Control system for rotational inertia change of space telescope

Abstract

The invention relates to a control system, in particular to a control system for rotational inertia change of a space telescope. The system comprises a first subtracter, a position loop controller, a second subtracter, a speed loop controller, a third subtracter, an extended state observer ESO, a torque controller, a proportional adjustment function device, an error compensator and a filter. In order to further suppress the influence caused by the rotational inertia change, the error compensation mechanism of the error observer is utilized to compensate the error of the extended state observer, and in order to further suppress the influence caused by the noise, a filter is introduced into a compensation item.

Description

Technical Field

[0001] The present invention relates to a control system, and particularly to a control system for the change of the moment of inertia of a space telescope. Background Art

[0002] With the development of technology and the increasingly fierce competition in the space field, space situation awareness plays an increasingly important role in national security and economic development. As an important part of space situation awareness, space telescopes have the advantages of being unaffected by the atmosphere, operating all-weather, and performing surveillance tasks over a wide area.

[0003] Different from large-aperture ground-based telescopes, due to the limitation of launch capacity and the fact that the space environment is not affected by gravity, the space telescope will remove the trim during the launch phase, resulting in a different moment of inertia during on-orbit operation compared to ground debugging. On the other hand, the rotation of the pitch axis of the space telescope will also cause a change in the moment of inertia of the azimuth axis. Such rotational changes will not only affect the control accuracy of the system but may also cause system instability. Therefore, a reasonable control strategy needs to be designed to deal with the adverse effects brought about by the change of the moment of inertia.

[0004] In the prior art, space telescopes usually adopt a double-closed-loop control composed of a double PI controller, which is sensitive to the change of the moment of inertia and has insufficient robustness. At the same time, the estimation error of the ESO is inevitable, affecting the compensation ability for the change of the moment of inertia. The existing compensation methods for the ESO estimation error are either too complex or sensitive to noise, and it is difficult to meet the actual needs. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problems that the existing double-closed-loop control system composed of a double PI controller for space telescopes is sensitive to the change of the moment of inertia and has insufficient robustness, and the compensation for the existing ESO estimation error is too complex or sensitive to noise and difficult to meet the actual needs, and to provide a control system for the change of the moment of inertia of a space telescope.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A control system for the change of the moment of inertia of a space telescope, characterized in that:

[0008] It includes a first subtractor, a position loop controller, a second subtractor, a speed loop controller, a third subtractor, an extended state observer ESO, a torque controller, a proportional adjustment function generator, an error compensator, and a filter;

[0009] Two input ends of the first subtractor are respectively connected to the external desired rotation angle θ * and the actual rotation angle θ output by the proportional adjustment function generator, and the output end outputs the position loop control error eθ To the input terminal of the position loop controller;

[0010] The two input terminals of the second subtractor are respectively connected to the desired rotational speed ω output by the position loop controller * and the actual rotational speed ω output by the controlled object, and the output terminal outputs the speed loop control error e ω To the input terminal of the speed loop controller;

[0011] The two input terminals of the third subtractor are respectively connected to the control speed u output by the speed loop controller ω and the disturbance estimation after filtering by the filter The output terminal outputs the control current i to the input terminal of the torque controller KT and the first input terminal of the extended state observer ESO respectively;

[0012] The torque controller KT is used to output the control torque τ to the control end of the controlled object; the input terminal of the proportional regulator is connected to the actual rotational speed ω output by the controlled object;

[0013] The second input terminal of the extended state observer ESO is connected to the actual rotation angle θ output by the proportional regulator, and the output terminal outputs the observer state To the input terminal of the error compensator;

[0014] The output terminal of the error compensator outputs the compensated disturbance estimation To the input terminal of the filter; the filter is used to filter the compensated disturbance estimation For filtering.

[0015] Furthermore, the state equation of the extended state observer ESO is:

[0016]

[0017] In the formula: e1 is the estimation error of the observer; Is the observer state, n = 1, 2 and 3; β n Is the observer gain, n = 1, 2 and 3; x1 is the rotation angle; k T Is the torque coefficient, and J0 is the nominal value of the moment of inertia.

[0018] Furthermore, the state equation of the torque controller is:

[0019] τ = K T i.

[0020] Furthermore, the position loop controller is a PI controller, and the speed loop controller is a proportional controller.

[0021] Furthermore, the state equation of the position loop controller is:

[0022] ω * = k p e θ + k I ∫e θ dt;

[0023] Where: k P and k I are the position loop proportional control parameter and the position loop integral control parameter, respectively;

[0024] The state equation of the speed loop controller is:

[0025] u ω = k pω e ω ;

[0026] Where: k pω is the speed loop proportional control parameter.

