AGV vehicle operation control method in high-temperature environment and AGV vehicle

Abstract

The invention provides an AGV vehicle operation control method in a high-temperature environment and an AGV vehicle. The operation control method comprises the following steps that S1, thermal field distribution in a three-dimensional warehouse is solved according to a heat source; s2, the tire temperature of the AGV is detected through a sensor, and the tire temperatures of different positions are predicted through friction heat generation and a heat transfer formula; s3, determining a running speed limit value, an acceleration limit value and a braking distance according to the predicted temperature of the tire; and S4, according to the predicted temperature of the tire, or according to the predicted temperature of the tire, the driving speed limit value, the acceleration limit value and the braking distance, driving of the AGV is controlled, and safe braking is ensured. Prejudgment is performed by predicting the tire temperatures at different positions, so that the driving speed and acceleration of the AGV can be regulated and controlled in time, heat generated by friction is reduced, the tire temperature is prevented from further rising, and the driving safety is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of stereoscopic warehouse AGV vehicles, and particularly relates to a method for controlling the operation of an AGV vehicle in a high-temperature environment and an AGV vehicle. Background Art

[0002] For certain chemical substances, petroleum products, or easily viscous liquid substances, it may be necessary to maintain them in a certain temperature environment. Stereoscopic warehouses can be used to store foods after high-temperature processing, or raw materials that need to be maintained under high-temperature conditions. For example, certain candies, baked foods, etc. may need to maintain a certain temperature in the stereoscopic warehouse to maintain freshness.

[0003] The rubber material of the tire is prone to aging at high temperatures, resulting in the hardening of the rubber and the loss of elasticity. The hardened tire will reduce the friction with the road surface, resulting in a decrease in grip and an increased risk of slipping and skidding. In a high-temperature environment, the material of the tire may expand or deform. Especially after long-term high-speed driving, the shape of the tire will be affected. Tire deformation will affect driving stability and may cause the vehicle to deviate or lose control. In addition, in a high-temperature environment, the air pressure of the tire is prone to fluctuate, especially during emergency braking or long-term driving, and the air pressure change is more obvious. Both too high and too low air pressure will affect the controllability and safety of the vehicle.

[0004] After retrieval, there is no similar technical solution to the present invention disclosed. Summary of the Invention

[0005] To solve the technical problems existing in the prior art, the first aspect of the present invention is to provide a method for controlling the operation of an AGV vehicle in a high-temperature environment. By predicting the tire temperatures at different positions and making pre-judgments, it is convenient to timely adjust the driving speed and acceleration of the AGV, reduce heat generation due to friction, avoid further increase in tire temperature, and improve driving safety. In the second aspect, based on the same inventive concept, the present invention also provides an AGV vehicle based on the foregoing operation control method.

[0006] In an embodiment of the present invention, a method for controlling the operation of an AGV vehicle in a high-temperature environment includes the following steps: S1, obtaining the thermal field distribution in the stereoscopic warehouse according to the heat source; S2, using sensors to detect the tire temperature of the AGV vehicle, and predicting the tire temperatures at different positions through the heat generation due to friction and the heat transfer formula; S3, determining the driving speed limit, acceleration limit, and braking distance according to the predicted temperature of the tire; S4, controlling the driving of the AGV according to the predicted temperature of the tire, or according to the predicted temperature of the tire, the driving speed limit, acceleration limit, and braking distance, to ensure safe braking.

[0007] An AGV vehicle according to an embodiment of the present invention operates using an AGV vehicle operation control method. The AGV vehicle includes a vehicle body with tires and a cooling system. When the predicted temperature of the tires approaches the limit temperature, the cooling system operates to cool the tires. The cooling system includes a circulation pipeline built into the tires and a water supply device installed in the tires. The water supply device cools the tires by introducing circulating cold water into the circulation pipeline.

