Servo system for ship towing winch and control method thereof

Abstract

The invention discloses a servo system for a ship towing winch and a control method of the servo system. The servo system comprises a rectifying circuit, a three-phase full-bridge circuit, a braking circuit, a DSP control circuit, an output capacitor C, a brake control circuit and a rotary transformer decoding circuit. According to the servo driver, full electrification of releasing, recycling and zero-speed working condition maintaining of the ship winch is achieved, compared with a hydraulic driving device of a traditional winch, the defects that a hydraulic system is complex in structure, large in size and difficult to maintain are overcome, and an electric driving system is high in control precision, simpler to achieve and more convenient to operate. Compared with conventional alternating-current variable-frequency electric drive of an existing winch, servo drive is more suitable for the low-speed large-torque working condition, efficiency is higher, and cooperation of a PLC is not needed. Compared with a traditional speed loop and current loop control method, the control method for four-quadrant operation of the servo driver enables the winch to have an energy consumption braking function, and meanwhile the safety of the towing winch under the extreme working condition is guaranteed by being matched with a brake of the motor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of servo control, in particular to a servo system for a ship towing winch and a control method thereof. BACKGROUND

[0002] The servo drive system for the ship towing winch is mainly used for driving the winch to release, recover and hold equipment or heavy objects. In the release working condition, the permanent magnet synchronous motor is in the state of being dragged to generate electricity, and is used as a generator. At this time, the motor is used as a load, and the energy flows from the permanent magnet synchronous motor to the servo driver, and is finally consumed through the braking resistor. In the recovery working condition, the motor is used as an electric motor, and the energy flows from the power supply to the heavy object. In the holding working condition, the motor is mainly held by the brake. The motor speed in the three working conditions is controlled by the driver.

[0003] At present, the winch mainly has the characteristics of low speed and large torque in the field of ship application. Due to its large output, the weight of the driving equipment reaches several tons or even dozens of tons. However, with the space demand of national defense equipment, the lightweight, environmental adaptability and intelligence of the winch will be the future development trend, and the driving mode will also develop from hydraulic drive to electric drive along with the development of motor drive technology. At present, the main driving modes of the winch include hydraulic drive and electric drive, and the main characteristics are as follows: 1) The hydraulic drive mainly drives the winch through the hydraulic motor. Generally, the corresponding oil source and hydraulic pump need to be configured, which leads to a large size and heavy weight of the hydraulic drive device. Compared with the electric drive, the weight is nearly 10 times heavier, and the maintenance cost is higher, which has the risk of oil leakage. 2) For the electric drive, the main implementation mode is frequency converter + high-voltage asynchronous motor. Compared with the hydraulic drive, the implementation is simple, the response speed is faster, and the weight can be greatly reduced. However, for high-precision cable length control and high-speed dynamic response, the frequency converter still cannot meet the requirements. SUMMARY

[0004] To solve the above technical problems, the present application provides a servo system for a ship towing winch and a control method thereof.

[0005] The present application is realized by the following technical solutions.

