PRIORITY CLAIM

This application claims priority from Italian Patent

Application No. 102017000064293 filed on June 9, 2017, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to a winch assembly for assisting the movement of a tracked vehicle, in particular a snow groomer, along steep slopes and the control method thereof .

In particular, a tracked vehicle comprises a chassis; a vehicle control unit; and the winch assembly, which in turn comprises a support structure; a drum rotatable with respect to the support structure; a cable which can be wound and unwound around the drum; an actuator assembly coupled to the drum to rotate the drum about the axis; and a winch control device coupled to the actuator assembly for controlling the actuator assembly so as to adjust the winding and unwinding of the cable.

BACKGROUND ART

Generally, a tracked snow grooming vehicle also includes a tiller for processing the snow of the ski slopes and a shovel for moving snow masses along the ski slopes. When the tracked vehicle is used on a piste characterised by particularly steep slopes the free end of the cable of the winch assembly is fixed to an upstream anchor so as to manoeuvre the tracked vehicle with the aid of the winch assembly, ensure greater safety and prevent slipping of the tracked vehicle if it loses adherence to the snow.

Document EP 1 118 580 discloses a method for controlling the winch assembly so that the pulling force of the cable changes according to the difference in the pressure values between the two pumps which supply the tracks of the snow grooming vehicle and the angle of the winch arm with respect to the direction of travel.

The control method works well within certain limits but is not very suitable when very short reaction times and strong robustness with respect to internal and external troubles are required.

DISCLOSURE OF INVENTION

One object of the present invention is to provide a winch assembly which overcomes at least one of the drawbacks of the prior art.

According to the present invention, there is provided a winch assembly comprising a support structure, a drum rotatable with respect to the support structure about an axis; a cable which can be wound and unwound around the drum; an actuator assembly coupled to the drum to define a pulling force of the cable and configured to receive a first control signal, indicative of a desired pressure of a pump of the actuator assembly, and/or a second control signal, indicative of a desired displacement of the pump of the actuator assembly; and a winch control device coupled to the actuator assembly to control the pulling force of the cable and configured to provide the first control signal and/or the second control signal; the winch control device being configured to determine the first control signal and/or the second control signal according to a measured speed of travel signal indicating the measured speed of travel of the tracked vehicle, a measured pulling force signal indicating the pulling force measured on the winch assembly, and one or more signals selected from the following group of signals: cable speed signal, wound cable length signal, desired pulling force signal set manually by an operator, arm angle signal indicative of the angle of the winch arm with respect to a direction of travel, and measured pressure signal indicative of the pressure measured in a high pressure branch of a hydraulic circuit of the actuator assembly.

Thanks to the present invention, the winch assembly guarantees precision in the control of the pulling force even for high pulling force values and very short reaction times in order to counter sudden changes in external load due to sudden ground changes or sudden changes in load of the tracked vehicle.

According to a preferred embodiment, the winch control device determines the first control signal and/or the second control signal according to the pressure associated with at least one of the pumps of at least one of the tracks or the difference in the associated pressures between two pumps of two tracks.

According to a preferred embodiment, the winch control device comprises a first frequency-adjustable active filter and an oscillation detector configured to receive, as input, the measured force signal and provide, as output, one or more frequency values if an oscillation in the measured force signal is detected; the first active filter being frequency-adjusted according to the frequency or frequencies detected by the oscillation detector so as to damp or eliminate the oscillations in the pulling force; the winch control device being configured to define the first control signal by means of the first active filter; preferably, the oscillation detector being configured to detect the oscillations by detecting the frequencies related to the harmonics having amplitude values greater than a given value and within a first range of detection frequencies. Thanks to the present invention, the winch assembly is insensitive to internal or external troubles in the control of the pulling force of the winch and provides a system of control of the pulling force having fast and stable dynamics. In greater detail, thanks to the present invention, the control of the pulling force is capable of reacting quickly to the operator's commands and/or to load changes due to external causes.

According to a preferred embodiment, the winch control device defines the first control signal according to the measured pulling force signal indicating the pulling force measured on the winch assembly.

