Human-Inspired Online Path Planning and Biped Walking Realization in Unknown Environment

Abstract

The focus of research in biped locomotion has moved toward real-life scenario applications, like walking on uneven terrain, passing through doors, climbing stairs and ladders. As a result, we are witnessing significant advances in the locomotion of biped robots, enabling them to move in hazardous environments while simultaneously accomplishing complex manipulation tasks. Yet, considering walking in an unknown environment, the efficiency of humanoid robots is still far from being comparable with the human. Currently, bipeds are very sensitive to external changes and they have severe constraints for adaptation of walk to conditions from such a complex environment. Promising approaches for efficient generation and realization of walking in a complex environment are based on biological solutions that have been developed for many years of evolution. This work presents one such human-inspired methodology for path planning and realization of biped walk appropriate for motion in a complex unfamiliar environment. Path planning results in calculating clothoid curves that represent well the human-like walking path. The robot walk is realized by the composition of parametric motion primitives. Such an approach enables on-line modification of planned path and walk parameters at any moment, instantly. To establish the relationship between high-level path planner and the low-level joint motion realization, we had to find a way to extract the parameters of the clothoid paths that can be linked with the parameters of the walk and consequently to motion primitive parameters. This enabled the robot to adopt its walking for avoiding the obstacles and for a smooth transition between different paths. In this paper we provide a complete framework that integrates the following components: (i) bio-inspired online path planning, (ii) path-dependent automatic calculation of high-level gait parameters (step length, walking speed, direction, and the height of the foot sole), and (iii) automatic calculation of low-level joint movements and corresponding control terms (driving motor voltage) through the adaptation of motion primitives which realize walking pattern and preserves the dynamic balance of the robot.

Approximation of monotone clothoid segments by degree 7 Pythagorean–hodograph curves

“…and substituting these expressions in (30)-(32) yields three equations in three real variables, that are cubic in λ and quadratic in τ 1 , τ 2 . Upon solving these equations, the values of p 1 , q 1 and p 2 , q 2 may be obtained by substituting the solutions λ, τ 1 , τ 2 in (38) and (39).…”

“…When the system of three equations in the variables λ, τ 1 , τ 2 obtained by substituting (38) and (39) into (30)-(32) is employed, starting values for τ 1 , τ 2 must be obtained, to supplement the known starting value for λ. Equations (38) and (39) specify straight lines in the (p 1 , q 1 ) and (p 2 , q 2 ) planes, and the starting values for τ 1 and τ 2 are identified by the points on those lines closest to the values (p 1 , q 1 ) and (p 2 , q 2 ) determined from the quintic PH curve, as identified by minimizing the expressions…”

“…To reduce the dimension of the solution space, we employ the reduced system of three equations in the variables λ, τ 1 , τ 2 obtained by substituting (38)- (39) into (30)- (32). We then record the number of distinct real solutions obtained by Newton-Rapshon iterations from starting values defined by a 21 × 21 × 21 grid over the domain (λ,…”

“…Because of their monotone curvature variation, clothoid segments are of interest in diverse applications, including the design of highways and railways; path planning for mobile robots; specification of bipedal locomotion; control of unmanned aerial vehicles and autonomous ground vehicles; and smoothing of CNC machining toolpaths [4,21,24,28,30,31,37,38,39,41,42,44]. We are interested here in approximating canonical-form clothoid segments using Pythagorean-hodograph (PH) curves [13].…”

State-Space Characterization of Balance Capabilities in Biped Systems with Segmented Feet

“…During balancing tasks, the recovery action from a perturbed posture could benefit from intermittent heel and toe rocking, when compared to the flat-foot model. Nevertheless, very limited studies have investigated this in human experiments (Murnaghan et al, 2009), biped robot design (Vukobratović et al, 2008;Kouchaki et al, 2012;Torricelli et al, 2016), or balance control (Yang et al, 2017). The rigorous quantification of the isolated contribution of a segmented foot model on the balance capabilities of a general biped system has not yet been addressed.…”