Feed-forward-double closed-loop compound control system and method

Abstract

The invention discloses a feed-forward-double closed-loop compound control system and method, the system innovatively combines feed-forward control and cascade PID feedback control, the feed-forward control acts in advance according to an instruction, and the response speed is greatly improved; the speed ring serves as an inner ring, system damping is effectively increased, and overshoot is restrained; the position ring serves as an outer ring, and final steady-state precision is ensured. According to the method, feed-forward quantity, position PID and speed PID output are calculated in real time through a DSP chip, and the three are superposed to drive a voice coil motor. The method is suitable for high-end equipment fields such as laser communication and precision tracking.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of servo control of precision optical instruments, and particularly to a magnetic circuit design method for improving efficiency of current superimposed motor. BACKGROUND

[0002] Fast steering mirror is a core actuator in the fields of photoelectric tracking and laser communication, and its performance directly affects the tracking accuracy and bandwidth of the system. With the increasing demand for applications, the deflection angle of fast steering mirror has increased from milliradian level to several degrees, which puts high requirements on the dynamic performance of the control system. Although the traditional PID control algorithm is simple in structure and easy to implement, it has obvious shortcomings when dealing with large-angle step commands: first, the inertia and mechanical resonance of the system will cause a large overshoot, which may be as high as 17% or more, prolonging the settling time and even causing system oscillation; second, single feedback control is based on error to generate action, which has inherent response lag, limiting the response speed of the system. For modern fast steering mirror systems that require large travel, high precision and fast response, the traditional control strategy is no longer suitable. Therefore, there is an urgent need for an innovative control method that can effectively overcome the nonlinearity and inertia problems under large-angle motion, and achieve fast, smooth and accurate point control. SUMMARY

[0003] The purpose of the present application is to improve the response speed through feedforward control, suppress overshoot and increase damping through the speed loop, and ensure the final accuracy through the position loop, thereby significantly improving the dynamic performance and steady-state performance of the large-angle fast steering mirror in the full range of motion, and a feedforward-double closed loop composite control system and method are proposed.

[0004] To achieve the above purpose, the present application adopts the following technical solutions: A feedforward-double closed loop composite control system, comprising: a feedforward controller for receiving target commands and outputting feedforward control quantities based on the inverse model of the controlled object; a cascade feedback controller composed of an outer loop position loop and an inner loop speed loop, wherein the outer loop position loop is used to generate a speed command according to the angle error, and the inner loop speed loop is used to generate a feedback control quantity according to the speed error; and a superposition module for adding the feedforward control quantity and the feedback control quantity to generate a final control command and output it to the actuator.

[0005] Further, the feedforward controller comprises: a disturbance transfer function D d (s) for processing disturbance signals d to accurately cancel external disturbances represented by the disturbance signals d; a disturbance channel transfer function G d(s) for describing the dynamic influence path of the interference signal d on the output; a first forward channel transfer function G(s) for processing the control instruction u and multiplying the output signal of the disturbance transfer function D d (s) and multiplying the output signal of the disturbance channel transfer function G d (s) to obtain a feedforward control amount.

[0006] Further, the series feedback controller adopts a series double-closed-loop structure.

[0007] Further, the inner loop speed loop comprises: a speed loop PID for dynamically correcting the input signal; a second forward channel transfer function G(S) for processing the output signal of the speed loop PID and outputting a feedback control amount and generating a feedback signal to be fed back to the speed loop PID.

[0008] Further, the feedback signal of the inner loop speed loop is obtained by differentiating the position sensor signal.

[0009] Further, the outer loop position loop comprises: a position loop PID for processing the input signal to generate a speed instruction; an actuator transfer function G v (s) for converting the speed instruction into an actual speed signal and feeding back a position feedback value to the position loop PID.

[0010] Further, the outer loop position loop and the inner loop speed loop both adopt a PID control algorithm.

