A method for measuring the rotor input power of a damping motor

Abstract

The present invention discloses a method for measuring the input power of a damping motor rotor, which includes: keeping the coil of the damping motor open-circuited, driving the rotor to rotate stably under multiple working conditions in turn, and recording the input power and speed of the rotor under each working condition as open-circuit data; connecting the coil of the damping motor to a load resistor, driving the rotor to rotate stably under multiple working conditions in turn, and recording the input power, current and speed of the rotor under each working condition as load data; fitting the damping function model between the damping and speed and current of the damping motor according to the open-circuit data with the load data; substituting the speed and current actually measured by the damping motor into the damping function model to obtain the damping value and thus obtain the input power. This method can greatly reduce the cost of power measurement, does not need to use physical deformation measuring devices such as strain gauges, and can be directly used on each product of the same batch.

Description

Technical Field

[0001] The invention relates to the field of motor science, and in particular to a method for measuring the input power of a damping motor rotor. Background Art

[0002] Damping motors are often used to provide damping for active devices, such as bicycle trainers, and the power applied to damping motors by humans through the trainer is difficult to measure directly. The traditional method uses the method of calculating power by measuring the real physical deformation, which is expensive and is limited by the principle of strain measurement. A lot of calibration work needs to be done for each product separately. At the same time, when the environment changes, such as when the temperature changes, the measurement results will shift. Considering these shortcomings, there is an urgent need for a low-cost, universal, and stable power measurement method. Summary of the invention

[0003] The purpose of the present invention is to provide a method for measuring the input power of a damping motor rotor based on the above-mentioned deficiencies of the prior art. The method uses speed and current as independent variables to obtain power to solve the problems existing in the prior art of using strain to measure input power.

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] A method for measuring the rotor input power of a damping motor, comprising:

[0006] The coil of the damping motor is kept open-circuited, and the rotor is driven to rotate stably under multiple working conditions in sequence, and the input power and speed of the rotor under each working condition are recorded as open-circuit data;

[0007] Connect the coil of the damping motor to the load resistor, drive the rotor to rotate stably under multiple working conditions in turn, and record the input power, current and speed of the rotor under each working condition as load data;

[0008] According to the open circuit data, a damping function model between the damping, the rotation speed and the current of the damping motor is obtained by fitting the load data;

[0009] The measured rotation speed and current of the damping motor are substituted into the damping function model to obtain the damping value, and the rotor input power of the damping motor is calculated according to the damping value, the rotation speed, the angular acceleration and the moment of inertia.

[0010] A further improvement of the present invention is that the process of obtaining the damping function model between the damping and the speed and the current of the damping motor specifically includes:

[0011] A function model of mechanical damping is obtained by fitting the open circuit data;

[0012] For each working condition in the load data, the total damping is calculated according to the rotation speed and the input power, and the rotation speed is substituted into the function model of the mechanical damping to obtain the mechanical damping, and the electromagnetic damping under each working condition is obtained by subtracting the mechanical damping from the total damping;

[0013] The function model of electromagnetic damping is obtained by fitting the current and electromagnetic damping under various working conditions;

[0014] The function model of electromagnetic damping is added to the function model of mechanical damping to obtain a damping function model between damping, rotation speed and current.

[0015] A further improvement of the present invention is that the function model of the mechanical damping and the function model of the electromagnetic damping both adopt a cubic spline function model.

[0016] A further improvement of the present invention is that in the process of acquiring the open-circuit data, the rotation speed of each operating condition increases sequentially; in the process of acquiring the load data, the rotation speed and / or current of each operating condition increases sequentially.

