Current closed-loop control circuit and method for electromagnetic clutch

Abstract

The invention belongs to the technical field of servo control, and particularly relates to an electromagnetic clutch current closed-loop control circuit and method. Comprising a voltage conversion circuit, a current sampling circuit, a current monitoring circuit, a coil control circuit and a control module, and the control module comprises a current comparison module, a PI controller and a PWM generation module; each of the current sampling circuit and the current monitoring circuit sequentially comprises a differential acquisition circuit and a low-pass filter; the input end of the voltage conversion circuit receives a variable DC voltage. The PWM chopping is used for controlling the on and off of the lower switch tube, the magnitude of the output current is adjusted, the operation is simple, and the overall adaptability of the circuit function is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of servo control, and in particular relates to an electromagnetic clutch current closed-loop control circuit and method. Background Art

[0002] As one of the key components in the flight control system, the performance of the electric servo used to drive the aircraft control surface directly affects the operation of the entire flight control system. With the development of the flight control system, the switching of the working mode of the electric servo needs to be realized by the state control of the electromagnetic clutch. Therefore, the control of the electromagnetic clutch involves the mode switching of the flight control system, and the performance of the control circuit affects the safety of the flight control system. At the same time, the aviation industry is developing in the direction of low cost and fast replacement. The standardization and generalization of the design will greatly reduce the design time; the previous clutch control circuit has a reset and hold power supply, and the hardware cost is relatively high. At the same time, as the temperature changes, the resistance of the clutch coil changes, and the load current will also change accordingly, so that the power supply system needs to be designed according to the maximum current, which places too high requirements on the power supply system. In addition, different reset and hold voltages need to be designed for different clutch loads, resulting in low design reuse rate and prolonged development and verification cycle. Summary of the invention

[0003] Purpose of the invention: To propose a low-cost, high-efficiency, and high-reliability electromagnetic clutch current closed-loop control circuit and method.

[0004] Technical solution:

[0005] A current closed-loop control circuit for an electromagnetic clutch comprises: a voltage conversion circuit, a current sampling circuit, a current monitoring circuit, a coil control circuit, and a control module, wherein the control module comprises a current comparison module, a PI controller, and a PWM generation module; the current sampling circuit and the current monitoring circuit each comprise a differential acquisition circuit and a low-pass filter in sequence; the input end of the voltage conversion circuit receives a variable DC voltage;

[0006] The coil control circuit includes a first transistor 1, a sampling resistor 2, a clutch coil 3, a monitoring resistor 4, a second transistor 5, and a freewheeling diode 6, wherein the gate of the first transistor 1 is connected to the first output terminal of the current comparison of the control module; the output terminal of the voltage conversion circuit is connected to the drain of the first transistor 1; one end of the sampling resistor 2 is connected to the source of the first transistor 1 and the positive differential input terminal of the current sampling circuit, and the other end of the sampling resistor 2 is connected to one end of the clutch coil 3, the negative electrode of the freewheeling diode 6, and the negative differential input terminal of the current sampling circuit; one end of the monitoring resistor 4 is connected to the other end of the clutch coil 3, the positive electrode of the freewheeling diode 6, and the positive differential input terminal of the current monitoring circuit, and the other end of the monitoring resistor 4 is connected to the drain of the second transistor 5 and the negative differential input terminal of the current monitoring circuit;

[0007] The source of the second transistor 5 is grounded; the gate of the second transistor 5 is connected to the output end of the PWM generation module of the control module; the output end of the current sampling circuit is connected to the first input end of the current comparison module; the output end of the current monitoring circuit is connected to the second input end of the current comparison module; the third input end of the current comparison module is used to receive an enable signal; the current command is input into the PI controller after the difference is made between the output of the current sampling circuit, and the second output end of the current comparison module is connected to the enable input end of the PWM generation module.

[0008] Preferably, the voltage conversion circuit specifically uses a DC / DC module to convert the 18V-32V variable DC voltage input into a stable 28V DC voltage to supply the clutch coil.

[0009] Preferably, the first transistor 1 and the second transistor 5 are insulated gate field effect transistors.

[0010] Preferably, the low-pass filter is an active first-order low-pass filter.

[0011] Preferably, the period of the PWM wave generated by the PWM generation module is parameterized according to the resistance and inductance values ​​of the clutch coil 3 .

