CN113072012B - Anti-rollover control method for counterweight type forklift - Google Patents

Anti-rollover control method for counterweight type forklift Download PDF

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CN113072012B
CN113072012B CN202110447580.9A CN202110447580A CN113072012B CN 113072012 B CN113072012 B CN 113072012B CN 202110447580 A CN202110447580 A CN 202110447580A CN 113072012 B CN113072012 B CN 113072012B
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forklift
oil cylinder
locking
fri
steering
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CN113072012A (en
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夏光
张华磊
夏岩
钱峰
陈建杉
刘贤阳
魏志祥
施展
汪韶杰
孙保群
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Hefei University of Technology
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Hefei University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/07504—Accessories, e.g. for towing, charging, locking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F17/00—Safety devices, e.g. for limiting or indicating lifting force
    • B66F17/003—Safety devices, e.g. for limiting or indicating lifting force for fork-lift trucks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/07568—Steering arrangements

Abstract

The invention discloses an anti-rollover control method for a counter-weight forklift, which is based on a mode that a robot stability criterion gravity Center projection point (COG) and a Foot rollover indication point (FRI) are combined to serve as a lateral stability evaluation index, the lateral stability degree of the forklift is judged by comparing the position relations of a ground reference point COG mass Center, an FPI mass Center and a support area, the lateral stability state of the forklift is divided into three stages, and different combined control methods of locking oil cylinders and active steering are utilized for different lateral stability states to achieve the anti-rollover effect.

Description

Anti-rollover control method for counterweight type forklift
Technical Field
The invention belongs to the field of forklifts, and relates to a rollover prevention control method for a counterweight type forklift.
Background
The counter-weight forklift is widely applied to industries such as manufacturing industry, warehousing industry, transportation industry and the like as a common goods carrying vehicle, is more and more widely used in the current highly-developed economic society, and gradually becomes an indispensable part for industrial development. Therefore, the technical requirements of the forklift are more and more strict, and accidents such as rollover and the like are inevitable in the using process of the forklift, so that in order to reduce the occurrence of the accidents, the rollover prevention capability of the forklift needs to be improved, and the driving safety is enhanced.
The two biggest defects of the traditional domestic forklift are respectively poor transverse stability of a forklift body and incapability of realizing steering synchronization of a steering system, the forklift is easy to turn on one's side when the forklift turns at a high speed due to poor transverse stability, and the corresponding relation between the positions of a steering wheel and wheels is disordered due to leakage of oil liquid in the steering system. The domestic research on the rollover prevention of the forklift and the synchronous steering of the steering system is still in a primary stage, the control mode and the control process are rough, the core technology is not involved, and the research results do not meet the requirement of product loading.
Disclosure of Invention
In order to avoid the technical problems, the invention provides a rollover prevention control method of a balance weight type forklift, so that the attitude change of a forklift body can be inhibited by adopting a rollover prevention control strategy of combined control of a locking oil cylinder and active steering, and the optimal rollover prevention effect is achieved.
The invention adopts the following technical scheme for solving the technical problems:
the invention discloses a rollover prevention control method for a counter-weight forklift, which is characterized by comprising the following steps of:
step 1, determining evaluation indexes of the transverse stability of the forklift, comprising the following steps: the robot stability criterion gravity center projection point is recorded as a COG (chip on glass) mass center, and the foot turning indication point is recorded as an FRI (field replaceable interface) mass center;
step 2, determining the COG (chip on glass) mass center (x) of the forklift by using the formula (1) and the formula (2) respectivelyCOG,yCOG) And FRI centroid (x)FRI,yFRI)：
Figure BDA0003037507440000011
Figure BDA0003037507440000021
In the formulas (1) and (2), a is the distance from the combined mass center of the forklift to the front axle, and hgHeight, m, of the combined centre of mass of the truck and the ground1Is the unloaded body mass of the fork-lift truck, L0Is the distance between the unloaded centre of mass of the fork truck and the front axle, h2Height of unloaded centre of mass, m2Is the mass of the goods, c is the horizontal distance from the center of mass of the goods to the front end of the portal frame, h1Is the height of the center of mass of the goods, d is the distance from the front end of the portal to the front shaft, vx、vyIs the component on the X, Y axis of the absolute velocity of the combined centre of mass of the truck, v'x、v′yAre each vx、vyFirst derivative of, a'x，a′yThe components of the absolute acceleration of the combined mass center of the forklift on the X, Y axis, omega is the yaw velocity of the forklift, hxFor the height of the articulated shaft of the steering axle, Ixm1、Ixm2Respectively are inertia products of the whole vehicle and the goods around YZ axes respectively;
determining the boundary Y of the support area delta ABE before the locking of the locking oil cylinder in the Y-axis direction by using the formula (3) and the formula (4)max1And the boundary Y of the support area □ ABCD in the Y-axis direction when the locking cylinder is lockedmax2To determine the support area position:
Figure BDA0003037507440000022
Figure BDA0003037507440000023
in the formulae (3) and (4), B1、B2Respectively the wheel track of front and rear wheels of the forklift;
and 3, judging the transverse stable state of the forklift according to the relationship between the COG (chip on glass) mass center and the FRI (fiber reinforced plastics) mass center and the position of the supporting area respectively, wherein the method comprises the following steps: static stable state, dynamic stable state, and dynamic unstable state;
step 4, designing a locking oil cylinder and an active steering system;
step 5, constructing the anti-rollover controller based on the variable domain self-adaptive fuzzy control method, which comprises the following steps: a locking oil cylinder variable-discourse-domain self-adaptive fuzzy controller and an active steering variable-discourse-domain self-adaptive fuzzy PID controller;
and 6, implementing a corresponding anti-rollover control strategy of joint control of the locking oil cylinder and the active steering system by using the anti-rollover controller according to different transverse stable states of the forklift.
