted through the seat cushion 12 due to pulsation of the occupant's femoral artery. Here, the pulsation of the femoral artery includes movements corresponding to the heartbeat and breathing, which are biological information. Therefore, the pressure sensor 33 is configured to detect the pulsation of the femoral artery as a signal used to estimate the biological information.

[0041] Furthermore, in this embodiment, the pressure sensor 33 is configured to detect a signal used to estimate the posture of the occupant. Changes in the seating position and seating posture of the occupant correspond to the position of the thighs and changes in the thigh position of the occupant. Therefore, the pressure sensor 33 is configured to detect the position of the thighs and changes in the thigh position of the occupant as a signal used to estimate the posture of the occupant.

[0042] The vibration control device 34 controls the vibration device 32. The vibration control device 34 controls the vibration device 32 by applying adaptive control based on the reference signal detected by the reference signal detection sensor 31 and the signal corresponding to the pressure output by the pressure sensor 33. Specifically, the vibration control device 34 uses the vibration component of the pressure sensor calculated from the signal corresponding to the pressure output by the pressure sensor 33 as an error signal, and performs adaptive control to reduce the influence component of the reference signal included in the error signal.

[0043] Therefore, the control by the vibration control device 34 suppresses the transmission of disturbance vibrations to the seat 4. For example, when vibrations are input from the road surface to the wheels, the seat 4 is in a state where the influence of the vibrations input from the road surface is reduced.

[0044] Instead of configuring the reference signal detection sensor 31 to include a low-pass filter with a cutoff frequency of 10 Hz, the vibration control device 34 may be configured as follows: The vibration control device 34 may be configured to include a low-pass filter with a cutoff frequency of 10 Hz, and components of the reference signal detected by the reference signal detection sensor 31 that are 10 Hz or less may be extracted.

[0045] The occupant state estimation device 22 constituting the occupant state estimation system 100 estimates the state of an occupant seated in the seat 4 by performing arithmetic processing based on a signal output by the pressure sensor 33. As described above, the pressure sensor 33 is disposed in the seat cushion 12 and outputs a signal corresponding to the pressure input via the seat cushion 12. Furthermore, the pressure sensor 33 is configured to detect a signal used to estimate the occupant's biological information. In addition, the pressure sensor 33 is configured to detect a signal used to estimate the occupant's posture.

[0046] The occupant state estimation device 22 is configured to estimate biological information of the occupant based on the signal detected by the pressure sensor 33. Furthermore, the occupant state estimation device 22 is configured to estimate the posture of the occupant based on the signal detected by the pressure sensor 33.

[0047] The occupant state estimation device 22 can estimate the biometric information and posture of the occupant by applying the techniques disclosed in, for example, Japanese Patent Application Laid-Open No. 2018-023618, Japanese Patent Application Laid-Open No. 2017-176499, and Japanese Patent Application Laid-Open No. 2017-176498.

[0048] As described above, the pressure sensor 33 is used for the adaptive control in the vibration control device 34, and is also used for the calculation processing by the occupant state estimation device 22. In this way, the pressure sensor 33 is used for both the adaptive control in the vibration control device 34 and the calculation processing by the occupant state estimation device 22.

[0049] However, the adaptive control in the vibration control device 34 and the arithmetic processing by the occupant state estimation device 22 can operate independently. That is, the arithmetic processing by the occupant state estimation device 22 can be executed while the adaptive control in the vibration control device 34 is being executed. Furthermore, it is also possible to execute the adaptive control in the vibration control device 34 and stop the arithmetic processing by the occupant state estimation device 22. The reverse is also possible.

[0050] 5. Structure of Pressure Sensor 33 The structure of the pressure sensor 33 will be described with reference to Fig. 2. The pressure sensor 33 will be described as being an electrostatic sensor. The pressure sensor 33 comprises a sensor main body 41, a power supply circuit 42, and a detection circuit 43. The power supply circuit 42 and the detection circuit 43 may be disposed inside the seat cushion 12, as with the sensor main body 41, or may be disposed outside the seat cushion 12.

[0051] As shown in Figure 2, the sensor body 41 of the pressure sensor 33 is formed in a sheet (film) shape. The sensor body 41 detects pressure applied from both sides. The power supply circuit 42 applies a voltage to the sensor body 41 for pressure detection. The detection circuit 43 detects a voltage corresponding to the capacitance detected by the sensor body 41.

