阅读说明：本技术 一种基于油泵电机电气特性的油温估算方法 (Oil temperature estimation method based on electrical characteristics of oil pump motor ) 是由 李庆旭 于 2020-11-30 设计创作，主要内容包括：本发明公开了一种基于油泵电机电气特性的油温估算方法,将油泵电机的输出转速调整到最低工作转速；将润滑油的油温调至最低工作温度,记录对应电流；按照温升步长提升油温,依次获取各油温对应的电流,直到将油温升至最高工作温度,获取最低工作转速下油温与油泵电机电流之间的映射关系,获取最低工作转速下油温与油泵电机电流的计算公式；按照转速升速步长逐步提高输出转速直到最高工作转速,记录每个输出转速下油温与电机电流的映射关系,得到各输出转速下的油温与油泵电机电流的计算公式。优点是：通过使用油温估算方法即可获取油温,降低了成本和硬件的故障率,避免了现有技术中油温传感器故障导致油温数据获取不准确的情况。(The invention discloses an oil temperature estimation method based on the electrical characteristics of an oil pump motor, which adjusts the output rotating speed of the oil pump motor to the lowest working rotating speed; adjusting the oil temperature of the lubricating oil to the lowest working temperature, and recording corresponding current; increasing the oil temperature according to the temperature rise step length, sequentially obtaining currents corresponding to the oil temperatures until the oil temperature is increased to the highest working temperature, obtaining a mapping relation between the oil temperature at the lowest working speed and the current of the oil pump motor, and obtaining a calculation formula of the oil temperature at the lowest working speed and the current of the oil pump motor; and gradually increasing the output rotating speed to the highest working rotating speed according to the rotating speed increasing step length, recording the mapping relation between the oil temperature and the motor current at each output rotating speed, and obtaining a calculation formula between the oil temperature and the oil pump motor current at each output rotating speed. The advantages are that: the oil temperature can be obtained by using the oil temperature estimation method, so that the cost and the failure rate of hardware are reduced, and the condition that the oil temperature data is not accurately obtained due to the failure of an oil temperature sensor in the prior art is avoided.)

1. An oil temperature estimation method based on electrical characteristics of an oil pump motor is characterized in that: comprises the following steps of (a) carrying out,

s1, determining the lowest working temperature and the highest working temperature of the lubricating oil to obtain the oil temperature rise step length; determining the lowest working rotating speed and the highest working rotating speed of an oil pump motor to obtain a rotating speed increasing step length;

s2, adjusting the output rotating speed of the oil pump motor to the lowest working rotating speed; adjusting the current oil temperature of the lubricating oil to the lowest working temperature, and acquiring the current of an oil pump motor; increasing the oil temperature of the lubricating oil according to the temperature rise step length, sequentially obtaining the current of an oil pump motor corresponding to each oil temperature until the oil temperature is increased to the highest working temperature, and obtaining the mapping relation between the oil temperature and the current of the oil pump motor at the lowest working rotating speed; performing polynomial fitting by using data in the mapping relation to obtain a calculation formula between the oil temperature and the current of the oil pump motor at the lowest working rotation speed;

and S3, changing the output rotating speed according to the rotating speed increasing step length, and repeating the step S2 in a circulating mode until the output rotating speed is equal to the highest working rotating speed, jumping out of the circulation mode, and obtaining a plurality of calculation formulas between the oil temperature and the current of the oil pump motor at the corresponding output rotating speed.

2. The oil temperature estimation method of electric motor electrical characteristics according to claim 1, characterized in that: polynomial fitting is carried out, a calculation formula between the oil temperature and the current of the oil pump motor at the preset rotating speed is obtained as follows,

T_rpmX＝f(I_rpmX)＝knX*I_rpmX^nX+

knX-1*I_rpmX^(nX-1)+……k1X*I_rpmX+k0X

the oil temperature corresponding to the Xth output rotating speed of the T _ rpmx oil pump motor is I _ rpmx, and the I _ rpmx represents the motor working current corresponding to the Xth output rotating speed of the oil pump motor; x is 1,2,3, … n; nx represents the degree of polynomial fitting, and knx, knx-1 … k11 and k01 respectively correspond to coefficients of the polynomial fitting; through the calibration process, the fitting coefficient of the polynomial can be known, so that when the motor current corresponding to each output rotating speed is known, the formula can be substituted, and the oil temperature under the corresponding output rotating speed is obtained through calculation.

