IT202000016045A1 - INDUSTRIAL FORKLIFT WITH IMPROVED STABILITY CONTROL - Google Patents

Description

TITLE: INDUSTRIAL TROLLEY WITH STABILITY CONTROL? IMPROVED

TECHNICAL FIELD OF THE INVENTION

The field of the present invention relates to an industrial truck, such as a fork lift truck, with a stability control? improved.

STATE OF THE ART OF THE INVENTION

Forklifts including a frame, a mast pivotally mounted to the frame, and a fork slidably mounted to the mast are known in the art. The gallows? used to lift a load, for example to transport goods to a warehouse. The upright can? be tilted with respect to the frame to facilitate loading and unloading of the goods.

During operation of the forklift truck, can? arise a problem of stability? due to a load being carried by the forklift and an incorrect command given by the forklift user. For example, in the event of a heavy load carried by the fork in a raised position with the mast tilted forward, the center of gravity of the system jointly composed of the truck and the load can be located beyond the front axle of the truck, thereby causing the truck to tip forward. Even a side flip? possible, in the event of a sharp steering commanded by the user which causes lateral acceleration leading to an unstable condition of the truck. A forward tipping can? This could also be caused by a braking operation causing excessive longitudinal deceleration, thereby bringing the center of gravity of the loaded truck outside the stability triangle, i.e. beyond the front axle of the truck.

In view of the problem of achieving stability? of the trolley, control systems have been designed to prevent commands from the user from bringing the trolley into an unstable condition, both when stationary (when the trolley is in a static condition, i.e. it is not running) and in a dynamic state (i.e. when the trolley is in gear). For example, a known control system can block the lifting operation of the fork in order to avoid a forward tipping under certain operating circumstances detected by means of a plurality? of trolley sensors. As a further example, ? it is also known to limit the steering angle during a travel of the truck, in order to avoid lateral overturning.

Stability control systems known, however, have failed to safely prevent a loss of stability? in any possible operating condition of the stationary trolley (i.e. in static conditions). Furthermore, the stability control systems? known have failed to achieve stability? while maximizing truck performance, for example due to excessive restrictions on truck operation that do not accurately reflect actual requirements to achieve stability. Furthermore, the stability control systems? known have failed to achieve a stability control? reliably over time, for example if a failure of one or more? sensors occurs during truck operation.

SUMMARY OF THE INVENTION

In view of the above problems, has the applicant devised a new stability control system? which relies on information from a tilt sensor that measures the tilt of the truck, to control the maximum lift height and forward tilt angle of the mast when stationary. By controlling the lifting operation and the tilting operation of the mast according to the inclination of the truck, ? Is it possible to achieve a stability control? safe and reliable in any condition, also taking into account possible inclined slopes (such as a ramp or similar) on which the forklift is operating. Furthermore, the stability control? involves a limited number of sensors relevant when stationary, in particular the tilt sensor, the load sensor and the sensors to control the lift height and tilt angle of the mast; therefore, ? It is possible to achieve highly reliable stationary operation while minimizing the potential impact of component failures. Consequently, the stability control? ? achieved in a simple and efficient way, considering a limited number of operating variables related to the loaded trolley.

Specifically, in view of the above purposes, the present invention proposes an industrial trolley which includes:

-a frame,

-a strut pivotally mounted on the frame,

- a lifting element for lifting a load, the lifting element being mounted on the mast in a sliding manner along the mast,

-a lifting actuator configured to move the lifting element along the mast,

-a tilt actuator configured to tilt the mast relative to the chassis,

-a unit? configured to control the lift actuator and the tilt actuator,

-a load sensor to detect the load weight on the lifting element and output to the unit? load information control showing the detected load weight, e

- a tilt angle sensor to detect the tilt angle of the mast with respect to the chassis and output to the unit? control information about a tilt angle indicating the detected tilt angle,

-a height sensor for detecting the height of the lifting element relative to the mast and outputting height information indicating the detected height of the lifting element,

wherein the industrial truck further comprises a tilt sensor configured to sense a tilt of the industrial truck with respect to a horizontal plane and output tilt information indicating the sensed tilt to the unit? control,

in which the unit? control ? configured:

- to control the lifting actuator by limiting the lifting height of the lifting element below a maximum allowable lifting height of the lifting element based on the tilt information, load information and information on a swing angle, e

- to control the tilt actuator by limiting the tilt angle below a maximum allowable forward tilt angle of the mast based on the tilt information, load information and height information. Consequently, the industrial truck performs a correct stability control? stationary in most of the possible operating conditions, for example also in the case of the trolley placed on an inclined surface. Thanks to the presence of the tilt sensor, a correct control of the lift and tilt actuators can performed efficiently and reliably by limiting the maximum forward tilt angle and maximum lift height.