[0052] The sensor body 41 of the pressure sensor 33 includes an insulator sheet 51, a first electrode sheet 52, a second electrode sheet 53, a first insulator sheet 54, a first shield electrode 55, a second insulator sheet 56, and a second shield electrode 57. Although it is possible to configure the sensor without the first shield electrode 55 and the second shield electrode 57, a configuration including these electrodes allows for more accurate detection of a desired signal.

[0053] The insulator sheet 51 has insulating properties and constitutes a dielectric in the electrostatic sensor. The insulator sheet 51 is flexible. Furthermore, the insulator sheet 51 is formed to be compressible and deformable in the direction normal to the surface. The insulator sheet 51 is formed to be compressible and deformable in response to the pressure applied to the sensor body 41 of the pressure sensor 33. The insulator sheet 51 is formed of, for example, elastomer or rubber.

[0054] The first electrode sheet 52 is disposed in contact with the first surface (the upper surface in FIG. 2 ) of the insulator sheet 51. The first electrode sheet 52 may be disposed by adhering to the first surface of the insulator sheet 51, or may be disposed without adhering. The first electrode sheet 52 is flexible. The first electrode sheet 52 may be a metal sheet without through holes, a metal sheet with multiple through holes, a conductive cloth, or the like.

[0055] The second electrode sheet 53 is disposed in contact with the second surface (the lower surface in FIG. 2 ) of the insulator sheet 51. The second electrode sheet 53 may be disposed by adhering to the second surface of the insulator sheet 51, or may be disposed without adhering. The second electrode sheet 53 is flexible. The second electrode sheet 53 may be a metal sheet without through holes, a metal sheet with multiple through holes, a conductive cloth, or the like.

[0056] As described above, when pressure is applied from the seat cushion 12 to both sides of the sensor body 41 of the pressure sensor 33, the insulating sheet 51 is compressed and deformed. The compressive deformation of the insulating sheet 51 changes the distance between the first electrode sheet 52 and the second electrode sheet 53. Therefore, the capacitance between the first electrode sheet 52 and the second electrode sheet 53 changes. The detection circuit 43 of the pressure sensor 33 detects the capacitance between the first electrode sheet 52 and the second electrode sheet 53. This capacitance corresponds to the pressure input via the seat cushion 12.

[0057] The first insulator sheet 54 is disposed in contact with the outer surface (upper surface in FIG. 2 ) of the first electrode sheet 52, i.e., the surface of the first electrode sheet 52 opposite the insulator sheet 51. The first insulator sheet 54 may be disposed by being adhered to the first electrode sheet 52, or may be disposed without being adhered to the first electrode sheet 52. The first insulator sheet 54 is flexible. The first insulator sheet 54 may be formed from the same type of elastomer or rubber as the insulator sheet 51. Alternatively, the first insulator sheet 54 may be formed from a resin film.

[0058] The first insulator sheet 54 is formed thinner than the insulator sheet 51 and is formed so as to be less susceptible to compressive deformation than the insulator sheet 51. The first insulator sheet 54 functions to protect the first electrode sheet 52. Furthermore, the first insulator sheet 54 functions to insulate the first electrode sheet 52 from the first shield electrode 55.

[0059] The first shield electrode 55 is disposed in contact with the outer surface (upper surface in FIG. 2 ) of the first insulator sheet 54, i.e., the surface opposite the first electrode sheet 52. The first shield electrode 55 may be disposed by being adhered to the first insulator sheet 54, or may be disposed without being adhered. The first shield electrode 55 is flexible. The first shield electrode 55 may be formed of a metal sheet, a conductive cloth, or the like. The first shield electrode 55 has the function of reducing the influence of external conductors on the first electrode sheet 52. For example, a voltage having the same potential as the first electrode sheet 52 or a ground potential may be applied to the first shield electrode 55.