Thanks to the present invention, the first control signal involved in adjusting the pulling force of the winch assembly is a feedback-controlled signal so that the desired force value is equal to that of the current winch force .

According to a preferred embodiment, the winch control device defines the first control signal according to the measured angle signal indicating the measured angle of the winch arm with respect to the direction of travel.

Thanks to the present invention, the pulling force is adjusted according to the pulling direction and the direction of travel, in particular, the pulling force is limited in some circumstances. According to a preferred embodiment, the winch control device defines the first control signal according to the cable speed signal.

According to a preferred embodiment, the winch control device defines the first control signal according to the wound cable length signal.

Thanks to the present invention, the control device ensures a more precise, faster and more stable adjustment of the pulling force, in fact, the value of the wound cable length allows a better adjustment of the torque to be applied to the drum so as to obtain a given pulling force.

According to a preferred embodiment, the winch control device defines the first control signal according to the signal from the measured speed of travel of the tracked vehicle indicating the measured speed of travel of the tracked vehicle.

According to a preferred embodiment, the winch control device defines the first control signal according to the desired pulling force signal defined through an external manual command given by an operator.

According to a preferred embodiment, the winch control device defines the first control signal according to the track pressure signal indicative of the measured pressure of at least one pump which supplies a respective track; preferably, the track pressure signal is indicative of the difference in the measured pressures between the hydraulic circuits supplying the first and the second track, respectively, of the tracked vehicle.

According to a preferred embodiment, the winch control device defines the second control signal according to the measured angle signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the cable speed signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the wound cable length signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the desired pulling force signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the measured pulling force signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the measured speed of travel signal.

According to a preferred embodiment, the winch control device defines the second control signal according to the measured pressure signal indicating the pressure measured in the high pressure branch of the hydraulic circuit of the actuator assembly.

According to a preferred embodiment, the winch control device defines the second control signal according to the signal from the engine revolutions of the tracked vehicle.

According to a preferred embodiment, the winch control device defines the second control signal according to the measured pressure of at least one of the pumps of at least one of the tracks and/or the difference in the measured pressures between two pumps of two tracks.

According to a preferred embodiment, the winch control device defines the second control signal according to a desired theoretical force value.

According to a preferred embodiment, the winch control device comprises a second frequency-adjustable active filter and an oscillation detector configured to receive, as input, the measured force signal and provide, as output, one or more frequency values if an oscillation in the measured force signal is detected; the second active filter being frequency-adjusted according to the frequency or frequencies detected by the oscillation detector so as to damp or eliminate the oscillations in the pulling force; the winch control device being configured to define the second control signal by means of the second active filter; preferably, the oscillation detector being configured to detect the oscillations by detecting the frequencies related to the harmonics having amplitude values greater than a given value.

According to a preferred embodiment, the actuator assembly comprises a hydraulic circuit and a variable displacement pump which supplies the hydraulic circuit and is configured to vary its displacement according to: the pressure measured in the high pressure branch of the hydraulic circuit, the pressure indicated by the first control signal, and preferably according to the second control signal.

Thanks to the present invention, the variable displacement pump is controlled through the first signal which is a signal obtained by means of a feedback control on the pulling force of the winch assembly and a feedback on the hydraulic pressure of the hydraulic circuit. In other words, the pump is controlled through two feedbacks: an electronic feedback via electronic devices on the measured pulling force and a hydraulic feedback via hydraulic devices on the hydraulic pressure of the hydraulic circuit. In addition, in the preferred embodiment, the variable displacement pump is controlled through another electronic feedback, i.e. through electronic devices, on the pressure of the hydraulic circuit .

According to a preferred embodiment, the winch assembly comprises a variable displacement motor coupled to the hydraulic circuit and supplied by the variable displacement pump by means of the hydraulic circuit; the variable displacement motor being configured to vary its displacement according to the pressure detected in the hydraulic circuit.

Another object of the present invention is to provide a tracked vehicle which reduces the drawbacks of the prior art .

According to the present invention, there is provided a tracked vehicle comprising an engine, preferably an internal combustion engine, a first and a second track, and a winch assembly according to any one of claims 1 to 11.

