Research

The focus of my proposed research is in the field of biped locomotion, which is a key area of study in humanoid robotics. This is a particularly challenging research problem because of the complexity required to maintain balance of a naturally unstable and non-linear dynamic system. Since its inception over 40 years ago, the most popular method of achieving biped locomotion has been through the Zero- Moment Point (ZMP) concept [1]. A direct consequence of this approach is that the joint motors are constantly actuated to maintain balance. Thus far, the majority of walking control strategies [2, 3] aim to keep the ZMP within the region of support to sustain balance during the gait cycle. A direct consequence of this approach is that the joint motors are constantly actuated to maintain balance. Thus, ZMP-based control strategies produce slower walking speeds and are inefficient in terms of energy use (high torque) when compared to human gait even when taking structural and actuator differences into account.

More recent research in the field of biped locomotion has investigated dynamic walking as an alternative approach to achieve more efficient human-like gait [4]. This approach is more in line with natural human gait whereby it utilizes the momentum from the walking motion to eliminate the need for continuous joint actuation. However, the drawback of this approach lies in its poor robustness against perturbations and lack of controllability. The focus of this control strategy would be to restore balance when needed Concurrent research has shown the promising use of a Foot Placement Estimator (FPE) algorithm, which assumes the robot is falling and focuses on identifying where it must step in order to restore balance [5]. A control strategy based on a combination of dynamic walking and the FPE algorithm has the potential to produce more efficient and robust biped locomotion with human-like gait. The focus of this control strategy would be to restore balance when needed, rather than to constantly maintain balance throughout the gait cycle.

References
  1. Vukobratovic M., Borovac B., “Zero-Moment Point - Thirty Five Years of its Life”, International Journal of Humanoid Robotics, 2004.
  2. Kajita, S., Kanehiro, F., Kaneko, K., Fujiwara, K., Harada, K., Yokoi, K., Hirukawa, H., “Biped walking pattern generation by using preview control of zero-moment point”, Robotics and Automation, 2003. Proceedings. ICRA 03. IEEE International Conference, 2003.
  3. Hirai, K., Hirose, M., Haikawa, Y., Takenaka, T., “The development of Honda humanoid robot,” Robotics and Automation, 1998. Proceedings. IEEE International Conference, 1998.
  4. Collins S., Ruina A., Tedrake R., Wisse M. “Efficient Bipedal Robots Based on Passive-Dynamic Walkers”, Science Vol. 307, 2005.
  5. Wight D., Kubica E., Wang D. “Introduction of the Foot Placement Estimator: A Dynamic Measure of Balance for Bipedal Robotics”, Journal of Computational and Nonlinear Dynamics Vol. 3, 2008.