[0006] The servo drive system for the ship towing winch provided by the present application comprises a permanent magnet synchronous motor, a rectifier circuit, a three-phase full-bridge circuit, a braking circuit, a DSP control circuit, a bus capacitor C, a braking resistor box, a brake control circuit and a surge suppression circuit. The rectifier circuit is formed by 6 rectifier diodes D1-D6 to form a rectifier bridge, wherein the cathodes of diodes D1, D3 and D5 are commonly connected to the positive pole of the bus capacitor C, the anode of D1 is connected to the L1 terminal of the three-phase power supply, the anode of D3 is connected to the L2 terminal of the three-phase power supply, and the anode of D5 is connected to the L3 terminal of the three-phase power supply; the cathode of D2 is connected to the anode of D1, the cathode of D4 is connected to the anode of D3, the cathode of D6 is connected to the anode of D5, and the anodes of D2, D4 and D6 are commonly connected to the negative pole of the bus capacitor C; the rectifier bridge is connected to the power supply at one end and connected to the surge suppression circuit at the other end through the above connection relationship of D1-D6; The surge suppression circuit includes an IGBT device Q7 and a power resistor R1, the collector of Q7 is connected to the cathodes of D1, D3 and D5 in the rectifier bridge (i.e. the positive pole of the rectifier bridge output), and the collector of Q7 is also connected to one end of the power resistor R1; the emitter of Q7 is connected to the positive pole of the bus capacitor C, and the emitter of Q7 is also connected to the other end of the power resistor R1; The three-phase full-bridge circuit is composed of IGBT devices Q1-Q6, the collectors of Q1, Q3 and Q5 are commonly connected to the positive pole of the bus capacitor C; the emitter of Q1 is connected to the A-phase winding of the permanent magnet synchronous motor, and the emitter of Q1 is also connected to the collector of Q2; the emitter of Q3 is connected to the B-phase winding of the permanent magnet synchronous motor, and the emitter of Q3 is also connected to the collector of Q4; the emitter of Q5 is connected to the C-phase winding of the permanent magnet synchronous motor, and the emitter of Q5 is also connected to the collector of Q6; the emitters of Q2, Q4 and Q6 are commonly connected to the negative pole of the bus capacitor C; the three-phase full-bridge circuit is electrically connected to the three-phase windings of the permanent magnet synchronous motor at one end and electrically connected to the bus capacitor C at the other end through the above connection relationship of Q1-Q6; The braking circuit includes an IGBT device Q8 and a freewheeling diode D7, the collector of Q8 is connected to the positive pole of the bus capacitor C, the emitter of Q8 is connected to the cathode of the freewheeling diode D7, and the emitter of Q8 is also connected to one end of the braking resistor box; the anode of the freewheeling diode D7 is connected to the negative pole of the bus capacitor C, and the anode of D7 is also connected to the other end of the braking resistor box; the braking circuit is electrically connected to the bus capacitor C at one end and electrically connected to the braking resistor box at the other end through the above connection relationship of Q8 and D7; The input end of the brake control circuit is connected to the G ZDQThe signal output end is electrically connected, the output end of the brake control circuit is electrically connected with the built-in brake of the permanent magnet synchronous motor; the permanent magnet synchronous motor is built-in with a rotary transformer RT, the signal output end of the rotary transformer RT is connected with the signal input end of a resolver decoding chip, the signal output end of the resolver decoding chip is communicatively coupled with the signal input end of the DSP control circuit, so as to transmit the motor armature group position signal θ and the rotating speed signal n to the DSP control circuit; the DSP control circuit further accesses the DC bus voltage V dc and the currents Ia~Ic of the three-phase windings of the permanent magnet synchronous motor; the PWM1~PWM6 signal output ends of the DSP control circuit are respectively electrically connected with the gates of Q1~Q6 in the three-phase full-bridge circuit, the PWM zd signal output end of the DSP control circuit is electrically connected with the gate of Q8 in the brake circuit; the permanent magnet synchronous motor is mechanically connected with the ship towing winch.

[0007] Further, the DSP control circuit adopts a four-quadrant operation control method, through controlling the conduction and turn-off of Q1~Q6 in the three-phase full-bridge circuit and the conduction and turn-off of Q8 in the brake circuit, combining with the speed loop and current loop calculation, the control of the release, recovery and 0-speed maintaining working conditions of the winch is realized.

[0008] A control method of a servo drive system for a ship towing winch, comprising the following steps: A, a speed control step in the winch recovery working condition; B, a speed control step in the winch release working condition; C, a control step in the 0-speed maintaining working condition of the winch.

[0009] Further, the recovery working condition speed control step of the step A is: A1, through the rectification of D1~D6 in the rectifier circuit, the three-phase power supply is rectified to a DC voltage; A2, detecting the DC bus voltage V dc , when V dc is greater than the bus under-voltage threshold, opening the IGBT device Q7 of the surge suppression circuit and closing the surge suppression function; A3, enabling the FOC control, controlling the motor to 0-speed maintaining by setting the speed loop reference rotating speed to 0, and releasing the brake of the permanent magnet synchronous motor through the brake control circuit; A4, controlling the motor to rated speed maintaining operation by setting the speed loop reference rotating speed to the rated rotating speed of the recovery working condition; A5, detecting the motor turns through the motor armature group position signal θ, and controlling the motor to 0-speed maintaining by setting the speed loop reference rotating speed to 0 when the motor turns meet the cable length control requirement; A6, close the brake of the permanent magnet synchronous motor through the brake control circuit, and close the FOC control.

