Flexible motion control method and control circuit of AC magnetic actuator

Abstract

The present invention relates to a flexible motion control method and control circuit of an AC magnetic actuator. The flexible motion control method is that a first AC electronic switch and a second AC electronic switch are connected in a working circuit connected to the AC magnetic actuator, and the first AC electronic switch and the second AC electronic switch are respectively connected to a switch control circuit, and the switch control circuit controls the first AC electronic switch and the second AC electronic switch to implement mutually alternating on-off conversion, so as to adjust the actual working voltage of the AC magnetic actuator by pulse width modulation of the input AC voltage applied to the AC magnetic actuator, and then adjust the working current thereof, thereby realizing continuous adjustment of the output electromagnetic force of the AC electromagnet in the AC magnetic actuator, so as to realize flexible motion of the AC magnetic actuator. The present invention can implement flexible motion control on AC magnetic actuators such as AC brakes and AC contactors, thereby reducing power loss of the AC magnetic actuator, reducing temperature rise, and improving performance and service life.

Description

Technical Field

[0001] The invention relates to a control method for an AC magnetic actuator, in particular to a flexible motion control method and a control circuit for an AC magnetic actuator. Background Art

[0002] The AC magnetic actuator described in the present invention refers to a magnetic action device that works with AC power, including AC electromagnetic brakes, AC contactors, AC circuit breakers, etc. At present, such products are generally directly connected to the AC power grid, and the AC magnetic actuator is connected or disconnected by the on and off of the power switch.

[0003] Among them, the AC electromagnetic brake is an electromagnetic brake device with a brake spring and a brake push rod as the brake mechanism and an AC electromagnet as the brake opening mechanism. The advantage of the AC electromagnet is that it has a fast action response speed and is particularly suitable for use as a working part in the brake; but its disadvantage is that under AC working conditions, due to the large number of wires in the electromagnetic coil and the difficulty in heat dissipation, it causes serious heat generation, which often leads to the burning of the coil. Therefore, short service life is a major performance defect of the AC electromagnetic brake. The existence and difficulty of overcoming this problem have forced people to turn to the development and use of DC electromagnetic brakes. Although the DC electromagnetic brake has a long service life and can meet the use needs of product life in various application fields, one of its biggest problems is that due to the large inductance of the electromagnetic coil, its action response time generally reaches more than 100 milliseconds. The main technical requirements of the brake are "braking, braking quickly, and braking steadily". The action response time of more than several hundred milliseconds is undoubtedly difficult to meet the working needs of the brake, which is also the bottleneck problem that makes it difficult for DC electromagnetic brakes to be widely used.

[0004] Therefore, people try to find a solution on how to reduce the heat generated by AC electromagnetic brakes. Although there are various ways to reduce the heat generated by AC electromagnetic brakes, the result is that the structure of AC electromagnetic brakes is complicated, the cost is increased, and the product competitiveness is reduced.

[0005] Other AC magnetic actuators also have the problem of having a high heat generation that affects their service life, but the problem with AC electromagnetic brakes is the most prominent. Summary of the invention

[0006] One of the purposes of the present invention is to provide a flexible motion control method for an AC magnetic actuator to solve the problem that the service life of the AC magnetic actuator is reduced due to high heat generation during use.

[0007] The second object of the present invention is to provide a flexible motion control circuit for an AC magnetic actuator to reduce the power loss of the AC magnetic actuator and increase the service life of the AC magnetic actuator.

[0008] One of the purposes of the present invention is achieved as follows: a method for controlling the flexible motion of an AC magnetic actuator, wherein a first AC electronic switch is connected in series in a working circuit connecting the AC magnetic actuator, and a second AC electronic switch is connected in parallel at both ends of the AC magnetic actuator, wherein the first AC electronic switch and the second AC electronic switch are respectively connected to a switch control circuit, and the switch control circuit controls the first AC electronic switch and the second AC electronic switch to perform alternating on-off conversions, so as to adjust the actual working voltage on the AC magnetic actuator and then adjust its working current by pulse width modulation of the input AC voltage applied to the AC magnetic actuator, thereby continuously adjusting the output electromagnetic force of the AC electromagnet in the AC magnetic actuator to achieve flexible motion of the AC magnetic actuator.

