DE102005051407B4 - Device for ground clearance measurement, in particular on an agricultural machine - Google Patents

Abstract

Device for measuring ground clearance, in particular on an agricultural machine of which it is part and which is function-controlled with the ground clearance measurement signal (BAS), the ground distance meter comprising a periodically excited ultrasound transmitter / sensor (2) to be directed to the ground (B) in a predetermined distance range, whose respective first echo signal determines a respective response time, and those response times which lie in a time window (OG-UG) which includes twice the sound propagation time in the distance range (A), a first smoothing circuit operating continuously over a respective predetermined number of measured response times (G1), which generates a respective first smoothing value (1.G), and those response times, which lie between the respective first smoothing value (1.G) and the predetermined upper time window border (OG), are fed to a second smoothing circuit (G2) whose second smoothness they produce value (2.G) is multiplied by the speed of sound or scaled as the ground distance measurement signal (BAS) is output.

Description

The The invention relates to a device for ground clearance measurement, in particular on an agricultural machine, according to the preamble of claim 1 and an inventory density meter according to claim 19.

Known is such a device, which consists of a mechanical oblique on the Ground-based ground scanner with a sanding pad, the high Wear is subject and an angle encoder. The encoder signal becomes a height adjustment device controlled to maintain a constant ground clearance. Such mechanical scanner can be found z. B. mowers to a constant cutting height even if the ground is wavy, uneven, or pending is inclined. Also an inventory density meter with a skid scanner is known whose distance measuring signal a vertical slide so that a pendulum on a gallows suspended fouling probe suspended at a constant ground clearance, so that the pendulum deflection angle is a measure of population density, their measure of Control of the local Application rate of sprays or fertilizer is used. The problem the ground clearance measurement of agricultural equipment is in particular through the formation of lanes in the fields, depending on the type of soil and the previous use very different Have depths, of ever greater importance, because this causes the laterally arranged functional assemblies, like ploughshare, tiller, Sämaschinenschare, Plant teaser, cleaver, cutting unit, potato harvester, beet harvester, spreading device, Sprühwerk often work very poorly and the work result is endangered, z. B. because the spray only at a certain height the fungal or pest infestation can meet, or an unnecessarily high Material consumption arises and too high consumption of spray an environmental damage occurs.

Farther are from the brochure "Ultrasonic sensors multi-talented for industrial use", microsonic GmbH, 2002, ultrasound sensors are known, which periodically sound pulse packets send out with a vibrationally excited membrane and then the evaluated by the membrane recorded echo signals elekrisch converted.

By suitable excitation patterns and dimensions of the membrane will be for certain Applications specified the radiation characteristics. By filtering the received signals a Stöhrsignalunterdrückung is made. With a time window, a distance measuring range can be specified. In cramped conditions is The radiation characteristic with a flat reflector deflected by 90 °.

In a high and / or dense plant population occur depending on the location and branching of the stems and leaves so strong side echoes on that no sufficiently accurate ground clearance measurement for controlled operation an agricultural machine, in particular a stock detection device with the known Ultraschallmeßvorrichtung possible was. Also, by scattering to the side and / or absorption of the Sound often no signal echo can be received.

The known ultrasonic sensor device emits ultrasound signals at short intervals and then picking up the echo signals, whereupon the echo signal reinforced a threshold circuit, z. B. a Schmitt trigger circuit, supplied for digitization becomes. With the transmission of the sound pulse, a time counter is started and with the digitized echo signal it is stopped so that the counter content a measure of the sound time and thus for the distance of the obstacle in the sound field is. The respective meter reading is compared either with a predetermined count, whose result is output as a binary signal or provided for further processing, or in an analogous manner Output signal is converted.

Arriving later Echo signals are ignored, which suppresses multiple echoes.

Becomes in a plant stock with such, the prior art corresponding ultrasonic sensor measured against the ground, so hit successively several echoes from differently far away Stalks, leaves or other objects, which lie within the sound lobe of the ultrasonic sensor, a. This leads the Evaluation of each of the first echo according to the prior art not to a usable reading for the Distance of the lower ground. Also a Halmteiler, the Halme each apart around the sound beam side yields insufficient avoidance of echoes on the soil cover.

For further prior art is on the DE 691 32 170 T2 directed.

It The object of the invention is a contactlessly operating device to provide ground clearance measurement, which thus a significant less wear than a mechanical scanner is subjected and at the different Soil and fouling conditions so reliable works that one spaced machine control possible is.