[0060] The second insulator sheet 56 is disposed in contact with the outer surface (lower surface in FIG. 2 ) of the second electrode sheet 53, i.e., the surface of the second electrode sheet 53 opposite the insulator sheet 51. The second insulator sheet 56 may be disposed by being adhered to the second electrode sheet 53, or may be disposed without being adhered to the second electrode sheet 53. The second insulator sheet 56 is flexible. The second insulator sheet 56 may be formed from the same type of elastomer or rubber as the insulator sheet 51. The second insulator sheet 56 may also be formed from a resin film.

[0061] The second insulator sheet 56 is formed thinner than the insulator sheet 51 and is formed so as to be less susceptible to compressive deformation than the insulator sheet 51. The second insulator sheet 56 functions to protect the second electrode sheet 53. Furthermore, the second insulator sheet 56 functions to insulate the second electrode sheet 53 from the second shield electrode 57.

[0062] The second shield electrode 57 is disposed in contact with the outer surface (lower surface in FIG. 2 ) of the second insulator sheet 56, i.e., the surface opposite the second electrode sheet 53. The second shield electrode 57 may be disposed by being adhered to the second insulator sheet 56, or may be disposed without being adhered. The second shield electrode 57 is flexible. The second shield electrode 57 may be formed of a metal sheet, a conductive cloth, or the like. The second shield electrode 57 has the function of reducing the influence of external conductors on the second electrode sheet 53. For example, a voltage having the same potential as the second electrode sheet 53 or a ground potential may be applied to the second shield electrode 57.

[0063] 6. Configuration Related to Adaptive Control by Seat Vibration Reduction Device 21 The configuration related to adaptive control by the seat vibration reduction device 21 will be described with reference to Fig. 3. As described above, the seat vibration reduction device 21 includes the reference signal detection sensor 31, the vibration device 32, the pressure sensor 33, and the vibration control device 34. The vibration control device 34 includes an error signal calculation unit 61 and an adaptive control unit 62.

[0064] Vibration (disturbance vibration) of the vibration source is transmitted via the basic vibration transmission path (transfer function W1) from the vibration source to position P1, which is the seat frame 11 of the seat 4. Then, vibration of the seat 4, which has the occupant as its mass, is combined with the vibration of the seat frame 11.

[0065] Furthermore, the vibration device 32 is disposed on the seat frame 11. Therefore, when the vibration device 32 is driven, vibrations generated by the vibration device 32 are combined at position P1, which is the seat frame 11. The vibration device 32 generates vibrations at position P1, which is the seat frame 11, to cancel out vibrations of 10 Hz or less that are included in disturbance vibrations caused by the vibration source. Therefore, ideally, at position P1, the vibrations of 10 Hz or less that are included in disturbance vibrations caused by the vibration source are canceled out.

[0066] The reference signal detection sensor 31 detects vibrations of the first support member 2 located on the fundamental vibration transmission path. However, the reference signal detection sensor 31 may output only components of the disturbance vibrations of the first support member 2 that have passed through a low-pass filter with a cutoff frequency of 10 Hz. In this case, the reference signal detection sensor 31 outputs components of the disturbance vibrations of the first support member 2 that are 10 Hz or lower. Note that instead of providing a low-pass filter in the reference signal detection sensor 31, a low-pass filter may be provided in the vibration control device 34, and the vibration control device 34 may extract components of 10 Hz or lower.

[0067] The pressure sensor 33 is disposed within the seat cushion 12. Vibrations at position P1, which is the seat frame 11, are transmitted to position P2 of the pressure sensor 33 via a transfer function W2 of the seat cushion 12. Furthermore, since pressure fluctuations due to the state of the occupant are input to the seat cushion 12, the pressure fluctuations due to the state of the occupant are combined at position P2 of the pressure sensor 33. Therefore, the pressure sensor 33 detects vibrations resulting from the combined pressure fluctuations due to the state of the occupant in addition to the vibrations at position P1, which is the seat frame 11. The signal detected by the pressure sensor 33 is output to the occupant state estimation device 22 and is used to estimate the state of the occupant.

[0068] The error signal calculation unit 61 of the vibration control device 34 acquires the signal output by the pressure sensor 33 when an occupant is seated in the seat 4 and the vibration device 32 is activated. The error signal calculation unit 61 calculates the vibration component of the pressure sensor 33 as an error signal based on the signal output by the pressure sensor 33. As described above, the sensor body 41 of the pressure sensor 33 outputs a signal corresponding to the pressure input via the seat cushion 12. Therefore, the error signal calculation unit 61 calculates the vibration component of the pressure sensor 33, i.e., a signal corresponding to the acceleration of the pressure sensor 33, as an error signal from the signal corresponding to the pressure detected by the pressure sensor 33.

