Proportional electromagnet control method based on magnetic sensor

Abstract

The invention discloses a proportional electromagnet control method based on a magnetic sensor, and aims to solve the technical problem of poor control effect of a proportional electromagnet caused by low detection precision and reliability when an existing electromagnet uses the magnetic sensor to detect the position of an armature. The method comprises the following steps: firstly, closing the magnetic sensor, applying a high-speed section current greater than a corresponding action current to a coil of the proportional electromagnet, and after the high-speed section current is applied, starting the magnetic sensor to detect the position of an armature; and judging whether the armature moves in place or not according to the output of the magnetic sensor, otherwise, repeating the steps until the armature moves to a specified position. According to the method, the position of the armature can be accurately measured while the quick action of the armature is ensured, and the action efficiency and the action accuracy of the electromagnet are both improved.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnets, and in particular to a proportional electromagnet control method based on a magnetic sensor. Background Art

[0002] A magnetic sensor is a sensor that can detect magnetic fields. Commonly used magnetic sensors include Hall sensors and MR sensors. Hall sensors are the most widely used magnetic sensors with the highest market share; while MR sensors (especially TMR sensors) have higher sensitivity and lower noise, and are partially replacing Hall sensors. Hall sensors are sensors that use the change in current direction after the electrons in a semiconductor device are affected by a magnetic field (Lorentz force). TMR sensors are sensors based on the magnetoresistance effect, which uses the effect of a magnetic field on current to achieve detection. Specifically, a TMR sensor consists of a non-magnetic layer sandwiched between two metal magnetic layers. When there is no magnetic field, the current will pass through the two metal layers evenly. However, when there is a magnetic field, spin-orbit coupling occurs in the non-magnetic metal layer, causing the current to tend to pass through the metal layer in the same direction as the magnetic field, thereby changing the resistance of the sensor. This change in resistance is closely related to the change in the external magnetic field, so the change in the magnetic field can be sensed by measuring the resistance.

[0003] The electromagnet is mainly composed of a coil, a fixed iron core, an armature and a shell. The coil is usually made of a conductor. When it is energized, it will generate a magnetic field to magnetize the fixed iron core and the armature. The armature is a movable component. When the coil is energized, according to the principle of electromagnetic induction, a magnetic field will be generated around the coil. When this magnetic field acts on the armature, the armature will be attracted, so that the position of the armature can change with the change of the magnetic field strength, and the magnetic field around the armature will also change. Then, the position of the armature can be detected by detecting the magnetic field generated by the coil through a magnetic sensor.

[0004] During the use of the electromagnet, one control method known to the inventor is to first apply a larger driving current to the coil to generate a larger electromagnetic force, thereby increasing the reaction speed of the electromagnet, that is, setting a high-speed section. However, the inventor of the present application found in the process of implementing the technical solution in the embodiment of the present application that since the magnitude of the magnetic field generated by the electromagnet coil is proportional to the power supply current of the coil, even if the armature is at the same position, the magnetic field will increase with the increase of the coil driving current, which will cause the magnetic field corresponding to the same armature position to be different, thereby making it impossible for the magnetic sensor to achieve accurate measurement, and further resulting in the inability to achieve accurate control of the armature position of the proportional electromagnet based on the magnetic sensor signal.

[0005] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0006] In view of at least one of the above technical problems, the present disclosure provides a proportional electromagnet control method based on a magnetic sensor; it mainly solves the technical problem that the existing electromagnet has low detection accuracy and reliability when using a magnetic sensor to detect the armature position, resulting in poor proportional electromagnet control effect.

[0007] According to one aspect of the present disclosure, a proportional electromagnet control method based on a magnetic sensor is provided, wherein the proportional electromagnet includes a magnetic sensor arranged along the armature movement direction of the proportional electromagnet and at one end of the proportional electromagnet; the proportional electromagnet control method includes the following steps: (1) Turn off the magnetic sensor, assume that the current required to be applied to the coil when the armature moves to the specified position is the action current, apply a high-speed current greater than the corresponding action current to the coil of the proportional electromagnet, and the application time of the high-speed current is greater than the armature action time corresponding to the armature moving to the corresponding position; (2) After the high-speed section current application is completed, the magnetic sensor is started to detect the armature position; (3) Determine whether the armature has moved to the designated position based on the output of the magnetic sensor; otherwise, repeat steps (1) and (2) until the armature moves to the designated position.