[0012] Preferably, the differential acquisition circuit in the current sampling circuit is implemented using an operational amplifier with a common mode rejection ratio greater than 50V.

[0013] Preferably, the current carrying capacity of the freewheeling diode 6 , the first transistor 1 , and the second transistor 5 is greater than 1.5 times the maximum current of the clutch coil 3 .

[0014] A method for controlling an electromagnetic clutch current closed-loop, the method being performed by means of the electromagnetic clutch current closed-loop control circuit, the method comprising:

[0015] Step 1: The current command signal and the current signal output by the current sampling circuit are differentially controlled to perform closed-loop control, and a modulated PWM wave is output through a PI controller to drive the second transistor 5;

[0016] Step 2: The current comparison module determines whether to enable the output of the upper and lower tube control signals based on whether the current values ​​fed back by the monitoring circuit and the current sampling circuit are equal;

[0017] The enable signal E of the current comparison module n Contains 0 and 1, corresponding to two working modes. n =1 and the current comparison module outputs the upper tube normally-on enable signal according to the current values ​​fed back by the monitoring circuit and the current sampling circuit being equal, and controls the first transistor 1 to be normally-on; at the same time, enables the PWM output to control the second transistor 5 to be turned on;

[0018] Dangdang E n =1 and the current comparison module receives different current values ​​from the monitoring circuit and the current sampling circuit, or E n =0, at this time, the current comparison module outputs the upper tube shutdown enable signal to control the first transistor 1 to be turned off, and at the same time enables PWM not to output to control the second transistor 5 to be turned off.

[0019] Beneficial effects:

[0020] The clutch current control circuit and current loop control method proposed by the present invention are concise and practical. The PWM chopping control is used to turn on and off the lower switch tube to adjust the output current. The operation is simple and the overall adaptability of the circuit function is improved. A current monitoring circuit is provided to effectively monitor whether there is a fault in the clutch current loop. The upper and lower tubes are used to control the circuit, which can ensure the reliability of the loop shutdown and ensure safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for use in the embodiment of the present invention. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A connection diagram of each circuit module involved in the present invention;

[0023] Figure 2 The following is a detailed schematic diagram of the clutch control circuit.

[0024] The components in the drawings are indicated by numbers:

[0025] 1-first transistor, 2-sampling resistor, 3-clutch coil, 4-monitoring resistor, 5-second transistor, 6-freewheeling diode. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0028] The embodiment of the present invention provides a clutch current control circuit and a current loop control method, which are used to detect the real-time current when the clutch is working, and at the same time close-loop adjust the feedback current so that it can follow the system current setting with high dynamics and without overshoot, including: a voltage conversion circuit, a current sampling circuit, a control module, a coil control circuit, and a current monitoring circuit.

[0029] A clutch control circuit and a clutch current control method are proposed.

[0030] In the first aspect, an electromagnetic clutch current closed-loop control circuit is proposed, which is also an implementation platform of the current closed-loop control method of the present invention; the electromagnetic clutch current closed-loop control circuit includes a voltage conversion circuit, a current sampling circuit, a current monitoring circuit, a coil control circuit, and a control module.

[0031] The voltage conversion circuit uses a DC / DC (Direct current / Direct current) module to convert the 18V to 32V variable DC voltage input into a stable 28V DC voltage to supply the clutch coil, ensuring that the output voltage is stable when the external power supply changes from 18V to 32V.

[0032] The coil control circuit includes a first transistor 1 , a sampling resistor 2 , a clutch coil 3 , a monitoring resistor 4 , a second transistor 5 , and a freewheeling diode 6 .

[0033] Both the current sampling circuit and the monitoring circuit collect voltage signals through sampling resistor voltage division, and transmit them to the processing circuit after filtering and amplification by an active first-order low-pass filter.

