Ultrasonic height control system

Claim 2

An ultrasonic distance measuring apparatus for use on an agricultural machine, the apparatus comprising an ultrasonic transducer system (LL, L, CA, CB, R, RR) for directing an ultrasonic signal onto the soil and for receiving a reflected signal, signal processing means (P) for receiving an input signal (R x ) corresponding to the reflected signal and for providing an output signal representative of the height of the transducer above the soil surface, the signal processing means comprising (a) means for sampling the input signal (Trigger Sampler); (b) timing means (counter) for measuring the time elapsed from the initiation of the ultrasonic transmitted signal (T x ) and the sampling of said sampling means; (c) means for storing (Stage A) first and second elapsed time values when the amplitude envelope of the input signal respectively: (i) exceeds a threshold value, and (ii) falls below a threshold value; (d) analysing means (Stage A) for analysing the stored elapsed time values and determining a deemed reference time value between said elapsed time values representative of the transit time of the ultrasonic signal from transmittal to receipt substantially irrespective of the amplitude and shape of the amplitude envelope, whereby variations in this reference time value indicate variations in the machine tool height; and (e) output means (Stage B, Stage C and either Stage D or Fig 7) for producing said output signal whereby adjustments required to the agricultural machine can be determined and/or effected.

Claim 3

Apparatus as claimed in Claim 1, and further comprising comparator means (Stage B) for comparing said output signal with a set value of desired effective height and producing an error signal, and means for providing (Stage C) an averaged error signal from a sample comprising a multiplicity of successive output signals.

Claim 4

An apparatus as claimed in Claim 2 and wherein the analysing means (Stage A Fig 2) establishes reference time values corresponding to a deemed peak in the amplitude envelope of the input signal.

Claim 5

An apparatus as claimed in Claim 2 wherein the analysing means (Stage A) calculates the reference time value as being a time along the time scale corresponding to one-third of the time approximately from the first elapsed time value to the second elapsed time value.

Claim 8

Apparatus as claimed in Claim 2, and including a microprocessor (P) providing said sampling means, said storing means, said analysing means and said output means, and the microprocessor also including trigger means for providing a trigger pulse (T x ) to cause transmittance of said ultrasonic signal onto the soil, and the apparatus further comprising an output control circuit connected to a monostable device (M₁) and to a transistor (T₁) which, when in use, is coupled to the transducer system for the purpose of stopping ringing of the transducer after the ultrasonic transmitted signal has been transmitted.

Claim 9

Apparatus as claimed in any one the preceding claims, and wherein said sampling means (Trigger Sampler) and said storing means (counter) have means for sampling and storing two successive peaks in the received signal, and the analysing means (Stage A) has means for analysing said two peaks in terms of their respective widths and having means for applying a predetermined test to use one or other of the peaks if they have a width exceeding a predetermined minimum or to use both peaks in computing a reference time value.

Claim 10

Apparatus as claimed in any one of the preceding claims and including processing means for processing the received signal with clipping (Fig 2-A₃ and A₄) of the amplitude envelope of the input signal.

Claim 11

Apparatus as claimed in any one of the preceding claims and including a multiplicity of transducers (LL, L, CA, CB, R, RR) in said transducer system with a multiplexing device (MUX) and wherein at least one of said transducers (CA or CB) is arranged as a centre sensor arrangement for a central portion of the agricultural machine, and the apparatus further comprising separate sampling means and storing means corresponding to the respective transducers, and said analysing means including means for providing a warning signal if any one of the transducers has an individual reference time value corresponding to an indicated averaged error signal significantly different from the average of said centre sensor arrangement.

Claim 12

Apparatus as claimed in any one of the preceding claims and including calibration means (S₄, P) adapted to be actuated when desired and intended to be operated with the agricultural machine set with its tools in a zero depth position, the agricultural machine in this calibration mode being adapted to store the averaged reference time values determined for each transducer in the system as a calibration value, whereby in normal operation differences from this value represent the distance of the tool from this zero depth position.

Claim 13

Apparatus as claimed in Claim 11 and including a multiplicity of ports adapted to be connected to respective transducers, the apparatus having calibration means adapted to be actuated in a calibration mode, and the apparatus having a multiplexer (MUX) for sequentially actuating the respective transducer ports, and a port control device being provided for sampling the received signals on each port during calibration and upon termination of calibration suppressing the address of the multiplexer to any ports from which received signals are not detected during the calibration mode.