[0009] The switch control circuit is a pulse width modulation circuit, and an output electromagnetic force setting circuit is arranged in the switch control circuit.

[0010] The second object of the present invention is achieved as follows: a flexible motion control circuit of an AC magnetic actuator, comprising:

[0011] The first AC electronic switch is connected in series in the working circuit of the AC magnetic actuator and is used to perform pulse width modulation on the AC voltage applied to the AC magnetic actuator, so as to adjust the magnitude of its working current by adjusting the magnitude of the actual working voltage applied to the AC magnetic actuator;

[0012] The second AC electronic switch is connected in parallel to both ends of the AC magnetic actuator and is used to control the on and off of the freewheeling circuit of the AC magnetic actuator;

[0013] A DC power supply connected in parallel to the AC power supply input terminal for providing a DC working voltage for the switch control circuit; and

[0014] The switch control circuit is respectively connected to the control end of the first AC electronic switch, the control end of the second AC electronic switch and the signal output end of the voltage sampling circuit, and is used to control the first AC electronic switch and the second AC electronic switch to implement alternating on-off conversion according to the set value of the output electromagnetic force and the sampled voltage signal, so as to adjust the actual working voltage of the AC magnetic actuator by pulse width modulation of the input AC voltage applied to the AC magnetic actuator, and then adjust the working current thereof, thereby continuously adjusting the output electromagnetic force of the AC electromagnet in the AC magnetic actuator to achieve flexible movement of the AC magnetic actuator.

[0015] The flexible motion control circuit of the present invention further comprises:

[0016] The voltage sampling circuit is connected in parallel to the access end of the AC power supply, and is used to detect the amplitude and phase of the AC power supply, and input the sampling signal to the switch control circuit. By adding the voltage sampling circuit, the voltage fluctuation of the AC power supply can be detected in real time, and the detection signal can be fed back to the switch control circuit. In this way, the AC output voltage of the flexible motion control circuit can be made more accurate by adjusting the pulse width, thereby effectively reducing or even avoiding the influence of the fluctuation of the AC power supply on the output voltage of the flexible motion control circuit.

[0017] The switch control circuit is a pulse width modulation circuit, and an output electromagnetic force setting circuit is arranged in the switch control circuit.

[0018] The first AC electronic switch and / or the second AC electronic switch may adopt the following structure: a diode VD 1 With diode VD 2 The first branch is formed by connecting the negative poles, and the diode VD 3 With diode VD 4 The second branch is formed by connecting the positive poles, the first branch is connected in parallel with the second branch, and the diode VD 1 With diode VD 2 The connection node and the diode VD 3 With diode VD 4 A power switch device V is connected between the connection nodes, and the control electrode of the power switch device V serves as the control end of the AC electronic switch, which is used to connect the switch control circuit.

[0019] The first AC electronic switch and / or the second AC electronic switch may also adopt the following structure: a diode VD 1 With power switch device V 1 The first branch is formed by reverse parallel connection, which consists of power switch device V 2 With diode VD 2 The first branch and the second branch are connected in series, and the power switch device V 1 The control electrode and power switch device V 2 The control electrode serves as the control end of the AC electronic switch and is used to connect the switch control circuit.

[0020] For AC electromagnetic brakes, the flexible action control circuit of the present invention is a flexible brake control circuit for controlling AC electromagnetic brakes. As the flexible brake control circuit, its input power supply is AC power, and its action object is the AC electromagnet in the AC electromagnetic brake. In fact, the flexible brake control circuit replaces the ordinary power switch to control the AC electromagnet. By performing high-frequency pulse width modulation (PWM) control on the input AC power supply voltage, the duty cycle of the PWM wave is adjusted, so that the effective value of the pulse AC voltage applied to the AC electromagnet is continuously adjusted, and the effective value of the current flowing through the AC electromagnet (due to the filtering effect of the inductance in the AC electromagnet, the current is a sine wave current with the same frequency as the power supply) can be continuously adjusted, so that the electromagnetic force output by the AC electromagnetic brake can be continuously adjusted from zero to the original rated value range, thereby achieving the purpose of flexible braking of the action object of the AC electromagnetic brake (such as: elevator brake, trolley travel brake of gantry crane, working brake of tower crane slewing mechanism, working brake of conveying machinery such as belt conveyor and cableway, etc.).

