A method for testing the braking time of a motor brake

Abstract

The present invention discloses a method for testing the braking time of an electric motor brake, which includes the following steps: Step S1, initial operation: The brake is in a non-enabled state, and the motor under test runs at a stable speed; Step S2, implement braking deceleration: Cut off the power supply, enable the brake, and the motor under test implements braking deceleration. The current detection module and the speed detection module continuously collect current signals and speed signals, and the main control module records the phase current i of the motor a , i b , i c data decaying with time, records the data of the rotor speed Ω of the motor changing with time, and simultaneously records the system operation time t; Step S3, data sampling and processing; S4: calibrate the start and end times; Step S5, calculate the braking time. The present invention realizes the precise synchronous triggering and time measurement in the dynamic process of the motor, and makes the measurement process of the controller precisely synchronized with the dynamic movement process of the motor, thereby improving the time measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the field of testing technology, and in particular relates to a motor performance testing method. Background Art

[0002] In production equipment such as hoists, cranes, and elevators, motors usually operate under frequent start-stop, speed change, or braking conditions. When equipment fails and may cause a risk of flying or falling, the motor's rapid brake performance is an important indicator for measuring system safety. Factors that affect the brake performance mainly include braking torque, braking reaction time, brake clearance, etc., which are characterized as braking time from the braking effect. The so-called braking time is the time it takes for the motor speed to drop from the rated speed to zero when the motor and the coaxially connected brake are powered off at the same time under normal rated working conditions. The braking time is generally short, in milliseconds, and its value determines the performance of the motor braking system. The national standard GB / T34114-2017 "General Technical Conditions for Electromagnetic Brakes for Motors" and the industry standard JB / T JB / T7125-2010 "Technical Conditions for Small Planar Braking Three-Phase Asynchronous Motors" have made technical provisions for the inspection and testing of the dynamic rapid braking performance of motors, and clarified the inspection indicators, inspection methods, and inspection rules.

[0003] The traditional method for testing the braking time of a motor brake is mainly the waveform measurement method (Literature - Mi Yongcun, Analysis of the Braking Time Test of a Motor Brake Unit, Micromotors, 2007, 40(6):93-94,100.), where the motor under test with a brake is coaxially connected to the dynamometer tooling table, powered on until stable operation, and then the power is manually cut off and the brake is applied. During the deceleration process of the power-off brake, the motor stator voltage waveform is sampled and recorded with an oscilloscope, and the voltage waveform is manually measured to obtain the deceleration time. This method is currently the main testing method used by quality inspection agencies. It has the disadvantages of low measurement accuracy and large repeatability errors. The main reasons are as follows: 1. The starting time is not accurately calibrated. At the beginning of the braking process, the starting point is judged only based on the slow change process of the motor terminal voltage waveform as the speed decreases. The characteristics are not obvious and difficult to observe; 2. The ending time is not accurately calibrated. The motor is judged to be stationary by the amplitude of the voltage waveform dropping to zero. The small amplitude of the motor's back-electromotive force voltage at low speed and the poor signal-to-noise ratio are not taken into account, which is nonlinearly related to the speed, thus causing errors in the judgment of the time point; 3. The idle action time of the brake clearance cannot be measured (the terminal voltage is only related to the motor speed, and the voltage cannot reflect the braking clearance). In response to the above problems, patent CN200620051083.8 "A new device for measuring the opening and braking time of the motor brake" adopts the method of installing a rotary encoder on the motor output shaft to directly and accurately measure the motor speed, and the PLC controls the motor power-off and brake holding signal, and manually gives the braking start time. This method improves the calibration error problem of the braking start and end time, but adds a PLC system and an electronic control connection with the brake, which makes the system complex, costly and affects the test efficiency. Patent CN201820792065.8 "A braking performance test device for a controllable braking device" adds a variable frequency speed regulation device for driving the motor under test to the test system, and obtains performance parameters such as braking time through online measurement and calculation by the sensors of the variable frequency speed regulation system. This solution not only requires the modification of existing wiring and installation, but also requires matching with a dedicated frequency converter, which also increases the complexity of the system and is not suitable for applications where rapid and large-scale motor detection is required. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a braking time testing method for a motor brake to improve the accuracy, consistency and speed of time measurement, while avoiding high-cost and complex modifications to the original motor dynamometer system, simplifying the testing process and eliminating human interference factors.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: a method for testing the braking time of a motor brake, which performs data acquisition and analysis and calculation through a contactless motor braking test device, wherein the contactless motor braking test device comprises a current detection module, a speed detection module, and a main control module, wherein the current detection module is used to detect the real-time current of the motor, the speed detection module is used to detect the speed of the motor, and the main control module comprises a single-chip microcomputer and a braking time analysis algorithm running on the single-chip microcomputer. The specific testing process comprises the following steps:

[0006] Step S1, initialization operation: fix the motor under test with the brake on the tooling stand, supply power to the motor under test and the brake, the brake is in a non-enabled state, and the motor under test runs at a stable speed;

[0007] Step S2, implement braking deceleration: cut off the power supply, enable the brake, implement braking deceleration on the motor under test, the current detection module and the speed detection module continuously collect the current signal and speed signal, and the main control module records the motor phase current i a ,i b ,i c Data that decays over time, records the data of the motor rotor speed Ω changing over time, and also records the system operation time t;

[0008] Step S3, data sampling processing: the phase current value i that changes with time a (t),i b (t),i c (t) is processed to eliminate zero drift, expressed as:

[0009]

[0010] where i a0 ,i b0 ,i c0 is the zero drift value of the alternating current, and then the sinusoidal alternating current i a1 (t),i b1 (t),i c1 (t) Calculate the effective value of phase current I, expressed as:

[0011]

[0012] S4: Calibrate the start and end times. According to the curves of the effective value of the phase current I and the rotational speed Ω changing with time, the period from t0 to t3 is the entire braking process from when the motor and the brake are powered off simultaneously until the motor stops. Among them, t < t0 is the initial steady-state operation stage before braking, t = t0 is the start time of the braking process, t0 < t < t1 is the power-off process, t1 < t < t2 is the brake actuation gap, t2 < t < t3 is the deceleration process, t = t3 is the end time of the braking process. Record the time value t1 when the current decays to 0, record the time value tk when the current decays to I(tk) = 0.37I at point K, and record the time value t3 when the rotational speed is 0;

[0013] Step S5, calculate the braking time: There are inductive coils in the motor and the brake. During the power-off process of the current, the current decays according to the exponential law and satisfies:

[0014]

[0015] where τ is the time constant. After a time τ, the amplitude decays to 0.37 times the initial value. When the amplitude decays to 0 after 4τ, the above time relationship can be expressed as:

[0016]

[0017] Solving from Equation (4), the start time t0 is:

[0018]

[0019] Then the total braking time is expressed as:

[0020]

[0021] Adopting the above technical solutions, the present invention has the following beneficial effects:

[0022] By verifying the effective current at the motor input terminal to determine the test start time and detecting the real-time rotational speed of the motor rotor to determine the test end time, precise synchronous triggering and time measurement of the motor dynamic process are achieved. Among them, the current characteristic calibration technology can quickly identify the load change and power-off action of the motor drive system under sudden given external control signals, making the measurement process of the controller precisely synchronized with the dynamic movement process of the motor, thereby improving the time measurement accuracy.

[0023] The open-close type Hall current sensor is suspended and nested on the outer ring side of the motor wire to collect the real-time current signal of the motor. The non-contact magnetic encoder is used to sample and obtain the angular position information θ of the motor rotor, and the speed information Ω is obtained by the phase-locked loop observer algorithm. It avoids costly and complex transformation of the original motor dynamometer system, simplifies the test process and eliminates human interference factors.

[0024] The specific technical solutions and beneficial effects of the present invention will be described in detail in the following specific embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0026] Figure 1 This is the structural diagram of the non-contact braking time test device.

[0027] Figure 2 Flowchart for motor braking time test analysis.

[0028] Figure 3 This is the schematic diagram of the phase-locked loop speed observer.