[0008] In some embodiments of the present disclosure, in step (1), the high-speed section current is 1.3 to 1.5 times the coil action current.

[0009] In some embodiments of the present disclosure, in step (1), the high-speed current application time is greater than 3 to 6 times the armature action time.

[0010] In some embodiments of the present disclosure, in step (2), assuming that the inductance of the coil is L, the resistance of the coil is R, and the current change time constant of the coil is τ=L / R, then after the high-speed current is applied, the magnetic sensor is started after an interval of at least 5τ.

[0011] In some embodiments of the present disclosure, in the step (2), after the high-speed current is applied, the coil current is correspondingly reduced to the operating current.

[0012] In some embodiments of the present disclosure, the magnetic sensor is a Hall sensor.

[0013] In some embodiments of the present disclosure, the magnetic sensor is a TMR sensor.

[0014] One or more technical solutions provided in the embodiments of the present application have at least any of the following technical effects or advantages: 1. Applying high-speed current to the proportional electromagnet coil at the initial movement of the armature can generate a stronger electromagnetic force to drive the armature to overcome the static friction or spring resistance, thereby accelerating the armature movement, thereby improving the overall response efficiency of the electromagnet and avoiding hysteresis and delay.

[0015] 2. By reasonably limiting the current intensity and application time in the high-speed section, the problem of coil overheating causing damage to the electromagnet can be avoided, and at the same time, the armature can be ensured to move into place.

[0016] 3. Turn off the magnetic sensor during the high-speed current application stage, and start the magnetic sensor after a certain delay after the armature moves into place. This can avoid the magnetic field changes caused by increasing the response rate from affecting the measurement accuracy of the magnetic sensor, and ensure that the measurement value of the magnetic sensor can accurately reflect the armature position. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a partial structure of a proportional electromagnet in one embodiment of the present application.

[0018] Figure 2 1 is a curve diagram showing the relationship among the proportional solenoid control voltage, coil current, and armature position in one embodiment of the present application.

[0019] Figure 3 This is a curve diagram of the electromagnet control process parameters in one embodiment of the present application.

[0020] Figure 4 This is a curve diagram of electromagnet action parameters corresponding to different starting currents in one embodiment of the present application.

[0021] In the above figures, 1 is a fixed iron core, 2 is an armature, 3 is a coil, and 4 is a magnetic sensor. DETAILED DESCRIPTION

[0022] The programs involved or relied upon in the following embodiments are all conventional programs or simple programs in the technical field, and those skilled in the art can make conventional selections or adaptive adjustments according to specific application scenarios. In order to better understand the technical solution of this application, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] In order to solve the problem that different magnetic fields will be generated when the coil current is different under the same armature position, which causes the magnetic sensor to be unable to accurately measure the armature position, and thus unable to accurately control the armature action position. This example discloses a proportional electromagnet control method based on a magnetic sensor. In this embodiment, the proportional electromagnet includes a fixed iron core 1, an armature 2, a coil 3 and a magnetic sensor 4. Among them, one end side of the fixed iron core 1 is coaxially connected to a guide sleeve, and the armature 2 and the fixed iron core are coaxially arranged in the guide sleeve to move along the axial direction of the guide sleeve. The coil 3 is correspondingly wound at a position outside the guide sleeve to generate a magnetic field when energized, thereby realizing the change of the armature position by controlling the coil current. An end cap is provided at one end of the guide sleeve, and the magnetic sensor is fixedly embedded in the end cap, thereby realizing the judgment of the armature action position by detecting the magnetic field. In some other embodiments, the magnetic sensor is fixed at the outer edge of the end cap, and the plane where the magnetic sensor is located is perpendicular to the armature movement direction. In addition, in this embodiment, the magnetic sensor specifically adopts a TMR sensor, and in some other embodiments, the magnetic sensor adopts a Hall sensor.