The invention also discloses a rollover prevention control method for the counter-weight forklift,
the transverse stable state of the forklift in the step 3 is judged as follows:
the static steady state is: the COG centroid and the FRI centroid are both located in the position of the support region, namely yCOG|≤ymax、|yFRI|≤ymax(ii) a Wherein, ymaxIndicates the boundary ymax1And a boundary ymax2Any one of the boundaries;
the dynamic steady state is: COG centroid outside the support region boundary, but FRI centroid within the support region position, i.e. | yCOG|＞ymax、|yFRI|≤ymax；
The dynamic unstable state is: the COG centroid and the FRI centroid are both positioned outside the supporting region, namely | yCOG|＞ymax、|yFRI|＞ymax。
The design process of the locking oil cylinder in the step 4 is as follows:
two ends of the locking oil cylinder are respectively hinged with the vehicle body and the rear axle, so that an upper cavity and a lower cavity of the locking oil cylinder are communicated between the vehicle body and the rear axle, and a locking electromagnetic valve is arranged on an oil way connected with the locking oil cylinder and the oil pump;
when the locking oil cylinder performs anti-rollover control, the load force of a piston rod of the locking oil cylinder is used as a power source of the locking oil cylinder; if the piston rod is pressed, hydraulic oil flows from the lower cavity to the upper cavity, and the locking oil cylinder provides lateral supporting force for the vehicle body; if the piston rod is pulled, hydraulic oil flows from the upper cavity to the lower cavity, and the locking oil cylinder provides lateral damping force for the vehicle body;
when the locking oil cylinder is not controlled to prevent side turning, the locking electromagnetic valve is normally opened, and the vehicle body can normally swing around a hinge point.
The design process of the active steering system in the step 4 is as follows:
a steering wheel corner sensor (1) is arranged on a transmission shaft of a steering wheel and is used for collecting steering wheel corner signals when the steering wheel rotates;
a wheel corner sensor (2) is arranged on an extending section of a left piston rod of the steering oil cylinder and used for collecting wheel corner signals;
an oil inlet and an oil outlet of the steering oil cylinder are respectively connected with two ends of the oil drainage electromagnetic valve (3) in parallel and used for shunting oil liquid of the steering oil cylinder;
when the position of a supporting area where the forklift is in a transverse stable state reaches the trigger threshold y of active steeringmaxAnd when the steering oil cylinder is in a steering state, the oil drainage electromagnetic valve (3) is opened, so that the high-pressure oil path of the steering oil cylinder starts shunting oil drainage to weaken the steering response of the steering wheel to the rear wheels.
The construction process of the locking oil cylinder variable domain self-adaptive fuzzy controller in the step 5 is as follows:
step 5.1a, indicating the transverse position y of the point with the foot turnoverFRIIs measured by the expected error e and the lateral error variation e between the actual value and the expected value ofcTaking the current i of a locking electromagnetic valve of a locking oil cylinder as an input variable and taking the current i as an output variable;
the expected value error e and the error change e are determined by equations (5) and (6), respectivelyc：
Figure BDA0003037507440000031
Figure BDA0003037507440000041
In the formulae (5) and (6),
Figure BDA0003037507440000042
is the trigger threshold for the dynamic steady state,
Figure BDA0003037507440000043
are each yFRI、
Figure BDA0003037507440000044
The first derivative of (a);
step 5.2a, determining two input quantization factors K by using an equation (7) and an equation (8) respectivelye、KecAnd the output scale factor Ki：
Figure BDA0003037507440000045
Figure BDA0003037507440000046
In formulae (7) and (8), eminAnd emaxRespectively representing the maximum and minimum values of the error e of the desired value, ecminAnd ecmaxRespectively representing error variations ecMaximum and minimum values of iminAnd imaxRespectively representing the maximum value and the minimum value of the current i of a locking electromagnetic valve of the locking oil cylinder and forming a physical discourse range [ e ] of input and outputmin，emax]，[ecmin，ecmax]，[imin，imax]；
Step 5.3a, determining a fuzzy rule:
error in current expected value
Figure BDA0003037507440000047
When the forklift is in a dangerous working condition, the opening degree of the locking electromagnetic valve is reduced by reducing the current i so as to obtain larger lateral supporting force and improve the transverse stability;
error in current expected value
Figure BDA0003037507440000048
When the method is used, the forklift is indicated to be in a non-dangerous working condition, the opening degree of the locking electromagnetic valve is increased by increasing the current i so as to obtain relatively smaller lateral supporting force, so that the profiling function of the forklift is considered on the premise of avoiding the continuous deterioration of the transverse stability of the forklift, wherein,
Figure BDA0003037507440000049
triggering a threshold for a dynamic steady state;
step 5.4a, designing a scale factor pair physical discourse domain range [ emin，emax]，[ecmin，ecmax]，[imin，imax]And (3) adjusting:
determination of three scaling factors alpha of input and output by using equation (9)e1、αec1And beta1：
Figure BDA00030375074400000410
In the formula (9), αe1And alphaec1Error e and error variation e of input variable desired valuecStretch factor of beta1Is the scaling factor of the current i, t represents the independent variable and τ is the integral variable.
