A control method and control system for a control angle motor

Abstract

A control method and control system of an angle control motor. The present application adopts a speed feedforward type three closed loop servo motor control method, wherein the control method and control cycle setting of the three closed loops can ensure the accuracy and stability of the angle control of the flow regulating servo unit, thereby ensuring the stability of the flow change; the closed loop control with speed feedforward can accelerate the response speed of the servo motor, and meet the real-time and high responsiveness of the system. In a further scheme, the segmented PID control method first ensures the no overshoot index requirement of the flow regulating system, and further accelerates the motor response speed on the basis of ensuring no overshoot.

Description

Technical Field

[0001] This invention relates to a control method for an internal servo motor in a rocket propulsion system, specifically to a control method and system for a servo motor in a liquid rocket engine flow regulation system. Background Technology

[0002] Existing servo-controlled angle drivers (i.e., servo motors connected to speed reducers) achieve this by controlling speed, which has problems such as poor dynamic response, overshoot, and large deviations in the steady-state range. Summary of the Invention

[0003] In view of the defects and shortcomings of the existing technology, the present invention provides a control method for a motor to control the angle.

[0004] Therefore, the control method provided by the present invention includes: the method is implemented using an angle PID control loop, a speed PID control loop, and a current PID control loop, and the method includes:

[0005] The angle of the motor reducer is collected in real time. The difference between the current angle of the reducer and the current set angle is used as the input of the angle PID control loop. The angle PID control loop uses the angle difference to calculate the speed. The angle PID control loop periodically outputs the speed calculation result.

[0006] The motor speed is collected in real time, and the difference between the current motor speed and the calculated current speed is used as the input of the speed PID control loop. The speed PID control loop uses the speed difference to calculate the current; the speed PID control loop periodically outputs the current calculation result.

[0007] The motor current is collected in real time, and the difference between the current motor current and the calculated current current is used as the input of the current PID control loop. The current PID control loop uses the current difference to calculate the duty cycle. The current PID control loop periodically outputs the duty cycle calculation result as the servo motor control signal.

[0008] The control algorithm for the current PID control loop is as follows:

[0009]

[0010] in:

[0011] k represents the kth output cycle of the current PID control loop at the current moment, and k is a natural number;

[0012] u(k) represents the output value of the kth output cycle of the current PID control loop;

[0013] e(k) is the current difference used to calculate u(k);

[0014] e(k-1) is the current difference used to calculate u(k-1), and e(k-1) is initially 0;

[0015] j = 0, 1, 2, ..., k;

[0016] q represents the q-th output cycle of the PID control loop at the current angle, where q is a natural number;

[0017] possv(q) represents the set angle used to calculate the output value in the qth output cycle of the angle PID control loop. Initially, possv(q-1) is 0.

[0018] K b Denotes the feedforward coefficient, 70≤K b ≤150;

[0019] K p This indicates the current proportional gain of the current PID control loop;

[0020] K i This represents the current integral coefficient of the current PID control loop;

[0021] K d This represents the current differential coefficient of the current PID control loop.

[0022] Optionally, the output period of the angle PID control loop is 5 to 10 ms; the output period of the speed PID control loop is 1 to 5 ms; and the output period of the current PID control loop is 0.05 to 0.1 ms.

[0023] Furthermore, the method of the present invention also includes:

[0024] The rotational speed is calculated after selecting the parameters of the angle PID control loop based on the magnitude of the current angle difference and the first threshold. The selection of the angle PID control loop parameters based on the magnitude of the current angle difference and the first threshold includes:

[0025] When the current angle difference is greater than or equal to the first threshold, the angle PID control loop K p When the value of K is greater than the current angle difference and less than the first threshold, the angle PID control loop K... p The value of ,

[0026] When the current angle difference is greater than or equal to the first threshold, the angle PID control loop K i When the value of K is less than the current angle difference and less than the first threshold, the angle PID control loop K... i The value of ,

