Stable Bipedal Walking With Foot Rotation Through Direct Regulation of the Zero Moment Point

For collaboration of humans and bipedal robots in human environments, this paper proposes a stability control method for dynamically modifiable bipedal walking using a capture point (CP) tracking controller. A reasonable reference CP trajectory for the CP tracking control is generated using the real-time zero moment point (ZMP) manipulation without information on future footstep commands. This trajectory can be modified at any time during the single support phase according to a given footstep command. Accordingly, this makes it possible for the robot to walk stably with dynamically modifiable walking patterns, including sudden changes in navigational commands during the single support phase. A reference CP trajectory during the double support phase is also generated for continuity. The CP of the robot is controlled to track the reference trajectory using a ZMP-based CP tracking controller. The ZMP while walking is measured by the force-sensing resistor sensors mounted on the sole of each foot. A handling method for infeasible footstep commands is utilized so that the manipulated ZMP satisfies the allowable ZMP region for stability. The validity of the proposed method is verified through simulations and experiments.

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A Robust Balance-Control Framework for the Terrain-Blind Bipedal Walking of a Humanoid Robot on Unknown and Uneven Terrain

Sensors ◽

10.3390/s19194194 ◽

2019 ◽

Vol 19 (19) ◽

pp. 4194 ◽

Cited By ~ 6

Author(s):

Hyun-Min Joe ◽

Jun-Ho Oh

Keyword(s):

Humanoid Robot ◽

Balance Control ◽

Humanoid Robots ◽

Bipedal Walking ◽

Leg Length ◽

Zero Moment Point ◽

Uneven Terrain ◽

Control Framework ◽

Zero Moment ◽

Capture Point

Research on a terrain-blind walking control that can walk stably on unknown and uneven terrain is an important research field for humanoid robots to achieve human-level walking abilities, and it is still a field that needs much improvement. This paper describes the design, implementation, and experimental results of a robust balance-control framework for the stable walking of a humanoid robot on unknown and uneven terrain. For robust balance-control against disturbances caused by uneven terrain, we propose a framework that combines a capture-point controller that modifies the control reference, and a balance controller that follows its control references in a cascading structure. The capture-point controller adjusts a zero-moment point reference to stabilize the perturbed capture-point from the disturbance, and the adjusted zero-moment point reference is utilized as a control reference for the balance controller, comprised of zero-moment point, leg length, and foot orientation controllers. By adjusting the zero-moment point reference according to the disturbance, our zero-moment point controller guarantees robust zero-moment point control performance in uneven terrain, unlike previous zero-moment point controllers. In addition, for fast posture stabilization in uneven terrain, we applied a proportional-derivative admittance controller to the leg length and foot orientation controllers to rapidly adapt these parts of the robot to uneven terrain without vibration. Furthermore, to activate position or force control depending on the gait phase of a robot, we applied gain scheduling to the leg length and foot orientation controllers, which simplifies their implementation. The effectiveness of the proposed control framework was verified by stable walking performance on various uneven terrains, such as slopes, stone fields, and lawns.

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EXPERIMENTAL AND THEORETICAL OPTIMAL REGULATOR CONTROL OF BALANCE ZERO MOMENT POINT FOR BIPEDAL ROBOT

Journal of Engineering and Sustainable Development ◽

10.31272/jeasd.24.6.6 ◽

2020 ◽

Vol 24 (06) ◽

pp. 68-82

Author(s):

Ali Fawzi Abdul Kareem ◽

◽

Ahmed Abdul Hussein Ali ◽

Keyword(s):

Performance Index ◽

Settling Time ◽

Bipedal Walking ◽

Optimal Feedback Control ◽

Walking Robot ◽

Zero Moment Point ◽

Double Support ◽

Zero Moment ◽

Minimum Performance ◽

Support Phase

In this paper, the optimal control is analyzed to compare the results of the zero moment point of a bipedal walking robot. Seventeen degrees of freedom bipedal walking robot is manufactured of hard Aluminum sheets. The zero moment point is calculated experimentally and theoretically in the single support phase. MATLAB Simulink is used to simulate the results. The experimental results showed that the lower link takes the settling time is (1) sec, the middle link takes settling time (0.9) sec and the upper link takes (1.1) sec to arrive the desired zero moment point for the bipedal walking robot. The minimum performance index in the experimental parts occurs when the optimal feedback control gain is [35.5 30.4 5 -4]. Hence, the minimum performance index in the theoretical part is [35 31 5.2 -4]. The dimensions of the foot area are (12.3cm×6.3cm), 2.3cm thickness, and 32g weight. Also, the approximate balance area in the double support phase equals the area between the feet of the robot

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