Technical Field

The invention relates to the technical field of oil temperature estimation, in particular to an oil temperature estimation method based on the electrical characteristics of an oil pump motor.

Background

In a transmission system such as a motor and a reducer, certain abrasion inevitably exists in the processes of gear engagement and bearing rotation, and lubricating oil is usually adopted to lubricate the surfaces of components in order to reduce friction loss and protect transmission components. Lubricating oil is at the in-process that the part surface flows, except that reducing wear provides the lubrication function, can also take away the heat, through the mode that increases heat exchanger or refrigerator in oil circulation return circuit, gives off the heat that the oil temperature was taken away to realize oily cold effect. The circulation of lubricating oil in the oil circuit has multiple forms, and some throw away oil through centrifugal force, some adopt gear stirring oil, still some adopt the mode of oil pump pressurization oil spout. The relatively common bearings, gears and heating components inside the motor are often lubricated and cooled by spraying or throwing lubricating oil. Because of the inevitable height difference in the lubricating oil system, the oil pump is required to pressurize the lubricating oil system, so as to provide a certain lift and flow rate, thereby realizing the circulation of the lubricating oil in the oil path. And adjusting the rotating speed of an oil pump motor according to the actual operation requirement of the system, thereby realizing the adjustment of the flow rate and the pumping pressure of the oil pump.

Due to the physical characteristics of lubricating oil or cooling oil, when the oil temperature changes, the viscosity of the oil can obviously change, particularly when the oil temperature of the lubricating oil is lower, the viscosity-temperature curve of the oil changes in an exponential manner, and the increase of the viscosity leads to the increase of the load of an oil pump motor, so that the overload protection, the alarm or the failure of the oil pump motor is caused. Too high or too low oil temperature can also produce great influence to lubricated cooling effect, and oil itself can also go bad under extreme high temperature to influence the life-span of whole lubricating system. Therefore, in the current mainstream lubrication and cooling oil system, an oil temperature sensor is usually adopted to feed back to an oil pump control unit or a main control unit by monitoring an oil temperature signal in real time. When the oil temperature is too high, the oil flow is improved and the lubricating and radiating effects are enhanced by increasing the rotating speed of the oil pump; when the oil temperature is too low, the viscosity of the oil is increased, the rotating speed of the oil pump can be reduced by the oil pump motor according to the constant power control principle, and the problem of overload protection of the oil pump motor is avoided. Meanwhile, the oil temperature signal can be sent to an upper computer for displaying, monitoring and alarming the oil temperature.

The addition of the oil temperature sensor increases the flexibility and stability of the control of the oil circulation system. However, the additional oil temperature sensor also increases the system cost and the system complexity, and the fault and the signal distortion of the oil temperature sensor can also bring negative effects to the system protection. There is no simpler lower cost oil temperature sensing scheme currently available in the industry. The arrangement of the oil temperature sensor is limited by space and has a certain limitation. The oil temperature sensor can only represent the oil temperature at a local position, and the average oil temperature of the whole system still has a certain deviation with the oil temperature at the position of the oil temperature sensor.

Disclosure of Invention

The present invention is directed to a method for estimating an oil temperature based on electrical characteristics of an oil pump motor, so as to solve the foregoing problems in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

an oil temperature estimation method based on the electrical characteristics of an oil pump motor comprises the following steps,

s1, determining the lowest working temperature and the highest working temperature of the lubricating oil to obtain the oil temperature rise step length; determining the lowest working rotating speed and the highest working rotating speed of an oil pump motor to obtain a rotating speed increasing step length;

s2, adjusting the output rotating speed of the oil pump motor to the lowest working rotating speed; adjusting the current oil temperature of the lubricating oil to the lowest working temperature, and acquiring the current of an oil pump motor; increasing the oil temperature of the lubricating oil according to the temperature rise step length, sequentially obtaining the current of an oil pump motor corresponding to each oil temperature until the oil temperature is increased to the highest working temperature, and obtaining the mapping relation between the oil temperature and the current of the oil pump motor at the lowest working rotating speed; performing polynomial fitting by using data in the mapping relation to obtain a calculation formula between the oil temperature and the current of the oil pump motor at the lowest working rotation speed;

and S3, changing the output rotating speed according to the rotating speed increasing step length, and repeating the step S2 in a circulating mode until the output rotating speed is equal to the highest working rotating speed, jumping out of the circulation mode, and obtaining a plurality of calculation formulas between the oil temperature and the current of the oil pump motor at the corresponding output rotating speed.

