Method and device for controlling temperature of lubricating grease, vehicle and storage medium

Abstract

The invention provides a method and device for controlling the temperature of lubricating grease, a vehicle and a storage medium, the method is applied to the field of rear wheel steering control, and the method comprises the steps that the temperature of the lubricating grease at the matching position is determined according to the matching temperature at the matching position of a transmission nut and a screw and the damping variation generated in the process that a motor drives the transmission nut and the screw; target working parameters of the motor are determined according to the lubricating grease temperature, the target working parameters are used for representing the running state of the motor, and when the motor runs according to the target working parameters, the lubricating grease temperature is smaller than or equal to the preset temperature; and controlling the motor to operate according to the target working parameters. According to the method, the temperature of the lubricating grease between the transmission nut and the screw which are most prone to heating in the rear wheel steering gear can be controlled within a reasonable range by reducing the output torque or the output power of the motor, and the problems of lubricating grease volatilization, performance reduction and the like caused by too high lubricating grease temperature are solved.

Description

Technical Field

[0001] The present application relates to the field of rear-wheel steering control, and more specifically, to a method, device, vehicle, and storage medium for controlling the temperature of grease in the field of rear-wheel steering control. Background Art

[0002] Currently, with the development of vehicle production technology, some vehicles may be equipped with a Rear Wheel Steering (RWS) to improve the handling performance and driving safety of the vehicle. The rear-wheel steering can increase flexibility when the vehicle is driving at low speed and improve stability and responsiveness when the vehicle is driving at high speed.

[0003] Affected by the geometric design of the vehicle suspension, the self-aligning ability of the rear wheels is relatively weak, that is, the ability of the rear wheels to return to a straight line during steering is relatively weak. This characteristic makes the rear wheels prone to deflection due to external impacts. To solve this problem, the transmission mechanism of the rear-wheel steering needs to have a strong self-locking function.

[0004] The self-locking function mainly depends on friction, and friction will cause energy loss, resulting in a decrease in the transmission efficiency of the transmission mechanism of the rear-wheel steering. The transmission mechanism is prone to heat generation during operation. The overheated temperature will accelerate the evaporation rate of the grease in the transmission mechanism, resulting in insufficient lubrication ability, and may also cause the grease to oxidize or decompose, resulting in irreversible damage.

[0005] Based on this, during the operation of the rear-wheel steering, how to avoid the excessive temperature of the grease has become an urgent problem to be solved. Summary of the Invention

[0006] The present application provides a method, device, vehicle, and storage medium for controlling the temperature of grease. This method can control the temperature of the grease between the transmission nut and the screw, which is the most prone to heat generation in the rear-wheel steering, within a reasonable range by reducing the output torque or output power of the motor, and avoid problems such as the volatilization and performance degradation of the grease caused by excessive temperature.

[0007] In a first aspect, a method for controlling the temperature of grease is provided. This method is applied to a rear-wheel steering system including a rear-wheel steering device. The rear-wheel steering device includes a motor and a transmission nut and a screw that cooperate with each other. The method includes: determining the temperature of the grease at the mating portion according to the mating temperature at the mating portion of the transmission nut and the screw and the damping change amount generated during the process of the motor driving the transmission nut and the screw; determining the target operating parameter of the motor according to the grease temperature, where the target operating parameter is used to represent the operating state of the motor, and when the motor operates with the target operating parameter, the grease temperature is less than or equal to a preset temperature; controlling the motor to operate with the target operating parameter.

[0008] In the above technical solution, for a vehicle equipped with a rear-wheel steering gear, in order to avoid excessive temperature of the grease in the rear-wheel steering gear, the present application proposes a method for controlling the grease temperature. The specific implementation process of this method is as follows: During the operation of the rear-wheel steering gear, since the transmission efficiency between the transmission nut and the screw is the lowest, the temperature is most likely to overheat. Therefore, the temperature of the grease between the transmission nut and the screw is also most likely to be too high and volatilize and fail. The vehicle estimates the temperature of the grease between the transmission nut and the screw based on the change in the cooperation temperature and damping between the transmission nut and the screw. Further, the operation of the motor is controlled by the grease temperature, so that the temperature of the grease during the operation of the motor is less than or equal to the preset temperature. Thus, through the above process, by adjusting the output of the motor, the temperature of the grease between the transmission nut and the screw is controlled not to be too high. This ensures that the temperature of the grease in the entire rear-wheel steering gear is not too high, avoids the problem of grease volatilization and failure at high temperatures, and improves the working efficiency and control accuracy of the rear-wheel steering gear.

[0009] In combination with the first aspect, in some possible implementation manners, determining the target working parameter of the motor according to the grease temperature includes: determining a target adjustment coefficient between the target working parameter and the grease temperature according to the grease temperature; and determining the target working parameter according to the target adjustment coefficient and the grease temperature.

[0010] In combination with the first aspect and the above implementation manners, in some possible implementation manners, the method further includes: obtaining the starting time and the current ambient temperature of the operation of the rear-wheel steering device; obtaining a plurality of first working parameters of the motor at a plurality of first times during the period from the starting time to the current time; obtaining a plurality of historical cooperation temperatures and a plurality of historical ambient temperatures corresponding to a plurality of second times during the period from the starting time to the previous time of the current time; determining the transmission heat generation generated by the transmission between the transmission nut and the screw during the operation of the rear-wheel steering device according to the plurality of first working parameters, the current time, and the starting time; determining the transmission heat dissipation generated by the transmission between the transmission nut and the screw during the operation of the rear-wheel steering device according to the plurality of historical cooperation temperatures, the plurality of historical ambient temperatures, the previous time, and the starting time; and determining the cooperation temperature according to the transmission heat dissipation, the transmission heat generation, and the current ambient temperature.

[0011] Combined with the first aspect and the above implementation manners, in some possible implementation manners, the multiple first operating parameters include multiple first output torques and multiple motor angular velocities. Determining the transmission heat generation amount generated by the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple first operating parameters, the current moment, and the starting moment includes: for any first moment among the multiple first moments, determining the first output torque and the motor angular velocity corresponding to the first moment according to the first moment, the multiple first output torques, and the multiple motor angular velocities; determining the output power of the motor at the first moment according to the first output torque and the motor angular velocity corresponding to the first moment; determining the transmission efficiency between the transmission nut and the screw at the first moment according to the first output torque corresponding to the first moment; and determining the transmission heat generation amount according to the output powers of the motor at the multiple first moments, the transmission efficiencies between the transmission nut and the screw at the multiple first moments, the current moment, and the starting moment.

[0012] Combined with the first aspect and the above implementation manners, in some possible implementation manners, determining the transmission heat dissipation amount generated by the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple historical mating temperatures, the multiple historical ambient temperatures, the previous moment, and the starting moment includes: for any second moment among the multiple second moments, determining the historical mating temperature and the historical ambient temperature corresponding to the second moment according to the second moment, the multiple historical mating temperatures, and the multiple historical ambient temperatures; determining the temperature difference between the historical mating temperature and the historical ambient temperature; and determining the transmission heat dissipation amount according to the temperature differences at the multiple second moments, the starting moment, and the previous moment.

[0013] Combined with the first aspect and the above implementation manners, in some possible implementation manners, the method further includes: controlling the motor to vibrate with a preset amplitude according to a preset period, and when the motor vibrates with the preset amplitude, the output torque of the motor is less than or equal to a preset torque; obtaining the second operating parameter of the motor at the third moment closest to the current moment before the current moment during the process that the motor vibrates with the preset amplitude; and determining the damping change amount according to the second operating parameter.

[0014] Combined with the first aspect and the above implementation manners, in some possible implementation manners, the second operating parameter includes a second output torque and a motor rotation angle. Determining the damping change amount according to the second operating parameter includes: determining the screw output force at the third moment according to the second output torque; determining the screw stroke at the third moment according to the motor rotation angle; and determining the damping change amount according to the screw stroke and the screw output force.

[0015] Second aspect, a device for controlling the temperature of grease is provided. The device is applied to a rear-wheel steering system including a rear-wheel steering device. The rear-wheel steering device includes a motor and a transmission nut and a screw rod that cooperate with each other. The device includes: a grease temperature determination module, configured to determine the grease temperature at the mating part according to the mating temperature at the mating part of the transmission nut and the screw rod, and the damping change amount generated during the process of the motor driving the transmission nut and the screw rod; a parameter determination module, configured to determine the target operating parameter of the motor according to the grease temperature, where the target operating parameter is used to represent the operating state of the motor, and when the motor operates with the target operating parameter, the grease temperature is less than or equal to a preset temperature; an operation control module, configured to control the motor to operate with the target operating parameter.

