Walking Trajectory Generation and Control at Non-constant Body Height for Biped Robot
Date Issued
2012
Date
2012
Author(s)
Chang, Hong-Hao
Abstract
The objective of this research is mainly in generating a biped robot walking pattern towards more closer to mimic human walking. In many research, we found that the ZMP(Zero Moment Point) planning of their walking trajectory has a big difference between that measured from human walking. Therefore, we tried to implement a biped robot walking pattern to with the ZMP planning mimic to human walking.
The mathematical model of the biped robot used in our research is composed of three main points, which is very different from LIPM (Linear Inverted Pendulum Model) and GCIPM(Gravity Compensated Inverted Pendulum Model). This model represents the physical structure of biped robot better than LIPM and GCIPM. We use ZMP based trajectory generator with the three mass model and divide walking behavior into three processes(lowering down, rising up and inverted pendulum mode processes). The walking pattern we developed has the following features: (1) quasi-constant speed body movement. (2) The ZMP planning goes monotonically forward with no intermediate stop. (3) The height of body is quite high and it is at non-constant height during the walking process. Combining the three features above, we can develop a quasi natural walking pattern. In the mean time, we also provided a rule of how to set the parameters of walking trajectory generator and it makes us easier to control the stride length and walking velocity.
In the biped robot walking experiment, we use Windows XP as the operating system with RTX real time kernel. In addition, with common modules such as encoders/decoders and AD/DA converter, we can easily establish a control system that is very friendly to developers. In our experiment, walking patterns with stride length of 5cm to 30cm is implemented. From the snapshots of the experiment, we find that the walking behavior has a big difference from other ZMP based trajectory generating methods and is quite stable. With the same method, we can get a common walking pattern at constant body height that is similar to the walking behavior of HRP and ASIMO. From the ZMP response measured in the experiment, we know that there are big errors from the desired ZMP reference but in the mean time the stability of the proposed walking pattern has been proved.
Subjects
biped
control
Type
thesis
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