1 Introduction
2 Dynamic Model of the Lander
2.1 Configuration and Coordinate System Definition of Lander
Parameter | Value |
---|---|
Mass of load (kg) | 1650 |
Mass of landing gear (kg) | 15 |
Height of mass center (mm) | 2500 |
Radius of footpad’s lower surface (mm) | 100 |
Distance between two adjacent footpads (mm) | 4000 |
2.2 Adaptive Buffer and Its Control Strategy
Parameter | Value | Range |
---|---|---|
Stiffness coefficient k (N/m) | 4.9 × 104 | [3 × 104, 7 × 104] |
Maximum damping coefficient cmax/(Ns/m) | 5.4 × 104 | [3 × 104, 7 × 104] |
Dynamic range ratio r = cmin/cmax | 0.1 | [0.1, 1.0] |
3 Simulation and Analysis for Adaptive Lander
3.1 Indicators for Soft Landing
Indicator | Parameter | Sign | |
---|---|---|---|
Performance indexes | Nozzle performance against damage | Minimum distance between the bottom of the nozzle and the landing surface (mm) |
U
|
Acceleration overload | Maximum acceleration during soft landing (g) |
L
| |
Buffer performance | Four maximum buffer strokes during soft landing (mm) |
S
| |
Landing stability index | Minimum distance between the centroid of the lander and four stability walls (mm) |
T
|
3.2 Analysis of Landing Performance
Condition | Range |
---|---|
vx (m/s) | [3, 4] |
φ (°) | [0, 45] |
μ
| [0.3, 0.7] |
αe (°) | [0, 10] |
Parameter | Value |
---|---|
vx (m/s) | 3.5 |
φ (°) | 45 |
μ
| 0.7 |
αe (°) | 8 |
4 Hierarchical Optimization
4.1 Sensitivity Analysis of Conditioning Factors
4.2 Response Surface Model
4.3 Optimization in the Followers
Number | Objective | Constraint | Output |
---|---|---|---|
1 | Min U | q
i
L
< qi < q
i
U
|
U
min
|
2 | Max L |
L
max
| |
3 | Max S |
S
max
| |
4 | Min T |
T
min
|
Parameter | Value |
---|---|
Max evaluation | 200 |
Convergence tolerance | 0.1 |
Minimum discrete step | 0.02 |
Parallel batch size | 5 |
Penalty base | 0 |
Penalty multiplier | 1000 |
Penalty exponent | 2 |
Failed run penalty value | 1 × 1030 |
Failed run objective value | 1 × 1030 |
4.4 Optimization in the Leader
Parameter | Value |
---|---|
Population size | 12 |
Number of generation | 20 |
Crossover probability | 0.9 |
Crossover distribution index | 10 |
Mutation distribution index | 20 |
Parameter | cmax (Ns/m) |
r
| K (N/m) |
---|---|---|---|
Value | 34224.47 | 0.30 | 50450.50 |
Landing performance index | U (mm) | L (g) | S (mm) | |
---|---|---|---|---|
Before | Max. | 432.9272 | 15.57734 | 186.1706 |
Avg. | 401.6185 | 9.827149 | 127.2947 | |
Min. | 381.7005 | 5.600144 | 57.4495 | |
After | Max. | 439.0153 | 14.68367 | 146.8838 |
Avg. | 415.9362 | 9.536974 | 94.99342 | |
Min | 401.6876 | 5.484198 | 38.52626 |