[0016] In combination with the second aspect, in some possible implementation manners, the parameter determination module is specifically configured to: determine a target adjustment coefficient between the target operating parameter and the grease temperature according to the grease temperature; and determine the target operating parameter according to the target adjustment coefficient and the grease temperature.

[0017] In combination with the second aspect and the above implementation manners, in some possible implementation manners, the device further includes: a mating temperature determination module, configured to obtain the starting moment of the operation of the rear-wheel steering device and the current ambient temperature; obtain a plurality of first operating parameters of the motor at a plurality of first moments during the period from the starting moment to the current moment; obtain a plurality of historical mating temperatures and a plurality of historical ambient temperatures corresponding to a plurality of second moments during the period from the starting moment to the previous moment of the current moment; determine the transmission heat generation amount generated by the transmission of the transmission nut and the screw rod during the operation of the rear-wheel steering device according to the plurality of first operating parameters, the current moment, and the starting moment; determine the transmission heat dissipation amount generated by the transmission of the transmission nut and the screw rod during the operation of the rear-wheel steering device according to the plurality of historical mating temperatures, the plurality of historical ambient temperatures, the previous moment, and the starting moment; and determine the mating temperature according to the transmission heat dissipation amount, the transmission heat generation amount, and the current ambient temperature.

[0018] Combined with the second aspect and the above implementation manners, in some possible implementation manners, the multiple first operating parameters include multiple first output torques and multiple motor angular velocities. The matching temperature determination module is specifically configured to: for any one of the multiple first moments, determine the first output torque and the motor angular velocity corresponding to the first moment according to the first moment, the multiple first output torques, and the multiple motor angular velocities; determine the output power of the motor at the first moment according to the first output torque and the motor angular velocity corresponding to the first moment; determine the transmission efficiency between the transmission nut and the screw at the first moment according to the first output torque corresponding to the first moment; and determine the transmission heat generation according to the output powers of the motor at the multiple first moments, the transmission efficiencies between the transmission nut and the screw at the multiple first moments, the current moment, and the starting moment.

[0019] Combined with the second aspect and the above implementation manners, in some possible implementation manners, the matching temperature determination module is further configured to: for any one of the multiple second moments, determine the historical matching temperature and the historical ambient temperature corresponding to the second moment according to the second moment, the multiple historical matching temperatures, and the multiple historical ambient temperatures; determine the temperature difference between the historical matching temperature and the historical ambient temperature; and determine the transmission heat dissipation according to the temperature differences at the multiple second moments, the starting moment, and the previous moment.

[0020] Combined with the second aspect and the above implementation manners, in some possible implementation manners, the device further includes: a damping determination module, configured to control the motor to vibrate with a preset amplitude at a preset period. When the motor vibrates with the preset amplitude, the output torque of the motor is less than or equal to a preset torque; obtain the second operating parameters of the motor at the third moment closest to the current moment before the current moment during the process that the motor vibrates with the preset amplitude; and determine the damping change amount according to the second operating parameters.

[0021] In some possible implementation manners, the damping determination module is specifically configured to: determine the screw output force at the third moment according to the second output torque; determine the screw stroke at the third moment according to the motor rotation angle; and determine the damping change amount according to the screw stroke and the screw output force.

[0022] In a third aspect, a vehicle is provided, including a memory and a processor. The memory is used to store executable program code, and the processor is used to call and run the executable program code from the memory, so that the vehicle executes the method in the first aspect or any one of the possible implementation manners of the first aspect.

[0023] Fourthly, a computer program product is provided, which includes computer program code that, when running on a computer, causes the computer to execute the method in the above first aspect or any possible implementation manner of the first aspect.

[0024] Fifthly, a computer-readable storage medium is provided, which stores computer program code that, when running on a computer, causes the computer to execute the method in the above first aspect or any possible implementation manner of the first aspect. Description of the Drawings

[0025] Figure 1 FIG. is a schematic structural diagram of a rear-wheel steering system provided by an embodiment of the present application;

[0026] Figure 2 FIG. is a schematic structural diagram of an electronic control unit provided by an embodiment of the present application;

[0027] Figure 3 FIG. is a schematic flowchart of a method for controlling the temperature of grease provided by an embodiment of the present application;

[0028] Figure 4 FIG. is a curve diagram of the change of motor rotation angle and motor output torque provided by an embodiment of the present application;

[0029] Figure 5 FIG. is a schematic structural diagram of a device for controlling the temperature of grease provided by an embodiment of the present application;

[0030] Figure 6 FIG. is a schematic structural diagram of a vehicle provided by an embodiment of the present application. Detailed Embodiments

[0031] Hereinafter, the technical solutions in the present application will be clearly and elaborately described in conjunction with the drawings. Among them, in the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B may mean A or B. The "and / or" in the text is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B may mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more than two.

[0032] Hereinafter, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as implying or indicating relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0033] Before introducing the method of the embodiments of the present application, first, a glossary of technical terms that may be involved in the embodiments of the present application will be provided.

[0034] Rear-wheel steering gear: It is a part of the vehicle suspension and steering system, specifically designed to control the direction of the vehicle's rear wheels. It adjusts the angle of the rear wheels through mechanical, hydraulic, or electronic control systems to achieve precise control of the vehicle's dynamic behavior. The rear-wheel steering gear mainly improves the vehicle's handling performance and stability by adjusting the angle of the rear wheels. Its main functions include but are not limited to the following:

[0035] 1. Improve low-speed maneuverability

[0036] When driving at low speeds or parking, the rear-wheel steering gear can make the rear wheels turn in the opposite direction to the front wheels, thereby reducing the turning radius of the vehicle, making the vehicle more maneuverable, and facilitating operation in narrow spaces.

[0037] 2. Enhance high-speed stability

[0038] When driving at high speeds, the rear-wheel steering gear can make the rear wheels turn in the same direction as the front wheels to help the vehicle corner more smoothly, reduce the risk of roll and drift, and improve driving safety.

[0039] 3. Optimize vehicle dynamic response

[0040] By adjusting the rear-wheel angle in real time, the rear-wheel steering system can dynamically change the position of the rear wheels according to vehicle speed, steering wheel angle, and other sensor data, thereby optimizing the vehicle's dynamic response and providing a better driving experience.

[0041] Grease: It is a semi-solid or solid lubricating material composed of base oil, thickener, and additives. It has strong adhesion and is not easily lost, and can provide long-lasting lubrication within a wide operating temperature range.

[0042] In the rear-wheel steering system, the functions of grease are as follows:

[0043] 1. Reduce friction and wear

[0044] In the rear-wheel steering system, grease can fill the tiny unevenness on the metal surface, form a protective film, significantly reduce the direct metal contact between the transmission nut and the screw, thereby reducing the friction coefficient and wear.

[0045] 2. Dissipate heat

[0046] In addition to reducing friction, grease can also help dissipate heat to a certain extent, prevent the temperature from being too high due to heat generated by friction, thereby avoiding the overheating failure of the grease and maintaining its lubrication performance.

[0047] 3. Prevent corrosion

[0048] The grease can form a protective layer on the metal surface, isolating air and moisture, preventing the occurrence of oxidation reactions, and thus playing a role in anti-corrosion.

[0049] 4. Shock Absorption and Buffering

[0050] The grease has a certain viscosity, which can absorb vibration energy to a certain extent, reduce the impact and vibration between mechanical components, and improve the smoothness and comfort of the system.

[0051] Automatic Return-to-Center Ability: It refers to the ability of the wheels (including the front wheels and the rear wheels) to automatically return to the straight-ahead driving position after the vehicle completes a turning operation and releases the steering wheel.

[0052] Self-Locking Ability: It refers to the ability of certain mechanical components to self-lock under specific conditions to prevent accidental movement or loosening.

[0053] Damping: It refers to the ability of a system to consume vibration energy internally, usually manifested as the force to reduce the vibration amplitude.

