Zappa, a Quasi-Passive Biped Walking Robot With a Tail: Modeling, Behavior, and Kinematic Estimation Using Accelerometers

In this paper, we describe a biped mechanism model, as well as the biped robot Zappa based on it, that is able to walk using only one actuator that moves its tail. The model has 13 joints and 3 parallel link mechanisms that reduce the passive degrees of freedom to three. We present the behavior of this system when we vary the main parameters that define its gait, and the tail follows a chirp function. It represents an initial methodology for selecting an appropriate set of robot parameters. On the other hand, we present the biped robot Zappa and how we can estimate the kinematics during walking by means of using only three-axis accelerometers. This information allows the attainment of real phase diagrams and, in a future work, the estimation of the zero moment point from the positions and accelerations of the links of the robot.

I. Introduction

Bipeds are complex hybrid dynamical systems in the sense that they mix both continuous and discrete-event phenomena [1]. The main characteristic of biped walkers is the abrupt kinematic change between the aerial and support phases accompanied by dynamical impacts. The main problem is how to achieve a rhythmical or periodical walk. One of the main problems of these robots is their high power and energy consumption, which limits mainly their autonomy. It could be attributed to, for example, the high number of actuated joints (about 20) and also because the study of energy consumption is not often considered during the planning of movements.