According to a preferred embodiment, the vehicle comprises a first pump to operate the first track and a second pump to operate the second track.

According to a preferred embodiment, the tracked vehicle comprises a vehicle control unit connected to the winch control device for defining a drive command signal.

Another object of the present invention is to provide a method for operating a winch assembly for a tracked vehicle which reduces at least one of the drawbacks of the prior art .

According to the present invention, there is provided a control method for a winch assembly of a tracked vehicle; the winch assembly comprising a revolving drum; a cable wound around the drum; an actuator assembly coupled to the drum to wind or unwind the cable comprising a variable displacement pump and a preferably variable-displacement hydraulic motor; the method comprising the step of controlling the pressure at the pump outlet to control the winding and unwinding of the cable and/or the displacement of the pump to control the winding and unwinding of the cable according to the measured speed of travel of the tracked vehicle, the value of the measured pulling force of the cable, and one or more values selected from the group of values of: cable speed, wound cable length, desired pulling force set manually by an operator, measured angle of the arm of the winch assembly with respect to a direction of travel, and pressure measured in a high pressure branch of a hydraulic circuit of the actuator assembly .

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will be apparent from the following description of a non-limiting embodiment thereof, with reference to the attached figures, wherein:

- Figure 1 is a side elevation view, with parts removed for clarity, of a tracked vehicle comprising a winch assembly and constructed in accordance with the present invention;

- Figure 2 is a diagram of a detail of the winch assembly of Figure 1; and

- Figure 3 is a diagram of a detail of the winch assembly of Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, reference numeral 1 defines, as a whole, a tracked vehicle. In a preferred embodiment, the tracked vehicle is a snow groomer for the preparation of ski slopes.

The tracked vehicle 1 comprises a chassis 2; two tracks 3 (only one shown in Figure 1) ; two drive wheels 4 (only one shown in Figure 1) operatively coupled to the respective tracks 3; a cabin 6; a user interface 7 located in the cabin 6; a shovel 8 supported at the front by the chassis 2; a tiller 9 supported at the rear by the chassis 2; a winch assembly 10 fixed to the chassis 2; an engine 11, preferably an internal combustion engine; and a power transmission 12 (partially visible in Figure 3) operatively connected to the internal combustion engine 11, the drive wheels 4, the shovel 8 and the tiller 9. Moreover, the power transmission 12 connects the engine 11 to the winch assembly 10.

The power transmission 12 can be hydraulic or electric or a hydraulic and electric combination. The tracked vehicle 1 comprises a vehicle control unit

13 connected to the user interface 7 and suitable to control the tracked vehicle 1.

The winch assembly 10 comprises a winch control device 13a configured to control the winch assembly 10. The winch control device 13a is also connected to the user interface 7.

In a preferred embodiment, the tracked vehicle 1 comprises a first pump (not visible in the attached figures) for operating one of the tracks 3 and a second pump (not visible in the attached figures) for operating the other track 3.

With reference to Figures 1 and 2, the winch assembly 10 comprises a support structure 14 fixed to the chassis 2, a drum 15 rotatable with respect to the support structure

14 around an axis A; a cable 16 having one end fixed to the drum 15 and wound around the drum 15; an actuator assembly 17 (Figure 3) coupled to the drum 15 to wind or unwind the cable 16 through a pulling force; and the winch control device 13a coupled to the actuator assembly 17 for controlling the pulling force of the cable 16.

The winch control device 13a being configured to determine and emit a first control signal SCI and a second control signal SC2 for controlling the actuator assembly 17. The actuator assembly 17 being configured to receive the first control signal SCI and the second control signal SC2 from the winch control device 13a and be controlled by the winch control device 13a through the first control signal SCI and the second control signal SC2.

The actuator assembly 17 comprises a hydraulic circuit 20, a variable displacement pump 21 that supplies the hydraulic circuit, and a variable displacement motor 22 that is supplied by the variable displacement pump 21 through the hydraulic circuit 20.

The actuator assembly 17 comprises a hydraulic choke valve 24, the input of which is connected to the high- pressure branch of the hydraulic circuit. In addition, the choke valve 24 is connected to the winch control device 13a for receiving and be controlled through the first control signal SCI. The choke valve adjusts its own output according to the first control signal SCI.