[0008] Compared with the prior art, the technical effects achieved by the relatively superior technical solution of the present invention include: 1. First, the present invention obtains the internal heat field distribution in the stereoscopic warehouse according to the heat source, predicts the tire temperature at different positions through the heat generation by friction and the heat transfer formula, determines the driving speed limit, acceleration limit and braking distance according to the predicted tire temperature, and then controls the driving of the AGV according to the predicted tire temperature, or according to the predicted tire temperature, as well as the driving speed limit, acceleration limit and braking distance, to ensure safe braking. By predicting the tire temperature at different positions and making a pre-judgment, it is convenient to timely adjust the driving speed and acceleration of the AGV, reduce the heat generation by friction, avoid the further increase of the tire temperature, and improve the driving safety.

[0009] 2. When the present invention controls the driving of the AGV according to the predicted tire temperature, the driving speed limit, acceleration limit and braking distance to ensure safe braking, first, according to the starting point, ending point and driving route, the driving process is divided into several stages: starting, linear acceleration, turning (if any), and linear deceleration braking. The speed, acceleration, driving distance and driving time of each stage are determined respectively. According to the established objective function and constraint relationship, the safe braking of the AGV driving is ensured. Description of the Drawings

[0010] Figure 1 is a flow chart of an AGV vehicle operation control method in a high-temperature environment according to an embodiment. Detailed Embodiments

[0011] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. Embodiment

[0012] This embodiment provides an AGV vehicle operation control method in a high-temperature environment. As Figure 1 shown, in a preferred embodiment, the operation control method includes the following steps: S1. Obtain the internal heat field distribution in the stereoscopic warehouse according to the heat source (such as areas like storage tanks with a constant temperature); S2. Detect the tire temperature of the AGV vehicle using sensors (such as infrared temperature sensors), and predict the tire temperatures at different positions through the formula of heat generation by friction and heat transfer; S3. Determine the driving speed limit, acceleration limit, and braking distance based on the predicted tire temperature; S4. Control the driving of the AGV vehicle according to the predicted tire temperature, or according to the predicted tire temperature, driving speed limit, acceleration limit, and braking distance to ensure safe braking.

[0013] In step S1 of the present invention, the method for obtaining the internal heat field distribution in the stereoscopic warehouse based on the heat source is as follows: , where, is the temperature in the stereoscopic warehouse, is the time, is the thermal diffusivity in the stereoscopic warehouse (different at different positions, such as the stored items, air, etc., which can be obtained through experiments or by looking up tables), is the Laplace operator of the temperature in the stereoscopic warehouse, is the heat source per unit volume (this value is 0 in the area without heat source).

[0014] The boundary conditions are: For the outer wall and ground of the stereoscopic warehouse, an adiabatic boundary condition is adopted , is the outer normal direction of the boundary; For the storage area, a fixed temperature boundary condition is adopted , is the storage temperature; For the storage area in the stereoscopic warehouse and the surrounding air, a radiation boundary condition is adopted where, is the radiative heat flux, is the radiative emissivity of the surface of the storage area, is the Stefan-Boltzmann constant, is the temperature of the surface of the storage area, is the ambient temperature around the storage area; For the places where there is ventilation and air flow between the stereoscopic warehouse and the surrounding environment, a convective boundary condition is adopted where, is the convective heat flux, is the air convection heat transfer coefficient, is the surface temperature of the convective area of the stereoscopic warehouse, is the ambient temperature outside the convective area.

[0015] When the present invention calculates the internal heat field distribution in the three-dimensional warehouse based on the heat source, it considers the temperature in the three-dimensional warehouse, the thermal diffusivity in the three-dimensional warehouse, the Laplace operator of the temperature in the three-dimensional warehouse, and the heat source per unit volume. Moreover, the outer wall and the ground of the three-dimensional warehouse adopt adiabatic boundary conditions, the storage area adopts fixed temperature boundary conditions, the storage area in the three-dimensional warehouse and the surrounding air adopt radiation boundary conditions, and the places where there is ventilation and air flow between the three-dimensional warehouse and the surrounding environment adopt convective boundary conditions. Different boundary conditions are adopted at different positions, and the obtained internal heat field distribution of the three-dimensional warehouse is more accurate.

