Department of Automation, Ocean University of China, Qingdao 266100, China.
Sensors (Basel). 2020 May 18;20(10):2859. doi: 10.3390/s20102859.
This paper proposes a smooth adjustment method for the instability problem that occurs during the start and stop of a multi-footed robot during attitude change. First, kinematics analysis is used to establish the mapping relationship between the joint angles of the robot support legs and the body posture. The leg joint angle is a known quantity that can be measured accurately and in real time. Therefore, when the position of the foot end of the support leg is unchanged, a unique set of joint angles can be obtained with the change of body posture at a certain moment. Based on the designed mapping model, the smooth adjustment of the posture can be achieved by the smooth adjustment of the support legs. Second, a constraint index that satisfies the requirements of the robot's steady adjustment of the robot is given. The S-curve acceleration/deceleration method is used to plan the body's attitude angle transformation curve, and then the mapping control relationship is used to obtain the control trajectory requirements of the joint to achieve smooth adjustment. In addition, this paper also gives a simple choice and motion control method for the redundancy problem caused by the number of support legs of a multi-footed robot when the attitude is changed. The simulation and prototype experiments verify and analyze the proposed method. The results of comparative experiments show that the posture adjustment method proposed in this paper has continuous acceleration without breakpoints, the speed changes gently during the start and stop phases of the attitude transformation, and there is no sudden change in the entire process, which improves the consistency of the actual values of the attitude planning curve with the target values. The physical prototype experiment shows that the maximum deviation between the actual value of the attitude angular velocity and the target value changes from 62.5% to 5.5%, and the degree of fit increases by 57.0%. Therefore, this study solves the problem of the instability of the fuselage when the robot changes its attitude, and it provides an important reference for the multi-footed robot to improve the terrain adaptability.
本文针对多足机器人在姿态改变过程中启动和停止时出现的不稳定性问题，提出了一种平滑调整方法。首先，通过运动学分析建立机器人支撑腿关节角度与机身姿态之间的映射关系。腿关节角度是一个可以精确且实时测量的已知量，因此在支撑腿的脚端位置不变的情况下，在某一时刻随着机身姿态的变化，可以得到一组唯一的关节角度。基于设计的映射模型，可以通过支撑腿的平滑调整来实现姿态的平滑调整。其次，给出了满足机器人稳定调整要求的约束指标。采用 S 曲线加速度/减速度方法规划机体姿态角变换曲线，然后利用映射控制关系得到关节的控制轨迹要求，实现平滑调整。此外，本文还针对多足机器人在姿态改变时支撑腿数量引起的冗余问题，给出了简单的选择和运动控制方法。仿真和原型实验验证和分析了所提出的方法。对比实验结果表明，本文提出的姿态调整方法具有连续的加速度，没有断点，在姿态变换的启动和停止阶段速度变化平缓，整个过程没有突变，提高了姿态规划曲线的实际值与目标值之间的一致性。物理原型实验表明，姿态角速度实际值与目标值之间的最大偏差从 62.5%降低到 5.5%，拟合度提高了 57.0%。因此，本研究解决了机器人改变姿态时机身不稳定的问题，为多足机器人提高地形适应性提供了重要参考。