[0069] In particular, in this embodiment, the sensor body 41 of the pressure sensor 33 is an electrostatic sensor, and the insulating sheet 51 is configured to be compressively deformable. Therefore, when the sensor body 41 of the pressure sensor 33 inputs pressure via the seat cushion 12, the thickness of the insulating sheet 51 changes. As a result, the distance between the first electrode sheet 52 and the second electrode sheet 53 that make up the sensor body 41 changes. This changes the charge between the first electrode sheet 52 and the second electrode sheet 53.

[0070] The detection circuit 43 of the pressure sensor 33 detects the capacitance between the first electrode sheet 52 and the second electrode sheet 53 of the sensor body 41, which corresponds to the change in the distance between the first electrode sheet 52 and the second electrode sheet 53. In other words, the detection circuit 43 detects a change in charge between the first electrode sheet 52 and the second electrode sheet 53. This change in charge can be regarded as a change in acceleration input to the pressure sensor 33. Therefore, the error signal calculation unit 61 can calculate, as an error signal, a vibration component of the pressure sensor 33, i.e., a signal corresponding to the acceleration of the pressure sensor 33, from a signal corresponding to the pressure detected by the pressure sensor 33.

[0071] The adaptive control unit 62 of the vibration control device 34 acquires the reference signal output by the reference signal detection sensor 31 and the error signal calculated by the error signal calculation unit 61. Based on the reference signal and the error signal, the adaptive control unit 62 performs adaptive control to reduce the influence component of the reference signal included in the error signal, and controls the vibration exciter 32 based on the output value of the adaptive control. Therefore, the vibration exciter 32 generates vibrations at position P1, which is the seat frame 11, to cancel out vibrations of 10 Hz or less included in the disturbance vibrations caused by the vibration source.

[0072] As described above, the vibration device 32 applies vibrations to the position P1 of the seat frame 11 to cancel out vibrations of 10 Hz or less contained in the disturbance vibrations caused by the vibration source. The vibration device 32 is controlled based on the output value of the adaptive control unit 62, so ideally, at position P1, the vibrations of 10 Hz or less contained in the disturbance vibrations caused by the vibration source are canceled out.

[0073] 7. Effects According to this embodiment, the seat vibration reduction device 21 can reduce vibrations of the seat 4 by controlling the vibrator 32 through adaptive control. Here, the seat vibration reduction device 21 is provided with a pressure sensor 33 that is disposed in the seat cushion 12 of the seat 4 and outputs a signal corresponding to the pressure input via the seat cushion 12. The error signal used for adaptive control is the vibration component of the pressure sensor 33 that is calculated based on the signal output by the pressure sensor 33.

[0074] That is, instead of using an acceleration sensor disposed in the seat cushion 12 of the seat 4, the pressure sensor 33 is used. Of the pressure input to the pressure sensor 33 via the seat cushion 12, the vibration component of the pressure sensor 33 itself is extracted and used as an error signal. Therefore, compared to an acceleration sensor, using the pressure sensor 33 can prevent the occupant from feeling uncomfortable, improving sitting comfort.

[0075] Furthermore, the occupant state estimation device 22 estimates the state of an occupant seated in the seat 4 by performing arithmetic processing based on the signal output by the pressure sensor 33. In other words, the pressure sensor 33 has a function of detecting a signal that serves as the basis of an error signal for reducing vibration of the seat 4, and a function of detecting a signal used to estimate the state of the seated occupant. In this way, by using a single sensor to both estimate the state of the occupant and reduce vibration of the seat 4, the device can be made smaller and its configuration can be simplified.

[0076] In this embodiment, the pressure sensor 33 is an electrostatic sensor, and the occupant state estimation device 22 estimates the occupant's biological information as the occupant's state, thereby making it possible to estimate the occupant's biological information with high accuracy.

[0077] In this embodiment, the pressure sensor 33 is an electrostatic sensor, and the occupant state estimation device 22 estimates the occupant's biometric information and posture as the occupant's state, thereby enabling the occupant's biometric information and posture to be estimated with high accuracy.