[0034] Among them, the gate of the first transistor 1 is connected to the first output terminal of the current comparison of the control module; the output terminal of the voltage conversion circuit is connected to the drain of the first transistor 1; one end of the sampling resistor 2 is connected to the source of the first transistor 1 and the positive differential input terminal of the current sampling circuit, and the other end of the sampling resistor 2 is connected to one end of the clutch coil 3, the negative electrode of the freewheeling diode 6 and the negative differential input terminal of the current sampling circuit; one end of the monitoring resistor 4 is connected to the other end of the clutch coil 3, the positive electrode of the freewheeling diode 6 and the positive differential input terminal of the current monitoring circuit, and the other end of the monitoring resistor 4 is connected to the drain of the second transistor 5 and the negative differential input terminal of the current monitoring circuit;

[0035] The source of the second transistor 5 is grounded; the gate of the second transistor 5 is connected to the output end of the PWM generation module of the control module; the output end of the current sampling circuit is connected to the first input end of the current comparison module; the output end of the current monitoring circuit is connected to the second input end of the current comparison module; the third input end of the current comparison module is used to receive an enable signal; the current command is input into the PI controller after the difference is made between the output of the current sampling circuit, and the second output end of the current comparison module is connected to the enable input end of the PWM generation module.

[0036] The control module performs closed-loop control based on the difference between the current command signal and the actual feedback current signal. It outputs the modulated PWM (Pulse-Width Modulation) wave to the MOS tube drive circuit through the PI (Proportional Integral) controller, and finally realizes the PWM modulation control of the tube under the coil control circuit, thereby controlling the current size on the coil.

[0037] At the same time, the control module also outputs a control signal of the upper tube, which is amplified by the drive circuit and input to the upper tube of the clutch coil control circuit to prevent the clutch circuit from being grounded by mistake and ensure that the clutch is effectively shut down;

[0038] At the same time, the current comparison module determines whether to enable the output of the upper and lower tube control signals based on whether the current values ​​fed back by the monitoring circuit and the current sampling circuit are equal.

[0039] Enable signal E n Contains 0 and 1, corresponding to two working modes. n =1, and the current comparison module is equal to the current value fed back by the monitoring circuit and the current sampling circuit. At this time, the upper and lower tubes work normally, the upper tube is normally open, and the lower tube is controlled by PWM output; when E n =1 and the current comparison module receives different current values ​​from the monitoring circuit and the current sampling circuit, or E n =0, at this time the upper and lower tubes do not work, there is no PWM output, and the upper tube is shut down.

[0040] The voltage conversion circuit is a DC / DC module, which converts the 18V~32V variable DC voltage input into a 28V voltage as the voltage of the subsequent circuit; the coil control circuit includes an insulated gate field effect transistor 1, a sampling resistor 2, a clutch coil 3, a sampling resistor 4, an insulated gate field effect transistor 5 and a freewheeling diode 6. The insulated gate field effect transistors 1 and 5 are switch tubes. When they are connected at the same time, the clutch coil has current. When any one of them is disconnected, the clutch has no current. The two switch tubes are disconnected at the same time to prevent the clutch coil loop from being grounded by mistake and ensure that the clutch can be effectively turned off. Resistor 2 is a sampling resistor, and the clutch coil current is collected through the current sampling circuit for closed-loop control; resistor 4 is a monitoring resistor, and the clutch coil current is collected through the current monitoring circuit to enter the control module for monitoring. The current collection circuit and the current monitoring circuit include a differential collection circuit and a low-pass filter. The differential collection circuit collects the differential voltage at both ends of the sampling resistor, and the low-pass filter is used to filter out high-frequency interference signals. Diode 6 is a freewheeling diode, which can provide a freewheeling circuit for the clutch coil when the clutch circuit is turned off.

[0041] The core control function of the closed-loop control method is in the control module, which includes a PI controller for converting the current command I cmd The current is subtracted from the current collected, and the PI controller outputs the modulated PWM to achieve closed-loop control of the coil current. n The current comparison result controls the on or off of transistors 1 and 5, and the logic is the enable signal E n Or if any of the current comparison results is invalid, transistors 1 and 5 are turned off at the same time. The control module function can be implemented by processor software or programmable logic.

[0042] The implementation principle of the clutch current control method is: the control module receives the command value of the clutch current, and uses the current command value and the current actual value of the clutch current to implement closed-loop negative feedback control through the PI controller, and then outputs a PWM wave to accurately control the current of the circuit. This method can ensure that when the resistance and inductance values ​​of the clutch coil drift, the current on the clutch load is not affected.

[0043] In a preferred embodiment, Figure 1 4 is a structural block diagram of a clutch current control circuit according to an embodiment of the present invention.

