Patent Description:
Moreover, the present invention concerns a related control method for controlling the controllable arm, a computer program product executing the control method, a heavy vehicle comprising the control system, and a control unit comprised in the control system.

As known, a heavy vehicle provided with a controllable arm is suitable to perform different tasks due to its arm capability and its ability to manipulate, carry and dump a load. Examples of such heavy vehicle are a wheel loader, a telehandler or an excavator, where the controllable arm carries, for example, a bucket as shown in <CIT>.

During use of such heavy vehicles, the drivers driving them and controlling the controllable arm must carefully operate the controllable arm when the latter is loaded, in order to avoid spilling of the loaded product (e.g., soil, grain, etc.). In particular, in order to be more efficient and reduce the overall time to perform the required task, the drivers generally fully fill the bucket with the loaded product and manually control the controllable arm in rapidly performing consecutive manoeuvres, so that it is not unusual that part of the loaded product spills over and falls on the ground, thus forcing the drivers to perform additional manoeuvres to recover the spilled-over material and increasing the overall time and complexity of the task.

Therefore, the need is felt to reduce the spill-over of loaded material from the bucket when operating the heavy vehicle.

An aim of the present invention is to satisfy the above-mentioned needs.

The aforementioned aim is reached by a control system for controlling a controllable arm of a heavy vehicle, as claimed in the appended set of claims.

<FIG> shows, in a triaxial Cartesian reference system defined by axis X, Y and Z, a vehicle <NUM> provided with a controllable arm <NUM>. In particular, the vehicle <NUM> is a heavy vehicle (in details, a work vehicle), such as a compact wheel loader, a telehandler or an excavator (<FIG> shows a compact wheel loader), driven by a user.

The controllable arm <NUM> comprises a bucket <NUM> and a boom <NUM>' coupling the bucket <NUM> to a main body of the vehicle <NUM>. The controllable arm <NUM> is provided with at least one joint <NUM> actuated by a respective joint actuator <NUM> (hydraulic actuator, in particular a cylindrical actuator). As a non-limiting example, <FIG> shows the controllable arm <NUM> having two joints <NUM> (i.e., a tilt joint and a boom lift joint, indicated respectively with the reference numerals 16a and 16b) and three respective joint actuators <NUM> (i.e., a tilt actuator and two boom lift actuators, indicated respectively with the reference numerals 17a and 17b).

Moreover, the vehicle <NUM> includes an input command acquisition device <NUM>, such as a joystick (in the following indicated as joystick <NUM>), for example placed in a cabin <NUM> of the vehicle <NUM>. In use, the user operates the joystick <NUM> to control the controllable arm <NUM>, i.e. to control the trajectory of the controllable arm <NUM>.

As better discussed in the following, the user manually selects a level of jerk of the vehicle <NUM> (also called in the following manually selected jerk) among a plurality of manually selectable jerks when the vehicle <NUM> is not in a predefined working mode (e.g., digging operation) and the vehicle <NUM> is travelling in forward direction, while the jerk level is automatically selected when the vehicle <NUM> is in the predefined working mode and the vehicle <NUM> is not travelling in forward direction (e.g., is travelling in reverse direction).

In particular, upon occurrence of specific conditions as better described in the following, the user manually controls the level of jerk of the controllable arm <NUM>, so that the aggressiveness of the manoeuvre carried out by the controllable arm <NUM> can be modified depending on the vehicle working conditions and situations. For example, the user can choose among a plurality of jerk levels (e.g., <NUM> to <NUM>, where <NUM> corresponds to low jerk, <NUM> corresponds to medium jerk and <NUM> corresponds to high jerk) to set a lower aggressiveness of the manoeuvre of the controllable arm <NUM> (suitable for manoeuvres requiring slow movements and high accuracy) or a higher aggressiveness of the manoeuvre of the controllable arm <NUM> (suitable for manoeuvres requiring fast movements and low accuracy). The jerk level is set by the user by operating an aggressiveness setting mean <NUM> that can be, as non-limiting examples, an aggressiveness setting switch <NUM>, for example carried by the joystick <NUM> or by the vehicle <NUM> (e.g., located in the cabin <NUM>).

As illustrated in <FIG>, the vehicle <NUM> further comprises an engine <NUM> (e.g., a thermal engine) mechanically coupled to an arm pump <NUM> (e.g., hydraulic pump). The vehicle <NUM> further comprises an arm hydraulic circuit <NUM> including the joint actuators <NUM> and the arm pump <NUM> providing hydraulic power to the joint actuators <NUM> in order to actuate the joints <NUM> of the controllable arm <NUM>. In particular, the arm pump <NUM> pumps a fluid (e.g., a substantially incompressible fluid such as oil) to the joint actuators <NUM>, thus actuating the latter.

