SEAT OCCUPANCY DETECTION WITH ACCELERATION SIGNAL

Abstract

The invention relates to a system for seat occupancy detection, comprising a vehicle seat for a driver with an upper part and at least one suspension-damper system, wherein an acceleration sensor is arranged on the upper part and is designed to detect a characteristic of an acceleration of the upper part as a function of a time, an evaluation unit being provided which is designed to generate an evaluation of the characteristic of the acceleration and optionally to transmit a signal to a higher-level control unit, the evaluation unit also being designed to assign the evaluation to one of several states, wherein the states are selected from a group comprising an occupied state and an unoccupied state of the vehicle seat.

Claims

1. A system for seat occupancy detection, comprising a vehicle seat for a driver with an upper part and at least one suspension-damper system, an acceleration sensor being arranged on the upper part and designed to detect a characteristic of an acceleration of the upper part as a function of a time, wherein an evaluation unit is provided which is designed to create an evaluation of the characteristic of the acceleration and optionally to transmit a signal to a higher-level control unit, characterized in that the evaluation unit is also designed to assign the evaluation to one of several states, the states being selected from a group comprising an occupied state and an unoccupied state of the vehicle seat.

2. The system according to claim 1, wherein the evaluation unit is further configured to assign the evaluation to one of several processes, the processes being selected from a group which comprises occupying the vehicle seat and leaving the vehicle seat by the driver.

3. The system according to claim 1, wherein the evaluation comprises an amplitude spectrum of the characteristic of the acceleration, the evaluation unit also being designed to compare the amplitude spectrum with at least one temporally preceding amplitude spectrum and/or with at least one predetermined amplitude spectrum.

4. The system according to claim 3, wherein the evaluation unit is also designed to detect a deviation between a first frequency which can be assigned to a maximum peak of the determined amplitude spectrum and a second frequency which can be assigned to a maximum peak of the compared amplitude spectrum.

5. The system according to claim 3, wherein the evaluation unit is further configured to detect a deviation of a number of peaks and/or frequencies assignable to these peaks between the determined amplitude spectrum and the compared amplitude spectrum.

6. The system according to claim 1, wherein the evaluation unit is further configured to evaluate the characteristic of the acceleration and compare it with at least one previous characteristic and/or with at least one predetermined characteristic.

7. A method for seat occupancy detection within a system, the system comprising a vehicle seat for a driver with an upper part and at least one suspension-damper system, an acceleration sensor arranged on the upper part and an evaluation unit, comprising the following steps: detecting a characteristic of an acceleration of the upper part as a function of a time by the acceleration sensor, creating an evaluation of the characteristic of the acceleration by the evaluation unit, comparing the evaluation with the evaluation of a chronologically preceding characteristic or with a predetermined evaluation, assignment of the evaluation to one of several processes, the processes being selected from a group which comprises occupying the vehicle seat and leaving the vehicle seat by the driver, or assignment of the evaluation to one of several states, the states being selected from a group which comprises an occupied state and an unoccupied state of the vehicle seat, repetition of steps to up to a predefinable termination criterion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further advantages, goals and features of the present invention are explained with reference to the accompanying drawings and the following description, in which different embodiments of the vehicle seat according to the invention are shown and described by way of example. In the drawings:

[0046] FIG. 1a shows a schematic representation of a vehicle with a vehicle seat and an actuator;

[0047] FIG. 1b shows a schematic representation of a system according to the invention;

[0048] FIG. 2 shows an example of a characteristic a(t);

[0049] FIG. 3a, 3c show characteristics a(t) of the process sitting;

[0050] FIG. 3b shows a representation of one of the characteristics from FIG. 3a together with the associated envelope curve;

[0051] FIG. 4a, 4c show characteristics a(t) of the leaving process;

[0052] FIG. 4b shows a representation of one of the characteristics from FIG. 4a together with the associated envelope curve;

[0053] FIG. 5 shows an amplitude spectrum a(f) resulting from the characteristic of FIG. 2;

[0054] FIG. 6 shows a preferred sequence of the method according to the invention.