[0021] The present invention can implement flexible motion control on AC magnetic actuators such as AC brakes and AC contactors, and can enable the AC magnetic actuator to achieve the preferred working state of large current starting and small current maintenance, thereby reducing the power loss of the AC magnetic actuator, reducing the electrothermal heating and working temperature rise of the AC magnetic actuator, and correspondingly improving the control performance, use reliability and service life of the AC magnetic actuator. The control circuit of the present invention has the characteristics of small size, low cost, simple structure, flexible control, fast response, convenient operation and maintenance, high reliability, etc. Since AC electromagnets have much faster dynamic response characteristics than DC electromagnets, using the control circuit of the present invention to control AC electromagnets can greatly improve the control performance of the object of action.

[0022] The control method and the control circuit of the present invention can be used not only for AC brakes, but also for various AC magnetic motors such as AC contactors and AC circuit breakers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a circuit block diagram of the flexible motion control circuit of the present invention.

[0024] Figure 2 It is a schematic diagram of the control mechanism of the present invention.

[0025] Figure 3 It is a working waveform diagram of the flexible motion control circuit of the present invention.

[0026] Figure 4 It is a circuit block diagram of Embodiment 1 of the flexible motion control circuit of the present invention.

[0027] Figure 5It is a circuit block diagram of a switch control circuit composed of a single chip.

[0028] Figure 6 It is the software flow chart of the single chip microcomputer in the switch control circuit.

[0029] Figure 7 It is a circuit schematic diagram of a switch control circuit composed of a hardware circuit.

[0030] Figure 8 and Fig. 9 It is a circuit schematic diagram of two specific implementation methods of AC electronic switches. DETAILED DESCRIPTION

[0031] The following describes a specific implementation of the present invention by taking an AC electromagnetic brake as an object to be adjusted.

[0032] like Figure 1 As shown, the flexible motion control circuit of the present invention includes a voltage sampling circuit 3, a switch control circuit 4, a DC power supply 2, a first AC electronic switch 5 and a second AC electronic switch 6. The brake electromagnet 7 in the AC electromagnetic brake serves as an adjusted control object, and the AC power input 1 is an AC power supply.

[0033] exist Figure 2 In the control principle diagram of the flexible motion control circuit of the present invention, the dotted line box shows the equivalent circuit of the AC electromagnet in the AC electromagnetic brake. It consists of an inductor L d With a resistor R d The equivalent circuit formed by series connection. Figure 2 The switch in represents an AC electronic switch K. It includes contact A and contact B, contact A is connected to the power supply, and contact B is connected to the AC electromagnet. When the AC electronic switch K is connected to contact A, the entire power supply voltage is applied to the AC electromagnet; when the AC electronic switch K is connected to contact B, the AC power supply is disconnected, the AC electromagnet is short-circuited, and the voltage on it is zero. Although the voltage on the AC electromagnet is zero at this time, current will still flow through the AC electromagnet due to the inductive energy storage. By switching the AC electronic switch K at a suitable high frequency so that it can continuously switch between contact A and contact B, the voltage u acting on the AC electromagnet can be O The effective value U O Because the AC electromagnet is basically a linear element, the AC current i flowing through the inductor coil O The effective value of I OThe proportional continuous adjustment will be obtained, so that the electromagnetic force F output by the AC electromagnetic brake can be continuously adjusted, thereby realizing the flexible braking of the AC electromagnetic brake. The use of the flexible action control circuit of the present invention can effectively reduce the current flowing through the inductor coil, reduce the power loss of the AC electromagnetic brake accordingly, and greatly reduce the heat generation of the AC electromagnetic brake. The service life of the AC electromagnetic brake is steadily improved, thereby overcoming the disadvantage of the AC electromagnet having a short service life due to heating.