The design process of the active steering variable discourse domain self-adaptive fuzzy PID controller in the step 5 is as follows:
step 5.1b, determining the equivalent additional rear wheel steering angle beta of the active steering by using the formula (11)c：
Figure BDA00030375074400000411
In the formula (10), KpIs a proportionality coefficient, TbTo integrate the time constant, TdIs a differential time constant, eFRIError of expected value for FRI centroid;
by footTransverse position y of the turning-over indication pointFRIError e and lateral error variation e between the actual value and the desired value ofcAs input variables, with a proportionality coefficient KpIntegral time constant TbDifferential time constant TdA fuzzy rule is established for the output variable according to the fuzzy relation between the input variable and the output variable, thereby realizing the proportionality coefficient K according to the fuzzy rulepIntegral time constant TbDifferential time constant TdOnline adjustment of (2);
and 5.2b, determining the wheel rotation angle beta of the forklift by using the formula (11):
β＝βd-βc (11)
in the formula (11), betadWheel angle, beta, input for steering wheelcEquivalent additional rotation angles input for the active steering variable domain self-adaptive fuzzy PID controller;
and 5.3b, determining the trigger condition of the active steering variable domain adaptive fuzzy PID controller by using the formula (12):
Figure BDA0003037507440000051
and 5.4b, determining the PID controller parameters after fuzzification processing by using the formula (13):
Figure BDA0003037507440000052
in formula (13), K'p、T′i、T′dFor the final PID controller parameter, Kp0、Ti0、Td0For initially set PID controller parameter, Δ Kp、ΔTi、ΔTdIs the output quantity of the PID controller;
determination of five scaling factors alpha for input and output using equation (14)e2、αec2、βp、βdAnd betai：
Figure BDA0003037507440000053
The rollover prevention control strategy in the step 6 is as follows:
when the forklift is in a static stable state: the locking electromagnetic valve is completely opened, and a piston rod of the locking oil cylinder freely follows up to keep the profiling function of the forklift;
when the forklift is in a dynamic stable state: the opening degree of the locking electromagnetic valve is controlled by using a locking oil cylinder variable domain self-adaptive fuzzy controller so as to obtain different damping forces to support the vehicle body; if the transverse stability of the forklift continues to deteriorate and the forklift is about to break away from the dynamic stable state, closing the locking electromagnetic valve;
when the forklift is in a dynamic unstable state: after the locking oil cylinder is locked, if the state of the vehicle body is recovered to a static stable state, the active steering control is not carried out; and if the forklift reaches the dynamic stable state again, opening the oil drainage electromagnetic valve by using the active steering variable domain self-adaptive fuzzy PID controller to perform active steering intervention control.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, a robot stability research result is adopted, a Center Of Gravity projection point (COG) and a Foot turning Indicator (FRI) are used as forklift lateral stability evaluation indexes, and the problems Of the currently commonly used lateral stability evaluation indexes such as lateral Load Transfer Rate (LTR), TTR real-time rollover warning and Zero Moment Point (ZMP) can be effectively avoided;
2. according to the invention, the transverse stable state of the forklift is classified according to the relation between the COG (chip on glass) mass center, the FRI (fiber reinforced plastic) mass center and the supporting area of the ground reference point, and the transverse stable state of the forklift is divided into three stages: the control system is characterized by comprising a static stable state, a dynamic stable state and a dynamic unstable state, and a rollover prevention control strategy and a controller are designed on the basis, so that whether the forklift is in a safe working condition or not can be effectively judged;
3. in view of the defects caused by independent utilization of the locking oil cylinder or active steering control, the invention provides a rollover prevention strategy of combined control of the locking oil cylinder and the active steering, and the purpose of rollover prevention of the forklift under different stable states can be achieved;
4. the invention designs a locking oil cylinder and an active steering controller based on variable-discourse-domain self-adaptive fuzzy control, wherein the variable-discourse-domain fuzzy control is an anti-rollover control strategy which enables input and output discourse domains to be automatically adjusted along with the changes of input variables and output variables on the basis of a fuzzy controller, has the functions of increasing fuzzy control rules and improving the fuzzy control precision, and thus can ensure the profiling function and the steering reliability of the forklift to the maximum extent.
Drawings
FIG. 1 is a diagram of the calculation of the combined center of mass of a forklift truck according to the present invention;
FIG. 2.1 is a lateral dynamics model of the present invention;
FIG. 2.2 is a roll model of the present invention;
FIG. 3.1 is a force analysis diagram of a robot leg according to the present invention;
FIG. 3.2 is a force analysis diagram of the ankle and foot of the robot of the present invention;
FIG. 4 is a representation of a support region of the present invention;
FIG. 5.1 is a static steady state diagram of the present invention;
FIG. 5.2 is a dynamic steady state diagram of the present invention;
FIG. 5.3 is a dynamic instability state diagram of the present invention;
FIG. 6 is a schematic view of the lock-up cylinder of the present invention;
FIG. 7 is a schematic diagram of an active steering oil circuit of the present invention;
FIG. 8 is a block diagram of a variable-domain adaptive fuzzy controller for a locking cylinder according to the present invention;
FIG. 9 is a block diagram of the active steering control of the present invention;
fig. 10 is a schematic view of the rollover prevention control strategy of the present invention.
Detailed Description
In the embodiment, a control method for preventing the side-turning of the balance weight type forklift is used for realizing the side-turning prevention effect of the balance weight type forklift by adopting the locking oil cylinder and the active steering variable domain self-adaptive fuzzy controller in a combined control mode. The method comprises the following specific steps:
step 1, determining the evaluation indexes of the transverse stability of the forklift as follows: the robot stability criterion is a gravity center projection point, namely a COG (chip on glass) mass center, and a foot turning indication point, namely an FRI (foot turnover indicator) mass center;
step 2, determining the center of mass COG, the center of mass FRI and the position of a supporting area of the forklift;
step 2.1, calculating the combined center of mass position of the forklift through a synthesis method, as shown in figure 1:
according to the moment balance relation, the following equation is obtained:
(m2+m1)a＝m1L0-m2(c+d) (1)
(m2+m1)hg＝m2h1+m1h2 (2)
the combined centroid positions were:
Figure BDA0003037507440000071
Figure BDA0003037507440000072
wherein: h is a total ofgIs the combined centroid ground clearance; m is1The mass of the forklift body is no-load; l is0The distance between the no-load mass center and the front axle; h is2Is the unloaded centroid height; m is2Is the cargo quality; c is the horizontal distance from the center of mass of the goods to the front end of the portal; h is a total of1Is the height of the center of mass of the cargo; d is the distance from the front end of the door frame to the front shaft.
And 2.2, constructing a three-degree-of-freedom lateral-rolling dynamic model of the forklift, wherein the established transverse dynamic model is shown in a figure 2.1, and the lateral-rolling model is shown in a figure 2.2.
And establishing different side-tipping motion models according to the dynamic characteristic change of the whole vehicle before and after the locking of the locking oil cylinder.
First roll motion model: and locking the oil cylinder in an unlocked stage. The side-tipping axis of the forklift is a connecting line between the hinge point of the rear axle and the fixed connection point of the front axle. The roll model has 3 degrees of freedom, namely, the vehicle body rotates around a hinged rotating shaft, and the combined center of mass moves along the Y axis and rotates around the Z axis respectively.