Preferably, the unit? control ? configured to control the tilt actuator by limiting the tilt angle between the maximum allowable forward tilt angle of the mast and a maximum allowable rearward tilt angle of the mast calculated from tilt information, load information and to the height information. Consequently, by also controlling the maximum allowable rearward angle, the invention can also avoid a backward tipping of the trolley, which can? occur under certain circumstances on steep slopes.

Preferably, the unit? control ? configured to control the lift actuator by limiting the maximum allowable lift height of the lifter to a value calculated based on tilt information, load information and information about a tilt angle. Consequently, the invention can efficiently calculate the maximum permissible lift height under most relevant standstill conditions.

Preferably, the unit? control ? configured:

-to control the lifting actuator by limiting the maximum allowable lifting height of the lifting element to a value calculated only based on the tilt information, load information and information about a tilt angle, and

-to control the tilt actuator by limiting the maximum allowable mast forward tilt angle to a value calculated from the tilt information, load information and height information only. Consequently, all the relevant variables for a stability? stationary (lift height and swing angle) are controlled efficiently and reliably each based on only three variables to achieve correct stability control? under most possible stationary operating conditions.

Preferably, the unit? control ? configured to generate one or more? control values using a mathematical model of the industrial truck to which tilt information, load information, height information and information about a tilt angle are entered, the unit? controller being configured to control the lift actuator and/or the tilt actuator based on one or more? control values. Consequently, the invention can adequately control the lift and/or tilt actuator under a wide range of stationary conditions

using a cart

Preferably, one or more control values include one or more? of the following: the maximum permitted lift height, the maximum permitted forward tilt angle, the maximum permitted rearward tilt angle, the maximum permitted load weight, and/or an indication that a lifting operation or a The user commanded tilt operation is bringing the industrial truck close to an unstable condition. There? allows the control system to intervene correctly by blocking the user-commanded tilt or lift operation, or to issue a warning to the user if the truck approaches an unstable condition.

Preferably, the unit? control ? configured to generate one or more? control values by entering in the mathematical model of the industrial truck a speed? of the wheels, a longitudinal acceleration, a lateral acceleration and information on a steering angle detected by respective sensors of the industrial truck, the unit? control being configured to control the speed? of the trolley, the acceleration of the trolley and the braking of the trolley according to one or more? control values. As a result, control systems can achieve stability? even in the event of a dynamic condition (i.e. when the truck is running).

Preferably, one or more control values include one or more? of the following: -the maximum speed? allowed forward,

-the maximum speed? backwards allowed,

-maximum permissible forward acceleration,

-the maximum acceleration allowed backwards,

-the maximum deceleration of forward/reverse braking.

Preferably, the industrial truck includes a rear axle sensor for detecting the load weight on a rear axle of the industrial truck; the unit? control ? configured to estimate the longitudinal position of the load on the lifting element based on the load weight detected by the load sensor to detect the load weight on the lifting element and the load weight detected by the rear axle sensor, where the 'unit? control ? configured to generate one or more? control values by entering the estimated longitudinal position of the load into the mathematical model. By estimating the longitudinal position of the load on the fork (which can vary according to how the user has lifted the load), ? You can refine the mathematical model to calculate accurate control values, such as maximum allowable lift height, maximum allowable forward tilt angle, and maximum allowable rearward tilt angle. Therefore, the cart can? operate with the maximum possible performance while achieving safe and stable operation, given that the maximum values for lift height and tilt angles correctly reflect the real maximum operating ranges of the truck.

Preferably, the unit? control ? configured to stop a user commanded lift and/or pan/tilt operation when a control value generated by the unit? of control indicates that the industrial trolley ? close to a condition where the industrial truck rolls over backwards around the rear axle. As a result, safe operation ? achieved under most possible conditions.

Preferably, the unit? control ? configured to calculate the maximum allowable lift height and maximum allowable forward tilt angle continuously and repeatedly during industrial truck operation. There? allows you to constantly achieve a correct level of safety during operation. Preferably, when the wheels of the industrial trolley are in a stationary condition, the unit? control ? configured to control the lift actuator and the tilt actuator only based on the following inputs: load information, tilt information, height information, tilt information, and a command entered by a user using a user interface. There? allows to achieve a stability control? in correspondence with a static condition in a very simple and efficient way by limiting the number of sensors involved in the control.

Preferably, the tilt sensor ? a unit? Inertial Measurement Unit (IMU), configured to also detect a lateral acceleration and a longitudinal acceleration of the industrial truck and output lateral acceleration information indicating the detected lateral acceleration and longitudinal acceleration information indicating the detected longitudinal acceleration to the unit control for controlling a truck operation in a dynamic condition. Consequently, a plurality of detected signals that are useful both for the control of stability? from a standstill that for the control of stability? in dynamic condition can? be provided by a single existing sensor such as the IMU, thereby simplifying truck construction.

Preferably, when the forklift begins to pick up the load, the unit? control ? It is also configured to calculate a maximum allowable load weight based on tilt information, information about a tilt angle and height information, and to control the lift actuator by stopping a lift operation while ? load is being picked up, when the difference between the load weight determined by the load sensor and the maximum permissible load weight ? below a predetermined threshold. There? allows to achieve a high level of safety even when the load is picked up.