[0027] Furthermore, the state equation of the error compensator is:

[0028]

[0029] Furthermore, the filter is a first-order low-pass filter 1 / b0, and its state equation is:

[0030]

[0031] Where: τ l is the filter parameter, and 0 < τ l < 1; s is the Laplace transform operator.

[0032] The beneficial effects of the present invention are:

[0033] The present invention proposes a dual closed-loop control system for the change of the moment of inertia of a space telescope. The position loop adopts a PI controller to ensure the position tracking accuracy, and the speed loop adopts a proportional control technology to cope with the change of the moment of inertia.

[0034] To further suppress the influence brought by the change of the moment of inertia, the error compensation mechanism of the error observer is used to compensate the error of the extended state observer (ESO). To further suppress the influence brought by the noise, a low-pass filter is introduced into the compensation term. Description of the Drawings

[0035] Figure 1 is a structural schematic diagram of an existing space telescope;

[0036] Figure 2 is a structural diagram of an embodiment of the present invention;

[0037] Figure 3 It is the step response comparison diagram of the change in moment of inertia in the embodiment of the present invention. Specific embodiments

[0038] To make the objectives, advantages, and features of the present invention clearer, the following further elaborates in detail a control system for the change in moment of inertia of a space telescope proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following specific embodiments, the advantages and features of the present invention will be clearer.

[0039] Step 1: The structure of the space telescope is as Figure 1 shown, including an optical load, a pitch-axis motor and its corresponding encoder, a U-shaped frame, an azimuth-axis motor and its corresponding encoder. The mechanical dynamics model of any axis (azimuth axis and pitch axis) is described as:

[0040]

[0041] where J is the moment of inertia, θ is the rotation angle of the telescope motor, and are the first derivative and the second derivative of θ respectively, τ is the output torque of the telescope motor, T L is the disturbance torque, and B is the viscous damping coefficient. Assuming that the current loop bandwidth is large enough, the above model is simplified to:

[0042]

[0043] where K T is the torque coefficient and satisfies τ = K T i, where i is the motor current. Let x1 = θ, The state space model of the above formula is:

[0044]

[0045] where u = i, Let b = b0 + Δb, The above formula can be further written as:

[0046]

[0047] where the lumped disturbance

[0048] Step 2: Let x3 = f, then there is:

[0049]

[0050] where

[0051] Step 3: Design an extended state observer ESO as:

[0052]

[0053] where β n is the observer gain, n = 1, 2, and 3, e1 is the estimation error of the observer, is the observer state, n = 1, 2, and 3;. If there exists a constant L > 0 such that |h| ≤ L, as long as a sufficiently large observer gain is selected, the disturbance estimation error can be guaranteed to be small enough. As long as the disturbance estimation error is small enough, the influence of the change in moment of inertia on the control performance will be small enough. To further reduce the disturbance estimation error, e3 is compensated, that is, a new disturbance estimation is defined as:

[0054]

[0055] where is the estimated value of the lumped disturbance f. In this way, the influence of the change in moment of inertia can be further reduced. However, due to the existence of sensor noise, the compensation term β2e1 will introduce a large amount of sensor noise, and the sensor noise needs to be processed. This patent uses a simple first-order low-pass filter to process the noise, so the above formula can be rewritten as:

[0056]

[0057] where 0 < τ l < 1 is the filter parameter, and s is the Laplace transform operator.

[0058] Step 4: The control block diagram of the entire system is as shown in Figure 2 and includes a first subtractor, a position loop controller, a second subtractor, a speed loop controller, a third subtractor, an Extended State Observer (ESO), a torque controller, a proportional regulation function generator, an error compensator, and a filter; the two input terminals of the first subtractor are respectively connected to the external desired rotation angle θ * and the actual rotation angle θ output by the proportional regulation function generator, and the output terminal outputs the position loop control error e θ to the input terminal of the position loop controller; the two input terminals of the second subtractor are respectively connected to the desired rotation speed ω * output by the position loop controller and the actual rotation speed ω output by the controlled object, and the output terminal outputs the speed loop control error e ω to the input terminal of the speed loop controller; the two input terminals of the third subtractor are respectively connected to the control speed u ω output by the speed loop controller and the disturbance estimation filtered by the filter, and the output terminals respectively output the control current i to the input terminal of the torque controller and the first input terminal of the Extended State Observer (ESO); the torque controller is used to output the control torque to the controlled object (i.e., Figure 2The control end of the turntable mechanical dynamics); the input end of the proportional regulation function device is connected to the actual rotational speed ω output by the controlled object; the second input end of the extended state observer ESO is connected to the actual rotational angle θ output by the proportional regulation function device, and the output end outputs the observer state To the input end of the error compensator; the output end of the error compensator outputs the compensated disturbance estimation To the input end of the filter; the filter is used to filter the compensated disturbance estimation For filtering.

