We present a software synthesis method for speed- controlled robot walking based on supervisory control of a context-free Motion Grammar. First, we use Human-Inspired control to identify parameters for fixed speed walking and for transitions between fixed speeds, guaranteeing dynamic stability. Next, we build a Motion Grammar representing the discrete- time control for this set of speeds. Then, we synthesize C code from this grammar and generate supervisors 1 online to achieve desired walking speeds, guaranteeing correctness of discrete computation. Finally, we demonstrate this approach on the Aldebaran NAO, showing stable walking transitions with dynamically selected speeds. I. INTRODUCTION Walking provides key advantages for robot locomotion. Walkers are holonomic, they move over rough and uneven terrain, and they adjust their center of mass to better manip- ulate their environment. Producing stable walking on bipedal robots, however, is a challenging control problem. To compose walking with more varied and autonomous robot actions, the robot must safely and reliably transition between different walking behaviors (25, 19). In this work, we focus on one type of behavior: transitioning between different walking velocities to increase flexibility of walking locomotion. Reliable walking depends on both dynamic stability across a variety of modes and correctness of the discrete software implementation. We present a method to achieve both dynamic stability and discrete correctness in the domain of walking speed regulation by implementing Human-Inspired control of bipedal robots using a supervised Motion Grammar, automatically generating stable and correct hybrid control software. The contribution of this paper is a method for automatic synthesis of software for speed-controlled bipedal robot walk- ing and an experimental realization on the NAO robot. Using Human-Inspired control, we generate parameters for walking at fixed and transition speeds (20) (Sect. IV-A), guaranteeing dynamic, continuous stability. Then, we automatically convert this set of steps and transitions to a context-free Motion Grammar (8) (Sect. IV-B), which provides key benefits for control implementation. With a context-free grammar, we can efficiently specify a hierarchical, discrete time controller for step-taking within a single language framework (Fig. 6, Fig. 7). From this single language, we automatically generate the con- trol software for the robot (Sect. V-A) without tedious hand- coding. Then, we apply supervisory control, guaranteeing
['Neil Dantam', 'Ayonga Hereid', 'Aaron D. Ames', 'Mike Stilman']
Correct Software Synthesis for Stable Speed-Controlled Robotic Walking