[0016] In step S2 of the present invention, the method for calculating and predicting the tire temperatures at different positions through frictional heat generation and heat transfer formula is as follows: , Among them, is the density of the tire, c is the specific heat capacity of the tire material, is the tire temperature, is the heat conduction term, is the frictional heat generation between the tire and the ground, is the convective heat dissipation between the tire and the air, is the radiative heat dissipation of the tire to the outside; Take the maximum value of the tire temperatures at different positions as the predicted temperature of the tire .

[0017] Specifically, the heat conduction term , among which, is the thermal conductivity of the tire material, A is the surface area of the tire, is the temperature difference between the tire surface and the inside, is the thickness from the tire surface to the inside.

[0018] The frictional heat generation between the tire and the ground , among which, is the friction coefficient between the tire and the ground, N is the normal force between the tire and the ground, is the vehicle speed. The normal force between the tire and the ground , among which, is the weight of the AGV vehicle, is the weight of the goods on the AGV vehicle, and g is the acceleration due to gravity.

[0019] The convective heat dissipation between the tire and the air , among which, is the convective heat transfer coefficient between the tire surface and the air, is the tire surface temperature, is the temperature of the tire surrounding environment.

[0020] Radiative heat dissipation of the tire to the outside , where is the heat radiation rate of the tire surface temperature

[0021] When predicting the tire temperature at different positions through frictional heat generation and heat transfer formula in the present invention, not only the density of the tire, the specific heat capacity of the tire material, the tire temperature, and the heat conduction term are considered, but also the frictional heat generation between the tire and the ground, the convective heat dissipation between the tire and the air, and the radiative heat dissipation of the tire to the outside are considered. Finally, the highest value of the tire temperature at different positions is taken as the predicted temperature of the tire , making the predicted temperature at time t more accurate and anticipating in advance

[0022] In another preferred embodiment, when determining the friction coefficient between the tire and the ground, the measured temperature of the tire is judged (obtained by measurement through a sensor) whether it is higher than the upper limit of the safe temperature of the tire (the upper limit of the temperature to ensure the normal operation of the tire, which can be tested through a high-temperature test, generally 90 - 110 degrees Celsius). If it is not higher than the upper limit of the safe temperature of the tire, the friction coefficient between the tire and the ground takes the maximum friction coefficient . If it is higher than the upper limit of the safe temperature of the tire, then the friction coefficient between the tire and the ground is , where is the friction coefficient, which changes with the tire temperature and is inversely correlated with the tire temperature is the upper limit of the safe temperature of the tire

[0023] When determining the friction coefficient between the tire and the ground, the measured temperature of the tire is compared with the upper limit of the safe temperature of the tire. When the measured temperature is not higher than the upper limit of the safe temperature, it indicates that the tire can operate normally and the tire grip has not decreased, and the maximum friction coefficient is taken. On the contrary, when the measured temperature is higher than the upper limit of the safe temperature, it indicates that there is a possibility of a decrease in the tire grip affected by high temperature, and the friction coefficient between the tire and the ground is , making the calculation of the frictional heat generation between the tire and the ground more accurate

[0024] In step S3 of the present invention, the method for determining the driving speed limit, acceleration limit, and braking distance according to the predicted temperature of the tire is as follows Driving speed limit , where is the maximum speed of the tire at the upper limit of the safe temperature, which can be determined through experiments is the predicted temperature is the upper limit of the safe temperature of the tire, which can be determined through experiments is the limit temperature of the tire, which can be determined through experiments

[0025] Acceleration limit , where is the base acceleration, which is the maximum acceleration of the tire at the upper limit of the safe temperature and can be determined by experiments.

[0026] Braking distance , where is the braking distance at the predicted temperature , is the vehicle speed, and g is the acceleration due to gravity.

