Asymptotic Realization of Desired Control Performance by Body Adaptation of Passive Dynamic Walker

[abstFig src='/00290003/03.jpg' width='300' text='Schematic of the proposed design method' ] This article proposes a design method of legged walking robot hardware capable of performing passive dynamic walking with its desirable characteristics. Passive dynamic walking has a relatively good energy efficiency, and is said to be similar to the walking style of animals. However, most legged robot hardware capable of passive dynamic walking is designed through trial and error on the basis of experience. One of the major problems of designing through trial and error is the difficulty of verifying walking for the legged robot hardware that has many degree of freedom. It is relatively easy to determine the initial condition for compass-type robot hardware. However, it often takes long time to determine the appropriate initial conditions and slope angles for complicated robots such as legged robots with knees. We proposed and verified a method to design a legged robot with knees that has a desired leg length and leg mass from a compass-type legged robot. In this article, we propose a method to design a passive dynamic walker that has a desired leg angle, step length, leg mass, etc., and verify the resulting design. More specifically, the physical parameters, such as the leg length, leg mass, and joint friction, are defined as “physical parameters” and the parameters acquired as the result of walking, such as the leg angle, step length, and walking cycle, are defined as “variable parameters.” By observing variable parameters while the robot is walking and by changing the physical parameters according to the observed variable parameters, the variable parameters are indirectly changed to desired values.