[0027] Furthermore, the K of the angle PID control loop p The value range is [10, 50], and the angle PID control loop K iThe value range is [0,1], and the angle PID control loop K d The value range is [0, 0.1];

[0028] After selecting the parameters of the speed PID control loop based on the relationship between the current speed difference and the second threshold, the current is calculated. The selection of the speed PID control loop parameters based on the relationship between the current speed difference and the second threshold includes:

[0029] When the current speed difference is greater than or equal to the second threshold, the speed PID control loop K p When the value of K is greater than the current speed difference and less than the second threshold, the speed PID control loop K... p The value of ,

[0030] When the current speed difference is greater than or equal to the second threshold, the speed PID control loop K i When the value of K is greater than the current speed difference and less than the second threshold, the speed PID control loop K... i The value of ,

[0031] Furthermore, the K of the speed PID control loop p The value range is [0.5, 10], and the speed PID control loop K i The value range is [0,1], and the speed PID control loop K d The value range is [0, 0.1];

[0032] After selecting the parameters of the current PID control loop based on the relationship between the current current difference and the third threshold, the duty cycle is calculated. The selection of the parameters of the current PID control loop based on the relationship between the current current difference and the third threshold includes:

[0033] When the current difference is greater than or equal to the third threshold, the current PID control loop K p When the value of K is greater than the current current difference and less than the third threshold, the current PID control loop K... p The value of ;

[0034] When the current difference is greater than or equal to the third threshold, the current PID control loop K i When the value of K is less than the current current difference and less than the third threshold, the current PID control loop K... i The value of ,

[0035] Furthermore, the K of the current PID control loop p The value range is [0,1], and the current PID control loop K i The value range is [0,1], and the current PID control loop K d The value range is [0, 0.1].

[0036] Furthermore, the difference between the normalized values ​​of the current angle and the current set angle after normalization is taken as the current angle difference; the difference between the normalized values ​​of the calculated current speed and the collected current motor speed after normalization is taken as the current speed difference; the difference between the normalized values ​​of the calculated current current and the collected current motor current after normalization is taken as the current current difference.

[0037] The present invention also provides a control system for implementing the above-described method. The control system includes a data acquisition module, an angle PID control loop, a speed PID control loop, and a current PID control loop. The data acquisition module is used to acquire the reducer's angle, motor speed, and motor current, and input them to the angle PID control loop, speed PID control loop, and current PID control loop, respectively. Each of the angle PID control loop, speed PID control loop, and current PID control loop executes the above-described method.

[0038] Furthermore, the control system also includes a segmented PID control module for executing the method described in claim 3 and controlling the corresponding parameters of the angle PID control loop, the speed PID control loop, and the current PID control loop.

[0039] Compared with existing technologies, this invention employs a speed-feedforward three-closed-loop servo motor control method. The three-closed-loop control method and control cycle setting ensure the accuracy and stability of the angle control of the flow regulation servo unit, thereby guaranteeing stable flow changes. The closed-loop control with speed feedforward accelerates the servo motor's response speed, meeting the system's real-time and high-response requirements. In a further embodiment, the piecewise PID control method first ensures the flow regulation system's overshoot-free performance requirement, and then, while ensuring no overshoot, further accelerates the motor's response speed.

[0040] The method of this invention is particularly suitable for meeting the specific position control requirements of flow regulation systems in aerospace liquid rocket engines. Using the control method of this invention, rocket engines can meet the requirements of rapid response, no overshoot, and steady-state error of less than ±0.2 degrees for rocket propulsion systems. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the three control closed-loop relationships in the control method of the present invention;

[0042] Figure 2 This is a diagram illustrating the motor control effect of Example 1;

[0043] Figure 3 This is a diagram illustrating the motor control effect in Comparative Example 1.

[0044] Figure 4 This is a diagram illustrating the motor control effect in Comparative Example 2;

[0045] Figure 5 This is a diagram illustrating the motor control effect of Example 2;

[0046] Figure 6 This is an example of the structure of a flow regulation servo control system for an existing liquid rocket propulsion system. Detailed Implementation

[0047] Unless otherwise specified, the terminology used in this document is based on the understanding of those skilled in the art.