The task is ge with a device according to claim 1 or with an inventory density meter according to claim 19. In this device, the ground distance measuring device comprises a periodically excited ultrasound sensor to be directed to the ground in a predetermined distance range, from whose respective first echo signal a respective response time is determined and only those response times which lie in a time window which includes twice the sound transit time in the distance range , a first smoothing circuit operating continuously over a respective predetermined number of measured response times, which generates a respective first smoothing value, and those response times lying between the respective first smoothing value and the predetermined upper time window boundary are fed to a second smoothing circuit, the first one generated by it second smoothing value is multiplied by the speed of sound or scaled as the ground distance measuring signal is output.

advantageous Embodiments are specified in the subclaims.

Advantageous becomes the smoothing device in each case, instead of the eliminated response time, a reference value is supplied, which e.g. the last associated smoothing value or the last allowed response time is.

The so completed Number of response times is preferably averaging or a median smoothing for generating the smoothing value subjected.

The Number of readings, over which is continuously averaged, is set at about 4 to 8 maximum 16, on the one hand one possible little delay until the measured value output occurs and on the other hand, a bearable Meßwertstreuung not exceeded becomes. The more readings are included in the smoothing the more accurate the mean, but the level of detail decreases and thus the reaction rate of the ground clearance measurement.

Out the measured and / or the averaged echo times becomes the ground distance calculated by multiplication with the speed of sound. in this connection becomes advantageous the temperature dependence of the speed of sound considered, by continuously measuring the temperature and evaluating it by the measuring processor.

Approximately the speed of sound is in air 331.6 + 0.6 t [° C] m / s.

A further improvement of the measurement results provides a Halmteiler, which surrounds the ultrasonic sensor. This sets the sound lobe as far as possible free from stalks and protects the Sensor from damage.

Prefers the sensor is placed horizontally in a Halmteilergehäuse, in which a reflector the sound by 90 ° from a bottom opening to Deflects the ground.

Preferably the reflector is concave, so that the sound beam is its focal point near the ground Has.

Of the Bodenabstandsmeßwert is preferably issued in analogue form for tax purposes, by giving each of the current digitally formed value in an analog converter is changed and held.

A preferred application of the Abstandsmeßsignals is the controller a vertical positioner of the sensor itself, so that he always approximately the same Ground clearance and thus under constant acoustic basic conditions is working.

With the vertical bearing controller is directly or indirectly the depth-controlled Machine function regulated, z. As the height of a mowing table or the depth a chipper or a Roders on his chassis. An immediate one Adjustment is advantageously carried out with an inventory density meter, whose gallows is attached to the pendulum on the lifting device, which also carries the Halmteiler with the ultrasonic sensor.

The Control of further machine functions is done with a height signal of the vertical positioner, which is removed from this. moreover in the case of using an inventory densitometer, a Evaluation of its measuring signal, z. B. to control a fertilizer or Spray-discharge rate, the sprayer height application with respect to the vertical-position signal of the vertical bearing controller also is controlled.

Advantageous embodiments are in the 1 to 8th shown.

1 shows a vertical arrangement of a sensor on a height-controlled inventory density meter in side view;

2 shows a block diagram of an ultrasonic sensor;

3 shows a sequence of echo timing signals;

4 shows an adjusted measurement signal sequence and its mean value - 1. smoothing value;

5 shows the averages and the one-sided filled support values;

6 shows the measured values padded with the supporting values and the second smoothing value formed therefrom which is output;

7 shows a Halmteiler from below;

8th shows a Halmteiler with a sound reflector in side view.

1 shows an inventory density meter consisting of a vertical column 1 with a gallows 10 exists, on which a pendulum 11 is suspended, whose deflection angle with an angle sensor 12 is measured. The gallows 10 and a stalk divider 13 with an ultrasound transmitter / sensor 2 are at the pillar 1 with a vertical slide 14 guided and driven by a position controller.

The pillar 1 is to be mounted on a three-point hitch of a vehicle in a known manner at the front. The received signals of the sensor are either evaluated immediately or forwarded as raw signals to an on-board computer of the vehicle, where they are converted to a Bodenabstandsmeßsignal that serves the altitude control. As a result, the ultrasonic transmitter / sensor work 2 and the pendulum 11 always about the same ground clearance A, whereby maximum accuracy is achieved. The stalk divider 13 is at the vertical slide 14 with an elastic rod 15 held, which prevents damage from obstacles when driving in the direction of travel F. The stalk divider 13 is designed ship-shaped and protects with its side walls the ultrasound sender / sensor 2 before contact with the stalks of the stock to be checked. The pole 15 is adjustable to different lengths, so that at a constant ground clearance A of the ultrasonic transducer / sensor 2 in each case a suitable height of the pendulum to the type of the stock 11 established.

2 shows a block diagram of the ultrasonic sensor 2 , The generator G periodically provides electrical pulses to the sensor / transmitter element 20 which converts it to sound and radiates and then electrically converts the received echo signals and to the amplifier V (t) which feeds a Schmitt trigger S which provides a digital signal when a predetermined threshold is exceeded.