[0024] See also Figure 2 In the figure, U is the control voltage signal, where Tp is the pulse width, T is the pulse period; I is the coil current, and X is the displacement of the armature. The inventor found in the process of implementing this embodiment that when the coil of the electromagnet is energized, due to the existence of the coil inductance, the current in the coil cannot instantly reach the current required for the armature to move, but needs to wait for a period of time before reaching the starting current for the armature to start moving, that is, the corresponding Figure 2 In the AB section of the middle current curve, during this time period, the thrust of the electromagnet cannot overcome the movement resistance of the armature or the resistance of the spring, so the armature will not produce any movement during this period. When the coil current of the electromagnet gradually increases until it reaches the starting current of the armature movement, the electromagnetic thrust generated by the electromagnet can overcome the resistance of the armature movement or the resistance of the spring, and the armature begins to move. However, the change in the position of the armature will cause the magnetic field to change, and then the coil cuts the changing magnetic field to generate an induced back electromotive force. The generation of this back electromotive force will resist the increase of the original current in the coil, causing the current in the coil to decrease instead. See Figure 2 The current curve shows an obvious inflection point B until point C. In this embodiment, the time from the electromagnet being energized to the armature being actuated is defined as the armature actuation time. When the coil current changes to point C, the armature position remains unchanged, the coil inductance remains unchanged, and the coil current begins to increase slowly, gradually reaching Figure 2 Point D. When the electromagnet coil is powered off, the signal voltage suddenly changes to zero, but due to the existence of inductance, the current at the coil cannot disappear instantly. At this time, the armature is still affected by the electromagnetic force, and the armature return spring cannot overcome the electromagnetic force of the electromagnet, and the armature position does not change. Figure 2The DE section corresponds to the power-off delay stage. As the coil current gradually decreases, the armature begins to move until the elastic force of the reset spring is sufficient to overcome the electromagnetic force generated by the residual current and the friction resistance required for the armature to move. The movement of the armature will cause the coil to generate an induced electromotive force and prevent the original current in the coil from decreasing. Figure 2 As a result, the coil current rises slightly through the inflection point E until it reaches point F, at which time the armature stops moving completely, the induced electromotive force becomes zero, and the coil current decays rapidly to zero. In this example, the time from when the electromagnet is powered off to when the armature stops moving is defined as the armature reset time.

[0025] Based on this, this example discloses a proportional solenoid control method, which includes the following steps: (1) Turn off the magnetic sensor and apply a high-speed current greater than the operating current to the coil of the proportional solenoid.

[0026] Applying different degrees of current to the proportional electromagnet can achieve different action positions of the armature. In this embodiment, the current applied to the coil required for the armature to move to the specified position is defined as the action current. Considering the need for rapid action of the electromagnet, it is necessary to avoid control errors caused by control delays; and after the electromagnet is energized and generates a magnetic field, the electromagnetic force acting on the armature first needs to overcome the static friction of the armature, and then the relative change of the armature position can be achieved. In order to enable the electromagnet to quickly break through the limitation of the static friction of the armature at the initial moment, this example applies a high-speed segment current greater than the action current to the coil of the proportional electromagnet at the initial moment. Among them, the high-speed segment current is 1.3 to 1.5 times the coil action current, so that by applying a large current to the coil of the proportional electromagnet, it can generate a stronger magnetic field and output a larger electromagnetic force, thereby quickly overcoming the static friction of the armature and allowing the armature to respond quickly. In this embodiment, the high-speed segment current is specifically 1.4 times the action current. In addition, in this embodiment, the application time of the high-speed current is set to be greater than the armature action time required for the armature to move to the corresponding position; specifically, the application time of the high-speed current in this example is greater than 3 to 6 times the armature action time, so as to ensure that the armature can reliably move to the position within the redundant action time, thereby avoiding the problem that the armature does not move to the position due to the high-speed current application time being too short, and avoiding the problem that the high-speed current application time is too long, resulting in increased power consumption and / or heating of the electromagnet. See Figure 3 , apply 36V control voltage to the proportional solenoid coil within 1 to 20ms to enable the armature to overcome static friction and achieve rapid movement; apply 24V voltage within 20 to 30ms, and turn off the electromagnet after 30ms, the voltage is 0V, thereby realizing proportional solenoid control.