The vehicle <NUM> further comprises a motor hydraulic circuit <NUM> with a hydraulic pump <NUM> mechanically coupled to the engine <NUM> and a hydraulic motor <NUM> powered by the hydraulic pump <NUM> and powering a driveline <NUM> of the vehicle <NUM>. In particular, the hydraulic pump <NUM> pumps a fluid (e.g., a substantially incompressible fluid such as oil) to the hydraulic motor <NUM>, thus actuating the latter. More in details, the hydraulic pump <NUM> is fluidly connected to a first conduit, referred to in the following as forward hydraulic line 24a, extending between the hydraulic pump <NUM> and the hydraulic motor <NUM> and being pressurized when the vehicle <NUM> moves forward; and the hydraulic pump <NUM> is fluidly connected to a second conduit, referred to in the following as reverse hydraulic line 24b, extending between the hydraulic pump <NUM> and the hydraulic motor <NUM> and being pressurized when the vehicle <NUM> moves rearward.

Alternatively, the vehicle <NUM> comprises an electric motor (not shown) powering the driveline <NUM>.

A control unit <NUM> (e.g., a vehicle control unit or a dedicated controller or control unit) of the vehicle <NUM> is electrically coupled to the joint actuators <NUM>. As better discussed in the following, the control unit <NUM> acquires input data from the vehicle <NUM> and, based on these input data, controls the joint actuators <NUM>. As an example, the control unit <NUM> comprises a data storage unit <NUM> (referred to in the following as memory <NUM>, such as a RAM memory) and an elaboration unit <NUM> electrically coupled between them.

As better discussed in the following, in use, the control unit <NUM> receives sensor signals from a plurality of sensor means. The sensor signals are indicative of working conditions of the vehicle <NUM>, such as of a digging operation.

In particular, in use, the control unit <NUM> receives a vehicle speed signal from a vehicle speed sensor <NUM> carried by the vehicle <NUM>. The vehicle speed signal is indicative of a speed of the vehicle <NUM> travelling on the ground. For example, the vehicle speed is obtained from a wheel speed sensor of a known type, or is calculated based on an engine rotation speed.

The control unit <NUM> further receives a transmission state signal indicative of a currently engaged state of a transmission of the vehicle <NUM> (i.e., forward, neutral or reverse transmission). For example, the transmission state signal is acquired from a FNR switch <NUM> of the vehicle <NUM>, of a per se known type.

The control unit <NUM> further receives a hydraulic function state signal indicative of a state of the arm hydraulic circuit <NUM> (i.e., the arm hydraulic circuit <NUM> is enabled or disabled, and the fluid is circulating in the arm hydraulic circuit <NUM> or not, thus providing or not power to the joint actuators <NUM>). For example, the hydraulic function state signal is acquired from a hydraulic function activation switch <NUM> of the vehicle <NUM>, of a per se known type, switching on or off the arm hydraulic circuit <NUM> (i.e., controlling the joint actuators <NUM>).

The control unit <NUM> further receives hydraulic pressure signals from one or more pressure sensors <NUM> in the motor hydraulic circuit <NUM>, indicative of the hydraulic pressure of the fluid circulating in the motor hydraulic circuit <NUM>. In particular, a first hydraulic pressure signal is received from a first pressure sensor 46a, placed in the forward hydraulic line 24a of the motor hydraulic circuit <NUM>. Moreover, optionally, a second hydraulic pressure signal is received from a second pressure sensor 46b, placed in the reverse hydraulic line 24b of the motor hydraulic circuit <NUM> so that the control unit <NUM> can compute a relative difference of the first and second hydraulic pressure signals.

The control unit <NUM> further acquires, from one or more engine sensors <NUM> carried by the engine <NUM>, an engine speed signal indicative of the rotational speed of the engine <NUM>. For example, the one or more engine sensors <NUM> are rotational speed sensors.

The control unit <NUM> further acquires a boom position signal and a bucket position signal from arm position sensors <NUM> carried by the controllable arm <NUM>, the boom position signal and the bucket position signal being indicative of the positions of the boom <NUM>' and, respectively, of the bucket <NUM>. For example, the arm position sensors <NUM> acquire data of the joints <NUM> (e.g., in the joint space). According to an exemplary and non-limiting embodiment of the present invention, illustrated in <FIG>, the arm position sensors <NUM> comprise a tilt angular sensor 28a coupled to the tilt joint 16a and a boom angular sensor 28b coupled to the boom lift joint 16b. The tilt angular sensor 28a and the boom angular sensor 28b acquire the angular positions of the tilt joint 16a and, respectively, of the boom lift joint 16b. From these data, the positions of the boom <NUM>' and of the bucket <NUM> are calculated accorded to per se known techniques, for example by the control unit <NUM>. As an example, the position of the boom <NUM>' is calculated as a relative angle of the boom <NUM>' with respect to the ground position (e.g., an angular displacement of the boom <NUM>' with respect to an angular position of the boom <NUM>' when the latter is set in ground position, e.g. when the boom lift actuators 17b are fully retracted) and the position of the bucket <NUM> is calculated as a relative angle of the bucket <NUM> with respect to a dumping position of the bucket <NUM> (e.g., an angular displacement of the bucket <NUM> with respect to an angular position of the bucket <NUM> when the latter is set in dumping position, e.g. when the tilt actuator 17a is fully retracted).