Whenever a time control device 31 the generator G starts, becomes a time pulse counter 32 started, stopped with the Schmitt trigger signal and in an evaluation circuit 33 is read out.

The evaluation circuit 33 includes a response register AR, which determines the respectively determined number of time pulses from the time pulse counter 32 and a limiter LIM and two smoothing circuits G1, G2 connected in series. The limiter LIM pass only those measured values which lie in a time window between a predetermined upper limit OG and a lower limit UG, wherein in each case a signal OK signals compliance with the limits and otherwise a signal NOK is derived from the comparator CP.

3 shows a sequence of echo signals in analog representation, as occurs at the input of the limiter LIM. The permissible measured values are fed to a summing input of the first smoothing circuit G1, and the blanked measured values are replaced by a first reference value ST1, the last plausibly found measured value or the first smoothing value 1.G, such as 2 dashed lines shows.

simultaneously becomes this sequence of measurements a first latch D1, which receives a plurality of measured values and in each case the measured values an input of the first smoothing circuit G1 feeds, so that always over the last measured values the smoothing accomplished which is in the balance formed and in the first cache D1 are included.

Of the first smoothing circuit is followed by a comparator CP, the pre-smoothed measured values with the unsmoothed Measured values from the limiter LIM compares and only if the unsmoothed Value from the limiter LIM is larger, this unsmoothed Value of the second smoothing circuit G2 feeds and in the other case the last plausibly found measured value or the last-formed mean value 1.G as a second support value ST2 uses, as to the other smoothing device already described.

Also this second smoothing circuit G2 is a summer of the measuring or support values, a second buffer D2 for a number of measured values whose respective values are the second smoothing circuit G2 supplied become.

The in the second smoothing circuit G2 smoothed Value sequence is multiplied by the speed of sound and fed to a digital-to-analog converter D / A whose output signal stored in a latch circuit H and the output as a ground distance signal BAS supplied becomes. The temperature dependence The speed of sound is determined by evaluating a temperature measurement signal Temperature sensor T in the characteristic of the digital-to-analog converter D / A taken into account.

3 shows the unchanged measured values of a sequence of 1000 measurements in a measuring distance rescaled.

4 shows the measured value sequence cleaned by the limiter LIM - thin line - and the pre-smoothed first smoothing values 1.G - thick line.

5 shows the mean value - thin line - and the support value based input sequence on the first smoothing circuit G1 - thick line -.

6 shows the input sequence at the second smoothing circuit G2 - thin line - and the output signal of pre-smoothed second smoothing value 2.G, - thick line -.

All values in the 3 to 6 are analogously scaled scaled to the same scale of the ground clearance A.

The complex of the evaluation circuit 33 . 2 , is preferably implemented in a microprocessor. If an increased accuracy is required, a temperature sensor T is arranged on it, with which the temperature dependence of the speed of sound in air is taken into account by offsetting the temperature measuring signal with the measured echo propagation times.

7 shows a stalk divider 13 from underneath. He is in the direction of travel F by the stock of cereals or the like. guided and pushed by its wedge shape, the blades and leaves aside, so that the sound lobe of the sensor / encoder element 20 on the farmland. The sensor is protected by the cross-sectionally rhombic shape of the Halmteilerwandung. Above and below is the Halmteiler 13 open to avoid unnecessary secondary reflections.

8th shows a section through a Halmteiler 13 with a horizontal arrangement of the ultrasonic transducer / sensor 2 , its sound lobe and receiving characteristic by a reflector 21 is deflected to the field soil B. Below and above the ultrasonic transducer / sensor 2 there are fenders 22 which prevent contamination and damage by particles falling from the grain and by elastically high-speeding plant parts.

The reflector 21 is preferably concave, in particular cylindrical, formed in the direction of travel.

1

pillar

10

gallows

11

pendulum

12

angle sensor

13

dividers

14

vertical slide

15

Rods (on 13 )

2

Ultrasound transmitter / sensor

20

Sensor / transmitter element

21

reflector

22

mudguard

31

Timing controller

32

Time pulse counter

33

evaluation

B

arable land

A

Ground clearance (to 2 )

F

direction of travel

G

generator

V (t)

amplifier

S

Schmitt trigger

T

temperature sensor

AR

Auswerteregister

LIM

limiter

OG

Upper limit

UG

lower limit

OK

signal (within the limit)

NOK

signal (outside the border)

D1

1. cache

D2

Second cache

CP

comparator

G1

1. smoothing circuit

G2

Second smoothing circuit

THERE

Digital to analog converter

H

hold circuit

BAS

Ground clearance signal

1.G

pre-smoothed first smoothing value

2.G

second smoothed smoothing value

ST1

first support value

ST2

second support value

T

temperature sensor

Claims (19)