The variable displacement pump 21 comprising a pump control unit 21a in order to vary its own displacement. The pump control unit 21a comprises a hydraulic input connected to the output of the choke valve 24, and an electrical input configured to receive an electrical signal connected to the winch control device 13a for receiving the second control signal SC2. In greater detail, the pump control unit 21a is configured to vary the displacement of the variable displacement pump 21 according to the value of the pressure received through the hydraulic input and to the value of the electrical signal received by the electrical input, in greater detail the pump control unit 21a adjusts the displacement of the variable displacement pump 21 according to the smaller of the pressure value and the electrical signal value.

In an alternative embodiment, the second control signal SC2 is omitted or has a fixed value always equal to the maximum possible value, in this case the pump control unit 21a regulates the displacement of the variable displacement pump 21 according to the value of the pressure received from the hydraulic inlet.

In another alternative embodiment, the first control signal SCI is omitted or has a fixed value always equal to the maximum possible value, in this case the pump control unit 21a regulates the displacement of the variable displacement pump 21 according to the displacement value indicated by the second control signal SC2.

The variable displacement motor 22 comprises a motor control unit 22a that is configured to adjust the displacement of the variable displacement motor 22. The motor control unit 22a is connected to the high-pressure branch of the hydraulic circuit 20 to receive, as input, the pressurised liquid and adjust the displacement of the variable displacement motor 22 according to the pressure in the high-pressure branch of the hydraulic circuit 20. In other words, the variable displacement motor 22 is configured to vary its own displacement according to the pressure in the high-pressure branch of the hydraulic circuit 20. The pressure of the hydraulic circuit as shown previously is adjusted according to the first control signal SCI. Accordingly, the variable displacement motor 22 is configured to vary its displacement according to the first control signal SCI.

The variable displacement motor 22 is coupled to the drum 15 and acts on the drum 15 for adjusting the pulling force of the cable 16.

The winch control device 13a comprises a force sensor 26, in particular a load cell, coupled to the cable 16 for detecting the pulling force exhibited by the cable 16. The force sensor 26 determines and emits a measured pulling force signal FF indicative of the pulling force measured on the cable 16.

The user interface 7 is coupled to the winch control device 13a and allows the sending of a desired force command received from the operator U. In greater detail, the user interface 77 emits a desired force signal S4 according to the desired force command received from the operator U. The winch control device 13a comprises a pressure sensor 28 that is coupled to the high-pressure branch of the hydraulic circuit 20 for detecting the pressure of the hydraulic circuit 20 and emitting a measured pressure signal PF, which is an electrical signal indicative of the pressure in the high-pressure branch of the hydraulic circuit 20.

The tracked vehicle 1 comprises a speed sensor (not shown in the attached figures) to measure the speed of travel of the tracked vehicle 1. The speed sensor is coupled to the winch control device 13a to determine and send to the winch control device 13a a measured speed of travel signal S2 indicative of the measured speed of travel .

The winch assembly 10 comprises a cable speed sensor

(not shown in the attached figures) coupled to the cable 16 to measure the speed of movement of the cable 16 and determine a measured cable speed signal S3 indicative of the measured cable speed S3 to be sent to the winch control device 13a. In one embodiment of the present invention, the cable speed sensor is coupled to the drum and measures the revolutions of the drum and sends the number of revolutions of the drum to the winch control device.

The winch assembly 10 comprises a wound cable sensor coupled to the cable to measure the amount of cable wound around the drum. The wound cable sensor determines and sends a measured wound cable length signal S7 to the winch control device. In one embodiment, the wound cable sensor comprises a computing unit which calculates the amount of wound cable according to the number of positive or negative revolutions of the drum. The sensor that detects the number of revolutions of the drum can be part of the wound cable sensor or be a stand-alone sensor.

The winch assembly 10 comprises an angle sensor coupled to an arm 5 of the winch assembly 10 to measure the angle that the arm 5 of the winch assembly 10 forms with a direction D of travel of the tracked vehicle. The angle sensor determines and sends a measured angle signal S5 to the winch control device 13a. In particular, the arm 5 is fixed to the support structure 14 and is rotatable about a vertical axis B. The arm 5 is coupled to the drum 15 and guides the cable 16.

