Integration of posture and rhythmic motion controls in quadrupedal dynamic walking using phase modulations based on leg loading/unloading

Abstract

In this paper, we intend to show the basis of a general legged locomotion controller with the ability to integrate both posture and rhythmic motion controls and shift continuously from one control method to the other according to the walking speed. The rhythmic motion of each leg in the sagittal plane is generated by a single leg controller which controls the swing-to-stance and stanceto-swing phase transitions using respectively leg loading and unloading information. Since rolling motion induced by inverted pendulum motion during the two-legged stance phases results in the transfer of the load between the contralateral legs, leg loading/unloading involves posture information in the frontal plane. As a result of the phase modulations based on leg loading/unloading, rhythmic motion of each leg is achieved and inter-leg coordination (resulting in a gait) emerges, even without explicit coordination amongst the leg controllers, allowing to realize dynamic walking in the low-to medium-speed range. We show that the proposed method has resistance C. Maufroy ( ) ability against lateral perturbations to some extent, but that an additional ascending coordination mechanism between ipsilateral legs is necessary to withstand perturbations decreasing the rolling motion amplitude. Even without stepping reflex using vestibular information, our control system, relying on phase modulations based on leg loading/unloading and the ascending coordination mechanism between ipsilateral legs, enables low speed dynamic walking on uneven terrain with long cyclic period, which was not realized in our former studies. Details of trajectory generation, movies of simulations and movies of preliminary experiments using a real robot are available at: http://robotics.mech.kit.ac.jp/kotetsu/.

Autonomous Motion Adaptation Against Structure Changes Without Model Identification

“…On typical points, by recovering not only position sensor values but also the sensor values observing the stability such as acceleration, gyro, force and so on, the designed trajectories can be recovered in stable condition. In addition, this problems will be resolved in combination with the other methods such as Maufroy (Maufroy et al, 2010), Otoda (Otoda et al, 2009). Further studies are required.…”

Modular control of limit cycle locomotion over unperceived rough terrain

“…Compared to the CPG approaches in [10], [12], the proposed control architecture is simple and hierarchical as the modules are not strongly interconnected and can be tuned on top of each other. Also we experiment with more difficult rough terrain scenarios and more systematically, however only in simulation so far.…”

“…CPGs have proven to be useful for limit cycle locomotion and has been widely used on different robots [10]- [12], [19], [20]. An open-loop CPG might suffice for flat terrain locomotion, but sensory feedback is needed to compensate for perturbations.…”

“…Another example is the control approach presented by Maufroy al. [12]. They utilize a Central Pattern Generator (CPG) [13] model enriched with phase modulations based on legs loading/unloading.…”

Central Pattern Generators augmented with virtual model control for quadruped rough terrain locomotion

“…Quadruped locomotion over unperceived rough terrain has also been studied in 3D forward dynamics simulation, but not extensively. One example is the work of Maufroy et al [17]. They introduced a CPG control with phase modulations based on legs loading/unloading and tested their control approach one slopes and steps.…”