Online adaptation for humanoids walking on uncertain surfaces

Abstract

In this paper, an online adaptation algorithm for bipedal walking on uneven surfaces with height uncertainty is proposed. In order to generate walking patterns on flat terrains, the trajectories in the task space are planned to satisfy the dynamic balance and slippage avoidance constraints, and also to guarantee smooth landing of the swing foot. To ensure smooth landing of the swing foot on surfaces with height uncertainty, the preplanned trajectories in the task space should be adapted.The proposed adaptation algorithm consists of two stages. In the first stage, once the swing foot reaches its maximum height, the supervisory control is initiated until the touch is detected. After the detection, the trajectories in the task space are modified to guarantee smooth landing. In the second stage, this modification is preserved during the Double Support Phase (DSP), and released in the next Single Support Phase (SSP). Effectiveness of the proposed online adaptation algorithm is experimentally verified through realization of the walking patterns on the SURENA III humanoid robot, designed and fabricated at CAST. The walking is tested on a surface with various flat obstacles, where the swing foot is prone to either land on the ground soon or late.

Plantar Tactile Feedback for Biped Balance and Locomotion on Unknown Terrain

“…With the addition of contact or pressure sensors on the sole, walking algorithms have been extended to handle unknown terrain conditions 8,19,26 without complex compliant mechanic designs 27 or fast reactive motions. 28 Furthermore, even for point feet robots, the detection of premature contacts on a step trajectory can be used to reset the phase of a Central Pattern Generator (CPG).…”

“…In such conditions, walking controllers must be adapted to the terrain either by mapping the terrain to plan a set of footholds [2][3][4] or by reacting compliantly to the terrain modifying the footholds online. [5][6][7][8][9] Di®erent methods have been developed for mapping the terrain looking for suitable footholds by using cameras, 2 laser scanners 3 or exploratory motions. 4 Following the reactive approach, di®erent methods have been proposed by including Force-Torque (FT) sensors in the ankles or the joints [5][6][7]10,11 or even with contact switches mounted on the sole.…”

“…4 Following the reactive approach, di®erent methods have been proposed by including Force-Torque (FT) sensors in the ankles or the joints [5][6][7]10,11 or even with contact switches mounted on the sole. 8,9 In this paper, a biologically-motivated approach for terrain sensing is presented by mounting robot skin [12][13][14] on the foot soles without modi¯cations on the foot architecture. The plantar robot skin can be used to estimate all the states that are required for balance and locomotion 15,16 (e.g.…”

Walking Control Based on Step Timing Adaptation

“…They used step location and timing adjustment using heuristics to compensate for the DCM (or instantaneous capture point (ICP)) tracking error. Apart from adjusting step timing to robustify gaits against disturbances, [35], [26] adapted the single support duration to negotiate soon or late landing of the swing foot using contact detection.…”

Design and Experimental Development of a Pneumatic Stiffness Adjustable Foot System for Biped Robots Adaptable to Bumps on the Ground

“…In [16], a graph-based footstep planning approach was proposed to generate the whole step sequences in rough terrain scenarios using a black box walking controller. In [17], the preplanned trajectories were modified online to guarantee a smooth landing after the detection of the foot touching the uneven ground. However, the above controllers depended on some sensors, such as inertial measurement units, contact switches, or laser scanners, to obtain the robot motion state and terrain profile information.…”