Claim 14

Apparatus as claimed in any one of the preceding claims and including motion detection means (P) comprising means for detecting whether the received signal includes variance above a predetermined threshold level and then and only then enabling the output means.

Claim 15

Apparatus as claimed in Claim 1 and including a differential buffer (Fig 7) in the output means and operating (a) to suppress any output signal if the error signal is less than a predetermined value, (b) for a relatively small value of error signal equal to or greater than said predetermined value suppressing the output signal and only enabling the generation of a corresponding corrective output signal if a sufficiently great error persists for a relatively long predetermined period of time, and (c) for a larger value of error signal greater than a second predetermined value, supressing the output signal and only enabling the generation of a corresponding corrective output signal if a sufficiently great error signal persists, but persists for a period of time which is substantially shorter than said relatively long predetermined period of time.

Claim 16

Apparatus as claimed in in any one of the preceding claims and inclduing means for averaging (Stage C) the error signal from values derived at sampling points in time after either said predetermined value or said second predetermined value has been exceeded, means for comparing (Fig 7) said predetermined value or said second predetermined value as the case may be after respectively said relatively long or said relatively short period of time with said average error signal, and providing the corresponding corrective output signal only if the predetermined value or said second predetermined value is exceeded, any said corrective output signal operating to reset said differential buffer.

Claim 17

An apparatus as claimed in Claim 14 and further comprising means for causing an immediate corrective error signal if the error signal exceeds a further predetermined value.

Claim 18

Apparatus as claimed in Claim 2 and having means for processing (Fig 7) the average error signal according to the following conditions and providing a corrective control signal substantially corresponding to the averaged error signal: (i) For an averaged error signal in a very small predetermined range from zero to a very small ceiling value, the control signal is not enabled; (ii) For an averaged error signal exceeding said ceiling value, a sampler controlled by a counter samples at regular intervals the averaged error signal for a first predetermined time and averages its samples and generates the control signal after a relatively long counting period; (iii) For a larger averaged error signal exceeding a threshold value substantially greater than said ceiling value, a sampler at regular intervals samples the averaged error signal for a second period of time shorter than said first period of time and averages said samples and generates the control signal after the end of said second period of time; (iv) For a greater averaged error signal exceeding a higher threshold value than that applicable to condition (iii) above, a sampler at regular intervals samples the averaged error signal for a third period of time shorter than said second period of time and generates the control signal after the elapse of the third period of time; (v) For an averaged error signal exceeding a further threshold value greater than the higher threshold value referred to in (iv) above, the control signal is immediately enabled; (vi) The enabling of the control signal from any one of (ii), (iii), (iv) or (v) above resets all samplers; and (vii) If at the end of the counting time corresponding to any one of said samplers the averaged error signal as sampled has an absolute value less than the threshold value corresponding to that sampler then that sampler alone is reset.

Claim 19

An ultrasonic distance measuring apparatus for use on an agricultural machine, the apparatus comprising (i) an ultrasonic transducer system (LL, L, CA, CB, R, RR) for directing an ultrasonic signal (T x ) onto the soil and for receiving a reflected signal (R x ); (ii) signal processing means (P) for receiving an input signal (Stage B, Stage C) corresponding to the reflected signal and for providing an output signal representative of the height of the transducer above the soil surface; (iii) means for providing a sample averaged error signal from a number of readings in a sample representative of the averaged difference between the actual transducer height above the soil and the desired height, said error signal also being representative of the departure of a working tool on the agricultural machine from a desired height relative to the soil surface; (iv) signal control means (Fig 7) for monitoring the change of the sample averaged error signal with time and for providing a controlled actuation signal for actuating a control system to adjust as required the agricultural machine to alter the height above the soil of the portion of the machine mounting the transducer; (v) the signal control means comprising a plurality of electronic counter means corresponding to error signal ranges having respective threshold values and arranged to count time to respective termination points after being switched on; (vi) each counter means for an error range which has a larger threshold than the next counter means in the series having a shorter termination point than the termination point of said next counter means; (vii) each of the counter means being controlled for being: (a) switched on when the sample averaged error signal at any sampling time is in the range to which that counter means corresponds and to count time to said termination point; (b) reset if the control system for the agricultural machine is actuated; and (c) a trigger for an actuation signal if the counter means reaches its termination point; and (viii) the apparatus having means for processing said actuation signal from any of the counter means for providing said control actuation system for the control system of the agricultural machine, said control actuation signal corresponding to the magnitude of the error signal.