[0048] This invention employs a speed-feedforward three-loop control technology, specifically using a control algorithm with speed feedforward to accelerate the motor control response speed. Furthermore, the outputs of the three closed loops are periodic, meeting the motor's rapid response requirements and effectively controlling the stable operation of the servo unit. The three-loop control includes a PID control loop for the unit angle, a PID control loop for the motor speed, and a PID control loop for the motor current. The relationship between the three closed loops is shown below. Figure 1 As shown, the servo unit's angle (also referred to as position in this article) is set by the user, while the feedback angle comes from the servo unit's position sensor (such as a rotary transformer). The output value is calculated using a PID algorithm and serves as the set speed for the speed PID control loop. The feedback speed value comes from the servo motor's speed sensor (such as a rotary transformer). Both are calculated using a PID algorithm to obtain the output value, which serves as the set current for the current PID control loop. The feedback current for the current PID control loop comes from the analog three-phase current acquired through Clarke and Park transformations. These are then used in PID calculations to obtain the duty cycle of the six PWM signals controlling the servo motor. Changes in the PWM signal duty cycle control the on / off state of the drive circuit, thereby changing the magnetic field and controlling the servo motor's operation. Using a PID closed-loop control algorithm, dynamic adjustment of the angle in the steady-state range can be achieved, reducing deviation. This deviation mainly depends on the resolution of the rotary transformer sensor and the stability of the system's acquired data.

[0049] The "speed feedforward" refers to the current PID control loop incorporating a speed feedforward term. The control algorithm for the current PID control loop is as follows:

[0050]

[0051] in:

[0052] k represents the kth output cycle of the current PID control loop at the current moment, and k is a natural number;

[0053] u(k) represents the output value of the kth output cycle of the current PID control loop;

[0054] e(k) is the current difference used to calculate u(k);

[0055] e(k-1) is the current difference used to calculate u(k-1), and e(k-1) is initially 0;

[0056] j = 0, 1, 2, ..., k;

[0057] q represents the q-th output cycle of the PID control loop at the current angle, where q is a natural number;

[0058] possv(q) represents the set angle used to calculate the output value in the qth output cycle of the angle PID control loop. Initially, possv(q-1) is 0.

[0059] K b Denotes the feedforward coefficient, 70≤K b ≤150;

[0060] K p This indicates the current proportional gain of the current PID control loop;

[0061] K i This represents the current integral coefficient of the current PID control loop;

[0062] K d This represents the current differential coefficient of the current PID control loop.

[0063] This algorithm can predict the target position in advance based on the target position at the current moment, thereby shortening the adjustment time. In motor control, this means that the motor responds faster and adjusts to the target angle more quickly at the same speed.

[0064] In the specific scheme, the output cycles of the three control loops can be determined according to the operating parameters and control accuracy requirements of the controlled unit. Specifically, for different servo units, if it is necessary to improve and enhance the control quality, this can be achieved by adjusting the output cycles of each closed-loop control. For example, the current loop control cycle can be increased while the cycles of other closed-loop control remain unchanged. More specifically, the angle control cycle is X, 5ms≤X≤10ms; the speed control cycle is Y, 1ms≤Y≤5ms; and the current control cycle is Z, 0.05ms≤Z≤0.1ms.

[0065] In a further proposed solution, a segmented PID control algorithm is employed. This means that during the servo motor control process, the three control loops each select different PID control parameters (including K) based on corresponding thresholds. p K i and K d Closed-loop control is implemented to further improve motor response speed while ensuring no overshoot. Specifically, this includes:

[0066] For the angle PID control loop, the rotational speed is calculated after selecting the parameters of the angle PID control loop based on the magnitude of the current angle difference and the first threshold. The selection of the angle PID control loop parameters based on the magnitude of the current angle difference and the first threshold includes:

[0067] When the current angle difference is greater than or equal to the first threshold, K p When the value of K is greater than the current angle difference and less than the first threshold, p The value of ;