[0010] Further, the implementation steps of the FOC control in step A3 are: A31, decode the signal output by the resolver RT through the resolver decoding circuit to obtain the motor speed n and the armature group position signal θ; A32, detect the motor three-phase winding current i a , i b , i c , convert to dq-axis current i d , i q after Clarke transformation and Park transformation; A33, perform speed loop and current loop calculation, and convert the dq-axis voltage to αβ-axis voltage u α , u β through inverse Park transformation; A34, obtain the duty cycle of the EPWM of the DSP through the SVPWM module; A35, generate PWM1~PWM6 driving signals through the EPWM module of the DSP, and output them to the gate electrodes of Q1~Q6 in the three-phase full-bridge circuit; A36, output the phase voltage signal from the three-phase full-bridge circuit to the permanent magnet synchronous motor.

[0011] Further, the speed control steps of the release working condition in step B are: B1, enable the FOC control, control the motor to 0 speed by setting the speed loop reference speed to 0, release the brake of the permanent magnet synchronous motor through the brake control circuit, and perform energy consumption braking through the brake circuit; B2, control the motor to operate at rated speed by setting the speed loop reference speed to the release working condition rated speed, and continuously perform energy consumption braking through the brake circuit; B3, detect the motor turns (through zero point detection) through the motor armature group position signal θ, and control the motor to 0 speed by setting the speed loop reference speed to 0 when the motor turns meet the cable length control requirement, and continuously perform energy consumption braking through the brake circuit; B4, close the brake of the permanent magnet synchronous motor through the brake control circuit, and close the FOC control.

[0012] Further, the energy consumption braking steps in steps B1~B3 are: B11, detect the DC bus voltage Vdc under the release working condition; B12, when V dc is greater than the brake voltage threshold V dcthWhen the DC bus voltage is greater than the normal voltage threshold V B13、when V dc is less than the normal voltage threshold V dcth2 , the brake resistor box is turned off, and the freewheeling diode D7 is used for freewheeling.

[0013] Further, in steps B12 and B13, the DSP control circuit controls the IGBT device Q8 of the brake circuit through the output PWM zd signal to realize the connection and disconnection of the brake resistor box.

[0014] Further, the 0-speed maintaining control step of step C includes the following two steps: C1, when the motor is in the 0-speed maintaining working condition or is powered off, the brake of the permanent magnet synchronous motor is closed by the brake control circuit to realize the 0-speed maintaining of the motor; C2, when the motor is in the release working condition and the recovery working condition, the 0-speed maintaining is realized by the FOC control, and the motor is maintained at 0-speed by the three-phase full-bridge circuit.

[0015] Further, the motor turns in step A5 are detected by the zero point detection.

[0016] The beneficial effects of the present application are as follows: 1. Compared with the hydraulic drive mode, the servo driver + permanent magnet synchronous motor + brake resistor box implementation mode is simpler, and the weight requirement is only hundreds of kilograms, without oil source, which is more convenient to maintain; 2. Compared with the frequency converter + asynchronous motor, the servo driver + permanent magnet synchronous motor + brake resistor box implementation mode has high control precision, faster response and higher system efficiency of 90%. 3. The four-quadrant control operation mode ensures good speed control performance of the winch in each working state, and ensures better stability of the winch when the load suddenly changes. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the structure block diagram of the servo drive system of the ship towing winch of the present application; Figure 2 is the main circuit principle diagram of the recovery working condition of the present application; Figure 3 is the main circuit principle diagram of the release working condition of the present application. DETAILED DESCRIPTION

[0018] The technical solutions of the present application are further described below, but the scope of protection is not limited to the description.