Preferably, a polynomial fitting is performed to obtain a calculation formula between the oil temperature and the oil pump motor current at the preset rotation speed as follows,

T_rpmX＝f(I_rpmX)＝knX*I_rpmX^nX+

knX-1*I_rpmX^(nX-1)+……k1X*I_rpmX+k0X

the oil temperature corresponding to the Xth output rotating speed of the T _ rpmx oil pump motor is I _ rpmx, and the I _ rpmx represents the motor working current corresponding to the Xth output rotating speed of the oil pump motor; x is 1,2,3, … n; nx represents the degree of polynomial fitting, and knx, knx-1 … k11 and k01 respectively correspond to coefficients of the polynomial fitting; through the calibration process, the fitting coefficient of the polynomial can be known, so that when the motor current corresponding to each output rotating speed is known, the formula can be substituted, and the oil temperature under the corresponding output rotating speed is obtained through calculation.

The invention has the beneficial effects that: the mode that the corresponding power circuit and the detection circuit of the oil temperature sensor machine are used for obtaining the oil temperature in the prior art is eliminated, the structure of the oil temperature detection system is simplified, the oil temperature can be accurately obtained by using an oil temperature estimation method, and the cost and the fault rate of hardware are reduced. The oil temperature can be estimated by using the rotating speed and the current signal of the oil pump motor, and the condition that the oil temperature data is inaccurate due to the fault of an oil temperature sensor in the prior art is avoided.

Drawings

FIG. 1 is a schematic flow chart of a method for estimating oil temperature according to an embodiment of the present invention;

fig. 2 is a hardware system for oil temperature detection with an oil temperature estimation method built therein according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Example one

In the present embodiment, as shown in fig. 1, there is provided an oil temperature estimation method based on electrical characteristics of an oil pump motor, including the steps of,

s1, determining the lowest working temperature and the highest working temperature of the lubricating oil to obtain the oil temperature rise step length; determining the lowest working rotating speed and the highest working rotating speed of an oil pump motor to obtain a rotating speed increasing step length;

s2, adjusting the output rotating speed of the oil pump motor to the lowest working rotating speed; adjusting the current oil temperature of the lubricating oil to the lowest working temperature, and acquiring the current of an oil pump motor; increasing the oil temperature of the lubricating oil according to the temperature rise step length, sequentially obtaining the current of an oil pump motor corresponding to each oil temperature until the oil temperature is increased to the highest working temperature, and obtaining the mapping relation between the oil temperature and the current of the oil pump motor at the lowest working rotating speed; performing polynomial fitting by using data in the mapping relation to obtain a calculation formula between the oil temperature and the current of the oil pump motor at the lowest working rotation speed;

and S3, changing the output rotating speed according to the rotating speed increasing step length, and repeating the step S2 in a circulating mode until the output rotating speed is equal to the highest working rotating speed, jumping out of the circulation mode, and obtaining a plurality of calculation formulas between the oil temperature and the current of the oil pump motor at the corresponding output rotating speed.

In the embodiment, polynomial fitting is performed to obtain a calculation formula between the oil temperature and the oil pump motor current at the preset rotation speed as follows,

T_rpmX＝f(I_rpmX)＝knX*I_rpmX^nX+

knX-1*I_rpmX^(nX-1)+……k1X*I_rpmX+k0X

the oil temperature corresponding to the Xth output rotating speed of the T _ rpmx oil pump motor is I _ rpmx, and the I _ rpmx represents the motor working current corresponding to the Xth output rotating speed of the oil pump motor; x is 1,2,3, … n; nx represents the degree of polynomial fitting, and knx, knx-1 … k11 and k01 respectively correspond to coefficients of the polynomial fitting; through the calibration process, the fitting coefficient of the polynomial can be known, so that when the motor current corresponding to each output rotating speed is known, the formula can be substituted, and the oil temperature under the corresponding output rotating speed is obtained through calculation.