[0054] Transmission Pair: Also known as a kinematic pair or a mechanical pair, it is the basic unit in a mechanical system where two components are in direct contact and interact with each other to transmit motion and power. It is the basic component that constitutes a mechanical transmission system and realizes the transmission of force and motion through specific geometric shapes and contact methods.

[0055] According to different motion forms and contact methods, the types of transmission pairs include revolute pairs, prismatic pairs, screw pairs, gear pairs, cam pairs, belt drive pairs, chain drive pairs, etc.

[0056] It should be understood that the method of the embodiments of the present application is applied to a vehicle equipped with a rear-wheel steering system (or a rear-wheel steering gear). For the convenience of understanding the solutions of the embodiments of the present application, the structure and working principle of the rear-wheel steering system will be introduced first below.

[0057] Figure 1 It is a schematic structural diagram of a rear-wheel steering system provided by the embodiments of the present application.

[0058] Exemplarily, as Figure 1 shown, the rear-wheel steering system 100 mainly includes two major parts: a rear-wheel steering gear 102 and a motor controller (or, motor control unit) 101.

[0059] Among them, the rear-wheel steering gear 102 is composed of multiple components. As Figure 1 shown, the rear-wheel steering gear 102 specifically includes: a motor 1, a motor output shaft 2, a drive belt 3, a drive nut 4, a screw rod 5, a left tie rod 6, a steering gear housing 7, and a right tie rod 8.

[0060] The motor controller 101 is mainly used to receive the motor control signal and control the rotation of the motor 1 according to the motor control signal to drive the rear wheel steering gear 102 to work.

[0061] Based on the composition of the above-mentioned rear wheel steering gear 102, the specific working process of the rear wheel steering gear 102 is as follows:

[0062] When the vehicle needs to perform rear wheel steering, the motor controller 101 will control the motor 1 to start running according to the motor control signal. After the motor 1 starts, the driving motor output shaft 2 starts to rotate. The motor output shaft 2 is directly connected to the transmission belt 3 through a coupling or other means to transmit the rotational motion of the motor 1 to the transmission belt 3. The transmission belt 3 transmits the rotational motion of the motor output shaft 2 to the transmission nut 4 through friction, driving the transmission nut 4 to rotate.

[0063] Optionally, the type of the transmission belt 3 can be any one of a synchronous belt, a V-belt or a flat belt, and the embodiments of the present application do not limit the type of the transmission belt 3.

[0064] The transmission nut 4 has internal threads that match the external threads on the screw rod 5. Thus, in the rear wheel steering gear 102, the transmission nut 4 and the screw rod 5 form a screw-nut transmission pair, simply referred to as a "screw pair".

[0065] When the transmission nut 4 rotates, since the screw rod 5 is restricted to move only along its length direction and cannot rotate. Therefore, the screw rod 5 will perform a linear motion under the action of the transmission nut 4, and thus through the cooperation of the transmission nut 4 and the screw rod 5, the rotational motion of the transmission nut 4 is converted into the linear motion of the screw rod 5.

[0066] Both ends of the screw rod 5 are respectively connected to the left pull rod 6 and the right pull rod 8. As the screw rod 5 moves linearly, the left pull rod 6 and the right pull rod 8 will also move accordingly, thereby pushing or pulling the steering knuckle of the rear wheel and driving the rear wheel to rotate.

[0067] The steering gear housing 7 provides physical support for all the above components and also plays a role in protecting the internal parts from the influence of the external environment.

[0068] After introducing the composition structure and working principle of the rear wheel steering system, the application scenarios of the embodiments of the present application will be introduced below.

[0069] For a vehicle equipped with a rear wheel steering gear, the rear wheel steering gear is installed on the rear axle of the vehicle. Due to the different structures of the front suspension and the rear suspension of the vehicle. The front suspension mostly adopts a MacPherson type or a multi-link type, and pays more attention to the steering and self-aligning ability in design. The rear suspension structure is relatively simple and is mainly responsible for the support and shock absorption functions, lacking a self-aligning design like the front suspension, resulting in a relatively weak self-aligning ability of the rear wheel itself.

[0070] Due to the weak self-aligning ability of the rear wheels, the rear wheels are prone to deflection due to external impacts. To solve this problem, the transmission mechanism of the rear-wheel steering gear needs to have a strong self-locking function. The self-locking function mainly relies on friction, and friction will cause energy loss, resulting in a decrease in the transmission efficiency of the rear-wheel transmission mechanism, and the transmission mechanism of the rear-wheel steering gear is prone to heat generation during operation.

[0071] In particular, since the cooperation between the transmission nut and the screw is based on the principle of screw transmission, they mainly rely on sliding friction to transmit force and motion. For other components in the rear-wheel steering gear, such as the motor output shaft, transmission belt, or pull rod, etc., a design method with less rolling friction or sliding friction is mostly adopted. Therefore, compared with other components, the friction between the transmission nut and the screw is much greater. In addition, the self-locking function of the rear-wheel steering gear mainly targets the transmission nut and the screw, which will cause a relatively high reverse driving resistance in the screw pair. The combination of the above various factors results in the lowest transmission efficiency and the greatest friction between the transmission nut and the screw. Therefore, the transmission nut and the screw are more prone to heat generation compared with other components.

[0072] Since the transmission nut and the screw are prone to heat generation, the overheat temperature will accelerate the evaporation rate of the grease between the transmission nut and the screw, resulting in insufficient lubrication ability of the grease, and it is also possible that the grease will oxidize or decompose, causing irreversible damage.

[0073] Based on the above problems, the embodiment of the present application proposes a method for controlling the temperature of the grease, which can control the temperature of the grease between the transmission nut and the screw, which is the most prone to heat generation in the rear-wheel steering gear, within a reasonable range by reducing the output torque or output power of the motor, and avoid problems such as grease volatilization and performance degradation caused by too high grease temperature.

[0074] It should be understood that in the process of implementing the method of the embodiment of the present application, it can be applied to Figure 1 the rear-wheel steering system 100 shown, and is specifically applied to the motor controller 101 in the above system 100. When implementing the above method, the motor controller 101 can be divided according to different functions performed.

[0075] Figure 2 is a schematic structural diagram of an electronic control unit provided by the embodiment of the present application. Among them, this electronic control unit (Electronic Control Unit, ECU) is the Figure 1 motor controller 101 in

[0076] Exemplarily, as Figure 2 shown, in combination with Figure 1The motor controller 101 specifically includes the following modules: a spiral pair temperature calculation module 201 , a spiral pair damping calculation module 202 , a grease temperature calculation module 203 , a motor parameter calculation module 204 and a motor control module 205 .

[0077] The functions of each module are as follows:

[0078] The spiral pair temperature calculation module 201 is used to calculate the temperature of the spiral pair according to various parameter information. Figure 1 The fitting temperature between the transmission nut 4 and the screw 5 in the embodiment. Among them, various parameter information includes Figure 2 The environmental parameters, the working parameters of the motor 1 and the operating parameters of the rear wheel steering device (ie, the rear wheel steering gear 102 ) are shown. Further, the spiral pair temperature calculation module 201 can send the calculated matching temperature to the grease temperature calculation module 203 .

[0079] The helical pair damping calculation module 202 is used to calculate the change of the damping of the rear wheel steering system 100 in the power transmission path from the motor 1 to the transmission nut 4 and the screw 5, that is, the damping change amount, according to the working parameters of the motor 1. Further, the helical pair damping calculation module 202 can send the calculated damping change amount to the grease temperature calculation module 203.

[0080] The grease temperature calculation module 203 is used to determine the grease temperature at the fitting point between the transmission nut 4 and the screw 5 according to the fitting temperature and the damping change, and send it to the motor parameter calculation module 204.

[0081] The motor parameter calculation module 204 is used to determine the target operating parameters of the motor 1 according to the grease temperature, and send the target operating parameters to the motor control module 205 .

[0082] The motor control module 205 is used to control the operation of the motor 1 according to the target operating parameters.

[0083] It should be understood that when the motor control module 205 controls the operation of the motor 1 with the target working parameters, the grease temperature between the transmission nut 4 and the screw 5 is less than or equal to the preset temperature. Since the temperature between the transmission nut 4 and the screw 5 in the rear-wheel steering gear 102 is most likely to generate heat. Therefore, compared with the grease temperature at other positions, the grease temperature between the transmission nut 4 and the screw 5 is higher. During the operation of the rear-wheel steering gear 102, the embodiment of the present application adjusts the working parameters of the motor 1 to ensure that the grease temperature between the transmission nut 4 and the screw 5 is not too high, so that the grease temperature in the entire rear-wheel steering gear 102 is within a reasonable range, avoiding the problem of grease volatilization and failure under high temperature conditions.

