Small tracking error correction for electro-optical systems is essential to improve the tracking precision of future mechanical and defense technology. Aerial threats, such as “low, slow, and small (LSS)” moving targets, pose increasing challenges to society. The core goal of this work is to address the issues, such as small tracking error correction and aiming control, of electro-optical detection systems by using mechatronics drive modeling, composite velocity–image stability control, and improved interpolation filter design. A tracking controller delay prediction method for moving targets is proposed based on the Euler transformation model of a two-axis, two-gimbal cantilever beam coaxial configuration. Small tracking error formation is analyzed in detail to reveal the scientific mechanism of composite control between the tracking controller’s feedback and the motor’s velocity–stability loop. An improved segmental interpolation filtering algorithm is established by combining line of sight (LOS) position correction and multivariable typical tracking fault diagnosis. Then, a platform with 2 degrees of freedom is used to test the system. An LSS moving target shooting object with a tracking distance of S = 100 m, target board area of A = 1 m2, and target linear velocity of v = 5 m/s is simulated. Results show that the optimal method’s distribution probability of the tracking error in a circle with a radius of 1 mrad is 66.7%, and that of the traditional method is 41.6%. Compared with the LOS shooting accuracy of the traditional method, the LOS shooting accuracy of the optimized method is improved by 37.6%.
Closed-loop transfer function of the position-loop
Gs (s)
Transfer function
Velocity-loop delay
Current-loop controlled object
GTrack
Image tracker
GT (s)
Electromagnetic torque
Zero-order hold
Gθ (s)
Controller of the position loop
Gω (s), GFF (s), GI (s)
Controllers of the velocity loop
I
Material cross-sectional moment of inertia
I (s)
Current function
ia, ib, ic
Current of each phase winding
id, iq
Current of the d–q axis
if
Current
J
Moment of inertia
K
Free quantity
Ke
Coefficient of counter-electromotive force
Kk
Target manipulator deceleration ratio
Ko, Kδ, Kw
Conversion coefficient
KN
Coefficient of pulse conversion
KV, KI, Kω, Kθ
Coefficients of visual servo
kP, kI, kD
Coefficients of the velocity-loop controller
kp, ki, kd
Coefficients of the current-loop controller
Coefficients of the position-loop controller
L
Stator inductance
L (x)
Interpolation function
Ld, Lq
Inductance of the d–q axis
Ln (x)
Lagrange interpolation polynomial
Lo
Target manipulator rod length
l
Length of the beam
li
Length of the ith structure
Lk (x)
Interpolation basis function
M
Coil mutual inductance of each phase winding
M (x)
The function of bending moment
Ma
Bending moment
M × N
Resolution
{mn, mn+1, ..., mn+4}
Dataset of miss distance
N
Interpolation step size
n
Stepper motor speed
n0
Speed output of the decelerator
OA
Line of sight line
OB
Fire line
Oa, Ob
Reference axis of the calibration tool
P
The stress on the beam
Pn
Number of motor poles
q
Uniformly distributed load
R
Stator resistance
s
Differential module
S
Tracking distance
ds
Differential arc of a cantilever beam
T
Sampling time
T1
Unit step signal duration
T2
Sinusoidal response signal duration
Td, Tf, Tk, Tb
Constant of delay time
Te, TL
Electromagnetic torque and load torque
Ts
Sampling period of the encoder
t
Unit step signal starting time
U (s)
Voltage function
u
Voltage
ua, ub, uc
Voltage of each phase winding
ud, uq
Voltage of the d–q axis
v
Linear velocity
w
Deflection curve
wmax
Maximum deflection
X (t)
Sampling value
x
Displacement
x0, x1, ..., xn
Independent variables
Y
Feedback coordinate
y0, y1, ..., yn
Function values
ya1
Section deflection
yα1, yα2, yα3, yα4
Deflection distance
yβ1, yβ2, yβ3, yβ4
Total deflection distance
z
A variable after the difference transformation
α
Adjustment coefficient
β1, β2
Orthogonal decomposition distances
ψ
Total flux of each phase winding
ψa, ψb, ψc
Flux linkage of each phase winding
ψf
Magnetic linkage of the permanent magnet
ψm
Rotor permanent magnet flux
Flux components of each phase winding
θ
Offset angle
θ*
Output control instruction
θα1(l − x)
Offset angle of section A
θe
Relative angle
θmax
Maximum offset angle
ρ
Curvature radius
δ1, δ3
Calibration deviation
δ2
Vertical distance
δmax
Calibration error
|δ|, δx, δy
Shooting accuracy judgment threshold
|δ|
Tracking error
ε
Stability coefficient of the closed loop
τI
Integral time constant of the velocity loop
τi
Integral time constant of the current loop
ω
Target manipulator angular velocity
ωe
Electrical angular velocity
ωr
Angular velocity
(x, y)
Target pixel coordinate
(Δx, Δy)
Pixel distance
(θM, θN)
Angle of the lens
(θx, θy)
Miss distance
(α, β)
Output pulse of the motor
Center of the lens
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