[0017] The advantages of the present invention are as follows: the method can greatly reduce the cost of power measurement, does not require the use of physical deformation measuring devices such as strain gauges, and can be directly used on each product in the same batch. At the same time, the influence of changes in ambient temperature on power calculation results is greatly reduced, and various actual physical influences are fully considered in the calculation process, thereby improving the calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart of a method for measuring rotor input power for damping a motor;

[0019] Figure 2 It is a comparison chart between measured power and simulated power. DETAILED DESCRIPTION

[0020] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0021] Example: Figure 1 As shown, the embodiment of the present invention includes a method for measuring the rotor input power of a damping motor. The main principle of the method is that the damping of the damping motor during the rotation process can be expressed as:

[0022]

[0023] Among them, F is damping, B is magnetic induction intensity, I is current, l is the length of the conductor bar, μ is the friction coefficient, N is pressure, ρ l is the density of lubricating oil, v is the viscosity coefficient of lubricating oil, A is the friction contact area, is the gradient of the speed difference between the two lubricated parts, C is the air resistance coefficient, ρ g is the air density, S is the characteristic area, and v is the speed. The first term on the right side of the formula is the electromagnetic force on the energized coil in the magnetic field, the second and third terms are mechanical friction forces such as bearings, and the fourth term is the air resistance of the coil rotation; from the expression, it can be seen that the first term is mainly determined by the current, and the second, third, and fourth terms are mainly determined by the rotation speed.

[0024] For ease of understanding, formula (1) is a formula in a translational coordinate system, not a formula in a rotational coordinate system. It can be seen from formula (1) that the damping of the damping motor can be obtained according to the speed and current of the damping motor. On this basis, the rotor input power of the damping motor can be obtained through formula (2).

[0025] P=ω(T z +I M α)(2)

[0026] In the above formula, P is the rotor input power, ω is the speed, T z is the damping, that is, F in the translational coordinate system, I M is the moment of inertia of the damping motor, which can be measured by existing means, and α is the angular acceleration, which can be obtained by the speed difference.

[0027] like Figure 1 As shown, the method for measuring the rotor input power of the damping motor of this embodiment includes the following steps:

[0028] (S1) Determine a test condition similar to the target condition. For example, for a bicycle trainer, the power range should be in the range of 30-2000W.

[0029] (S2) Two groups of calibration tests are performed respectively. In the first group of calibration tests, the coil of the damping motor is kept open-circuited, and the rotor is driven to rotate stably under multiple working conditions in turn, and the input power and speed of the rotor under each working condition are recorded as open-circuit data. In the first group of tests, the speed of each working condition increases in turn. In the process of testing each working condition, it is necessary to wait until the speed is stable before measuring the rotor input power, so as to eliminate the influence of the moment of inertia on the input power. In the obtained open-circuit data, each working condition has a corresponding speed and input power measurement value.

[0030] (S3) In the second set of calibration tests, the coil of the damping motor is connected to the load resistor, and the rotor is driven to rotate stably under multiple working conditions in turn, and the input power, current and speed of the rotor under each working condition are recorded as load data. In the second set of calibration tests, the speed and / or current of each working condition are increased in turn, and the current and input power also need to be measured after the speed reaches stability. In the obtained load data, each working condition has corresponding measurement values ​​of speed, current and input power.

[0031] (S4) fitting the open circuit data with the load data to obtain a damping function model between the damping and the speed and current of the damping motor. This step adopts the principle disclosed by formula (1) for fitting, and the specific process includes:

[0032] (S41) A function model of mechanical damping is obtained by fitting the open-circuit data; the function model of mechanical damping adopts a cubic spline function model, and the corresponding mechanical damping can be obtained by inputting the actually measured rotation speed.

[0033] (S42) For each working condition in the load data, the total damping is calculated according to the rotational speed and the input power, and the rotational speed is substituted into the function model of the mechanical damping to obtain the mechanical damping, and the electromagnetic damping under each working condition is obtained by subtracting the mechanical damping from the total damping. When the rotational speed is stable, the total damping can be obtained by dividing the input power by the rotational speed.