The lateral equilibrium equation of motion:
Figure BDA0003037507440000081
yaw motion balance equation:
Figure BDA0003037507440000082
roll equilibrium equation:
Figure BDA0003037507440000083
the second side-tipping motion model: and locking the oil cylinder. And after the oil cylinder is locked, the forklift motion model is switched to a second side-tipping model. At the moment, the rear axle is fixedly connected with the frame, the whole vehicle becomes a rigid body, and the tilting axis becomes a connecting line of the grounding point of the single-side tire. At this time, the lateral motion balance equation becomes:
Figure BDA0003037507440000084
the roll equation of motion becomes:
Figure BDA0003037507440000085
wherein, the rotational inertia product contains the whole car of fork truck and goods two parts. As shown in equation (10).
Ix＝Ixm1+Ixm2；Iz＝Izm1+Izm2 (10)
When fork truck turned to, regard fork truck tire vertical deformation as spring deformation, then tire vertical acting force after the tire vertical deformation was:
Figure BDA0003037507440000086
ax＝v′x-ωvy；ay＝v′y+ωvx (12)
Figure BDA0003037507440000087
Fij＝Kαβij (14)
the component of the transverse acceleration of the center of mass of the forklift on the X, Y axis is shown as the formula (12), the calculation of the tire slip angle of the forklift is shown as the formula (13), and the wheel slip force is shown as the formula (14).
In the formula, m is the mass of the whole vehicle; m is1Vehicle body mass; a isyLongitudinal acceleration;
Figure BDA0003037507440000091
vehicle body roll angle acceleration; b is1、B2Respectively the front and rear wheel tracks; h isxThe height of a hinge shaft of the steering axle; l is the wheelbase; a. b is the horizontal distance from the combined centroid to the front axle and the rear axle respectively; omega is yaw angular velocity; beta is a1、β2Respectively are the outer and inner corners of the wheel; beta is aijA tire slip angle; fz11、Fz12Vertical force of front left and right wheels of the forklift is provided; fijIs the tire lateral force; v. ofx、vyIs the component of the combined centroid absolute velocity at axis X, Y; i isx、IzRespectively is the inertia product of the whole vehicle and the goods around the YZ axis and the XY axis; t isxVertical stiffness of the front wheel; kαTire cornering stiffness.
Step 2.3, the robot FRI calculation formula derivation process is carried out as follows:
according to Newton or Alembert's theorem, taking the moment for point O can yield:
Figure BDA0003037507440000092
as shown in fig. 3.2, the equation for the dynamic balance of the bare part of the robot foot is:
Figure BDA0003037507440000093
when dynamic items, as shown in FIG. 3.1
Figure BDA0003037507440000094
aiWhen 0, the formula (16) is an expression of the static balance of the foot. If only the tangent vector portion is taken, the static balance expression becomes:
(τ1+FO1×R1-FG1×m1g)t＝0 (17)
the angular momentum balance equation of the robot is as follows:
Figure BDA0003037507440000095
the tangent vector portion can be obtained by combining equation (17) and equation (18):
Figure BDA0003037507440000096
when equation (19) is expanded according to the coordinate algorithm, the following equations are obtained:
Figure BDA0003037507440000101
the formula (20) is a calculation formula of FRI on XY axes. M, R is the reaction force and moment of the ground to the foot, respectively; m isi、Gi、ai、HiMass, mass center position, acceleration and mass center angular momentum of each part; tau is1The moment acting on the foot by the leg is the bare moment.
Step 2.4, deducing a calculation formula of the FRI of the forklift as follows:
substituting the formula (20) into the three-degree-of-freedom side-tipping model according to the characteristics of FRI, wherein the calculation formula of the FRI mass center and the COG mass center of the forklift can be obtained by neglecting the pitching motion of the forklift because the forklift has no suspension structure as follows:
determining the COG (center of mass) x of the forklift by using an equation (21) and an equation (22) respectivelyCOG,yCOG) And FRI centroid (x)FRI,yFRI)：
Figure BDA0003037507440000102
Figure BDA0003037507440000103
In the formulas (21) and (22), a is the distance from the combined center of mass of the forklift to the front axle, and hgFor the combined centre of mass of the fork truck, m1For the mass of the unloaded body of the fork-lift truck, L0Is the distance between the unloaded center of mass and the front axle, h2Height of center of mass, m, at no load2Is the mass of the goods, c is the horizontal distance from the center of mass of the goods to the front end of the portal frame, h1Is the height of the center of mass of the goods, d is the distance from the front end of the portal frame to the front shaft, vx、vyIs the absolute speed of the combined mass center of the forklift at X, Y axle component v'x、v′yAre each vx、vyOf a'x，a′yThe absolute acceleration of the combined center of mass of the forklift is X, Y axis components, omega is the yaw velocity of the forklift, and hxFor steering axle articulation shaft height, Ixm1、Ixm2The inertia products of the whole vehicle and the goods around the YZ axis are respectively.
As shown in fig. 4, which is a characteristic diagram of the support area, the boundary Y of the support area Δ ABE before the lockup of the lockup cylinder in the Y-axis direction is determined by using equations (23) and (24), respectivelymax1And the boundary Y of the deadlocked support area □ ABCD of the deadlocked cylinder in the Y-axis directionmax2To determine the support area position:
Figure BDA0003037507440000111
Figure BDA0003037507440000112
in formulae (23) and (24), B1、B2Respectively the wheel track of front and rear wheels of the forklift. In the following step ymax1、ymax2Unify with ymaxRepresents;
step 3, dividing the transverse stable state of the forklift into three stages according to the position relation between the ground reference points COG and FRI and the supporting area: static steady state, dynamic unstable state. The three states are defined as follows:
as shown in fig. 5.1, the static steady state of the forklift is as follows: COG and FRI are both located in the support region, i.e. | yCOG|≤ymax、|yFRI|≤ymax. In this state, the speed and the acceleration of the whole vehicle are small, the resultant force or resultant moment acting on the whole vehicle is zero, and the running state of the forklift is safest and mostly occurs in the running working conditions of low speed and small turning angle. Wherein, ymaxIndicates the boundary ymax1And a boundary ymax2Any one of the boundaries;
as shown in fig. 5.2, the dynamic steady state of the forklift is as follows: COG is located outside the support zone boundary, but FRI is located within the support zone, i.e. | yCOG|＞ymax、|yFRI|≤ymax. In this state, the resultant force and resultant moment of the total gravity and the total inertia of the whole forklift can be balanced, and the forklift cannot roll over. The closer the FRI is to the support zone boundary the worse the lateral stability, when the FRI is on the support zone boundary the forklift is in a critical stable state.