[0084] After introducing the system structure and working process in the above embodiments of the present application, a method for controlling the temperature of grease will be introduced below.

[0085] Figure 3 It is a schematic flowchart of a method for controlling the temperature of grease provided by an embodiment of the present application. It should be understood that in addition to being applied to the above-mentioned motor controller, this method can also be applied to any ECU in a vehicle. During the following introduction, the motor controller is taken as an example of the execution subject of this method. Among them, the vehicle mentioned in the embodiments of the present application is specifically a vehicle equipped with Figure 1 the rear-wheel steering system 100 shown. The rear-wheel steering system 100 includes a rear-wheel steering gear 101. The rear-wheel steering gear 101 includes a transmission nut 4 and a screw rod 5 that cooperate with each other.

[0086] Exemplarily, as Figure 3 shown, this method 300 includes steps 301-step 303:

[0087] 301, Determine the grease temperature at the mating part according to the mating temperature at the mating part of the transmission nut and the screw rod, and the damping change amount generated during the process of the motor driving the transmission nut and the screw rod.

[0088] It should be understood that in combination with the foregoing description, during the operation of the rear-wheel steering gear, since the transmission efficiency between the transmission nut and the screw rod is the lowest, the probability of the grease temperature being too high between the transmission nut and the screw rod is the greatest. Too high grease temperature will cause the volatilization performance of the grease to decline. To solve this problem, an embodiment of the present application proposes a method for controlling the grease temperature. This method can estimate the grease temperature between the transmission nut and the screw rod through a series of parameters. Further, the working parameters of the motor in the rear-wheel steering gear are adjusted according to the grease temperature to obtain the target working parameters of the motor. When the motor controller works with the target working parameters, the effect of reducing the grease temperature can be achieved. The above adjustment of the working parameters of the motor specifically refers to reducing the output power or output torque of the motor in the embodiments of the present application.

[0089] Among them, the target working parameters of the motor are used to represent the operating state of the motor. Optionally, the working parameters of the motor include output torque or output power.

[0090] The main reasons for reducing the grease temperature by reducing the output torque or output power of the motor are as follows:

[0091] Reduce frictional heat generation. When the output torque or output power of the motor decreases, if the load remains unchanged, this means that the relative movement speed between the motor and the transmission mechanism may decrease, or the pressure applied to each contact surface (mating surface) decreases, thereby reducing the frictional force and the heat generated by the frictional force.

[0092] Reduce energy consumption. When the output torque or output power of the motor decreases, the internal energy losses (such as copper loss, iron loss, etc.) will also decrease accordingly, reducing the heat generation of the motor itself. The motor and the transmission mechanism are closely connected, and the heat generated by the motor will be conducted to the grease through metal components, thus reducing the heat transferred to the grease.

[0093] Improve heat dissipation conditions. Lower torque or power output means a reduction in the overall heat load of the rear-wheel steering system. Even under the same heat dissipation conditions, since less heat is generated, the grease can dissipate excess heat more effectively, thus maintaining a lower operating temperature. The lower operating load allows the grease to flow more smoothly within the system, thereby improving its heat dissipation efficiency.

[0094] Specifically, in the embodiment of the present application, the motor controller obtains the grease temperature at the mating part of the transmission nut and the screw through the mating temperature at the mating part of the transmission nut and the screw, and the damping change amount generated during the process of the motor driving the transmission nut and the screw.

[0095] Among them, damping refers to the ability of the system to consume vibration energy internally. Correspondingly, the damping change amount refers to the change in the energy dissipation ability of the system caused by different conditions or factors internally.

[0096] The damping change amount generated during the process of the motor driving the transmission nut and the screw refers to the change of the system damping over time or other factors during the process of power transmission from the motor to the transmission mechanism of the transmission nut and the screw. The reasons for the damping change may be: First, as the operating temperature changes, the physical properties of the material will change, resulting in a change in the friction coefficient, thereby affecting the damping characteristics. Second, long-term use will cause wear on the contact surface, changing the surface roughness and contact area, and thus affecting the frictional force and damping.

[0097] It should be understood that the reason why the mating temperature at the mating part of the transmission nut and the screw is not equal to the grease temperature at the mating part is that the transmission nut and the screw are usually made of metal, while the grease is a semi-solid or liquid substance. Compared with metal, the thermal conductivity of the grease is relatively poor. In addition, even in the case of close contact, there may still be tiny gaps between the thread surfaces, and these gaps increase the resistance to heat transfer. Therefore, although frictional heat generation mainly occurs on the thread contact surface, there will be some losses during the process of heat transfer from the metal component to the grease.

[0098] Based on this, the damping change amount can directly reflect the friction state at the mating part of the transmission nut and the screw, and the friction state is affected by the viscosity of the grease, and the viscosity of the grease is closely related to the temperature. Therefore, in the embodiments of the present application, the grease temperature at the mating part can be estimated through the mating temperature at the mating part of the transmission nut and the screw and the damping change amount in the process from the motor to the transmission nut and the screw.

[0099] The calculation processes of the mating temperature and the damping change amount are introduced separately below.

[0100] The calculation process of the mating temperature at the mating part.

[0101] In a possible implementation manner, the method further includes:

[0102] Obtain the starting moment when the rear-wheel steering device operates and the current ambient temperature;

[0103] Obtain multiple first working parameters of the motor at multiple first moments during the period from the starting moment to the current moment;

[0104] Obtain multiple historical mating temperatures and multiple historical ambient temperatures corresponding to multiple second moments during the period from the starting moment to the previous moment of the current moment;

[0105] Determine the transmission heat generation amount generated by the transmission of the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple first working parameters, the current moment and the starting moment;

[0106] Determine the transmission heat dissipation amount generated by the transmission of the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple historical mating temperatures, the multiple historical ambient temperatures, the previous moment and the starting moment;

[0107] Determine the mating temperature according to the transmission heat dissipation amount, the transmission heat generation amount and the current ambient temperature.

[0108] Specifically, the calculation process of the mating temperature in the embodiments of the present application can be represented by the following formula (1).

[0109]

[0110] Wherein, in formula (1):

[0111] TMP screw(t1) : The mating temperature at the mating part of the transmission nut and the screw at the current moment, unit: degree Celsius (°C);

[0112] Q1: The transmission heat generation amount during the transmission of the transmission nut and the screw, unit: joule (J);

[0113] Q2: The transmission heat dissipation amount during the transmission of the transmission nut and the screw, unit: joule (J);

[0114] m p : The mass of the transmission nut and the screw is determined by the specific structural design of the transmission nut and the screw, unit: kilogram (Kg);

[0115] C p : The specific heat capacity of the nut-screw mechanism is determined by the specific material selection of the nut and the screw, unit: (joule per kilogram per degree Celsius J / (Kg·℃));

[0116] TMP env(t1) : The ambient temperature at the current moment, that is, the current ambient temperature, unit: degree Celsius (℃).

[0117] Among them, the multiple first working parameters include multiple first output torques and multiple motor angular velocities.

[0118] Exemplarily, for the starting moment of the rear-wheel steering gear operation, after the previous rear-wheel steering gear operation ends, if the motor controller detects again that the motor speed is not 0 rpm, it means that the rear-wheel steering gear starts to operate again. The motor controller can record the starting moment of this rear-wheel steering gear operation.

[0119] Exemplarily, the motor controller can collect the current ambient temperature through a temperature sensor outside the vehicle, or can estimate the current ambient temperature by combining other parameters. In the embodiments of the present application, any method that can estimate the ambient temperature is within the protection scope of the embodiments of the present application.

[0120] Exemplarily, for the multiple first output torques and multiple motor angular velocities of the motor at multiple first moments during the period from the starting moment to the current moment. During the operation of the rear-wheel steering gear, the method flow in the embodiments of the present application is continuously and repeatedly executed according to a period, that is, the estimation process of the grease temperature is dynamically updated. Therefore, every certain period, the motor controller will collect the first output torque of the motor through a torque sensor installed on the motor, and collect the motor angular velocity through an angular velocity sensor installed on the motor, so as to estimate the grease temperature. Therefore, the motor controller can obtain multiple first moments, the multiple first output torques and multiple motor angular velocities of the motor. Among them, the time interval between two adjacent first moments is the period of the method execution in the embodiments of the present application.

