Study On Non-Regular Motion Planning And Disturbance Rejection Control For Humanoid Robot

Non-regular motions are referring to the ones that involve great degrees of freedom (DOFs), complex constraint conditions, and characteristics of non-periodicity and randomness. As a front research topic in the humanoid robot field, they have well application foreground in fields of rehabilitation treatment, house works, interstellar exploration and sports entertainment.Relative to the periodic biped motion, the challenges for non-regular motions consist in the applicability, especially the applicability for tasks and environments. It's very important for the humanoid robot facing a given task or environment to keep or promote the motion capability. The essential problems are motion planning and motion control. Humanoid robot is a multivariable, strongly coupled, nonlinear and varying structure dynamic system. Its instability due to the varying posture structure and the dynamic stability for a stable movement is very challenging for control theory and dynamics molding.In order to improve the humanoid versatility, this dissertation concentrates on some key problems relate to the non-regular motion, including the dynamic modeling, motion planning and disturbance rejection control. Simulations and experiments have also been performed to test the methods presented in the dissertation. We have mainly done the following research work:1) In this dissertation, some main factors appearing in the modeling process are analyzed according to the characteristics of the non-regular humanoid motion. In addition, the solution for simple nonholonomic constraints appearing in the non-regular motion is presented by using Kane's method. And the nonholonomic partial velocities and the partial angular velocities as well as the nonholonomic generalized active and inertia forces are derived to illustrate the relationships between the nonholonomic and the holonomic systems. Apparently, in addition to the calculation of the controlling torques, an important support for gait and non-gait planning is also provided by the dynamics model of the robot.2) In the term of non-regular motion planning, a state transition method is presented for humanoid robot, that is to generate dynamically stable trajectories according to the key motion states of the given task. In this method, motion planning is simplified by introducing a state-space to describe the whole motion series. And by means of transitions between the neighboring states, i.e. state transitions, all kinds of complex motions can be realized. Since the original motion data are one of the basic elements for the state transition motion planning, this dissertation proposes a new state generation theory to replace the conventional HMCD method. And a state generator is developed based on genetic algorithm (GA), which enables users to generate various motion states without using any reference motion data. By specifying various types of constraints such as configuration constraints and contact constraints, the state generator can generate the desired motion states that are stable as well as satisfy the constraint conditions. Compared with the HMCD method, our approach provides a more direct way to acquire the non-regular motion data. In addition, the state transition process is classified into intra-transition and inter-transition categories. In order to distinguish these two types of transitions, a state recognition method is introduced. We firstly propose a variable contact set in which the contact points on the robot body are defined to represent the alternation of the contact states logically. Then, by predefining thresholds for the contact forces, the state transition can be well recognized.3) As another research topic, the local tracking control according to the pre-acquired state transition trajectories plays an important role in realizing the non-regular motion for the humanoid robot. In this thesis, a control strategy for the trajectory tracking under external disturbance forces is presented. The method combines the inverse dynamics control with the ZMP-plane acceleration projection, whereby the whole body stability of the robot can be considered simultaneously when tracking the predefined trajectories. With this method, the inapplicability existing in the classical control methods in the terms of disturbance rejection and stability maintenance is solved.4) Finally, in order to verify the proposed methods, experiment platforms for the motion planning and disturbance rejection control are constructed respectively. And the motion generation and the execution system are introduced in detail. The platforms provide the premise and basis for verifying the proposed motion planning and disturbance rejection control algorithms by experiments. And it is also one of the key implementation technologies for the non-regular motion system of the humanoid robot.The contribution of the dissertation consists in improving the human-like versatility and motion capability of the humanoid robot, widening application field and its reference value on the theory and application.