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, an acceleration sensor being arranged on the upper part which is designed to determine a characteristic of an acceleration of the upper part as a function of time, an evaluation unit being provided which is designed to create an evaluation of the characteristic of the acceleration and optionally to send a signal to a higher-level control unit, the evaluation unit also being designed to assign the evaluation to a value of a mass of an object with which the vehicle seat is currently occupied.

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 that detects a characteristic of an acceleration of the upper part as a function of a time; and an evaluation unit that creates an evaluation of the characteristic of the acceleration and optionally sends a signal to a higher-level control unit, wherein the evaluation unit assigns the evaluation to one of a plurality of states of the vehicle seat, wherein the states are one of: occupied by the driver, unoccupied, or occupied by an inanimate mass, wherein the evaluation unit assigns the evaluation a value of a mass of an object occupying the vehicle seat, wherein the evaluation unit determines, when a vibration diagram presents a first pattern, that the state of the vehicle seat is occupied by the driver of a first mass, and wherein the evaluation unit determines, when the vibration diagram presents a second pattern different from the first pattern, that the vehicle seat is occupied by the inanimate mass of the first mass.

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

3. The system according to claim 2, wherein the evaluation unit is further designed to detect a deviation between a first frequency that is assigned to a maximum peak of a determined amplitude spectrum and a second frequency that is assigned to the maximum peak of the compared amplitude spectrum.

4. The system according to claim 2, wherein the evaluation unit is further designed to detect a deviation of at least one of a number of peaks or frequencies assignable to the peaks between the predetermined amplitude spectrum and the compared amplitude spectrum.

5. The system according to claim 1, wherein the evaluation unit is further designed to evaluate the characteristic of the acceleration and to compare the characteristic of the acceleration with at least one temporarily preceding characteristic or with at least one predetermined characteristic.

6. The system according to claim 1, wherein the evaluation unit is further configured to assign at least one envelope curve to the characteristic of the acceleration and one characteristic of the at least one envelope curve.

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, one acceleration sensor arranged on the upper part and an evaluation unit, the method comprising: 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 via the evaluation unit; comparing the evaluation to the evaluation of a temporally preceding characteristic or to a predetermined evaluation; assigning of the evaluation to one of a plurality of states, the states being one of: occupied by the driver, unoccupied, and occupied by an inanimate mass; assigning the evaluation a value of a mass of an object occupying the vehicle seat; determining, when a vibration diagram presents a first pattern, that the state of the vehicle seat is occupied by the driver of a first mass; determining, when the vibration diagram presents a second pattern different from the first pattern, that the vehicle seat is occupied by an inanimate mass of the first mass; and repeating the detecting, creating, comparing, and assigning of the evaluation to one of a plurality of states steps until a predefinable termination criterion is reached.

8. The system according to claim 1, wherein the control unit switches off an actuator when the evaluation unit determines that the vehicle seat is occupied by an inanimate mass or is unoccupied, and wherein the control unit refrains from switching off the actuator when the evaluation unit determines that the vehicle seat is occupied by the driver.

9. The system according to claim 1, wherein the control unit decides, based on the signal of the evaluation unit, whether to send a second signal to an actuator that changes a state of the actuator, and wherein the signal of the evaluation unit depends on the states of the vehicle seat.

10. The system according to claim 1, wherein the first pattern has a first periodic frequency, wherein the second pattern has a second periodic frequency, and wherein the first periodic frequency is smaller than the second periodic frequency.

11. The system according to claim 10, wherein the first pattern has a first amplitude, wherein the second pattern has a second amplitude, and wherein the first amplitude is less than the second amplitude.

12. The method according to claim 7, wherein the first pattern has a first periodic frequency, wherein the second pattern has a second periodic frequency, and wherein the first periodic frequency is smaller than the second periodic frequency.

13. The method according to claim 12, wherein the first pattern has a first amplitude, wherein the second pattern has a second amplitude, and wherein the first amplitude is less than the second amplitude.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1a shows a schematic representation of a vehicle with a vehicle seat and an actuator;

(3) FIG. 1b shows a schematic representation of a system according to the invention;

(4) FIG. 2 shows an example of a characteristic a(t);

(5) FIG. 3 shows an amplitude spectrum a(f) resulting from the characteristic of FIG. 2;

(6) FIG. 4 shows a preferred sequence of the method according to the invention.