[0034] exist Figure 3 In the idealized waveform diagram of the flexible motion control circuit of the present invention, Figure 3 (a) is the AC input voltage u of the flexible action control circuit I Waveform diagram of Figure 3 (b) is the AC voltage u applied to the AC electromagnet coil after pulse width modulation by the flexible motion control circuit O The waveform diagram, where t 1 is the period when contact A of the AC electronic switch K is on and contact B is off, t 2 It is the period when contact A is disconnected and contact B is turned on, thus forming a pulse width modulation of the AC voltage; Figure 3 (c) is the AC current i acting on the AC electromagnet coil after the modulated AC voltage O Waveform diagram of .

[0035] The working principle of the flexible motion control circuit of the AC magnetic actuator of the present invention is embodied in formulas (1) to (3), Figure 2 The schematic diagram and Figure 3 In the idealized waveform diagram shown in FIG. 1 , formulas (1) to (3) represent the relationship between the electrical parameters corresponding to the action of the flexible motion control circuit on the AC electromagnet coil and the calculation formula for the output electromagnetic force.

[0036]

[0037] Depend on Figure 2 , Figure 3 From formulas (1) to (3), it can be seen that when the input effective value is U I When the AC power is high, adjust the conduction time t of the AC electronic switch K contact A 1 and / or disconnection time t 2 , both can make the effective value of the voltage on the AC electromagnet U O changes (Formula (1)), and accordingly, the current I flowing through the AC electromagnet OA continuous adjustment is obtained (Formula (2)), whereby the electromagnetic force F output by the AC electromagnetic brake can be adjusted continuously accordingly (Formula (3)) while other electromechanical parameters remain unchanged, thereby achieving the purpose of flexible braking (brake), thereby realizing the technical goal of the present invention.

[0038] Figure 4 The voltage sampling circuit in the circuit is composed of resistor R 1 and resistor R 2 The series branch formed by the series connection is connected in parallel at both ends of the AC input power supply. 1 With resistor R 2 The lead wire on the connection node between the two terminals is connected to the switch control circuit, and the detected detection signal u about the amplitude and phase of the AC power supply can be c The voltage sampling resistor R 1 and R 2 It can also be replaced by components such as voltage sensors.

[0039] It should be noted that the voltage sampling circuit is not necessary in the flexible action control circuit. The voltage sampling circuit is only used when the AC power input voltage U I When fluctuation occurs, the voltage U on the AC electromagnet can be O Adjusted to be more accurate.

[0040] Figure 4 The DC power supply in the circuit converts the input AC voltage into low-voltage DC power to provide the DC working power required for the switch control circuit. The DC power supply can be obtained from a switching power supply or a linear power supply.

[0041] Figure 4 The switch control circuit in the circuit adopts a pulse width modulation circuit, which can be an intelligent circuit with a single chip as the core ( Figure 5 ), or it can be a common circuit made up of hardware circuits ( Figure 7 ).

[0042] exist Figure 5 In the embodiment of the switch control circuit shown in the figure, the integrated circuit chip PIC12F675 is used as the main body of the pulse width modulation circuit, the output end of the voltage sampling circuit is connected to the 7-pin input end of the integrated circuit chip, and the 5-pin input end of the integrated circuit chip is connected to the potentiometer R W The sliding end of the potentiometer R W This is the output electromagnetic force setting circuit set in the switch control circuit. Adjust the potentiometer R W The set value of the output electromagnetic force of the AC electromagnetic brake can be changed. The output electromagnetic force setting circuit can also use components such as buttons, encoders or dip switches. The switch control circuit is based on the potentiometer RW The setting value and voltage detection signal u c , by applying a continuous pulse drive signal K to the first AC electronic switch and the second AC electronic switch A and K B , the first AC electronic switch and the second AC electronic switch can be controlled to be turned on and off alternately. When the first AC electronic switch is turned on, the second AC electronic switch is turned off; conversely, when the first AC electronic switch is turned off, the second AC electronic switch is turned on. The on-off switching time of the two AC electronic switches is relative to their t 1 + t 2 Although the circuit has a voltage sampling circuit, it can be used or not in the control program according to the control accuracy requirements.

