Zhenze Liu

Further Research and Comparison of Gaits for Compass-Like Biped and Kneed Passive Dynamic Walker

A further research and comparison study of passive gaits for compass-like biped and kneed passive dynamic walker are carried out in the paper. The physical and mathematical model of the two passive robots are illustrated and simulated, and the gait chrematistics are compared. The slope angle scale when stable gaits exist for the two robots is researched. Finally, the slope invariant control and energy based control are designed for kneed robot and validated by simulations. The results of the research can give a deep insight to the effect of knees to the planner passive biped and gives some instructions to design of biped machines.

The analysis on bifurcation and chaos in the compass-gait biped

The paper focuses on the analysis of the behavior of symmetric and asymmetric passive gaits using a simple nonlinear gait biped model and also continues the investigation into the stability property of the compass gait biped. Three parameters, namely the ground slope angle, and the mass ratio and length ratio of the robot are used here to observe the target gait property to improve the robot performance as well as generating new gaits. In response to a continuous change in any one of these three parameters, the symmetric and steady gait of the passive robot will gradually evolve through a regime of stable gait, period-doubling bifurcation, and eventually arriving at an apparently chaotic gait. The note of orbital stability is used to study the stability of passive gaits, and Eigen-values of the linearized poincare map are solved to describe the stability property of biped locomotion. Some symmetry properties of the passive gait biped are discussed, to find the degree of asymmetric between two legs motions. Period-doubling bifurcation of passive gaits and chaotic gaits is studied by poincare maps of passive gaits. The results of the paper are helpful to the investigation of the features and control strategy design of biped locomotion.

Anti-phase Synchronization Control Scheme of Passive Biped Robot

A novel control scheme is proposed for passive compass-like biped based on the concept of anti-phase synchronization. Under this framework, various interesting properties of the stable biped gait are studied. The dynamics of the biped is decoupled by inverse dynamic control and two legs of the biped are converted to be independent parallel subsystems. The coupled synchronization controller is designed which can effectively solve the anti-phase synchronization control problem. The proposed anti-phase synchronization control scheme can also make the mechanical energy of the robot reach a desired level while the average velocity tracking a target value. By designing a Lyapunov function, the stability and convergence of the anti-phase synchronization controller are proved. Simulation is conducted to show the effectiveness of the proposed control scheme. It is demonstrated that the proposed method is useful for analysis and design of the biped gait.

Adaptive compliant control of humanoid biped foot with elastic energy storage

How to minimize landing impact is a challenging research topic in humanoid locomotion. In this paper, we propose a biomimic design of humanoid biped foot with elastic energy storage aiming to reduce the impact when the foot of swing leg landing on the ground and conserve the energy that is used to be dissipated as a result of foot collide. An adaptive compliant control strategy is proposed to control the robot walking smoothly without an exact velocity control of landing foot. The proposed elastic energy storage mechanism and its control approach are used to enhance the dynamic walking capability of biped robot. The effectiveness of the proposed biomimic foot model design is verified by simulation results.

Sub-sectional Control of the Compass-Like Biped Robot

This paper shows the principle and control strategy design of the simple compass-like biped robot. Based upon the control method of energy shaping control and slope invariant control, the sub-sectional controller switches between the inverse dynamic control and passivity based control. The control idea was designed and implemented using numerical simulation. The results showed that the controller can substantially enlarge the basin of attraction and robustness when confronted large disturbances and highly uneven terrains, while keeping a smooth and natural gait.

Further analysis of the kneed passive-dynamic biped robot

The work is a further study on the passive gait biped added with knees, the model can be reduced to a kind of five mass point bar linkage. The further analysis on the variation of the potential energy as well as the kinetical energy has been illustrated, in addition, phase-space limit cycle of a symmetric gait of the robot on a certain degree slope, the conversion law between kinetic energy and potential energy, the energy distribution between the swing leg and stance leg during the walking process have also been presented in detail in the paper, the paper also have a discussion about culmination points which exist in potential and kinetic energy conversion of the coupling two legs. All the research above will have realistic significance in helping us to be better aware of walking rules and global properties of the biped gaits of the robot.

Gait Analysis of the Passive Dynamic Walker with Knees

A systematic study to the passive gaits of the passive dynamic walker with knees is presented in the paper. The motion models are derived firstly and normalized for numerical simulation. A time based limit cycle is employed to represent the hybrid dynamics of periodic passive dynamic walking. The evaluation of gait descriptors under variations of parameters of the robot is studied based on the Poincare first return map which captures the periodic dynamics of passive gaits. The stability property is analyzed and the effect of knees is discussed. The research of the paper is much helpful to the study of passive dynamic walkers with complex structures, the theoretical analysis and control strategy design.

Some results on the study of the kneed gait biped

The new passive gait biped model added with knees can be reduced to a kind of five mass point bar linkage. The variation of the potential energy and the kinetical energy has been discussed. Moreover, the conversion law between kinetic energy and potential energy, the energy distribution between the swing leg and stance leg during the walking process, phase-space limit cycle of a symmetric gait of the robot on a certain degree slope have also been presented in detail in the paper as well as the dipiction about culmination points which exist in potential and kinetic energy conversion of the coupling two legs. All the research above will have realistic significance in helping us to better awaring of walking rules and global properties of the biped gaits of the robot.

Bisection method for evaluation of attraction region of passive dynamic walking

A new numerical method for calculation of the attraction region of limit cycle in passive dynamic walking are proposed in the paper. The cell-mapping method is usually used in the evaluation of attraction region, but the calculation is complex and time-consuming. The existing studies show that the attraction region of passive dynamic walking gait is a continuous region and can be determined by its edge. The new calculation method called the bisection method is presented to determine the basin of attraction approximately simply by searching for its edge. Using the proposed bisection method, the basins of attraction are calculated for passive dynamic walker with and without knees, and the result is compared with the cell mapping method. Compared with the usually used cell mapping method, the bisection method can locate the attraction region with a much higher accuracy and yet need much less of calculation amount.