[0029] Figure 4 This is the current and speed change curve of the motor braking process. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] During the dynamic operation of the motor system, the measurement process of the detection device needs to strictly match the action process of the device under test, which puts forward the requirement for the synchronization between the start time of the motor state change and the start time of the measurement. However, in the actual detection environment, the measurement system and the control system of the motor under test are independent of each other, and it is impossible to achieve data docking between the control signal and the measurement signal.

[0032] In response to the above key technical issues, such as Figure 1As shown, the present invention provides a contactless motor braking time measurement device, including a current detection module, a speed detection module, and a main control module, wherein the current detection module includes an open-and-close Hall current sensor and a current signal processing unit, wherein the open-and-close Hall current sensor is suspended and nested on the outer ring side of the motor line, and is used to collect the real-time current signal of the motor, and the current signal processing unit is electrically connected to the current sensor and the main control module, and is used to filter and amplify the current signal measured by the current sensor and send the processed signal to the main control module; the speed detection module includes a non-contact magnetic encoder and an encoding signal processing unit, wherein the non-contact magnetic encoder is suspended and nested on the outer ring side of the motor shaft, and is used to collect the position angle and rotation angular velocity of the motor shaft, and the encoding signal processing unit is electrically connected to the non-contact magnetic encoder and the main control module, and is used to shape and filter the output signal of the non-contact magnetic encoder, and send it to the main control module;

[0033] The main control module includes a single-chip microcomputer, a battery, a communication interface, and a human-machine interface. The single-chip microcomputer stores and runs a braking time analysis algorithm. The braking time analysis algorithm determines the start time of the test by verifying the effective current at the motor input terminal and determines the end time of the test by detecting the real-time speed of the motor rotor.

[0034] refer to Figure 2 As shown, a method for testing the braking time of a motor brake is provided, wherein data collection and analysis calculation are performed through a non-contact motor brake testing device, and the specific testing process includes the following steps:

[0035] Step S1, initialization operation: fix the motor under test with a brake on a tooling stand, supply power to the motor and the brake, the brake is in a disabled state, and the motor runs at a stable speed (the motor is powered by an external system and has nothing to do with the measuring device; the motor can be tested both with no load and with load);

[0036] Step S2, implement braking deceleration: cut off the power supply, enable the brake, implement braking deceleration on the motor under test, the current detection module and the speed detection module continuously collect the current signal and the speed signal, and the main control module records the motor phase current i a ,i b ,i c (Take a three-phase AC motor as an example. If it is a DC motor and a single-phase AC motor, only the single-phase current i a ,i b =i c =0) data that decays over time, records the data of the motor rotor speed Ω changing over time, and also records the system running time t (microcontroller us-level high resolution);

[0037] Step S3, data sampling processing: the current sensor samples and obtains the phase current value i that changes with time a (t),ib (t), i c (t), the zero - drift of the phase current is eliminated and expressed as:

[0038]

[0039] where i a0 , i b0 , i c0 is the zero - drift value of the AC quantity. Then, from the sinusoidal AC quantity i a1 (t), i b1 (t), i c1 (t), the effective value I of the phase current is calculated and expressed as:

[0040]

[0041] The AC quantity is converted into a DC quantity to facilitate the judgment of the zero - crossing point of the amplitude in the next step. If the zero - crossing point of the AC current is directly judged, the zero - crossing point of the sine waveform will cause a misjudgment of zero amplitude.

[0042] The non - contact magnetic encoder samples to obtain the motor rotor angular position information θ, and the speed information Ω is obtained by the phase - locked loop observer algorithm. Among them, the speed tracking method based on the phase - locked loop enables the estimated values of the angle and speed to track the true values through a closed - loop control loop, and has strong anti - interference ability. Its structure is as Figure 3 shown.