Claim 20

An ultrasonic distance measuring apparatus for use on an agricultural machine, the apparatus comprising (i) an ultrasonic transducer system (LL, L, CA, CB, R, RR) for directing an ultrasonic signal (T x ) onto the soil and for receiving a reflected signal (R x ); (ii) signal processing means (P) for receiving an input signal (Stage B, Stage C) corresponding to the reflected signal and for providing an output signal representative of the height of the transducer above the soil surface; (iii) means for providing a sample averaged error signal from a number of readings in a sample representative of the averaged difference between the actual transducer height above the soil and the desired height, said error signal also being representative of the departure of a working tool on the agricultural machine from a desired height relative to the soil surface; (iv) signal control means (Fig 7) for monitoring the change of the sample averaged error signal with time and for providing a controlled actuation signal for actuating a control system to adjust as required the agricultural machine to alter the height above the soil of the portion of the machine mounting the transducer; (v) the signal control means comprising a plurality of electronic counter means corresponding to error signal ranges having respective threshold values and arranged to count time to respective termination points after being switched on; (vi) each counter means for an error range which has a larger threshold than the next counter means in the series having a shorter termination point than the termination point of said next counter means; (vii) each of the counter means being controlled for being: (a) switched on when the sample averaged error signal at any sampling time is in the range to which that counter means corresponds and to count time to said termination point; (b) reset if the control system for the agricultural machine is actuated; and (c) a trigger for an actuation signal if the counter means reaches its termination point; and (viii) the apparatus having means for processing said actuation signal from any of the counter means for providing said control actuation system for the control system of the agricultural machine, said control actuation signal corresponding to the magnitude of the error signal.

Claim 21

Apparatus as claimed in Claim 15, and for use in controlling a soil working machine and having means for establishing a dead band for error signals up to 0.75 cm, and said control means includes four counters arranged to operate substantially as follows:

Claim 22

Apparatus as claimed in Claim 19, and further comprising immediate mode means for causing a corrective output signal to be provided if an averaged error signal exceeds a threshold value of approximately 4 cm.

Claim 23

Apparatus as claimed in Claim 2, and further comprising control means (Fig 7) for processing said averaged error signal, the control means comprising a plurality of electronic counter means (P, Q, R, S) corresponding to error signal ranges having respective threshold values and arranged to count time to respective termination points after being switched on; and wherein (vi) each counter means for an error range which has a larger threshold than the next counter means in the series having a shorter termination point than the termination point of said next counter means; (vii) each of the counter means being controlled for being: (a) switched on when the sample averaged error signal at any sampling time is in the range to which that counter means corresponds and to count time to said termination point; (b) reset if the control system for the agricultural machine is actuated; and (c) a trigger for an actuation signal if the counter means reaches its termination point; and (viii) the apparatus having means for processing said actuation signal form any of the counter means for providing said control actuation system for the control system of the agricultural machine, said control actuation signal corresponding to the magnitude of the error signal.

Claim 24

Apparatus as claimed in Claim 21, and including means associated with each of the counter means for responding to the value of the sample averaged error signal at each sampling point in time and for determining an average value thereof at the termination point for that counter means, whereby the controlled actuation signal has a corresponding value, and after a counter means has been switched on, it continues to count towards its termination point even if individual sample averaged error signals fall outside the range for switch-on of that counter means; if the particular counter means which has been switched on experiences a value above the threshold for the next higher counter means, then this next higher counter means is then switched on and if it reaches its termination point before the first counter means, then it is the next higher counter means which causes the production of the requisite controlled actuation signal and all counter means are reset.

Claim 25

Apparatus as claimed Claim 22 and wherein a threshold gate (T.G.) is applied to the control actuation signal of the respective counter means for causing a machine adjustment signal to be issued if the samples of the averaged error signal exceeds the threshold for that counter means, but otherwise to cause resetting of that counter means only.

Claim 26

Apparatus as claimed in Claim 18, and wherein said sampling means and said storing means have means for sampling and storing two successive peaks in the received signal, and the analysing means has means for analysing said two peaks in terms of their respective widths and having means for applying a predetermined test to use one or other of the peaks if they have a width exceeding a predetermined minimum or to use both peaks in computing a reference time value.