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… Show more
“…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).…”
Section: Related Workmentioning
confidence: 99%
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
This work introduces a new sensing system for biped robots based on plantar robot skin, which provides not only the resultant forces applied on the ankles but a precise shape of the pressure distribution in the sole together with other extra sensing modalities (temperature, pre-touch and acceleration). The information provided by the plantar robot skin can be used to compute the center of pressure and the ground reaction forces. This information also enables the online construction of the supporting polygon and its preemptive shape before foot landing using the proximity sensors in the robot skin. Two experiments were designed to show the advantages of this new sensing technology for improving balance and walking controllers for biped robots over 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).…”
Section: Related Workmentioning
confidence: 99%
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
This work introduces a new sensing system for biped robots based on plantar robot skin, which provides not only the resultant forces applied on the ankles but a precise shape of the pressure distribution in the sole together with other extra sensing modalities (temperature, pre-touch and acceleration). The information provided by the plantar robot skin can be used to compute the center of pressure and the ground reaction forces. This information also enables the online construction of the supporting polygon and its preemptive shape before foot landing using the proximity sensors in the robot skin. Two experiments were designed to show the advantages of this new sensing technology for improving balance and walking controllers for biped robots over unknown terrain.
“…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.…”
Section: B Step Adjustment and Timing Adaptationmentioning
Step adjustment for biped robots has been shown to improve gait robustness, however the adaptation of step timing is often neglected in control strategies because it gives rise to non-convex problems when optimized over several steps. In this paper, we argue that it is not necessary to optimize walking over several steps to guarantee stability and that it is sufficient to merely select the next step timing and location. From this insight, we propose a novel walking pattern generator with linear constraints that optimally selects step location and timing at every control cycle. The resulting controller is computationally simple, yet guarantees that any viable state will remain viable in the future. We propose a swing foot adaptation strategy and show how the approach can be used with an inverse dynamics controller without any explicit control of the center of mass or the foot center of pressure. This is particularly useful for biped robots with limited control authority on their foot center of pressure, such as robots with point feet and robots with passive ankles. Extensive simulations on a humanoid robot with passive ankles subject to external pushes and foot slippage demonstrate the capabilities of the approach in cases where the foot center of pressure cannot be controlled and emphasize the importance of step timing adaptation to stabilize walking.
“…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.…”
Walking on rough terrains still remains a challenge that needs to be addressed for biped robots because the unevenness on the ground can easily disrupt the walking stability. This paper proposes a novel foot system with passively adjustable stiffness for biped robots which is adaptable to small-sized bumps on the ground. The robotic foot is developed by attaching eight pneumatic variable stiffness units to the sole separately and symmetrically. Each variable stiffness unit mainly consists of a pneumatic bladder and a mechanical reversing valve. When walking on rough ground, the pneumatic bladders in contact with bumps are compressed, and the corresponding reversing valves are triggered to expel out the air, enabling the pneumatic bladders to adapt to the bumps with low stiffness; while the other pneumatic bladders remain rigid and maintain stable contact with the ground, providing support to the biped robot. The performances of the proposed foot system, including the variable stiffness mechanism, the adaptability on the bumps of different heights, and the application on a biped robot prototype are demonstrated by various experiments.
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