The tracked vehicle 1 comprises a pressure sensor (not shown in the attached figures) coupled to the first and the second pump (not shown) , respectively, of one of the tracks 3 and of the other track 3, in particular coupled to the hydraulic circuit of the first pump and to the hydraulic circuit of the second pump. The pressure sensor is configured to define a measured track pressure signal SI indicative of the difference in pressure between the two hydraulic circuits of the two tracks 3.

The track pressure signal SI, the measured speed of travel signal S2, the cable speed signal S3, the desired force signal S4, the measured angle signal S5, the wound cable length signal S7, the measured pulling force signal FF, the measured pressure signal PF are electrical signals.

The winch control device 13a is configured to determine the first and second control signals SCI and SC2 according to the signal S2 from the measured speed of travel of the tracked vehicle 1; the measured pulling force signal FF; the cable speed signal S3; the wound cable length signal S7; the measured angle signal S5 and the desired force signal S4.

In greater detail, the winch control device 13a defines the first control signal SCI according to the measured angle signal S5, the cable speed signal S3, the wound cable length signal S7, the measured speed of travel signal S2, the measured pulling force signal FF, and the desired pulling force signal S4.

The winch control device 13a also defines the first control signal SCI according to the track pressure signal SI .

With reference to Figure 2, the winch control device 13a defines the second control signal SC2 according to the measured angle signal S5, the wound cable length signal S7, the measured pulling force signal FF, the measured speed of travel signal S2, the measured pressure signal PF, the cable speed signal S3, and preferably the desired pulling force signal S4 and/or the track pressure signal SI.

In addition, the tracked vehicle 1 comprises an engine revolution sensor coupled to the engine 11 and defining a signal S6 from the measured engine revolutions indicative of a measured number of revolutions of the engine 11 of the tracked vehicle 1. The engine revolution signal S6 is an electrical signal.

In a preferred but non-limiting embodiment of the present invention, the winch control device 13a defines the second control signal SC2 according to the engine revolution signal S6 in addition to the signals indicated above .

In an alternative embodiment, one or more of the signals listed above are omitted in the determination of the first control signal SCI and the second control signal SC2 by the winch control device 13a.

In an alternative embodiment, the winch control device 13a does not define the second control signal SC2 or defines it with a fixed, non-variable value according to the signals listed above. In this case, the winch control device 13a defines the second control signal SC2 as being equal to the maximum possible control signal value SC2. The two alternative embodiments just described can be combined with each other, in other words one embodiment of the invention comprises a winch control device 13a which only determines the first control signal SCI according to the modalities listed above.

In an alternative embodiment, the winch control device 13a does not define the first control signal SCI or defines it with a fixed, non-variable value according to the signals listed above. In this case, the winch control device 13a defines the first control signal SCI as being equal to the maximum possible control signal value SCI.

The alternative embodiments just described can be combined with each other, in other words one embodiment of the invention comprises a winch control device 13a which only determines the second control signal SC2 according to the modalities listed above.

In a preferred but non-limiting embodiment of the present invention, the winch control device 13a determines the first and second control signals SCI and SC2 according to the following paragraphs.

The winch control device 13a comprises a computing unit 30 configured to calculate a desired theoretical force signal SFTD, indicative of a desired theoretical pulling force value. The control unit 30 receives the measured angle signal S5, the cable speed signal S3, the desired pulling force signal S4, the measured speed of travel signal S2, as input, and defines the desired theoretical force signal SFTD according to the input signals.

In one embodiment, the computing unit 30 receives the track pressure signal SI, as input, and defines the desired theoretical force signal SFTD also according to said signal together with the signals listed above.

The winch control device 13a comprises a computing unit 31 connected to the computing unit 30. The computing unit 31 receives the desired theoretical force signal SFTD, the wound cable length signal S7 and the measured force signal FF, as input, and determines a desired theoretical pressure signal SPTD.

