Fall on Backpack: Damage Minimization of Humanoid Robots by Falling on Targeted Body Segments

Abstract

Safety and robustness will become critical issues when humanoid robots start sharing human environments in the future. In physically interactive human environments, a catastrophic fall is a major threat to the safety and smooth operation of humanoid robots. It is, therefore, imperative that humanoid robots be equipped with a comprehensive fall management strategy. This paper deals with the problem of reducing the impact damage to a robot associated with a fall. A common approach is to employ damage-resistant design and apply impact-absorbing material to robot limbs, such as the backpack and knee, that are particularly prone to fall related impacts. In this paper, we select the backpack to be the most preferred body segment to experience an impact. We proceed to propose a control strategy that attempts to reorient the robot during the fall such that it impacts the ground with its backpack. We show that the robot can fall on the backpack even when it starts falling sideways. This is achieved by generating and redistributing angular momentum among the robot limbs through dynamic coupling. The planning and control algorithms for a fall are demonstrated in simulation.

Whole-Body Dynamics-Based Aerial Fall Trajectory Optimization and Landing Control for Humanoid Robot

“…As can be seen from Figure 7(1)-(4), in order to reduce the landing speed, the robot swings its arms backward. Figures 7(5)- (8) show that after the robot lands, its knees quickly touch the ground and its arms also start to find the landing position. Figure 7(8) is the final state, and it can be seen that without the constraint of touchdown information, the robot has problems such as flipping over backward and unbalanced ground contact, and the overall optimized motion exhibits unreasonable phenomena.…”

“…However, when the robot lands, the landing controller is engaged. Figure 9(5)- (8) shows the effect of it. Once contact with the ground is detected, the robot swings its arms backward, presses down its body, and moves forward.…”

“…For the aspect of increasing the ground impact time, Kajita et al introduced a method using airbags [7]; however, the airbags employed can only be used once and must reinflate before they can be used again, making the method complex and expensive. Similarly, Sung-Hee Lee introduced a way of placing a backpack on the robot's back [8] to change the falling direction after the robot receives an impact, which is suitable for environments wherein surrounding objects do not interfere. In [9], Kakiuchi designed a robot with hard points mounted over its entire body, which looks like a man wearing a set of shackles and significantly limits the robot's workspace.…”

QP-based adaptive-gains compliance control in humanoid falls

“…The idea is to track a CoM trajectory which aims at minimizing the impact. Another method proposed in [9] consists in making the robot fall on its backpack that prevents the damage.…”

An Integrated Dynamic Fall Protection and Recovery System for Two-Wheeled Humanoids

“…The most basic approach consists in stopping the robot when a possible fall is predicted [13]. Other strategies minimize the damage caused by a fall by locating the contact point on the backpack or on specific areas that are protected [14], mimicking martial arts techniques [15], [16]. Moreover, it is conceivable to use arms to prevent or absorb the effects of falling [17].…”