[0078] In this embodiment, when vibrations are input from the road surface to the wheels, the reference signal detection sensor 31 detects, as a reference signal, disturbance vibrations in the basic vibration transmission path from the wheels to the seat 4. In this case, the seat 4 can be made less susceptible to disturbance vibrations input from the road surface. Furthermore, even if disturbance vibrations are input from the road surface, the state of the occupant can be estimated with high accuracy.

[0079] In this embodiment, when the in-vehicle drive equipment generates vibrations, the reference signal detection sensor 31 detects, as a reference signal, disturbance vibrations in the basic vibration transmission path from the in-vehicle drive equipment to the seat 4. In this case, the seat 4 can be made less susceptible to disturbance vibrations generated by the in-vehicle drive equipment. Furthermore, even if the in-vehicle drive equipment generates disturbance vibrations, the state of the occupant can be estimated with high accuracy.

[0080] In this embodiment, the reference signal detection sensor 31 detects components of disturbance vibrations of 10 Hz or less as a reference signal. This allows the occupant's biological information to be estimated with high accuracy as the occupant's condition. Note that the same effect can be achieved even when the vibration control device 34 extracts components of 10 Hz or less from the reference signal detected by the reference signal detection sensor 31.

[0081] In this embodiment, the reference signal detection sensor 31 is attached to the chassis frame (first support member 2) of the vehicle, the suspension device (first support member 2) of the vehicle, the subframe (first support member 2) on which the vehicle's on-board drive equipment is mounted, or the floor member (second support member 3) on which the vehicle seat 4 is mounted, thereby achieving the above-mentioned effects.

[0082] An occupant state estimation system 200 according to a second embodiment will be described with reference to Fig. 4. Note that, among the reference symbols used in the second embodiment, the same reference symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified.

[0083] In this embodiment, the vibration device 232 is attached to the second support member 3. That is, the vibration device 232 reduces the vibration of the seat 4 by applying a reduction vibration to the second support member 3 that is in the opposite phase to the vibration of the second support member 3.

[0084] The configuration related to adaptive control by the seat vibration reduction device 21 will be described with reference to Fig. 5. The seat vibration reduction device 21 includes a reference signal detection sensor 31, a vibration device 232, a pressure sensor 33, and a vibration control device 34. The vibration control device 34 includes an error signal calculation unit 61 and an adaptive control unit 62.

[0085] Vibration (disturbance vibration) of the vibration source is transmitted via a fundamental vibration transmission path (transfer functions W11, W12) from the vibration source to position P1, which is the seat frame 11 of the seat 4. Of the fundamental vibration transmission paths, vibration of the vibration source is transmitted via a vibration transmission path (transfer function W11) from the vibration source to position P3, which is the second support member 3.

[0086] Furthermore, the vibration exciter 232 is disposed on the second support member 3. Therefore, when the vibration exciter 232 is driven, vibrations generated by the vibration exciter 232 are combined at position P3, which is the second support member 3. The vibration exciter 232 generates vibrations to cancel out vibrations of components of 10 Hz or less contained in disturbance vibrations caused by the vibration source at position P3, which is the second support member 3. Therefore, ideally, at position P3, vibrations of components of 10 Hz or less contained in disturbance vibrations caused by the vibration source are canceled out.

[0087] The vibration at position P3 is transmitted via a vibration transmission path (transfer function W12) from position P3, which is the second support member 3, to position P1, which is the seat frame 11. The vibration of the seat 4, which has the occupant as its mass, is then combined with the vibration of the seat frame 11.

[0088] Other configurations are the same as those of embodiment 1. This configuration also provides the same effects as those of embodiment 1.

[0089] Third Embodiment A vibration reduction device for a seat 300 according to a third embodiment will be described with reference to Fig. 6. In the first embodiment, the occupant state estimation system 100 includes the vibration reduction device for a seat 21 and the occupant state estimation device 22.

[0090] In this embodiment, a vibration reduction device for a seat 300 includes a reference signal detection sensor 31, a vibration device 32, a pressure sensor 33, a vibration control device 34, and an occupant state estimation device 22. The first and third embodiments are essentially the same except for their different frameworks. Therefore, the present embodiment also achieves the same effects as the first embodiment.