[0043] like Figure 6 As shown in the figure, the specific working process of the switch control circuit as an intelligent circuit is: after the microcontroller is initialized, it first queries the potentiometer R W The voltage on the output is used to determine the output duty cycle and the conduction time t of the first AC electronic switch is calculated. 1 After that, an instruction is issued to control the first AC electronic switch to be turned on, and at the same time, the second AC electronic switch is turned off; after judging the on time t of the first AC electronic switch 1 The disconnection time t of the first AC electronic switch is calculated. 2 After that, an instruction is issued to control the first AC electronic switch to be turned off, and at the same time, the second AC electronic switch is instructed to be turned on; after judging the disconnection time t of the first AC electronic switch 2 When it is finished, it returns and enters the next working cycle. In this way, the pulse width modulation and continuous adjustment of the AC voltage applied to the brake electromagnet can be realized.

[0044] exist Figure 7 In the switch control circuit formed by the hardware circuit shown in the figure, the output of the third pin of the 555 time base circuit is connected to the driving circuit of the first AC electronic switch and the driving circuit of the second AC electronic switch. When the third pin outputs a high level, the first AC electronic switch is driven to be turned on and the second AC electronic switch is turned off; when the third pin outputs a low level, the first AC electronic switch is driven to be turned off and the second AC electronic switch is driven to be turned on, thereby realizing the reciprocal switching action of the two AC electronic switches.

[0045] The first AC electronic switch and the second AC electronic switch may be Figure 8 or Fig. 9 The structure of the AC electronic switch shown can of course also adopt other circuit structures that can achieve the function.

[0046] Figure 8 The AC electronic switch in the circuit is composed of a diode VD1 With diode VD 2 The first branch is formed by connecting the negative poles, and the diode VD 3 With diode VD 4 The second branch is formed by connecting the positive poles, the first branch is connected in parallel with the second branch, and the diode VD 1 With diode VD 2 The connection node and the diode VD 3 With diode VD 4 The power switch device V is connected between the connection nodes, and the positive output terminal of the power switch device V is connected to the diode VD 1 With diode VD 2 The negative output terminal of the power switch device V is connected to the diode VD 3 With diode VD 4 At the connection node, the control electrode of the power switching device V serves as the control end of the AC electronic switch to connect the switch control circuit.

[0047] Fig. 9 The AC electronic switch in the circuit is composed of a diode VD 1 With the power switch device V 1 The first branch is formed by reverse parallel connection, which consists of power switch device V 2 With diode VD 2 The first branch and the second branch are connected in series, and the power switch device V 1 The control electrode and power switch device V 2 The control electrode of is used as the control end of the AC electronic switch to connect the switch control circuit. The diode VD in the first branch 1 With the diode VD in the second branch 2 The connection can be made in a positive butt connection mode or a negative butt connection mode.

[0048] The power switch devices in the above two AC electronic switches can be selected from power devices such as MOS tubes, triodes or IGBTs. The AC power supply input to the AC flexible motion control circuit of the present invention can be 220V or 380V AC mains power, or it can be AC ​​power generated by an AC generator or other forms. For three-phase (or multi-phase) circuits, the flexible motion control method of the present invention is also applicable, which can generally be composed of three (or more) single-phase flexible motion control circuits of the present invention. The flexible motion control circuit of the present invention can be equipped with various backup or online UPS power supplies.