The winch control device 13a comprises a frequency- adjustable active filter 32 and an oscillation detector 33 configured to receive, as input, the measured pulling force signal FF and provide, as output, a filtering signal SF indicative of one or more frequency values if an oscillation in the measured force signal FF is detected. The oscillation detector 33 is configured to detect the oscillations through the detection of the frequencies related to the harmonics having amplitude values greater than a given value and within a first range of detection frequencies. For this purpose, the oscillation detector 33 can perform an FFT or a DFT or have other electronic means for detecting harmonics greater than a given amplitude and within a first range of detection frequencies.

The active filter 32 is frequency-adjusted according to the frequency or frequencies detected by the oscillation detector 33 so as to damp or eliminate the oscillations in the pulling force. For this purpose, the active filter 32 receives the filtering signal SF and the desired theoretical pressure signal SPTD, as input, and determines the output control signal SCI. The control signal SCI is defined according to the desired theoretical pressure signal SPTD and filtered of any oscillations indicated by the filtering signal SF .

The winch control device 13a also comprises a computing unit 34 which receives the measured speed of travel signal S2, the wound cable length signal S7, the measured angle signal S5 and the measured pressure signal PF, as input, and provides an output desired theoretical displacement signal SCTD calculated according to the input signals .

In a preferred embodiment, the computing unit 34 receives the engine revolution signal S6, as input, and defines the desired theoretical displacement signal SCTD as well as the signals just listed above.

The winch control device 13a comprises a frequency- adjustable active filter 35 connected to the oscillation detector 33. The active filter 35 being frequency-adjusted according to the frequency or frequencies detected by the oscillation detector 33 so as to damp or eliminate the oscillations in the pulling force.

The active filter 35 receives the desired theoretical displacement signal SCTD and the filtering signal SF, as input, and determines a filtered desired theoretical displacement signal SCTDF. The filtered desired theoretical displacement signal SCTDF is determined according to the desired theoretical displacement signal SCTD and filtered of the frequencies indicated in the filtering signal SF .

The winch control device 13a comprises a computing unit 36 which receives, as input, the filtered desired theoretical displacement signal SCTDF, the filtering signal SF, the measured pulling force signal FF and the desired theoretical force signal SFTD, and defines, as output, the second control signal SC2 according to the input signals.

Moreover, the vehicle control unit 13 is configured to define a drive command signal DDC according to the engine revolution signal S6, the wound cable length signal S7, the measured pressure signal PF and the filtering signal SF .

In greater detail, the vehicle control unit 13 is connected to the winch control device 13a to define the drive command signal DDC.

In greater detail, the vehicle control unit 13 comprises a processing unit 13b and a processing unit 13c. The processing unit 13b receives, as input, the engine revolution signal S6, the wound cable length signal S7, the measured pressure signal PF, and determines a speed limit signal VSL indicating the maximum speed that the tracked vehicle 1 is enabled to reach. The processing unit 13c is connected to the processing unit 13b and receives the speed limit signal VSL and the filtering signal SF, as input, and defines the drive command signal DDC which determines the travel of the snow grooming vehicle 1. In particular, the drive command signal DDC can control the tracks of the snow grooming vehicle to define the travel of the snow grooming vehicle 1.

Thanks to the present invention, the control signal SCI regulates the pulling force of the winch assembly 10 through a feedback control system, which is formed by an electronic feedback control on the measured pulling force in series with a hydraulic feedback control on the pressure of the hydraulic circuit 20. The electronic feedback control is stable and insensitive to internal and external troubles and/or changes in commands and/or changes in loads thanks to the adjustable active filtering and the oscillation detector.

Moreover, in the embodiment in which the control signal SC2 is adjusted according to the inputs, the pulling force and the pulling speed are adjusted independently and via two electronic feedback controls, which are in series with the hydraulic feedback control. This type of control provides the advantages outlined above combined with the advantage of having a very precise and stable control on the pulling force and the pulling speed even for high values and for fast dynamics due to sudden changes in load. Moreover, this type of control reduces consumption.

It is also evident that the present invention also covers embodiments not described in the detailed description and equivalent embodiments, which fall within the scope of protection of the appended claims.