[0068] When the current angle difference is greater than or equal to the first threshold, K i When the value of K is less than the current angle difference and less than the first threshold, i The value of ,

[0069] Furthermore, the K of the angle PID control loop p The value range of K is [10, 50]. i The value range of K is [0,1]. d The value range is [0, 0.1];

[0070] For the speed PID control loop, the current is calculated after selecting the parameters of the speed PID control loop based on the relationship between the current speed difference and the second threshold. The selection of the speed PID control loop parameters based on the relationship between the current speed difference and the second threshold includes:

[0071] When the current speed difference is greater than or equal to the second threshold, K p When the value of K is greater than the current speed difference and less than the second threshold, p The value of ;

[0072] When the current speed difference is greater than or equal to the second threshold, K i When the value of K is greater than the current speed difference and less than the second threshold, i The value of ,

[0073] Furthermore, the K of the speed PID control loop p The value range of K is [0.5, 10]. i The value range of K is [0,1]. d The value range is [0, 0.1];

[0074] For the current PID control loop, the duty cycle is calculated after selecting the parameters of the current PID control loop based on the relationship between the current current difference and the third threshold. The selection of the parameters of the current PID control loop based on the relationship between the current current difference and the third threshold includes:

[0075] When the current difference is greater than or equal to the third threshold, K p When the value of K is greater than the current current difference and less than the third threshold, p The value of ;

[0076] When the current difference is greater than or equal to the third threshold, K i When the value of K is less than the current current difference and less than the third threshold, i The value of ,

[0077] Furthermore, the K of the current PID control loop p The value range of K is [0,1]. i The value range of K is [0,1]. d The value range is [0, 0.1].

[0078] In the specific scheme, the first threshold, the second threshold, and the third threshold can be selected according to the unit's operating parameters and control accuracy requirements.

[0079] In some solutions, angle, speed, and current are normalized. This method ensures that the PID parameters tuned by the controller are compatible with most servo motors, without requiring re-determining the control parameters due to changes in motor model, thus maximizing parameter applicability. For solutions using normalized data, in the piecewise PID control algorithm, the first threshold is set to 0.3, the second threshold to 0.2, and the third threshold to 0.015.

[0080] Example 1:

[0081] The specific solution of this embodiment is to use the method of the present invention. Figure 6 The flow regulation servo control system of the liquid rocket propulsion system shown is controlled by a servo unit. Figure 6 The liquid rocket propulsion system flow regulation servo control system shown consists of a host computer, cables (communication, power supply, control, and signal acquisition cables), a controller, a power supply, a servo unit, and a flow regulator. The servo unit consists of a servo motor, a reducer, a brake, and a feedback device (sensor).

[0082] Its working principle is as follows: the host computer sends control commands to the controller through the communication cable, and at the same time receives the motor working data and telemetry data uploaded by the controller; the power supply provides power to the controller through the power cable, and the controller provides power to the servo unit through the internal power management module; when the servo unit is not running, the brake is closed, and when it starts, the brake is open; the servo unit reducer and the flow regulator are connected through a mechanical gear structure, and the rotation of the servo motor drives the flow regulator to rotate, thereby realizing the flow regulation of the liquid rocket engine.

[0083] To reduce the complexity of space launch systems, improve the reliability of propulsion systems, and enhance the stability and rapid shutdown characteristics of engine ignition and start-up, flow regulators are used to control the oxidizer flow rate, and throttle valves are used to control the fuel flow rate. By controlling the ratio of the two propellants, the mixture ratio is controlled, thereby controlling the engine thrust. The liquid rocket engine flow regulation system uses a servo motor as the core component for thrust and mixture ratio control. The core of thrust and mixture ratio control is flow regulation; the flow regulators or fuel throttle valves used require the installation of servo motors and the use of angle control to change their opening.

[0084] In this embodiment, the angle PID control loop outputs the speed calculation result every 5ms; the speed PID control loop outputs the current calculation result every 1ms; and the current PID control loop outputs the duty cycle calculation result every 0.1ms as the servo motor control signal.