Example two

In this embodiment, assuming that the lowest operating speed is T _ rpm1, according to the calculation method in the first embodiment, the formula of the corresponding relationship between the lowest operating speed and the oil temperature is obtained as

T_rpm1＝f(I_rpm1)＝kn1*I_rpm1^n1+

kn1-1*I_rpm1^(n1-1)+……k11*I_rpm1+k01

In the above formula, T _ rpm1 represents the oil temperature corresponding to the lowest operating speed, I _ rpm1 represents the motor operating current corresponding to the lowest operating speed, and T _ rpm1 is a function of I _ rpm1, which is expressed in the above formula. N1 represents the fitting times of the polynomial, kn1, knx-1 … k11 and k01 respectively correspond to the fitting coefficients of the polynomial, and the fitting coefficients of the polynomial can be known through a calibration process, so that when the motor current corresponding to the lowest working speed is known, the motor current can be substituted into the formula to calculate the oil temperature.

By analogy, the rotation speed of the oil pump motor is increased, and polynomial fitting formulas corresponding to other typical oil pump working rotation speeds T _ rpm2, T _ rpm3 and … T _ rpmn can be obtained. According to a common oil pump control strategy, stepless speed regulation is not required for speed regulation of an oil pump motor, and the oil pump motor usually only works at a typical working rotating speed, such as 5-10 rotating speed working points, so that according to the actual running rotating speed of the oil pump motor, a polynomial function can be calibrated according to oil temperature-oil pump motor current of different rotating speeds, and the oil temperature is estimated.

T_rpm2＝f(I_rpm2)＝kn2*I_rpm2^n2+

kn2-1*I_rpm2^(n2-1)+……k12*I_rpm2+k02

T_rpm3＝f(I_rpm3)＝kn3*I_rpm3^n3+

kn3-1*I_rpm3^(n3-1)+……k13*I_rpm3+k03

……………………………………………….

T_rpmn＝f(I_rpmn)＝knn*I_rpmn^nn+

knn-1*I_rpmn^(nn-1)+……k1n*I_rpmn+k0n

If the oil pump motor needs stepless speed regulation under special working conditions and has a plurality of working rotating speeds, the oil temperature can be estimated by reducing the rotating speed increasing step length in the calibration process, increasing the data volume of the calibration rotating speed and the principle of the nearby rotating speed. Each output rotating speed can obtain a corresponding oil temperature relation formula. And solidifying the corresponding relation formulas into an oil temperature estimation algorithm.

The specific implementation steps of the oil temperature estimation method in the implementation process are illustrated,

in table 1, a certain type of oil pump motor is taken as an example for explanation, and it is assumed that the operating current range of the oil pump motor is 6-14A, and the operating range of the rotating speed of the oil pump motor is 500-3000 rpm. The calibration process is briefly described as follows:

step 1: firstly, defining a lubricating oil temperature working range, a minimum working temperature Tmin, a maximum working temperature Tmax and a temperature rise step length delta T in a calibration process; determining the lowest working speed n _ min and the highest working speed n _ max in the working speed range of the oil pump motor, and the working speed increasing step length delta n;

step 2: adjusting the output rotating speed of an oil pump motor to be n _ min-500 rpm by an oil pump motor controller, adjusting the oil temperature to the lowest working temperature Tmin by an oil temperature control system, and recording the current I0-500 rpm of the oil pump motor at the moment; then increasing the oil temperature by using the temperature step length delta T, and respectively recording the oil pump motor currents corresponding to different oil temperatures until the maximum working temperature Tmax; so far, the calibration of the mapping relation between the oil temperature and the current of the oil pump motor at the rotating speed of 500rpm is completed, as shown in the first row of data in table 1;