[0027] In addition, considering that when the high-speed current is applied, the armature can be moved quickly and the response efficiency of the electromagnet can be improved, the magnetic field generated by the coil will also increase with the increase of the coil driving current, so that when the armature is in the same position and the coil driving current is in different stages, the magnetic field sensed by the magnetic sensor is different, which makes it impossible to establish a reliable and accurate correspondence between the magnetic field detected by the magnetic sensor and the armature position. For this reason, in this embodiment, before applying the high-speed current to the proportional electromagnet coil, the magnetic sensor is first turned off, that is, the power supply to the magnetic sensor is stopped. In this way, the magnetic field changes generated by the high-speed current are prevented from affecting the detection output of the magnetic sensor.

[0028] (2) After the high-speed current is applied, the magnetic sensor is started to detect the armature position.

[0029] After the high-speed current is applied, the armature movement ends. At this time, the coil current is reduced to the action current corresponding to the armature reaching the specified position, so as to reduce the power consumption of the electromagnet and avoid the heating of the coil. However, considering that when the current in the coil changes, due to the existence of the coil inductance, the current in the coil cannot be instantly reduced to the action current level, which causes the magnetic field to change in the process, and still cannot be detected by the magnetic sensor to accurately reflect the position of the armature. For this reason, in this embodiment, after the high-speed current is applied, the magnetic sensor is started to detect the armature position after a certain interval. Specifically, in this example, the inductance of the electromagnet coil is L, and the resistance of the coil is R, so that the time constant of the change of the current in the coil is τ=L / R, and then after the high-speed current is applied, after an interval of at least 5τ, the current in the coil is stabilized, and then the power supply to the magnetic sensor is restored, and the magnetic sensor is started to measure the magnetic field, so that the current position of the armature can be accurately determined.

[0030] (3) Determine whether the armature has moved to the specified position based on the output of the magnetic sensor. If it is detected that there is a position deviation between the actual position of the armature and the specified position, the difference between the two is used to control the distance the armature moves. Repeat steps (1) and (2), thereby forming a closed-loop feedback control until the armature moves to the specified position while satisfying the motion error.

[0031] See also Figure 4 In this example, the response time of the electromagnet under different voltage levels is tested, see Figure 4 (a) It can be seen that when a 36V voltage is applied to the coil, the current generated is significantly greater than the current corresponding to a 24V voltage; when a high-speed current greater than the operating current is applied to the coil, that is, Figure 4 (b) The movement amount under 36V voltage, the response time required for the armature to move 2mm is 1.2ms; when controlling the armature movement, the action current is always applied, that is, when there is no high-speed current, the corresponding Figure 4 (b) shows the armature movement under 24V voltage. In this case, the response time required for the armature to move 2mm is 1.75ms. Therefore, the setting of high-speed current can make the armature respond quickly and improve the efficiency of the electromagnet.

[0032] Although some preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0033] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the inventive concept. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A proportional electromagnet control method based on a magnetic sensor, characterized in that: The proportional electromagnet includes a magnetic sensor arranged along the armature movement direction of the proportional electromagnet and at one end of the proportional electromagnet; the proportional electromagnet control method includes the following steps: (1) Turn off the magnetic sensor, assume that the current required to be applied to the coil when the armature moves to the specified position is the action current, apply a high-speed current greater than the corresponding action current to the coil of the proportional electromagnet, and the application time of the high-speed current is greater than the armature action time corresponding to the armature moving to the corresponding position; (2) After the high-speed section current application is completed, the magnetic sensor is started to detect the armature position; (3) Determine whether the armature has moved to the designated position based on the output of the magnetic sensor; otherwise, repeat steps (1) and (2) until the armature moves to the designated position.

2. The proportional solenoid control method according to claim 1, characterized in that: In the step (1), the high-speed section current is 1.3 to 1.5 times the coil operating current.

3. The proportional solenoid control method according to claim 1, characterized in that: In the step (1), the high-speed current application time is greater than 3 to 6 times the armature action time.

4. The proportional solenoid control method according to claim 1, characterized in that: In step (2), assuming that the inductance of the coil is L, the resistance of the coil is R, and the current change time constant of the coil is τ=L / R, then after the high-speed current is applied, the magnetic sensor is started after an interval of at least 5τ.

5. The proportional solenoid control method according to claim 1, characterized in that: In the step (2), after the high-speed current is applied, the coil current is correspondingly reduced to the operating current.

6. The proportional solenoid control method according to claim 1, characterized in that: The magnetic sensor is a Hall sensor.

7. The proportional solenoid control method according to claim 1, characterized in that: The magnetic sensor is a TMR sensor.

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