Preferably, the unit? control ? is also configured to reduce the speed to zero? of the trolley if the following conditions are verified simultaneously:

- the inclination information indicates an inclination of the trolley above a predetermined inclination threshold which ? different from zero,

- the load information indicates a load weight above a predetermined load threshold which ? different to zero; And

- a command entered by a user via a user interface requires the truck to be steered beyond a predetermined steering angle.

There? allows you to significantly improve the safety of operation in order to avoid steering on a ramp under load, which can? lead to a loss of stability? of the cart.

BRIEF DESCRIPTION OF THE DRAWINGS

The above advantages and other advantages of the present invention will be illustrated with reference to an exemplary embodiment of the invention, described with reference to the accompanying drawings listed as follows.

Fig. 1 shows a side view of an industrial truck according to the invention; Fig. 2 shows a schematic view of the sensors, the unit? control and actuators of the industrial truck;

Fig. 3 shows the carriage on a horizontal surface;

Fig. 4 shows the carriage on a downward inclined surface;

Fig. 5 shows the trolley on an inclined surface,

Fig. 6 shows a schematic view of an implementation of the unit? industrial truck control system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FAVORITE

Figure 1 shows an industrial truck 10 according to an embodiment of the present invention, for example a forklift truck. The industrial truck 10 includes a frame 11, a post 12 pivotally mounted on the frame 11, and a lifting member 13 (e.g., a fork) for lifting a load 14; the lifting element 13 ? mounted on upright 12 in a sliding manner along upright 12; in figure 1 the lifting element 13 ? shown in a raised position. Pillar 12? rotatably mounted on the frame 11 around the rotation pin 16, which ? preferably located near the front axle of the bogie 10. The mast 12 can? be swung in a range of directions including a vertical direction. The rotation pin 16 ? substantially parallel to the front axle of the bogie 10. In figure 1, the load 15 is illustrated with dashed line when the mast 12 ? swung forward by a swing angle ?. The industrial trolley 10 can? be operated electrically or can? include an internal combustion engine. Furthermore, the industrial truck 10 could include four wheels or three wheels arranged on a front axle and a rear axle.

The carriage 10 includes at least one lift actuator 32 (shown in Fig. 2 ) configured to move the lift member 13 along the mast 12 and a tilt actuator 31 (shown in Figs. 1 and 2 ) configured to tilt the mast 12 relative to to the frame 11. The trolley also includes a unit? controller 20 (shown in FIG. 2 ) configured to control the lift actuator 32 and

the swing actuator 31.

Preferably, as shown in figure 2, the unit? controller 20 also controls further actuators of the carriage, i.e. a wheel drive system 34. The wheel drive system 34 can be implemented according to any known art. In particular, the wheel drive system 34 can include one or more motors to drive the trolley wheels and a braking system. In addition, the unit control 20 pu? preferably be configured to issue a warning signal and/or an indication of a control value (such as a permissible operating range of the truck identified by a maximum permissible lift height, a maximum permissible forward tilt angle and the like) to an output interface 54 including for example a loudspeaker and/or a display.

The industrial truck 10 further includes a number of sensors for monitoring the operation of the truck and, in particular, its stability. from standstill. The 10 carriage sensors include at least:

- a load sensor 21 (figure 2) to detect the load value W (ie the weight of the load 14) on the lifting element 13 and output to the unit? control 20 load information showing the detected load weight,

-a swing angle sensor 22 (figure 2) for detecting the swing angle ? (shown in figure 1) of the upright 12 with respect to the frame 11 and issue to the unit? control 20 information about a swing angle indicating the detected swing angle,

-a height sensor 23 (figure 2) for detecting the height Hw (shown in figure 1) of the lifting element 13 with respect to the upright 12 and emitting to the unit? control 20 height information indicating the detected height of the lifting element 13.

According to the invention, the truck 10 further includes a tilt sensor 27 (shown in Fig. 2 ) configured to detect a tilt a (see Fig. 4 ) of the industrial truck with respect to a horizontal plane and output tilt information indicating the 'detected inclination to the unit? control 20.

Preferably, the unit? control 20 also includes a speed sensor? 24 to detect the speed? of the trolley, a steering angle sensor 25 for detecting the steering angle of the trolley, a longitudinal acceleration sensor 28 for detecting the longitudinal acceleration of the trolley and a lateral acceleration sensor 29 for detecting the lateral acceleration of the trolley ( figure 2). In the context of this application, the term ?longitudinal? refers to a direction from the rear axle to the front axle of the bogie 10, while the term ?lateral? refers to a direction transverse to the longitudinal direction of the carriage. Advantageously, the inclination sensor 27, the longitudinal acceleration sensor 28 and the lateral acceleration sensor 29 are formed by a single unit. of inertial measurement, IMU, 26. Ci? allows to reduce the number of sensors installed in the truck by using a single known sensor available on the market. Preferably, the IMU 26 ? mounted on a lower part of the frame 11.