[0027] When determining the driving speed limit and acceleration limit of the AGV vehicle in the present invention, the predicted temperature of the tire, the upper limit of the safe temperature of the tire, and the limit temperature of the tire are considered. The difference between the limit temperature of the tire and the upper limit of the safe temperature of the tire is a fixed value. When the predicted temperature of the tire is greater than the upper limit of the safe temperature, the tire grip decreases, and the driving speed limit / acceleration limit is less than the maximum speed / maximum acceleration of the tire at the upper limit of the safe temperature, which is safer. Preferably, when the predicted temperature of the tire is less than or equal to the upper limit of the safe temperature, the driving speed limit / acceleration limit is equal to the maximum speed / maximum acceleration of the tire at the upper limit of the safe temperature.

[0028] In an implementation manner of step S4 of the present invention, the method for controlling the driving of the AGV according to the predicted temperature of the tire to ensure safe braking is as follows: when the predicted temperature is close to the limit temperature , cool down the tire to reduce its temperature, lower the maximum speed and maximum acceleration (for example, lower it to 0.9 times the driving speed limit and driving acceleration limit), reduce the heat generated by the friction between the tire and the ground, avoid continuous temperature rise, and improve driving safety; when the predicted temperature is lower than the limit temperature , drive at the maximum speed (i.e., the driving speed limit) and maximum acceleration (i.e., the driving acceleration limit) to facilitate rapid transfer of goods.

[0029] In another implementation manner of step S4 of the present invention, the method for controlling the driving of the AGV according to the predicted temperature of the tire, the driving speed limit, the acceleration limit, and the braking distance to ensure safe braking is as follows: Determine the starting point and ending point of the AGV, obtain the driving route, and judge whether the driving route is a straight line or has a turn. If it is a straight line, divide the driving process into three stages: starting, straight-line acceleration, and straight-line deceleration braking. If there is a turn, divide the driving process into four stages: starting, straight-line acceleration, turning, and straight-line deceleration braking; Starting stage: , where is the speed in the starting stage, is the acceleration of starting,t is the time, is the distance traveled during the starting phase, is the time taken during the starting phase, is the speed at the end of the starting phase.

[0030] Linear acceleration phase: , wherein, is the speed during the linear acceleration phase, is the acceleration during the linear acceleration phase, is the distance traveled during the linear acceleration phase, is the time taken during the linear acceleration phase, is the speed at the end of the starting phase, is the speed at the end of the linear acceleration phase.

[0031] Turning phase: The frictional force is greater than or equal to the centrifugal force to obtain the maximum speed and acceleration for maintaining stability during turning, , wherein, is the coefficient of friction between the tire and the ground, g is the acceleration due to gravity, is the turning radius of the AGV; then , wherein, is the turning angle, taking 90 degrees, is the turning speed, is the distance traveled during turning, is the time taken during turning.

[0032] Linear deceleration braking phase: , wherein, is the speed during the linear braking phase, is the acceleration during the linear braking phase, is the distance traveled during the linear braking phase, is the time taken during the linear braking phase.

[0033] Establish the objective function and constraint relationships: , wherein, , , and are weight coefficients, which can be set manually, for example, set to 0.6, 0.1, 0.2, and 0.1 respectively.

[0034] Constraint relationship: Distance traveled during the starting stage + Distance traveled during the linear acceleration stage + Distance traveled during turning + Distance traveled during the linear braking stage = Distance of the driving route d , The maximum speed during driving is less than or equal to the driving speed limit , The acceleration during driving is less than or equal to the acceleration limit , Distance traveled during the linear braking stage is less than or equal to the braking distance corresponding to the predicted temperature when .

[0035] According to the predicted temperature of the tire, the driving speed limit, the acceleration limit and the braking distance, the present invention controls the driving of the AGV to ensure safe braking. First, according to the starting point, the end point and the driving route, the driving process is divided into several stages including starting, linear acceleration, turning (if any), and linear deceleration braking. The speed, acceleration, driving distance and driving time of each stage are determined respectively. According to the established objective function and constraint relationship, the safe braking of the AGV driving is ensured.