As shown in fig. 5.3, the dynamic unstable state of the forklift is as follows: COG, FRI both located outside the support region, i.e. | yCOG|＞ymax、|yFRI|＞ymax. In this state, the moment of the whole vehicle cannot be balanced, and the vehicle turns over.
Step 4, designing a locking oil cylinder and an active steering system;
step 4.1, designing a locking oil cylinder as follows:
as shown in fig. 6, two ends of the locking oil cylinder are hinged to the vehicle body and the rear axle respectively, so that an upper cavity and a lower cavity of the locking oil cylinder are communicated between the vehicle body and the rear axle, and an oil path connected with the locking oil cylinder and the oil pump is provided with a locking electromagnetic valve;
when the locking oil cylinder is used for anti-rollover control, the load force of a piston rod of the locking oil cylinder is used as a power source of the locking oil cylinder, when the piston rod is pressed, hydraulic oil flows from the lower cavity to the upper cavity, and the locking oil cylinder provides lateral supporting force for a vehicle body; when the piston rod is pulled, hydraulic oil flows from the upper cavity to the lower cavity, and the locking oil cylinder provides lateral damping force for the vehicle body;
when the locking oil cylinder is not controlled to prevent side turning, the locking electromagnetic valve is normally opened, and the vehicle body can normally swing around a hinge point.
And 4.2, designing an active steering system as follows:
as shown in fig. 7, a steering wheel angle sensor 1 is disposed on a transmission shaft of a steering wheel and is used for collecting a steering wheel angle signal when the steering wheel rotates;
a wheel corner sensor 2 is arranged on an extending section of a left piston rod of the steering oil cylinder and used for collecting wheel corner signals;
an oil inlet and an oil outlet of the steering oil cylinder are respectively connected with two ends of the oil drainage electromagnetic valve 3 in parallel and are used for shunting oil liquid of the steering oil cylinder;
when the transverse stable state of the forklift reaches the active steering triggering threshold value, the oil drainage electromagnetic valve 3 is opened, so that the high-pressure oil way of the steering oil cylinder starts shunting oil drainage to weaken the steering response of the steering wheel to the rear wheels.
Step 5, constructing the anti-rollover controller based on the variable domain self-adaptive fuzzy control method, which comprises the following steps: a locking oil cylinder variable domain self-adaptive fuzzy controller and an active steering variable domain self-adaptive fuzzy PID controller.
As shown in fig. 8, the variable domain adaptive fuzzy controller for the lockup cylinder is designed as follows:
step 5.1a, indicating the transverse position y of the point with the foot turnoverFRIIs desired error e sum between actual value and desired valueLateral error variation ecTaking the current i of a locking electromagnetic valve of a locking oil cylinder as an input variable and taking the current i as an output variable;
determining the error e and the error change e of the expected value by using the formula (25) and the formula (26) respectivelyc：
Figure BDA0003037507440000121
Figure BDA0003037507440000122
In the formula (I), the compound is shown in the specification,
Figure BDA0003037507440000123
for the dynamic steady state trigger threshold, 0.8y is taken in this embodimentmax1、2；
Figure BDA0003037507440000124
Are each yFRI、
Figure BDA0003037507440000125
The first derivative of (a);
step 5.2a, respectively determining an input quantization factor and an output scale factor by using a formula (27) and a formula (28):
Figure BDA0003037507440000126
Figure BDA0003037507440000127
in the formula, the input and output physical discourse range is [ emin，emax]，[ecmin，ecmax]，[imin，imax]The ambiguity fields are all taken as [ -10, 10 [)](ii) a Determining the input and output physical discourse domain according to the structural characteristics of the forklift: because the mass center moves forwards under the full-load working condition, y is at the momentΔABEUp to 498mm, the physical domain of E is [0, 498 ]]mm, domain of EC [ -200, 200]mm·s-1And I has a physical discourse domain of [0.03, 1.05]A。
Step 5.3a, determining the fuzzy rule as follows:
error in current expected value
Figure BDA0003037507440000131
When the forklift is in a dangerous working condition, the opening degree of the locking electromagnetic valve is reduced by reducing the current i so as to obtain larger lateral supporting force and improve the transverse stability;
error in current expected value
Figure BDA0003037507440000132
When the forklift is in a non-dangerous working condition, the opening degree of the locking electromagnetic valve is increased by increasing the current i so as to obtain relatively smaller lateral supporting force, so that the forklift can consider the profiling function of the forklift on the premise of avoiding the continuous deterioration of the lateral stability, wherein,
Figure BDA0003037507440000133
expressed as a dynamic steady state trigger threshold; in this example,. DELTA.y＝0.8ymax。
Step 5.4a, designing expansion factor to adjust the domain of discourse: a variable discourse domain self-adaptive fuzzy control block diagram of the locking oil cylinder is shown in FIG. 9; the controller has two input variables and three output variables, wherein the input variables are the transverse position y of the foot turnover indicating pointFRIError e and rate of change of error e between actual and expected valuescThe output variables are e, ecAnd a variable universe scaling factor alpha corresponding to the control current ie、αec、β。
The scale factor domain adjustment rule is as follows: when the feedback error and the error change rate of the forklift dynamic model are large, the system is adjusted greatly, the transverse stability is improved, the universe of input variables is enlarged in a small range, and the universe of output variables is unchanged; when the feedback error and the error change rate of the forklift dynamic model are small, the discourse area of input and output variables should be reduced in order to ensure that the control is not overshot and the copying capability of the forklift body is weakened.