According to a preferred embodiment, the truck 10 further includes a rear axle sensor 30 for detecting the load weight on a rear axle of the industrial truck 10. For example, the rear axle sensor 30 may be accomplished with a load cell mounted on the rear axle.

All sensors 21-30 output sensed information to the unit? of control 20, so

According to the present embodiment, the unit? of control 20 ? configured: - to control the lifting actuator 32 by limiting the lifting height of the lifting element below a maximum permitted lifting height Hmax of the lifting element based on the tilt information, load information and to information about a tilt angle, e

- to control the swing actuator 31 by limiting the swing angle ? below a maximum permissible forward tilt angle ?max,f of the mast based on the tilt information, load information and height information.

By controlling the lifting operation and the mast tilt operation according to the inclination of the truck, ? Is it possible to achieve a stability control? safe and reliable in a vast majority of conditions, also taking into account possible inclined slopes (such as a ramp or similar). Furthermore, the stability control? it involves a limited number of sensors when stationary, in particular the inclination sensor 27, the load sensor 23 and the sensors 21-22 to control the lifting height and the tilt angle of the mast; therefore, ? It is possible to achieve highly reliable stationary operation while minimizing the potential impact of component failures. Consequently, the stability control? ? carried out in a simple and efficient way when stationary, considering a limited number of relevant variables of the loaded trolley.

According to a further embodiment, another type of control is made by the industrial truck during a load pick-up: specifically, when the load pick-up is started, the unit? of control 20 ? configured to calculate a maximum allowable load weight based on tilt information, tilt angle information, and height information; moreover, the unit? control controls the lift actuator 32 by stopping a lift operation while ? the load 14 is being picked up, when the difference between the load weight W determined by the load sensor 21 and the calculated maximum permissible load weight Wmax ? below a predetermined threshold. There? allows you to achieve a desired level of safety when picking up the load. This kind of specific check based on the maximum permissible load weight Wmax during a pick-up can? be carried out even in the absence of the check described above according to the maximum permissible lift height and the maximum permissible forward tilt angle. In other words, in one embodiment of the industrial truck, the unit control 20 pu? be configured to control the lift operation at picking without being configured to control the lift actuator and tilt actuator to limit the lift height and forward tilt angle after picking the load.

As shown in figure 2, the unit? controller 20 receives a command entered by the user via a user interface 40, such as a command console. The command entered by the user can? include a command to raise/lower the lifting member 13, a command to tilt the mast 12 backwards or forwards, and a command to accelerate/brake the carriage 10.

According to the invention, the unit control 20 limits the lifting height Hw of the lifting element 13 below a maximum permitted lifting height Hmax to avoid a condition in which the trolley could lose stability. For example, the unit controller 20 could interrupt the lifting operation currently controlled by the user by means of the user interface 40 if the lifting height of the lifting element approaches the maximum permissible lifting height Hmax. The maximum permissible lifting height Hmax pu? be less than the maximum lifting height that ? made possible by the mechanical configuration of the trolley.

Similarly, according to the invention, the unit? control 20 limits the tilt angle of the mast 12 below a maximum permitted forward tilt angle ?max,f to avoid a condition in which the truck could lose stability. For example, the unit controller 20 could interrupt the tilt operation currently controlled by the user by means of the user interface 40 if the tilt angle approaches the maximum allowable forward tilt angle ?max,f. The maximum forward tilt angle allowed ?max,f pu? be less than the maximum forward tilt angle that ? made possible by the mechanical configuration of the trolley.

Preferably, the unit? control ? configured to control the swing actuator 31 by limiting the swing angle ? between the maximum permissible forward tilt angle ?max,f of the mast 12 and a maximum permissible rearward tilt angle ?max.b (see figure 1) of the mast 12 calculated from the tilt information, information load and height information. In fact, if the trolley is on a steep uphill slope, the inclination a could increase the risk of tipping backwards around the rear axle of the trolley 10, in the event that a heavy load is in the raised position (si see for example figure 5). The unit? control 20 controls the tilt angle so as to prevent the mast 12 from being tilted even more? backwards in a position that pu? cause the carriage to tip backwards. This additional control of the maximum permissible rearward angle improves the safety of the truck when stationary, even considering the case of extremely steep uphill gradients.

Preferably, the unit? of control 20 ? further configured to control the lifting actuator by limiting the maximum allowable lifting height Hmax of the lifting member 13 to a value calculated based on tilt information, load information and information about a tilt angle. For example, the unit control could use a mathematical model of the truck to calculate the maximum allowable height of the lifting element in static condition, based on tilt information, load information and information about a tilt angle. There? allows to efficiently, quickly and safely calculate the maximum height of the lifting element using a simple model and a limited number of signals from a limited number of sensors (i.e. the inclination sensor, the load sensor and the angle sensor of swing). As a result, you get a reliable and efficient algorithm to achieve stability. of stationary trolleys.