[0019] Permanent magnet synchronous motor adopts 8-pole 48-slot pole-slot matching, and the cogging torque is small. Due to low speed and large torque, the rotor is realized by large outer diameter. The normal retraction and release speed of the servo system is 160-2100 r / min, the torque is 93 N·m, and the release and recovery capacity is 22 kW. At the same time, it has the ability to perform 136 N·m large torque retraction and release adjustment within the speed range of 160-630 r / min. The input power is three-phase 380VAC (50Hz), and within the range of 380VAC±10%, it needs to ensure normal retraction and release and low-speed large torque retraction and release. The brake resistor box needs to meet the ability of 93 N·m long-time winch release braking at 2100 r / min speed. The motor efficiency is 0.7 in the generating state, and the driver efficiency is 0.9, so the brake box needs to ensure 14 kW of braking power for a long time. The application background is a ship towing winch retraction and release device.

[0020] Figure 1 The structure block diagram of the proposed servo drive system for ship towing winch is shown, which includes three-phase full-bridge circuit, surge suppression circuit, brake circuit, rectifier bridge, bus capacitor C, resolver decoding circuit, brake controller circuit, DSP control circuit, brake resistor box, permanent magnet synchronous motor, brake, resolver transformer RT; the DSP control circuit is connected with the resolver transformer RT through the resolver decoding chip and accesses the motor armature group position signal θ and the speed signal n, accesses the DC bus voltage V dc , and accesses the phase current I a~c ; the DSP control circuit outputs the brake controller signal G ZDQ to the brake controller circuit, and the DSP control circuit also outputs the PWM 1~6 signal to the three-phase full-bridge circuit, and the DSP control circuit also outputs the PWM zd signal to the brake circuit, the rectifier bridge is connected with the three-phase AC 380V power supply, the other end is connected with the surge suppression circuit, the three-phase full-bridge circuit is connected with the three-phase winding of the motor, the other end is connected with the bus capacitor, the brake circuit is connected with the bus capacitor, the other end is connected with the brake resistor box, the brake controller circuit is connected with the permanent magnet synchronous motor brake, and the permanent magnet synchronous motor is mechanically connected with the towing winch.

[0021] Figure 2 With Figure 3The proposed circuit diagrams for both recovery and release modes show that the three-phase full-bridge circuit consists of IGBT devices Q1~Q6. The collectors C of Q1, Q3, and Q5 are connected to the positive terminal of the bus capacitor. The emitter E of Q1 is connected to the A-phase winding and to the collector C of Q2. The emitter E of Q3 is connected to the B-phase winding and to the collector C of Q4. The emitter E of Q5 is connected to the C-phase winding and to the collector C of Q6. The emitters E of Q2, Q4, and Q6 are connected to the negative terminal of the bus capacitor. For the circuit diagram for recovery mode, the surge suppression circuit consists of IGBT device Q7 and power resistor R1. The collector C of Q7 is connected to the positive output of the rectifier bridge and to one side of resistor R1. The emitter E of Q7... The collector E is connected to the positive terminal of the bus capacitor and to the other side of the resistor R1. The rectifier bridge consists of power diodes D1 to D6. The cathodes of D1, D3, and D5 are connected to the positive terminal of the capacitor. The anodes of D1, D3, and D5 are connected to the three-phase inputs L1, L2, and L3 respectively, and are connected to the cathodes of D2, D4, and D6. The anodes of D2, D4, and D6 are connected to the negative terminal of the capacitor. For the circuit structure diagram of the release condition, the braking circuit consists of IGBT device Q8 and freewheeling diode D7. The collector C of Q8 is connected to the positive terminal of the bus capacitor. The emitter E of Q8 is connected to the cathode of the freewheeling diode and to the input side of the braking resistor box. The cathode of the freewheeling diode is connected to the negative terminal of the bus capacitor and to the other input side of the braking resistor box.

[0022] The control method for the servo drive system used in ship towing winches mainly includes the following control steps: A. Speed ​​control procedures under winch recovery conditions; B. Speed ​​control procedures under winch release conditions; C. Control steps under winch 0-speed holding condition.