[0121] Exemplarily, for multiple historical mating temperatures and multiple historical ambient temperatures corresponding to multiple second moments during the period from the starting moment to the previous moment of the current moment. Since the grease temperature is dynamically updated with the cycle. Based on this, the motor controller can obtain an ambient temperature and estimate the mating temperature every cycle duration, so as to obtain the grease temperature. Therefore, the motor controller can obtain multiple historical mating temperatures and multiple historical ambient temperatures corresponding to multiple second moments based on historical data. Wherein, the time interval between two adjacent second moments is the cycle for executing the method of the embodiment of the present application described above.

[0122] After obtaining the above various parameters, the motor controller can determine the transmission heat generation generated by the transmission nut and the screw during the operation of the rear-wheel steering device based on multiple first working parameters, the current moment, and the starting moment. Specifically, the calculation process of the transmission heat generation is as follows.

[0123] In a possible implementation manner, the multiple first working parameters include multiple first output torques and multiple motor angular velocities. Determining the transmission heat generation generated by the transmission nut and the screw during the operation of the rear-wheel steering device based on the multiple first working parameters, the current moment, and the starting moment includes:

[0124] For any one of the multiple first moments, determine the first output torque and the motor angular velocity corresponding to the first moment according to the first moment, the multiple first output torques, and the multiple motor angular velocities;

[0125] Determine the output power of the motor at the first moment according to the first output torque and the motor angular velocity corresponding to the first moment;

[0126] Determine the transmission efficiency of the transmission nut and the screw at the first moment according to the first output torque corresponding to the first moment;

[0127] Determine the transmission heat generation according to the output power of the motor at multiple first moments, the transmission efficiency of the transmission nut and the screw at multiple first moments, the current moment, and the starting moment.

[0128] Specifically, the calculation process of the transmission heat generation can be expressed by the following formulas (2)-(3).

[0129]

[0130] P mot(ti) =TQ mot(ti) ·ω mot(ti) Formula (3)

[0131] Wherein, in Formulas (2)-(3):

[0132] Q1: The transmission heat generation during the transmission process of the transmission nut and the screw, unit: joule (J);

[0133] t0: The starting moment when the rear-wheel steering gear operates, unit: minute (min);

[0134] t1: The current moment when the rear-wheel steering gear operates, unit: minute (min);

[0135] P mot(ti) : The output power of the motor at any first moment, unit: watt (W);

[0136] η (ti) : The transmission efficiency between the transmission nut and the screw, which is a curve varying according to the motor output torque and can be pre-calibrated through testing during the development stage of the rear-wheel steering gear. Since the motor output torque varies with time, the transmission efficiency also varies with time, dimensionless;

[0137] TQ mot(ti) : The first output torque of the motor at any first moment, unit: Newton-meter (N·m);

[0138] ω mot(ti) : The angular velocity of the motor at any first moment, unit: radian per second (rad / s).

[0139] It should be understood that in the embodiments of the present application, the output torque and the angular velocity of the motor vary with time. That is to say, during the operation of the rear-wheel steering gear, the motor controller can obtain the output torque and the angular velocity of the motor at multiple first moments at regular intervals, and then based on formula (3), obtain the output power of the motor at each first moment. In addition, the transmission efficiency is a variable corresponding to the motor output torque. Therefore, at each first moment, the motor controller can look up the transmission efficiency at this first moment according to the output torque of the motor at this first moment and the corresponding relationship between the motor output torque and the transmission efficiency.

[0140] Thus, in the definite integral expression shown in the above formula (2), 1000 in the integrand part of the definite integral is a constant, and P mot(ti) and η (ti) are both numerical values that vary with time. Different from the traditional definite integral calculation, P mot((ti) and η (ti) The variation processes of the two parameters with time do not correspond to mathematical function expressions, but only have specific numerical values at time points. Therefore, in the case where the integrand function does not have a specific mathematical function expression, the above process of calculating the definite integral can be solved by means of numerical integration.

[0141] Optionally, the numerical integration method includes the trapezoidal method or the Simpson's method, etc. In the embodiments of the present application, the trapezoidal method is used to calculate the definite integral as an example.

[0142] It should be understood that the basic idea of the trapezoidal integration method is to divide the integration interval into multiple small intervals, and approximate the sum of the areas under the curves of multiple small intervals as the sum of the areas of trapezoids.

[0143] The process of calculating the definite integral by the trapezoidal method can be expressed by the following formulas (4)-(5).

[0144]

[0145] Among them, in formulas (4)-(5):

[0146] t0: The starting moment when the rear-wheel steering gear operates, unit: minute (min);

[0147] t1: The current moment when the rear-wheel steering gear operates, unit: minute (min);

[0148] Δt: The time interval, which can be the execution period of the method in the embodiment of the present application in the embodiment of the present application, unit: minute (min);

[0149] n: The number of divided time intervals, obtained from the starting moment, the current moment, and the time interval Δt;

[0150] f (t) : The value of the integrand part in the above formula (2), that is, 1000·P mot((ti) ·(1 - η (ti) );

[0151] ti = t0 + i·Δt.

[0152] After obtaining multiple first output torques and motor angular velocities at multiple first moments, for any one of the first moments, the motor controller can calculate the output power of the motor at the first moment according to the first output torque and the motor angular velocity at the first moment. Since the transmission efficiency is related to the output torque of the motor, after obtaining the first output torque of the motor at the first moment, the motor controller can obtain the transmission efficiency between the transmission nut and the screw at the first moment through the pre-set corresponding relationship between the output torque of the motor and the transmission efficiency.

[0153] Furthermore, the motor controller can obtain the value of f (t) at the first moment according to the motor output power at the first moment and the transmission efficiency between the transmission nut and the screw at the first moment. Thus, the motor controller can obtain the values of f (t) at multiple first moments from t0 to t1, and substitute them into the above formula (4), and then the result of the definite integral, that is, the transmission heat generation, can be solved.

[0154] In addition, the motor controller can determine the transmission heat dissipation based on multiple historical mating temperatures, multiple historical ambient temperatures, the previous moment, and the starting moment. Specifically, the calculation process of the transmission heat dissipation is as follows.

[0155] In one possible implementation, based on multiple historical mating temperatures, multiple historical ambient temperatures, the previous moment, and the starting moment, to determine the transmission heat dissipation generated by the transmission nut and screw during the operation of the rear-wheel steering device, including:

[0156] For any one of the multiple second moments, based on the second moment, multiple historical mating temperatures, and multiple historical ambient temperatures, determine the historical mating temperature and historical ambient temperature corresponding to the second moment;

[0157] Determine the temperature difference between the historical mating temperature and the historical ambient temperature;

[0158] Based on the temperature differences at multiple second moments, the starting moment, and the previous moment, determine the transmission heat dissipation.

[0159] Specifically, the calculation process of the transmission heat dissipation can be expressed by the following formula (6).

[0160]

[0161] Among them, in formula (6):

[0162] Q2: The transmission heat dissipation during the transmission process of the transmission nut and the screw, unit: joule (J);

[0163] t0: The starting moment of the rear-wheel steering gear operation, unit: minute (min);

[0164] t2: The previous moment before the current moment, unit: minute (min);

[0165] TMP screw(ti) : The historical mating temperature at any second moment, unit: degree Celsius (°C);

[0166] TMP env(ti) : The historical ambient temperature at any second moment, unit: degree Celsius (°C);

[0167] K t : The heat dissipation coefficient of the transmission nut and the screw, which is related to the mechanical structure design of the rear-wheel steering gear and can be pre-calibrated through tests during the development stage, unit: watt per square meter per degree Celsius (W / (m 2 ·°C));

[0168] S: The equivalent heat dissipation area of the transmission nut and the screw, which can be pre-calibrated through test data during the development stage, unit: square meter (m 2 )

[0169] Similar to the above calculation process of the transmission heat generation, in the integrand part of the above formula (6), K t and S are constants. TMP screw(ti) and TMP env(ti) These two parameters are values that change with time. And TMP screw(ti) and TMP env(ti) The change process with time does not correspond to a mathematical function expression, but only corresponds to specific values at time points. Therefore, in the case where the integrand function does not have a specific mathematical function expression, the above process of calculating the definite integral can also be solved by means of numerical integration.