The unit? control 20 pu? be configured to generate one or more? control values using a mathematical model of the industrial truck to which tilt information, load information, height information and information about a tilt angle are entered, the unit? controller being configured to control the lift actuator and/or the tilt actuator based on one or more? control values. An example of a mathematical model used to generate control values ? described more after you.

Preferably, one or more control values include one or more? of the following: -the maximum permitted lifting height Hmax,

-the maximum forward tilt angle allowed ?max,f,

-the maximum permissible load weight Wmax,

-the maximum allowable rearward angle ?max,b, and/or -an indication that a lift operation or a user-commanded tilt operation is bringing the industrial truck close to an unstable condition. Most preferably, the control values generated by the unit? The control knobs 20 include all of the above control values for improving the stability control. The control values can be displayed by the output interface 54 during operation or an acoustic warning can be output from the output interface 54 to the user when the maximum values are approached during operation.

In one embodiment, the unit? control 20 pu? stop a user commanded lift and/or tilt operation when a control value generated by the unit? of control 20 indicates that the industrial trolley 10 ? close to a condition where the industrial truck rolls over backwards around the rear axle. Alternatively, the unit? control 20 pu? stopping a lifting operation commanded by a user when the sensed height of the lifting element 13 approaches the maximum permitted lifting height. Alternatively, the unit? control 20 pu? stopping a tilt operation when the tilt angle detected by the tilt angle sensor approaches one of the maximum allowable forward tilt angle ?max,f or the maximum allowable rearward angle ?max.b. The above control values allow for satisfactory control of the trolley to ensure stability? in case of static conditions, i.e. if the trolley is not moving and the wheels are not driven to rotate (when stationary).

According to a preferred embodiment, the unit? control 20 pu? also be configured to generate one or more? control values by entering in the mathematical model of the industrial truck a speed? of the wheels, a longitudinal acceleration, a lateral acceleration and information on a steering angle detected by respective sensors 24, 25, 28 and 29 of the industrial truck. In that case, the unit? of control 20 ? configured to control the speed? of the trolley, the acceleration of the trolley and the braking of the trolley according to one or more? control values. There? allows you to control the dynamic behavior of the trolley to avoid the risk of overturning and losing stability? of the truck due to sudden steering or excessive braking commanded by the user.

The one or more control values can include one or more? of the following:

-the maximum speed? allowed forward,

-the maximum speed? backwards allowed,

-the maximum permissible forward acceleration,

-the maximum acceleration allowed backwards,

-the maximum forward/reverse braking deceleration. Most preferably, the control values include all of the above-mentioned control values. These additional control values can also be displayed by the output interface 54 to the user. The maximum speed? allowed can? be calculated according to the maximum deceleration allowed and the maximum braking distance to be ensured.

Preferably, the unit? of control 20 ? configured to calculate the maximum permitted lift height Hmax and the maximum permitted forward tilt angle ?max,f continuously and repeatedly during operation of the industrial truck.

Likewise, the unit control 20 pu? calculate the maximum permissible rearward angle ?max.b continuously and repeatedly.

Preferably, when the wheels of the industrial trolley are in a stationary condition (ie when the trolley is not moving), the unit? of control 20 ? configured to control the lift actuator and the tilt actuator only based on the following inputs: load information, tilt information, height information, tilt information, and a command entered by a user using a user interface 40.

The unit? control 20 pu? advantageously be configured to estimate the longitudinal position of the load 14 on the lifting element based on the load weight detected by the load sensor 21 for detecting the load weight on the lifting element 13 and the load weight detected by the axle sensor back 30; moreover, the unit? of control 20 ? configured to generate one or more? control values by entering the estimated longitudinal position of the load into the mathematical model. Therefore, the control values calculated by the unit? of control 20 using the mathematical model are also calculated on the basis of the real longitudinal position of the load on the fork 13. The longitudinal position of the load 14 on the lifting element 13 can? be calculated as follows with reference to Figure 3.

The following equations describe the forces (or load weights) on the front and rear axles of the bogie as a function of the load weight W on the lifting element 13 and the weight G of the bogie 10.

Formula 1)

Formula (2)

where G? the weight of the trolley 10, W ? the weight of the load 14, at ? the longitudinal distance between the center of gravity of the bogie 10 and the front axle (corresponding to the fulcrum F in figure 3), a2 ? the longitudinal distance between the center of gravity of the bogie 10 and the rear axle of the bogie 10, 1 ? the distance between the front and rear axles of the bogie, Z1 ? the force on the front axle of the bogie and Z2 ? the force on the rear axle of the bogie, f ? the longitudinal distance between the front axle of the trolley (fulcrum F in figure 3) and the bearing surface of the lifting element 13 and r ? the longitudinal distance of the center of gravity of the load 14 from the vertical element of the lifting element 13. r+f represents the distance of the center of gravity of the load 14 from the axle

front of the carriage

From stationary, the following formula d? the maximum load weight allowed on the lifting element to maintain stability? and avoid a forward tipping:

Formula (3)

Using formula (2), the unit? control 20 pu? calculate the longitudinal position of the load (r+f) on the lifting element 13 using the measurement Z2 of the load weight on the rear axle as sensed by the rear axle load sensor 30 and the weight W sensed by the load sensor 21 (1, G and a are characteristic constant parameters

of the cart ):

Formula (4)

In fact, the value of r pu? vary according to the weight distribution of the load 14 and, also, of how the user lifts the load 14 with the lifting element 13. By calculating the value of r according to Formula (4), the unit? control 20 pu? entering a refined value of the position of the load 14 into the mathematical model of the trolley, thereby improving the accuracy of the control values produced using the model. There? allows you to improve the stability control? and truck performance by correctly estimating the maximum allowable load height and maximum forward/backward tilt angles. The refined mathematical model also allows you to improve the stability control? under dynamic conditions, for example by correctly controlling the maximum speed? or the maximum permitted steering angle. Preferably, the unit? controller 20 calculates an estimated longitudinal position of the load on the lifting member 13 whenever a load ? raised by the lifting element 13, i.e. when the load weight sensed by the load sensor 21 increases from zero to a non-zero value above a threshold.

The position limit of the load center 14 corresponds to the length of the fork 13, Lfork, in the longitudinal direction. This value? used preferably by the unit? control 20 to check the correct operation of the rear axle load sensor 30 by means of the following condition:

Formula (5)

where (r+f)ce//a load defines the value of r+f estimated by the unit? control based on the measurement from the rear axle load sensor 30 using the mathematical model. If the above condition as defined by formula (5) ? verified, an error occurs due to unreliable data received from the rear axle load sensor. If so a warning sign ? issued to the user indicating the error in the operation of the rear axle load sensor 30. Ci? allows to achieve a self-monitoring function of the control system, given that the correct functioning of the rear axle sensor ? monitored.

Figure 4 shows the carriage on a downward sloping surface, i.e. a non-horizontal surface. When the cart ? inclined at an angle a as shown in figure 4, the maximum weight Wmax that can? be carried on the lifting element 13 without losing stability? due to a forward rollover ? expressed by the following equation, which represents an example of a mathematical model used by the unit? control 20 for determining an unstable condition and/or control values as discussed above:

Formula (6)

in which i ? the height of the center of gravity of the trolley 10 (a constant parameter of the trolley 10) and hw ? the height of the center of gravity of the load 14.

In formula (6), r ? a function r(?,Hw) of the lift height Hw and the mast tilt angle ? shown in figure 1. Similarly, the height of the load hw pu? be expressed as a function hw(?,Hw) of the lift height Hw and the mast tilt angle ?.

When the sensed load weight W on the lifting member 13 approaches the

maximum load W max according to the following formula

(Formula 7)

the unit? control 20 issues a warning (for example an acoustic and visual signal on the display 54) to the operator and blocks the function commanded by the user (for example forward tilt and/or lifting).

When the cart ? in operation after picking up the load, the load weight W ? known based on the measurement of the load sensor 21, and the above formulas 6 and 7 can be used to calculate the maximum permissible lift height Hmax and the maximum permissible forward tilt angle ?max,f as a function of the inclination of the carriage a and the other current parameters of the carriage. During a load pick-up, the above formulas 6 and 7 can be used to calculate the maximum permissible load weight Wmax. Again, the above formulas 6 and 7 can be used to detect a dangerous condition where the truck is close to a forward tip condition. The mathematical model can? include a plurality? of formulas that define different dangerous conditions in which the truck can? lose stability. For example, the mathematical model pu? include a formula defining the condition of tipping back around the rear axle by setting Z1 equal to zero in formula (1) above and expressing the geometrical parameters of the bogie as a function of bogie inclination a, the angle of tilt and lift height. This situation ? relevant for example in the condition shown in Figure 5 which shows the case where the trolley is on an uphill slope with a load in a raised position. In that case, the unit? control 20 limits the rearward angle and/or lift height to prevent a backwards tip-over. The unit? control 20 could also control the translation of the carriage, ie the speed? of the trolley to avoid tipping backwards. As shown in figure 5, in this condition the fulcrum ? on the rear axle and the tipping condition ? defined as the condition in which the force on a front axle Z1 ? nothing: Z1 = 0. There? makes it possible to calculate the maximum permissible rearward angle to avoid a rollover backwards around the rear axle.

In a preferred embodiment, the unit? of control 20 ? is also configured to reduce the speed to zero? of the trolley if the following conditions are verified simultaneously:

- the inclination information indicates an inclination of the trolley above a predetermined inclination threshold which ? different from zero,

-the load information indicates a load above a predetermined load threshold which ? non-zero; And

- a command entered by a user by means of a user interface 40 requests to steer the truck beyond a predetermined steering angle.