The control unit <NUM> further acquires a pump signal indicative of a control current of the displacement of the hydraulic pump <NUM>. In particular, the displacement of the hydraulic pump <NUM> is controllable through an input current (i.e., the control current) that is a function of the engine speed and, more in details, is based on a characteristic curve in two variables that are the engine speed and the input current previously used. For example, the pump signal is acquired from a pump control mean <NUM> operable to control the displacement of the hydraulic pump <NUM>.

The control unit <NUM> further acquires the selected jerk level set by the user through the aggressiveness setting switch <NUM>.

During use of the vehicle <NUM>, the control unit <NUM> (in details, the elaboration unit <NUM>) acquires the vehicle speed signal, the transmission state signal, the hydraulic function state signal, the first hydraulic pressure signal, the engine speed signal, the boom and bucket position signals, the pump signal and the selected jerk level both at a considered (or current) time instant (e.g., t=t*) and during a preceding predetermined period of time (e.g., ΔT) immediately preceding the considered time instant t=t*. In other words, these signals are acquired at t*-ΔT < t ≤ t*. For example, the acquired signals are temporarily stored in the memory <NUM>.

If the transmission state signal at the considered time instant t=t* is not indicative of the reverse state (e.g., is indicative of the forward state), the control unit <NUM> (in details, the elaboration unit <NUM>) generates at the considered time instant t=t* a jerk command that is indicative of the jerk level manually selected by the user at the considered time instant t=t*.

If the transmission state signal at the considered time instant t=t* is indicative of the reverse state, the control unit <NUM> (in details, the elaboration unit <NUM>) compares the vehicle speed signal, the transmission state signal, the hydraulic function state signal, the first hydraulic pressure signal, the engine speed signal, the boom and bucket position signals and the pump signal, acquired during the preceding predetermined period of time ΔT, with respective reference signals that are, for example, stored in the memory <NUM>. This is done to assess if a predetermined working condition (i.e., digging condition and reverse engaged) of the vehicle <NUM> is verified. Based on the result of the comparison, the control unit <NUM> (in details, the elaboration unit <NUM>) generates at the considered time instant t=t* the jerk command that is indicative either of the jerk level manually selected by the user at the considered time instant t=t* (in details, if the predetermined working condition of the vehicle <NUM> is not verified, i.e. the vehicle <NUM> is not in digging condition and/or the forward is engaged) or of a predetermined jerk level (in details, if the predetermined working condition of the vehicle <NUM> is verified, i.e. the vehicle <NUM> is in digging condition and the reverse is engaged).

The jerk command generated by the control unit <NUM> is used to control the controllable arm <NUM>, according to per se known techniques.

In details, the predetermined jerk level (or, for simplicity, the predetermined jerk) is either the lowest jerk level that the user can manually select or a jerk level that is lower than the jerk level that has been manually selected at the considered time instant t=t*. According to an embodiment of the present invention, the predetermined jerk level is the lowest jerk level that the user can manually select (i.e., jerk level equal to <NUM>), thus corresponding to the lowest aggressiveness that can be selected for the control of the controllable arm <NUM>. According to a different embodiment of the present invention, the predetermined jerk level corresponds to the jerk level manually selected at the considered time instant t=t*, that is decreased by a predefined jerk quantity (e.g., if the user selects the jerk level to be equal to <NUM> and the predefined jerk quantity is equal to <NUM>, the predetermined jerk level is <NUM>), so that the aggressiveness of the manoeuvres of the controllable arm <NUM> is lower than the manually selected one but still dependent on the latter. According to a further embodiment of the present invention, the predetermined jerk level is lower than any jerk level that can be manually selected by the user (e.g., the predetermined jerk level is <NUM>), so that the aggressiveness of the manoeuvre of the controllable arm <NUM> is minimized.

Moreover, the duration of the preceding predetermined period of time ΔT can be manually selected by the user, for example at the starting of the vehicle <NUM>. According to a non-limiting example, the preceding predetermined period of time ΔT is about <NUM> seconds.

More in particular, the jerk command at the considered time instant t=t* is set to be indicative of the predetermined jerk level if the transmission state is in reverse state at the considered time instant t=t* and is in forward state during the preceding predetermined period of time ΔT, and if the following conditions are verified during the preceding predetermined period of time ΔT:.