[0023] Combination Figure 2 The main circuit schematic for the recovery operation mode, and the speed control in control step A during the recovery operation mode include the following steps: A1. The three-phase AC power input to L1, L2, and L3 is rectified to DC voltage through the D1~D6 rectifier circuit, and the bus capacitor C is charged through R1. A2, Detecting V dc When the voltage exceeds the bus undervoltage threshold, surge circuit Q7 is activated and surge suppression function is disabled. A3. Speed ​​loop enable: By setting the speed loop reference speed to 0, the motor is controlled to maintain 0 speed, and the motor brake is released through the brake control circuit. A4. By giving a reference speed to the rated speed under recycling conditions, the motor is controlled to maintain operation at the rated speed. A5, detect the motor coil number through the motor angle θ, and control the motor to 0 speed by setting the speed loop reference speed to 0 when the motor coil number reaches the cable length control requirement; A6, close the motor brake through the brake control circuit, and close the loop enable.

[0024] In combination Figure 3 The principle diagram of the main circuit in the release working condition, and the speed control in the release working condition in step B includes the following steps: B1, enable the speed loop, control the motor to 0 speed by setting the speed loop reference speed to 0, and open the motor brake through the brake control circuit, and the brake circuit performs energy consumption braking; B2, control the motor to rated speed by setting the reference speed to the rated speed of the release working condition, and the brake circuit performs energy consumption braking; B3, detect the motor coil number through the motor angle θ, and control the motor to 0 speed by setting the speed loop reference speed to 0 when the motor coil number reaches the cable length control requirement, and the brake circuit performs energy consumption braking; B4, close the motor brake through the brake control circuit, and close the loop enable.

[0025] Through the combination of the vector control mode and the energy consumption braking mode, bidirectional flow of energy is realized, the servo system has high speed stability in both recovery and release, the system has fast response when the load suddenly changes, the motor coil number and the cable length are accurately controlled, and the system stability of the winding and unwinding device is improved.

[0026] The energy consumption braking steps in B1-B3 in step B are as follows: B11, in the release working condition, detect the bus voltage V dc ; B12, when V dc is greater than the braking voltage threshold V dcth , the bus voltage generates electricity through the braking resistor box connected through the brake circuit Q8 and D7; B13, when V dc is less than the normal voltage threshold V dcth2 , the bus voltage is connected through the braking resistor box by opening Q8, and the freewheeling diode D7 performs freewheeling; The implementation steps of the vector control in A3-A5 in step A are as follows: A31, obtain the motor speed n and θ through the resolver decoding circuit; A32, detect the motor three-phase winding currents i a , i b , i c , and i d , iq ; A33, speed loop and current loop calculation, current loop sets i d Reference 0, convert dq axis voltage to u by inverse Park transformation α , u β ; A34, get the duty cycle of the EPWM of the DSP through the SVPWM module; A35, generate the driving signal PWM1~6 of the three-phase full-bridge Q1~Q6 through the EPWM module of the DSP; A36, the IGBT full-bridge outputs the phase voltage signal to the PMSM; The control step B is the control step of the winch 0-speed maintaining working condition, which mainly includes two cases: C1, when the motor is in the 0-speed maintaining working condition or power-off for a long time, the 0-speed maintaining is performed by the motor brake, and the brake control circuit controls the motor to maintain 0 speed; C2, when the motor is in the release working condition and the recovery working condition, the 0-speed maintaining is realized by the vector control, and the three-phase full-bridge circuit controls the motor to maintain 0 speed.

[0027] The application combines the brake maintaining and the vector control 0-speed maintaining, combines the advantages of long-time maintaining energy saving and the advantages of short-time maintaining flexibility, and the brake maintaining has higher safety in the long-time maintaining state.