[0011] The application also provides a control method of the system according to any one of claims 1-7, comprising the following steps: Step 1: receiving a target angle instruction; Step 2: calculating a feedforward control amount by a feedforward controller according to the target angle instruction; Step 3: collecting an actual angle feedback signal and calculating a speed instruction by an outer loop position loop; Step 4: calculating a speed signal by differentiating the actual angle feedback signal, combining the speed instruction, and calculating a feedback control amount by a speed loop; Step 5: adding the feedforward control amount and the feedback control amount by a superposition module to obtain a final control amount; Step 6: outputting the final control amount to drive the fast reflecting mirror to move.

[0012] Further, the transfer function of the feedforward control algorithm in the feedforward controller is the inverse function of the nominal transfer function of the controlled object.

[0013] Compared with existing technologies, the advantages of this invention are: 1. This invention uses a feedforward controller to output directly according to the command without waiting for the error to occur, which greatly improves the system's response speed to the command. Furthermore, the use of a speed loop as the inner loop greatly improves the system's damping and effectively suppresses overshoot and oscillation.

[0014] 2. The present invention also employs a dual closed-loop structure to make the system more robust to external disturbances and changes in internal parameters. At the same time, by combining a high-resolution sensor and using a position loop as the outer loop, the steady-state accuracy of the system is ultimately guaranteed. Attached Figure Description

[0015] Figure 1 This is a system structure block diagram of the feedforward controller described in this invention.

[0016] Figure 2 This is a block diagram of the feedforward-feedback control system described in this invention.

[0017] Figure 3 This is a block diagram of the control system structure of the speed loop proposed in this invention.

[0018] Figure 4 This is a block diagram of the control system structure of the position loop proposed in this invention. Detailed Implementation

[0019] The invention will now be further explained with reference to the accompanying drawings.

[0020] like Figures 1-4 As shown, the present invention provides a feedforward-dual closed-loop composite control system, comprising: A feedforward controller is used to receive target commands and output feedforward control quantities based on the inverse model of the controlled object.

[0021] The cascade feedback controller adopts a cascaded dual closed-loop structure, consisting of an outer position loop and an inner speed loop. The outer position loop is used to generate speed commands based on the angle error, and the inner speed loop is used to generate feedback control quantities based on the speed error.

[0022] And an overlay module, used to add the feedforward control quantity and the feedback control quantity to generate the final control command and output it to the actuator.

[0023] In this embodiment, the feedforward controller is composed of the disturbance transfer function D. d (s) Disturbance channel transfer function G d The control system consists of the first forward channel transfer function G(s) and the second forward channel transfer function G(s). In the control system, the control command is identified by u, and the core of the feedforward control strategy is reflected in its disturbance transfer function D. d(s), aiming at precisely offsetting the external interference represented by the interference signal d, the behavior of the controlled system is defined by its inherent first forward channel transfer function G(s), in parallel with which is the interference path characteristic, represented by the disturbance channel transfer function G d (s) precisely describes, whose output response is θ(s), namely the feedforward control amount.

[0024] The outer loop position loop is composed of a position loop PID and an actuator transfer function G v (s), when the outer loop position loop receives an input signal, the angle error is processed by the position loop PID to generate a speed command, and the speed command is converted into an actual speed signal by the actuator transfer function G v (s), and the position feedback value is fed back to the position loop PID.

[0025] The inner loop speed loop is composed of a speed loop PID and a second forward channel transfer function G(S), when the speed loop PID receives an input signal, the input signal is first dynamically corrected, then input into the second forward channel transfer function G(S) for processing, and output a feedback control amount and generate a feedback signal feedback to the speed loop PID, wherein the feedback signal of the inner loop speed loop is obtained by differentiating the position sensor signal.

[0026] The above-mentioned outer loop position loop and inner loop speed loop both adopt PID control algorithm.

[0027] A feedforward-double closed loop compound control system is applied to a large-angle fast mirror.

[0028] Therefore, the application also provides a control method based on the feedforward-double closed loop compound control system, comprising the following steps: Step 1: receiving a target angle command.