[0043] S4: Calibrate the start and end times. Refer to the curves of the effective value I of the phase current and the speed Ω changing with time as shown in Figure 4 . t0 - t3 is the entire braking process from when the motor and the brake are powered off simultaneously to the motor being stationary. Among them, t < t0 is the initial steady - state operation stage before braking, t = t0 is the starting moment of the braking process, t0 < t < t1 is the power - off process, t1 < t < t2 is the brake - release action interval, t2 < t < t3 is the deceleration process, and t = t3 is the termination moment of the braking process. The single - chip microcomputer of the main control module records the moment value t1 when the current decays to 0, records the moment value t k when the current decays to I(t k ) = 0.37I, and records the moment value t3 when the speed is 0; among the above moments, the time points t0 and t2 occur randomly, and the amplitude of their ordinates is the same as that of the previous moments. Even considering the amplitude fluctuation during actual measurement, the signal - to - noise ratio is still insufficient. Therefore, these two time points cannot be judged by the amplitude. Therefore, t0 needs to be calculated.

[0044] Step S5, calculate the braking time: There are inductive coils in the motor and the brake. During the current power - off process, the current decays according to the exponential law and satisfies:

[0045]

[0046] Where τ is the time constant, and after a period of time τ, the amplitude decays to 0.37 (e -1 ) times, after 4τ, the amplitude decays to approximately 0, and the above time relationship can be expressed as:

[0047]

[0048] The starting time t0 can be obtained by solving equation (4):

[0049]

[0050] The total braking time is expressed as:

[0051]

[0052] The present invention is not limited to the above embodiment of measuring the braking time of a rotating AC motor, but can also be applied to various types of measured objects such as a rotating DC motor, a rotating stepping motor, a linear motor, and a brake electromagnet. The specific structure and the measured object are allowed to vary, and those skilled in the art can make various changes and deformations according to the present invention, as long as they do not deviate from the spirit of the present invention, they all fall within the scope defined by the claims attached to the present invention.

Claims

1. A method for testing the braking time of a motor brake, wherein data collection and analysis and calculation are performed through a contactless motor braking test device, wherein the contactless motor braking test device comprises a current detection module, a speed detection module, and a main control module, wherein the current detection module is used to detect the real-time current of the motor, the speed detection module is used to detect the speed of the motor, and the main control module comprises a single-chip microcomputer and a braking time analysis algorithm running on the single-chip microcomputer, and the testing process comprises the following steps: Step S1, initialization operation: fix the motor under test with the brake on the tooling stand, supply power to the motor under test and the brake, the brake is in a non-enabled state, and the motor under test runs at a stable speed; Step S2, implement braking deceleration: cut off the power supply, enable the brake, implement braking deceleration on the motor under test, the current detection module and the speed detection module continuously collect the current signal and the speed signal, and the main control module records the motor phase current i a ,i b ,i c Data that decays over time, records the data of the motor rotor speed Ω changing over time, and also records the system operation time t; Step S3, data sampling processing: the phase current value i that changes with time a (t),i b (t),i c (t) is processed to eliminate zero drift, expressed as: where i a0 ,i b0 ,i c0 is the zero drift value of the alternating current, and then the sinusoidal alternating current i a1 (t),i b1 (t),i c1 (t) Calculate the effective value of phase current I, expressed as: S4: Calibrate the start and end times. According to the curves of the effective value of the phase current I and the rotational speed Ω changing with time, the period from t0 to t3 is the entire braking process from when the motor and the brake are powered off simultaneously until the motor stops. Among them, t < t0 is the initial steady-state operation stage before braking, t = t0 is the start time of the braking process, t0 < t < t1 is the power-off process, t1 < t < t2 is the brake actuation gap, t2 < t < t3 is the deceleration process, t = t3 is the end time of the braking process. Record the time value t1 when the current decays to 0, and record the time value t k ) when the current decays to 0.37I at point K k , and record the time value t3 when the rotational speed is 0; Step S5, calculating the braking time: There are inductive coils in the motor and the brake, and the current decays according to the exponential law during the power-off process, satisfying: Where τ is the time constant. After a period of time τ, the amplitude decays to 0.37 times of the initial value. After 4τ, the amplitude decays to 0. The above time relationship can be expressed as: The starting time t0 can be obtained by solving equation (4): The total braking time is expressed as;

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