Quadruped robots have the superiority to locomote on complicated terrains. However, in unknown environments, adaptive locomotion is still a great challenge. Considering the terrains including convex obstacles and forbidden areas, a novel motion planning algorithm is investigated for path planning, gait generation, gait transition and foothold searching. According to the terrain maps built by on-board stereo vision, the quadruped robot chooses the suitable gaits independently. Walk gait is selected on unstructured road segments for more stability while trot gait is employed on flat ground for higher speed. The motion trajectories are performed in the low level compliant control based on the kinematics and the couple dynamics which depends on stance phase and swing phase. The emphases of our inverse dynamics model are the analyses of the couple influences between four legs and the transition between different motion stages. The control architecture is applied on a real quadruped robot, and the experiment results demonstrate the availability of the system.
The quadruped robot excels in tight space traversing and rough terrain locomotion because of its higher flexibility and better environment adaptability. Aiming at passing through tight spaces with free-collision, an adjustment approach of the Center of Gravity (COG) is designed to realize stable quadruped walking. The Hopf oscillator based Central Pattern Generator (CPG), utilized in this paper, can generate rhythmic control signals with different frequencies for the swing phase and the stance phase. The COG is adjusted through the rhythmic medium value transition, which automatically generates smooth trajectories according to preset parameters. We also propose a rhythmic bias compensation method to maintain the rhythmic medium positions of legs vertical to the ground to alleviate the bump caused by the body pitch. Still, an adjustment technique for the hip motion amplitude is developed to maintain the uniform motion when the robot posture changes. We evaluate the performance of the COG adjustment approach on a simulated quadruped robot model, and the simulation of the tight space negotiating of the robot model demonstrates the stable quadruped locomotion.
This article adopts Mikhail Bakhtin's conception of the chronotope to analyze the 2015 film Laopaoer 老炮兒 (Mr. Six), directed by Guan Hu 管虎 and starring Feng Xiaogang 馮小剛, exploring its representation and reconfiguration of the real as well as the imagined time-spaces of Beijing. Revolving around generational conflicts against the grain of a globalized and gentrified Beijing, Mr. Six creates a strong nostalgic appeal and laments the withering of mores from the past. The film not only attends to the physiognomic remapping of contemporary Beijing but also incorporates topographical imaginaries from the culture of the martial arts. By invoking hybrid sites of memory, Guan Hu mobilizes cultural legacies associated with Beijing and creates a palimpsestic urban chronotope. Furthermore, this article compares Mr. Six to its literary and filmic predecessors, probing its insights and oversights in restoring cultural memories and in capturing the zeitgeist of contemporary China. With gaps and conflicts on textual, contextual, and intertextual levels calling into question the efficacy of Mr. Six's exposé of China's social stratification and urban gentrification, the stories in, of, and around Mr. Six reiterate the coordination between cultural elites and consumer culture.
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