[0085] In this embodiment, the current PID control loop includes a speed feedforward term, where K... b =100;

[0086] Furthermore, the control method in this embodiment uses normalized data of angle, rotational speed, and current for corresponding control, and employs a piecewise PID control algorithm. The selection scheme for the parameters of the three control loops is as follows:

[0087] The angle PID control loop selects control parameters based on the relationship between the current normalized angle difference and the first threshold of 0.3: if the current normalized angle difference is ≥ 0.3, then K... p =25, K i =0,K d =0, if the current normalized angle difference is <0.3, then K p =15, K i =0.01, K d =0;

[0088] The speed PID control loop selects control parameters based on the relationship between the current normalized speed difference and the second threshold of 0.2: if the current normalized speed difference is ≥ 0.2, K... p =2, K i =0.01, K d =0, if the current normalized speed difference is <0.2, then K p =1.5, K i =0.002, K d =0;

[0089] The current PID control loop selects appropriate control parameters based on the relationship between the current normalized current difference and the third threshold of 0.015. If the current normalized current difference is ≥ 0.015, then K...p =0.4, K i =0.005, K d =0, if the current normalized current difference is <0.015, then K p =0.2, K i =0.01, K d =0.

[0090] Acquire position settings and feedback values ​​during the control process, and plot corresponding curves, such as... Figure 2 As shown, it meets the requirements of rapid response, no overshoot, and steady-state error of less than ±0.2 degrees for rocket propulsion systems.

[0091] Comparative Example 1:

[0092] The difference between this comparative example and Example 1 is that the current PID control loop does not include a speed feedforward term K. b (possv(q)-possv(q-1)), the proportional motor control effect is as follows Figure 3 As shown.

[0093] contrast Figure 2 and 3 It can be seen that without feedforward, the motor control is close to the target position, but due to the lack of overshoot requirements, the feedback deviation from the set point is larger; while with the introduction of feedforward control, the deviation can be basically guaranteed to remain unchanged and without overshoot, and the deviation is smaller than that of the motor control without feedforward.

[0094] Comparative Example 2:

[0095] The difference between this comparative example and Example 1 is that the current PID control loop does not include a speed feedforward term K. b (possv(q)-possv(q-1)), and without using a piecewise PID control algorithm, the control parameters for the three control loops are:

[0096] Angle PID control loop, K p =25, K i =0,K d =0;

[0097] Speed ​​PID control loop, K p =2, K i =0.01, K d =0;

[0098] Current PID control loop, K p =0.4, K i =0.005, K d =0.

[0099] The speed setpoint (i.e., the input to the speed PID control loop) and feedback values ​​during the acquisition and control process are used to plot the corresponding curves, such as... Figure 4 As shown.

[0100] Example 2:

[0101] The difference between this embodiment and embodiment 1 is that the current PID control loop does not include a speed feedforward term K. b (possv(q)-possv(q-1)), its control effect is as follows Figure 5 As shown.

[0102] contrast Figure 4 and 5 The results show that, without segmentation, when the angle step control adjusts from the current angle to the target angle, the speed changes to a very large value instantaneously, and then gradually decreases, resulting in overshoot in the control process; with segmented control, the speed is in a stable process during motor adjustment, and gradually decreases after approaching the target angle, achieving overshoot-free control.