[0170] Similarly, when solving the transmission heat dissipation by means of numerical integration, referring to the above formulas (4)-(5), the number of n can be determined by t1, t2 and Δt. f (t) Specifically, K in formula (6) t ·S·(TMP screw(ti) -TMP env(ti) ). Specifically, for any second moment among multiple second moments, the motor controller can calculate the temperature difference at the second moment based on the historical matching temperature and the historical ambient temperature at the second moment, and based on the temperature difference at the second moment, as well as the heat dissipation coefficient and the equivalent heat dissipation area, obtain f (t) at the second moment, and substitute it into the above formula (4), then the result of the definite integral, that is, the transmission heat dissipation, can be solved.

[0171] After obtaining the transmission heat dissipation and the transmission heat generation, the motor controller can determine the matching temperature at the current moment through formula (1) based on the transmission heat dissipation, the transmission heat generation and the current ambient temperature.

[0172] Calculation process of the damping change amount.

[0173] In a possible implementation, the method further includes:

[0174] Controlling the motor to vibrate with a preset amplitude according to a preset period. When the motor vibrates with a preset amplitude, the output torque of the motor is less than or equal to the preset torque;

[0175] Obtaining the second working parameter of the motor at the third moment closest to the current moment before the current moment during the process of the motor vibrating with a preset amplitude;

[0176] Determining the damping change amount according to the second working parameter.

[0177] It should be understood that in the embodiments of the present application, by performing stiffness self-check on the transmission nut and screw of the rear-wheel steering gear and recording the change curves of the motor rotation angle and the motor output torque, it is found that when the motor rotation angle is 0.5g away from the zero position, the movement of the transmission mechanism of the rear-wheel steering gear is not affected by the external forces transmitted by the left tie rod and the right tie rod. Herein, g refers to the clearance of the transmission mechanism, specifically the free stroke of the motor rotation angle when the motor output torque does not change significantly, which is the mating clearance between the rear-wheel steering tie rod and the wheel, and the unit is radian (rad) or degree (°).

[0178] Figure 4 It is a change curve graph of the motor rotation angle and the motor output torque provided by the embodiments of the present application.

[0179] Exemplarily, as Figure 4 shown, the abscissa represents the motor rotation angle, and the ordinate represents the motor output torque. The direction indicated by the arrow is the change direction of the motor rotation angle.

[0180] From Figure 4 it can be seen that: the motor starts to rotate forward from the zero position, the motor rotation angle starts to increase along the positive direction of the abscissa, the motor output torque gradually increases until the motor rotation angle reaches the maximum value of the positive rotation angle. At the same time, the output torque of the motor during forward rotation also reaches the maximum value.

[0181] Subsequently, the motor starts to rotate in reverse, the motor rotation angle starts to decrease along the positive direction, and the output torque also decreases along the positive direction until the motor rotation angle returns to the zero position again. The motor continues to rotate in reverse, the motor rotation angle starts to increase along the reverse direction of the abscissa, the motor output torque gradually increases along the reverse direction until the motor rotation angle reaches the maximum value of the reverse rotation angle. At the same time, the output torque of the motor during reverse rotation also reaches the maximum value.

[0182] Subsequently, the motor starts to rotate forward again, the motor rotation angle starts to decrease along the reverse direction, and the output torque also decreases along the reverse direction until the motor rotation angle returns to the zero position again.

[0183] From Figure 4 it can be seen that when the motor rotation angle changes and the motor output torque does not change significantly, the change range of the motor rotation angle is the aforementioned clearance g of the transmission mechanism.

[0184] Whether the motor rotates forward or backward, when the motor rotation angle is 0.5g away from the zero position (i.e., the motor rotation angle is 0.5g), the output torque of the motor does not change significantly. That is, the movement of the transmission mechanism between the motor and the transmission nut and screw is not affected by the external forces transmitted by the left pull rod and the right pull rod, and the rear wheel steering system is not affected by external forces. Therefore, when the motor rotation angle is 0.5g away from the zero position, there are only two factors that affect the motor output torque and the motor rotation angle: the inertia of the transmission mechanism and the damping of the transmission mechanism. The inertia of the transmission mechanism is designed and will not change due to the environment. Therefore, the only thing that changes with temperature is the damping change amount between the motor and the transmission nut and screw. Therefore, when the temperature of the grease changes, the damping change amount will also change accordingly.

[0185] Based on the above characteristics, the motor controller can control the motor to vibrate with a preset amplitude at a preset period and record the working parameters of the motor at each vibration moment.

[0186] In the embodiment of the present application, the preset amplitude refers to the maximum deviation of the motor rotation angle from the reference position during the vibration of the motor. The reference position is the zero position of the motor, and the preset amplitude is 0.5g. Thus, at each vibration moment, the motor controller can obtain the working parameters of the motor.

[0187] It can be seen that when the motor rotates at 0.5g away from the zero position, the output torque of the motor is not too large either. In the embodiment of the present application, the maximum value of the motor output torque within this range can be recorded as the preset torque. Thus, when the motor vibrates with an amplitude of 0.5g, the output torque of the motor must be less than or equal to the preset torque.

[0188] Since the grease temperature affects the damping change amount. In the embodiment of the present application, if it is necessary to solve the grease temperature at the current moment, it is necessary to first determine the damping change amount determined most recently before the current moment. Therefore, based on the working parameters of multiple motors recorded during the historical vibration process of the motor, the motor controller can determine the second working parameters of the motor at the third moment closest to the current moment before the current moment.

[0189] Optionally, the second working parameters of the motor include the second output torque and the motor rotation angle.

[0190] Exemplarily, the motor controller can obtain the motor rotation angle through a sensor on the motor.

[0191] Specifically, the process of determining the damping change amount based on the second working parameters is as follows.

[0192] In a possible implementation manner, the second working parameters include the second output torque and the motor rotation angle. Determining the damping change amount according to the second working parameters includes:

[0193] Determine the screw output force at the third moment according to the second output torque;

[0194] Determine the screw stroke at the third moment according to the motor rotation angle;

[0195] Determine the damping change amount according to the screw stroke and the screw output force.

[0196] Specifically, when determining the damping change amount, it can be solved through the dynamic equation of the rear-wheel steering gear.

[0197] The dynamic equation of the rear-wheel steering gear can be expressed by the following formula (7).

[0198] X (s) (m·s 2 +b·s+k)+B (s) ·X (s) ·s=F (s) Formula (7)

[0199] Among them, in formula (7):

[0200] X (s) : The Laplace transform form of the screw stroke x stk , unit: meter (m);

[0201] B (s) : The Laplace transform form of the damping change amount B, unit: Newton / meter / second (N / m / s);

[0202] F (s) : The Laplace transform form of the screw output force F, unit: Newton (N);

[0203] m: The equivalent mass from the motor to the drive nut screw drive mechanism, determined by the specific structure design, is a constant, unit: kilogram (Kg);

[0204] b: The standard damping from the motor to the drive nut screw drive mechanism at standard room temperature, and its specific value is calibrated through test data analysis during the product development stage; unit: Newton / meter / second (N / m / s);

[0205] k: The equivalent elasticity between the drive nut and the screw from the motor, determined by the specific structure design, is a fixed constant, unit: Newton / meter (N / m);

[0206] s: Laplace operator.

[0207] From the above formula, the Laplace transform form of the damping change amount can be deduced as shown in the following formula (8).

[0208]

[0209] In formulas (7)-(8), the screw travel x stk The calculation process can be expressed by the following formula (9).

[0210]

[0211] Among them, in formula (9):

[0212] x stk : The screw travel at the third moment, unit: meter (m);

[0213] The motor rotation angle at the third moment, unit: radian (rad);

[0214] i: The transmission ratio from the motor rotation angle to the transmission nut screw, which is a constant.

[0215] In formulas (7)-(8), the calculation process of the screw output force F can be expressed by the following formula (10).

[0216]

[0217] Among them, in formula (10):

[0218] F: The screw output force, unit: Newton (N);

[0219] TQ mot : The second output torque of the motor at the third moment, unit: Newton-meter (N·m);

[0220] i: The transmission ratio from the motor rotation angle to the transmission nut screw, indicating the linear distance that the screw moves when the motor rotates one circle, which is a constant, unit: meter (m).