A non-zero slope threshold means a slope other than the horizontal floor. There? allows you to avoid a potentially dangerous situation in which the loaded trolley? swerved onto a ramp.

On the undercarriage display 54, the maximum height and forward tilt are shown, so? the operator can? easily realize a safe operating area. Preferably, even the maximum rearward angle can be shown to the user in the display 54.

Figure 6 shows a possible implementation of the unit? controller 20. In one embodiment, the unit? controller 20 includes a processor 42, a memory 43, and an input/output (I/O) interface 41. The processor ? configured to run a control software stored on memory 43 to perform any of the functions of the unit? control 20 as described above. When executing the control software, processor 42 receives input from sensors 21-30 via input/output (LO) interface 41 and outputs control signals to actuators 31-34 also using the input/output interface. (LO) 41. Also other possible implementations of the unit? of control can be conceived, which include for example a plurality? of distributed processors or similar.

The above description of embodiments applying the innovative principles of the invention ? provided solely for the purpose of illustrating said principles and therefore is not to be construed as limiting the scope of the invention claimed herein.

For example, additional features can be added using data from sensors to prevent misuse and increase user comfort. of the operator.

For example, according to an additional optional feature, carriage 10 can have an automatic fork positioning function. While driving, it should be mandatory to have the forks in the low position with maximum rearward tilt angle. According to the forks auto-positioning function, the forklift operator can request (for example by pressing a button of the user interface 40) to automatically bring the load to the "running position", i.e. with the low position of the lifting element 13 and the maximum backward tilt angle of the mast 12. control 20 consequently acts on the lifting and tilting actuators 32, 31 when it receives the corresponding command from the user.

According to a further optional feature, the carriage 10 can have a function to avoid the impact of the gallows. Here, the height sensor can? be used to avoid a collision when the forks 13 reach the limit switch or the ground during its movement along the mast 12. Therefore, when the lifting element is approaching the limit switch along the mast, the unit? control 20 controls the lifting actuator in order to decrease the speed? lifting or lowering of the lifting element. There? allows to reduce the risk of vibrations of the lifting element, which can? bring the trolley 10 into an unstable situation.

According to a further optional feature, in addition to this?, the upright 12 can? include multiple stages, where each stage corresponds to a segment of the mast along which the movement of the fork ? caused by a stage actuator, such as a cylinder. Each end? of a segment to stage pu? cause a fork shock when the additional adjacent stage starts/stops moving. Preferably, the unit? controller 20 has stored information regarding the height of the end points and the height of the stage change. Using this stored information, the unit? control 20 pu? check the lift actuator to:

- stop a lift at the end of the mast's maximum stroke (ie maximum possible height of the lifting element 13 along the mast 12) or decrease the speed? lifting when approaching this position of the lifting element;

- stopping a lowering function when the fork reaches the ground (ie the lowest possible position of the lifting element 13 along the mast 12); -reduce the speed? of the movement of lowering and lifting when the height of the fork ? close to the stage change along pillar 12.

Preferably, the cart can? include an additional auto-positioning function when the trolley starts. In fact, after loading, the operator often forgets to raise the forks a little to avoid them scraping on the ground. As soon as the operator begins to move, the unit? of control 20 controls the position of the fork 13. If the fork 13 ? on the ground, the unit? controller 20 automatically controls the relevant actuators to lift and tilt back the mast to prevent fork scraping.

Claims (15)

