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自由漂浮是空间机器人执行任务时常用的工作模式,其姿态规划是完成复杂空间任务的基础.针对自由漂浮柔性空间机器人姿态运动规划问题,提出一种由Gauss伪谱法求解可行解与直接打靶法求解更为精确的数值解相结合的混合优化策略.首先,利用假设模态法近似描述柔性臂杆的弹性变形,根据Lagrange方程建立空间机器人系统的动力学模型;然后,利用Gauss伪谱法将空间机器人非完整运动规划问题离散为非线性规划问题,求解在较少Legendre-Gauss(LG)点时状态变量和控制变量对应的可行解,可行解的求解采用从可行解到近似最优解的串行优化策略;最后,在LG点处离散控制变量,作为直接打靶法的初值,利用序列二次规划算法求解最优的控制输入,再通过数值积分得到空间机器人系统姿态运动优化轨迹.通过数值仿真,求解得到的姿态运动曲线光滑平稳,最优控制输入也能很好地满足各种约束条件.结果表明该混合优化策略具有很好的鲁棒性和有效性.
Free-floating is a common mode of operation for space robots, and attitude planning is the basis for complex space tasks.In order to solve the problem of attitude and motion planning of free-floating flexible space robots, a method of Gauss Pseudo-spectral method for solving feasible solutions and direct shooting A more accurate solution to the hybrid optimization of numerical solution is proposed.Firstly, the elastic deformation of the flexible arm is approximated by using the hypothetical modal method, and the dynamic model of the space robot system is established according to the Lagrange equation. Then, The problem of nonholonomic motion planning in space robot is discretized as a non-linear programming problem. The feasible solutions of the state variables and the control variables are obtained when the number of Legendre-Gauss (LG) points is small. The feasible solutions are solved from the feasible solution to the approximate optimal solution Finally, the discrete control variables at LG point are used as the initial value of direct shooting method, and the optimal control input is solved by sequence quadratic programming algorithm, and the trajectory of trajectory optimization of space robot system is obtained by numerical integration. Numerical simulation, the solution obtained by the movement curve is smooth and smooth, the optimal control input can be very good Meet a variety of constraints. The results show that the hybrid optimization strategy is robust and effective.