DETAILED DESCRIPTION

(7) According to FIG. 1a, a vehicle M with a vehicle seat 1 and an actuator 20 is shown in a highly simplified representation. For example, vehicle M is a combine harvester and actuator 20 is the associated mower.

(8) FIG. 1b shows a system (S) for seat occupancy detection, 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 mounted 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) (not shown). It would also be conceivable that the scissor-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).

(9) 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.

(10) An acceleration sensor (10) is arranged on the upper part 2, in this case on the upholstery part (6) of the upper part 2, and 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 characteristic is shown as diagram 30. In the present case, this acceleration sensor (10) transmits the recorded characteristic to an evaluation unit (11).

(11) In the present case, the evaluation unit (11) is designed to create 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 diagram 40.

(12) The evaluation unit (11) is now designed to assign the evaluation (a′) to a value of a mass (m1, m2) of an object (F, K) with which the vehicle seat (1) is currently occupied, for example with a driver F or a box K as a dead mass. In other words, the evaluation unit (11) is designed to assign the evaluation (a′) to one of a plurality of states (J1, J2, J3), the states (J1, J2) being selected from a group which has an occupied state (J1), a non-occupied state (J2) of the vehicle seat (1) and a state (J3) of the vehicle seat (1) occupied by a dead mass. 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 (state J1).

(13) On the basis of the signals of the evaluation unit 11, the control unit (CU) can decide whether it transmits a signal to the actuator 20 which changes its state or not. 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.

(14) FIG. 2 now shows an oscillation curve a(t) with three temporally different sections (without any intermediate sections, which represent the exchange of mass), which can be assigned to states J1, J2 or J3 after evaluation. For example, the first section is to be assigned to state J2, that is to say to the unoccupied vehicle seat 1. The seat 1 oscillates substantially periodically with a specific frequency f2 and an amplitude A2. In the second 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 the case here that A1 is smaller than A2, which can be immediately read from the diagram, and that f1 is smaller than f2 (see also FIG. 3 for the evaluation). In the third section, the seat 1 is occupied by a dead mass, so that the seat 1 vibrates with an amplitude A3 and with a periodic frequency f3. It applies here that A3 is smaller than A2, but larger than A1, which can be immediately read from the diagram, and that f3 is smaller than f2, but larger than f1 (see also FIG. 3 for evaluation).

(15) Using an FFT, an amplitude spectrum a(f) was calculated from the characteristic of the curve according to FIG. 2 and represented according to FIG. 3. It can be seen that a plurality of peaks accumulate around three frequencies f1, f2 and f3. 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. The same applies to the frequency f3; this also is clearly distinguishable from the other two frequencies f1 and f2.

(16) FIG. 4 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 shown embodiment of the method 100 comprises the following steps:

(17) (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),

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

(19) (103) comparing the evaluation to the evaluation (a−1′) of a temporally preceding characteristic (a(t)) or to a predetermined evaluation (a0′),

(20) (104) assigning the evaluation to one of a plurality of states (J1, J2, J3), the states (J1, J2, J3) being selected from a group which comprises an occupied state (J1), an unoccupied state (J2) of the vehicle seat (1), and a state (J3) of the vehicle seat (1) occupied by a dead mass,

(21) (105) repetition of steps (101) to (104) up to a predefinable termination criterion.

(22) In the present case, it is first checked whether the unoccupied seat J2 is recognized. If no, it is checked whether the seat J1 occupied by a driver is recognized. If no, it is checked whether the seat J3 occupied by a dead mass is recognized. If no detection is possible here either, the process is repeated.

(23) It is understood that the exemplary embodiment explained above is merely an initial design of the system S according to the invention and the method 100 according to the invention. In this respect, the design of the invention is not limited to this exemplary embodiment.

(24) 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 with respect to the prior art.

LIST OF REFERENCE CHARACTERS

(25) vehicle seat

(26) 1x longitudinal direction of the seat

(27) 1y width direction of the seat

(28) 1z height direction of the seat

(29) 2 upper part

(30) 3 lower part

(31) 4 scissor-type frame

(32) 5 suspension-damper system

(33) 6 upholstered part

(34) 10 acceleration sensor

(35) 11 evaluation unit

(36) 20 actuator

(37) 30, 40 diagram

(38) 100 method

(39) 101-105 step

(40) a, a(t) acceleration

(41) CU control unit

(42) f frequency

(43) F driver

(44) J1, J2, J3 state

(45) K box

(46) M vehicle

(47) S system

(48) t time