[0091] (Others) As in the above embodiment, the vibration device 32, 232 may be disposed on the first support member 2 in addition to the seat frame 11 and the second support member 3. Furthermore, as in the above embodiment, the reference signal detection sensor 31 may be disposed on the second support member 3. In this case, however, the vibration device 32, 232 will be disposed on the second support member 3 or the seat frame 11.

Claims

1. A vehicle (1) comprising: a reference signal detection sensor (31) that detects, as a reference signal, disturbance vibrations in a basic vibration transmission path from a vibration source to a seat (4); a vibration excitation device (32, 232) that applies reducing vibrations to the seat or to a member that constitutes a partial vibration transmission path from the reference signal detection sensor to the seat in order to reduce vibrations of the disturbance vibrations input to the seat; a pressure sensor (33) that is disposed in a cushion (12) of the seat and outputs a signal corresponding to pressure input via the cushion; and a vibration excitation control device (34) that controls the vibration excitation device, wherein the vibration excitation control device comprises: an error signal calculation unit (61) that calculates, as an error signal, a vibration component of the pressure sensor based on the signal output by the pressure sensor when an occupant is seated in the seat and the vibration excitation device is activated; an adaptive control unit (62) that performs adaptive control based on the reference signal and the error signal to reduce the influence component of the reference signal contained in the error signal, and controls the vibration device based on an output value of the adaptive control.

2. A vibration reduction device for a seat as described in claim 1, further comprising an occupant state estimation device (22) that estimates the state of the occupant seated in the seat by performing arithmetic processing based on the signal output by the pressure sensor.

3. A vibration reduction device for a seat as described in claim 2, wherein the pressure sensor is an electrostatic sensor, and the occupant state estimation device estimates the occupant's state based on biological information of the occupant.

4. A vibration reduction device for a seat as described in claim 2, wherein the pressure sensor is an electrostatic sensor, and the occupant state estimation device estimates the occupant's state based on the occupant's biometric information and the occupant's posture.

5. A vibration reduction device for a seat as described in any one of claims 1 to 4, wherein the reference signal detection sensor detects the disturbance vibration in the basic vibration transmission path from the wheel to the seat as the reference signal when vibration is input from the road surface to the wheel.

6. A vibration reduction device for a seat as described in any one of claims 1 to 4, wherein the reference signal detection sensor detects the disturbance vibration in the basic vibration transmission path from the vehicle-mounted driving equipment to the seat as the reference signal when the vehicle-mounted driving equipment generates vibration.

7. A vibration reduction device for a seat according to any one of claims 1 to 4, wherein the reference signal detection sensor detects a component of the disturbance vibration that is 10 Hz or less as the reference signal.

8. A vibration reduction device for a seat as described in any one of claims 1 to 4, wherein the reference signal detection sensor is attached to a chassis frame of the vehicle, a suspension device of the vehicle, a subframe that mounts the vehicle's onboard drive equipment, or a floor member for mounting the vehicle's seat.

9. A vehicle (1) comprising: a reference signal detection sensor (31) that detects, as a reference signal, disturbance vibrations in a basic vibration transmission path from a vibration source to a seat (4); a vibration excitation device (32, 232) that applies reducing vibrations to the seat or to a member that constitutes a partial vibration transmission path from the reference signal detection sensor to the seat in order to reduce vibrations of the disturbance vibrations input to the seat; a pressure sensor (33) that is disposed in a cushion (12) of the seat and outputs a signal corresponding to pressure input via the cushion; an occupant state estimation device (22) that estimates the state of an occupant seated in the seat by performing arithmetic processing based on the signal output by the pressure sensor; and a vibration excitation control device (34) that controls the vibration excitation device, wherein the vibration excitation control device comprises: an error signal calculation unit (61) that calculates, as an error signal, a vibration component of the pressure sensor based on the signal output by the pressure sensor when the occupant is seated in the seat and the vibration excitation device is activated; an adaptive control unit (62) that performs adaptive control based on the reference signal and the error signal so as to reduce an influence component of the reference signal contained in the error signal, and controls the vibration device based on an output value of the adaptive control.

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