Study On Motion Planning And Stability Recovery For Legged Jumping Robot

In complex or nonstructure environment, legged jumping robots have a better mobility, dexterity and terrain suitability than wheeled or tracked robots. As an advanced topic in mobile robots, they have well application foreground in fields of house work, rehabilitation treatment, sports science, life entertainment, interstellar exploration and national defence.Legged jumping robot is a multivariable, strongly coupled, nonlinear and varying structure dynamics system. Due to actuator constraints limitation, the ability of jumping over obstacles and dynamic stability are very challenging for control theory and motion planning. This dissertation concentrates on multi-joints legged jumping robot without elastic actuators. In order to improve versatility of jumping motion, some key problems related to dynamics modeling, motion planning, motion optimization and stability recovery are studied. Simulations and experiments have also been performed to test the methods presented in the dissertation. The discussed contents are listed as follows.(1) Character parameters of jumping motionFrom biology forms under literature datum and human jumping motion under motion capture experiment, three character parameters can be used to describe jumping robots related to biomechanics and robotics, and they are take-off postures, generalized load and upper limbs swing.(2) Dynamics modeling of legged jumping robotLegged jumping robot belongs to a variable constraint system because every phase has different constraint conditions. Stance phase has holonomic constraint, nevertheless flight phase has holonomic and non-holonomic constraints. The unified dynamics modelings of legged jumping robot including flight phase, stance phase and landing impact phase are achieved using Lagrange method based on floating basis.(3) Motion planning of jumping over obstaclesUsing the idea of motion synthesis and redundant DOFs decoupling, a motion planning method related jumping over obstacles is presented. Upper body is equivalent to a rigid body with inertia property. Based on internal dynamics and boundary conditions including jumping postures and obstacle's size, a motion of jumping over obstacles is planned. Moreover, redundant DOFs are decoupled using open-manipulability optimization method based on COM manipulability of upper limb.(4) Motion optimization for legged jumping robotLegged jumping robot can be regarded as a redundant manipulator with a load at the end-effector. From the take-off dynamics and transfer performance between motion and force, inertia matching directional manipulability is used to optimize character parameters of jumping motion including take-off posture, generalized load and upper limbs swing. Inertia matching ellipsoid is an index of dynamic performance, and it measures the jumping height under jumping tasks.(5) Stability recovery under landing impactDuring landing impact phase, there is a large impact force. Aim at this landing impact, ZMP manipulability is introduced to plan jumping gaits based on actuator constraints limitation. Stability can be recovered by ZMP plane projection method within actuator performance, and it is only recovered through gait adjustment beyond actuator performance.(6) Experiments of human motion capture and robot jumping motionIn order to verify the proposed methods, human motion capture and experiment platforms for jumping motion are constructed respectively. Main factors are obtained by analyzed motion of key points based on human motion capture system. Motion optimization and stability control strategy are tested under two jumping robots which one is run linked to a 3D platform and the other is an autonomous robot.The main contributions of this dissertation consist in the improvement of mobility and jumping performance, motion planning and stability recovery control of legged robot. The presented methods are worth to be used for widening application fields and its reference value on the theory and application.