and 3, step 3: by using the current-oil temperature data at 500rpm in the first column in table 1, through polynomial fitting, T _500rpm ═ f (I0_500rpm) ═ kn1 ^ I0_500rpm ^ n1+ … kn1-1 ^ I0_500rpm ^ (n1-1) + … … k1 ^ I0_500rpm + k0 can be obtained, and through the formula, the oil temperature can be estimated according to the oil pump motor current under the condition that the oil pump motor working speed is 500 rpm;

and 4, step 4: increasing the operating speed of the oil pump motor to 1000rpm, obtaining oil temperature and current data at 1000rpm in the second row in table 1 according to the same method in the second step, and obtaining T _1000rpm ═ f (I0_1000rpm) ═ kn2 ^ I0_1000rpm ^ n2+ … kn2-1 ^ I0_1000rpm (n2-1) + … … k1 ^ I0_500rpm + k0 by the polynomial fitting, wherein the oil temperature can be estimated according to the current of the oil pump motor under the condition that the operating speed of the oil pump motor is known to be 1000 rpm;

and 5, step 5: referring to the method in the step 2-3, completing current-oil temperature data calibration and polynomial fitting of all operating rotation speed points to obtain T _2000rpm ═ f (I0_2000rpm), T _2500rpm ═ f (I0_2500rpm), and T _3000rpm ═ f (I0_3000rpm), so as to complete all data calibration, and solidifying the polynomial fitting formulas of the oil pump motor current and the oil temperature signals into an oil temperature estimation algorithm;

TABLE 1 oil temperature-current calibration data at different oil pump motor rotation speeds

In table 1, the minimum operating speed n _ min is assumed to be 500rpm, the maximum operating speed n _ max is assumed to be 3000rpm, and the speed increment step Δ n is assumed to be 500 rpm.

In actual operation, an oil temperature signal is calculated by a method for detecting the rotating speed and the current of the oil pump motor according to a polynomial fitting formula and then is output to an upper computer for monitoring and protection.

In this embodiment, the oil temperature may be detected in real time by a hardware system (as shown in fig. 2). The hardware system comprises a lubricating oil cavity of the motor/reducer, a circulating oil pipe, a circulating water pipe, a water pump, a radiator, a heat exchanger, a filter, an oil pump motor and a controller; an oil inlet and an oil outlet of the circulating oil pipe are communicated with the lubricating oil cavity, a filter and an oil pump are sequentially arranged on the circulating oil pipe along the flowing direction of the lubricating oil, the oil pump is connected with an oil pump motor, the oil pump motor is connected with a controller, and the circulating oil pipe positioned between the filter and the lubricating oil cavity passes through a heat exchanger; two ends of the circulating water pipe can be communicated with the water pump, a radiator is arranged on the circulating water pipe, and the circulating water pipe between the water pump and the radiator passes through the heat exchanger; the controller is provided with a complete oil temperature estimation method, the rotating speed and the current of the oil pump motor are obtained through the controller, the current lubricating oil temperature can be calculated and obtained according to a built-in algorithm, and when the oil temperature is too high, the temperature of the lubricating oil can be reduced through a circulating water pipe connected to the heat exchanger, so that the normal work of the motor or the speed reducer is ensured. Compared with the mode of detecting the oil temperature by using the temperature sensor in the prior art, the built-in oil temperature estimation method can more conveniently acquire the current oil temperature, simplifies the circuit structure of oil temperature detection, does not need to arrange the temperature sensor, does not need to increase other hardware structures, and has low cost. The situation that the oil temperature cannot be detected due to the fault of the oil temperature sensor is also avoided.

By adopting the technical scheme disclosed by the invention, the following beneficial effects are obtained:

the invention provides an oil temperature estimation method based on the electrical characteristics of an oil pump motor, which cancels the mode of acquiring oil temperature by using a corresponding power circuit and a detection circuit of an oil temperature sensor machine in the prior art, simplifies the structure of an oil temperature detection system, can accurately acquire the oil temperature by using the oil temperature estimation method, and reduces the cost and the failure rate of hardware. The oil temperature can be estimated by using the rotating speed and the current signal of the oil pump motor, and the condition that the oil temperature data is inaccurate due to the fault of an oil temperature sensor in the prior art is avoided.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.