Claims

1. A servo drive system for a ship towing winch, characterized in that: Includes permanent magnet synchronous motor, rectifier circuit, three-phase full-bridge circuit, braking circuit, DSP control circuit, bus capacitor C, braking resistor box, brake control circuit, and surge suppression circuit; The rectifier circuit consists of a rectifier bridge formed by six rectifier diodes D1 to D6. The cathodes of diodes D1, D3, and D5 are connected to the positive terminal of the bus capacitor C. The anode of D1 is connected to terminal L1 of the three-phase power supply, the anode of D3 is connected to terminal L2 of the three-phase power supply, and the anode of D5 is connected to terminal L3 of the three-phase power supply. The cathode of diode D2 is connected to the anode of D1, the cathode of D4 is connected to the anode of D3, and the cathode of D6 is connected to the anode of D5. The anodes of D2, D4, and D6 are connected to the negative terminal of the bus capacitor C. Through the above connection relationship of D1 to D6, one end of the rectifier bridge is connected to the power supply, and the other end is connected to the surge suppression circuit. The surge suppression circuit includes an IGBT device Q7 and a power resistor R1. The collector of Q7 is connected to the cathodes of D1, D3, and D5 in the rectifier bridge (i.e., the positive output of the rectifier bridge), and the collector of Q7 is also connected to one end of the power resistor R1. The emitter of Q7 is connected to the positive terminal of the bus capacitor C, and the emitter of Q7 is also connected to the other end of the power resistor R1. The three-phase full-bridge circuit is composed of IGBT devices Q1 to Q6. The collectors of Q1, Q3, and Q5 are all connected to the positive terminal of the bus capacitor C. The emitter of Q1 is connected to the A-phase winding of the permanent magnet synchronous motor, and the emitter of Q1 is also connected to the collector of Q2. The emitter of Q3 is connected to the B-phase winding of the permanent magnet synchronous motor, and the emitter of Q3 is also connected to the collector of Q4. The emitter of Q5 is connected to the C-phase winding of the permanent magnet synchronous motor, and the emitter of Q5 is also connected to the collector of Q6. The emitters of Q2, Q4, and Q6 are all connected to the negative terminal of the bus capacitor C. Through the above connection relationship of Q1 to Q6, one end of the three-phase full-bridge circuit is electrically connected to the three-phase winding of the permanent magnet synchronous motor, and the other end is electrically connected to the bus capacitor C. The braking circuit includes an IGBT device Q8 and a freewheeling diode D7. The collector of Q8 is connected to the positive terminal of the bus capacitor C, and the emitter of Q8 is connected to the cathode of the freewheeling diode D7. The emitter of Q8 is also connected to one end of the braking resistor box. The anode of the freewheeling diode D7 is connected to the negative terminal of the bus capacitor C, and the anode of D7 is also connected to the other end of the braking resistor box. Through the above connection relationship between Q8 and D7, one end of the braking circuit is electrically connected to the bus capacitor C, and the other end is electrically connected to the braking resistor box. The input terminal of the brake control circuit is connected to the G of the DSP control circuit. ZDQ The signal output terminal is electrically connected, and the output terminal of the brake control circuit is electrically connected to the brake built into the permanent magnet synchronous motor. The permanent magnet synchronous motor has a built-in resolver RT, the signal output terminal of which is connected to the signal input terminal of the resolver decoding chip. The signal output terminal of the resolver decoding chip is communicatively coupled to the signal input terminal of the DSP control circuit to transmit the motor armature group position signal θ and speed signal n to the DSP control circuit. The DSP control circuit is also connected to the DC bus voltage V. dc The currents Ia~Ic of the three-phase windings of the permanent magnet synchronous motor; the PWM1~PWM6 signal output terminals of the DSP control circuit are respectively electrically connected to the gates of Q1~Q6 in the three-phase full-bridge circuit, and the PWM of the DSP control circuit... zd The signal output terminal is electrically connected to the gate of Q8 in the braking circuit; the permanent magnet synchronous motor is mechanically connected to the ship's towing winch.

2. The servo drive system for a ship towing winch as described in claim 1, characterized in that: The DSP control circuit adopts a four-quadrant operation control method. By controlling the on and off of Q1~Q6 in the three-phase full-bridge circuit and the on and off of Q8 in the braking circuit, combined with speed loop and current loop calculations, the control of winch release, recovery and zero-speed holding conditions is realized.

3. The control method for the servo drive system of a ship towing winch as described in any one of claims 1-2, characterized in that: The control steps of the DSP control circuit for winch operation include: A. Speed ​​control procedures under winch recovery conditions; B. Speed ​​control procedures under winch release conditions; C. Control steps under winch 0-speed holding condition.