Claims

1. A control method of a control angle motor, characterized by, The method is realized by using an angle PID control loop, a speed PID control loop and a current PID control loop, and comprises the following steps: Real-time collection of the motor reducer angle, subtraction of the current angle of the reducer from the current set angle, and use of the obtained current angle difference as the input of the angle PID control loop, the angle PID control loop calculating the speed by using the angle difference; periodic output of the speed calculation result of the angle PID control loop; Real-time collection of the motor speed, subtraction of the current speed of the motor from the current speed calculation result, and use of the obtained current speed difference as the input of the speed PID control loop, the speed PID control loop calculating the current by using the speed difference; periodic output of the current calculation result of the speed PID control loop; Real-time collection of the motor current, subtraction of the current current of the motor from the current current calculation result, and use of the obtained current current difference as the input of the current PID control loop, the current PID control loop calculating the duty ratio by using the current difference; periodic output of the duty ratio calculation result of the current PID control loop as the servo motor control signal; The control algorithm of the current PID control loop is as follows: ； Wherein: k represents the kth output period of the current PID control loop at the current time, and k is a natural number; u(k) represents the output value of the kth output period of the current PID control loop; e(k) is the current difference used for calculating u(k); e(k-1) is the current difference used for calculating u(k-1), and e(k-1) is initially 0; =0,1,2，…，k； q represents the qth output period of the angle PID control loop at the current time, and q is a natural number; set_angle(q) represents a set angle used in the calculation of the output value of the qth output cycle of the angle PID control loop, and is initialized to 0 at the start, 0; represents the feedforward term coefficient, 70 ≤ ; represents the current proportional coefficient of the current PID control loop; represents the current integral coefficient of the current PID control loop; represents the current derivative coefficient of the current PID control loop; The method further comprises the following steps: Calculation of the speed according to the size relationship between the current angle difference and the first threshold value for selecting the parameters of the angle PID control loop, which comprises the following steps: The value of the angle PID control loop when the current angle difference is greater than or equal to the first threshold The value of the angle PID control loop when the current angle difference is less than the first threshold The value of the angle PID control loop when the current angle difference is less than the first threshold When the current angle difference is greater than or equal to the first threshold, the angle PID control loop When the value is less than the current angle difference and less than the first threshold, the angle PID control loop... The value of , and the value range of the angle PID control loop of is [10, 50], the value range of the angle PID control loop of is [0, 1], and the value range of the angle PID control loop of is [0, 0.1]. Calculation of the current according to the size relationship between the current speed difference and the second threshold value for selecting the parameters of the speed PID control loop, which comprises the following steps: The current speed difference value is greater than or equal to the second threshold value The current speed difference value is less than the second threshold value The current speed difference value is less than the second threshold value The current speed difference value is greater than or equal to the second threshold value The current speed difference value is less than the second threshold value The current speed difference value is less than the second threshold value And, the value range of the speed PID control loop of is [0.5, 10], the value range of the speed PID control loop of is [0, 1], and the value range of the speed PID control loop of is [0, 0.1]. Calculation of the duty ratio according to the size relationship between the current current difference and the third threshold value for selecting the parameters of the current PID control loop, which comprises the following steps: The current PID control loop when the current difference is greater than or equal to a third threshold value The current PID control loop when the current difference is greater than or equal to a third threshold value The current PID control loop when the current difference is greater than or equal to a third threshold value The current PID control loop when the current difference is greater than or equal to a third threshold value The current PID control loop when the current difference is less than the third threshold value The current PID control loop when the current difference is less than the third threshold value and the value range of the current PID control loop is [0, 1], the value range of the current PID control loop is [0, 1], the value range of the current PID control loop is [0, 0.1].

2. The control method of a control angle motor according to claim 1, characterized by, The output period of the angle PID control loop is 5 ms to 10 ms; the output period of the speed PID control loop is 1 ms to 5 ms; and the output period of the current PID control loop is 0.05 ms to 0.1 ms.

3. The control method of a control angle motor according to claim 1, characterized by, The difference between the normalized values of the current angle and the current set angle is taken as the current angle difference; The difference between the normalized values of the current speed calculation result and the current speed of the motor is taken as the current speed difference; The difference between the normalized values of the current current calculation result and the current current of the motor is taken as the current current difference.

4. A control system for a variable angle motor, characterized by The control system of the motor for controlling the angle comprises a data acquisition module, an angle PID control loop, a rotating speed PID control loop, a current PID control loop and a segmented PID control module. The control system of the motor for controlling the angle is used to execute the method of claim 1, 2 or 3.

Images