[0044] like Figure 1 As shown, in the module connection diagram of the clutch current control circuit structure diagram of an embodiment of the present invention, all arrows represented by solid lines represent the flow direction of current and power, that is, electrical connection; all arrows represented by dotted lines represent the flow direction of signals, that is, signal connection.

[0045] like Figure 1As shown, the variable DC 18V~32V voltage input supplied from the outside enters the coil control circuit after passing through the voltage conversion circuit. The voltage conversion circuit can convert the DC 18V~32V voltage into a stable 28V DC voltage. The current output by the coil control circuit passes through the current sampling circuit and the current monitoring circuit to collect the coil current respectively. The current value obtained by the current collection circuit enters the control module, and the control module integrates the enabling control signal E n and current command I cmd Output the upper MOS tube control signal and the lower MOS tube PWM signal. These control signals pass through the MOS tube drive circuit and finally drive the MOS tube in the coil control circuit to work. The coil current collected by the current monitoring circuit is used for real-time current monitoring.

[0046] Compared with the current clutch control circuit, the present invention has the following innovative features:

[0047] 1. The clutch coil current is closed-loop controlled, the current remains unchanged and is not affected by the change of the clutch coil resistance and inductance;

[0048] 2. The clutch current closed-loop feedback and current monitoring are designed separately to avoid the problem of being unable to effectively identify the failure mode such as parameter offset in the closed-loop control circuit, thus improving the integrity of monitoring;

[0049] 3. The upper and lower MOS tubes of the clutch coil are disconnected at the same time, which can ensure the reliability of the current loop shutdown and the reliability of the clutch disconnection;

[0050] 4. Adapt to GJB181B and meet the DC voltage input in a wide range of 18V to 32V;

[0051] 5. The PWM modulation control circuit is simple in design, small in size, light in weight and low in power consumption.

[0052] The control module will be based on the reference current I cmd The feedback current sampled by the current sampling circuit is processed and calculated to generate a PWM signal, which is then amplified by the drive circuit and enters the coil control circuit. The PWM signal input end of the drive circuit is connected to the signal output end of the processor circuit, and the signal input end of the coil control circuit is connected to the output end of the drive circuit.

[0053] At the same time, the control module is based on the enable signal E n The value of is used to determine whether the upper tube control signal is enabled to output and whether the lower tube outputs a PWM signal. n =1, it means the upper tube control signal is enabled, the upper tube works normally and the lower tube has PWM output; when E n=0, it means that the upper tube control signal is not enabled, the upper tube does not work, and the lower tube has no PWM output. The upper tube control signal input end of the drive circuit is connected to the output end of the processor circuit, and the signal input end of the coil control circuit is connected to the output end of the drive circuit.

[0054] In order to further explain the working principle of the present invention in detail, Figure 2 Provide explanation.

[0055] like Figure 2 As shown, the voltage conversion circuit uses a DC / DC module to convert the 18V~32V variable DC voltage input into a stable 28V DC voltage to supply the clutch coil. The positive end of the DC voltage input 18V~32V is connected to the voltage input end of the DC / DC module, the negative end is grounded, and the voltage output end of the DC / DC module is connected to the coil control circuit.

[0056] The coil control circuit is composed of a clutch coil 3, a high-end sampling resistor 2, a low-end sampling resistor 4, a high-end switch MOS tube 1 and a low-end switch MOS tube 5, and a freewheeling diode 6; the high-end sampling resistor 2 collects the current of the clutch coil control loop for closed-loop control; the low-end resistor 4 collects the clutch coil current for current monitoring; when the clutch coil needs to be turned off, the high-end switch MOS tube 1 and the low-end switch MOS tube 5 are turned off at the same time, which can ensure that the clutch control loop is reliably turned off.

[0057] The high end of the clutch coil 3 is connected to the high end sampling resistor 2 and the high end switch MOS tube 1 in sequence, and the low end of the clutch coil 3 is connected to the low end sampling resistor 4 and the low end switch MOS tube 5 in sequence to form a current loop. The freewheeling diode 6 is connected in parallel with the clutch coil to form a freewheeling loop.

[0058] The current sampling circuit includes a sampling resistor 2, a differential acquisition circuit and a low-pass filter; the current monitoring circuit includes a monitoring resistor 4, a differential acquisition circuit and a low-pass filter. Both the current sampling circuit and the monitoring circuit collect voltage signals through sampling resistor voltage division, and transmit them to the control module after filtering and amplification by an active first-order low-pass filter.