[0221] Thus, through the above formulas (7)-(10), after the motor controller obtains the second output torque and the motor rotation angle of the motor, it can first calculate the screw output force and the screw travel at the third moment respectively, then perform Laplace transforms on the screw travel and the screw output force respectively, substitute them into formula (8), solve to obtain the Laplace transform form of the damping change amount, and through the inverse Laplace transform, obtain the damping change amount.

[0222] After obtaining the damping change amount and the temperature at the mating part, the motor controller can calculate the grease temperature at the mating part through the following formula (11).

[0223] TMP gre =(B·a + T std )·k1 + TMP screw ·k2 Formula (11)

[0224] Among them, in formula (11):

[0225] TMP gre : The grease temperature at the mating part, unit: degree Celsius (°C);

[0226] B: The damping change amount, unit: Newton per meter per second (N / m / s);

[0227] a: The relationship coefficient between the grease temperature and the damping change amount at the mating part of the transmission nut and screw, determined by the grease selection and the mating method of the transmission nut and screw, unit: degree Celsius · meter / (Newton · second) (°C · m / (N · s));

[0228] T std : The standard room temperature corresponding to the standard damping b, unit: degree Celsius (°C);

[0229] k1: The weight coefficient, obtained through pre - calibration;

[0230] k2: The weight coefficient, obtained through pre - calibration;

[0231] TMP screw : The mating temperature at the current moment, unit: degree Celsius (°C).

[0232] Thus, after calculating the temperature at the mating part and the damping change amount, the motor controller can obtain the grease temperature through formula (11).

[0233] 302. According to the grease temperature, determine the target operating parameters of the motor. The target operating parameters are used to represent the operating state of the motor. When the motor operates with the target operating parameters, the grease temperature is less than or equal to the preset temperature.

[0234] After obtaining the grease temperature, the embodiment of the present application can determine the adjustment coefficient of the operating parameters of the motor based on the grease temperature, which is used to limit the operating parameters of the motor.

[0235] In a possible implementation manner, determining the target operating parameters of the motor according to the grease temperature includes:

[0236] Determine the target adjustment coefficient between the target operating parameters and the grease temperature according to the grease temperature;

[0237] Determine the target operating parameters according to the target adjustment coefficient and the grease temperature.

[0238] Optionally, the target operating parameters include the target output torque or the target output power.

[0239] Taking the target operating parameter as the target output power as an example, the process of determining the target output power of the motor according to the grease temperature in the embodiment of the present application can be represented by the following formula (12).

[0240] P mot = TMP gre ·h Formula (12)

[0241] Wherein, in Formula (12):

[0242] P mot : The target output power of the motor, unit: watt (W);

[0243] TMP gre : The grease temperature at the mating part, unit: degree Celsius (°C);

[0244] h: The power limit coefficient determined according to the grease temperature, obtained by calibration during the product development stage, i.e., the target adjustment coefficient, unit: watt per degree Celsius (W / °C); when the grease temperature is multiplied by this coefficient, the obtained output power can ensure that the grease temperature is less than or equal to the preset temperature.

[0245] Specifically, in the embodiment of the present application, after determining the grease temperature, the target adjustment coefficient can be determined through the corresponding relationship between the grease temperature and the motor output power, and substituted into the above Formula (12) to obtain the target output power of the motor.

[0246] Similarly, when the target operating parameter is the target output torque, in the embodiment of the present application, the technical personnel can also pre-calibrate the corresponding relationship between the grease temperature and the motor output torque in advance. The motor controller can find the target adjustment coefficient based on the grease temperature and the above corresponding relationship, and determine the target output torque of the motor based on the target adjustment coefficient and the grease temperature.

[0247] 303. Control the motor to operate with the target operating parameter.

[0248] After determining the target output torque or the target output power of the motor, the motor controller can control the motor to operate with the target output torque or with the target output power, so that the temperature of the grease is less than or equal to the preset temperature.

[0249] In summary, for a vehicle equipped with a rear-wheel steering gear, in order to avoid excessive temperature of the grease in the rear-wheel steering gear, the present application proposes a method for controlling the grease temperature. The specific implementation process of this method is as follows: During the operation of the rear-wheel steering gear, since the transmission efficiency between the transmission nut and the screw is the lowest, the temperature is most likely to overheat. Therefore, the temperature of the grease between the transmission nut and the screw is also most likely to be too high and volatilize and fail. The vehicle estimates the temperature of the grease between the transmission nut and the screw through the change in the cooperation temperature and damping between the transmission nut and the screw. Further, the operation of the motor is controlled by the grease temperature, so that the temperature of the grease during the operation of the motor is less than or equal to the preset temperature. Thus, through the above process, by adjusting the output of the motor, the temperature of the grease between the transmission nut and the screw is controlled not to be too high. Thereby, it is ensured that the temperature of the grease of the entire rear-wheel steering gear is not too high, avoiding the problem of the grease volatilizing and failing at high temperatures, and improving the working efficiency and control accuracy of the rear-wheel steering gear.

[0250] Figure 5 FIG. 4 is a schematic structural diagram of a device for controlling the temperature of grease provided by an embodiment of the present application. This device is applied to a rear-wheel steering system including a rear-wheel steering device, and the rear-wheel steering device includes a motor and a transmission nut and a screw that cooperate with each other.

[0251] Exemplarily, as Figure 5 shown, the device 500 includes:

[0252] A grease temperature determination module 501, configured to determine the temperature of the grease at the cooperation position according to the cooperation temperature at the cooperation position between the transmission nut and the screw and the change in damping generated during the process of the motor driving the transmission nut and the screw;

[0253] A parameter determination module 502, configured to determine the target working parameter of the motor according to the grease temperature, where the target working parameter is used to represent the operating state of the motor, and when the motor operates with the target working parameter, the grease temperature is less than or equal to the preset temperature;

[0254] An operation control module 503, configured to control the motor to operate with the target working parameter.

[0255] In a possible implementation manner, the parameter determination module 502 is specifically configured to: determine a target adjustment coefficient between the target working parameter and the grease temperature according to the grease temperature; and determine the target working parameter according to the target adjustment coefficient and the grease temperature.

[0256] Optionally, the device further includes: a matching temperature determination module, configured to obtain the starting moment when the rear-wheel steering device operates and the current ambient temperature; obtain multiple first operating parameters of the motor at multiple first moments during the period from the starting moment to the current moment; obtain multiple historical matching temperatures and multiple historical ambient temperatures corresponding to multiple second moments during the period from the starting moment to the previous moment of the current moment; determine the transmission heat generation generated by the transmission between the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple first operating parameters, the current moment, and the starting moment; determine the transmission heat dissipation generated by the transmission between the transmission nut and the screw during the operation of the rear-wheel steering device according to the multiple historical matching temperatures, the multiple historical ambient temperatures, the previous moment, and the starting moment; and determine the matching temperature according to the transmission heat dissipation, the transmission heat generation, and the current ambient temperature.

[0257] In a possible implementation manner, the multiple first operating parameters include multiple first output torques and multiple motor angular velocities, and the matching temperature determination module is specifically configured to: for any one of the multiple first moments, determine the first output torque and the motor angular velocity corresponding to the first moment according to the first moment, the multiple first output torques, and the multiple motor angular velocities; determine the output power of the motor at the first moment according to the first output torque and the motor angular velocity corresponding to the first moment; determine the transmission efficiency between the transmission nut and the screw at the first moment according to the first output torque corresponding to the first moment; and determine the transmission heat generation according to the output powers of the motor at the multiple first moments, the transmission efficiencies between the transmission nut and the screw at the multiple first moments, the current moment, and the starting moment.

[0258] In a possible implementation manner, the matching temperature determination module is further configured to: for any one of the multiple second moments, determine the historical matching temperature and the historical ambient temperature corresponding to the second moment according to the second moment, the multiple historical matching temperatures, and the multiple historical ambient temperatures; determine the temperature difference between the historical matching temperature and the historical ambient temperature; and determine the transmission heat dissipation according to the temperature differences at the multiple second moments, the starting moment, and the previous moment.

[0259] Optionally, the device further includes: a damping determination module, configured to control the motor to vibrate with a preset amplitude at a preset period, and when the motor vibrates with the preset amplitude, the output torque of the motor is less than or equal to a preset torque; obtain the second operating parameter of the motor at the third moment closest to the current moment before the current moment during the process of the motor vibrating with the preset amplitude; and determine the damping change amount according to the second operating parameter.