[0036] Embodiment 2 This embodiment provides an AGV vehicle operating by using the operating control method of Embodiment 1. The AGV vehicle includes a vehicle body with tires and a temperature reduction system. During driving, when the predicted temperature approaches the limit temperature , the temperature reduction system works to cool the tires, reduce the temperature of the tires, and at the same time lower the maximum speed and maximum acceleration of the AGV driving to ensure the safe driving of the AGV. Specifically, the temperature reduction system includes a circulation pipeline built in the tire and a water supply device installed in the tire (the water supply device is provided with a heat insulation layer outside to insulate heat). The water supply device cools the tire by introducing circulating cold water into the circulation pipeline. The cooled water enters another water storage tank for temporary storage and is recycled after cooling. The principle of the temperature reduction system is the same as the way of using circulating cold water for temperature reduction in the prior art, which is the prior art and will not be elaborated here.

[0037] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and purpose of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for controlling the operation of an AGV vehicle in a high-temperature environment, characterized in that It includes the following steps: S1. Obtain the internal heat field distribution in the stereoscopic warehouse according to the heat source; S2. Use sensors to detect the tire temperature of the AGV vehicle, and predict the tire temperature at different positions through the heat generation by friction and the heat transfer formula; S3. Determine the driving speed limit, acceleration limit and braking distance according to the predicted tire temperature; S4. Control the driving of the AGV according to the predicted tire temperature, or according to the predicted tire temperature, driving speed limit, acceleration limit and braking distance to ensure safe braking.

2. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 1, characterized in that, In step S1, the method for obtaining the internal heat field distribution in the stereoscopic warehouse according to the heat source is: ， Among them, is the temperature in the stereoscopic warehouse, is the time, is the thermal diffusivity in the stereoscopic warehouse, is the Laplace operator of the temperature in the stereoscopic warehouse, is the heat source per unit volume; The boundary conditions are: The outer wall and floor of the three-dimensional warehouse adopt adiabatic boundary conditions , is the outer normal direction of the boundary; The storage area adopts fixed temperature boundary conditions , which is the storage temperature The storage area in the three-dimensional warehouse and the surrounding air adopt a radiation boundary condition , where is the radiative heat flux, is the radiative emissivity of the surface of the storage area, is the Stefan-Boltzmann constant, is the temperature of the surface of the storage area, is the ambient temperature around the storage area; Convection boundary conditions are adopted in the places where the automated storage and retrieval system has ventilation and air flow with the surrounding environment , where is the convective heat flux, is the air convection heat transfer coefficient, is the surface temperature of the convection area of the automated storage and retrieval system, is the environmental temperature outside the convection area.

3. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 1, characterized in that, In step S2, the method for calculating and predicting the tire temperature at different positions through the heat generation by friction and the heat transfer formula is: ， wherein, is the density of the tire, c is the specific heat capacity of the tire material, is the tire temperature, is the heat conduction term, is the heat generated by friction between the tire and the ground, is the convective heat dissipation between the tire and the air, is the radiative heat dissipation of the tire to the outside world; Take the highest value of the tire temperatures at different positions as the predicted temperature of the tire .

4. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 3, characterized in that, Heat conduction term Obtained using the following formula: ， Among them, is the thermal conductivity of the tire material, A is the surface area of the tire, is the temperature difference between the tire surface and the inside, is the thickness from the tire surface to the inside; The heat generated by the friction between the tire and the ground Obtained by the following formula: ， wherein, is the friction coefficient between the tire and the ground, N is the normal force between the tire and the ground, is the vehicle speed; Convective heat dissipation between the tire and the air Obtained using the following formula: ， wherein, is the convective heat transfer coefficient between the tire surface and the air, is the tire surface temperature, is the ambient temperature around the tire; Radiative heat dissipation of the tire to the outside Obtained using the following formula: ， Among them, is the thermal emissivity of the tire surface temperature.