Device for ground clearance measurement, in particular on an agricultural machine, of which it is part and which is function-controlled with a ground distance measuring signal (BAS), with a periodically excited ultrasound transmitter / sensor (FIG. 2) to be straightened in a predetermined distance range on the field soil (B) 2 ), from whose respective first arriving echo signal a respective response time is determined, characterized in that such response times, which are in a time window (OG-UG), which includes twice the Schallaufzeit in the range of the ground distance (A), one continuously over each a predetermined number of measured response times working first smoothing circuit (G1), each having a pre-smoothed first Glät tion value (1.G) are generated, and those response times, which lie between the respective first smoothing value (1.G) and the predetermined upper limit (OG) of the time window, a second smoothing circuit (G2) are fed, the latter produced by her second smoothing value (2.G) multiplied by the speed of sound as the ground distance measuring signal (BAS) is output. Apparatus according to claim 1, characterized in that the echo signal is compared in a Schmitttrigger (S) with a limit value and its exceeding as a stop signal for a time pulse counter ( 32 ), which is started in each case when driving a generator (G) and the respective final count is fed to an evaluation register (AR). Device according to claim 2, characterized in that that each the contents of the evaluation register (AR) as an input value one Limiter (LIM) supplied which only sends such final meter readings to the first smoothing circuit (G1) lets pass that in the time window (OG-UG), and in the limiter (LIM) suppressed input values each by a first supporting value (ST1), which lies in the time window (OG-UG). Device according to claim 3, characterized in that that the input and the first support values (ST1), the first Smoothing circuit (G1) supplied be, as well a comparator (CP) supplied in which they come with the pre-smoothed first smoothing value (1.G) and only then to the second smoothing circuit (G2) if they are above this and otherwise in each case a second support value (ST2) supplied to this that is between the pre-smoothed first smoothing value (1.G) and the upper limit (OG) of the time window. Apparatus according to claim 3 or claim 4, characterized in that the first support value (ST1) is the last one in each case Input value that passed the limiter (LIM), or the last one stored input value and / or the second reference value (ST2) each is the last value that passed the comparator (CP), or the first smoothing value (1.G) is. Device according to Claim 2 or 3, characterized that each the input side of the smoothing circuit (G1, G2) supplied Support values (ST1, ST2) in the smoothing circuit (G1, G2) are averaged and also the supporting values (ST1, ST2) are stored in a buffer (D1, D2), wherein the latches (D1, D2) are each given four to sixteen Record values. Device according to one of the preceding claims, characterized characterized in that nachgeglättete, second smoothing value (2.G) converted by analogy a holding circuit (H) is output as the ground distance measuring signal (BAS). Device according to one of the preceding claims, characterized in that the time pulse counter ( 32 ) and the evaluation circuit ( 33 ) are installed with the smoothing circuits (G1, G2) in a microprocessor. Device according to claim 8, characterized in that the existence temperature measurement signal a temperature sensor (T) is supplied to the microprocessor, it to compensate for the temperature dependence of the Schallaufzeit for calculating the ground distance signal (BAS) from the smoothed second smoothing signal (2.G) uses. Device according to one of the preceding claims, characterized in that the ultrasound transmitter / sensor ( 2 ) is mounted on a lifting device with a height control device, which is supplied to the Bodenabstandsmeßsignal (BAS) as the ACTUAL signal. Device according to claim 10, characterized in that that on the lifting device at least a building or agricultural Device arranged is. Apparatus according to claim 11, characterized in that on the lifting device with a gallows ( 10 ) a pendulum ( 11 ) an inventory density measuring device is held pivotably, the pivot angle of an angle sensor ( 12 ) is detected. Apparatus according to claim 12, characterized in that the ultrasound transmitter / sensor ( 2 ) with a length-adjustable elastic rod ( 15 ) is held on the lifting device. Apparatus according to claim 12 or 13, characterized in that the ultrasound transmitter / sensor ( 2 ) of one in a direction of travel (F) each end tapered Halmteiler ( 13 ) is enclosed laterally. Apparatus according to claim 14, characterized in that the ultrasound transmitter / sensor ( 2 ) in the stalk divider ( 13 ) is arranged horizontally and its sound lobe with a reflector ( 21 ) is deflected downwards. Apparatus according to claim 15, characterized in that the ultrasound transmitter / sensor ( 2 ) on the top and bottom of an apron ( 22 ) is covered. Device according to claim 15, characterized in that the reflector ( 21 ) is concave, so that the sound beam is focused near the ground. Device according to claim 17, characterized in that the reflector ( 21 ) is cylindrically curved transversely to the direction of travel (F). Stock density meter with a device for Ground distance measurement according to one of the preceding claims.