[0059] Although the embodiments of the present invention have been shown and described above, it will be appreciated that the above embodiments are exemplary and are not to be construed as limitations on the present invention, and that those skilled in the art may change, modify, substitute and vary the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. An electromagnetic clutch current closed-loop control circuit, characterized in that: include: A voltage conversion circuit, a current sampling circuit, a current monitoring circuit, a coil control circuit, and a control module, wherein the control module includes a current comparison module, a PI controller, and a PWM generation module; the current sampling circuit and the current monitoring circuit each include a differential acquisition circuit and a low-pass filter in sequence; the input end of the voltage conversion circuit receives a variable DC voltage; The coil control circuit comprises a first transistor (1), a sampling resistor (2), a clutch coil (3), a monitoring resistor (4), a second transistor (5), and a freewheeling diode (6), wherein the gate of the first transistor (1) is connected to the first output terminal of the current comparison of the control module; the output terminal of the voltage conversion circuit is connected to the drain of the first transistor (1); one end of the sampling resistor (2) is connected to the source of the first transistor (1) and the positive differential input terminal of the current sampling circuit, and the other end of the sampling resistor (2) is connected to one end of the clutch coil (3), the negative electrode of the freewheeling diode (6), and the negative differential input terminal of the current sampling circuit; one end of the monitoring resistor (4) is connected to the other end of the clutch coil (3), the positive electrode of the freewheeling diode (6), and the positive differential input terminal of the current monitoring circuit, and the other end of the monitoring resistor (4) is connected to the drain of the second transistor (5) and the negative differential input terminal of the current monitoring circuit; The source of the second transistor (5) is grounded; the gate of the second transistor (5) is connected to the output end of the PWM generation module of the control module; the output end of the current sampling circuit is connected to the first input end of the current comparison module; the output end of the current monitoring circuit is connected to the second input end of the current comparison module; the third input end of the current comparison module is used to receive an enable signal; the current instruction is input into the PI controller after the difference is made between the output of the current sampling circuit, and the second output end of the current comparison module is connected to the enable input end of the PWM generation module.

2. The circuit according to claim 1, characterized in that The voltage conversion circuit specifically uses a DC / DC module to convert the 18V to 32V variable DC voltage input into a stable 28V DC voltage to supply the clutch coil.

3. The circuit according to claim 1, characterized in that The first transistor (1) and the second transistor (5) are insulated gate field effect transistors.

4. The circuit according to claim 1, characterized in that The low-pass filter is an active first-order low-pass filter.

5. The circuit according to claim 1, characterized in that The period of the PWM wave generated by the PWM generation module is parameterized according to the resistance and inductance values ​​of the clutch coil (3).

6. The circuit according to claim 1, characterized in that The differential acquisition circuit in the current sampling circuit is implemented using an operational amplifier with a common mode rejection ratio greater than 50V.

7. The circuit according to claim 1, characterized in that The current carrying capacity of the freewheeling diode (6), the first transistor (1) and the second transistor (5) is greater than 1.5 times the maximum current of the clutch coil (3).

8. A current closed-loop control method for an electromagnetic clutch, characterized in that: The method is performed by means of an electromagnetic clutch current closed-loop control circuit according to any one of claims 1 to 7, and the method comprises: Step 1: The current command signal and the current signal output by the current sampling circuit are differentially controlled to perform closed-loop control, and a modulated PWM wave is output through a PI controller to drive the second transistor (5); Step 2: The current comparison module determines whether to enable the output of the upper and lower tube control signals based on whether the current values ​​fed back by the monitoring circuit and the current sampling circuit are equal; The enable signal E of the current comparison module n Contains 0 and 1, corresponding to two working modes. n =1 and the current comparison module outputs an upper tube normally-on enable signal according to the current values ​​fed back by the monitoring circuit and the current sampling circuit being equal, and controls the first transistor (1) to be normally-on; and simultaneously enables the PWM output to control the second transistor (5) to be turned on; Dangdang E n =1 and the current comparison module receives different current values ​​from the monitoring circuit and the current sampling circuit, or E n =0, at this time, the current comparison module outputs the upper tube shut-down enable signal to control the first transistor (1) to shut down, and at the same time enables PWM not to output to control the second transistor (5) to turn off.

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