DETAILED DESCRIPTION

[0055] According to FIG. 1a, a vehicle M with a vehicle seat 1 and an actuator 20 is shown in a highly simplified manner. For example, the vehicle M is a combine harvester and the actuator 20 is the associated mower.

[0056] FIG. 1b shows a system (S) for recognizing seat occupancy comprising the vehicle seat (1) for a driver (F) with an upper part (2) and a suspension-damper system (5). In the present case, the upper part (2) is resiliently supported relative to the lower part (3) of the vehicle seat (1) by means of a scissor-type frame 4, which is supported, for example, by suspension elements and damping elements of the suspension-damper system (5), which are not shown. It would also be conceivable that the scissors-type frame (4) is dispensed with and the suspension-damper system (5) is formed by means of the upholstery part (6) of the upper part (2).

[0057] For illustration purposes, a Cartesian coordinate system with the axes 1x (longitudinal direction of the seat), 1y (width direction of the seat) and 1z (height direction of the seat) is shown.

[0058] An acceleration sensor (10) is arranged on the upper part 2, in this case on the upholstery part (6) of the upper part 2, which is designed to detect a characteristic of an acceleration (a) of the upper part (2) as a function of a time (t). An example of a resulting configuration is shown as diagram 30. In the present case, this acceleration sensor (10) sends the detected characteristic to an evaluation unit (11).

[0059] In the present case, the evaluation unit (11) is designed to produce an evaluation (a) of the characteristic (a(t)) of the acceleration (a) and to send a signal to a higher-level control unit (CU). In the present case, the evaluation is designed as an amplitude spectrum a(f) and is shown as an example in the diagram 40.

[0060] The evaluation unit (11) is now designed to assign the evaluation (a) to one of several states (J1, J2), the states (J1, J2) being selected from a group which comprises an occupied state (J1) and an unoccupied state (J2) of the vehicle seat (1). For example, the evaluation unit recognizes in the present case that the vehicle seat 1 is occupied by the driver F, who has a mass of 60 kg.

[0061] On the basis of the signals from the evaluation unit 11, the control unit (CU) can decide whether or not it sends a signal to the actuator 20 that changes its state. In the present case, the driver F is on the vehicle seat 1 and thus outside the danger zone of the actuator 20, so that, for example, there is no signal from the control unit (CU) to the actuator 20, or a signal with which the actuator 20 can be put into operation.

[0062] FIG. 2 now shows a vibration characteristic a(t) with three temporally different sections, which can be assigned to the states J2 or J1 and the process V1 after an evaluation. For example, the first section is to be assigned to state J2, that is to say the unoccupied vehicle seat. The seat 1 vibrates essentially periodically with a certain frequency f2 and an amplitude A2. In the third section, the seat 1 is occupied by a driver F, so that the seat 1 vibrates with an amplitude A1 and with a periodic frequency f1. It is important here that A1 is less than A2, which can be immediately read from the diagram, and that f1 is smaller than f2 (see also FIG. 5 here for evaluation).

[0063] The middle section now has a maximum peak 40 and, in chronological order, several smaller peaks 41-44. Based on this specific pattern, the evaluation unit 11 is now able to assign this middle section to the process V1, that is to say the sitting of a driver F in the seat 1.

[0064] FIGS. 3a and 4a now show several detected characteristics ai(t) and aj(t), as they occur in each case when sitting (FIG. 3a) or when leaving (FIG. 4a). FIGS. 3b and 4b each show an a1(t), a10(t) of these characteristics ai(t) and aj(t) as well as the envelope curves h1 and h3 thereof for the maximum values (positive amplitudes) and h3 and h4 for the minimum values (negative amplitudes).

[0065] It should be noted that the process V1 leads to a much more restless vibration characteristic: The mass of the driver F vibrates for a long time, so that the steady state is only reached after a certain time interval. The positive peaks 40, 42, 44 relative to one another and the negative peaks 41, 43, 45 relative to one another exhibit a relatively large difference. The two envelope curves h1 and h2 are not designed to fall or rise evenly.