[0029] Step 2: calculating a feedforward control amount by a feedforward controller according to the target angle command.

[0030] Step 3: collecting an actual angle feedback signal, and calculating a speed command by an outer loop position loop.

[0031] Step 4: calculating an angular velocity signal by differentiating the actual angle feedback signal, combining the speed command, and calculating a feedback control amount by a speed loop.

[0032] Step 5: adding the feedforward control amount and the feedback control amount by a superposition module to obtain a final control amount.

[0033] Step 6: outputting the final control amount to drive the fast mirror to move.

[0034] Wherein, the transfer function of the feedforward control algorithm in the feedforward controller is the inverse function of the nominal transfer function of the controlled object.

[0035] The application improves the response speed through the feedforward controller, suppresses the overshoot, increases the damping through the speed loop, and guarantees the final precision through the position loop, so that the dynamic performance and the steady-state performance of the large-angle fast mirror in the whole range are significantly improved.

[0036] From the common general knowledge, the application can be realized by other embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above disclosed embodiments are only illustrative in all aspects and are not the only ones. All changes within the scope of the application or within the equivalent scope of the application are included in the application.

Claims

1. A feedforward-dual closed-loop composite control system, characterized in that, include: The feedforward controller is used to receive target commands and output feedforward control quantities based on the inverse model of the controlled object; A cascaded feedback controller consists of an outer position loop and an inner speed loop. The outer position loop is used to generate a speed command based on the angle error, and the inner speed loop is used to generate a feedback control quantity based on the speed error. And an overlay module, used to add the feedforward control quantity and the feedback control quantity to generate a final control command and output it to the actuator.

2. The feedforward-dual closed-loop composite control system according to claim 1, characterized in that: The feedforward controller includes: Disturbance transfer function D d (s) is used to process the interference signal d to accurately cancel the external interference characterized by the interference signal d; Disturbance channel transfer function G d (s) is used to describe the dynamic influence path of the interference signal d on the output; The first forward channel transfer function G(s) is used to process the control command u and the disturbance transfer function D. d The signal obtained by multiplying the output signal of (s) and its output signal with the perturbation channel transfer function G d (s) The output signals are multiplied to obtain the feedforward control quantity.

3. The feedforward-dual closed-loop composite control system according to claim 1, characterized in that: The cascade feedback controller adopts a cascaded dual closed-loop structure.

4. The feedforward-dual closed-loop composite control system according to claim 1, characterized in that: The inner velocity loop includes: A speed loop PID controller is used to dynamically correct the input signal. The second forward channel transfer function G(S) is used to process the speed loop PID output signal, and output feedback control quantity and generate feedback signal to the speed loop PID.

5. The feedforward-dual closed-loop composite control system according to claim 4, characterized in that: The feedback signal of the inner velocity loop is obtained by differential calculation of the position sensor signal.

6. The feedforward-dual closed-loop composite control system according to claim 1, characterized in that: The outer ring position ring includes: The position loop PID is used to process the input signal and generate speed commands. and the actuator transfer function G v (s) converts the speed command into an actual speed signal and feeds back the position feedback value to the position loop PID.

7. The feedforward-dual closed-loop composite control system according to claim 1, characterized in that: Both the outer position loop and the inner speed loop employ PID control algorithms.

8. A control method for the system according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Receive target angle command; Step 2: Calculate the feedforward control quantity using the feedforward controller based on the target angle command; Step 3: Acquire the actual angle feedback signal and calculate the speed command through the outer ring position ring; Step 4: Calculate the angular velocity signal differentially based on the actual angle feedback signal, combine it with the speed command, and then calculate the feedback control quantity through the speed loop; Step 5: Add the feedforward control quantity and the feedback control quantity through the superposition module to obtain the final control quantity; Step 6: Output the final control value to drive the fast-reflecting mirror movement.

9. The control method according to claim 8, characterized in that: The transfer function of the feedforward control algorithm in the feedforward controller is the inverse function of the nominal transfer function of the controlled object.

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