The input-output scaling factor is determined using equation (29):
Figure BDA0003037507440000134
in the formula (29), αe1And alphaec1Error e and error variation e of input variable desired valuecStretch factor of beta1And is a scaling factor of the current i, t represents an independent variable, and tau is an integral variable.
Determining the theory domain after being adjusted by the variable theory domain controller as Xe＝αe[-E，E]、Xec＝αec[-EC，EC]、Y＝β[-U，U]，αe、αecβ is the scaling factor, E, EC and U are the respective domains of concern when no adjustment is made to the controller.
As shown in FIG. 9, the active steering variable domain adaptive fuzzy PID controller design proceeds as follows:
step 5.1b, determining the equivalent additional rear wheel steering angle beta of the active steering by using the formula (30)c：
Figure BDA0003037507440000135
In the formula (30), KpIs a proportionality coefficient, TiAs integration time constant, TdIs a differential time constant, eFRIFRI expected value error.
Error e and error change e of the actual value and the expected value of the transverse position of the foot overturning pointcAs input variables, with Kp、Ti、TdMaking fuzzy rules for the output variables by referring to the fuzzy relation between the input variables and the output variables, and finally realizing K according to the fuzzy rulesp、Ti、TdOn-line adjustment of (2).
And 5.2b, determining the wheel rotation angle beta of the forklift by using the formula (31):
β＝βd-βc (31)
in the formula (31), betadWheel angle, beta, input for steering wheelcAn equivalent additional turning angle input for the active steering controller;
and 5.3b, determining the active steering control triggering condition by using the formula (32):
Figure BDA0003037507440000141
step 5.4b, adding Kp、Ti、TdAnd performing variable domain adaptive fuzzy adjustment. Error e and error change e of the actual value and the expected value of the transverse position of the foot overturning pointcAs input variables, with Kp、Ti、TdMaking fuzzy rules for the output variables by referring to the fuzzy relation between the input variables and the output variables, and finally realizing K according to the fuzzy rulesp、Ti、TdIn-line adjustment of
The specific fuzzy rule is as follows:
when the error e is too large, K should be increased to increase the response speed of the active steering systemp(ii) a To limit the error rate
Figure BDA0003037507440000143
Should take a smaller Td(ii) a To prevent overshoot of the system, T is takeni＝0。
When the error e is moderate, a smaller K is required to improve the response speed of the systempAnd since the system response speed is Td、TiThe value of (2) has a large influence, and a proper T is also selectedd、TiIf the value is too large, integral saturation will occur, and if the value is too small, the response speed of the system will be reduced.
When the error e is small, K is used to ensure the system has excellent stability and robustnessp、TiThe value should be as large as possible, but the problem of system oscillation is considered, so TdIs particularly important, generally TdIs inversely proportional to the magnitude of the error e.
And 5.5b, determining the PID controller parameters after fuzzification processing by using a formula (33):
Figure BDA0003037507440000142
in the formula (33), Kp、Ti、TdFor the final control parameter, Kp0、Ti0、Td0For initial setting parameters, Δ Kp、ΔTi、ΔTdIs the fuzzy controller output.
After the fuzzy PID controller is established, performing expansion and contraction on a basic domain, performing domain expansion and contraction by adopting a method for adjusting a quantization factor and a scale factor, and determining that an expansion and contraction factor is selected as follows:
Figure BDA0003037507440000151
and 6, implementing a corresponding anti-rollover control strategy of joint control of the locking oil cylinder and the active steering system by using the anti-rollover controller according to different transverse stable states of the forklift. Specifically, as shown in fig. 10, the anti-rollover control strategy of the combined control of the locking cylinder and the active steering is as follows:
the method controls the locking oil cylinder, if the locking oil cylinder effectively inhibits the deterioration of the posture of the vehicle body, an ideal anti-rollover effect is achieved, and the active steering is not started. And if the locking oil cylinder cannot meet the requirement of preventing side turning, the system continues to carry out active steering control. Therefore, the steering angle and the profiling capability of the vehicle can be kept from being lost in the original driving purpose, and the purpose of preventing rollover can be achieved.
Static steady state: the locking electromagnetic valve is completely opened, and the piston rod of the oil cylinder freely follows up, so that the good profiling function of the forklift is kept;
dynamic steady state: and controlling the opening degree of the locking electromagnetic valve according to a designed control algorithm so as to obtain different damping forces to support the vehicle body. And if the lateral stability of the forklift continues to be deteriorated and the forklift is about to break away from the dynamic stable state, closing the locking electromagnetic valve. The whole vehicle is rigidly connected, the redistribution of force and moment is realized, and the support area is expanded into a trapezoidal support area formed by four wheel grounding points;
dynamic unstable state: and after the locking oil cylinder is locked, if the state of the vehicle body is recovered to a static stable state, the active steering control is not carried out. And if the forklift reaches the dynamic balance state again, opening the oil drainage electromagnetic valve to perform active steering intervention control.
Example (b): the control method for preventing the side turning of the forklift is applied to a certain type of 3-ton counter-weight forklift, the total weight m of the counter-weight forklift is 4639kg, and the weight m of a forklift bodys4300kg, and the whole vehicle rotates around the Z axisz＝6129kg·m2Moment of inertia of vehicle frame about X axis Ix＝3100kg·m2Height of center of mass h of vehicle bodys0.75m, the height of the center of mass of the rear axle is equal to the height h of the hinge point of the rear axler＝hu0The distance a between the front axle and the center of mass is 1m, the distance B between the rear axle and the center of mass is 0.7m, the wheel base B is 1m, and the maximum swing angle of the vehicle body relative to the rear axle is 0.265m
Figure BDA0003037507440000152
Selecting the position y of a vehicle body side inclination angle and a forklift foot overturning indicating pointFRIAs a target of the laterally stabilized observation, it is considered that
Figure BDA0003037507440000153
When the forklift is in a side-turning state,
Figure BDA0003037507440000154
example 1: when the forklift is fully loaded, the speed of the forklift is 10km/h, and the rotating speed of a steering wheel is 2r/s, the peak value of the roll angle is 8.56 degrees and yFRIThe peak value is 0.16, the locking oil cylinder is close to the rollover critical value, the locking oil cylinder can play a good role in preventing rollover, the active steering does not play a role, and the steering reliability is ensured.