4. The control method for the servo drive system of a ship towing winch as described in claim 3, characterized in that, The recovery speed control steps in step A are as follows: A1. The three-phase power supply is rectified to DC voltage through the rectification effect of D1~D6 in the rectifier circuit; A2. Detect the DC bus voltage Vdc. When Vdc is greater than the bus undervoltage threshold, turn on the IGBT device Q7 of the surge suppression circuit and turn off the surge suppression function. A3. Enable FOC control, control the motor to maintain 0 speed by setting the reference speed of the speed loop to 0, and release the brake of the permanent magnet synchronous motor through the brake control circuit. A4. By giving the reference speed of the speed loop to the rated speed of the recovery condition, control the motor to the rated speed and maintain operation; A5. Detect the number of motor revolutions by the position signal θ of the motor armature group. Once the number of motor revolutions reaches the cable length control requirement, control the motor to 0 speed and maintain it by setting the reference speed of the given speed loop to 0. A6. Close the brake of the permanent magnet synchronous motor through the brake control circuit and turn off the FOC control enable.

5. The control method for the servo drive system of a ship towing winch as described in claim 4, characterized in that: The implementation steps of FOC control in step A3 are as follows: A31. The signal output by the resolver RT is decoded by the resolver decoding circuit to obtain the motor speed n and the armature group position signal θ. A32. By detecting the three-phase winding current i of the motor a i b i c After Clarke and Park transformations, it is converted into dq-axis current i. d i q ; A33. Perform velocity loop and current loop calculations, and convert the dq-axis voltage to the αβ-axis voltage u using the inverse Park transformation. α u β ; A34. Obtain the duty cycle of the DSP's EPWM through the SVPWM module; A35. The DSP's EPWM module generates PWM1~PWM6 drive signals, which are then output to the gates of Q1~Q6 in the three-phase full-bridge circuit, respectively. A36. The three-phase full-bridge circuit outputs phase voltage signals to the permanent magnet synchronous motor.

6. The control method for the servo drive system of a ship towing winch as described in claim 3, characterized in that: The release speed control steps in step B are as follows: B1. Enable FOC control, control the motor to maintain 0 speed by setting the reference speed of the speed loop to 0, and release the brake of the permanent magnet synchronous motor through the brake control circuit, so that the braking circuit performs energy-consuming braking. B2. By giving the reference speed of the speed loop to the rated speed of the release condition, the motor is controlled to the rated speed and kept running, and the braking circuit continuously performs energy-consuming braking; B3. The number of motor revolutions is detected by the position signal θ of the motor armature group (by zero-point detection). Once the number of motor revolutions reaches the cable length control requirement, the motor is controlled to maintain 0 speed by setting the reference speed of the speed loop to 0. The braking circuit continues to perform energy-consuming braking. B4. Close the brake of the permanent magnet synchronous motor through the brake control circuit and turn off the FOC control.

7. The control method for the servo drive system of a ship towing winch as described in claim 6, characterized in that: The energy-saving braking steps in steps B1 to B3 are as follows: B11. Under the release condition, detect the DC bus voltage Vdc; B12, when V dc Greater than the braking voltage threshold V dcth At that time, the DC bus voltage is consumed by the braking resistor box connected to the braking circuit. B13, when V dc Less than the normal voltage threshold V dcth2 At this time, the braking resistor box is disconnected, and freewheeling current is simultaneously supplied through the freewheeling diode D7.

8. The control method for the servo drive system of a ship towing winch as described in claim 7, characterized in that: In steps B12 and B13, the DSP control circuit outputs PWM. zd The IGBT device Q8 in the signal-controlled braking circuit enables the braking resistor box to be switched on and off.

9. The control method for the servo drive system of a ship towing winch as described in claim 3, characterized in that: The zero-speed holding control step in step C includes the following two types: C1. When the motor is in a 0-speed holding condition for a long time or when the power is off, the brake control circuit controls the brake of the permanent magnet synchronous motor to close, so as to achieve 0-speed holding of the motor. C2. When the motor is in the release or recovery mode, the 0-speed maintenance is achieved by FOC control, which controls the motor to maintain 0 speed through a three-phase full-bridge circuit.

10. The control method for the servo drive system of a ship towing winch as described in claim 4, characterized in that: In step A5, the number of motor revolutions measured by θ is detected using a zero-point detection method.

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