[0034] (S43) Fitting the electromagnetic damping function model according to the current and electromagnetic damping under each working condition; in this embodiment, the electromagnetic damping function model adopts a cubic spline function model, and the value of the electromagnetic damping can be obtained by substituting the measured value of the current. Mechanical damping and electromagnetic damping are both fitted using a cubic spline function model. Compared with the traditional model, this fitting method can reflect high-order effects, and various damping related to speed and electromagnetic can be included in the fitting results, which is closer to the actual situation of the damping motor.

[0035] (S44) Adding the function model of electromagnetic damping to the function model of mechanical damping, to obtain a damping function model between damping, rotation speed and current.

[0036] (S5) Substituting the measured speed and current of the damping motor into the damping function model to obtain the damping value T Z , and according to the damping value T Z , speed ω, angular acceleration α and moment of inertia I M Calculate the rotor input power P of the damped motor.

[0037] In actual use, only the acquired speed and current can be used to bring the function model obtained through fitting into the theoretical formula of power for accurate calculation. The verification process of the method of this embodiment is introduced below:

[0038] (1) According to the method of this embodiment, a damping function model between the damping, speed and current of the damping motor is obtained when the damping motor is matched with the A resistor.

[0039] (2) In order to ensure the rigor of the verification, the damping motor is matched with another resistor B with a different resistance value, and the working conditions of the damping motor over a period of time are recorded, including current, speed, input power and other data.

[0040] (3) The current and speed groups measured when combined with resistor B are input into the damping function model obtained when combined with resistor A to obtain simulated power (simulated value of input power), which is compared with the corresponding measured power (measured value of input power) and the error is calculated. Figure 2 The curves of measured power and simulated power changing with time are given. Figure 2 It can be seen that the two curves almost coincide.

[0041] The comprehensive simulation power error is: 1.17%

[0042] Goodness of fit index R NL is: 0.9888

[0043] The following is the original data of the verification condition (cut Figure 2 (10-40s data)

[0044] Table 1 Original data of verification condition

[0045]

[0046]

[0047] It can be seen that the simulated power calculated by this method is in good agreement with the measured power, and the error between the simulated value and the measured value is basically around 1%, which has reached the industry-leading level.

[0048] The above embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modification, replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the rotor input power of a damping motor, characterized in that include: The coil of the damping motor is kept open-circuited, and the rotor is driven to rotate stably under multiple working conditions in sequence, and the input power and speed of the rotor under each working condition are recorded as open-circuit data; Connect the coil of the damping motor to the load resistor, drive the rotor to rotate stably under multiple working conditions in turn, and record the input power, current and speed of the rotor under each working condition as load data; According to the open circuit data, the damping function model between the damping, the rotation speed and the current of the damping motor is obtained by fitting the load data; Substituting the measured speed and current of the damping motor into the damping function model to obtain a damping value, and calculating the rotor input power of the damping motor according to the damping value, speed, angular acceleration and moment of inertia; The process of obtaining the damping function model between the damping and the speed and current of the damping motor specifically includes: A function model of mechanical damping is obtained by fitting the open circuit data; For each working condition in the load data, the total damping is calculated according to the rotation speed and the input power, and the rotation speed is substituted into the function model of the mechanical damping to obtain the mechanical damping, and the electromagnetic damping under each working condition is obtained by subtracting the mechanical damping from the total damping; The function model of electromagnetic damping is obtained by fitting the current and electromagnetic damping under various working conditions; The function model of electromagnetic damping is added to the function model of mechanical damping to obtain a damping function model between damping, rotation speed and current.

2. A method for measuring the rotor input power of a damping motor according to claim 1, characterized in that: The function model of the mechanical damping and the function model of the electromagnetic damping both adopt a cubic spline function model.

3. The method for measuring the rotor input power of a damping motor according to claim 1, characterized in that: In the process of acquiring the open-circuit data, the rotation speed of each working condition increases sequentially; in the process of acquiring the load data, the rotation speed and / or current of each working condition increases sequentially.

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