5. According to the AGV vehicle operation control method described in claim 4, the normal force between the tire and the ground is obtained by the following formula: ， Among them, is the weight of the AGV vehicle, is the weight of the goods on the AGV vehicle, and g is the acceleration due to gravity.

6. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 4, characterized in that When determining the friction coefficient between the tire and the ground, judge the measured temperature of the tire whether it is higher than the upper limit of the safe temperature of the tire. If it is not higher than the upper limit of the safe temperature of the tire, the friction coefficient between the tire and the ground takes the maximum friction coefficient , if it is higher than the upper limit of the safe temperature of the tire, then the friction coefficient between the tire and the ground is , where is the friction coefficient, is the upper limit of the safe temperature of the tire 7. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 1, characterized in that, In step S3, the method for determining the driving speed limit, acceleration limit and braking distance according to the predicted tire temperature is: Driving speed limit Obtained using the following formula: , Among them, is the maximum speed of the tire at the upper limit of the safe temperature, is the predicted temperature, is the upper limit of the safe temperature of the tire, is the limit temperature of the tire; Driving acceleration limit Obtained by the following formula: ， Among them, is the basic acceleration; The braking distance is obtained by the following formula: ， Among them, is the braking distance at the predicted temperature, is the vehicle speed, and g is the acceleration due to gravity.

8. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 1, characterized in that In step S4, the method for controlling the driving of the AGV according to the predicted tire temperature to ensure safe braking is: When the predicted temperature approaches the limit temperature cool down the tire, and reduce the maximum speed and maximum acceleration; When the predicted temperature is lower than the limit temperature travel at the maximum speed and maximum acceleration.

9. A method for controlling the operation of an AGV vehicle in a high-temperature environment according to claim 1, characterized in that In step S4, the method for controlling the driving of the AGV according to the predicted tire temperature, driving speed limit, acceleration limit and braking distance to ensure safe braking is: Determine the starting point and ending point of the AGV, obtain the driving route, and judge whether the driving route is a straight line or has a turn. If it is a straight line, the driving process is divided into three stages: starting, straight-line acceleration, and straight-line deceleration braking. If there is a turn, the driving process is divided into four stages: starting, straight-line acceleration, turning, and straight-line deceleration braking; Starting stage: ， Among them, is the speed at the starting stage, is the acceleration at the start, t is the time, is the distance traveled during the starting stage, is the time taken to travel during the starting stage, is the speed at the end of the starting stage; Straight-line acceleration stage: ， Among them, is the speed in the linear acceleration stage, is the acceleration in the linear acceleration stage, is the distance traveled in the linear acceleration stage, is the time taken in the linear acceleration stage, is the speed at the end of the starting stage, is the speed at the end of the linear acceleration stage; Turning stage: The frictional force is greater than or equal to the centrifugal force to obtain the maximum speed and acceleration for maintaining stability during turning, ， Among them, is the friction coefficient between the tire and the ground, and g is the acceleration due to gravity. is the turning radius of the AGV; then ， Among them, is the turning angle, taking 90 degrees, is the turning speed, is the distance traveled during turning, is the time taken for turning travel; Straight-line deceleration braking stage: ， Among them, is the speed in the straight-line braking stage, is the acceleration in the straight-line braking stage, is the distance traveled in the straight-line braking stage, is the time taken to travel in the straight-line braking stage; Establish the objective function and constraint relationship: , where , , and are weighting coefficients; Constraint relationship: , The maximum speed during driving is less than or equal to the driving speed limit , The acceleration during driving is less than or equal to the acceleration limit value , Less than or equal to the corresponding predicted temperature Braking distance .

10. An AGV vehicle, characterized in that, Operate using the AGV vehicle operation control method described in any one of claims 1-9. The AGV vehicle includes a vehicle body with tires and a cooling system. When the predicted tire temperature approaches the limit temperature, the cooling system operates to cool the tires; The cooling system includes a circulation pipeline built in the tire and a water supply device installed in the tire. The water supply device cools the tire by introducing circulating cold water into the circulation pipeline.

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