Claims

1. A flexible motion control method for an AC magnetic actuator, characterized in that: A first AC electronic switch is connected in series in a working circuit connecting the AC magnetic actuator, and a second AC electronic switch is connected in parallel at both ends of the AC magnetic actuator. The first AC electronic switch and the second AC electronic switch are respectively connected to a switch control circuit, and the switch control circuit controls the first AC electronic switch and the second AC electronic switch to perform alternating on-off conversion, so as to adjust the actual working voltage of the AC magnetic actuator by pulse width modulation of the input AC voltage applied to the AC magnetic actuator, and then adjust the working current thereof, thereby continuously adjusting the output electromagnetic force of the AC electromagnet in the AC magnetic actuator to achieve flexible movement of the AC magnetic actuator.

2. The flexible motion control method of the AC magnetic actuator according to claim 1 is characterized in that: The switch control circuit is a pulse width modulation circuit, and an output electromagnetic force setting circuit is arranged in the switch control circuit.

3. A flexible motion control circuit for an AC magnetic actuator, characterized in that: include: The first AC electronic switch is connected in series in the working circuit of the AC magnetic actuator and is used to perform pulse width modulation on the AC voltage applied to the AC magnetic actuator, so as to adjust the magnitude of its working current by adjusting the magnitude of the actual working voltage applied to the AC magnetic actuator; The second AC electronic switch is connected in parallel to both ends of the AC magnetic actuator and is used to control the on and off of the freewheeling circuit of the AC magnetic actuator; A DC power supply connected in parallel to the AC power supply input terminal for providing a DC working voltage for the switch control circuit; and The switch control circuit is respectively connected to the control end of the first AC electronic switch, the control end of the second AC electronic switch and the signal output end of the voltage sampling circuit, and is used to control the first AC electronic switch and the second AC electronic switch to implement alternating on-off conversion according to the set value of the output electromagnetic force and the sampled voltage signal, so as to adjust the actual working voltage of the AC magnetic actuator by pulse width modulation of the input AC voltage applied to the AC magnetic actuator, and then adjust the working current thereof, thereby continuously adjusting the output electromagnetic force of the AC electromagnet in the AC magnetic actuator to achieve flexible movement of the AC magnetic actuator.

4. The flexible motion control circuit of the AC magnetic actuator according to claim 3 is characterized in that: include: The voltage sampling circuit is connected in parallel to the input end of the AC power supply, and is used to detect the amplitude and phase of the AC power supply, and input the sampling signal to the switch control circuit.

5. The flexible motion control circuit of the AC magnetic actuator according to claim 3 or 4, characterized in that: The switch control circuit is a pulse width modulation circuit, and an output electromagnetic force setting circuit is arranged in the switch control circuit.

6. The flexible motion control circuit of the AC magnetic actuator according to claim 3 or 4, characterized in that: The structure of the first AC electronic switch and / or the second AC electronic switch is that a diode VD1 and a diode VD2 are connected in a negative pole manner to form a first branch, and a diode VD3 and a diode VD4 are connected in a positive pole manner to form a second branch. The first branch and the second branch are connected in parallel, and a power switch device V is connected between a connection node between the diode VD1 and the diode VD2 and a connection node between the diode VD3 and the diode VD4. The control electrode of the power switch device V serves as a control end of the AC electronic switch and is used to connect a switch control circuit.

7. The flexible motion control circuit of the AC magnetic actuator according to claim 6 is characterized in that: The positive output terminal of the power switch device V is connected to the connection node of the diode VD1 and the diode VD2, and the negative output terminal of the power switch device V is connected to the connection node of the diode VD3 and the diode VD4.

8. The flexible motion control circuit of the AC magnetic actuator according to claim 3 or 4, characterized in that: The structure of the first AC electronic switch and / or the second AC electronic switch is that a diode VD1 and a power switch device V1 are connected in reverse parallel to form a first branch, and a power switch device V2 and a diode VD2 are connected in reverse parallel to form a second branch. The first branch and the second branch are connected in series, and the control electrode of the power switch device V1 and the control electrode of the power switch device V2 serve as control terminals of the AC electronic switch and are used to connect a switch control circuit.

9. The flexible motion control circuit of the AC magnetic actuator according to claim 8 is characterized in that: The diode VD1 in the first branch and the diode VD2 in the second branch are connected in a positive butt connection manner or in a negative butt connection manner.

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