[0260] In a possible implementation, the damping determination module is specifically configured to: determine the screw output force at the third moment according to the second output torque; determine the screw stroke at the third moment according to the motor rotation angle; and determine the damping change amount according to the screw stroke and the screw output force.

[0261] Figure 6 FIG. 4 is a schematic structural diagram of a vehicle provided by an embodiment of the present application.

[0262] Exemplarily, as Figure 6 shown, the vehicle 600 includes: a memory 601 and a processor 602. Among them, an executable program code 6011 is stored in the memory 601, and the processor 602 is configured to call and execute the executable program code 6011 to execute a method for controlling the temperature of the grease.

[0263] In addition, an embodiment of the present application also protects a device, which may include a memory and a processor. Among them, an executable program code is stored in the memory, and the processor is configured to call and execute the executable program code to execute a method for controlling the temperature of the grease provided by an embodiment of the present application.

[0264] In this embodiment, the device may be divided into functional modules according to the above method example. For example, each functional module may correspond, or two or more functions may be integrated into one processing module. The above integrated module may be implemented in the form of hardware. It should be noted that the division of modules in this embodiment is illustrative, only a logical function division, and there may be other division methods in actual implementation.

[0265] In the case of dividing each functional module corresponding to each function, the device may further include a grease temperature determination module, a parameter determination module, an operation control module, etc. It should be noted that all relevant contents of each step involved in the above method embodiment can be cited in the function description of the corresponding functional module, and will not be repeated here.

[0266] It should be understood that the device provided by this embodiment is used to execute the above method for controlling the temperature of the grease, so the same effect as the above implementation method can be achieved.

[0267] In the case of adopting an integrated unit, the device may include a processing module and a storage module. Among them, when the device is applied to a vehicle, the processing module may be used to control and manage the actions of the vehicle. The storage module may be used to support the vehicle to execute relevant program codes, etc.

[0268] Among them, the processing module can be a processor or a controller, which can implement or execute various exemplary logic blocks, modules, and circuits shown in combination with the disclosure of this application. The processor can also be a combination that implements computing functions, such as including a combination of one or more microprocessors, a combination of digital signal processing (DSP) and a microprocessor, etc. The storage module can be a memory.

[0269] In addition, the device provided in the embodiments of this application can specifically be a chip, a component, or a module. The chip can include a connected processor and a memory. Among them, the memory is used to store instructions. When the processor calls and executes the instructions, the chip can execute a method for controlling the temperature of the grease provided in the above embodiments.

[0270] This embodiment also provides a computer-readable storage medium. Computer program code is stored in the computer-readable storage medium. When the computer program code runs on a computer, the computer is caused to execute the above-related method steps to implement a method for controlling the temperature of the grease provided in the above embodiments.

[0271] This embodiment also provides a computer program product. When the computer program product runs on a computer, the computer is caused to execute the above-related steps to implement a method for controlling the temperature of the grease provided in the above embodiments.

[0272] Among them, the device, the computer-readable storage medium, the computer program product, or the chip provided in this embodiment are all used to execute the corresponding methods provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding methods provided above, and will not be elaborated here.

[0273] Through the description of the above embodiments, those skilled in the art can understand that for the convenience and brevity of description, only the above division of each functional module is used for illustration. In practical applications, the above functions can be allocated to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above.

[0274] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection of devices or units can be in electrical, mechanical or other forms.

[0275] The above content is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for controlling grease temperature, characterized in that: The method is applied to a rear-wheel steering system including a rear-wheel steering device, wherein the rear-wheel steering device includes a motor and a transmission nut and a screw that cooperate with each other, and the method includes: Determine the grease temperature at the fitting point according to the fitting temperature of the driving nut and the screw rod and the damping change amount generated when the motor drives the driving nut and the screw rod; Determining a target operating parameter of the motor according to the grease temperature, wherein the target operating parameter is used to indicate an operating state of the motor, and when the motor operates at the target operating parameter, the grease temperature is less than or equal to a preset temperature; The motor is controlled to operate at the target operating parameters.

2. The method according to claim 1, characterized in that Determining the target operating parameters of the motor according to the grease temperature includes: Determining a target adjustment coefficient between the target operating parameter and the grease temperature according to the grease temperature; The target operating parameter is determined according to the target adjustment coefficient and the grease temperature.

3. The method according to claim 1, characterized in that The method further comprises: Obtaining the start time of the rear wheel steering device and the current ambient temperature; Acquire a plurality of first operating parameters of the motor at a plurality of first moments during a period from the starting moment to the current moment; Acquire multiple historical matching temperatures and multiple historical ambient temperatures corresponding to multiple second moments during the period from the start moment to the previous moment of the current moment; Determining the transmission heat generated by the transmission nut and the screw transmission during the operation of the rear wheel steering device according to the multiple first working parameters, the current time and the starting time; Determine the transmission heat dissipation generated by the transmission nut and the screw transmission during the operation of the rear wheel steering device according to the multiple historical matching temperatures, the multiple historical ambient temperatures, the previous moment and the starting moment; The matching temperature is determined according to the transmission heat dissipation, the transmission heat generation and the current ambient temperature.

4. The method according to claim 3, characterized in that The multiple first operating parameters include multiple first output torques and multiple motor angular velocities, and determining the transmission heat generated by the transmission nut and the screw transmission during the operation of the rear wheel steering device according to the multiple first operating parameters, the current time and the start time, includes: For any first moment among the plurality of first moments, determining a first output torque and a motor angular velocity corresponding to the first moment according to the first moment, the plurality of first output torques and the plurality of motor angular velocities; Determining the output power of the motor at the first moment according to the first output torque and the motor angular velocity corresponding to the first moment; determining a transmission efficiency of the transmission nut and the screw at the first moment according to a first output torque corresponding to the first moment; The transmission heat generation is determined according to the output power of the motor at the multiple first moments, the transmission efficiency of the transmission nut and the screw at the multiple first moments, the current moment and the starting moment.

5. The method according to claim 3, characterized in that: The step of determining the transmission heat dissipation generated by the transmission nut and the screw during the operation of the rear wheel steering device according to the multiple historical matching temperatures, the multiple historical ambient temperatures, the previous moment and the starting moment includes: For any second moment among the plurality of second moments, determining the historical matching temperature and the historical ambient temperature corresponding to the second moment according to the second moment, the plurality of historical matching temperatures and the plurality of historical ambient temperatures; determining a temperature difference between the historical matching temperature and the historical ambient temperature; The transmission heat dissipation is determined according to the temperature differences of the multiple second moments, the starting moment and the previous moment.

6. The method according to claim 1, characterized in that The method further comprises: According to a preset period, controlling the motor to vibrate with a preset amplitude, when the motor vibrates with the preset amplitude, the output torque of the motor is less than or equal to the preset torque; Acquire a second operating parameter of the motor at a third moment before the current moment and closest to the current moment during the vibration of the motor with the preset amplitude; The damping change amount is determined according to the second operating parameter.

7. The method according to claim 6, characterized in that The second operating parameter includes a second output torque and a motor rotation angle, and determining the damping change amount according to the second operating parameter includes: determining the screw output force at the third moment according to the second output torque; Determining the screw stroke at the third moment according to the motor rotation angle; The damping variation is determined according to the screw stroke and the screw output force.

8. A device for controlling the temperature of lubricating grease, characterized in that: The device is applied to a rear wheel steering system including a rear wheel steering device, wherein the rear wheel steering device includes a motor and a transmission nut and a screw that cooperate with each other, and the device includes: A grease temperature determination module, used to determine the grease temperature at the fitting point according to the fitting temperature of the driving nut and the screw rod and the damping change amount generated when the motor drives the driving nut and the screw rod; a parameter determination module, used to determine a target operating parameter of the motor according to the grease temperature, wherein the target operating parameter is used to indicate an operating state of the motor, and when the motor operates at the target operating parameter, the grease temperature is less than or equal to a preset temperature; The operation control module is used to control the motor to operate with the target operating parameters.

9. A vehicle, characterized in that: The vehicle comprises: A memory for storing executable program codes; A processor, configured to call and run the executable program code from the memory, so that the vehicle executes the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 7 is implemented.

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