[0066] It should also be noted that the process V2 leads to a much smoother vibration curve: As soon as the mass of the driver F has left the seat 1, the seat swings quickly in terms of time to state J2. The positive peaks 50, 52, 54, 56, 58, 60 relative to one another and the negative peaks 51, 53, 55, 57, 59 relative to one another exhibit a smaller difference. From the maximum peak 50 and the peak 51, the two envelope curves h3 and h4 are essentially falling (h3) or rising (h4).

[0067] FIGS. 3c and 4c again show characteristics of processes V1 (FIG. 3c) and V2 (FIG. 4c).

[0068] Using an FFT, an amplitude spectrum a(f) (without taking into account section V1) was calculated from the characteristic of the curve in accordance with FIG. 2 and represented in accordance with FIG. 5. It can be seen that several peaks accumulate around two frequencies f1 and f2. This again clearly shows that the frequency f2 of the unoccupied seat differs significantly from the frequency f1 of the occupied seat; a comparison of the two by the evaluation unit 11 can thus serve as a basis for making a decision for the assignment of the state.

[0069] FIG. 6 shows a preferred characteristic of the method 100 according to the invention for seat occupancy detection within a system (S), the system (S) comprising a vehicle seat (1) for a driver (F) with an upper part (2) and at least one suspension-damper system (5), an acceleration sensor (10) arranged on the upper part (2), and an evaluation unit (11). After the engine has started, the embodiment of the method 100 shown comprises the following steps:

[0070] (101) detecting a characteristic (a(t)) of an acceleration (a) of the upper part (2) as a function of a time (t) by the acceleration sensor (10),

[0071] (102) creating an evaluation (a) of the characteristic (a(t)) of the acceleration (a) by the evaluation unit (11),

[0072] (103) comparing the evaluation (a) with the evaluation (a-1) of a chronologically preceding characteristic (a(t)) or with a predefined evaluation (a0),

[0073] (104) assignment of the evaluation (a) to one of several processes (V1, V2), the processes (V1, V2) being selected from a group which includes occupying (V1) the vehicle seat (1) and leaving (V2) the vehicle seat (1) by the driver (F), or

[0074] (105) assigning the evaluation (a) to one of several states (J1, J2), the states (J1, J2) being selected from a group which comprises an occupied state (J1) and an unoccupied state (J2) of the vehicle seat (1),

[0075] (106) repetition of steps (101) to (105) up to a predefinable termination criterion.

[0076] In the present case, it is first checked whether standing up V2 is detected. If no, it is checked whether sitting V1 is detected. If no, it is checked whether the status occupied J1 is recognized.

[0077] Alternatively, it can be provided that it is checked in step 105 whether the unoccupied J2 state is recognized.

[0078] Also shown is a step (107) which, after determining the standing up, is intended to ensure that, for example, driving over a pothole was not incorrectly assigned to a standing up process V2. This step (107) checks whether seat occupied, J1 is recognized. If not, the previous assumption was correct and the seat is actually not occupied. If yes, it is assumed that the assignment was wrong; the state J1 is determined.

[0079] It is understood that the embodiment explained above is merely an initial configuration of the system S according to the invention and of the method 100 according to the invention. In this respect, the configuration of the invention is not limited to this embodiment.

[0080] All the features disclosed in the application documents are claimed as being essential to the invention, provided that, individually or in combination, they are novel over the prior art.

LIST OF REFERENCE SIGNS

[0081] 1 vehicle seat

[0082] 1x longitudinal direction of the seat

[0083] 1y width direction of the seat

[0084] 1z height direction of the seat

[0085] 2 upper part

[0086] 3 lower part

[0087] 4 scissor-type frame

[0088] 5 suspension-damper system

[0089] 6 upholstered part

[0090] 10 acceleration sensor

[0091] 11 evaluation unit

[0092] 20 actuator

[0093] 30, 40 diagram

[0094] 40-44, 50-60 peaks

[0095] 100 method

[0096] 101-107 step

[0097] a, a(t), ai(t), aj(t), a1(t), a10(t) acceleration

[0098] a evaluation

[0099] CU control unit

[0100] f frequency

[0101] F driver

[0102] h1-h4 envelope curve

[0103] J1, J2 state

[0104] M vehicle

[0105] S system

[0106] t time