1. An industrial cart (10) including: -a frame (11), - a lifting element (13) for lifting a load (14), the lifting element being mounted on the mast in a sliding manner along the mast, - a lifting actuator (32) configured to move the lifting element along the upright, - a tilt actuator (31) configured to tilt the mast with respect to the frame, -a unit? controller (20) configured to control the lift actuator and the tilt actuator, -a load sensor (21) to detect the load weight (W) on the lifting element (13) and emit to the unit? control (20) load information indicating the detected load weight, e - a tilt angle sensor (22) to detect the tilt angle (?) of the mast with respect to the chassis and emit to the unit? control information about a tilt angle indicating the detected tilt angle, -a height sensor (23) for detecting the height (Hw) of the lifting element (13) relative to the mast and outputting height information indicating the detected height of the lifting element, characterized by further comprising an inclination sensor (27) configured to detect an inclination (a) of the industrial truck with respect to a horizontal plane and output inclination information indicating the inclination detected to the unit? control, in which the unit? control (20) ? configured: - to control the lifting actuator by limiting the lifting height of the lifting element below a maximum allowable lifting height (Hmax) of the lifting element based on the tilt information, load information and information about a tilt angle, e - to control the tilt actuator by limiting the tilt angle below a maximum permissible forward tilt angle (?max,f) of the mast based on the tilt information, load information and height information . 2. An industrial cart (10) according to claim 1, wherein the unit? control ? configured to control the tilt actuator (31) by limiting the tilt angle between the maximum permitted forward tilt angle (?max,f) of the mast (12) and a maximum permitted rearward tilt angle (?max ,b) of the mast calculated from the slope information, load information and height information. 3. An industrial trolley (10) according to claims 1 or 2, wherein the unit? control (20) ? configured to control the lift actuator by limiting the maximum allowable lift height (Hmax) of the lifter (13) to a value calculated based on tilt information, load information and information about a tilt angle. 4. An industrial truck (10) according to any one of claims 1 to 3, wherein the unit? control (20) ? configured: -to control the lifting actuator (32) by limiting the maximum allowable lifting height (Hmax) of the lifting element (13) to a value calculated only based on the tilt information, load information and information on a swing angle e -to control the tilt actuator (31) by limiting the maximum allowable forward tilt angle (?max,f) of the mast (12) to a value calculated only from the tilt information, load information and information of height. 5. An industrial trolley (10) according to any of the preceding claims, wherein the unit? control (20) ? configured to generate one or more? control values using a mathematical model of the industrial truck to which tilt information, load information, height information and information about a tilt angle are entered, the unit? controller being configured to control the lift actuator and/or the tilt actuator based on one or more? control values. 6. An industrial trolley (10) according to claim 5, wherein one or more control values include one or more? of the following: -the maximum permitted lifting height (Hmax), -the maximum forward tilt angle allowed (?max,f), -the maximum rearward angle allowed (?max,b), -the maximum permitted load weight (Wmax), and/or -an indication that a user-commanded lift or tilt operation is bringing the industrial truck close to an unstable condition. 7. An industrial trolley (10) according to any one of claims 5-6, wherein the unit? control (20) ? configured to generate one or more? control values by entering the mathematical model of the industrial truck a speed? of the wheels, a longitudinal acceleration, a lateral acceleration and information on a steering angle detected by respective sensors (24, 25, 28, 29) of the industrial truck, the unit? control (20) being configured to control the speed? of the trolley, the acceleration of the trolley and the braking of the carrlo on the basis of one or more? go check. 8. An industrial trolley (10) according to claim 7, wherein one or more control values include one or more? of the following: -the maximum speed? allowed forward, -the maximum speed? backwards allowed, -the maximum permissible forward acceleration, -the maximum acceleration allowed backwards, -the maximum deceleration of forward/reverse braking. An industrial truck according to any one of claims 5-8, further comprising a rear axle sensor (30) for detecting a load weight on a rear axle of the industrial truck; in which the unit? control (20) ? configured to estimate the longitudinal position of the load (14) on the lifting element based on the load weight detected by the load sensor (21) to detect the load weight on the lifting element (13) and the detected load weight from the rear axle sensor (30), in which the unit? control (30) ? configured to generate one or more? control values by entering the estimated longitudinal position of the load (14) to the mathematical model. 10. An industrial trolley (10) according to any of the preceding claims, wherein the unit? control ? configured to stop a user commanded lift and/or pan/tilt operation when a control value generated by the unit? control (20) indicates that the industrial trolley (10) ? close to a condition where the industrial truck rolls over backwards around the rear axle. 11. An industrial trolley (10) according to any of the preceding claims, wherein the unit? control (20) ? configured to calculate the maximum allowable lift height (Hmax) and the maximum allowable forward tilt angle (?max,f) continuously and repeatedly during operation of the industrial truck. 12. An industrial truck (10) according to any one of claims 1-8 and 10-11, wherein, when the wheels of the industrial truck are in a stationary condition, the unit? control (20) ? configured to control the lift actuator and the tilt actuator only based on the following inputs: load information, tilt information, height information, tilt information, and a command entered by a user using a user interface (40). 13. An industrial truck (10) according to any of the preceding claims, wherein the inclination sensor is a unit? inertial measurement device, IMU (26), configured to also detect a lateral acceleration (28) and a longitudinal acceleration (29) of the industrial truck and output lateral acceleration information indicating the detected lateral acceleration and longitudinal acceleration information indicating ' longitudinal acceleration detected to the unit? controller (20) for controlling an operation of the carriage in a dynamic condition. 14. An industrial trolley (10) according to any of the preceding claims, wherein the unit? control (20) ? also configured, when the industrial truck begins to pick up a load, to calculate a maximum allowable load weight (Wmax) based on tilt information, information about a tilt angle and height information, and to control the actuator lift (32) stopping a lifting operation while the load (14) is being picked up when the difference between the load weight (W) detected by the load sensor (21) and the calculated maximum permissible load weight (Wmax) ? below a predetermined threshold. 15. An industrial trolley (10) according to any of the preceding claims, wherein the unit? control (20) ? is also configured to reduce the speed to zero? of the trolley if the following conditions are verified simultaneously: - the inclination information indicates an inclination of the trolley above a predetermined inclination threshold which ? different from zero, - the load information indicates a load weight above a predetermined load threshold which ? non-zero; And - a command entered by a user by means of a user interface (40) requests to steer the truck beyond a predetermined steering angle.