On the other hand, the jerk command at the considered time instant t=t* is set to be indicative of the jerk level manually selected by the user at the considered time instant t=t* if the transmission state is not in reverse state at the considered time instant t=t* or is in reverse state at the considered time instant t=t* but not in forward state during the preceding predetermined period of time ΔT or if at least one of the previously described conditions is not verified at one or more time instants that are comprised in the preceding predetermined period of time ΔT (in other words, at any time instant t*-ΔT < t < t*).

The control unit <NUM>, the aggressiveness setting switch <NUM>, the engine sensors <NUM>, the vehicle speed sensor <NUM>, the FNR switch <NUM>, the hydraulic function activation switch <NUM>, the pump control mean <NUM>, the arm position sensors <NUM>, the pressure sensors <NUM> and optionally the joystick <NUM> form a control system of the vehicle <NUM>. The control system implements, by means of the control unit <NUM>, a control method as previously discussed to generate the jerk command and thus to control the controllable arm <NUM>.

In view of the foregoing, the advantages of the control system according to the invention are apparent.

In particular, the control system of the vehicle <NUM> allows to automatically reduce the jerk of the controllable arm <NUM> when the vehicle <NUM> is in digging operation and is travelling in reverse direction (i.e., the transmission state is reverse state), so that a product (e.g., soil, grain, etc.) loaded in the bucket <NUM> is not spilled over on the ground while the vehicle <NUM> is performing the manoeuvres. Nonetheless, when the vehicle <NUM> is not in digging operation and is travelling in forward direction, the jerk is the one manually selected by the user, so that in this case the controllable arm <NUM> can be operated with an higher aggressiveness (i.e., at higher speed) that is chosen by the user.

This automatic control increases the comfort and the efficiency of the user driving the vehicle <NUM> during digging operations.

By automatically selecting the proper boom and bucket aggressiveness during digging operation, the digging operation is simplified and its efficiency is optimized. In particular, when the user approaches the pile with the vehicle <NUM> in forward, the aggressiveness is the one manually selected by the user while, when the user engages the reverse with the bucket <NUM> fully loaded, the boom and bucket aggressiveness is automatically reduced in order to avoid spilling over of the loaded product from the bucket <NUM>, thus increasing the comfort of the user and the efficiency of the operation.

It is clear that modifications can be made to the described control system, which do not extend beyond the scope of protection defined by the claims.

For example, although previously only jerk levels have been discussed, the same considerations apply with a more general selected jerk command provided by the user. For example, the selected jerk command can be a jerk level (i.e., constant value of jerk) or a jerk profile (i.e., time-dependent and time-varying profiles of jerk).

Claim 1:
Control unit (<NUM>) configured to be coupled to:
- an aggressiveness setting mean (<NUM>) operable by a user to manually select a manually selected jerk among a plurality of manually selectable jerks, for controlling a controllable arm (<NUM>) of a heavy vehicle (<NUM>) operable by the user;
- a transmission state selecting mean (<NUM>) operable by the user to select a transmission state for controlling a transmission of the heavy vehicle (<NUM>);
- a plurality of sensor means (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to acquire a respective plurality of sensor signals indicative of working conditions of the heavy vehicle (<NUM>); and
- the joint actuators (<NUM>) of the controllable arm (<NUM>),
wherein the control unit (<NUM>) is configured to:
- receive, at a current time instant (t*) and during a preceding predetermined period of time (ΔT) immediately preceding the current time instant (t*), the transmission state from the transmission state selecting mean (<NUM>), the manually selected jerk from the aggressiveness setting mean (<NUM>) and the sensor signals from the sensor means;
- if the transmission state at the current time instant (t*) is not indicative of a reverse state, generate at the current time instant (t*) a jerk command that is indicative of the manually selected jerk selected at the current time instant (t*);
the control unit is characterized in that it is configured to:
- if the transmission state at the current time instant (t*) is indicative of the reverse state, compare the transmission state and the sensor signals, acquired during the preceding predetermined period of time (ΔT), with reference signals to assess if a digging condition of the heavy vehicle (<NUM>) is verified;
- if the digging condition of the heavy vehicle (<NUM>) is not verified, generate at the current time instant (t*) the jerk command that is indicative of the manually selected jerk selected at the current time instant (t*);
- if the digging condition of the heavy vehicle (<NUM>) is verified, generate at the current time instant (t*) the jerk command that is indicative of a predetermined jerk,
wherein the jerk command is configured to control a jerk of the controllable arm (<NUM>), and
wherein the predetermined jerk is either a lowest manually selectable jerk among the manually selectable jerks, or is lower than the manually selected jerk selected at the current time instant (t*).