[0059] In the figure, the speed loop controller is a simple proportional (P) controller, and the position loop controller is a PI controller. ω * Is the desired speed calculated by the position controller, θ * Is the desired angle, u ω Is output by the speed loop controller. e ω = ω * - ω is the speed loop control error, e θ = θ * - θ is the position loop control error.

[0060] The speed loop controller is designed as:

[0061] u ω = k pω e ω (9)

[0062] Where k pω Is the speed loop proportional control parameter. The position loop controller is designed as:

[0063] ω * = k p e θ + k I ∫e θ dt (10)

[0064] Where k pω And k I Are the position loop proportional control and position loop integral control parameters respectively.

[0065] The controller parameters are selected as k p = 2.5, k I = 0.5, k pω = 3, β1 = 150, β2 = 7500, β3 = 125000, τ l = 0.02, b0 = 1 / 15.

[0066] The parameters of the controlled object are J0 = 15kg·m 2 、B = 0.056N·m·s / rad, K T = 3.5.

[0067] By increasing and decreasing the moment of inertia to verify the robustness of the controller against changes in the moment of inertia, the simulation experimental results are as Figure 3 shown.

[0068] It can be Figure 3 seen that the proposed control method only has a change in the response speed when the moment of inertia changes, and has no effect on the system stability. Therefore, the proposed control method can effectively suppress the influence of changes in the moment of inertia.

Claims

1. A control system for the change of the moment of inertia of a space telescope, characterized by: It includes a first subtractor, a position loop controller, a second subtractor, a speed loop controller, a third subtractor, an extended state observer ESO, a torque controller KT, a proportional adjustment function, an error compensator and a filter; The two input ends of the first subtractor are respectively connected to the external desired rotation angle θ * The actual rotation angle θ output by the proportional control function, the output position loop control error e θ To the input of the position loop controller; The two input ends of the second subtractor are respectively connected to the desired rotation speed ω output by the position loop controller * and the actual rotation speed ω output by the controlled object, the output speed loop control error e ω To the input of the speed loop controller; The two input ends of the third subtractor are respectively connected to the control speed u output by the speed loop controller ω and the disturbance estimate after filtering The output end outputs the control current i to the input end of the torque controller KT and the first input end of the extended state observer ESO respectively; The torque controller KT is used to output the control torque τ to the control end of the controlled object; the input end of the proportional adjustment function is connected to the actual rotation speed ω output by the controlled object; The second input terminal of the extended state observer ESO is connected to the actual rotation angle θ output by the proportional adjustment function, and the output terminal outputs the observer state To the input of the error compensator; The output terminal of the error compensator outputs the compensated disturbance estimate to the input of the filter, which is used to estimate the compensated disturbance Perform filtering.

2. A control system for the change of the moment of inertia of a space telescope according to claim 1, characterized in that: The state equation of the extended state observer ESO is: Where: e1 is the estimated error of the observer; is the observer state, n = 1, 2 and 3; β n is the observer gain, n = 1, 2 and 3; x1 is the rotation angle; k T is the torque coefficient, and J0 is the nominal moment of inertia.

3. A control system for the change of the moment of inertia of a space telescope according to claim 2, characterized in that: The state equation of the torque controller is: τ=K T I.

4. A control system for the change of the moment of inertia of a space telescope according to claim 2 or 3, characterized in that: The position loop controller is a PI controller, and the speed loop controller is a proportional controller.

5. A control system for the change of the moment of inertia of a space telescope according to claim 4, characterized in that: The state equation of the position loop controller is: ω * =k p e θ +k I ∫e θ dt; Where: k p and k I They are position loop proportional control parameter and position loop integral control parameter respectively; The state equation of the speed loop controller is: you ω =k pω and ω ; Where: k pω It is the speed loop proportional control parameter.

6. A control system for the change of the moment of inertia of a space telescope according to claim 5, characterized in that: The state equation of the error compensator is:

7. A control system for the change of the moment of inertia of a space telescope according to claim 6, characterized in that: The filter is a first-order low-pass filter 1 / b0, and its state equation is: Where: τ l is the filter parameter, and 0<τ l <1; s is the Laplace transform operator.

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