Example 2: when the forklift is unloaded, the speed is 19km/h, and the rotating speed of a steering wheel is 0.8r/s, the peak value of the uncontrolled side dip angle is 14.22 degrees and yFRIThe peak value is 0.24, the values exceed the rollover critical value, and the forklift transmitsTurning the left side to the right side. The variable universe fuzzy locking oil cylinder control can play a certain role in preventing side turning, but the effect is general, and the peak value of the side inclination angle can still reach 6.42 degrees. When the variable-discourse-domain fuzzy locking oil cylinder and the active steering are used for combined control, the transverse dynamic stability of the forklift can be further improved, and the variable-discourse-domain fuzzy PID active steering has a smaller roll angle peak value than the fuzzy PID active steering, so that the rollover-simulating effect is achieved.
In conclusion, the control method for preventing the side-tipping of the forklift can ensure the steering stability of the forklift and prevent the side-tipping of the forklift.

Claims (7)

1. A rollover prevention control method for a counter-weight forklift is characterized by comprising the following steps:
step 1, determining evaluation indexes of the transverse stability of the forklift, comprising the following steps: the robot stability criterion gravity center projection point is recorded as a COG (chip on glass) mass center, and the foot turning indication point is recorded as an FRI (field replaceable interface) mass center;
step 2, determining the COG (chip on glass) mass center (x) of the forklift by using the formula (1) and the formula (2) respectivelyCOG,yCOG) And FRI centroid (x)FRI,yFRI)：
Figure FDA0003597813670000011
Figure FDA0003597813670000012
In the formulas (1) and (2), a is the distance from the combined center of mass of the forklift to the front axle, and hgHeight, m, of the combined centre of mass of the truck and the ground1Is the unloaded body mass of the fork-lift truck, L0Is the distance between the unloaded centre of mass of the fork truck and the front axle, h2Height of unloaded centre of mass, m2Is the mass of the goods, c is the horizontal distance from the center of mass of the goods to the front end of the portal frame, h1Is the height of the center of mass of the goods, d is the distance from the front end of the portal to the front shaft, vx、vyBeing combined centre of mass of fork-lift truckComponent of absolute velocity on the X, Y axis, v'x、v′yAre each vx、vyFirst derivative of, a'x，a′yThe components of the absolute acceleration of the combined mass center of the forklift on the X, Y axis, omega is the yaw velocity of the forklift, hxFor the height of the articulated shaft of the steering axle, Ixm1、Ixm2Respectively are inertia products of the whole vehicle and the goods around YZ axes respectively;
determining the boundary Y of the support area delta ABE before the locking of the locking oil cylinder in the Y-axis direction by using the formula (3) and the formula (4)max1And the boundary Y of the support area □ ABCD in the Y-axis direction when the locking cylinder is lockedmax2To determine the support area position:
Figure FDA0003597813670000013
Figure FDA0003597813670000014
in the formulae (3) and (4), B1、B2Respectively the wheel track of front and rear wheels of the forklift;
and 3, judging the transverse stable state of the forklift according to the relationship between the COG (chip on glass) mass center and the FRI (fiber reinforced plastics) mass center and the position of the supporting area respectively, wherein the method comprises the following steps: static stable state, dynamic stable state, and dynamic unstable state;
step 4, designing a locking oil cylinder and an active steering system;
step 5, constructing the anti-rollover controller based on the variable domain self-adaptive fuzzy control method, which comprises the following steps: a locking oil cylinder variable-discourse-domain self-adaptive fuzzy controller and an active steering variable-discourse-domain self-adaptive fuzzy PID controller;
and 6, according to different transverse stable states of the forklift, implementing a corresponding anti-rollover control strategy of joint control of the locking oil cylinder and the active steering system by using the anti-rollover controller.
2. The method as claimed in claim 1, wherein the lateral stable state of the forklift in the step 3 is determined as follows:
the static steady state is: the COG centroid and the FRI centroid are both located in the position of the support region, namely yCOG|≤ymax、|yFRI|≤ymax(ii) a Wherein, ymaxIndicates the boundary ymax1And a boundary ymax2Any one of the boundaries;
the dynamic steady state is: COG centroid outside the support region boundary, but FRI centroid within the support region position, i.e. | yCOG|＞ymax、|yFRI|≤ymax；
The dynamic unstable state is: the COG centroid and the FRI centroid are both positioned outside the supporting region, namely | yCOG|＞ymax、|yFRI|＞ymax。
3. The method for controlling the rollover prevention of the counterweight type forklift as recited in claim 1, wherein the design process of the locking cylinder in the step 4 is as follows:
two ends of the locking oil cylinder are respectively hinged with the vehicle body and the rear axle, so that an upper cavity and a lower cavity of the locking oil cylinder are communicated between the vehicle body and the rear axle, and a locking electromagnetic valve is arranged on an oil way connected with the locking oil cylinder and the oil pump;
when the locking oil cylinder performs anti-rollover control, the load force of a piston rod of the locking oil cylinder is used as a power source of the locking oil cylinder; if the piston rod is pressed, hydraulic oil flows from the lower cavity to the upper cavity, and the locking oil cylinder provides lateral supporting force for the vehicle body; if the piston rod is pulled, hydraulic oil flows from the upper cavity to the lower cavity, and the locking oil cylinder provides lateral damping force for the vehicle body;
when the locking oil cylinder is not controlled to prevent side turning, the locking electromagnetic valve is normally opened, and the vehicle body can normally swing around a hinge point.
4. The method as claimed in claim 1, wherein the design process of the active steering system in step 4 is as follows:
a steering wheel corner sensor (1) is arranged on a transmission shaft of a steering wheel and is used for collecting steering wheel corner signals when the steering wheel rotates;
a wheel corner sensor (2) is arranged on the overhanging section of the left piston rod of the steering oil cylinder and is used for collecting wheel corner signals;
an oil inlet and an oil outlet of the steering oil cylinder are respectively connected with two ends of the oil drainage electromagnetic valve (3) in parallel and used for shunting oil liquid of the steering oil cylinder;
when the position of a supporting area where the forklift is in a transverse stable state reaches the trigger threshold y of active steeringmaxAnd when the steering oil cylinder is in a steering state, the oil drainage electromagnetic valve (3) is opened, so that the high-pressure oil path of the steering oil cylinder starts shunting oil drainage to weaken the steering response of the steering wheel to the rear wheels.
5. The method for controlling the rollover prevention of the counter-weight forklift as recited in claim 1, wherein the locking cylinder variable domain adaptive fuzzy controller in the step 5 is constructed by the following steps:
step 5.1a, indicating the transverse position y of the point with the foot rolloverFRIIs measured by the expected error e and the lateral error variation e between the actual value and the expected value ofcTaking the current i of a locking electromagnetic valve of a locking oil cylinder as an input variable and taking the current i as an output variable;
the expected value error e and the error change e are determined by equations (5) and (6), respectivelyc：
Figure FDA0003597813670000031
Figure FDA0003597813670000032
In the formulae (5) and (6),
Figure FDA0003597813670000033
is the trigger threshold for the dynamic steady state,
Figure FDA0003597813670000034
are each yFRI、
Figure FDA0003597813670000035
The first derivative of (a);
step 5.2a, determining two input quantization factors K by using an equation (7) and an equation (8) respectivelye、KecAnd the output scale factor Ki：
Figure FDA0003597813670000036
Figure FDA0003597813670000037
In formulae (7) and (8), eminAnd emaxRespectively representing the maximum and minimum values of the error e of the desired value, ecminAnd ecmaxRespectively representing error variations ecMaximum and minimum values of iminAnd imaxRespectively representing the maximum value and the minimum value of the current i of a locking electromagnetic valve of the locking oil cylinder and forming a physical discourse range [ e ] of input and outputmin，emax]，[ecmin，ecmax]，[imin，imax]；
Step 5.3a, determining a fuzzy rule:
error in current expected value
Figure FDA0003597813670000038
When the forklift is in a dangerous working condition, the opening degree of the locking electromagnetic valve is reduced by reducing the current i so as to obtain lateral supporting force and improve the transverse stability;
error in current expected value
Figure FDA0003597813670000041
When the forklift is in a non-dangerous working condition, the opening degree of the locking electromagnetic valve is increased by increasing the current i so as to obtain lateral supporting force, so that the forklift has the profiling function of the forklift on the premise of avoiding the continuous deterioration of the transverse stability, wherein,
Figure FDA0003597813670000042
triggering a threshold for a dynamic steady state;
step 5.4a, designing a scale factor pair physical discourse domain range [ emin，emax]，[ecmin，ecmax]，[imin，imax]And (3) adjusting:
determination of three scaling factors alpha of input and output by using equation (9)e1、αec1And beta1：
Figure FDA0003597813670000043
In the formula (9), αe1And alphaec1Error e and error variation e of input variable desired valuecStretch factor of beta1Is the scaling factor of the current i, t represents the independent variable and τ is the integral variable.
6. The method as claimed in claim 1, wherein the design process of the active steering variable domain adaptive fuzzy PID controller in the step 5 is as follows:
step 5.1b, determining the equivalent additional rear wheel steering angle beta of the active steering by using the formula (11)c：
Figure FDA0003597813670000044
In the formula (10), KpIs a proportionality coefficient, TbAs integration time constant, TdIs a differential time constant, eFRIExpected value for FRI centroidAn error;
with transverse position y of the foot-rollover-indicating pointFRIError e and lateral error variation e between the actual value and the desired value ofcAs input variables, with a proportionality coefficient KpIntegral time constant TbDifferential time constant TdA fuzzy rule is established for the output variable according to the fuzzy relation between the input variable and the output variable, thereby realizing the proportionality coefficient K according to the fuzzy rulepIntegral time constant TbDifferential time constant TdOnline adjustment of (2);
and 5.2b, determining the wheel rotation angle beta of the forklift by using the formula (11):
β＝βd-βc (11)
in the formula (11), betadWheel angle, beta, input for steering wheelcEquivalent additional rotation angles input for the active steering variable domain self-adaptive fuzzy PID controller;
and 5.3b, determining the trigger condition of the active steering variable domain adaptive fuzzy PID controller by using the formula (12):
Figure FDA0003597813670000045
and 5.4b, determining the PID controller parameters after fuzzification processing by using the formula (13):
Figure FDA0003597813670000051
in formula (13), K'p、Ti′、T′dFor the final PID controller parameter, Kp0、Ti0、Td0For initially set PID controller parameter, Δ Kp、ΔTi、ΔTdThe output quantity of the PID controller;
determination of five scaling factors alpha for input and output using equation (14)e2、αec2、βp、βdAnd betai：
Figure FDA0003597813670000052
7. The method of claim 1 wherein said rollover prevention control strategy of step 6 is:
when the forklift is in a static stable state: the locking electromagnetic valve is completely opened, and a piston rod of the locking oil cylinder freely follows up to keep the profiling function of the forklift;
when the forklift is in a dynamic stable state: controlling the opening of a locking electromagnetic valve by using a locking oil cylinder variable domain self-adaptive fuzzy controller to obtain different damping forces to support a vehicle body; if the transverse stability of the forklift continues to deteriorate and the forklift is about to break away from the dynamic stable state, closing the locking electromagnetic valve;
when the forklift is in a dynamic unstable state: after the locking oil cylinder is locked, if the state of the vehicle body is recovered to a static stable state, the active steering control is not carried out; and if the forklift reaches the dynamic stable state again, opening the oil drainage electromagnetic valve by using the active steering variable domain self-adaptive fuzzy PID controller to perform active steering intervention control.
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